Fuel vs flow - Revision history

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	[[category:fuels]]		[[category:fuels]]
	[[category:energy flows]]		[[category:energy flows]]
	<onlyinclude>Different types of [[primary energy]] fall into two main categories: '''[[fuel]]s and [[flow]]s'''. '''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 [[tidal power\|tides]].</onlyinclude><ref>Wolfson, "Earth's Energy Endowment," ''Energy, Environment, and Climate,'' Second edition. London, England: Norton, 2012, chapter 1.6</ref> Once the energy is extracted from a fuel, it's gone, but extracting the energy from a flow is different. Natural processes put energy back into flows over time making them [[renewable and sustainable energy\|renewable]].		<onlyinclude>Different types of [[primary energy]] fall into two main categories: '''[[primary fuel]]s''' and '''[[primary energy flow]]s'''. '''Fuels''' like [[coal]], [[natural gas]], and [[uranium]] are dense stores of energy that are consumed when used. '''Primary flows''' are natural processes that have energy associated with movement. Using a primary flow means harnessing [[energy]] that comes from this movement like [[wind]] and [[tidal power\|tides]].</onlyinclude><ref>Wolfson, "Earth's Energy Endowment," ''Energy, Environment, and Climate,'' Second edition. London, England: Norton, 2012, chapter 1.6</ref> Once the energy is extracted from a fuel, it's gone, but extracting the energy from a primary flow is different. Natural processes put energy back into primary flows over time making them [[renewable and sustainable energy\|renewable]].

	===Fuel===		===Fuel===
	Most of the world's primary energy (90-95%) comes from fuels (see Figure 1). Of these [[primary fuel]]s like [[coal]] and [[natural gas]] are put into power plants. Crude [[oil]] is processed into [[secondary fuel]]s, like [[gasoline]], [[diesel]] and [[kerosene]]. Most cars are propelled by igniting a fuel like gasoline or diesel. Coal, natural gas, gasoline, and diesel are all considered to be fuels, because the energy we take from them is stored discretely inside them, and once we use it up, the fuel is gone. Fuels are [[dispatchable source of electricity\|dispatchable]], which means the energy is available whenever it is needed.		Most of the world's primary energy (90-95%) comes from fuels (see Figure 1). Of these [[primary fuel]]s like [[coal]] and [[natural gas]] are put into power plants. Crude [[oil]] is processed into [[secondary fuel]]s, like [[gasoline]], [[diesel]] and [[kerosene]]. Most cars are propelled by igniting a fuel like gasoline or diesel. Coal, natural gas, gasoline, and diesel are all considered to be fuels, because the energy we take from them is stored discretely inside them, and once we use it up, the fuel is gone. Fuels are [[dispatchable source of electricity\|dispatchable]], which means the energy is available whenever it is needed.

	===~~Flow~~===		===Primary Energy Flows===
	Power sources like [[hydroelectricity]], [[tidal power]], [[wind power]], and [[solar power]] take advantage of energy flows, where energy is harnessed from natural energy sources. An energy ~~flow differs from a fuel because~~ an energy flow is ~~simply~~ a ~~movement of~~ energy from ~~one place to another, whereas a fuel is a substance that stores energy~~.		Power sources like [[hydroelectricity]], [[tidal power]], [[wind power]], and [[solar power]] take advantage of primary energy flows, where energy is harnessed from natural energy sources. A fuel is a substance that stores energy while an energy flow is a natural process that has energy that can be extracted from the process.

	==Why it matters==		==Why it matters==

	Both fuels and flows can be [[renewable and sustainable energy\|sustainable]], but for the most part, only flows are [[renewable and sustainable energy\|renewable]]. For a discussion of why this distinction is important please see [[renewable and sustainable energy]].		Both primary fuels and primary flows can be [[renewable and sustainable energy\|sustainable]], but for the most part, only flows are [[renewable and sustainable energy\|renewable]]. For a discussion of why this distinction is important please see [[renewable and sustainable energy]].

	[[Public attitudes towards energy sources\|Public perception]]s of these fuels and flows are complex, but the science is clear: each fuel and flow has its own advantages and drawbacks. Comparing which is the best is not straightforward, and depends on many parameters.		[[Public attitudes towards energy sources\|Public perception]]s of these fuels and flows are complex, but the science is clear: each fuel and flow has its own advantages and drawbacks. Comparing which is the best is not straightforward, and depends on many parameters.

