Abrupt climate change

Abrupt climate change is a specific type of climate change that can occur naturally or possibly as a result of human activities. In abrupt climate change, the climate system changes to a new climate state rapidly, generally over a time scale which is much faster than the typical time scale of the climate forcing responsible for the change. read more on Abrupt climate change

Absolute pressure

Absolute pressure is the measure of pressure with respect to absolute zero pressure, which is the pressure of a perfect vacuum. read more on Absolute pressure

Absolute zero

When all of the molecules (or atoms) in a system stop moving completely, that's as cold as they can get. This temperature, where there's no thermal energy at all, is called absolute zero. read more on Absolute zero

AC adapter

AC adapters convert a higher-voltage alternating current to a lower-voltage direct current for use with devices that require a relatively constant voltage (within a tolerance). read more on AC adapter

AC generation

Turbine-based AC electrical generation uses the unique interactions between charged particles and magnetic fields to convert the kinetic energy of the turbine into the kinetic energy of electrons, which creates a current. read more on AC generation


Acceleration is the rate of change of velocity, meaning that if an objects speed or direction is changing, it is undergoing an acceleration. read more on Acceleration

Acceleration due to gravity

The acceleration due to gravity, usually written as g, is a measure of how fast a free-falling object will accelerate when dropped near the surface of the Earth. It is more or less constant everywhere on Earth. read more on Acceleration due to gravity

Access to electricity

Electricity access refers to the percentage of people in a given area that have relatively simple, stable access to electricity.[1] It can also be referred to as the electrification rate. read more on Access to electricity

Access to non-solid fuel

The lack of access to non-solid fuels for use in lighting, cooking, and heating is a worldwide issue that the World Health Organization estimates contributes to 4 million deaths per year.[2] The use of inefficient and harmful fuels in underdeveloped countries is a significant health, safety, and environmental issue. read more on Access to non-solid fuel


An acid is any substance with a pH less than 7. This means that the ion concentration of hydrogen (H+) is larger than the concentration of hydroxide (OH-). read more on Acid

Acid rain

Acid deposition is any type of precipitation - rain, snow, sleet, hail, or fog - that has a lower pH (and is therefore more acidic) than normal. However, the term almost always used for all of these is acid rain. This higher acidity can cause problems in ecosystems and the environment, and remains one of the major environmental concerns from fuel use despite the immense progress made to address it since the 1970s.[3] read more on Acid rain


The acre is a unit of area used in the Imperial system of units. One square mile is equal to 640 acres. read more on Acre


Adiabatic refers to a process in which no heat is transferred into or out of a system, and the change in internal energy is only done by work. read more on Adiabatic


Aerosols are any small liquid or solid particles suspended in the atmosphere, excluding large cloud or precipitation particles.[4] They are released into the atmosphere by both natural and anthropogenic sources, and interact with various global systems in complex ways. read more on Aerosol


Afforestation is the process of introducing trees and tree seedlings to an area that has previously not been forested. read more on Afforestation

Agricultural energy use

Agricultural energy use is what allows farming to create food. Energy use varies tremendously across agriculture so it's necessary to treat the sector as an aggregation rather than being able to drill in specifically. read more on Agricultural energy use


Air is a mixture of several gases that is a precious resource and a necessity of life. Pure air is completely invisible and odourless, however pollutants in the air can cause it to have a coloured tinge or odour. read more on Air

Air conditioner

An air conditioner is a system that is used to cool down a space by removing heat from the space and moving it to some outside area. The cool air can then be moved throughout a building through ventilation. Air conditioners require some input of work to operatre, otherwise entropy would decrease naturally which is forbidden by the Second law of thermodynamics. Air conditioners act similarly to a heat pump, but instead follow a cooling cycle. read more on Air conditioner

Air infiltration and exfiltration

Air infiltration is the movement of air into a building, whereas air exfiltration is the movement of air out of a building. read more on Air infiltration and exfiltration

Air infiltration/exfiltration

Air infiltration is the movement of air into a building, whereas air exfiltration is the movement of air out of a building. read more on Air infiltration/exfiltration

Air pollution

Air pollution is the presence of any substance at high enough levels in the atmosphere to threaten the health of human, animal and plant life. read more on Air pollution

Air pollution control devices

Air pollution control devices are a series of devices that work to prevent a variety of different pollutants, both gaseous and solid, from entering the atmosphere primarily out of industrial smokestacks. read more on Air pollution control devices

Air pollution from oil sands

There are several different types of air pollution that arise as a result of oil sands bitumen extraction. In addition to the greenhouse gases released by the bitumen extraction process in the oil sands - primarily CO2 (see climate impacts of oil sands for more information) - other pollutants are released during oil sands mining operations. read more on Air pollution from oil sands

Air quality

Air quality is an important factor in a person's quality of life.[5] When air quality is high, the outdoors are fresh and enjoyable. This corresponds to a greater well-being of individuals, including enhanced health and happiness. read more on Air quality

Air quality index

Air quality index (AQI) is a metric developed to communicate levels of pollution over a given location. read more on Air quality index

Aircraft reactor experiment

The Aircraft Reactor Experiment (ARE) was an attempt by Oak Ridge National Laboratories (ORNL) that began in the 1940s to power an aircraft by means a Molten Salt Reactor (MSR) which is a type of nuclear reactor. read more on Aircraft reactor experiment


Albedo is the amount of solar radiation that is reflected by some surface, and is often expressed as a percentage or a decimal value. read more on Albedo


An alcohol is a type of organic compound that is composed of a carbon and hydrogen alkyl chain with one or more hydroxy functional groups attached to a carbon atom of the main hydrocarbon chain. read more on Alcohol


Algae (singular alga) are a diverse group of plant-like aquatic organisms.[6] Oceanic algae is often referred to as phytoplancton. These simple organisms use photosynthesis to grab energy which allows them to make carbohydrates, oils and proteins. These in turn can be processed to become a biofuel read more on Algae

Algae biofuel

Algae are sometimes grown to make algae biofuels since all parts of many types of algae can be used and processed to become a biofuel, unlike other biomass. read more on Algae biofuel


An alkane is a type of hydrocarbon that contain only single bonds. Alkanes are true hydrocarbons, meaning they are made up of nothing but hydrogen and carbon. read more on Alkane


An alkene is one of the four main types of hydrocarbons. Alkenes must contain at least one carbon to carbon double bond in their chain. Alkenes are true hydrocarbons, meaning they are made up of only hydrogen and carbon. read more on Alkene


An alkyne is one of the four main types of hydrocarbons. Alkynes must contain at least one carbon to carbon triple bond in their chain. Alkynes are true hydrocarbons, meaning they are made up of nothing but hydrogen and carbon. read more on Alkyne

Alpha decay

Alpha decay is a nuclear decay process where an unstable nucleus transmutes and ejects a particle composed of two protons and two neutrons.[7] This ejected particle is known as an alpha particle and is simply a helium nucleus. read more on Alpha decay

Alternating current

Alternating current (AC) is the current generated by the vast majority of power plants and used by most power distribution systems, as it is cheaper to generate and has fewer energy losses than direct current when transmitting electricity over long distances. read more on Alternating current

Alternative fuel vehicle

Alternative Fuel Vehicles or AFVs are not powered by conventional diesel or gasoline. These vehicles usually use either natural gas, hydrogen, or electricity. read more on Alternative fuel vehicle

Alternative fuel vehicle infrastructure

Alternative fuel vehicle infrastructure refers to the supporting infrastructure such as fueling stations and specialized support that are needed to run alternatively fueled vehicles. read more on Alternative fuel vehicle infrastructure


Aluminum (Al) also called aluminium is the 13th element on the periodic table, and is the most abundant metal on Earth, making up 8.1% of the Earth's crust. read more on Aluminum


Ammonia is a chemical with the formula NH3. At room temperature, it is a colourless gas, with a pungent odour that is highly irritating. Ammonia is classified as a base, and is fairly corrosive. read more on Ammonia


Ampacity is the maximum amount of current that can be safely carried by a given wire gauge (in the American wire gauge system), it is measured in amperes (A) read more on Ampacity


Amperage is the amount of electric current in amperes. This can refer either to the maximum safe amount of current flowing through a device, or the normal operating current flowing through a device. read more on Amperage


The Ampere is the SI base unit of electric current. read more on Ampere

Ampere hour

An ampere hour (abbreviated A[math]\cdot[/math]h or amp hr) is a unit of electric charge, usually used for batteries. This unit combines the amount of current with how long that current can be sustained until the battery completely discharges. read more on Ampere hour

Antarctic ice

Antarctic ice makes up a large portion of the geography in the great continent of Antarctica. With global warming effects becoming noticeable worldwide, one of the main concerns of scientists is to study the world's large bodies of ice, in order to observe melting ice and rising sea levels. read more on Antarctic ice

Antarctic ice sheet

The Antarctic ice sheet plays an important role in global climate processes. Antarctica's ice sheet is between 1.6 and 6.4 kilometres thick and is the largest block of ice on Earth.[8] read more on Antarctic ice sheet


Anthracite is a dark black fossil fuel and the highest rank of coal. It is very hard, has a low moisture content, and has a carbon content of nearly 95%. read more on Anthracite


Anthropogenic means of, relating to, or resulting from the influence of human beings on nature. read more on Anthropogenic

Anthropogenic carbon emissions

Anthropogenic carbon emissions are the emissions of various forms carbon - the most concerning being carbon dioxide - associated with human activities. These activities include the burning of fossil fuels, deforestation, land use changes, livestock, fertilization, etc., that result in a net increase in emissions.[9] read more on Anthropogenic carbon emissions

Anti-trust legislation

Anti-trust legislation or competition law exists to promote and ensure the freedom and competitiveness of markets, by discouraging any practice or market structure that would reduce competition in the market. read more on Anti-trust legislation


An anticline is a folded rock formation that is upwards convex in shape and was formed from rock that was initially flat. read more on Anticline


Appliances are technologies that run off of electricity or natural gas, used within a residence to accomplish various household needs. read more on Appliance


An aquifer is a porous, water-saturated layer of sand, gravel, or bedrock, which contains groundwater or has flowing groundwater. Simply put, aquifers are large, underground stores of water. They are accessible by a well, and provide the world with around 1/4 of its drinking water. read more on Aquifer

Arctic sea ice

Arctic sea ice is a major concern for climate scientists, as it is one of the most sensitive systems to global warming. With potential impacts of further ice melt from both land and sea ice worldwide, monitoring the sea ice in the Arctic is an ongoing task. read more on Arctic sea ice

Aromatic hydrocarbon

An aromatic hydrocarbon or an arene is one of the four main types of hydrocarbons. Aromatics are true hydrocarbons, meaning these molecules are made up of only hydrogen and carbon. read more on Aromatic hydrocarbon


Arsenic (As) is the 33rd element on the periodic table, and is found naturally in trace amounts on Earth. It is most often found combined with other elements, but is also found in its pure form. read more on Arsenic


Ash is the solid, somewhat powdery substance that is left over after some fuel undergoes combustion. read more on Ash


An asset is a store of value that has the ability to provide benefit in the future to the person, firm or government that owns the asset. read more on Asset

Atlantic Multidecadal Oscillation

Atlantic Multidecadal Oscillation (AMO) is a sequence of long period changes in the sea surface temperature of the North Atlantic Ocean, with cool and warm phases that may last for 60-80 years at a time and a difference in temperature of approximately 0.556°C between extremes.[2] These changes are natural in occurrence and have been happening for at least the last 1,000 years.[2] Since the mid-1990s the world has been in a warm phase.[2] read more on Atlantic Multidecadal Oscillation


An atmosphere is the layer of gases surrounding a planet. read more on Atmosphere

Atmospheric oxygen

Atmospheric oxygen refers to the abundance of molecular oxygen,O2, in the atmosphere; especially in the troposphere that allows life to flourish. read more on Atmospheric oxygen


An atom is the most basic unit of an element - all elements have distinct properties because of the structure of their atoms. For example, an atom on the surface of a silicon crystal (see Figure 1) will be different from those on the surface of a uranium crystal. read more on Atom

Atomic mass

The atomic mass of an element is the microscopic mass of an element in atomic mass units.[10] read more on Atomic mass

Atomic mass unit

The atomic mass unit (u or amu) is one unit for measuring the atomic mass of particles. It is defined as one-twelfth (1/12) of the mass of an unbonded Carbon-12. read more on Atomic mass unit

Atomic number

The atomic number, written as Z, refers to the number of protons in the nucleus of an atom, and is used to organize the periodic table of elements.[11] read more on Atomic number

Atomic weight

Atomic weight, or relative atomic mass, is a unitless number defined as the ratio of the average atomic mass of a given element to the atomic mass unit. read more on Atomic weight

Avogadro's number

Avogadro's number, NA, represents the number of atoms or molecules that are in a mole of a substance. This number is 6.0221415 x 1023.[12] Just like 12 things are in a "dozen", 6.0221415 x 1023 things are in a "mole". read more on Avogadro's number

Avoidance cost

When producing goods and services, firms take certain measures to avoid damaging or harming the environment they operate in. There are many ways in which this can be done, improving pollution control mechanisms, retrofitting inefficient equipment, increased compliance monitoring etc. read more on Avoidance cost

Axial tilt

Axial tilt, also called obliquity, refers to the angle a planet's rotation axis makes with the plane of its orbit. The Earth is currently tilted 23.5° from this plane, resulting in many remarkable effects. read more on Axial tilt

Band gap

A band gap is the distance between the valence band of electrons and the conduction band. Essentially, the band gap represents the minimum energy that is required to excite an electron up to a state in the conduction band where it can participate in conduction. read more on Band gap


The bar is a unit of pressure, equal to 100,000 Pa. read more on Bar


A barrel (bbl) is a unit of volume, almost always used for crude oil and petroleum products. It is equivalent to 42 US gallons or 159 liters. read more on Barrel

Barrels of oil equivalent

Barrels of oil equivalent or BOE is a measure of energy; it's almost always used to discuss primary energy. It compares any amount of energy to how much energy is contained in a single barrel of oil. read more on Barrels of oil equivalent

Base (chemistry)

A base or alkaline is defined as any substance with a pH greater than 7. This means that the ion concentration of hydrogen (H+) is less than the concentration of hydroxide (OH-). read more on Base (chemistry)

Baseload power

Baseload power refers to the minimum amount of electric power needed to be supplied to the electrical grid at any given time. read more on Baseload power


A battery is a device that stores energy and then discharges it by converting chemical energy into electricity. read more on Battery


Billion cubic meters of natural gas (bcm) is a unit of energy, specifically natural gas production and distribution. There are different standards for how much energy this represents, but according the International Energy Agency (IEA) it is equal to 38.2 petajoules (1.06 x 1010 kWh) at 15°C and atmospheric pressure. read more on Bcm


The becquerel or Bq is the SI unit for radioactive decay, measuring the activity of a substance, and is defined as one nucleus decaying per second (units of s-1). read more on Becquerel


Benzene is a hydrocarbon with the chemical formula C6H6. Its bonds are arranged in a closed loop, and it is colourless or light yellow chemical that is liquid at room temperature. It has a sweet odour, is highly flammable, and evaporates easily into the air. read more on Benzene

Bernoulli's equation

Bernoulli's equation expresses conservation of energy for flowing fluids, such as water. It shows the equivalence of the overall energy for a given volume of a fluid as it moves. read more on Bernoulli's equation

Beta decay

Beta decay is a nuclear decay process where an unstable nucleus transmutes and ejects particles to become more stable. There are two different types of beta decay - beta minus and beta plus. read more on Beta decay

Betz limit

The Betz limit is the theoretical maximum efficiency for a wind turbine, conjectured by German physicist Albert Betz in 1919.[13] Betz concluded that this value is 59.3% read more on Betz limit

Beyond design basis accident

Beyond design-basis are accidents that are outside the realm of what the plant was design to withstand are beyond design-basis accidents, the classic example is the Fukushima nuclear accident. read more on Beyond design basis accident

Big Bang

The Big Bang is what scientists call the enormous explosion that started time, space, and the universe.[14] The explosion started out extremely dense and hot, before rapidly cooling down. To this day space remains a few kelvin above absolute zero because of the initial temperature of the Big Bang.[15] Physicists use this model to explain when the fundamental forces appear that govern how everything in the universe interacts. read more on Big Bang


Bioaccumulation describes how the concentration of chemicals in an organism or species increases. This can occur when toxic substances are ingested. read more on Bioaccumulation


Biodiversity is a measure of the variety of organisms within an ecosystem. read more on Biodiversity


When used as an alternative fuel, ethanol is referred to simply as Bioethanol. Bioethanol is frequently used as motor fuel or as an additive in gasoline and is an option for more "renewable" energy. read more on Bioethanol


Biofuel is fuel derived from living matter called biomass (usually plant matter). Examples of biofuels include but are not limited to biodiesel, ethanol, and vegetable oil read more on Biofuel


Biomagnification is the process by which toxic chemicals build up within predators. This typically occurs across an entire food chain and affects all of the organisms but animals higher up in the chain are more impacted. read more on Biomagnification


Biomass is the general term for material whose origin is living, or recently dead organisms. The most common example of biomass as a fuel is wood, which is often burned in its direct form.[2] read more on Biomass


Biomes are nature's major communities, classified according to the predominant vegetation and characterized by adaptations of organisms to that particular environment.[16] Biomes are often defined by abiotic (non-living) factors such as climate, relief, geology, soils and vegetation. read more on Biome


The biosphere is the sum of all regions on the Earth that support life. The biosphere is subdivided into five subcategories known as biomes which include forests, aquatic zones, deserts, tundras, and grasslands. read more on Biosphere


Bitumen is a low-grade of crude oil which is composed of complex, heavy hydrocarbons. In an oil reservoir, bitumen is a thick, viscous fluid and must be extracted from the ground. read more on Bitumen

Bitumen upgrading

Bitumen upgrading is the chemical treatment of bitumen that is used in an attempt to increase its value by creating a high quality crude oil substitute known as a synthetic crude oil. Generally this involves reducing the viscosity of the bitumen to allow for shipment. read more on Bitumen upgrading

Bituminous coal

Bituminous coal is mid-rank type of coal and a black fossil fuel. It is also the most abundant type of coal. The carbon content of bituminous coal is approximately 80%. read more on Bituminous coal

Black swan theory

The Black swan theory, postulated by Nassim Nicholas Taleb, is used to describe the impact of events that come as a surprise in societal aspects. The event is unprecedented at a particular point in time until it happens. read more on Black swan theory

Blackbody radiation

Blackbody radiation, sometimes called cavity radiation, refers to the behavior of a system that absorbs all radiation that is incident upon it and then re-radiates energy. This re-radiated energy is characteristic of the system and doesn't depend on the energy that is hitting it. The radiated energy depends strongly on the temperature of the object instead. read more on Blackbody radiation


An engine block is the heavy solid-cast part of a vehicle's reciprocating engine that houses the cylinders and their components (pistons, spark plugs, etc) and is an important component for the car. read more on Block


Boilers are used in power plants in order to produce high pressured steam, so that the plant can generate electricity. The process that does this is known as the Rankine cycle. The boiler takes in energy from some form of fuel such as coal, natural gas, or nuclear fuel to heat water into steam. read more on Boiler

Boiler slag

Boiler slag is a coarse, granular, incombustible by-product of coal combustion and is thus classified as a coal combustion byproduct. It is angular, dense, and very hard. Boiler slag is only produced in a wet-bottom boiler, as this boiler has a special design that keeps bottom ash in a molten state until it is removed. Essentially, boiler slag is what bottom ash turns into in very specialized boilers. read more on Boiler slag

Boiling point

Boiling point is the temperature that a liquid will change phase into a gas. Boiling occurs when the vapor pressure of a liquid is equal to the atmospheric pressure of the gas outside of it. read more on Boiling point

Boiling water reactor

Boiling water reactors (BWR) are a type of nuclear reactor that use light water (ordinary water, as opposed to heavy water) as their coolant and neutron moderator. They are the second most used reactor for nuclear power generation in the world, next to the pressurized water reactor (PWR), with 80 in operation as of 2015. read more on Boiling water reactor

Boltzmann's constant

Boltzmann's constant (also referred to as the Boltzmann constant), written as kB, is named after the physicist Ludwig Boltzmann. read more on Boltzmann's constant


Boron (B) is the 5th element on the periodic table. It is not found in high abundance in the universe or on Earth, however there is enough of it on Earth to satisfy its certain applications in human society. read more on Boron

Bottom ash

Bottom ash is the coarse, granular, incombustible by-product of coal combustion that is collected from the bottom of furnaces. Most bottom ash is produced at coal-fired power plants. read more on Bottom ash


Braking is the process of controlling the velocity of an object by inhibiting its motion. An object in motion possesses kinetic energy and to bring the object to a stop this kinetic energy must be removed. read more on Braking

Brayton cycle

The Brayton cycle is a thermodynamic cycle used in some heat engines. Notably, it is used for gas turbine engines and some jet engines. read more on Brayton cycle

Breeder reactor

Breeder reactors are a type of nuclear reactor which produce more fissile materials than they consume. They are designed to extend the nuclear fuel supply for the generation of electricity,[17] and have even been mistakenly called a potential renewable energy source. read more on Breeder reactor


BRICs or BRIC countries refers to four countries - Brazil, Russia, India, and China - that are all seen to be at a similar stage of rapidly advancing economic development.[2] The term BRICs was first actively used in a report from Goldman Sachs in 2003, and this report predicted that by 2050 the BRIC economies would be stronger and the countries wealthier than most current economic powers in the West, Europe, and Asia. read more on BRIC

British thermal unit

British thermal units, or BTUs, are a unit of energy. It is the amount of energy required to heat a pound of water by one degree Fahrenheit at one atm. read more on British thermal unit


BTU/hour is aunit of power, measuring energy per unit time, equal to 1 BTU being output in an hour. read more on BTU/hour

Building envelope

The building envelope is the physical barrier between the exterior and interior environments enclosing a structure. read more on Building envelope


Butane is a hydrocarbon that can be burned as a fuel. It's chemical formula is C4H10. read more on Butane

C vs CO2

When discussing climate change, the basic element carbon is often mistaken for carbon dioxide and vise versa.[18] read more on C vs CO2


Cadmium is the 48th element on the periodic table. It is a poisonous metal and within the environment it is classified as a harmful pollutant. read more on Cadmium


A calorie can be used to describe two separate units of measurement, either the thermochemical calorie or the nutritional calorie. Both are equal to a quantity of energy needed to raise the temperature of a certain amount of water by one degree Celsius. read more on Calorie


California University Cyclotron, or the Calutron, is a mass spectrometer which was created during the Manhattan Project by Earnest O. Lawrence for the isotope separation of 235U from 238U. read more on Calutron


A cam is a mechanical link that converts rotational motion into linear motion, or linear motion into rotational motion read more on Cam


A camshaft is a rod which rotates and slides against a piece of machinery in order to turn rotational motion into linear motion. read more on Camshaft

Canadian Energy Security

In Canada there is a relatively high degree of energy security read more on Canadian Energy Security

Canadian support for nuclear power

Public opinion can bring benefits or setbacks to any industry, including the energy industry. Nuclear power is particularly unsupported by Canadians, with over half (53%) of Canadians opposed to it in 2012. read more on Canadian support for nuclear power


The candela (cd) is the SI unit of luminous intensity, which is a measure of power emitted from a light source. read more on Candela

CANDU reactor

CANDU reactor is a type of nuclear reactor which was developed in Canada, and is currently used in nuclear power plants for electrical generation in various countries around the world. CANDU stands for CANada Deuterium Uranium, which reflects the key role of deuterium, or heavy water, which acts as the reactor's neutron moderator, a unique trait of the CANDU. read more on CANDU reactor


Capacitance is the ability of an object or material to store an electric charge. Specifically, it is a measure of an isolated conductor's ability to store charge at a given voltage difference. read more on Capacitance


A capacitor is an electronic device that stores charge and energy. Capacitors can give off energy much faster than batteries can, giving them much higher power density than batteries with the same amount of energy. read more on Capacitor


Capital is anything that has value. Capital must be generated and is then used to create wealth through investment. Capital can come in many forms such as physical capital and human capital. read more on Capital


Carbohydrates are molecules made of carbon, oxygen, and hydrogen. read more on Carbohydrate


Carbon (C) is the 6th element on the periodic table, and also happens to be the 6th most abundant element in the universe. read more on Carbon

Carbon capture and storage

Carbon capture and storage, sometimes referred to as CCS, is a process that can take up to 90% of the carbon dioxide emissions produced from the use of fossil fuels in electricity generation and put them underground or under the ocean. read more on Carbon capture and storage

Carbon cycle

The carbon cycle is the flow of carbon (in various forms, such as carbon dioxide or methane) through the atmosphere, ocean, terrestrial biosphere, and lithosphere.[9] The carbon cycle monitors the exchange of carbon throughout Earth's "carbon reservoirs" which store and transport carbon in many ways.[19] The flow of it is measured in GtC/year (gigatonnes of carbon per year), and it may be stored in gaseous, liquid and solid form in the atmosphere, land and sea.[19] read more on Carbon cycle

Carbon dioxide

Carbon dioxide (CO2) is a naturally occurring gas, important to the carbon cycle for life and a byproduct of many forms of energy production. It is also a greenhouse gas. read more on Carbon dioxide

Carbon farming

Carbon Farming is the use of farming techniques to return once released carbon in the form of carbon dioxide CO2 back to the Earth. read more on Carbon farming

Carbon flux

A carbon flux is the amount of carbon exchanged between Earth's carbon pools - the oceans, atmosphere, land, and living things - and is typically measured in units of gigatonnes of carbon per year (GtC/yr).[19] A gigatonne is a tremendous amount of mass, roughly twice the mass of all humans on Earth combined, or the mass of about 200 million elephants! read more on Carbon flux

Carbon intensity

The term carbon intensity is ambiguous and may refer to:

read more on Carbon intensity

Carbon monoxide

Carbon monoxide, or CO, is a gas that forms from the incomplete combustion of fuels such as propane, natural gas, gasoline, oil, coal, or wood. It is a colourless, odourless, and tasteless gas and thus it cannot be detected without a specialized piece of equipment. read more on Carbon monoxide

Carbon pool

Carbon pools are reservoirs of carbon that have the capacity to both take in and release carbon.[20] read more on Carbon pool

Carbon sink

A carbon sink is a land or ocean mass that can take in carbon - most notably carbon dioxide - from the atmosphere. It is the opposite of a carbon source, which acts to emit carbon into the atmosphere, such as a motor vehicle or a coal-fired power plant. Carbon sources cause negative impacts to the earth as they emit carbon from below the Earth's surface that would otherwise not enter the atmosphere.