	~~Flows~~ almost always have fewer [[emission]]s and [[pollution]] than fuels (although nuclear fuels lead to very few emissions). This is especially true of the [[CO2 footprint]], which has led to aggressive pursuit of flows, especially by environmental groups. While there is usually no direct [[pollution vs waste\|waste]] from flow harvesting technologies [[life cycle analysis]] often shows that there is waste that should be taken into consideration. The [[carbon dioxide]] released from harvesting flows is almost always quite a bit less ([[greenhouse gases from hydroelectricity]] are a problem, ~~and in~~ theory it's possible to [[carbon capture and storage\|capture and sequester carbon]] dioxide from fossil fuel plants~~. Although as of 2015 only~~ the [http://www.saskpowerccs.com/ccs-projects/boundary-dam-carbon-capture-project/ \|Boundary Dam project] in Saskatchewan Canada ~~is actually capturing [[Carbon dioxide\|CO2]]~~.		Primary energy flows almost always have fewer [[emission]]s and [[pollution]] than fuels (although nuclear fuels lead to very few emissions). This is especially true of the [[CO2 footprint]], which has led to aggressive pursuit of flows, especially by environmental groups. While there is usually no direct [[pollution vs waste\|waste]] from flow harvesting technologies [[life cycle analysis]] often shows that there is waste that should be taken into consideration. The [[carbon dioxide]] released from harvesting flows is almost always quite a bit less. The [[greenhouse gases from hydroelectricity]] are a problem, but tend to be less of a problem than fossil fuels. In theory it's possible to [[carbon capture and storage\|capture and sequester carbon]] dioxide from fossil fuel plants, but it appears expensive and difficult, see for example the [http://www.saskpowerccs.com/ccs-projects/boundary-dam-carbon-capture-project/ \|Boundary Dam project] in Saskatchewan Canada.

	~~Flows~~ like [[wind]], [[sunlight]] and [[tidal power]] are [[non-dispatchable source of electricity\|non-dispatchable]] and [[intermittent electricity\|intermittent]], meaning that there is little to no control over when the energy comes. Issues with [[energy storage]] make this a difficult challenge to overcome in using flows. Fuels are ready whenever they're needed. For example, both [[wind]] and [[tidal force\|tides]] have been used for years for sailing ships. The ships go when the flows take them, because "Time and the tide wait for no one."		Primary energy flows like [[wind]], [[sunlight]] and [[tidal power]] are [[non-dispatchable source of electricity\|non-dispatchable]] and [[intermittent electricity\|intermittent]], meaning that there is little to no control over when the energy comes. Issues with [[energy storage]] make this a difficult challenge to overcome in using flows. Fuels are ready whenever they're needed. For example, both [[wind]] and [[tidal force\|tides]] have been used for years for sailing ships. The ships go when the flows take them, because "Time and the tide wait for no one."

	These flows (although not geothermal) tend to take up a large amount of [[renewable footprint \| land]], compared to fuel use. Fuels are very dense. Flows are often, but not always more [[energy cost\|expensive]] than fuels.		These flows (although not geothermal) tend to take up a large amount of [[renewable footprint \| land]], compared to fuel use. Fuels are very dense. Flows are often, but not always more [[energy cost\|expensive]] than fuels.
	While flows have been used for millennia (like [[daylighting]] for light in buildings, or milling using hydropower), the technology necessary to get electricity out of flows tends to be harder to build. For example, it’s easier to make a [[coal-fired power plant]] than to ~~make~~ a [[photovoltaic cell]]. This means that in rapidly developing countries like China, coal ~~is actually growing~~ more rapidly than any of the flows (see [[world primary energy]]).
			While flows have been used for millennia (like [[daylighting]] for light in buildings, or milling using hydropower or wind), the technology necessary to get electricity out of flows tends to be harder to build. For example, it’s easier to develop the technology needed to make a [[coal-fired power plant]] than to manufacture a [[photovoltaic cell]] (let alone mass producing them). This means that in rapidly developing countries like China, coal tends to grow more rapidly than any of the primary energy flows (see [[world primary energy]]).

	==Examples==		==Examples==
	===Flows===		===Primary Energy Flows===
	'''[[Hydroelectricity]]''' uses the flow of water to turn turbines, connected to [[generator]]s, which create electricity. The [[potential energy]] put into this system (water evaporating, condensing, flowing in rivers), comes from the [[sun]], hydro power plants harness the [[kinetic energy]] of an already-moving system.		'''[[Hydroelectricity]]''' uses the flow of water to turn turbines, connected to [[generator]]s, which create electricity. The [[potential energy]] put into this system (water evaporating, condensing, flowing in rivers), comes from the [[sun]], hydro power plants harness the [[kinetic energy]] of an already-moving system.

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	'''[[Solar power]]''' uses the [[radiation]] from the sun in order to create electricity. [[Solar thermal power plant]]s use the [[heat]] from the sun to spin turbines, whereas [[photovoltaic system]]s convert the energy directly.		'''[[Solar power]]''' uses the [[radiation]] from the sun in order to create electricity. [[Solar thermal power plant]]s use the [[heat]] from the sun to spin turbines, whereas [[photovoltaic system]]s convert the energy directly.