Carbon sinks are a vital part of the carbon cycle, as they regulate the carbon in the atmosphere via processes like photosynthesis or absorption through pressure differences.[19] read more on Carbon sink

Carbon tax

A carbon tax is a tax levied on the carbon content in fossil fuels. Even though the tax is designed to address the problem caused by the CO2 emissions, the tax is based on the carbon content because almost all of the carbon is converted into CO2 from the combustion process. read more on Carbon tax

Carbon tax vs emissions trading

Emissions trading or cap-and-trade (CAT) and a carbon tax are fundamentally different tools to limit the effects of using fossil fuels. Carbon taxes makes emitting carbon dioxide more expensive. No matter how much gets emitted a carbon tax makes the emission the same. Cap-and-Trade systems limit the amount of carbon dioxide that gets emitted, but gives little control to the price. read more on Carbon tax vs emissions trading

Carnot efficiency

Carnot efficiency describes the maximum thermal efficiency that a heat engine can achieve as permitted by the Second Law of Thermodynamics. The law was derived by Sadi Carnot in 1824. read more on Carnot efficiency


When firms agree to collude, that is they agree to a certain price and quantity for a good or service, they create a cartel. A cartel is a type of oligopoly. read more on Cartel

Cascade process

A Cascade process is used when purifying or enriching a desired substance and when one stage of enrichment is not enough to reach the target percentages. read more on Cascade process


Celsius is the standard unit of temperature in the metric system of units. Celsius is split up into degrees, with one degree being 1/100 of the temperature difference between the boiling and freezing points of water. read more on Celsius

Centrally planned

A centrally planned economy is one where the price and allocation of resources, goods and services is determined by the government rather than autonomous agents as it is in a free market economy. read more on Centrally planned

Centrally planned economy

A centrally planned economy or a command economy is one where the price and allocation of resources, goods and services is determined by the government rather than autonomous agents as it is in a free market economy. read more on Centrally planned economy


A centrifuge works by spinning objects around a centre axis. read more on Centrifuge

Cetane number

Cetane rating, also known as cetane number is a measurement of the quality or performance of diesel fuel. The higher the number, the better the fuel burns within the engine of a vehicle. The cetane number is similar to the octane rating in that it is a rating assigned to a fuel to rate the quality of its combustion. The difference is that octane rating rates gasoline whereas cetane rates diesel. read more on Cetane number

CFL light bulb

Compact fluorescent light bulbs (CFLs) are a type of light bulb used for lighting needs in a wide range of applications. They are much more energy efficient than incandescent light bulbs which are currently still in wide use. read more on CFL light bulb


Charcoal is a solid fuel used for heating and cooking that is created through the process of carbonisation, which is a process where complex carbon substances - such as wood or other biomass - are broken down through a slow heating process into carbon and other chemical compounds. read more on Charcoal


Charge, which is short for electrical charge, is a fundamental physical property that causes objects to feel an attractive or repulsive force toward one another. read more on Charge

Charge carrier

Charge carriers are particles or holes that freely move within a material and carry an electric charge. read more on Charge carrier


A chemical is some type of matter that has a constant composition (in terms of molecules or atoms). It also has physical properties such as a density, refractive index, conductivity, melting point, and boiling point that can be used to characterize this substance. read more on Chemical

Chemical bond

Chemical bonds are the attractions between atoms that hold them together to form compounds. There are three major types of bonding: covalent bonds that bind together molecular compounds, ionic bonds that bind salts and ionic crystals, and metallic bonds that bind the atoms of metals. read more on Chemical bond

Chemical chain reaction

A chemical chain reaction is a series of chemical reactions where the products of the reaction contribute to the reactants of another reaction. This transformation of products to reactants allows a reaction to continue along by itself with minimal or no outside influence. read more on Chemical chain reaction

Chemical energy

Chemical energy is the potential energy stored in the arrangement of atoms within molecules. Breaking chemical bonds requires energy, while forming new chemical bonds releases energy. The more energy that's released when a bond forms, the more stable that bond is. read more on Chemical energy

Chemical isomer

Chemical isomers are molecules of the same chemical composition, but different molecular structure. In other words, two isomers will have the same number and type of atoms, but a different arrangement in space. read more on Chemical isomer

Chemical reaction

A chemical reaction is a recombination of atoms that produces products with new chemical identities. Chemical reactions power life, and provide most of the energy used by today's high energy society. read more on Chemical reaction

Chernobyl nuclear accident

The Chernobyl nuclear accident refers to the events in the Chernobyl nuclear power plant on April 26th 1986. read more on Chernobyl nuclear accident


Chimneys are ventilation channels that guide smoke and other gases that are products of combustion out from a fireplace through the roof of a building. read more on Chimney


An electric circuit is a connection of components that can conduct current. Simple electrical circuits have conductors (usually wires), a component that supplies power (like a battery or wall plug) and a component that absorbs power called the load. A light bulb would be an example of a load and there must always be a return path - a way for the electrons to come back to the power source from the load. read more on Circuit

Circuit breaker

Circuit breakers are devices that protect circuits from overload current conditions. They do the same job as fuses, but they are not destroyed when activated. read more on Circuit breaker


Climate is broadly defined as the long-term statistics or characteristics of weather that are determined over time. These can be any characteristics, ranging from the average expected weather patterns to the measure of the variability and likelihood of extreme events. read more on Climate

Climate change

Greenhouse gases that come from the combustion of fossil fuels are changing the Earth's climate.<onlyinclude> The world is warming, and there are many different phenomena that force the Earth's climate to become hotter or colder. While some of these are anthropogenic and some are natural, carbon dioxide released from pursuing energy services is by far the most important contributor. read more on Climate change

Climate change consequences on rainforests

Climate change has and continues to have a massive impact on Earth’s rainforests. Whether it’s North America’s western temperate rain forests or the tropical rainforests in South America and beyond, climate change affects these areas negatively. read more on Climate change consequences on rainforests

Climate feedback

Climate feedback is a response to a climate process that either intensifies or minimizes the initial effect of a climate forcing (often either warming or cooling). Essentially, these climate feedback effects occur after an initial forcing (warming or cooling) causes a change, and this change in turn influences the severity of the initial change. read more on Climate feedback

Climate forcing

Climate forcing is the physical process of affecting the climate on the Earth through a number of forcing factors. These factors are specifically known as forcings because they drive the climate to change, and it is important to note that these forcings exist outside of the existing climate system. read more on Climate forcing

Climate impacts of oil sands

The climate impacts of oil sands are significant, and the greenhouse gas emissions for oil sands extraction and processing are significantly larger than for conventional crude oil.[21] read more on Climate impacts of oil sands

Climate scenario

Climate scenarios are plausible representations of the future climate of the Earth, based on its current observed state and different greenhouse gas emission scenarios. read more on Climate scenario

Climate simulation ensemble

An ensemble is a group of climate model simulations used for climate projections. Rather than running a single climate model, an ensemble of thousands of model versions is run with each version of the model being slightly different from one another. This produces a result with multiple scenarios. read more on Climate simulation ensemble

Climate system

The climate system is the highly complex global system consisting of 5 major components: the atmosphere, the oceans, the cryosphere (snow and ice), the land surface, the biosphere, and the interactions between them. read more on Climate system

Climate threshold

A climate threshold is a critical limit where a climate system responds drastically when exposed to an external forcing, resulting in the system changing into a different stable state. read more on Climate threshold

Climate vs weather

It is important to understand that climate and weather are not the same thing. Although both refer to meteorological events, it is the timescale of these events that separates the two. While climate generally looks at these events over a long period of time, weather is short-termed and can change rapidly and drastically. read more on Climate vs weather


Clouds are made primarily of water droplets and ice crystals floating in the sky. They play an important part in the Earth's weather, and influence, and are affected by, the Earth's climate read more on Cloud

Club good

A club good or natural monopoly good is a good that is virtually unlimited in terms of the quantity available but those who do not belong the club that provides the good can be excluded from using the good. read more on Club good

CO2 equivalent

The carbon dioxide equivalent or CO2e is a unit that represents the warming effect of any given greenhouse gas. read more on CO2 equivalent

CO2 footprint

A CO2 footprint or carbon footprint is the total amount of carbon dioxide emissions produced created as a result of an individuals actions over a set period of time - generally over the time period of a year. Whenever an individual drives a car, heats their home, or buys food and other goods a certain amount of carbon dioxide is produced as a result of the manufacturing, fuel extraction, or transportation. read more on CO2 footprint


Coal is a rock formed from the decomposition of plant life. It is primarily composed of carbon, with many other trace elements. read more on Coal

Coal ash

Coal ash, sometimes called coal combustion residuals, is produced from the burning of coal in coal-fired power plants. read more on Coal ash

Coal bed methane

Coal bed methane is methane trapped in underground coal seams. This type of methane can be accessed using drilling techniques similar to those used in the collection of shale gas. read more on Coal bed methane

Coal fired power plant

Coal fired power plants are a type of power plant that make use of the combustion of coal in order to generate electricity. Their use provides around 40% of the world's electricity and they are primarily used in developing countries. read more on Coal fired power plant

Coal formation

Coal is a solid, black, readily combustible fossil fuel that contains a large amount of carbon-based material - approximately 50% of its weight.[22][8] The formation of coal takes a significant amount of time, with coal beginning to form 290-360 million years ago, in a time known as the Carboniferous or "coal-bearing" Period. read more on Coal formation

Coal liquefaction

Coal liquefaction is a process in which coal is converted into liquid fuels or petrochemicals. read more on Coal liquefaction

Coal reserve

Coal reserves refer to large deposits of coal which, based on geological surveys and engineering studies, are thought to exist to a very high degree of certainty. In addition to the knowledge of their existence, these reserves are also accessible and coal can be produced from them economically. read more on Coal reserve

Coal seam

A coal seam is a dark brown or black banded deposit of coal that is visible within layers of rock. These seams are located underground and can be mined using either deep mining or strip mining techniques depending on their proximity to the surface. read more on Coal seam

Coase theorem

The Coase theorem is a way to deal with the tragedy of the commons problem surrounding common resources such as the environment. Ronald Coase is an economist who won a Nobel Prize for Economics and developed his theory in 1960.[23] The coast theorem is a market-based solution to the negative externality created by pollution. <onlyinclude>The theory suggests that property rights are not essential and that government intervention is not necessary but rather, if parties can negotiate (without incurring excess cost) to correct a negative externality then the problem can be solved. read more on Coase theorem

Coefficient of performance

Coefficient of performance (K) is a number that describes the effectiveness of refrigerators or air conditioners, by comparing the heat that is dispelled from it to the work that had to be done to do so. read more on Coefficient of performance


Cogeneration or combined heat and power (CHP) is the on-site generation of electricity and useful heat. When generating electricity from coal, natural gas or nuclear power only a fraction of the actual energy content released during combustion is converted into electricity. The remainder of the energy is lost as waste heat. In a CHP power plant, this waste heat is recovered for other applications such as space heating or other industrial processes that require heat. read more on Cogeneration


Collateral is a asset or group of assets that can be seized by a lender in the event of a loan default. read more on Collateral


Collusion occurs when two or more firms informally agree not to compete with each other or to limit the introduction of new competitors into the market. read more on Collusion

Combined cycle gas plant

Combined cycle gas plants are a type of natural gas power plant used to generate electricity, consisting of a simple cycle gas plant in combination with a second steam engine that uses the Rankine cycle. read more on Combined cycle gas plant

Commercial energy use

Commercial energy use, which includes institutional energy use, is what gives businesses, schools (including universities), and public buildings like libraries the ability to serve the public. read more on Commercial energy use


A commodity is a tangible good that is interchangeable regardless of the producer. Commodities are almost always an input for the production of other goods. read more on Commodity

Common resource

A common resource is a resource that is available to everyone and provides benefit to the users but decreases in value as more and more people use it. read more on Common resource

Comparing gasoline, diesel, natural gas, and electricity prices

Gasoline, diesel, and electricity are all energy currencies which can be used to power transportation. Compressed natural gas can also be considered a currency as it also provides this energy service directly. read more on Comparing gasoline, diesel, natural gas, and electricity prices

Compressed air energy storage

Compressed air energy storage or simply CAES is one of the many ways that energy can be stored during times of high production for use at a time when there is high electricity demand. read more on Compressed air energy storage

Compressed natural gas

Compressed natural gas or CNG is simply natural gas - with the main component being methane - that is stored under high pressures (while remaining in its gaseous form) mainly as a means to transport it or as storage for later use as a vehicle fuel. read more on Compressed natural gas

Concentration in parts per

Pollutants can be problematic even in low concentrations, so it's necessary to be able to talk about very small amounts of a substance in a larger substance. This means it's useful to think of a total and how many parts of that total are a pollutant, or whatever scarce substance is being considered. If we divide a gas into a million parts, then the ppm is how many of those parts is the substance that we're interested in. read more on Concentration in parts per


Conduction can refer to either:

read more on Conduction

Conduction band

The conduction band is the band of electron orbitals that electrons can jump up into from the valence band when excited. When the electrons are in these orbitals, they have enough energy to move freely in the material. This movement of electrons creates a current. read more on Conduction band


Conductors are a category of materials that allow electrons to flow easily (which is called electricity and are a useful way to transport energy). read more on Conductor

Conductor resistance

Conductor resistance is a property of a conductor at a specific temperature, and it is defined as the amount of opposition to the flow of electrical current through a conducting medium. read more on Conductor resistance

Connecting homes to the electrical grid

Connecting homes to the electrical grid is the final stage of the electrical grid. After the distribution grid's substations have stepped-down the voltage to safe levels, this stage may be accomplished. read more on Connecting homes to the electrical grid

Consensus about global warming

There is a significant scientific consensus about global warming; specifically that humans are causing the widespread warming on the Earth. It was found that at least 97% of expert climate scientists agree with this claim,[25] thus forming a dominant scientific consensus within the community. read more on Consensus about global warming

Conservative force

A conservative force is a force that conserves mechanical energy. This means that all of the macroscopic motion (or mechanical energy) stays as macroscopic motion and doesn't turn into microscopic motion (thermal energy). read more on Conservative force

Control (building envelope)

The control function of a building envelope is the most vital contributing factor to the performance of the envelope itself. Enclosures must control the movement of moisture (both liquid water and water vapor), air leakage, and heat transfer. read more on Control (building envelope)

Control function

The control function refers to one of the three functions a building envelope serves, and it is vital to the overall performance of the envelope. The control function refers to the ability of a building envelope to control and moderate the exchange of mass (air and moisture) and energy (heat and sound) due to the separation of interior and exterior environments. read more on Control function

Control rod

A control rod is a device that is used to absorb neutrons so that the nuclear chain reaction taking place within the reactor core can be slowed down or stopped completely by inserting the rods further, or accelerated by removing them slightly. read more on Control rod


Convection is the motion of a fluid driven by temperature differences across that fluid. When a fluid is heated, the region in closest contact with the heat source becomes less dense due to increased kinetic energy in the particles read more on Convection

Conventional vs unconventional resource

Conventional resources and unconventional resources are two very different, separate sets of resources that can potentially be extracted. Both refer to some quantity of fossil fuels that could contribute to a reserve if they could be extracted economically. read more on Conventional vs unconventional resource

Convertible loan

A convertible loan, also called a convertible bond, is a bond that can be converted into common stock shares in the firm that issues the bond. read more on Convertible loan


Copper (Cu) is the 29th element on the periodic table, and is found fairly commonly on Earth, with approximately the same abundance as zinc and nickel. read more on Copper


A cost is the value of resources that are used to achieve an end. read more on Cost

Cost benefit analysis

When a firm considers a new project, they will conduct a cost-benefit analysis to determine if the project is worth pursuing. This is a careful weighing of all of the downsides (costs) and upsides (benefits) of completing the project. If the benefits of the new project outweighs the cost of building or implementing it, than the firm will go ahead with the project. read more on Cost benefit analysis

Cost-effectiveness analysis

A cost-effectiveness analysis (CEA) is a version of a cost benefit analysis where the analysis is focused towards a specific goal and tries maximize the benefit to cost ratio to find the least costly way to meet an objective. read more on Cost-effectiveness analysis

Costs for a firm

Firms have a number of different types of costs including fixed cost, variable cost, total cost and marginal cost. All of these different costs need to be considered when looking to figure out the costs to a firm. read more on Costs for a firm


The coulomb, also written as its abbreviation 'C', is the SI unit for electric charge. One coulomb is equal to the amount of charge from a current of one ampere flowing for one second read more on Coulomb

Coulomb's law

Coulomb's law states that "like charges repel, and unlike charges attract," but the more complete form determines the strength of the Coulomb force; Coulomb's law shows how strong the push or pull (the force) is between two points of charge, like a proton and electron in an atom. read more on Coulomb's law


A crankshaft is a part in a reciprocating engine, used to convert between reciprocating motion from the pistons and rotational motion from the rest of the vehicle. read more on Crankshaft


The term crest is ambiguous, and has applications in hydroelectric dams as well as small-scale weirs. read more on Crest

Cross section of the Earth

The Cross section of the Earth is a visualization of the composition of the Earth in geological terms. The planet Earth is an immensely complicated and dynamic system, with many different physical and chemical properties. read more on Cross section of the Earth

Cross-sectional area

The cross-sectional area is the area of a two-dimensional shape that is obtained when a three-dimensional object - such as a cylinder - is sliced perpendicular to some specified axis at a point. read more on Cross-sectional area

Crossflow turbine

Crossflow turbines, sometimes known as Mitchell-Banki or Ossberger turbines are a type of turbine that tends to be used in smaller hydroelectric sites with power outputs between 5-100 kW. These turbines are useful for a large range of hydraulic heads, from only 1.75 meters to 200 meters, although usually crossflow turbines are chosen for heads below 40 meters. read more on Crossflow turbine

Crude oil

Crude oil is the liquid component of petroleum and it varies drastically in its composition. Although the specific amounts of different hydrocarbons varies, it is always composed of a series of different hydrocarbons. read more on Crude oil


The cryosphere is the component of the Earth that composed of all solid, frozen water found on Earth. The cryosphere includes water storage areas such as glaciers, iceburgs, snow-covered areas, and sea ice. read more on Cryosphere

Cubic feet

Cubic feet is a unit of volume, given by the dimension of ft3. It is used in the Imperial system of units, and can be visualized as a box with side lengths of 1 ft (0.3048 meters). read more on Cubic feet

Cubic meter

A cubic meter is a measure of volume, corresponding to a box with side lengths of one meter. read more on Cubic meter


The curie or Ci is the non-SI unit for radioactive decay measuring the radioactivity of a substance. read more on Curie


Currency is a medium of exchange issued by the central bank of a country that is declared to be legal tender and is exchanged for goods and services, it is also used as an accounting tool and in certain forms it acts as a store of value.[26] A fixed currency is pegged to another currency such as the USD or a commodity such as gold and the rate of exchange does not change. read more on Currency


Current is the amount of electric charge flowing per second within a conductor. It is what carries the electric power from power plants, through the transmission system and distribution system for industrial and home electricity use. It is otherwise known as electricity. read more on Current

Current transformer

Current transformers measure the amount of electric current flowing through a particular wire on the electrical grid[27] by making a secondary current that is proportional (but much less than) the amount of current flowing in that wire. read more on Current transformer


Curtains are coverings for windows that are placed inside a home and are used to block light or thermal radiation from entering the home by covering the interior pane of the window. Curtains are generally cloth and are made of fabrics of differing opacity depending on how much light is to be blocked. read more on Curtain

Curtain wall

The curtain wall is a thin portion of the building envelope that has an independent frame assembly containing in-fills of glass, metal panels, or thin stone. These walls do not support any of the load of the building itself, and transfer the wind and gravity loads to the building structure. read more on Curtain wall

Cyclone separator

Cyclone separators or simply cyclones are separation devices that use the principle of inertia to remove particulate matter from flue gases. read more on Cyclone separator

Dam failures

A dam failure is simply an uncontrolled release of water from a hydroelectric reservoir through a hydroelectric dam as a result of structural failures or deficiencies in the dam. read more on Dam failures


Daylighting is the process of using natural sunlight to light a building to help reduce energy costs, especially in commercial buildings.[28] The process of daylighting includes controlling how much natural light (both diffuse and direct) enters a building. read more on Daylighting

DC generation

Direct current generation can be quite similar to AC generation, in that the electromagnetic generation of energy still requires all the same essential components. However, direct current is also generated by photovoltaic cells and batteries. read more on DC generation

Deadweight loss

A deadweight loss is the result of inefficiencies in a market resulting from a poor allocation of goods and services. read more on Deadweight loss


Decane is a hydrocarbon that can be burned as a fuel. It's chemical formula is C10H22, and is a colourless liquid with a strong odour. read more on Decane


Deforestation is the temporary or permanent removal of large expanses of forest for agriculture or other uses. Harvesting materials like timber and fuelwood by chopping down forests yields many economic benefits, however it comes along with many harmful environmental impacts. read more on Deforestation


Demand is "the ability and desire to buy goods and services, or the quantity of a good or service that is needed in order to meet the requirements of the user." read more on Demand


Density refers to the ratio between the mass and volume of an object. read more on Density


Depreciation refers to the loss of value of an asset or the capital stock of a firm over time. read more on Depreciation

Detailed pollution data

Detailed pollution data, visualized below, can help clarify trends in levels of primary pollutant emissions in Canada and help explain where certain pollutants come from. read more on Detailed pollution data


Deuterium is a stable isotope of hydrogen, consisting of 1 proton, 1 neutron and 1 electron. It is found fairly rarely in nature, making up a mere 0.015% of the total hydrogen abundance. read more on Deuterium

Developed countries

Developed countries are generally countries that are seen as being more advanced in terms of technologies, while also having a higher human development index and a higher quality of life when compared to other countries. In addition to this, developing countries generally have more advanced economies, which means the per capita income level and diversity of exports is generally higher. read more on Developed countries

Developing countries

Developing countries are generally countries that are seen as being less advanced in terms of technologies, while also having a lower human development index and a poorer quality of life. In addition to this, developing countries are seen as having developing economies, which means the per capita income level and diversity of exports is generally lower. read more on Developing countries


Dielectric materials are insulators that can be polarized in the presence of an electric field. Without an electric field, the polar molecules of the dielectric are oriented in random directions. An applied electric field causes the molecules to reorient uniformly since the negative and positive ends of each molecule in the dielectric are attracted to the positive and negative sources of the field, respectively. read more on Dielectric


Diesel is an energy-dense secondary fuel (or energy currency) used to power many heat engines, including cars, trucks, and diesel generators. It can be a petroleum derivative, or it can be made from biomass. read more on Diesel

Diesel engine

A diesel engine is a type of internal combustion heat engine, powered by diesel. These engines run small electricity generators called diesel generators often in remote areas as well as the engines of cars and trucks (both large and small). read more on Diesel engine

Diesel generator

Diesel generators are very useful machines that produce electricity by burning diesel fuel. These machines use a combination of an electric generator and a diesel engine to generate electricity. read more on Diesel generator

Diesel vs gasoline engine

The two main types of engines used in cars right now burn either diesel fuel, or gasoline. While the engines share many of the same parts, including the engine block, the engines have a few distinct differences, namely, ignition, starter motors, and outputs read more on Diesel vs gasoline engine


Diffusion is a form of mixing, usually where molecules disperse. read more on Diffusion


A diode is an electrical component with the fundamental property of only allowing current to flow in one direction through it. This property is essential to the conversion of alternating current into direct current, which is why diodes are commonly found in AC adapters and other rectifier circuits. read more on Diode

Diode operation

The way that a diode operates can be difficult to understand as it involves fairly advanced quantum mechanics. However, at the simplest level the operation of a diode can be understood by looking at the flow of positive charges (or "holes") and the negative charges (the electrons). read more on Diode operation

Direct current

Direct current (DC) is uni-directional, so the flow of charge is always in the same direction. read more on Direct current

Discount rate

The discount rate is the interest rate that firms use to determine how much a future cash flow is worth in the present. read more on Discount rate


The process of discounting is used to determine the present discounted value of a payment or revenue flow made in the future. This is how much something in the future would be worth in the present. read more on Discounting

Discovery of the greenhouse effect

One common misconception about the greenhouse effect is that it is a new concept. However, scientists have speculated about the existence of some greenhouse effect since the 1800s. One of the most notable scientists who investigated the concept of a greenhouse effect was Svante Arrhenius, a Swedish scientist who in 1896 was the first to claim that the combustion of fossil fuels could eventually result in global warming. read more on Discovery of the greenhouse effect

Dispatchable source of electricity

A dispatchable source of electricity refers to an electrical power system, such as a power plant, that can be turned on or off; in other words they can adjust their power output supplied to the electrical grid on demand. read more on Dispatchable source of electricity

Distribution grid

Distribution grid refers to the final stage of the electrical grid in which electricity is distributed to homes, industry, and other end use products. read more on Distribution grid

Distribution transformer

A distribution transformer is the type of transformer that performs the last voltage transformation in a distribution grid. It converts the voltage used in the transmission lines to one suitable for household and commercial use, typically down to 240 volts. read more on Distribution transformer

District heating

District heating is the process of using a network of insulated pipes used to deliver hot water or steam from the point of generation to end users. read more on District heating

Domestic water heating

Domestic water heating is the process of warming water for personal use, and it can consume a large amount of energy. read more on Domestic water heating


A door is a vital part of the building envelope as it serves as an opening in the barrier between the outside and inside environments. read more on Door


Doping is the practice of introducing very small amounts of certain foreign atoms into the crystal lattice of a semiconductor to modify its electrical properties. These foreign atoms add charge carriers to the semiconductor by creating either an excess or a deficiency of electrons around the foreign atom. read more on Doping


Radiation dose is the amount of energy absorbed from being exposed to different forms of ionizing radiation. read more on Dosage

Downstream oil and gas industry

Downstream industry is the portion of the oil and natural gas industry that is responsible for the refining, distributing, and retail of petroleum products. This portion of industry includes oil refineries, petrochemical plants, petroleum products distributors, and natural gas distribution companies. read more on Downstream oil and gas industry


Drag is a force that opposes or resists motion, caused by collisions of moving objects with molecules in a fluid like air or water. It is much like surface friction in that it opposes moving objects, except that it occurs in a moving fluid. read more on Drag

Drake Landing solar project

The Drake Landing solar project is a renewable energy project that provides homes with their energy primarily from solar energy. It is a community built in Okotoks, AB, Canada, consisting of 52 highly efficient homes, which receive 90% of their energy for space heating from the Sun. read more on Drake Landing solar project

Drive shaft

The drive shaft (also called propeller shaft or prop shaft) is a component of the drive train in a vehicle, with the purpose of delivering torque from the transmission to the differential, which then transmits this torque to the wheels in order to move the vehicle. read more on Drive shaft

Drive train

The drive train of a vehicle refers to the group of components that act to deliver power to the driving wheels of a vehicle. read more on Drive train

Driving forces for emission scenarios

Driving forces for emission scenarios are the factors that influence how society will emit greenhouse gases in the future. read more on Driving forces for emission scenarios


A drought is a deficiency of precipitation over an extended period of time, relative to the region's typical precipitation levels. read more on Drought

Dry scrubber

A dry scrubber or dry scrubber system is one type of scrubber that is used to remove harmful materials from industrial exhaust gases before they are released into the environment. Dry scrubbers are the type most commonly used in plants today, and they utilize a collection of dry substances to remove acidic gases that contribute to acid rain. read more on Dry scrubber

Dynamic tidal power

Dynamic tidal power is a technology that uses the difference between the potential energy and kinetic energy of tides. read more on Dynamic tidal power

Dyson sphere

The Dyson sphere or Dyson shell is a theoretical megastructure that was first proposed by astronomer Freeman Dyson in 1959. This has been and will remain science fiction for a long time, but is interesting from the perspective of the total limit of energy a society can access. A Dyson sphere is a sphere approximately the size of a planetary orbit that would be able to harvest all the sun's energy and, on the inside surface, would be habitable to humans. read more on Dyson sphere


E-coatings or Low-emissivity coatings are thin coatings that are put on top of traditional glass windows that prevent or limit certain wavelengths of light from passing through the pane while still allowing the passage of visible light. read more on E-coating


Earth is the planet people live on, but can also mean electrical grounding. Usually calling the ground wire the Earth is a British term.

Earth the planet has a rich structure under the surface, read about that at Cross section of the Earth. read more on Earth

Earth Temperature without GHGs

The temperature of the Earth, as well as the temperature of other planets, depends strongly on the composition of the atmosphere and how significant the effects of the greenhouse effect are.

On Earth, the temperature is kept at a comfortable level since the atmosphere traps some of the radiant heat from the Sun, warming the surface and sustaining life. This trapping is done by greenhouse gases in our atmosphere, which absorbs some infrared heat radiation and reradiates some to the surface of the Earth, warming it. read more on Earth Temperature without GHGs

Earth's energy budget

Earth's energy budget refers to the tracking of how much energy is flowing into and out of the Earth's climate, where the energy is going, and if the energy in balances with the energy out. read more on Earth's energy budget

Earth's energy flow

Energy flows are the energy transformations and movement that occur once energy has reached the Earth. These flows describe how energy is distributed and how it interacts with objects, determining certain climate properties. read more on Earth's energy flow

Earth's heat balance

Earth's heat balance is and extremely important factor in what makes the Earth livable. The fact that the Earth can respond to slight changes in the amount of incoming radiation to maintain a fairly stable temperature is a result of Earth's energy budget. This phenomenon is also closely connected to flows on the Earth, and the Solar energy to the Earth. read more on Earth's heat balance

Economies of scale

Economies of scale means that production gets cheaper when more units are produced (up to a certain point). The savings come from spreading the cost of production over a larger number of units. read more on Economies of scale


An ecosystem is a community of different species interacting with one another and their physical environment.[29] Depending on the focus of interest or study the extent of an ecosystem may range from very small spatial scales, such as a small pond, to the entire planet. read more on Ecosystem


Efficiency in physics (and often for chemistry) is a comparison of the energy output to the energy input in a given system. read more on Efficiency

El Nino Southern Oscillation

El Niño-Southern Oscillation, also known as ‘ENSO’ for short, means ‘The Little Boy’ or ‘Christ Child’ in Spanish. It is a large scale ocean-atmosphere climate interaction that originates in the Pacific ocean but spreads across the world. read more on El Nino Southern Oscillation

Elastic potential energy

The Potential energy stored in a spring (or any similar object) is known as the elastic potential energy. It is stored by the deformation of an elastic material such as the spring in Figure 1. read more on Elastic potential energy

Elasticity vs plasticity

Objects deform when pushed, pulled, and twisted. Elasticity is the measure of the amount that the object can return to its original shape after these external forces and pressures stop. read more on Elasticity vs plasticity

Electric dipole

An electric dipole is a separation of charges of opposite sign, typically introduced by a simple case of two charges, both with equal magnitude but opposite charge. read more on Electric dipole

Electric field

The electric field is one of the fundamental results of electromagnetism, created by a static (stationary) charge, or by a dynamic (changing in time) magnetic field read more on Electric field

Electric generator

Electric generators are used to transform mechanical or kinetic energy into electric potential difference, also known as voltage. read more on Electric generator

Electric meter

An electric meter is a device used to measure the electrical energy usage of a home, building, or other electrically powered device. They are used in order to provide accurate billing to customers. read more on Electric meter

Electric motor

An electric motor is a device used to convert electricity into mechanical energy and because of this, is the opposite of an electric generator. read more on Electric motor

Electric power

Electric power is a transfer of energy over time, just like un-prefixed power, specifically it refers to energy transfer in the form of electricity, sending current through conductors. read more on Electric power

Electric power to the grid

Electrical power to the grid is the output power generated by a power plant through the use of a fuel or flow of energy. This power is output by these plants as electricity and fed to the grid via electrical transmission in order to meet society's electrical needs. read more on Electric power to the grid

Electric vehicle

Electric vehicles (EV) are vehicles that use electric motors as a source of propulsion. EVs utilize an onboard electricity storage system as a source of energy and have zero tailpipe emissions. read more on Electric vehicle

Electric vehicle emissions

Electric vehicles (EVs) do not produce carbon dioxide through driving. Because of this, many people wrongly assume that they are emissions free vehicles, but this is not the case. Emissions from EVs fall into two categories: Life cycle emissions, and beyond tailpipe emissions. read more on Electric vehicle emissions

Electric vehicle practicality

One topic that arises when discussing alternative vehicle options is the practicality of electric vehicles. Specifically, investigating factors such as ownership costs - factoring in battery replacement, practicality issues, and environmental impacts help understand the real-world positives and negatives of electric vehicles. read more on Electric vehicle practicality

Electrical component

An electrical component is the general term for any part of an electric circuit. read more on Electrical component

Electrical conductance

Electrical conductance, G, is the reciprocal of resistance (R) read more on Electrical conductance

Electrical conductivity

Electrical conductivity is a property of materials that determines how well a given material will conduct electricity. read more on Electrical conductivity

Electrical energy

Electrical energy is the most convenient forms of energy. Electrical energy is easy to move from one location to another and easy to use, but it is almost impossible to store in any large quantity. read more on Electrical energy

Electrical generation

Electricity is an energy currency, rather than an energy source, which means that electrical generation needs to start from a primary energy source like a fuel or a flow. These fuels and flows are usually turned into electric current which transmits electric power to the grid. read more on Electrical generation

Electrical grid

The electrical grid is the intricate system designed to provide electricity all the way from its generation to the customers that use it for their daily needs. These systems have grown from small local designs to what they are today, stretching thousands of kilometers and connecting millions of homes and businesses. read more on Electrical grid

Electrical insulation

Insulation is the term used for a variety of materials used to reduce the transfer of energy. Insulation is used around electric wires to protect the wire from the environment or the environment (like people) from the wire. It is a key safety feature in wiring. read more on Electrical insulation

Electrical insulator

Electrical insulators are materials with a high resistivity (resistivity is a property of the material) so they can make objects with a high resistance. This allows insulators to prevent electrical current from flowing where it's not wanted. read more on Electrical insulator

Electrical load

An electrical load is simply any component of a circuit that consumes power or energy. In a household setting, the most obvious examples of electrical loads include light bulbs and appliances. read more on Electrical load

Electrical outlet

Electrical outlets (also known as outlets, electrical sockets, plugs, and wall plugs) allow electrical equipment to connect to the electrical grid. The electrical grid provides alternating current to the outlet. There are two primary types of outlets: domestic and industrial. read more on Electrical outlet

Electrical safety devices

This page examines these electrical safety devices. Namely, fuses, circuit breakers, and ground fault circuit interrupters. read more on Electrical safety devices

Electrical substation

Electrical substations are the interface between parts of the distribution systems and transmission systems. read more on Electrical substation

Electrical transmission

Electrical transmission is the process of delivering generated electricity - usually over long distances - to the distribution grid located in populated areas. read more on Electrical transmission


Electricity is energy harnessed from the configuration or movement of electrons - the former being static electricity, and the latter being the electricity that comes from the electrical outlet or flows through overhead power-lines read more on Electricity

Electricity as an energy currency

Electricity is the classic example of an energy currency.[30] An energy currency is simply some transformed form of energy that came from a primary source, but is easier to use, transport, or store. Several authors have introduced the idea of energy currency as a way to think about these useful intermediate forms of energy. read more on Electricity as an energy currency


An electrode is a conductor that is used to make contact with a nonmetallic part of a circuit. read more on Electrode

Electromagnetic force

The electromagnetic force, also called the Lorentz force, explains how both moving and stationary charged particles interact. It's called the electromagnetic force because it includes the formerly distinct electric force and the magnetic force; magnetic forces and electric forces are really the same fundamental force. read more on Electromagnetic force

Electromagnetic induction

Electromagnetic induction is the production of an electromotive force (EMF) being created as a result of relative motion between a magnetic field and a conductor. read more on Electromagnetic induction

Electromotive force

Electromotive force (EMF) is a voltage developed by any source of electrical energy such as a battery or photovoltaic cell. read more on Electromotive force


Electrons are negatively charged particles that exist in a cloud around the nucleus of an atom. read more on Electron

Electron hole

An electron hole is one of the two types of charge carriers that are responsible for creating current in semiconducting materials. A hole can be seen as the "opposite" of an electron. read more on Electron hole

Electron volt

An electron volt (also written electron-volt and eV) is a unit of energy, specifically the energy that it takes to move an electron through the potential difference of 1 volt (or a proton moving through the same potential difference, in a different direction). read more on Electron volt

Electrostatic precipitator

An electrostatic precipitator is a type of filter that uses static electricity to remove soot and ash from exhaust fumes before they exit the smokestacks. read more on Electrostatic precipitator

Embodied energy

Embodied energy is the energy that is consumed in order to build a given usable object. This includes the energy from material extraction, refining, processing, transporting, and fabricating. read more on Embodied energy

Emission scenario

Emission scenarios are possible pathways that society might take in the the emission of greenhouse gases in the future. It is hard to predict what will occur in society in the next 5 years, let alone to predict the next 100. Society could continue to pollute heavily, or it could switch to minimal emissions in harnessing its energy, or anything in between. read more on Emission scenario


Emissions are defined simply as something that is emitted;[31] in an energy sense, these are most often waste products of a process aimed at obtaining useful work. The most common emissions from energy are associated with the generation of electricity and the transportation of goods and services, the content of which depends on what methods were used to accomplish these tasks. read more on Emissions

Emissions trading

Emissions trading is John H. Dales's revolutionary idea of using market forces to reduce pollution by making companies buy and sell the right to pollute. read more on Emissions trading

End use energy

End use energy is the energy directly consumed by the user, as opposed to primary energy which is the energy that is harvested directly from natural resources. End use energy includes electricity, gasoline, and natural gas. read more on End use energy


One way to describe energy is that it can cause a push or pull over some distance. This leads to the idea that energy is the ability to create change. Objects and collections of objects have energy that can only be indirectly observed - by observing what energy does. read more on Energy

Energy conversion technology

Energy conversion technology refers to any system that converts energy from one form to another. read more on Energy conversion technology

Energy currency

Energy from primary energy sources is often transformed into different forms to make it easier to use, transport, or store. These forms are called energy currencies. read more on Energy currency

Energy density

Energy density is the amount of energy that can be stored in a given mass of a substance or system.[32][33] The higher the energy density of a system or material, the greater the amount of energy stored in its mass. read more on Energy density

Energy density of storage devices

Energy density of storage devices is of great consideration when deciding which storage device to use for a given scenario. If a storage device has a larger energy density than another, this means that it can be smaller and/or weigh less while containing the same amount of energy. read more on Energy density of storage devices

Energy density vs power density

Energy density and power density are similar to energy and power, except that their values relate to volume. Gasoline has a higher energy density than wood, and a capacitor has a higher power density than a battery. read more on Energy density vs power density

Energy distribution technology

Energy distribution technology is any human-made system capable of transporting energy in the form of fuels like gasoline, or flows such as electricity. They are the backbone for the energy sector, as they allow energy to be transported globally in order to provide essentially any location with their energy needs, in effect driving the economy. When energy is produced in the form of electricity, gasoline, liquefied natural gas, or any other, it requires transportation to where it can be made useful. Distribution technologies make this task achievable, and in some cases are very efficient. read more on Energy distribution technology

Energy diversification

In order to minimize risk, an investor will diversify their portfolio of investments as a number of different investments is less likely to fail than one large investment. read more on Energy diversification

Energy efficiency

Energy efficiency refers to attempting to get a desired energy service using less primary energy (either fuels or flows). This goal is usually based on having less of an environmental impact and often attempts to be more sustainable, although sometimes people are seeking energy efficiency to save money. read more on Energy efficiency

Energy efficient building design

Energy efficient building design involves constructing or upgrading buildings that are able to get the most work out of the energy that is supplied to them by taking steps to reduce energy loss such as decreasing the loss of heat through the building envelope. read more on Energy efficient building design

Energy flow in ecosystems

The flow of energy in ecosystems is vitally important to the thriving of life on Earth. Nearly all of the energy in Earth's ecosystems originates within the Sun. Once this solar energy reaches Earth, it is distributed among ecosystems in an extremely complex manner. read more on Energy flow in ecosystems

Energy from nuclei

Almost all forms of primary energy come from nuclear reactions. Fossil fuels and biofuels got their energy from sunlight. Geothermal energy comes from radioactive decay or thermal energy left over from when the Earth originally formed (which came from a cataclysmic nuclear explosion, a supernova). Of course, nuclear reactors ultimately get their energy from nuclei. read more on Energy from nuclei

Energy from ocean waves

People have recently been able to start harnessing energy from ocean waves, but could be a very promising primary energy source. read more on Energy from ocean waves

Energy from water

The energy from water can be harnessed to be useful in a variety of different ways through water wheels or in hydroelectricity generating facilities. read more on Energy from water

Energy intensity

Energy intensity is a measurement that is used to show how much a bit of energy is doing to benefit the economy. This value is calculated by taking the ratio of energy use to GDP, and indicates how well a certain economy is using their fuel sources. read more on Energy intensity

Energy loss

When energy is transformed from one form to another, or moved from one place to another, or from one system to another there is some energy loss. This means that when energy is converted to a different form, some of the input energy is turned into a highly disordered form of energy, like heat. read more on Energy loss

Energy mix

The energy mix of a country to the combination of different primary energy sources that make up the total primary energy supply of a country. read more on Energy mix

Energy production

Energy production refers to how much primary energy a country extracts from nature. This is the total of all of the harvested fuels and flows. It is important to note that production does not include any energy imported from another country, or exported to another country. read more on Energy production

Energy security

The definition of energy security has evolved over time but has generally come to encompass the basic idea of a relatively cheap and stable supply of energy for the foreseeable future. read more on Energy security

Energy service

Energy services are the tasks performed using energy. read more on Energy service

Energy service technology

An energy service technology is a system that transforms energy currency (electricity, gasoline, etc.) into a useful task. read more on Energy service technology

Energy storage

Energy storage is useful when energy is harvested at a different time from when it's used. For example, electricity must be used very quickly after it's been made (within milliseconds). read more on Energy storage

Energy transformations

Energy transformations are processes that convert energy from one type (e.g., kinetic, gravitational potential, chemical energy) into another. Any type of energy use must involve some sort of energy transformation. read more on Energy transformations

Energy use by sector

Energy use by sector is useful to look at, since different sectors use different methods of achieving their goals, and therefore have varying demands for different fuels and flows. read more on Energy use by sector

Energy use per person

Energy use per person is a per capita expression of how much energy use there is in a given country or area. read more on Energy use per person

Energy vs power

Energy and power are closely related but are not the same physical quantity. Energy is the ability to cause change; power is the rate energy is moved, or used. read more on Energy vs power


An engine is some machine that converts energy from a fuel to some mechanical energy, creating motion in the process. Engines - such as the ones used to run vehicles - can run on a variety of different fuels, most notably gasoline and diesel in the case of cars. read more on Engine

Engine block

An engine block is the heavy solid-cast part of a vehicle's reciprocating engine that houses the cylinders and their components (pistons, spark plugs, etc) and is an important component for the car. read more on Engine block


Entropy is a measure of the number of ways a thermodynamic system can be arranged, commonly described as the "disorder" of a system. read more on Entropy


The term environment is a broad term with many different definitions, and the term is used differently by different people. Thus it makes it difficult to define exactly what the environment is. read more on Environment

Environmental impact

An environmental impact is defined as any change to the environment, whether adverse or beneficial, resulting from a facility’s activities, products, or services. read more on Environmental impact

Environmental impacts of oil sands

The environmental impact of the oil sands is an issue that has been extremely divisive. As with the extraction and use of any fossil fuel, negative environmental effects arise as a result of the extraction, upgrading, and processing of bitumen from the oil sands. read more on Environmental impacts of oil sands


Equity can be used to refer to two different concepts in economics. This page focuses on economic equality or the level of fairness within the economy of a nation. read more on Equity


An erg is a unit for energy, equal to 1 g·cm2/s2, which can be shown to be equal to exactly 10-7 joules.[34] read more on Erg


Ethane is a hydrocarbon that can be burned as a fuel. It's chemical formula is C2H6 read more on Ethane


Ethanol is a simple alcohol, also referred to as ethyl alcohol or drinking alcohol. It is a common alcohol that can be burned as fuel. It's chemical formula is C2H6O read more on Ethanol


Eutrophication is a state in which big bodies of water such as lakes, parts of the ocean and other reservoirs have a surplus of algal growth due to excessive nutrients such as phosphorus and nitrogen. read more on Eutrophication


The abbreviation EV usually means electric vehicle, while the letters eV stand for electron volt, a unit of energy. read more on EV


Evaporation is a phase change of a liquid to a gaseous state. read more on Evaporation


Evapotranspiration is the transfer of energy from the Earth's surface to the atmosphere in the form of latent heat, due to the evaporation of water from the ground and bodies of water, and the transpiration of water from plants. read more on Evapotranspiration

Everyday force

these are forces commonly observed in day-to-day life. read more on Everyday force

Excise tax

An excise tax is a tax on a particular good that is paid by the seller and is passed on to the buyer as part of the cost. read more on Excise tax

External forcing

An external forcing is a type of climate forcing agent that impacts the climate system while being outside of the climate system itself. read more on External forcing

External heat engine

An external heat engine (EHE) refers to any engine that receives its heat from a source other than the fluid that makes the engine work. read more on External heat engine


An externality is an effect that an economic transaction has on a party who is not involved in the transaction. read more on Externality


Fahrenheit is a unit of temperature in the imperial system of units. It is equal to 9/5 degrees Celsius; however, the two scales have different values for the freezing point of water. It is used as the official temperature scale in the USA, along with a few other Caribbean countries. read more on Fahrenheit


Famine is the scarcity of food over an extended period and over a large geographical area, such as a country. They may be triggered by extreme climate events such as drought or floods, but can also be caused by disease, war, or other factors. read more on Famine


The farad is a unit of capacitance, named after physicist Michael Faraday, used to describe storage of charge in capacitors. read more on Farad

Feed in tariff

The aim of a feed-in tariff (FIT) is to encourage the use of renewable technology for the generation of electricity. To encourage this behavior, governments guarantee electricity generation firms a long-term contract with a fixed price for each kilowatt hour. read more on Feed in tariff

Feedback cycle

A feedback cycle is some cyclic structure of cause and effect that causes some initial change in the system to run through a series of secondary effects, eventually influencing the initial change in some way. read more on Feedback cycle


Fenestration refers to the openings in the building envelope, including the installation of windows, doors, and skylights. read more on Fenestration


Fertile is a term used to describe an isotope that is not itself fissile (it cannot simply undergo fission by thermal neutrons), but can be converted into a fissile material through irradiation in a nuclear reactor. After this, the fission of this isotope could result from a radioactive decay. read more on Fertile

Fertility rate

General Fertility Rate, or simply Fertility Rate, is the total number of live births per 1000 women of reproductive age per year. read more on Fertility rate

Fibrous insulation

Fibrous insulation is a specific type of insulation that works by capturing air within the fibers, preventing heat transmission through convection. This type of insulation also limits heat conduction between molecules of gases by minimizing collisions between the particles. read more on Fibrous insulation


Financing is the provision of funds to a firm so they can expand their activities based on the promise that the funds will be paid back with interest or the financier will acquire a stake in the firm. read more on Financing

First law of thermodynamics

The first law of thermodynamics states that the change in internal energy of a system ([math]\Delta U[/math]) is equal to the work done by or to the system ([math]W[/math]) and the heat that flows in or out of it ([math]Q[/math]). read more on First law of thermodynamics

Fiscal incentive

Fiscal incentives are aspects of fiscal policy that are able to influence and induce the behaviors of people and firms to act in a particular way by offering financial reward for certain activities. read more on Fiscal incentive

Fish passage

A fish passage is any device used to promote and regulate safe fish migration up and downstream from hydroelectric facilities. If fish cannot migrate and rear without interruption, populations can significantly decrease. read more on Fish passage

Fish screen

A fish screen is a structure built to prevent fish from entering hydroelectric dams, aqueducts, diversion rivers, or other man-made structures. These screens are meant to supply water free of debris to power plants and other facilities without harming aquatic life. read more on Fish screen


Fissile material refers to a nuclide that is capable of capturing a slow or thermal neutron and undergoing fission. read more on Fissile

Fixed cost

Fixed costs are costs that a firm will incur regardless of its output and are sometimes referred to as overhead. These can be costs such as insurance, rent, utilities and others. These costs are incurred even if the company doesn't produce. read more on Fixed cost


Flammable is a term that describes the ability for a material to ignite. It is often used alongside combustible which also describes the ability to ignite, but the difference is that flammable materials ignite more easily and more vigorously. read more on Flammable


Flaring is the process by which natural gas is burned off in a controlled manner when extracting oil. Otherwise, the natural gas can burn in an uncontrolled way and be very dangerous. Usually, natural gas is captured, but when this is impossible it's flared. Flaring reduces the risk of gas ignition to facilities or to eliminate product that has been isn't fit for use. read more on Flaring


A flood is the overflowing of the normal confines of a stream or other body of water, or the accumulation of water over areas that are not normally submerged.[9] Floods can occur nearly anywhere on Earth; in any place that rain can fall, floods can occur.[35] read more on Flood


An energy flow is a natural process that has energy associated with movement, this energy can be sometimes be harvested. Examples include solar radiation shining on the earth from the sun, or water flowing downstream in a river. These flows can be harnessed to provide energy services such as home heating, transportation and electrical generation. read more on Flow

Flow rate

Flow rate, sometimes represented by Q, is the number of cubic meters of water that pass through a hydroelectric power plant per second.[28] Thus, the unit for flow rate is meters cubed per second (). read more on Flow rate


A fluid is a material that can flow easily and includes both liquids and gases. These materials often contain energy that can be harnessed as primary energy. read more on Fluid


A flume is a deep, narrow channel that is used to transport water from some source - such as a river - to the top of a waterwheel. This is used to direct water flow onto the blades of the wheel, allowing it to move. read more on Flume

Fly ash

Fly ash is a coal combustion product, part of a set of products that makes up the most abundant waste materials worldwide.[8] If not collected, this waste material is blown out with the flue gas in a coal fired power plant. read more on Fly ash


A flywheel is a mechanical device which stores energy in the form of rotational momentum. Torque can be applied to a flywheel to cause it to spin, increasing its rotational momentum. This stored momentum can then be used to apply torque to any rotating object, most commonly machinery or motor vehicles. read more on Flywheel


A foot (ft) is a unit of distance, defined as being equal to 12 inches, or 1/3 of a yard. read more on Foot

Foot pound

A foot pound is a unit of energy, not to be confused with the pound foot, which is a measure of torque. The foot pound is a measure of a pound of force applied over one foot. read more on Foot pound


Forces are interactions between objects - a push or pull. Forces have the ability to make an object speed up, slow down, change direction or change its shape.[36] read more on Force

Forced convection

Forced convection is a special type of heat transfer in which fluids are forced to move, in order to increase the heat transfer. read more on Forced convection

Forest fire

Forest fires or wildland fires are spontaneously occurring forest, bush and plain fires and can occasionally be controlled. read more on Forest fire

Fossil fuel

Fossil fuels are a category of fuels that are made by geological processes acting on dead organisms, often hundreds of millions of years old read more on Fossil fuel

Fossil fuel formation

Fossil fuel formation refers to the process that takes place over the time span of hundreds of millions of years to produce a variety of fossil fuels including coal, oil, and natural gas. read more on Fossil fuel formation


The foundation of the home is a large slab of material - generally stone or concrete - that is built on top of the Earth where a home is to be built and supports the building from underneath, promoting stability of the structure of the home. The foundation is just one component of the building envelope. read more on Foundation

Fracking-related seismic activity

Fracking-related seismic activity refer to earthquakes of varying magnitudes that occur as a result of the hydraulic fracturing process. read more on Fracking-related seismic activity

Fractional distillation

Fractional distillation is the process by which oil refineries separate crude oil into different, more useful hydrocarbon products based on their relative molecular weights in a distillation tower. This is the first step in the processing of crude oil, and it is considered to be the main separation process as it performs the initial rough separation of the different fuels. read more on Fractional distillation

Fracturing fluid

Fracturing fluid is a type of liquid that is pumped underground during hydraulic fracturing processes to create small fissures in below-ground rock formations. read more on Fracturing fluid

Francis turbine

A Francis turbine is a type of turbine used most frequently in medium- or large-scale hydroelectric plants. These turbines can be used for heads as low as 2 meters and as high as 300 meters. Additionally, these turbines are beneficial as they work equally well when positioned horizontally as they do when they are oriented vertically. read more on Francis turbine

Free market

A market economy (also known as a free market) is one that is unburdened by regulation and the economy is therefore subject to the supply and demand market forces. read more on Free market

Free-rider problem

When a person enjoys the benefits of a public good without contributing to the cost of it, they are known as a free-rider. read more on Free-rider problem


Frequency refers to how often an event occurs. read more on Frequency


Friction is an everyday force that arises from two surfaces interacting. read more on Friction

Frozen ground

Frozen ground occurs when ground water freezes due to the temperature of the ground being below 0°C.[2] The ground freezes when the water freezes between rocks, soil, and pebbles. In this context, this frozen water is called pore ice.[8] read more on Frozen ground

Frozen ground and climate change

Climate change is affecting the Earth's frozen ground. Frozen soils help to hold moisture and are impermeable. A thin layer of frozen soil prevents moisture in the layers below from evaporating. Hence frozen ground can help regulate the water cycle.[37] read more on Frozen ground and climate change


Fuels are dense repositories of energy that are consumed to provide energy services such as heating, transportation and electrical generation. read more on Fuel

Fuel cell

Fuel cells are a type of energy conversion technology which take the chemical energy contained within a fuel and transform it into electricity along with certain by-products (depending on the fuel used). read more on Fuel cell

Fuel economy

Fuel economy is a measurement of fuel use (often, but not always, gasoline) for motor vehicles. read more on Fuel economy

Fuel efficiency

This article refers to the thermal efficiency of internal combustion car engines. This is how well a vehicle's engine is able to convert gasoline to distance traveled, as expressed in liters per hundred kilometers, miles per gallon, or kilometers per liter read more on Fuel efficiency

Fuel efficiency savings

Fuel efficiency savings refers to the overall savings based on fuel economy of a vehicle over time. read more on Fuel efficiency savings

Fuel efficiency vs fuel economy

Fuel efficiency and fuel economy are two phrases that are often used interchangeably but have different meanings. The core difference involves fuel efficiency discussing how well a car uses fuel (like gasoline or diesel) and fuel economy measures how much distance a car gets out of fuel. read more on Fuel efficiency vs fuel economy

Fuel vs flow

Different types of primary energy fall into two main categories: fuels and flows. Fuels like coal, natural gas, and uranium are dense stores of energy that are consumed when used. Flows are natural processes that have energy associated with movement. Using a flow means harnessing energy that comes from this movement like wind and tides. read more on Fuel vs flow

Fukushima nuclear accident

The Fukushima nuclear accident refers to the events in the Fukushima prefecture of Japan on March 11th, 2011 and the days following. Different articles discuss the radiation release from the Fukushima nuclear accident and the health effects of the Fukushima nuclear accident. read more on Fukushima nuclear accident

Fundamental force

At the most fundamental level, all the forces in the universe come from only four forces read more on Fundamental force