	===Fuels===		===Primary Fuels===
	'''[[Petroleum\|Petroleum products]]''' like [[gasoline]], [[Natural gas vehicle\|liquid natural gas]], and [[diesel]] all are used as fuels to power vehicles.		'''[[Petroleum\|Petroleum products]]''' like [[gasoline]], [[Natural gas vehicle\|liquid natural gas]], and [[diesel]] all are used as fuels to power vehicles.

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	Figure 1. Approximately 95% percent of the primary energy in the world comes from fuels like [[oil]], [[coal]] and [[natural gas]]<ref>IEA (2014), "World energy balances", IEA World Energy Statistics and Balances (database). DOI: http://dx.doi.org/10.1787/data-00512-en		Figure 1. Approximately 95% percent of the primary energy in the world comes from fuels like [[oil]], [[coal]] and [[natural gas]]<ref>IEA (2014), "World energy balances", IEA World Energy Statistics and Balances (database). DOI: http://dx.doi.org/10.1787/data-00512-en
	(Accessed February 2015)</ref> (all of which except nuclear fuels produce extensive [[greenhouse gas]]es when used). Most of the rest of the world's primary energy comes from [[hydropower]], although a small fraction is [[wind power]], [[solar power]], [[geothermal energy]], and [[tidal power]]. The amount of electricity that comes from flows increases to about 19% (still mostly hydro) because flows don't have the same limitations of having a [[thermal efficiency]]'s that [[heat engine]]s have and flows are used almost entirely for electricity generation.		(Accessed February 2015)</ref> (all of which except nuclear fuels produce extensive [[greenhouse gas]]es when used). Most of the rest of the world's primary energy comes from [[hydropower]], although a small fraction is [[wind power]], [[solar power]], [[geothermal energy]], and [[tidal power]]. The amount of electricity that comes from primary flows increases to about 20% (still mostly hydro) because flows don't have the same limitations of having a [[thermal efficiency]]'s that [[heat engine]]s have and flows are used almost entirely for electricity generation.

	==References==		==References==
	{{reflist}}		{{reflist}}
	[[Category:Uploaded]]		[[Category:Uploaded]]

Jmdonev: 1 revision imported

2018-07-21T01:13:04Z

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Jmdonev at 21:27, 18 July 2018

2018-07-18T21:27:54Z

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	===Fuel===		===Fuel===
	Most of the world's primary energy (~95%) comes from fuels (see Figure 1). Of these [[primary fuel]]s like [[coal]] and [[natural gas]] are put into power plants. Crude [[oil]] is processed into [[secondary fuel]]s, like [[gasoline]], [[diesel]] and [[kerosene]]. Most cars are propelled by igniting a fuel like gasoline or diesel. Coal, natural gas, gasoline, and diesel are all considered to be fuels, because the energy we take from them is stored discretely inside them, and once we use it up, the fuel is gone. Fuels are [[dispatchable source of electricity\|dispatchable]], which means the energy is available whenever it is needed.		Most of the world's primary energy (90-95%) comes from fuels (see Figure 1). Of these [[primary fuel]]s like [[coal]] and [[natural gas]] are put into power plants. Crude [[oil]] is processed into [[secondary fuel]]s, like [[gasoline]], [[diesel]] and [[kerosene]]. Most cars are propelled by igniting a fuel like gasoline or diesel. Coal, natural gas, gasoline, and diesel are all considered to be fuels, because the energy we take from them is stored discretely inside them, and once we use it up, the fuel is gone. Fuels are [[dispatchable source of electricity\|dispatchable]], which means the energy is available whenever it is needed.

	===Flow===		===Flow===
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	[[Public attitudes towards energy sources\|Public perception]]s of these fuels and flows are complex, but the science is clear: each fuel and flow has its own advantages and drawbacks. Comparing which is the best is not straightforward, and depends on many parameters.		[[Public attitudes towards energy sources\|Public perception]]s of these fuels and flows are complex, but the science is clear: each fuel and flow has its own advantages and drawbacks. Comparing which is the best is not straightforward, and depends on many parameters.