A furnace is part of the HVAC system inside of buildings that provides heating to the building by warming air and sending it through the ductwork. They can also be known as boilers or heaters (although both of these are more general terms). read more on Furnace


A fuse is an electrical safety device that has the capability to protect a circuit from excessive electric current. read more on Fuse


The Imperial gallon is a unit of volume in the imperial system of units, where the US gallon is used exclusively in the United States. The imperial gallon is 20% larger than the US gallon. read more on Gallon

Gamma decay

Gamma decay is one type of radioactive decay that a nucleus can undergo. What separates this type of decay process from alpha or beta decay is that no particles are ejected from the nucleus when it undergoes this type of decay. Instead, a high energy form of electromagnetic radiation - a gamma ray photon - is released. read more on Gamma decay


Gases, along with liquids and solids, are one of the states of matter. read more on Gas

Gas centrifuge

Today, the Gas Centrifuge (a type of centrifuge is the main way we go about enriching uranium for nuclear fuel fabrication. read more on Gas centrifuge

Gas filling

Gas filling is a method where a low-conductivity inert gas, such as Argon, is used instead of air in window cavities in order to reduce heat transmission through the window. read more on Gas filling

Gas turbine

A gas turbine is a type of turbine that uses pressurized gas to spin it in order to generate electricity or provide kinetic energy to an airplane or jet. read more on Gas turbine

Gaseous diffusion

Gaseous diffusion was the first economic enrichment process of uranium to be successfully developed.[32] read more on Gaseous diffusion


Gasoline is an energy-dense secondary fuel that can be thought of as an energy currency. It is used to power many heat engines, most importantly it acts as a fuel for a large proportion of cars. Gasoline is made when crude oil is broken into various petroleum products through a process of fractional distillation. read more on Gasoline

Gasoline engine

A gasoline engine is a type of heat engine, specifically an internal combustion, that is powered by gasoline. These engines are the most common ways of making motor vehicles move. read more on Gasoline engine

Gauge pressure

Gauge pressure is a measurement of pressure relative to atmospheric pressure. For this measure of pressure, the zero point is set to be at 1 atm. read more on Gauge pressure


A gear is a type of simple machine that is used to manipulate the magnitude or direction of a force. Gears are used in combination and are linked together by their teeth - referred to as cogs - in order to form a "gear train". These gear trains are useful for transferring energy from one part of a system to another. read more on Gear

Generation IV nuclear reactors

Generation IV nuclear reactors are innovative nuclear reactors expected to facilitate nuclear power to meet the energy needs of society in the future. In addition to meeting the energy need, this generation of reactors is designed to fulfill the concept of sustainable development. read more on Generation IV nuclear reactors

Geothermal district heating

Geothermal district heating is the use of the Earth's natural thermal energy in order to provide heat to a group of buildings. read more on Geothermal district heating

Geothermal electricity

Geothermal electricity is electricity generated by the use of geothermal energy. Not all countries can accomplish this efficiently, as the temperatures beneath the surface of the Earth vary from place to place. read more on Geothermal electricity

Geothermal energy

Geothermal energy refers to primary energy that is extracted from the thermal energy deep underground. This thermal energy can be used directly for heat or to create electricity. read more on Geothermal energy

Geothermal gradient

Geothermal gradient is the amount the Earth’s temperature increases with depth, indicating heat flowing from the Earth’s warm interior to its surface. read more on Geothermal gradient

Geothermal heating

Geothermal heating is the use of the Earth's natural thermal energy, known as geothermal energy, for one's heating needs. read more on Geothermal heating

Geothermal industrial heat

Geothermal industrial heat is the use of the Earth's natural thermal energy in order to provide heat to industries. read more on Geothermal industrial heat

Geothermal power plants

Geothermal power plants are used in order to generate electricity by the use of geothermal energy (the Earth's internal thermal energy). They essentially work the same as a coal or nuclear power plant, the main difference being the heat source. With geothermal, the Earth's heat replaces the boiler of a coal plant or the reactor of a nuclear plant. read more on Geothermal power plants

GHGs for AFVs

Alternative fuel vehicles or AFVs produce considerably less greenhouse gas emissions or GHGs compared to gasoline vehicles. read more on GHGs for AFVs


A gigatonne is 1,000,000,000 tonnes, and is often used when discussing human carbon dioxide emissions. read more on Gigatonne

Gini coefficient

The Gini coefficient measures the amount of income inequality in a given country or region, when measured, a group with a coefficient of 0 has complete equality whereas a group with a coefficient of 1 has total inequality. read more on Gini coefficient

Glacial lake outburst flood

Glacial lake outburst floods (GLOFs) are floods that occur from an unstable natural dam formed from a glacial retreat.[38] read more on Glacial lake outburst flood


A glacier is a large mass of ice on land that flows downhill under the force of gravity. A significant fraction of the glaciers in the world are shrinking, which is a big concern because glaciers provide drinking and irrigation water for a significant fraction of the world. read more on Glacier


Glazing is the term that describes the transparent material used in windows.[39] Changing the type of glazing, the amount of glazing, or the material placed between layered glazing can greatly affect the energy performance of a window. read more on Glazing

Global climate model

Global climate models (also referred to as general circulation models, both abbreviated as GCM) are climate models that take into account the physical processes in the atmosphere, ocean, cryosphere and land surfaces. read more on Global climate model

Global surface temperature

The global surface temperature is an estimate of the overall average temperature of the surface of the Earth across the globe. The value is obtained by measuring the average water temperature of the first few meters below the surface of the ocean and the temperature between the land surface and 1.5 meters above. read more on Global surface temperature

Global warming potential

Global warming potential is a measurement, based around CO2, of how much heat a greenhouse gas traps in the atmosphere. It is often abbreviated GWP. read more on Global warming potential

Goods and services

A good is a tangible, physical thing that consumers want to consume or have. In contrast, pollution is not a good as people do not want to consume it.[40] A service is not a tangible or physical entity but is still sought after by consumers. Often, a service can also be performed at a distance. read more on Goods and services


Graphene is a one atom thick crystalline form of carbon. Graphene's structure is organized into a hexagonal (honeycomb) shape and can exist naturally in the stacked form of graphite or charcoal. Graphene also forms the fundamental structural units of graphene nanotubes. Graphene is best known for its excellent tensile strength, transparency to light, and high electrical and thermal conductivity read more on Graphene


Graphite is a mineral composed solely of carbon atoms combined in a hexagonal pattern with one another to form a crystal structure. read more on Graphite

Gravitational constant

The gravitational constant (G) is an experimentally calculated value that is involved in determining the gravitational force between two objects. read more on Gravitational constant

Gravitational field

A gravitational field is a field induced by any object with mass, which will interact with other massive objects by applying a force on it. Gravitational fields are expressed in Newtons per kilogram (N/kg), which is the same unit as acceleration. read more on Gravitational field

Gravitational potential energy

Gravitational potential energy is the energy possessed by masses according to their spatial arrangement and the gravitational force (one of the four fundamental forces) that pulls them towards one another. read more on Gravitational potential energy


The gravitational force (also referred to simply as gravity) is the force that pulls all the masses in the universe together. read more on Gravity


The gray or Gy is the official SI unit for absorbed dose which measures the amount of ionizing radiation that has been absorbed by any material.[41] read more on Gray

Great smog of 1952

The Great Smog of 1952 was a massive pollution event in London, England, where the entire city experienced a heavy smog for over four days from December 5 to December 9, 1952. The smog was reported to be responsible for 4,000 deaths in following weeks, however recent research puts this number more realistically at 12,000. read more on Great smog of 1952

Green investment

Green investing or eco-investing is the practice of only investing in firms that use environmentally conscious and friendly business practices. These firms focus on environmental conservation, low to no carbon projects, the development of renewable energy alternatives and clean air/water projects with very little ecological impact. read more on Green investment

Greenhouse effect

In general, the greenhouse effect refers to any situation where short wavelengths of light pass through some medium (it could be glass or the atmosphere) and get absorbed whereas longer wavelengths of infrared radiation pass through, are re-radiated from objects and then unable to pass through the medium. This results in the trapping of longer wavelengths and a higher temperature inside the medium. read more on Greenhouse effect

Greenhouse effect on other planets

The greenhouse effect is not the same on all planets, and differs dramatically based on the thickness and composition of the atmosphere. Three planets that show how dramatically the conditions of a planet can change with the different levels of the greenhouse effect are Venus, Earth, and Mars. read more on Greenhouse effect on other planets

Greenhouse gas

Greenhouse gases or GHGs, refer to gases that, when present in the upper atmosphere, contribute to global climate change. The cause of this contribution is due to the absorption and re-emission of radiation within the infrared range. read more on Greenhouse gas

Greenland ice sheet

The Greenland ice sheet is a large body of ice that covers approximately 80% of the surface of Greenland.[2] At 1.7 million square kilometres (3 times the size of the province of Alberta) it is the second largest ice body in the world. The Greenland ice sheet is however much smaller than the Antarctic ice sheet.[2] The ice sheet is 2,400 kilometres long.[2] read more on Greenland ice sheet

Gross domestic product

Gross Domestic Product or GDP is a measure of the total economic activity of a territory, including all private and public consumption, government expenditure, investment, product inventories, and net exports that occur within that defined territory. read more on Gross domestic product

Ground fault circuit interrupter

A Ground fault circuit interrupter, sometimes called a GFCI or simply a GFI, is an electrical safety device that is mandatory in locations throughout a home where water can come into contact with a wall plug. This includes bathrooms and kitchens. read more on Ground fault circuit interrupter

Ground level ozone

Ground level ozone is a highly reactive secondary pollutant produced from primary pollutants - specifically hydrocarbons and nitrogen oxides - when exposed to sunlight. It is irritating to human life from a visual, scent, and health perspective, as it is a major component of photochemical smog. read more on Ground level ozone

Ground source heat pump

Ground source heat pumps, also known as geothermal heat pumps, are highly effective space heating and cooling technologies that extract heat from the ground. Sometimes the source of this heat is the sun (warming the surface and conducting underground), and other times the heat comes from geothermal energy. The ground source heat pumps are literally pumping heat from the ground into a space, often someone's home. read more on Ground source heat pump


Electrical grounding, otherwise known as earthing, primarily provides a measure of safety against electric shocks by acting as a safety line to redirect electric current in the event of short circuits. read more on Grounding


Groundwater is all of the water found underneath the Earth’s surface. This water comes mostly from rain, melted snow, and other water that seeps through soil, sand and rock. Groundwater comprises almost 30% of the world's fresh water supply and is a significant part of the hydrologic cycle, see specifically groundwater as a part of the hydrologic cycle. read more on Groundwater

Groundwater as a part of the hydrologic cycle

Groundwater plays a key role in the hydrologic cycle. The hydrologic cycle is a sequence of water transformations that occur in the circulation from the atmosphere onto the surface and into the subsurface regions of the earth, and then back from the surface to the atmosphere once again.[21] read more on Groundwater as a part of the hydrologic cycle

Groundwater as a part of the Hydrologic Cycle

Groundwater plays a key role in the hydrologic cycle. The hydrologic cycle is a sequence of water transformations that occur in the circulation from the atmosphere onto the surface and into the subsurface regions of the earth, and then back from the surface to the atmosphere once again.[21] read more on Groundwater as a part of the Hydrologic Cycle

Growing algae

Growing algae is important as algae is used as a food supplement, a biofuel resource, a chemical resource and a waste management system. read more on Growing algae

Gyroscopic motion

Gyroscopic motion is the tendency of a rotating object to maintain the orientation of its rotation. A rotating object possesses angular momentum and this momentum must be conserved. read more on Gyroscopic motion

Half life

Half life is the time that it takes for half of the original value of some amount of a radioactive element to decay. Additionally, one half life is the time that it takes for the activity of a source to fall to half its original value. read more on Half life

Halogen light

Halogen light bulbs are a fairly efficient light bulb that produce light from the flow of electricity. Halogen lights have many uses in television and film production, home and commercial lighting, and in motor vehicles. read more on Halogen light

Hard & soft loan

A hard loan is a loan with very specific parameters and adheres to market conditions such as the interest rate. read more on Hard & soft loan

Harvesting algae

Harvesting algae after its growing cycle is the first step in processing it into biofuel in a commercial process. Harvesting techniques depend on the type of algae used. read more on Harvesting algae


Heat is a transfer of thermal energy caused by a difference in temperature. This temperature difference is also called a temperature gradient.[42] read more on Heat

Heat capacity

Heat capacity (C) is defined as the amount of heat needed to raise the temperature of a system by one degree (Celsius or Kelvin), and is expressed in units of Joules per degree Kelvin (). read more on Heat capacity

Heat engine

A heat engine is a device (like the motor in a car) that produces macroscopic motion from heat. read more on Heat engine

Heat exchanger

Heat exchangers are systems that use a fluid to absorb heat from a hotter outside source without the fluid and hot source mixing together. For example, water can be heated while inside a metal pipe within a furnace or boiler. read more on Heat exchanger

Heat pump

A heat pump is a device that pulls the energy out of air for the purpose of either heating or cooling a space. This process is known as space conditioning. read more on Heat pump

Heat transfer

Heat transfer is the movement or flow of heat energy, often used to describe the dissipation of heat energy from one location to the surrounding environment. Heat transfer is governed with two main properties – temperature, which is the amount of thermal energy available, and the flow of this thermal energy. read more on Heat transfer

Heat transfer mechanisms

Heat transfer mechanisms are simply ways by which thermal energy can be transferred between objects, and they all rely on the basic principle that kinetic energy or heat wants to be at equilibrium or at equal energy states. There are three different ways for heat transfer to occur: conduction, convection, and radiant heat (often referred to as radiation, but that's a more general term that includes many other phenomena).[43] read more on Heat transfer mechanisms

Heat vs temperature

Heat and temperature are a closely related topic, and as such, the difference between the two can be a bit confusing. The core difference is that heat deals with thermal energy, whereas temperature is more concerned with molecular kinetic energy. read more on Heat vs temperature

Heat vs work

The concept of Heat vs Work is an important one in the field of thermodynamics. The idea of how heat and work are distinct but interchangeable forms of energy is crucial to how thermodynamic processes work. Although heat can be transformed into work and vice verse (see mechanical equivalent of heat), they aren't necessarily the same thing. read more on Heat vs work

Heat wave

A heat wave is a period of unusually hot weather, typically lasting two or more days. read more on Heat wave


Space heaters are small, portable heating devices that are generally used when the main heating system in a building is inadequate. Generally if only one room needs heating, space heaters are a more cost effective solution. read more on Heater

Heating registers and vents

Registers and vents, whether they are located on the wall, roof, or floor are an important part of a home's HVAC system. Vents and registers direct air flow throughout a home and work to maintain uniform temperatures throughout the entire building, as well as adding to the aesthetics of a home's design. read more on Heating registers and vents

Heavy water

Heavy water is water that contains heavy hydrogen - also known as deuterium - in place of regular hydrogen. It can also be written as 2H2O or D2O. read more on Heavy water


Helium is the 2nd element on the periodic table, and it is the 2nd most abundant element in the universe; making up 23% of the total mass of all elements (some sources go as high as 25%). read more on Helium


A henry (H) is a unit of inductance, which is the mathematical representation of electromagnetic induction. The unit is named after American physicist Joseph Henry. read more on Henry


Heptane is an alkane with the chemical formula C7H16. As a hydrocarbon, it can undergo hydrocarbon combustion which gives off heat energy. read more on Heptane


Hertz (Hz) is a unit of frequency, measured in s-1 read more on Hertz


Hexane is a hydrocarbon that can be burned as a fuel. Its chemical formula is C6H14, and it is a volatile, colourless liquid that is highly flammable and insoluble in water. read more on Hexane

High energy society

Rich countries today live in a high energy society. These countries have extensive energy infrastructure (like the electrical grid) to give citizens access to energy currencies which provide extensive services that allow them to maintain a high quality of life. read more on High energy society

Home temperature control

Home temperature control refers to the process of keeping the interior of a house at a comfortable, uniform and regulated temperature. read more on Home temperature control

Homogeneous vs heterogeneous

In most technical applications homogeneous means that the properties of a system are the uniform throughout the entire system; heterogeneous (also inhomogeneous) means that the properties change within the system.[44] Any system with two phases like ice and water are said to be heterogeneous. read more on Homogeneous vs heterogeneous

Horizontal well

Horizontal wells are an alternative method for drilling for oil and natural gas when vertical wells do not yield enough fuel or are not possible. Drilling at some non-vertical angle can hit targets and stimulate reservoirs in ways that a vertical well cannot. read more on Horizontal well


Horsepower is a unit of power. Power is an exchange of energy over time. Therefore the measurement of horsepower refers to what the sustained output of an engine is. The term horsepower was invented by James Watt, who made significant improvements to the steam engine. read more on Horsepower

Hot line

A hot line (also known as a phase line) is a wire in the latter stages of the distribution system (like inside your house) that has a non-zero average voltage relative to the Earth (also called ground), as opposed to neutral lines, which are ideally at ground potential. read more on Hot line

Hubbert's peak

Hubbert's peak or Hubbert's curve is a model that approximates the production rate of a resource over a period of time. Specifically, Hubbert's peak refers to the point at which this production rate is at its highest with demand for the resource rising, and after this it predicts a drop in correlation to the increased demand. read more on Hubbert's peak

Human development index

The Human Development Index, also known as the HDI, is an evaluation of several different indicators that shows achievement in human life and well-being overall. read more on Human development index


Hurricanes are large storms (see figure 1) with winds of 119 km/hr or higher.[2] The generic, scientific term for these storms, regardless of where they occur, is tropical cyclone. read more on Hurricane


HVAC is an acronym for heating, ventilating, and air conditioning. It refers to a group of systems and machines used in buildings such as homes and buildings that regulate the internal to ensure comfort.[45] In modern homes, these three functions are often combined into one system. read more on HVAC

Hybrid car

Hybrid cars are a type of motor vehicle that combines the benefits of both gasoline and electric vehicles. Their goal is to increase the mileage and reduce the emissions of a gas-powered car, while overcoming the shortcomings of electric cars such as short distances for their battery charge. read more on Hybrid car

Hybrid lighting

Hybrid lighting is a method of lighting that mixes the use of solar light with artificial light to illuminate buildings. Solar light is channeled in through fiber optic cable bundles and this light is supplemented with some type of artificial lighting. read more on Hybrid lighting

Hydraulic fracturing

Hydraulic fracturing or fracking is a drilling method that is used to extract natural gas or other hydrocarbons that are locked tightly in rocks with poor porosity and permeability. read more on Hydraulic fracturing

Hydraulic head

The hydraulic head is a value that measures the amount of mechanical energy available in water in a river, stream or even lake. The hydraulic head is equivalent to the water level in a static (non-flowing) water body. read more on Hydraulic head

Hydro turbine

Hydro turbines are devices used in hydroelectric generation plants that transfer the energy from moving water to a rotating shaft to generate electricity. These turbines rotate or spin as a response to water being introduced to their blades. These turbines are essential in the area of hydropower - the process of generating power from water. read more on Hydro turbine


The term hydrocarbon refers to the most basic type of organic molecules. They are comprised of only 2 elements: hydrogen and carbon, hence the name hydrocarbons.[46] In general, hydrocarbon molecules are structured with one or more carbon atoms forming a central structure that is surrounded by hydrogen atoms read more on Hydrocarbon

Hydrocarbon combustion

Hydrocarbon combustion refers to the type of reaction where a hydrocarbon reacts with oxygen to create carbon dioxide, water, and heat. Hydrocarbons are molecules consisting of both hydrogen and carbon. read more on Hydrocarbon combustion

Hydrocarbon derivative

Hydrocarbon derivatives are very similar to hydrocarbons, but an atom in the original hydrocarbon gets something (usually another atom) else substituted in. read more on Hydrocarbon derivative

Hydrocarbon resource

Hydrocarbon resources are resources that contain hydrocarbon molecules - molecules consisting of both hydrogen and carbon. Hydrocarbon resources are often known as fossil fuel resources as hydrocarbons are the primary constituent of natural gas, oil, and coal. read more on Hydrocarbon resource

Hydroelectric dam

A hydroelectric dam is one of the major components of a hydroelectric facility. A dam is a large, man-made structure built to contain some body of water. read more on Hydroelectric dam

Hydroelectric facility

A hydroelectric facility is a special type of power plant that uses the energy of falling or flowing water to generate electricity. They do this by directing water over a series of turbines which convert the potential and kinetic energy of water into the rotational motion of the turbine. read more on Hydroelectric facility

Hydroelectric reservoir

A hydroelectric reservoir is a large collection of water behind a hydroelectric dam that makes use of potential energy of water for generating electricity.This water is held back by the dam, and is allowed to fall to generate electricity when it is needed. read more on Hydroelectric reservoir


Hydroelectricity is the electricity that is generated by converting the kinetic and potential energy of flowing water into electrical energy. read more on Hydroelectricity


Hydrogen is the 1st element on the periodic table of elements, and is the most abundant element in the universe: it makes up 75% of the total mass of all of the elements in the universe. read more on Hydrogen

Hydrogen as an energy currency

Hydrogen can be seen as energy currency since it does not naturally occur in its molecular form on Earth, and it must be made by inputting some energy. This turns it into a secondary fuel (a high density repository of energy that's easier to transport and use). read more on Hydrogen as an energy currency

Hydrogen bond

A hydrogen bond is an attraction between molecules (an intermolecular attraction). Hydrogen bonds can form between molecules that have C-H, N-H, Cl-H, and F-H bonds. read more on Hydrogen bond

Hydrogen sulfide

Hydrogen sulfide is a chemical with the formula H2S. Hydrogen sulfide is a dangerous, colourless gas that occurs naturally in many petroleum products but can make up significant amounts of natural gas. It has a distinct "rotten egg" smell. read more on Hydrogen sulfide

Hydrologic cycle

The hydrologic cycle, also known as the water cycle is a way of describing the material flow of water throughout the Earth. This series of steps describes how water moves across the Earth and changes form. These specific steps result in the circulation of water between oceans, the atmosphere, and the land. The water cycle involves natural phenomena that include precipitation such as rain and snow, drainage from rivers, and the return of water to the atmosphere through evaporation and transpiration. read more on Hydrologic cycle


Hydropower is the process of utilizing the mechanical potential energy of flowing water, transforming it into electrical energy to generate electricity. read more on Hydropower


The hydrosphere is the component of the Earth that is composed of all liquid water found on the planet. The hydrosphere includes water storage areas such as oceans, seas, lakes, ponds, rivers, and streams. read more on Hydrosphere


Hypoxia simply means low oxygen. This can apply to a lack of oxygen in air, but in the context of hydropower hypoxia refers to low concentrations of dissolved oxygen in water. An extreme case of hypoxia is anoxia, when there is no oxygen. When there is a low concentration of oxygen in water it is problematic for ecosystems that rely on this water. Water lacking in oxygen is known as hypoxic water.[47] Generally, hypoxic waters have dissolved oxygen concentrations of less than 2 or 3 ppm. read more on Hypoxia

Ideal gas constant

The ideal gas constant is also known as the molar gas constant, the gas constant or the universal gas constant. This constant is written as R, and is a constant of proportionality (constant number that is multiplied on one side of a proportional relationship to make them equal) for the ideal gas law. read more on Ideal gas constant

Ideal gas law

The ideal gas law is a fundamental law to physics, and it provides the basis for heat engines, as well as explains how airbags work, and why an empty water bottle can sometimes pop when you take it on an airplane. read more on Ideal gas law


Ignition is the process of providing the energy that is required to initiate a combustion process. read more on Ignition

Improving fuel efficiency

Improving fuel efficiency refers to the attempt to achieve higher fuel efficiency through a variety of means in a vehicle in an attempt to save money and reduce emissions. read more on Improving fuel efficiency


Impulse is a change in momentum. read more on Impulse

In a barrel of oil

A single barrel of crude oil - once it has been refined - can yield a large number of different, useful petroleum products. The ability to obtain products like gasoline, asphalt, and propane from a single product is part of what makes refining such a vital process. read more on In a barrel of oil

In situ

In situ is a latin phrase that simply means "in position", and in different contexts the term can refer to different things. read more on In situ

In situ oil sands mining

In situ oil sands deposits are simply deposits of oil sand that are located below the ground. The composition of this oil sand is still the same as the oil sand located above ground, the difference being most in situ deposits are buried more than 350-600 meters below ground. read more on In situ oil sands mining

In situ uranium mining

Dissolving solutions are pumped to the uranium underground which allows the uranium to flow through a system of wells to the ground above where it can be processed. read more on In situ uranium mining

Incandescent light bulb

Incandescent light bulbs are devices that convert electricity into light by heating a filament using electrical current until it emits electromagnetic radiation. As current passes through the filament, its high resistance causes its temperature to rise until it glows. read more on Incandescent light bulb

Inclined plane

Inclined planes, also referred to as ramps, are a type of simple machine which manipulate the direction and magnitude of a force.[48] Inclined planes, like all other simple machines, use mechanical advantage which is the ratio of the output force to the applied force. read more on Inclined plane

Income tax

An income tax is levied on the amount of money that a person earns in a given year, tax revenues are collected and used to support government expenditures. In Canada income tax is collected at the provincial and federal level. read more on Income tax

Indicators of a warming world

Humans are warming the planet[49] by increasing the greenhouse gases in the atmosphere. Scientists have many lines of evidence that consistently show that the world is getting warmer. These indicators of global warming include:[49] read more on Indicators of a warming world

Industrial energy use

Industrial energy use, is what allows industries to extract resources and produce goods. read more on Industrial energy use


Inertia is the resistance of any object to changes in its motion or direction. read more on Inertia


Inflation describes the rise of the price of goods and services over a period of time. read more on Inflation

Infrared radiation

Infrared radiation (IR) is a type of radiant energy, with longer wavelengths than the visible light humans can see, but shorter wavelengths than radio waves. Its range extends from fairly small wavelengths near the color red, 700x10-9 m, to nearly a millimeter, 3x10-4 m. read more on Infrared radiation


Insolation is the incident solar radiation onto some object. Specifically, it is a measure of the solar energy that is incident on a specified area over a set period of time. Generally insolation is expressed in kilowatt-hours per square meter per day. read more on Insolation


An institution is "a structure, a mechanism of social order or cooperation, which governs the behaviour of a group of individuals within a human community." read more on Institution


Insulation is material that isolates a physical property. Usually this refers to either:

  1. Electrical insulation which prevents electricity from going where it isn't wanted.
  2. Thermal insulation which prevents heat from going where it isn't wanted.

Often materials that make good electrical insulators also make good thermal insulation, but there are exceptions. read more on Insulation

Integrated gasification combined cycle

Integrated gasification combined cycle (IGCC) is a process of generating electricity from coal, petroleum or biomass while reducing the amount of carbon dioxide and other flue gases released. The cycle combines carbon capture and storage with combined cycle generation to maximize efficiency of the fuel, while also emitting less pollutants. read more on Integrated gasification combined cycle

Intermittent electricity

Intermittent electricity is electrical energy that is not continuously available due to external factors that cannot be controlled, produced by electricity generating sources that vary in their conditions on a fairly short time scale. Sources of intermittent electricity include solar power,[50] wind power,[51] tidal power, and wave power. read more on Intermittent electricity

Internal combustion engine

Internal combustion engines are the most common form of heat engines, as they are used in vehicles, boats, ships, airplanes, and trains. They are named as such because the fuel is ignited in order to do work inside the engine.[52] The same fuel and air mixture is then emitted as exhaust. read more on Internal combustion engine

Internal energy

Internal energy (U) is the microscopic energy contained in a substance, given by the random disordered kinetic energy of the molecules inside, the potential energy between these molecules, and the nuclear energy contained in the atoms of these molecules. read more on Internal energy

International Energy Agency

The International Energy Agency (IEA) was formed in 1974 under the umbrella of the OECD as a response to the turmoil of the 1973 Oil Embargo. read more on International Energy Agency

Inverse square law

A number of physical properties (like the force between two charges) get smaller as they get farther apart in a way that can be represented by an inverse square law. This means that the intensity of the property decreases in a particular way as the distance between interacting objects increases. read more on Inverse square law

Inversion layer

Typically as elevation increases on Earth, the temperature of the air decreases. An inversion layer is a region or layer of the atmosphere in which the temperature stops decreasing with elevation and instead becomes warmer. read more on Inversion layer


An ion is an atom with a net positive or negative charge. read more on Ion


Ionization is the process where one or more ions are formed, generally through the loss of electrons from some neutral entity, resulting in a net positive charge. read more on Ionization

Ionizing radiation

Ionizing radiation is a specific type of radiation that has enough energy to eject an electron from some atom. Generally speaking, the energies of alpha and beta decay particles and gamma ray photons is higher than the ionization energies of atoms and molecules. read more on Ionizing radiation


The Intergovernmental Panel on Climate Change or IPCC is an international body that assesses and reports about climate change. Specifically, it reports on the current knowledge about climate change and its possible impacts. read more on IPCC


Iron (Fe) is the 26th element on the periodic table and has been used by humans for over 5000 years.[53] It is one of the most abundant metals on Earth, making up 5.6% of the Earth's crust and nearly all of the Earth's core. read more on Iron


The term isobar is ambiguous read more on Isobar

Isobar (nuclear)

A nuclear isobar are two nuclear species where the total number of protons and neutrons is the same for each nucleus, but the number of protons and neutrons making up that total are different. read more on Isobar (nuclear)

Isobar (pressure)

An isobar in the context of thermodynamics refers to any process in which the system remains at a constant (unchanging) pressure throughout it. read more on Isobar (pressure)


The term isomer is ambiguous read more on Isomer


Isothermal refers to a process in which a system changes - be it the pressure, volume or contents - without the temperature changing. read more on Isothermal


Nuclear species with the same number of neutrons in the nucleus but a different number of protons (which makes it a different element) are called isotones of that element. read more on Isotone


Isotopes are atoms of the same element that have different numbers of neutrons, resulting in a different atomic mass.[54] read more on Isotope

Isotope separation

Isotope separation is a process of element enrichment by the physical separation of isotopes in a substance. read more on Isotope separation

Jet-bore mining method

The jet-bore mining method is an underground method used in the mining of uranium. A very cold brine is circulated under ground in order to freeze the ore and surrounding rocks in order to provide safe operation. read more on Jet-bore mining method


A joule is the SI base unit for energy. It is equal to .[55] read more on Joule

Kaplan turbine

A Kaplan turbine is a type of turbine used in hydroelectric plants. They are a type of "propeller" turbine that has an axial flow, taking in water parallel to its rotational axis. read more on Kaplan turbine


Kelvin is the SI base unit of temperature.[56] It is given the symbol . read more on Kelvin


Kerogen is a waxy, insoluble organic substance that forms when organic shale is buried under several layers of sediment and is heated. If this kerogen is continually heated, it leads to the slow release of fossil fuels such as oil and natural gas, and also the non-fuel carbon compound graphite. read more on Kerogen


Kerosene is a flammable liquid mixture of chemicals that are produced in the distillation of crude oil. To produce kerosene, crude oil is distilled in a distillation tower in a process similar to that used to produce diesel and gasoline. read more on Kerosene

Kerosene lantern

Kerosene lanterns are simply lanterns that burn kerosene by pulling it up through a wick within the lantern, creating light. Worldwide, an estimated 1.6 billion people use kerosene or other similar oil as their primary source of fuel for lighting. read more on Kerosene lantern


A kilogram is the SI unit of mass and one of the 7 base units. It is the only SI unit with a prefix. read more on Kilogram

Kilometers per hour

Kilometers per hour is a unit of measurement using length in kilometers and time in hours, and thus it acts as a derived unit for both speed and velocity. read more on Kilometers per hour

Kilometers per liter

Kilometers per liter is a measurement of fuel economy. It is rarely used, because liters per hundred kilometers has been adopted as the standard in much of the world. read more on Kilometers per liter

Kinetic energy

Kinetic energy is the energy of motion. This can be the motion of large objects (macroscopic kinetic energy), or the movement of small atoms and molecules (microscopic kinetic energy). read more on Kinetic energy

Kinetic energy recovery system

Kinetic energy recovery systems (KERS) are systems used in Formula 1 vehicles in order to recover kinetic energy for future use. read more on Kinetic energy recovery system


A knot is a derived unit of speed or velocity that uses length in nautical miles and time in hours.[57] read more on Knot

La Nina

La Niña is a massive ocean-atmosphere phenomenon that has dramatic effects on global weather. read more on La Nina

Lake Nyos

Lake Nyos is a lake in Cameroon which released a lethal cloud of gas on August 21st, 1986, killing 1800 people and 3500 livestock. A cloud of carbon dioxide elevated out from the lake and proceeded to roll into the valley below at 100 km/hr.[2] The cloud grew up to 100 meters in height, and spread over 25 kilometers before finally being dispersed into the atmosphere, leaving people and livestock dead in its wake. read more on Lake Nyos

Land vs sea ice

Land ice and sea ice comprise the majority of the polar regions on Earth. This article is aimed to distinguish between these two types of ice. read more on Land vs sea ice

Law of conservation of charge

Law of conservation of charge says that the net charge of an isolated system will always remain constant. read more on Law of conservation of charge

Law of conservation of energy

The law of conservation of energy states that energy can neither be created nor destroyed - only converted from one form of energy to another. read more on Law of conservation of energy

Layers of the atmosphere

Earth's atmosphere is a mixture of gases that cover the planet's surface and are held there by gravity. read more on Layers of the atmosphere


Lead, written shorthand as Pb, is the 82nd element on the periodic table. It is a metallic element with a very high density. read more on Lead


Leapfrogging is the ability of a developing or less developed country to essentially "skip" less efficient and higher carbon-intensive technologies during the course of their development. The decreasing cost of high efficiency, low-carbon technologies makes leapfrogging increasingly possible and allows for development and environmental awareness to coincide. read more on Leapfrogging

LED light bulb

LED bulbs consist of light emitting diodes designed and manufactured as lighting fixtures (see Figure 1). These devices use a semiconductor to turn electricity into light. read more on LED light bulb

Legal economics

Legal economics is the study and practice of making laws that are economically efficient. read more on Legal economics

Lenz's law

Lenz's law is an important concept in electromagnetism, which states that when a voltage is created by a change in magnetic flux, the induced voltage must create a current whose magnetic field is in opposition to the change which produces it.[58] read more on Lenz's law

Levelized cost of energy

The levelized cost of energy or LCOE is similar to the concept of the payback for energy systems. Instead of measuring how much is needed to recoup the initial investment the LCOE determines how much money must be made per unit of electricity (kWh, MWh etc. or even other type of energy like home heating) to recoup the lifetime costs of the system. This includes the initial capital investment, maintenance costs, the cost of fuel for the system (if any), any operational costs and the discount rate. read more on Levelized cost of energy


A lever is a type of simple machine, which creates a mechanical advantage to perform tasks by changing the magnitude and/or direction of forces. read more on Lever

Life cycle

Life cycle or product life cycle is the cycle through which every product goes through from "cradle to grave". This includes every step in its life including the extraction of resources to the disposal of the item itself. read more on Life cycle

Life cycle assessment

A life cycle assessment or life cycle analysis is a technique that is used to assess the potential environmental impacts that are associated with a product, process, or service. Generally this analysis observes a certain product from "cradle to grave", or its entire life cycle including extraction, processing, use, and disposal. read more on Life cycle assessment

Life expectancy

Life expectancy is the average number of years a hypothetical person in a specific group of people, who would be subject to the mortality rates of a specific period, could be expected to live. It is expressed in years.[59] read more on Life expectancy

Life-cycle cost

The life-cycle cost (LCC) of a project it the total amount of all costs incurred by the project from its initial design stages to its decommissioning. read more on Life-cycle cost


Light is technically any form of radiant energy, but is almost always taken to mean visible radiant energy. read more on Light

Light bulb

A light bulb is a device that converts electrical energy into light. read more on Light bulb

Light emitting diode

Light emitting diodes or LEDs are electronic components that exploit the movement of electrons in diodes to produce light. These LEDs have numerous advantages over other forms of illumination, including high efficiency and a long lifespan. read more on Light emitting diode

Light water

Light water is simply ordinary water that does not contain large amounts of deuterium, making it distinct from heavy water.[2] Although this water does contain small numbers of heavy water molecules, it isn't enough to make any significant changes in its properties. read more on Light water

Light year

A light year (l.y.) is a unit of distance, given by the distance light will travel in one year. read more on Light year


Lighting is a general term that refers to the process of illuminating a home, workplace, or street to make it livable through different technologies such as light bulbs, kerosene lanterns, charcoal burners, or through daylighting. read more on Lighting


Lignite or Brown coal is a brown fossil fuel and the lowest rank of coal. It is a softer coal with a high moisture content and contains the greatest amount of compounds other than carbon - such as sulfur and mercury. read more on Lignite


Likelihood is a probabilistic estimate of the occurrence of a single event or of an outcome. read more on Likelihood

Linear no-threshold model

The Linear no-threshold model (LNT) is a way of predicting the maximum biological risk from ionizing radiation. read more on Linear no-threshold model

Liquefied natural gas

Liquefied natural gas or LNG is a colorless and odorless liquid that contains 85-95% methane with trace amounts of ethane, propane, butane and nitrogen. read more on Liquefied natural gas

Liquefied natural gas industry

The liquified natural gas industry refers to the production, trade, and consumption of natural gas. While oil has been traded globally for decades, natural gas has tended to remain within its continent of origin. read more on Liquefied natural gas industry

Liquefied petroleum gas

Liquefied petroleum gas or LPG is a type of hydrocarbon gas that is obtained by refining crude oil or processing natural gas. This gas is composed of either propane and butane by themselves or as a mixture of the two. read more on Liquefied petroleum gas


Liquids, along with gases and solids, are one of the states of matter. read more on Liquid


The liter (also spelled litre) is a unit of volume in the metric system of units. One liter is equal to 1,000 cm3. read more on Liter

Liters per hundred kilometers

Liters per hundred kilometers, or L/100km, is a measurement of fuel consumption and is used to determine fuel economy. read more on Liters per hundred kilometers


The litre (also spelled liter) is a unit of volume in the metric system of units. One liter is equal to 1,000 cm3. read more on Litre

LNG carrier

An LNG carrier is a ship that is designed for the transport of liquefied natural gas in its chilled tanks. Worldwide there are around 359 of these advanced, specialized vessels that are used specifically for the transport of liquefied natural gas. read more on LNG carrier


A loan is when one entity (a bank, person, business etc.) lends money to another for repayment in the future. Loans can come in different forms depending on the term of the loan, the interest rate charged, the amount and other parameters. read more on Loan

Logarithmic scale

A logarithmic scale is a nonlinear scale often used when analyzing a large range of quantities. Instead of increasing in equal increments, each interval is increased by a factor of the base of the logarithm. Typically, a base ten and base e scale are used. read more on Logarithmic scale

Long tail-pipe problem

Long tail-pipe problem is an argument against the "zero emissions" claim of electric vehicles (EVs), which says that although there are no emissions from the actual operation of an all-electric vehicle, there is associated emissions from the electricity they are using. read more on Long tail-pipe problem

Long ton

A long ton is a unit of mass in the Imperial system equal to 2240 pounds. read more on Long ton

Lubricating oil

Lubricating oil, sometimes simply called lubricant/lube, is a class of oils used to reduce the friction, heat, and wear between mechanical components that are in contact with each other. Lubricating oil is used in motorized vehicles, where it is known specifically as motor oil and transmission fluid. read more on Lubricating oil


The lumen (lm) is the SI derived unit for light flux, which is the amount of light being received by a surface. read more on Lumen

Luminous intensity

Luminous intensity is a measure of the radiant power emitted by an object in a given direction, and is dependent on the wavelength of light being emitted. It is weighted to the sensitivity of the human eye, by what is called the "standard luminosity function". read more on Luminous intensity


A magnet is a type of material that produces a magnetic field. The magnetic field produced is invisible, but its effects are felt very easily when put in contact with other magnetic materials. read more on Magnet

Magnetic field

Magnetic fields are produced by changing electric fields, usually moving charges such as electrons, often the form of a macroscopic current (like the current in a wire) or a microscopic current (such as in an atomic orbit).[60] In one of the most beautiful examples of symmetry in physics, changing magnetic fields create electric fields. read more on Magnetic field

Magnetic flux

Magnetic flux is the amount of magnetic field perpendicular to a surface, passing through that surface. Changing magnetic flux creates an electromotive force, which will often make electric current flow through a wire. read more on Magnetic flux

Marginal cost

Marginal cost is the cost of adding one additional unit of output or the cost of increasing an activity. read more on Marginal cost


A market is where buyers and sellers exchange goods and services. read more on Market

Market economy

A market economy or free market is a market that is unrestricted by regulation and the economy is therefore subject to the market forces. read more on Market economy

Market failure

Markets exist to help determine the best price and quantity for goods and services. Unfortunately, markets often miss the perfect price and quantity because of externalities, when this gets bad enough this leads to a market failure. read more on Market failure

Market force

A market force is a factor that has some ability to affect change in a market. Market forces determine the price and quantity of a good or service in a market. read more on Market force

Market power

A firm has market power when it is able to affect the supply or demand of a market to force a change in the price. The firm that has the market power has the most influence over the market. read more on Market power


Mass is a measure of how much matter is contained within an object. Its SI unit is the kilogram. read more on Mass

Mass number

The mass number, [math]\left(A\right)[/math] (also called nucleon number), refers to the total number of protons and neutrons in the nucleus of an atom read more on Mass number

Mass-energy equivalence

Mass-energy equivalence is the famous concept in physics represented mathematically by [math]E=mc^2[/math], which states that mass and energy are one and the same. read more on Mass-energy equivalence


Matter can be defined as anything that has mass and occupies space. In its natural form, matter exists as a solid, liquid, gas, or plasma. read more on Matter

McKelvey box

A McKelvey diagram or McKelvey box is a diagram that helps to explore the distinction between resources and reserves and the differences that can exist within these two broad categories. read more on McKelvey box

Mechanical advantage

Mechanical advantage is a measure of the ratio of output force to input force in a system, used to analyze the forces in simple machines like levers and pulleys. Despite changing the forces that are applied the conservation of energy is still true and the output energy is still equal to the input energy. read more on Mechanical advantage

Mechanical energy

Mechanical energy is the sum of kinetic energy and potential energy within a system. For systems that only have conservative forces (no non-conservative forces, like friction, to cause energy to be turned into thermal energy), the mechanical energy stays the same. read more on Mechanical energy

Mechanical equivalent of heat

Mechanical equivalent of heat is the notion that mechanical energy can be converted into heat, and vice versa. That is, one can change the internal energy of a system by either doing work to the system, or adding heat to the system. This concept is fundamental to thermodynamics which applies the ideas of heat and work in order to create useful systems such as engines, power plants, and refrigerators. read more on Mechanical equivalent of heat

Mechanical power

Mechanical power refers to the rate at which work can be done. It is a power output, as opposed to a power input (how fast the engine can do work, rather than how fast it uses fuel). read more on Mechanical power

Megawatts electric

Megawatts electric or MWe is one of the two values assigned to a power plant, the other being megawatts thermal or MWt. Megawatts electric refers to the electricity output capability of the plant, and megawatts thermal refers to the input energy required. read more on Megawatts electric

Megawatts thermal

Most power plants are heat engines, and therefore can't turn 100% of their input energy into electricity. Because of this, there are two values assigned to a powerplant: megawatts electric (MWe), and megawatts thermal (MWt). The former refers to the electricity output capability of the plant, and the latter refers to the input energy required. read more on Megawatts thermal

Melting point

Melting point is the temperature that a solid will change phase into a liquid. read more on Melting point


Mercaptan, also known as methanethiol is a foul-smelling gas that is added to natural gas - which is colourless and odourless - as an odorant to make it easier to detect. read more on Mercaptan


The term mercury is ambiguous and may refer to:

read more on Mercury

Mercury (element)

Mercury (Hg) is the 80th element on the periodic table, is classified as a metal, and is liquid at room temperature. read more on Mercury (element)

Mercury (pollutant)

Mercury (Hg) as a pollutant is a major problem in pollution from energy. It is released from both humans and natural sources, with the burning of coal believed to be a major contributor. read more on Mercury (pollutant)


Metals are a class of elements characterized by a tendency to give up electrons and by good thermal and electrical conductivity. read more on Metal


A meter is the SI unit of distance. The meter is defined as the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. read more on Meter

Meters per second

Meters per second is a derived unit for speed or velocity, which are measured by taking the distance traveled during some duration and dividing that length by the time. read more on Meters per second


Methane is an alkane with the chemical formula CH4. As a hydrocarbon, it can undergo hydrocarbon combustion which gives off heat. Methane is the main hydrocarbon component of natural gas, which is a type of fossil fuel. read more on Methane


Methanol is the simplest alcohol, and is also known as methyl alcohol. It is colourless, highly flammable, and at typical temperatures and pressures is a liquid. read more on Methanol

Metric ton

The metric ton or tonne is a unit of mass, and it is defined as 1,000 kilograms. read more on Metric ton

Micro-wind turbine

Micro-wind turbines are used in micro-wind generation and are much smaller in scale than those used in conventional wind generation and therefore more suitable for residential energy production. read more on Micro-wind turbine

Midstream oil and gas industry

Midstream industry is the portion of the oil and natural gas industry that is responsible for the processing, storage, and transportation of products such as crude oil, natural gas, natural gas liquids, and sulfur. read more on Midstream oil and gas industry

Milankovitch cycle

Milankovitch cycles are three ways the Earth's orbit around the Sun changes over the course of tens of thousands of years. Each of the three, eccentricity, axial tilt and precession all influence how much solar energy hits the Earth. This change has been a major factor controlling periods of glaciation and seasons.[61] read more on Milankovitch cycle


A mile (mi) is a unit of distance equal to 1.609344 kilometers. read more on Mile

Miles per gallon

Miles per gallon is a fuel efficiency rating determined by how far a car can travel on a gallon of gasoline or diesel. read more on Miles per gallon

Miles per gallon gasoline equivalent

Miles per gallon gasoline equivalent refers to the fuel efficiency of electric vehicles that compares how far a car can go with how much energy is in a gallon of gasoline. read more on Miles per gallon gasoline equivalent

Miles per hour

Both speed and velocity are measured by taking the distance traveled during some duration, and dividing that length by a time. Using lengths in miles and time in hours, leads to the derived unit of miles per hour. read more on Miles per hour

Mill race

The mill race is a channel that carries water from its source - a hydroelectric dam or river - to the site of a mill using a waterwheel. This race directs and diverts the water to the waterwheel - either underneath it in the case of an undershot waterwheel or midway up it in the case of a breastshot waterwheel. read more on Mill race

Mine mouth

A mine mouth electric plant is a coal burning electricity generating plant that is built close to a coal mine.[62] In these plants, coal is excavated from the dig site, placed on a conveyor belt, and run directly into the plant where the coal will be burned. read more on Mine mouth

Mixed economy

A mixed market or, mixed economy is one that incorporates the principles of a capitalist free market to allow for private economic freedoms but attempts to compensate for its negative effects to ensure or improve the social good. read more on Mixed economy


Moderation is the process of slowing neutrons in a nuclear reactor so that they can easily promote fission of a nucleus.[2] The material that causes this slowing down of the neutrons is known as a moderator. read more on Moderation

Modes of climate variability

Climate can be defined as the long-term trends of the weather. While both are fundamental to the atmosphere, they are affected by cooperation between the atmosphere and the ocean, the biosphere, the land surface, and the cryosphere. read more on Modes of climate variability

Moisture intrusion (building envelope)

Moisture intrusion refers to water getting into a building and is one the most significant factor affecting the durability of a building envelope, which is its ability to continue to perform its functions over time. read more on Moisture intrusion (building envelope)

Molar mass

Molar mass (M) is a physical property, defined as the mass of a given element or molecule per mole of that substance. Since a mole is defined as the amount of a substance and substances have different masses, each element or molecule will have a different molar mass. read more on Molar mass


A mole, abbreviated as mol, is a measurement of amount used by scientists. One mole is equal to 6.022x1023 units. read more on Mole

Molecular hydrogen

Molecular hydrogen, sometimes called dihydrogen, is a diatomic molecule that is composed of two hydrogen atoms held together by a covalent bond with the chemical formula H2. read more on Molecular hydrogen

Molecular oxygen

Molecular oxygen (O2) is a diatomic molecule that is composed of two oxygen atoms held together by a covalent bond. Molecular oxygen is essential for life, as it is used for respiration by many organisms. It's also essential for fossil fuel combustion. read more on Molecular oxygen


A molecule is a specific collection of atoms. read more on Molecule

Molten salt reactor

Molten salt reactors (MSRs) are a Generation IV nuclear reactor that use molten salts (high temperature liquid salts) as their nuclear fuel in place of the conventional solid fuels used in the world's current reactors. The use of fluids allows for it to act both as their fuel (producing the heat) and coolant (transferring the heat). read more on Molten salt reactor

Molten salt reactor experiment

The Molten Salt Reactor Experiment or MSRE was an unimaginatively named molten salt reactor design that was constructed by Oak Ridge National Laboratories (ORNL). read more on Molten salt reactor experiment


Momentum is a property of an object's motion. When a push or a pull (a force) acts on an object and changes its motion, the quantity that gets changed is momentum. read more on Momentum


A firm that is the only supplier or seller in a market is said to have a monopoly. The lack of competition means the firm can charge a much higher price for goods and services because they don't have any competition. read more on Monopoly


A monopsony represents a situation where a market has only one buyer. This lone buyer is able to reduce the price of a good or service due to the lack of competition. Similar to a monopoly, a monopsony can affect the price of a specific good or service in a market but unlike a monopoly the monopsony affects price from the demand side or buyers side of the market. read more on Monopsony


A monsoon is a seasonal reversal in both the prevailing winds and associated precipitation over a region, caused by a difference in heating between a large land mass and the adjacent ocean. read more on Monsoon

Motor vehicle

Energy Education has a number of pages to help one understand the energy science behind their motor vehicles. This page provides a starting point for anyone keen on learning more about cars to pick and choose what interests them. read more on Motor vehicle

Mountain pine beetle

The mountain pine beetle is an insect that has long lived in North American forests.[63] Once a vital part of the ecosystem, the mountain pine beetle would feed on the bark of dying trees and then die out in the winter. read more on Mountain pine beetle


MSRP stands for "manufacturer's suggested retail price". This price is a suggestion of how much the manufacturer thinks that a certain product, such as a car or a cell phone, is worth. read more on MSRP


A multimeter is a device which measures current, resistance, and voltage (provided it's attached to an electrical circuit properly). It comes in analog and digital forms, but both function the same basic way. read more on Multimeter

N11 countries

N11 countries or the Next 11 countries refers to a group of eleven countries - specifically Bangladesh, Egypt, Indonesia, Iran, Mexico, Nigeria, Pakistan, the Philippines, Turkey, South Korea, and Vietnam - which have emerging markets that could potentially become some of the worlds largest economies. read more on N11 countries


Naphtha is a term used to refer to a group of volatile, flammable mixtures of liquid hydrocarbons that are used mainly as solvents, diluents, or raw materials for gasoline conversion. read more on Naphtha

Natural carbon cycle

The natural carbon cycle is the flow of carbon naturally throughout across the globe in various forms, such as carbon dioxide or methane. read more on Natural carbon cycle

Natural gas

Natural gas is a colourless, odorless gas that is easy to burn (see flaring in Figure 1) and typically consists mostly (90% or more) of methane. read more on Natural gas

Natural gas formation

Natural gas is a fossil fuel that is composed mainly of methane - composed itself of carbon and hydrogen - and is thus known as a hydrocarbon.[2] The formation of natural gas (which is a gas) is essentially the same as the formation of oil (a liquid) and thus takes a significant amount of time with natural gas beginning to form millions of years ago. read more on Natural gas formation

Natural gas power plant

Natural gas power plants are a type of power plant that use natural gas as their fuel in order to generate electricity. read more on Natural gas power plant

Natural gas refueling station

Natural gas refuelling stations are places to refuel Natural gas vehicles (NGVs) that look similar to those for diesel or gasoline.[64] The refueling process of natural gas depends on whether compressed natural gas (CNG) or liquefied natural gas (LNG) is being used. read more on Natural gas refueling station

Natural gas reserve

Natural gas reserves refer to large deposits of natural gas which, based on geological surveys and engineering studies, are thought to exist to a very high degree of certainty. In addition to the knowledge of their existence, these reserves are also accessible and natural can be produced from them economically. read more on Natural gas reserve

Natural gas vehicle

Natural gas vehicles or NGVs are an alternative fuel vehicle that use natural gas as fuel rather than the typical gasoline or diesel. read more on Natural gas vehicle

Natural gas vehicle fuel storage

Natural gas vehicle fuel storage is a challenge of natural gas vehicles since the vehicles can't keep natural gas at ambient pressure and temperature. read more on Natural gas vehicle fuel storage

Natural vs anthropogenic climate change

Anthropogenic climate change is defined by the human impact on Earth's climate while natural climate change are the natural climate cycles that have been and continue to occur throughout Earth's history. read more on Natural vs anthropogenic climate change

Negative climate feedback

Negative climate feedback is any process where climate feedback decreases the severity of some initial change. Some initial change causes a secondary change that reduces the effect of the initial change. This feedback keeps the climate system stable.[2] It is generally discussed in the context of climate change and is one particular type of negative feedback. read more on Negative climate feedback

Negative externality

Economists use the term externality to describe any time the price determined by a market doesn't reflect the true cost of an action. A negative externality is a bad consequence that isn't taken into account, like the harm that comes from pollution. read more on Negative externality

Negative feedback

Negative feedback is a process that minimizes or reduces some initial effect, generally some disturbance causes some secondary effect that in turn minimizes the magnitude of the initial disturbance. This causes some initial change to grow smaller, keeping the system from moving out of its equilibrium state. read more on Negative feedback

Neutral line

The neutral line refers to the part of the distribution system that returns the power that left the transmission lines through a hot line or phase line to do work on an electrical load. Neutral lines are at zero potential relative to the ground, meaning that ideally, they do not pose a shock hazard (but good safety practice is always a good idea). read more on Neutral line


Neutrons are neutrally charged particles that are found in the nucleus of atoms, along with the positively charged protons. read more on Neutron

Neutron moderator

Neutron moderators are a type of material in a nuclear reactor that work to slow down the fast neutrons produced by fission to make them more effective in the fission chain reaction. This slowing or moderation of the neutrons allows them to be more easily absorbed by fissile nuclei, creating more fission events. read more on Neutron moderator

Neutron number

The neutron number, written as N, refers to the number of neutrons in the nucleus of an atom.[65] read more on Neutron number


A newton is the SI unit of force. read more on Newton

Newton meter

The newton meter [math] \left( N m \right)[/math] is a measurement of torque. One newton meter is equal to approximately 0.738 pound-feet. read more on Newton meter


Nickel is the 28th element on the periodic table. read more on Nickel


Nitrogen (N) is the 7th element on the periodic table. Nitrogen is the fifth most abundant element in the universe, and it is also fairly common on Earth. read more on Nitrogen

Nitrogen oxide

Nitrogen oxides or NOx are a family of poisonous, highly reactive gases that form when fuel is burned at high temperatures. NOx gases are generally brown in colour and are emitted by vehicles as well as industrial sources such as power plants, industrial boilers, cement kilns, and turbines. read more on Nitrogen oxide

Non-conservative force

A non-conservative force is a force that turns some macroscopic motion (or mechanical energy) into microscopic motion (thermal energy). read more on Non-conservative force

Non-dispatchable source of electricity

A non-dispatchable source of electricity is a generator of electrical energy that cannot be turned on or off in order to meet societies fluctuating electricity needs. It is the opposite of dispatchable sources of electricity which are very flexible, being able to change their output fairly quickly in order to meet electricity demands. read more on Non-dispatchable source of electricity


Nonane is an alkane with the chemical formula C9H20. As a hydrocarbon, it can undergo hydrocarbon combustion and can be burned as a fuel. read more on Nonane


Nonlinearity is a property that is used to describe a relationship that is not linear - essentially it is a term used to describe a relationship that cannot be plotted as a straight line on a graph, but rather has a curved or angular shape. The term however usually implies that the relationship will yield surprising results. read more on Nonlinearity

Normal force

The normal force is an everyday force that is felt every time two surfaces push against each other. For example, when a book is placed on a table, the normal force keeps the book from falling through the table. read more on Normal force

North Atlantic Oscillation

North Atlantic Oscillation (NAO) is a climate pattern that has a strong influence over North America, Greenland, and Europe.[2] The NAO is a natural form of climate variability, explaining short and long phases in climate caused by natural, large scale features. Other natural patterns of climate variability include the Northern Annular Mode, Pacific Decadal Oscillation, and the Atlantic Multidecadal Oscillation. The NAO forms a permanent low pressure system which exists over Greenland and Iceland, with a permanent high-pressure system existing over a group of islands roughly 1400 km west of Portugal, known as the Azores.[21] read more on North Atlantic Oscillation

Northern Annular Mode

Northern Annular Mode (NAM) also known as Arctic Oscillation (AO) or Northern Hemisphere Annular Mode, is a natural form of climate variability[38], being closely associated with the North Atlantic Oscillation (NAO), which has similar structure over the Atlantic but when looked at from above, the shape is more annular. This makes the pattern regionally symmetric.[66] The NAM is a climate pattern which is described by winds circulating counterclockwise around the Arctic at approximately 55°N latitude.[38] read more on Northern Annular Mode

Not in my back yard syndrome

NIMBY (also NIMBYism, NIMBY syndrome) is an acronym for "Not In My Back Yard". read more on Not in my back yard syndrome

Not in my term of office

Not in my term of office, or Not in my election year occasionally referred to as NIMTOO and NIMEY, are an acronyms referring to the habit of elected officials for postponing projects that may be unpopular like a new power plant. read more on Not in my term of office

Nuclear chain reaction

Nuclear chain reactions are reactions where nuclear energy is obtained, generally through nuclear fission. These chain reactions are what provide nuclear power plants with the energy that is then turned into electricity for use by people. read more on Nuclear chain reaction

Nuclear fission

Nuclear fission is the process of splitting apart nuclei (usually large nuclei). When large nuclei, such as uranium-235, fissions, energy is released. read more on Nuclear fission

Nuclear fuel

Nuclear fuel is the fuel that is used in a nuclear reactor to sustain a nuclear chain reaction. These fuels are fissile, and the most common nuclear fuels are uranium-235 and plutonium-239 which are radioactive metals. read more on Nuclear fuel

Nuclear fuel cycle

The Nuclear fuel cycle is the series of industrial processes that describe uranium throughout its life cycle; from mining to processing to generating electricity and finally to its reprocessing and waste. read more on Nuclear fuel cycle

Nuclear fusion

Nuclear fusion is a type of nuclear reaction where two light nuclei collide together to form a single, heavier nucleus. read more on Nuclear fusion

Nuclear fusion in the Sun

The energy from the Sun - both heat and light energy - originates from a nuclear fusion process that is occurring inside the core of the Sun. The specific type of fusion that occurs inside of the Sun is known as proton-proton fusion. read more on Nuclear fusion in the Sun

Nuclear isomer

Nuclear isomers are nuclear species with the same number of neutrons and the same number of protons, but different binding energy per nucleon are called isomers of that element. read more on Nuclear isomer

Nuclear power

Nuclear power is the electricity generated through the use of nuclear fission. Nuclear power supplies the world with around 11% of its total electricity,[67] with operation in 31 countries. read more on Nuclear power

Nuclear power plant

Nuclear power plants are a type of power plant that use the process of nuclear fission in order to generate electricity. They do this by using nuclear reactors in combination with the Rankine cycle, where the heat generated by the reactor converts water into steam, which spins a turbine and a generator. read more on Nuclear power plant

Nuclear reactor

A nuclear reactor is a system used to initiate and contain a nuclear chain reaction, and they have many useful applications. These nuclear reactions produce thermal energy through either nuclear fission (in practice) or nuclear fusion (in development). read more on Nuclear reactor

Nuclear species

A nuclide, which is also called a nuclear species, is a unique configuration of nucleons (which is the collective term for protons and neutrons) inside of a nucleus.This term allows nuclear scientists to distinguish between nuclei that differ in any way; number of protons, neutrons, or energy configuration of either. read more on Nuclear species

Nuclear waste

The term nuclear waste is often used to refer to spent nuclear fuel. This term is general, as there are many different types of nuclear waste, but refers to any radioactive waste substance that is produced from industrial processes, including nuclear power plants. read more on Nuclear waste


Nucleon is the collective term for protons and neutrons. Nucleons are the particles found in the nucleus of atoms. read more on Nucleon


The nucleus is the central, highly dense, component of an atom and is composed of protons and neutrons (collectively called nucleons). read more on Nucleus

Ocean acidification

Ocean acidification is a major climate change problem, concerning the change in acidic levels of the ocean. Carbon dioxide emissions have been substantially increasing since the start of the industrial revolution. The oceans on Earth absorb approximately 25% of the carbon dioxide that is released into the atmosphere every year.[68] Hence, as atmospheric CO2 levels increase, so do the levels in the ocean. The CO2 absorbed by the ocean is changing the chemistry of the seawater, which is a process called ocean acidification. read more on Ocean acidification

Ocean heat

Ocean heat is the energy associated with the change in average ocean surface and bulk temperatures as a result of both natural and human activities. This heating comes as a result of increased greenhouse gas levels in the atmosphere, which are known to be attributed to human emissions. read more on Ocean heat

Ocean thermal energy conversion

Ocean thermal energy conversion or simply OTEC is the process of using the ocean itself as a solar collector. This technology is still highly theoretical, and utilizes the slight temperature gradient between the warm surface of the ocean and the cooler water deeper down. read more on Ocean thermal energy conversion


Octane is a hydrocarbon that can be burned as a fuel. It's chemical formula is C8H18, and it is a colourless liquid at room temperature with a characteristic "gasoline" odour. read more on Octane

Octane rating

Octane rating, also known as octane number is a measurement of the quality or performance of gasoline. The higher the number, the better the fuel burns within the engine of a vehicle. read more on Octane rating


Odorants are chemical additives that are mixed in with natural gas during the odorization process to add an artificial smell to the gas. These odorants are added as a safety precaution, as natural gas in its pure state is completely odourless. read more on Odorant


OECD stands for the Organization for Economic Co-operation and Development. This is an organization concerned with the day to day good of people in countries around the world. read more on OECD

Offshore drilling

Offshore drilling is the process of extracting petroleum from reserves located beneath the Earth's oceans instead of reserves located on the mainland. read more on Offshore drilling

Offshore wind turbine

Offshore wind turbines operate by transforming the kinetic energy in wind over water into rotational kinetic energy which is used to generate electricity. read more on Offshore wind turbine


The Ohm (Ω) is a unit of electrical resistance, useful for measuring the resistance of resistors, conductors, or even electrical insulators. read more on Ohm

Ohm's law

Ohm's law is a mathematical expression that describes the relation between potential difference (voltage), current, and resistance. read more on Ohm's law


In general, oil is a liquid that is made up of organic molecules. However, the world oil in the context of the energy sector is the liquid fossil fuel that is extracted from the ground. Roughly 1/3 of the world's primary energy comes from this primary fuel. Chemically, oil is composed mainly out of carbon and hydrogen with other trace elements. read more on Oil

Oil and gas reservoir

An oil and gas reservoir is a formation of rock in which oil and natural gas has accumulated within. The oil and gas collect in the small, connected pore spaces of rock and are sealed below ground surface by an impermeable layer of rock. read more on Oil and gas reservoir

Oil and gas traps

Oil and gas traps, sometimes referred to as petroleum traps are below ground traps where a permeable reservoir rock is covered by some low permeability cap rock. This combination of rock can take several forms, but they all prevent the upward migration of oil and natural gas up through the reservoir rock. read more on Oil and gas traps

Oil crisis of the 1970s

The oil crisis of the 1970s was brought about by two specific events occurring in the Middle-east, the Yom-Kippur War of 1973 and the Iranian Revolution of 1979. Both events resulted in disruptions of oil supplies from the region which created difficulties for the nations that relied on energy exports from the region. read more on Oil crisis of the 1970s

Oil formation

Oil or petroleum is a readily combustable fossil fuel that is composed mainly of carbon and hydrogen, and is thus known as a hydrocarbon.[2] The formation of oil takes a significant amount of time with oil beginning to form millions of years ago. read more on Oil formation

Oil refinery

An oil refinery is an industrial plant where crude oil is separated into a variety of different, useful substances through a variety of chemical separation steps.[2] After extraction from the ground, processing at oil refineries is the second step in the production of different petroleum products. read more on Oil refinery

Oil sands

Oil sands are a mixture of sand, clay, water, and bitumen that occur naturally. Bitumen is the fossil fuel component of this sand, and it is a very heavy oil that must be treated and upgraded before it can be used to produce useful fuels such as gasoline. read more on Oil sands

Oil sands extraction

Oil sands extraction is the process of removing oil sand from the ground and extracting bitumen from it. This bitumen is later upgraded into a synthetic crude oil that can be separated into usable fractions through fractional distillation. read more on Oil sands extraction

Oil sands land reclamation

Reclamation is the process of attempting to return previously used land from oil sands mining or tailings storage back to its original, natural state. The concept behind reclamation is the goal of "returning land back to nature". read more on Oil sands land reclamation

Oil sands surface mining

Surface mining is a technique used to obtain bitumen from oil sands where the oil sands deposits are located fairly close to the surface. If the reserves are shallow enough, earth moving equipment can dig out oil sand for processing. read more on Oil sands surface mining

Oil sands tailings ponds

Tailings ponds are settling ponds that contain the waste byproduct of oil sands extraction and upgrading. They are a mix of water, sand, silt, clay, unrecovered hydrocarbons, and other contaminants. read more on Oil sands tailings ponds

Oil well

An oil well is a hole dug into the Earth that serves the purpose of bringing oil or other hydrocarbons - such as natural gas - to the surface. read more on Oil well


An oligopoly is similar to a monopoly in that there is a small number of firms which have market power meaning that they can influence the price in the market and there is almost no competition. read more on Oligopoly


An oligopsony is a situation when there are only a small number of buyers in a market. This means that a limited number of people have market power and are able to lower the price they pay for a good or service due to the lack of competition. Similar to a monopsony an oligopsony can affect the price of a specific good or service in a market but unlike an oligopoly the oligopsony affects price from the demand side or buyers side of the market. read more on Oligopsony

On-line refueling

On-line refueling is a technique used in certain nuclear reactors, which allows nuclear fuel to be removed or added during operation. This is important, since most nuclear power plants like the common pressurized water reactor have to shutdown in order to refuel. read more on On-line refueling

OPEC (brief history)

The Organization of Petroleum Exporting Countries or OPEC an organization that was created at a conference in Baghdad, Iraq on September 10th-14th, 1960. The founding members which include Iran, Iraq, Kuwait, Saudi Arabia and Venezuela agreed to create an organization that could bring some degree of stability to the world oil market. read more on OPEC (brief history)

OPEC (cartel)

The governments of the OPEC countries agreed to coordinate with petroleum firms (both state owned and private) in order to manipulate the worldwide oil supply and therefore the price of oil. read more on OPEC (cartel)

Operational cost

The operational costs of a firm are the costs a firm incurs during its everyday business, it does not include the capital costs of building factories but does include costs such as labor, materials, monthly lease payments, transport costs etc. read more on Operational cost

Opportunity cost

Resources are assigned a value based on the cost of using an input to do one thing instead of another, this is called the opportunity cost.[69] The opportunity cost of one action compared with another is determined by comparing the potential benefits of each action. read more on Opportunity cost


An orbital in an atom refers to the regions within the atom where electrons have the highest probability of being found, since electrons are dispersed through a large volume of the atom and not concentrated in one area like the neutrons and protons. read more on Orbital

Organic molecule

Organic molecules are molecules which are made of carbon and other elements. read more on Organic molecule

Organic Rankine cycle

The organic Rankine cycle is an alternate form of the Rankine cycle, most often used when the high temperatures required to produce steam are not available. read more on Organic Rankine cycle

Organization of petroleum exporting countries

The Organization of Petroleum Exporting Countries or OPEC an organization of countries that contain a significant fraction of the world's oil reserves. read more on Organization of petroleum exporting countries

Overnight cost of capital

the cost of building a plant overnight would be or the overnight cost of capital. read more on Overnight cost of capital

Overnight cost of funds

The overnight cost is typically used to refer to the interest rate charged by financial institutions (banks) who lend money to other banks. The rate is usually set by the central bank of a country which controls how much money in is the economy, this is called the money supply. read more on Overnight cost of funds


Oxygen is the 8th element on the periodic table, and is the 3rd most abundant element in the universe.[70] Although the amount of oxygen in the universe is dwarfed by hydrogen and helium, oxygen is the most common element on Earth, and it is a crucial component of life. read more on Oxygen


Ozone is a molecule of oxygen with the formula O3. read more on Ozone

P-n junction

A P-N junction is formed when a p-type semiconductor and an n-type semiconductor are placed in contact with each other. read more on P-n junction

Pacific Decadal Oscillation

Pacific Decadal Oscillation (PDO) is a long term ocean fluctuation of the Pacific Ocean causing sea surface temperatures to cool or warm over extended periods of time. The PDO fluctuates in its phases approximately every 20 to 30 years.[8] PDO broadens to cover the whole Pacific Basin which known as the InterDecadal Pacific Oscillation (IPO). read more on Pacific Decadal Oscillation

Parallel circuit

Many electrical components in an electric circuit have two leads (ends). As a result, they can be connected in one of two ways, in series (one electrical lead is touching the other), or in parallel (both leads are touching).

Parallel circuits provide more than one current path between any two points. read more on Parallel circuit

Pareto Efficiency

Pareto efficiency refers to an allocation of goods in an economy whereby goods cannot be reallocated without making at least one individual worse off. It is used to evaluate social welfare. read more on Pareto Efficiency

Pareto Improvement

Pareto improvement is a condition on the way to Pareto efficiency whereby goods can be re-allocated to make at least one person better off without making any other individual worse off. Pareto improving behavior, in theory, will continue until Pareto efficiency is reached. read more on Pareto Improvement

Pareto Principles

There are two main theories within his works collectively referred to as Pareto Principles:

  1. Pareto Improvement
  2. Pareto efficiency or Pareto Optimization

read more on Pareto Principles


A particle an object that is treated as if it has no internal structure. As Knight says "An object that can be treated as a point mass is a particle." read more on Particle

Particulate matter

Particulate matter, sometimes called particle pollution or simply PM, is a term that refers to a mixture of solid particles and liquid droplets that can be found in the air. They are classified as pollutants and there are several different sizes of particulate matter. read more on Particulate matter


The pascal (Pa) is the SI unit of pressure. read more on Pascal

Passive solar heating and cooling

Passive solar heating and cooling, sometimes referred to simply as passive solar design, is the process of using specific building systems to help regulate internal temperature by using the Sun's energy selectively and beneficially in an attempt to improve the energy efficiency. read more on Passive solar heating and cooling


When evaluating the viability of a new project, a firm will determine what the payback period of the project is, this is determined by comparing the cost of the initial investment with the annual returns from the project. By comparing these figures, a firm can determine how long it will take for an investment to yield the initial amount used to produce it. read more on Payback

Peak oil

Peak oil is the predicted event, based off of the theory of Hubbert's peak, when the maximum rate of extraction and production of oil is reached. After this point, production will fall continually over time. read more on Peak oil

Peaking power

Peaking power refers to electricity use at its highest points during a day. Day to day trends of power usage need to be met by power plants, however it is not optimal for power plants to produce the maximum needed power at all times. read more on Peaking power


Peat is a soft, crumbly, dark brown substance that is formed as generations of dead and partially decaying organic matter. To form peat, the vegetation must fall and be buried in a relatively oxygen poor environment so that it can be incorporated into layers of the soil without completely decomposing. read more on Peat

Pelton turbine

A Pelton turbine or Pelton wheel is a type of turbine used frequently in hydroelectric plants. These turbines are generally used for sites with heads greater than 300 meters. This type of turbine was created during the gold rush in 1880 by Lester Pelton. read more on Pelton turbine


Penstocks are pipes or long channels that carry water down from the hydroelectric reservoir to the turbines inside the actual power station.[71] Generally, they are made of steel and water under high pressure flows through the penstock. They are a vital component of a hydroelectric facility that allows water to move to the turbine. read more on Penstock


Pentane is a hydrocarbon that can be burned as a fuel. Its chemical formula is C5H12 read more on Pentane

Per capita

The phrase per capita is a Latin phrase that means 'for each person.' Per capita measurement makes some comparisons more meaningful than the total for a country. read more on Per capita


A percentile is a value on a scale of 100 that indicates the percentage of the data set values that is equal to or below it. The percentile is often used to estimate the extremes of a distribution. read more on Percentile

Periodic table of elements

The periodic table of elements is an arrangement of all of the known chemical elements. They are arranged in a specific configuration in order to reflect the similarities between their properties. read more on Periodic table of elements


Permafrost, a permanently frozen layer below some parts of the Earth’s surface (usually in the Arctic or Antarctic), consisting of soil, gravel, and sand, held together by ice.[2] Frozen ground is often confused with permafrost but they aren't the same. Any layer of soil that freezes for more than 15 days in a year is called ‘seasonally frozen ground.’ A layer of soil that freezes between one and 15 days a year is called ‘intermittently frozen ground.’ read more on Permafrost


Permeability refers to the degree to which pore spaces - small pockets of air and empty space - in some material connect to each other, promoting the movement of fluid through that material. read more on Permeability

Permeability of free space

The permeability of free space, μ0, is a physical constant used often in electromagnetism. It is taken to have the exact value of 4π x 10-7 N/A2 (newtons per ampere squared).[72] It is connected to the energy stored in a magnetic field read more on Permeability of free space

Permittivity of free space

The permittivity of free space, ε0, is a physical constant used often in electromagnetism, and is the capability of a vacuum to permit electric fields. It is also connected to the energy stored within an electric field and capacitance. read more on Permittivity of free space

Peroxyacyl nitrate

Peroxyacyl nitrates or PANs are a component of photochemical smog, produced in the atmosphere when oxidized volatile organic compounds combine with nitrogen oxide.[73] They are a secondary pollutant since they form in the atmosphere after the emission of primary pollutants. read more on Peroxyacyl nitrate


Petrochemicals are chemicals derived from petroleum or natural gas. They are an essential part of the chemical industry as the demand for synthetic materials grows continually and plays a major part in today's economy and society. read more on Petrochemical


The writers of this encyclopedia are Canadian, so we refer to petrol as gasoline. Please pardon our regional dialect. read more on Petrol


Petroleum is a broad term that groups together a combination of organic liquids and gases that is formed after kerogen is heated and compressed over long periods of time. This mix can be fairly complex, but the main gaseous component of petroleum is natural gas - largely methane - whereas the main liquid component is crude oil. read more on Petroleum

Phase change

A phase change is a change from one state of matter to another in a thermodynamic system read more on Phase change

Photochemical smog

Photochemical smog is a type of smog produced when ultraviolet light from the sun reacts with nitrogen oxides in the atmosphere. It is visible as a brown haze, and is most prominent during the morning and afternoon, especially in densely populated, warm cities. read more on Photochemical smog


A photon is a particle of light, a packet of electromagnetic radiation. read more on Photon


Photosynthesis is how plants harness the radiant energy from sunlight. This process is important since it's originally how all of the energy in fossil fuels (except for the abiogenic fossil fuels) was captured. This process is also indirectly how animals and humans get energy from the sun in the form of food. read more on Photosynthesis

Photovoltaic cell

A photovoltaic cell (PV cell) is an energy harvesting technology, that converts solar energy into useful electricity. The vast majority are silicon semiconductors, and interact with incoming photons in order to generate an electric current. read more on Photovoltaic cell

Photovoltaic effect

The photovoltaic effect is a process that generates voltage or electric current in a photovoltaic cell when it is exposed to sunlight. It is this effect that makes solar panels useful, as it is how the cells within the panel convert sunlight to electrical energy. read more on Photovoltaic effect

Photovoltaic electricity

Photovoltaic electricity is the electricity generated by the conversion of radiant energy, most commonly done by photovoltaic cells. It uses the principles of Einstein's photoelectric effect, which he received a Nobel Prize for. read more on Photovoltaic electricity

Photovoltaic system

A photovoltaic system, sometimes known as a solar array, is a system composed of one or more solar panels combined with an inverter to generate electricity. These systems use energy from the Sun in the form of sunlight to generate this electricity. read more on Photovoltaic system

Pigouvian subsidy

A pigouvian subsidy is a subsidy that is used to encourage behaviour that have positive effects on others who are not involved or society at large. read more on Pigouvian subsidy

Pigouvian tax

A pigouvian tax or sin tax is a tax levied on actions that have negative effects on others who are not directly involved, a pigouvian tax is essentially a tax on behavior. The tax increases the cost of the action in order to make consumers less likely to act in that way. read more on Pigouvian tax


Pipelines are a vital component in the distribution process of oil and natural gas. Pipelines form extensive distribution networks, and in Canada there is an estimated 825 000 kilometers of lines that serve to transport natural gas, liquefied natural gas products, crude oil, and other refined petroleum products. read more on Pipeline


A piston is a moving disk enclosed in a cylinder which is made gas-tight by piston rings. The disk moves inside the cylinder as a liquid or gas inside the cylinder expands and contracts. read more on Piston

Planck's constant

Planck's constant was first discovered by Max Planck in experiments that helped lead to the formation of quantum mechanics.[74] He formed the Planck Hypothesis that radiation could only come in discrete packets now called photons. read more on Planck's constant


Plasma is the 4th state of matter. It is composed of mostly ionized particles and is often viewed as a gas, however it has much different properties than a typical gas. Although plasma isn't often seen on Earth (aside from lightning, fluorescent tubes, and the Aurora Borealis), some sources say that as much as 99% of the ordinary matter in the universe is plasma.[75] This estimate is based on the idea that all of the stars, gaseous nebulae and interstellar hydrogen are plasmas. read more on Plasma

Pneumatic Hydraulic energy

Pneumatic hydraulic energy is the energy stored in the form of pressurized fluid, making it an application of fluid power. read more on Pneumatic Hydraulic energy

Political economy

Political Economy is the study of economics in a political context, it examines how economics and politics interact to create government policy. read more on Political economy


Pollutants are the elements, molecules and particles involved in pollution - life can be harmed when exposed to these materials, and the effects of them on humans and plants are well known. read more on Pollutant

Polluter pays principle

The idea behind the Polluter-Pays Principle is, the entity that pollutes or creates environmental degradation is the one that should directly pay the cost of the polluting action (as opposed to letting society as a whole pay the cost). read more on Polluter pays principle


Human driven ecological degradation continues to be a major problem around the world. Pollution is the presence of any substance at high enough levels in air, water, soil, or food to threaten the health of human, animal and plant life. read more on Pollution

Pollution vs waste

Determining what is pollution vs waste can be somewhat confusing, however there are ways to look at each and distinguish easily between the two. First, a quick look at the definitions:[76][77]

  • Pollution: the presence in or introduction into the environment of a substance or item that has harmful or poisonous effects.
  • Waste: material that is not wanted; the unusable remains or byproducts of a process.

read more on Pollution vs waste


Pondage is the water that can back-up behind larger run-of-the-river systems. This pondage is essentially a small amount of water storage wherein water is built up during off-peak periods and used during peak periods. read more on Pondage


Porosity is the property of an object that expresses the total volume of empty or pore space in the material. For rocks that contain hydrocarbon resources this is a measure of the percentage of the total rock which is occupied by pore space. read more on Porosity

Positive climate feedback

Positive climate feedback is a process that is one type of climate feedback wherein some initial change in the climate causes some secondary change that in turn increases the effects of the initial change, essentially magnifying the initial effect.[2] Positive climate feedbacks are often discussed in the context of climate change and is one sub-type of positive feedback. read more on Positive climate feedback

Positive externality

Economists use the term externality to describe any time the price determined by a market doesn't reflect the true cost of an action. A positive externality is a good consequence that isn't taken into account. read more on Positive externality

Positive feedback

Positive feedback describes any process that intensifies an initial effect; generally a small push that eventually increases the magnitude of the initial disturbance. This causes some initial change to grow larger and moves the system out of its original equilibrium state. read more on Positive feedback

Potential energy

Potential energy is energy stored in an object or system of objects. read more on Potential energy


The pound, just like the Newton, is a unit of force.[78] It is the standard unit of force in the Imperial system of units. read more on Pound

Pound foot

Pound-feet is a measurement of torque and should not be confused with foot pounds which is a unit of energy.
read more on Pound foot

Pounds per square inch

Pounds per square inch or PSI is an imperial unit of pressure. read more on Pounds per square inch


Power is how fast energy is used or transferred. read more on Power

Power density

Power density is a measure of power output per unit volume. While it is not as commonly used a measurement as energy density, it is still useful for conversations about energy systems (often for portable applications like transportation). read more on Power density

Power plant

A power plant is an industrial facility that generates electricity from primary energy. Most power plants use one or more generators that convert mechanical energy into electrical energy in order to power the electrical grid and, in turn, supply society's electrical needs. The exception is solar power plants, which use photovoltaic cells to generate this electricity. read more on Power plant

Power servant

The Power servant,[79] also called energy servant[80] or energy slave,[81] is a unit of input power equal to 100 watts. read more on Power servant

Power strip

A power strip is a block of electrical outlets that provide AC power to appliances, computers, or any other electrical device. read more on Power strip


Precipitation is a vital part of the hydrologic cycle, and is defined as any water released from the clouds in the sky in the form of rain, freezing rain, sleet, snow, or hail. This is the primary method that water uses to move around in the hydrologic cycle. read more on Precipitation


Predictability is a measure that represents how confident a particular outcome can be determined ahead of time. These forecasts can predict states either quantitatively or qualitatively. read more on Predictability


Prefixes are attached to the front of units or other measures to communicate their relative size. read more on Prefixes


Pressure is an important concept in physics, and is defined as the magnitude of force acting perpendicular to a surface, per unit area. The SI unit for pressure is the pascal, defined as 1 newton per meter squared.[82] read more on Pressure

Pressurized heavy water reactor

A pressurized heavy water reactor is a type of nuclear reactor that makes use of heavy water () as its coolant and moderator. Heavy water contains an isotope of hydrogen called deuterium. read more on Pressurized heavy water reactor

Pressurized water reactor

The pressurized water reactor (PWR) is a type of nuclear reactor, used for the generation of electricity and for propulsion in nuclear submarines and naval vessels.[83] They make use of light water (ordinary water, as opposed to heavy water) as their coolant and neutron moderator. It is one of three types of light water reactors, with the others being the boiling water reactor and the supercritical water cooled reactor. read more on Pressurized water reactor

Prevailing winds

Prevailing winds are winds that blow consistently in a given direction over a particular region on Earth.[84] Due to factors such as uneven heating from the Sun and the Earth's rotation, these winds vary at different latitudes on Earth. read more on Prevailing winds


The price of a good or service is the amount of money that is paid to obtain it. read more on Price

Primary energy

Primary energy is the energy that's harvested directly from natural resources. Sources of primary energy fall into two basic categories, fuels and flows (see fuel vs flow for a detailed discussion). read more on Primary energy

Primary fuel

Primary fuels or primary energy sources are dense sources of primary energy found as natural resources. Primary fuels are fuels that are found in nature and can be extracted, captured, cleaned, or graded without any sort of energy conversion or transformation process. read more on Primary fuel

Primary pollutant

Primary pollutants are any type of pollutant emitted directly into the environment. They differ from secondary pollutants because secondary pollutants must form in the atmosphere, whereas primary pollutants do not. read more on Primary pollutant

Primary vs end use accounting

Primary energy accounting adds up all of the energy harvested from fuels and flows extracted from nature, the total sources of energy. This is different from end use energy accounting, which examines the energy people directly use in the form of secondary fuels and energy currencies. Two different methods of keeping track of this amount of energy have developed, each of these accounting types are used to highlight different parts of the energy sector. A systems approach to energy means being aware of both primary energy accounting and end use accounting. read more on Primary vs end use accounting

Private cost

The private cost is any cost that a person or firm pays in order to buy or produce goods and services. This includes the cost of labour, material, machinery and anything else that the person of firm pays for. The private cost does not take into account any negative effects or harm caused as a result of the production. read more on Private cost

Private good

A private good is a good that a consumer has to pay to use and that consumer who do not pay for it can be prevented from using it (it is excludable). The quantity of a private good diminishes as more and more consumers use the good (it is rivalrous). read more on Private good

Probability risk assessment

Probabilistic risk assessment or PRA is a comprehensive methodology used to evaluate the risks associated with the use of technology. The term technology accounts for a wide range such as a computer, cars or nuclear power plants. read more on Probability risk assessment

Processing algae

Processing algae is necessary to convert algae to biofuel. The harvested algae has to undergo several steps in order to produce consumer-grade products, such as biodiesel and bioethanol. read more on Processing algae


The profit of a firm is simply the revenues it takes in minus the costs it incurs. read more on Profit


Propane is a hydrocarbon with the chemical formula C3H8. read more on Propane

Property tax

A property tax is a tax levied on the value of a property. read more on Property tax


Proppant is a gritty material with uniformly sized particles that is mixed in with fracturing fluid during the hydraulic fracturing (fracking) process to hold open fractures made in the ground. read more on Proppant


Protons are the positively charged particles that are inside the nucleus of an atom. read more on Proton


Pounds per square in gauge, or psig, is a measure of pressure, specifically it is a gauge pressure. This means that it is measured with respect to the atmospheric pressure. read more on Psig

Public attitudes towards energy sources

Public attitudes towards energy sources vary drastically, but are extremely important as well. Public opinion is important since it is insufficient to simply produce electricity, the public must approve of its generation as well. read more on Public attitudes towards energy sources

Public good

A public good is a good that a person can use the without reducing the quantity available to others and others cannot be exclude from using the good. read more on Public good


A pulley is a simple machine that can change the magnitude and direction of an applied force in the process of doing work. It consists of a cable which is attached to a wheel and axle, and is often used to lift/transport objects. When referred to in this context, these objects that are being moved are generally known as the load. read more on Pulley

Pump jack

A pump jack is a device used in the petroleum industry to extract crude oil from a oil well where there is not high enough pressure in the well to force the oil to the surface. These pump jacks physically extract the oil for use. read more on Pump jack

Pumped storage

Pumped storage is the process of storing energy by using two vertically separated water reservoirs.[8] Water is pumped from the lower reservoir up into a holding reservoir. read more on Pumped storage

Purchase power parity

Purchase power parity (PPP) means that if the same good is sold in two countries, it should have the same price when expressed in the same currency. read more on Purchase power parity


The quad is a unit of energy defined as 1 quadrillion (1015) BTU. read more on Quad

Quality of life

Quality of life is an evaluation of the overall well-being of a group in society, determined by looking at a series of factors in a persons life. read more on Quality of life

Quantum mechanics

Quantum mechanics is a branch of science that started in the early 20th century as a number of scientists made certain observations that atoms (and their components) were not behaving as predicted by classical physics and chemistry. read more on Quantum mechanics


The R-value of insulation is a value that is used to measure how well a specific type of insulation can resist heat flow. The higher the R-value, the more effective the material is at preventing heat transfer. read more on R-value

Radiant energy

Radiant energy, also known as electromagnetic radiation (EMR), is energy transmitted without the movement of mass. Practically speaking, this is the energy found in electromagnetic waves, also known as light. Light is made of individual particles called photons, each carrying a small "packet" of energy. Because photons are so small, light energy is often measured in electron volts. Examples of radiant energy include the warmth that radiates from a hot stove and the warmth from direct sunlight. read more on Radiant energy

Radiant heat

Radiant heat, also known as thermal radiation, is the transfer of electromagnetic radiation which describes the heat exchange of energy by photons. Radiant heat is a mechanism for heat transfer which does not require a medium in which it propagates (unlike convection and conduction). read more on Radiant heat


Radiation is the emission or transmission of energy through space or some material in the form of a wave. This radiation spreads out from the source in all directions and "radiates" out. Radiation can also refer to the emitted energy itself. read more on Radiation

Radiative forcing

Radiative forcing is the difference between incoming solar radiation and outgoing terrestrial radiation. This power, and thus the difference, is measured in watts per meter squared. Radiative forcing is considered instantaneous if stratospheric temperature changes aren't accounted for. read more on Radiative forcing

Radioactive vs irradiated

A radioactive object and an irradiated object are very different things. Although they both involve radiation, the way that this radiation interacts with the object is what makes a radioactive substance different than a substance or object that has been irradiated. read more on Radioactive vs irradiated


Radioactivity is a property of certain elements - such as uranium - of emitting energy in the form of radiation as a result of some sort of nuclear decay of an unstable atom.[21] Nuclei that exhibit radioactivity are known as radioactive nuclei. Additionally, radioactivity or simply activity can be used as a measurement to describe how many decays a radioactive atom goes through in a period of time. read more on Radioactivity


Rainforests are a type of forest characterized by their thick tree density (closely spaced, tall trees), large annual rainfall (at least 200 cm) and high specie diversity. read more on Rainforest

Raisebore mining method

The raisebore mining method is an underground mining method to obtain ore, in which a horizontal underground shaft is built below the deposit. read more on Raisebore mining method


The Rankine (°R) is an absolute unit of temperature, named after physicist William John Macquorn Rankine. It is related to the Fahrenheit temperature scale, just like the Kelvin scale is related to Celsius. read more on Rankine

Rankine cycle

The Rankine cycle or Rankine Vapor Cycle is the process widely used by power plants, such as coal-fired power plants or nuclear reactors, in which a fuel is used to produce heat within a boiler, converting water into steam which then expands through a turbine producing useful work. read more on Rankine cycle


RBMK is a Soviet-designed nuclear reactor that uses enriched uranium as its fuel. It is a rather unusual design as it uses graphite as its moderator, and was designed for plutonium production but was also used extensively for electrical generation. The combination of graphite as a moderator and light water as coolant is unique to this reactor, as no other reactors in the world use both. read more on RBMK

Reactor building

Reactor buildings are used for containment of nuclear reactors and many components of a nuclear power plant, to ensure maximum safety in operation and in the event of an accident. The construction of these buildings requires they be extremely strong, and are often made of thickly reinforced concrete or steel walls and roofs. read more on Reactor building

Reciprocating engine

A reciprocating engine is an engine that uses one or more pistons in order to convert pressure into rotational motion. They use the reciprocating (up-and-down) motion of the pistons to translate this energy. read more on Reciprocating engine


A refrigerator is an open system that dispels heat from a closed space to a warmer area, usually a kitchen or another room. By dispelling the heat from this area, it decreases in temperature, allowing food and other items to remain at a cool temperature. read more on Refrigerator

Regenerative braking

Regenerative braking systems (RBSs) are a type of kinetic energy recovery system that transfers the kinetic energy of an object in motion into potential or stored energy to slow the vehicle down, and increase fuel efficiency. read more on Regenerative braking


Regulations are rules established by a government with the force of law to prevent or encourage certain activates. They are enforced by a regulatory body (also created by a government) which monitors a specific activity or industry. read more on Regulation


The Roentgen Equivalent Man or REM is an older, non-SI unit of dose equivalent. read more on Rem

Remote sensing

Remote sensing is the science of measuring properties of an object without physical contact with that object. read more on Remote sensing

Renewable and sustainable energy

The words "sustainable" and "renewable" are often used to describe certain sources of primary energy, often interchangeably. However, these words have very different meanings. Not everything renewable is sustainable, and in turn not everything which is sustainable is necessarily renewable. read more on Renewable and sustainable energy

Replacement rate

Replacement rate is the number of children that a couple would have to have over the course of their reproductive years in order to replace themselves. read more on Replacement rate

Research reactor

Research reactors are nuclear reactors that are not used for the generation of electricity, and instead provide uses for research and training, material testing, and production of isotopes for medical and industrial uses. read more on Research reactor


Reserves are deposits of fossil fuels that are known to exist with a reasonable level of certainty based on geological and engineering studies. These reserves are also recoverable economically with the technologies that already exist. read more on Reserve

Reserve vs resource

Both the term resource and reserve refer to some amount of mineral or fuel, however the ideas are fundamentally different. Primary fuels such as coal, oil, natural gas, and uranium are material resources and have associated reserves. read more on Reserve vs resource

Reserves/production ratio

The reserves/production ratio or R/P is a method used to assess the size of reserves. The value represents the number of years that current reserves would last if their rate of use did not change. read more on Reserves/production ratio


The term reservoir is ambiguous read more on Reservoir

Residential energy use

Residential energy use, also called home energy use, is part of what makes a home where the heart is. It's also where refrigerators, and other appliances are, which makes home a useful place to do personal things. Energy use around the house varies greatly by household, both in quantity (how much energy is used in total) and specific use (percentages used for different energy services). read more on Residential energy use


Resistance is similar to friction for electrical energy; resistance causes the electrical energy to be lost as heat (thermal energy), just like friction causes mechanical energy to be lost as heat. read more on Resistance


Resistivity is a property of materials that determines how well that material will conduct electricity. This property is closely related to resistance which is the property of a particular electrical component. read more on Resistivity


Resistors are electrical components in an electric circuit that slow down current in the circuit. They deliberately lose energy in the form of heat or thermal energy. read more on Resistor


The term resource refers to the total amount of a material or primary energy flow that exists in nature. To emphasize where these resources come from they're often referred to as natural resources. This includes material that is both discovered and undiscovered, economically recoverable or not economically recoverable. read more on Resource

Revolving loan

A revolving loan is a loan that continually renews for a period of time or until the agreement is ended by one party. read more on Revolving loan

Rising sea level

Global warming causes a rising sea level. An increasing amount of heat is trapped by higher levels of of greenhouse gases in the atmosphere. This heat warms the oceans and melts ice. read more on Rising sea level


The Roentgen or R is a non-SI unit for x-ray and gamma radiation in normal conditions under any given volume of air or ionization chamber. read more on Roentgen

Rolling resistance

Rolling resistance refers to the force that resists the movement of some rolling object, such as a ball or a tire. Specifically, rolling resistance is a type of friction. read more on Rolling resistance

Rotary engine

Rotary engines or Wankel engines are a type of internal combustion engine, most popularly used in the Mazda RX-7, which converts heat from the combustion of a high pressure air/fuel mixture into useful work for the rest of the car. Its unique characteristic is its triangular rotor, which performs the same tasks as a reciprocating engine's piston would, but in a very different manner. read more on Rotary engine

Rotational kinetic energy

Rotational kinetic energy is the energy associated with spinning around on an axis. It's an energy of motion, just like linear kinetic energy. Molecules get rotational kinetic energy as well, which becomes part of their thermal energy; this can be seen in the molecule's heat capacity. read more on Rotational kinetic energy


RPM stands for rotations per minute and is also abbreviated rpm. This is a unit which describes how many times an object completes a cycle in a minute. read more on RPM

Run-of-the-river systems

Run-of-the-river hydroelectric systems are hydroelectric systems that harvest the energy from flowing water to generate electricity in the absence of a large dam and reservoir - which is how they differ from conventional impoundment hydroelectric facilities. read more on Run-of-the-river systems

Rural population

Rural population refers generally to the population in areas that have a lower population density than urban areas and are overall more spread out than urban areas. read more on Rural population


A scenario is a plausible description of how the future may develop based on a consistent set of assumptions about driving forces (e.g. rate of technological change, economic developments, etc). For instance, technological advancements may lead to cheaper and more efficient methods of attaining energy, reducing carbon emissions and more. Scenarios are neither predictions nor forecasts, but are useful to provide a view of the implications of alternative developments and actions. read more on Scenario


A scrubber or scrubber system is a system that is used to remove harmful materials from industrial exhaust gases before they are released into the environment. read more on Scrubber


The second is the SI unit of time. Its name comes from being the "second" division of the hour, with the minute being the first. read more on Second

Second law of thermodynamics

The Second Law of Thermodynamics describes the limitations of heat transfer. Most importantly, it sets out the specific idea that heat cannot be converted entirely to mechanical energy. read more on Second law of thermodynamics

Secondary fuel

Secondary fuels are fuels that are derived from some primary fuel or fuels through chemical or physical processes. These are fuels that are not found as a natural resource. read more on Secondary fuel

Secondary pollutant

Secondary pollutants are any type of pollutant that is formed in the atmosphere. These pollutants are not emitted directly from a source, such as vehicles or power plants, instead they form as a result of the pollutants emitted from these. read more on Secondary pollutant

Secured loan

A secured loan is a loan backed by collateral posted by the debtor usually in the form of liquid assets. If the debtor fails to repay the loan within the terms of the contract, the lending institution has the legal right to seize the assets. read more on Secured loan


Sediment is some solid material - whether heavy or light - that is moved by some force and deposited in a new location. The general term used to refer to the force that moves sediment is erosion. read more on Sediment

Sedimentary rock

Sedimentary rock is rock that is formed over a period of time as a result of accumulation of sediment in one area. read more on Sedimentary rock


A semiconductor is an element or compound that conducts electricity under some conditions but not others. This property of being neither a good insulator nor a good conductor makes semiconductors useful for controlling electrical current. read more on Semiconductor

Sensible heat

Sensible heat is literally the heat that can be felt. It is the energy moving from one system to another that changes the temperature rather than changing its phase. For example, it warms water rather than melting ice. read more on Sensible heat

Separative work unit

The Separative Work Unit (SWU) is a unit that defines the effort required in the uranium enrichment process, in which uranium-235 and -238 are separated. read more on Separative work unit

Series circuit

A series circuit provides exactly one path between any two points for electric current. read more on Series circuit

Shading technology

Shading technology is a broad term that describes additions to a building that prevent over-heating or cooling of the space. These additions include, awnings, blinds, deciduous trees, and roof overhangs. read more on Shading technology


Shale is a fine-grained sedimentary rock that is formed when silt and clay are compressed. It is composed of many thin layers, and it readily splits into thin pieces where these layers meet - making it a relatively brittle stone. read more on Shale

Shale gas

Shale gas is a type of natural gas that is trapped within shale formations - arrangements of fine-grained sedimentary rock that are known as "plays" if they contain significant amounts of natural gas. read more on Shale gas

Shale oil

Shale oil, also called tight oil, is a type of oil that can be extracted by heating and upgrading kerogen trapped within shale formations - arrangements of fine-grained sedimentary rock. This type of oil resource is classified as an unconventional resource as the process of obtaining oil from these formations requires specialized processes. read more on Shale oil

Shock hazard

A shock hazard is the potential electric shock to a person that can be caused by many circumstances. It occurs when there is a voltage difference that a person may come into contact with. read more on Shock hazard

Short ton

A short ton is an Imperial unit of mass. It is equal to 2,000 pounds. read more on Short ton


The siemens (S), once known as the mho ()(Ohm spelled backwards), is the SI unit of electrical conductance. read more on Siemens


Silicon (Si) is the 14th element on the periodic table.[2] Silicon is the seventh most abundant element in the universe, and it is very common on Earth. In the Earth's crust, silicon is the second most abundant element. read more on Silicon


Silver is the 47th element on the periodic table. Silver's chemical symbol "Ag" is derived from the Latin word for silver, argentum. read more on Silver

Simple cycle gas plant

Simple cycle gas plants are a type of natural gas power plant which operate by propelling hot gas through a turbine, in order to generate electricity. They differ from combined cycle gas plants because their waste heat is not supplied to another external heat engine, so they are only used to meet peaking power needs on the electrical grid. read more on Simple cycle gas plant

Simple machine

A simple machine is a physical device that changes the magnitude or direction of a force. It should be noted that these machines do nothing to change the amount of energy used, just how hard it is to use that energy. read more on Simple machine

Size of the universe

The size of the universe refers to the relative size of the universe and entities contained within it. read more on Size of the universe


A skylight is essentially a sloped window installed on the roof instead of on a wall. Skylights are installations consisting of an insulating piece of glazing (clear glass-like material) held in an aluminum frame. read more on Skylight


Smog is a type of air pollution. It is a combination of harmful pollutants that are introduced into the atmosphere by both natural and human induced processes, often appearing relatively low to the ground as a yellow-brown haze. read more on Smog


Smoke is a visible collection of a variety of solid, liquid, and gas particles left unburned during the combustion process. read more on Smoke


A smokestack, stack, or chimney is a tall vertical pipe or channel used by power plants to exhaust combustion gases into the air. read more on Smokestack

Solar chimney

A solar chimney is a type of passive solar heating and cooling system that can be used to regulate the temperature of a building as well as providing ventilation. Like a Trombe wall or solar wall, solar chimneys are a way to achieve energy efficient building design. read more on Solar chimney

Solar collector

A solar collector is a device that transforms solar radiation from the Sun into heat, which is then transferred to some fluid. These devices are primarily used for active solar heating and allow for the heating of water for personal use. read more on Solar collector

Solar collector orientation

Considering the placement and orientation of solar energy collectors is just as important as considering which type of solar panel is best to use in a given situation. Ensuring that solar panels face the correct direction and have an appropriate tilt will help ensure that they produce maximum power as they are exposed to the highest intensity of sunlight for the greatest period of time. read more on Solar collector orientation

Solar energy to the Earth

Almost all of the Earth's energy input comes from the sun. Not all of the sunlight that strikes the top of the atmosphere is converted into energy at the surface of the Earth. The Solar energy to the Earth refers to this energy that hits the surface of the Earth itself. read more on Solar energy to the Earth

Solar panel

A solar panel is one component of a photovoltaic system that is constructed out of a series of photovoltaic cells arranged into a panel. read more on Solar panel

Solar pond

A solar pond is a solar energy collector, generally fairly large in size, that looks like a pond. This type of solar energy collector uses a large, salty lake as a kind of a flat plate collector that absorbs and stores energy from the Sun in the warm, lower layers of the pond. read more on Solar pond

Solar power

Solar power is the electricity generated using the solar radiation from the Sun.Currently, solar power supplies about 1% of electricity used every year in the world. read more on Solar power

Solar power tower

A solar power tower is a system that converts energy from the Sun - in the form of sunlight - into electricity that can be used by people by using a large scale solar setup. read more on Solar power tower

Solar thermal power plant

Solar thermal power plants are electricity generation plants that utilize energy from the Sun to heat a fluid to a high temperature. This fluid then transfers its heat to water, which then becomes superheated steam. This steam is then used to turn turbines in a power plant, and this mechanical energy is converted into electricity by a generator. read more on Solar thermal power plant

Solar wall

Solar walls are a technology used to passively heat a building. Similar to trombe walls or solar chimneys, solar walls are one way to achieve energy efficient building design. read more on Solar wall

Solar water heating

Solar water heating or SWH is the process of converting sunlight into energy that can then be used for domestic water heating. This heated water can be used for washing in the home, radiant floor heating, or to heat swimming pools. read more on Solar water heating


Solids, along with gases and liquids, are one of the states of matter. read more on Solid


A solvent is simply a substance that allows some other substance - known as a solute - to dissolve in it, forming a solution. Although a solvent is generally thought of as being liquid, a solvent can be either solid, liquid, or gas. read more on Solvent


Soot, sometimes called lampblack or carbon black, is a fine black or brown powder that can be slightly sticky and is a product of incomplete combustion. read more on Soot


Sound is a wave, and like all waves, sound carries energy. Sound transmits that energy through a medium by making small regions of greater (and lesser) pressure many times a second. read more on Sound


Spacers are small pieces of plastic or metal that work to separate and support the two (or three) panes of glass in a multi-glazed window. These spacers hold the panes in place, thus creating an air space filled with noble gasses such as argon or krypton in gas filled windows. read more on Spacers

Spark plug

A spark plug is used as a source of ignition, as the "spark" in its name might imply. It is a key component of internal combustion engines and its primary function is to ignite a fuel/air mixture within the combustion chamber of a car, or other system. read more on Spark plug

Species migration

Species migration is the seasonal event where animals move from one preferred location to the next as the ecosystem changes throughout the year. read more on Species migration

Specific heat capacity

Specific heat capacity is the amount of heat needed to raise one gram of a material by one degree celsius (oC). read more on Specific heat capacity

Specific power

Specific power or power-to-weight ratio is a measure of performance for an engine in a vehicle or in a power plant. It is defined as the power output by it divided by its mass,[85] typically in units of W/kg or hp/lb. read more on Specific power


Speed is how fast something is moving. It's determined by the ratio of how far it will go in a period of time, divided by how long that period of time is (the duration). read more on Speed

Speed of light

The speed of light, almost always written as c (for celerity, an archaic term for swiftness of motion), is a constant which is a strange consequence of Einstein's theory of relativity. read more on Speed of light

Spent nuclear fuel

After nuclear fuel goes through a reactor once, it is called spent fuel. This is a bit of a misnomer because there's still a fair amount of energy left in the fuel. read more on Spent nuclear fuel


A spillway is a structure constructed in a hydroelectric dam to provide a safe path for floodwaters to escape to some downstream area. Generally, the area that the spillway is released to is the river on which the hydroelectric dam was constructed. read more on Spillway

Standard atmosphere

A standard atmosphere, abbreviated atm, is a unit of pressure that is equal to the average atmospheric pressure at sea level. read more on Standard atmosphere

Standby power

Standby power (also known as vampire power, phantom power and phantom load) refers to the electrical energy that is used by devices even when they are turned off.[86] read more on Standby power

Static electricity

Static electricity is the imbalance of electric charge on a surface of a material. Static means fixed or stationary, therefore it is used in contrast to dynamic (moving) electricity in the form of electric currents. read more on Static electricity


Steam is the gaseous phase of water which is formed when the necessary latent heat of vaporization is supplied to water at its boiling point. Steam is created in power plants at high pressures by the burning of a fuel within a boiler, such as in coal-fired power plants or nuclear reactors, or even by sunlight in a solar thermal power plant. read more on Steam

Steam assisted gravity drainage

Steam assisted gravity drainage or SAGD is a method that is widely used to extract bitumen from underground oil sands deposits. This method involves forcing steam into sub-surface oil sands deposits to heat the bitumen locked in the sand, allowing it to flow well enough to be extracted. read more on Steam assisted gravity drainage


Steel is an alloy of iron with a varying carbon content (typically around 0.5-1.5%), and can also contain different elements depending on the type of steel desired. Whereas iron on its own is relatively soft and rusts easily, steel is hard, tough, and corrosion resistant.[87] This makes steel an extremely useful material that is used almost everywhere in society, from building skyscrapers and bridges to paperclips and thumbtacks. read more on Steel

Stefan-Boltzmann constant

The Stefan-Boltzmann constant is a constant of proportionality, σ = which gives how much power is radiated by an object at a given temperature. read more on Stefan-Boltzmann constant

Stefan-Boltzmann law

The Stefan-Boltzmann law, also known as Stefan's Law, is a law that expresses the total power per unit surface area (otherwise known as the intensity) that is radiated by an object, often taken to be a blackbody. read more on Stefan-Boltzmann law

Stirling engine

Stirling engines are a type of reciprocating external heat engine that uses one or more pistons to achieve useful work through some input of heat from an external source. They differ vastly from internal combustion engines that are seen in most vehicles. read more on Stirling engine

Storm surge

A storm surge is an abnormal rise of water generated by a storm, which exceeds the predicted tide levels. read more on Storm surge


Standard conditions for temperature and pressure (STP) are set standard conditions for the measurement and documentation of chemical and physical processes. read more on STP

Strong nuclear force

The strong nuclear force is one of four fundamental forces in nature. The strong force is 'felt' between nucleons (protons and neutrons) inside of the nucleus of an atom. read more on Strong nuclear force

Sub-bituminous coal

Sub-bituminous coal or black lignite is a grey-black or dark brown fossil fuel and is a mid rank of coal. It ranges from hard to soft as it represents an intermediate stage between low quality lignite and higher quality bituminous coal. read more on Sub-bituminous coal


A subsidy is a payment or tax abatement form the government to the buyer or seller of a good or service to encourage either its sale or purchase. read more on Subsidy


Sulfur (S) is the 16th element on the periodic table. Sulfur is the tenth most abundant element in the universe, and it is fairly common on Earth as well. read more on Sulfur

Sulfur oxides

Sulfur oxides or SOx are a group of pollutants that contain both sulfur and oxygen molecules. Sulfur dioxide, SO2 is the most common form in the lower atmosphere. read more on Sulfur oxides


The Sun is the star at the center of our solar system. It is mostly hydrogen - about 75% of its total mass - and helium - about 25% of its total mass. read more on Sun

Sunk cost

A sunk cost is a cost that has been paid and it cannot be recovered, it is a fixed cost that is unavoidable. read more on Sunk cost


Sunlight, also known as solar radiation, refers to the incoming light to the Earth that originated from the Sun. This light represents a portion of the electromagnetic spectrum that includes infrared, visible, and ultraviolet light. read more on Sunlight


Supercapacitors are a new type of capacitor, also known as ultra-capacitors. The characteristics of supercapacitors give them a higher capacitance than conventional capacitors. Supercapacitors have a higher power density, but they suffer from low energy densities compared to batteries read more on Supercapacitor

Superconducting magnetic energy storage

Superconducting magnetic energy storage (SMES) is the only energy storage technology that stores electric current. This flowing current generates a magnetic field, which is the means of energy storage. The current continues to loop continuously until it is needed and discharged. read more on Superconducting magnetic energy storage


A superconductor is a material that has absolutely no electrical resistance (0 Ω) and interesting interactions with magnetic fields. read more on Superconductor

Supercritical coal plant

Supercritical coal plants are a type of coal-fired power plant used in more modern designs. They differ from traditional coal power plants because the water running through it works as a supercritical fluid, meaning it is neither a liquid or a gas. read more on Supercritical coal plant

Supercritical fluid

Any fluid pushed to a temperature and pressure where it is no longer possible to differentiate between the liquid and gas phase becomes a supercritical fluid. read more on Supercritical fluid

Supercritical water cooled reactor

Supercritical water cooled reactor (SCWR) is a proposed Generation IV nuclear reactor which would function above the thermodynamic critical point of water. read more on Supercritical water cooled reactor


Supply is: "the quantity of a good or service that producers are willing to provide at the specified price, time period, and condition of sale". read more on Supply


A switch is an electrical component that breaks or closes a circuit. Opening the switch (breaking the circuit) means turning off the electrical device and closing the switch (completing the circuit) means allowing electrical current to flow so that the device is on. read more on Switch

Syndicated loan

A loan that is provided by a group of lending institutions to a debtor is known as a syndicated loan, the group of institutions agree to provide a level of funds and in doing so the group is called a syndicate. Among the group of lenders will be a "head" or "principle underwriter" who is in charge of negotiating with the debtor and setting the terms of the agreement. read more on Syndicated loan

Synthetic natural gas

Synthetic natural gas is a type of gas created from coal that serves as a substitute for natural gas and is suitable for transmission in natural gas pipelines. This natural gas substitute must have a minimum of 95% methane in it. read more on Synthetic natural gas


A system, as it is defined in physics or chemistry, is nothing more than a collection of objects (or smaller systems) that can be identified. read more on System

Tail race

The tail race, containing tail water, is a channel that carries water away from a hydroelectric plant or water wheel. The water in this channel has already been used to rotate turbine blades or the water wheel itself. read more on Tail race

Tar sands

Tar sands is a term that was historically[88] used to refer to the oil sands. Now the term is mostly used by people who wish to be derogatory, especially those concerned about the environmental impact. read more on Tar sands


A tariff is a tax on goods and services imported into a country from another. read more on Tariff


A tax is a charge that is paid by a person, firm or other legal entity to a government in order to fund public services. read more on Tax

Tax abatement

A tax abatement is similar to a deduction or tax credit. A tax abatement is typical used to reduce the level of property tax faced by an individual or firm for period of time. read more on Tax abatement

Tax credit

A tax credit is a certain amount that a tax payer is able to subtract from their annual taxes they owe to the government, the size of the credit and the restrictions are determined beforehand. read more on Tax credit

Tax exemption

A tax exemption reduces the total tax owed, because a person, or particular source of money is exempt (not counted toward the total). read more on Tax exemption

Tax refund

A tax refund is an amount of money paid back to a tax payer if their annual tax payment was more than they should have paid. read more on Tax refund


Technology is the practical application of knowledge to achieve particular goals.[89] This application almost always requires a certain amount of equipment and information. read more on Technology


Temperature is the reading obtained from a thermometer, which measures how hot or cold a substance is. read more on Temperature

Temperature of the Earth

The average temperature of the Earth is a fundamental part of what allows Earth to be habitable. Of all of the planets that have been found, Earth is the only one known to support life. This "perfect" temperature exists because Earth lies in a "Goldilocks zone" in terms of temperature, being neither too hot nor too cold to support life. read more on Temperature of the Earth


Tension is a force associated with the pulling of an object such as a rope, cable, or chain. It is very similar to elastic potential energy. read more on Tension

Term loan

A term loan is simply a loan that has to repaid in equal increments until the amount is repaid at the date that is specified.[90] Other variables and stipulation can apply. read more on Term loan


The Tesla is the unit for magnetic field, named after inventor and physicist Nikola Tesla. It is defined as one Newton of force per Ampere of current per meter of conductor, therefore it has units of [math]\frac{kg}{A\times s^2}[/math]. read more on Tesla

The greenhouse effect and Earth's energy budget

The greenhouse effect plays a significant role in Earth's energy budget. With the natural greenhouse effect, the energy budget is balanced as thermal radiation is re-radiated towards the ground, trapping thermal energy and warming the Earth. However, with the greenhouse effect being enhanced by humans, the energy budget of the Earth is shifted to an imbalance. read more on The greenhouse effect and Earth's energy budget

The pH scale

The term pH is an abbreviation for power of Hydrogen, which is a measure of how acidic or basic a chemical solution is. read more on The pH scale

Thermal conduction

Thermal conduction is the direct sharing of kinetic energy (heat) between materials in contact, specifically when talking about heat transfer. read more on Thermal conduction

Thermal conductivity

Thermal conductivity, frequently represented by , is a property of a material that relates the rate of heat loss per unit area of the material to the rate of change of temperature of the material.[91] Essentially, it is a value that accounts for any property of the material that could change the way it conducts heat. read more on Thermal conductivity

Thermal efficiency

The thermal efficiency of a heat engine is the amount of useful work an engine can do based on the amount of heat input. read more on Thermal efficiency

Thermal energy

The thermal energy of an object is the energy contained in the motion and vibration of its molecules. read more on Thermal energy

Thermal equilibrium

Thermal equilibrium is the state of a system in which its heat flow is balanced with its surroundings, meaning the temperatures of the system and surroundings are the same. read more on Thermal equilibrium

Thermal insulation

Insulation is the term used for a variety of materials used to reduce heat transfer. It is part of the building envelope, used to limit heat loss through walls, roofs or floors. read more on Thermal insulation

Thermal mass

Thermal mass refers to the material inside a building that can help reduce the temperature fluctuations throughout the course of the day; thus reducing the heating and cooling demand of the building itself. read more on Thermal mass

Thermal power

Thermal power is a measure of power given by the exchange of heat in a system over time. read more on Thermal power


Thermodynamics is the study of how heat can be transformed into useful energy in the form of work, hence the name thermo + dynamics.[52] It is an extremely vast and intricate area of science which took many years to develop, beginning in the early 19th century. read more on Thermodynamics

Thermohaline circulation

Thermohaline circulation describes the movement of ocean currents due to differences in temperature and salinity among regions in the water. read more on Thermohaline circulation


A thermostat is a control device that switches the heating system in a house on or off as necessary. It works by sensing air temperature, and switching the heating devices on or off depending on whether or not the ambient temperature is above or below a setpoint. read more on Thermostat


Thorium is the 90th element on the periodic table, the second heaviest element on Earth. Thorium is known for its potential to provide nuclear energy in nuclear reactors, much like uranium which is the current dominant nuclear fuel. It was discovered in 1828 by Swedish chemist Jons Jakob Berzelius, who named it after Thor, the Norse god of thunder. read more on Thorium

Thorium fuel cycle

The thorium fuel cycle is the path that thorium transmutes through from fertile source fuel to uranium fuel ready for fission. read more on Thorium fuel cycle

Three Mile Island nuclear accident

Three Mile Island nuclear accident occurred at the Three Mile Island nuclear power plant in nuclear reactor number 2 (TMI-2) on March 28, 1979, located near Middletown, Pa., U.S.A.[92] A partial meltdown occurred in the reactor core, and caused the most serious accident in civilian U.S. nuclear power history; although the small release of radioactive materials had no detectable health effects on the public. read more on Three Mile Island nuclear accident


Thrust is a force used to propel an object by expelling gas molecules at high speeds. read more on Thrust

Tidal barrage

Tidal barrage systems are a tidal power generation method that work similar to hydropower and have sluices that control the tidal flow to drive turbines and generate electricity. read more on Tidal barrage

Tidal force

The tidal force is a primary energy source and can be considered an energy flow. In fact, animals on Earth have been taking advantage of tides for as long as they have existed. read more on Tidal force

Tidal power

Tidal power harnesses the energy from the tidal force and wave action in order to generate electricity. Unlike other energy flows, it is a predictable source of energy because tides occur at expected times. read more on Tidal power

Tidal stream generator

Tidal stream generators make use of the kinetic energy of moving water to turn a turbine - similar to the way a wind turbine uses wind to create electricity. read more on Tidal stream generator

Tight gas

Tight gas is natural gas trapped within a rock with extremely low permeability - typically limestone or sandstone. This is not to be confused with shale gas, which is natural gas trapped within shale formations. read more on Tight gas

Time value of money

Money that is held now is worth more than the same amount of money later. read more on Time value of money

Timescale of hydrocarbon formation

The timescale of hydrocarbon formation refers to the approximate time that it takes hydrocarbons of a variety of different types to form. Generally speaking, when investigating the timeline of hydrocarbon formation geologic time is most important to investigate. Geologic time is simply a timescale used by geologists to relate features of the Earth's crust to a time period. read more on Timescale of hydrocarbon formation

Timescale of the universe

The timescale of the universe refers to the relative size of the universe and all events occurring within it. read more on Timescale of the universe

Tonne of oil equivalent

Tonne of oil equivalent (toe) is a unit of energy, defined as the amount of energy released by burning one tonne (1000 Kilograms) of crude oil. read more on Tonne of oil equivalent


Torque is the tendency of a force to cause a rotational movement[93]. It is measured in newton meters in the SI system, and pound-feet in the Imperial system. read more on Torque

Total cost

In economics, all resources are valued at their opportunity cost, which is the value of the alternative use of the resources. Costs are defined in a variety of ways and under a variety of assumptions that affect their value. The opposite of a cost is a benefit and often both are considered together, for example, net cost is the difference between gross costs and benefits.[94]

Total Cost

<onlyinclude>The total cost is the sum of fixed costs and variable costs. read more on Total cost

Total final consumption

Total final consumption of energy for a country is the aggregate of all of the energy that is used for providing various energy services. Usually, total final consumption is an aggregate of end use energy. read more on Total final consumption

Total primary energy supply

Total primary energy supply (TPES) is the total amount of primary energy that a country has at their disposal. This includes imported energy, exported energy (subtracted off) and energy extracted from natural resources (energy production). read more on Total primary energy supply

Town gas

Town gas or coal gas refers to a gaseous mixture, used as a fuel, that is released when bituminous coal is burned. Recently, some power plants have begun creating town gas not using coal, rather using heavy oil and naphtha as their feedstocks. read more on Town gas

Tragedy of the commons

When a common resource is used without restraint to the point where it has a negative effect on those who rely on it is said to be a tragedy of the commons. read more on Tragedy of the commons


Transducers are devices that transform energy from one form into another. read more on Transducer


A transformer is an electrical device that uses electromagnetic induction to pass an alternating current (AC) signal from one circuit to another, often changing (or "transforming") the voltage and current. read more on Transformer


Transistors are electrical components of circuits that can act as amplifiers and as switches. Transistors are integral to modern circuitry, with hundreds of millions of them used in modern integrated circuits for computing. read more on Transistor


The term transmission is ambiguous read more on Transmission

Transmission (vehicle)

Transmission is used in cars to vary the torque going from the engine to the drive wheels. It is an important part of the drive train. read more on Transmission (vehicle)


Transmutation or nuclear transmutation is a process that involves a change in the nucleus of an atom. When the number of protons in the nucleus of an atom changes, the identity of that atom changes as it is transmuted into another element or isotope. read more on Transmutation


Transpiration is the process in which plant roots absorb water and then release the water in the form of vapour through the leaves. read more on Transpiration


Transportation is the movement of people, animals and goods between any two locations in the world, or even outside of it. Types of transportation includes air, sea, land, underground and space, with differing methods on achieving the task for each type of medium. read more on Transportation

Transportation energy use

Transportation energy use refers to the end use energy consumed by all components in the transportation sector - the production, operation, and decommissioning of all vehicles and infrastructure. read more on Transportation energy use

Transportation of liquefied natural gas

The transportation of liquefied natural gas (LNG) refers to any movement or shipping of natural gas while in its liquid form. The two major methods of transporting LNG are by pipeline and vessel read more on Transportation of liquefied natural gas

Transportation of oil

The transportation of oil is the final step that oil takes before it is distributed to consumers. The transportation of oil is a part of midstream industry. read more on Transportation of oil

Trillion cubic feet

A Trillion cubic feet (1 Tcf = 1,000,000,000,000 cubic feet) is a volume measurement used by the oil and gas industry. A Tcf of natural gas is approximately equal to a quad of energy. read more on Trillion cubic feet

Trombe wall

Trombe walls are a type of technology that can be installed in homes to passively heat the building. The inclusion of Trombe walls reduces the need to heat the building using traditional methods such as furnaces or other space heaters, reducing the amount of energy used to heat the home. Like a solar chimney or solar wall, Trombe walls are a way to achieve energy efficient building design. read more on Trombe wall


Turbidity is a measure of the particles in water, particularly how much the material present in the water disrupts the passage of light. read more on Turbidity


A turbine is a device that harnesses the kinetic energy of some fluid - such as water, steam, air, or combustion gases - and turns this into the rotational motion of the device itself.[2] These devices are generally used in electrical generation, engines, and propulsion systems and are classified as a type of engine. read more on Turbine

Turgo turbine

A Turgo turbine is a type of turbine, developed in the 1920s, that is a variant of the Pelton turbine. The main difference between a Pelton turbine and a Turgo turbine is that Turgo turbines use single cups instead of double cups on the wheel, and these cups are more shallow. read more on Turgo turbine

Types of natural gas deposits

Natural gas can be contained in a variety of different types of deposits that must be accessed if the natural gas is to be used. read more on Types of natural gas deposits

Types of PV cells

Photovoltaic cells or PV cells can be manufactured from a variety of different materials. Despite this difference, they all perform the same task of harvesting solar energy and converting it to useful electricity. The most common material for solar panel construction is crystalline silicon which has semiconducting properties. read more on Types of PV cells

Types of wind turbines for microgeneration

There are two different types of wind turbines for microgeneration, meaning that they can be installed for a home to generate electricity. Both of these types of wind turbines have their own advantages and disadvantages. read more on Types of wind turbines for microgeneration


The U-value of insulation is a value that is used to measure how well a specific type of insulation can resist heat flow. The lower the U-value, the more effective the material is at preventing heat transfer. read more on U-value

Ultraviolet radiation

Ultraviolet radiation (UV) is a type of radiant energy, much like the light we see, but with a smaller wavelength and therefore higher energy. It is defined as the light in the spectrum of wavelengths between 40-400 nanometers. read more on Ultraviolet radiation


Uncertainty is an expression of the degree to which a value or relationship is unknown. read more on Uncertainty

Unconventional resource

Unconventional resources are resources, generally oil or natural gas resources, that do not appear in traditional formations and must use specialized extraction or production techniques to obtain fuel from the deposit. read more on Unconventional resource


Units are magnitudes of a physical quantity, defined by convention or law which sets a standard for any measurements of the same physical quantity. read more on Units

Unsecured loan

An unsecured loan is a loan that depends entirely on the credit rating of the debtor who has not posted collateral. read more on Unsecured loan

Upstream oil and gas industry

Upstream industry is the portion of the oil and natural gas industry that is responsible for finding crude oil and natural gas deposits, along with producing them. Upstream industry is sometimes known as the exploration and production or E&P sector. read more on Upstream oil and gas industry


Uranium is the 92nd element on the periodic table, and is the heaviest naturally occurring element on Earth.[95] It is known for being an abundant source of concentrated energy,[96] with the largest energy density of any of the world's fuels used for the generation of electricity. read more on Uranium

Uranium enrichment

Uranium enrichment is a process that is necessary to create an effective nuclear fuel out of mined uranium by increasing the percentage of uranium-235 which undergoes fission with thermal neutrons. read more on Uranium enrichment

Uranium hexafluoride

Uranium hexafluoride - with the chemical formula UF6 - is a chemical compound that contains one atom of uranium and six atoms of fluorine (see figure 1). In its solid form, uranium hexafluoride is a white crystalline substance (see figure 2). This uranium compound is used during the uranium enrichment process. read more on Uranium hexafluoride

Uranium mining

Uranium mining is the process of retrieving uranium from deposits for use in nuclear reactors to generate electricity. Uranium is also used for the important task of producing medical isotopes. read more on Uranium mining

Urban population

Urban population generally refers to the population inhabiting areas that have a greater population density than rural areas and are overall more compact than rural areas. read more on Urban population


In the public works sense, utility refers to companies who manage the water, gas and electrical electrical systems of a jurisdiction whereas utility in the economic sense refers to the maximization of ones happiness or satisfaction read more on Utility

Utility (economic)

Utility essentially refers to the welfare of an individual, it is a measure of the level "happiness" or "satisfaction" with a certain good or bundle of goods. The concept of utility is based on the assumption that a rational person will seek to maximize their utility or happiness. read more on Utility (economic)


Vacuums, such as the vacuum of space, contain no matter of any type. read more on Vacuum

Valence and core electrons

Valence electrons are the electrons orbiting the nucleus in the outermost atomic shell of an atom. Electrons that are closer to the nucleus are in filled orbitals and are called core electrons. read more on Valence and core electrons

Valence band

The valence band is the band of electron orbitals that electrons can jump out of, moving into the conduction band when excited. The valence band is simply the outermost electron orbital of an atom of any specific material that electrons actually occupy. read more on Valence band

Value added tax

A value added tax (VAT) is a consumption tax that is levied on the difference between the price paid by the seller and the price paid by the consumer for a good. read more on Value added tax

Variable cost

In economics, all resources are valued at their opportunity cost, which is the value of the alternative use of the resources. Costs are defined in a variety of ways and under a variety of assumptions that affect their value. The opposite of a cost is a benefit and often both are considered together, for example, net cost is the difference between gross costs and benefits.[97]

Variable Cost

<onlyinclude>A variable cost is incurred by a firm as it changes its level of output, in short, a firm pays more to produce more. Variable costs are inputs that can be easily adjusted such as the purchase of raw materials for manufacture. read more on Variable cost


A vector is a mathematical tool used to represent physical quantities that require both a magnitude and direction to describe. Such physical quantities include things like positions, velocities and forces. read more on Vector


Velocity is the measurement of speed included with a direction. read more on Velocity

Venturi effect

The Venturi effect describes how the velocity of the fluid increases (thus increasing the kinetic energy of the water) as the cross section of the container decreases, like in a funnel. read more on Venturi effect


In chemistry, the term volatile refers to the tendency of a substance to vaporize. At a given temperature a more volatile substance will more readily turn to gas as the molecules escape from the surface. read more on Volatile

Volatile organic compound

Volatile organic compounds (VOCs) are organic molecules - specifically hydrocarbons - that are classified as a pollutant as they produce undesirable effects in the atmosphere. The are defined as volatile because they evaporate quickly and easily into the air. read more on Volatile organic compound


The volt is the SI unit that measures voltage difference or potential difference. The symbol for volt is V. read more on Volt


Voltage is often used as a shorthand term for voltage difference, which is another name for potential difference. Voltage measures the energy that charge will get if it moves between two points in space. read more on Voltage


Volume is an amount of three dimensional space. read more on Volume

Wall assembly

The wall assembly consists of a system of components that fulfill the support, control, and finish function of the building envelope. read more on Wall assembly

Waste heat

Waste heat is the unused heat given to the surrounding environment (in the form of thermal energy) by a heat engine in a thermodynamic process in which it converts heat to useful work. The second law of thermodynamics requires that waste heat must be produced when converting a temperature difference into mechanical energy (which is often turned into electrical energy in power plants). read more on Waste heat


Water is a molecule made of one oxygen and two hydrogen atoms. Water is the most important chemical for life on Earth. read more on Water

Water impacts of oil sands

One major environmental impact that comes from extraction in the oil sands is the water use. The water used in oil sands development is used in surface mining to separate the extracted oil sand into sand and bitumen components, while water is converted to steam in SAGD operations to separate the bitumen from the sand before it is extracted. read more on Water impacts of oil sands

Water quality degradation

Water quality degradation is one of the major concerns associated with developing hydroelectric facilities. Hydropower, although free from direct carbon emissions that fossil fuel combustion produces, has a wide variety of other environmental impacts. The degradation in the quality of water that flows through hydroelectric dams and is held in hydroelectric reservoirs is a major concern as it effects a wide range of plant and animal life. read more on Water quality degradation

Water storage

Water storage refers to the process of holding water in some holding area for a period of time. There are multiple locations on Earth where water is stored, and the water stays there for variable periods of time depending on where exactly it is being stored. read more on Water storage

Water vapour

Water vapour is water in gaseous instead of liquid form. It can be formed either through a process of evaporation or sublimation. Unlike clouds, fog, or mist which are simply suspended particles of liquid water in the air, water vapour itself cannot be seen because it is in gaseous form. read more on Water vapour


A waterwheel is a type of device that takes advantage of flowing or falling water to generate power by using a set of paddles mounted around a wheel. The falling force of the water pushes the paddles, rotating a wheel. This rotation of a wheel can be transmitted to a variety of machines through a shaft at the center of the wheel. read more on Waterwheel


A watt is the SI unit for power. A watt is equal to 1 Joule per second , or (energy in an amount of time). read more on Watt


The watt-hour is a unit of energy equal to one watt of output for an hour.[98] It is equal to 3,600 joules. read more on Watt-hour


A watt-year (Wyr) is the measure of energy output by one watt in one year. This unit almost always refers to an amount of electricity generated by a group of power plants or an entire electrical grid. read more on Watt-year


A wave is some disturbance that travels through a medium, creating motion that propagates through the medium from one location to another. This wave can carry energy from its source to another location. read more on Wave


The wavelength of a specific wave is the distance over which a wave repeats. These repeating patterns known as wavelengths are represented by the letter lambda (λ). read more on Wavelength

Weak nuclear force

The weak nuclear force (or just the weak force, or weak interaction) acts inside individual nucleons, which means that it is even shorter ranged than the strong force. It is the force that allows protons to turn into neutrons and vice versa through beta decay. read more on Weak nuclear force


Wealth is a measure of value that can be used to assess different aspects of ones position. Wealth can be measured in terms of monetary well-being, quality of life and other factors. Generally wealth is described as being some measure of the value held by a person, company, community, or country. read more on Wealth


Weather refers to the instantaneous or near-term state of the atmosphere in a given location. Put simply, weather is what the sky is doing right now. read more on Weather

Weather stripping

Weatherstripping is a very simple and relatively low-cost way to improve the energy efficiency of a home by reducing air leaks through doors and operable windows by sealing the movable connections, when they are in the closed position, more completely against air drafts. read more on Weather stripping


A weir is a small barrier that is built across a stream or river to raise the water level slightly on the upstream side, and is essentially a small-scale dam. Weirs allow for water to pool behind them, while still allowing water to flow steadily over top of the weir itself. read more on Weir

Well casing

A well casing is a lining that is installed in an oil well once it is drilled and surrounds the well entirely. Casing is typically hollow steel pipe that lines the inside of the wellbore.[8] Casings are used to support the well, as the raw sides of the well would collapse in without support.[2] read more on Well casing

Wet scrubber

A wet scrubber or wet scrubber system is one type of scrubber that is used to remove harmful materials from industrial exhaust gases before they are released into the environment. It was the original type of scrubbing system, and utilizes a wet substance to remove acidic gases that contribute to acid rain. read more on Wet scrubber

Wheel and axle

The wheel and axle is a type of simple machine used to make tasks easier in terms of manipulating forces through the application of the concept of mechanical advantage. The wheel and axle consists of a round disk, known as a wheel, with a rod through the center of it, known as the axle. read more on Wheel and axle

Wien's Law

Wien's Law, sometimes called Wien's Displacement Law, is a law that determines at what wavelength the intensity of radiation emitted from a blackbody reaches its maximum point. read more on Wien's Law


Wind is the motion of air in the atmosphere. Movement means that the air has macroscopic kinetic energy read more on Wind

Wind chill

Anyone who has experienced a cold winter has most likely experienced the phenomena of wind chill. Wind chill is the sensation that is caused by the combined effect of temperature and wind, and in turn makes cool temperatures feel much colder. read more on Wind chill

Wind farm

A wind farm is a collection of wind turbines within a region used to generate electricity. Wind farms may be very large, covering areas of hundreds of square miles. They can also be offshore, located in a body of water. read more on Wind farm

Wind farm vs wind turbine

It is important to know the difference between a wind farm and wind turbine when talking about the topic of wind power:

A wind turbine is a single unit, which looks like an airplane propeller on top of a long stick. It transfers energy from the wind into rotational motion, which it then transforms into electricity by the use of a generator. A single turbine may be used to provide electricity to a group of houses or buildings, and smaller turbines may be used for an individual home or building.

A wind farm is a collection of these wind turbines in a given location, used collectively for the generation of electricity. A wind farm is often a very large installation, which can be hundreds of square kilometers in area, and provide electricity to the electrical grid for use by thousands of people. read more on Wind farm vs wind turbine

Wind power

Wind power is the generation of electricity from wind. Wind power harvests the flow of energy in the atmosphere generated from the uneven heating of the Earth’s surface by the Sun. Therefore, wind power is an indirect way to harness solar energy. Wind power is converted to electrical energy by wind turbines.[99] read more on Wind power

Wind resource measurement

Wind resource measurement is an import aspect of planning wind power development. Information about how hard the wind blows and in what directions is needed to determine how much power a proposed wind farm in an area would produce (see wind power). read more on Wind resource measurement

Wind turbine

Wind turbines operate by transforming the kinetic energy in wind into mechanical power which is used to generate electricity by spinning a generator. read more on Wind turbine


Windows are openings in walls, doors, or vehicles that allow the passage of light. Windows are important for household energy efficiency because they're how homes let heat and light in and out. read more on Window

Window frame

The window frame is the portion of the window that holds the glazing and sits between the glazing and the wall of the building when installed. The frame can be fairly simple in a non-operable window to very complex with numerous moving parts in an operable, multi-pane window. read more on Window frame


Wires are pieces of metal that transport electricity. read more on Wire

Wire gauge

Wire gauge is the measure of how large of a cross section a wire has. Knowing the gauge is important because it tells you how much current a wire can carry without being damaged - this quantity is called ampacity. read more on Wire gauge


Wood is an organic substance that has been used as a fuel for thousands of years. read more on Wood


Work is the transfer of mechanical energy from one object to another. Since work is a change in energy, it is measured in the same units as energy: joules (J). read more on Work

Work-energy theorem

The work-energy theorem explains the idea that the net work - the total work done by all the forces combined - done on an object is equal to the change in the kinetic energy of the object. read more on Work-energy theorem

World population

The world population refers to the entire number of people of all ages, living in all countries throughout the world. The world population is growing, and in 2015 is approximately 7.3 billion people. read more on World population


Yellowcake uranium the powdered typically yellow form of uranium oxide with the chemical formula U3O8. read more on Yellowcake

Yukon power grid

The Yukon power grid is located in Yukon, Canada and is isolated from the North American grid. Because of this, it faces some unique challenges in providing power to residents of the Yukon. read more on Yukon power grid


Zinc is the 30th element on the periodic table. It is a silvery-white metal that tarnishes in air, and has many uses in society. read more on Zinc

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