	Flows almost always have fewer [[emission]]s and [[pollution]] than fuels (although nuclear fuels lead to very few emissions). This is especially true of the [[CO2 footprint]], which has led to aggressive pursuit of flows, especially by environmental groups. While there is usually no direct [[pollution vs waste\|waste]] from flow harvesting technologies [[life cycle analysis]] often shows that there is waste that should be taken into consideration. The [[carbon dioxide]] released from harvesting flows is almost always quite a bit less ([[greenhouse gases from ~~hydropower~~]] are a problem, and in theory it's possible to [[carbon capture and storage\|capture and sequester carbon]] dioxide from fossil fuel plants. Although as of 2015 only the [http://www.saskpowerccs.com/ccs-projects/boundary-dam-carbon-capture-project/ \|Boundary Dam project] in Saskatchewan Canada is actually capturing [[Carbon dioxide\|CO2]].		Flows almost always have fewer [[emission]]s and [[pollution]] than fuels (although nuclear fuels lead to very few emissions). This is especially true of the [[CO2 footprint]], which has led to aggressive pursuit of flows, especially by environmental groups. While there is usually no direct [[pollution vs waste\|waste]] from flow harvesting technologies [[life cycle analysis]] often shows that there is waste that should be taken into consideration. The [[carbon dioxide]] released from harvesting flows is almost always quite a bit less ([[greenhouse gases from hydroelectricity]] are a problem, and in theory it's possible to [[carbon capture and storage\|capture and sequester carbon]] dioxide from fossil fuel plants. Although as of 2015 only the [http://www.saskpowerccs.com/ccs-projects/boundary-dam-carbon-capture-project/ \|Boundary Dam project] in Saskatchewan Canada is actually capturing [[Carbon dioxide\|CO2]].

	Flows like [[wind]], [[sunlight]] and [[tidal power]] are [[non-dispatchable source of electricity\|non-dispatchable]] and [[intermittent electricity\|intermittent]], meaning that there is little to no control over when the energy comes. Issues with [[energy storage]] make this a difficult challenge to overcome in using flows. Fuels are ready whenever they're needed. For example, both [[wind]] and [[tidal force\|tides]] have been used for years for sailing ships. The ships go when the flows take them, because "Time and the tide wait for no one."		Flows like [[wind]], [[sunlight]] and [[tidal power]] are [[non-dispatchable source of electricity\|non-dispatchable]] and [[intermittent electricity\|intermittent]], meaning that there is little to no control over when the energy comes. Issues with [[energy storage]] make this a difficult challenge to overcome in using flows. Fuels are ready whenever they're needed. For example, both [[wind]] and [[tidal force\|tides]] have been used for years for sailing ships. The ships go when the flows take them, because "Time and the tide wait for no one."
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	'''[[Uranium]]''' is a nuclear fuel used in [[nuclear reactor\|reactors]] to create electricity.		'''[[Uranium]]''' is a nuclear fuel used in [[nuclear reactor\|reactors]] to create electricity.

	<center><html><iframe style="border:1px solid #cccccc" src="~~http~~://www.energyeducation.ca/simulations/TFC/flows.php" width="520px" height="520px" scrolling='no'></iframe></html></center>		<center><html><iframe style="border:1px solid #cccccc" src="https://www.energyeducation.ca/simulations/TFC/flows.php" width="520px" height="520px" scrolling='no'></iframe></html></center>

	Figure 1. Approximately 95% percent of the primary energy in the world comes from fuels like [[oil]], [[coal]] and [[natural gas]]<ref>IEA (2014), "World energy balances", IEA World Energy Statistics and Balances (database). DOI: http://dx.doi.org/10.1787/data-00512-en		Figure 1. Approximately 95% percent of the primary energy in the world comes from fuels like [[oil]], [[coal]] and [[natural gas]]<ref>IEA (2014), "World energy balances", IEA World Energy Statistics and Balances (database). DOI: http://dx.doi.org/10.1787/data-00512-en

J.williams: 1 revision imported

2015-09-18T16:52:02Z

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Jmdonev at 22:27, 4 September 2015

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	These flows (although not geothermal) tend to take up a large amount of [[renewable footprint \| land]], compared to fuel use. Fuels are very dense. Flows are often, but not always more [[energy cost\|expensive]] than fuels.		These flows (although not geothermal) tend to take up a large amount of [[renewable footprint \| land]], compared to fuel use. Fuels are very dense. Flows are often, but not always more [[energy cost\|expensive]] than fuels.
	While flows have been used for millennia (like [[daylighting]] for light in buildings, or milling using hydropower), the technology necessary to get electricity out of flows tends to be harder to build. For example, it’s easier to make a [[coal-fired power plant]] than to make a [[photovoltaic cell]]. This means that in rapidly developing countries like China, coal is actually growing more rapidly than any of the flows (see [[world primary energy]].		While flows have been used for millennia (like [[daylighting]] for light in buildings, or milling using hydropower), the technology necessary to get electricity out of flows tends to be harder to build. For example, it’s easier to make a [[coal-fired power plant]] than to make a [[photovoltaic cell]]. This means that in rapidly developing countries like China, coal is actually growing more rapidly than any of the flows (see [[world primary energy]]).

	==Examples==		==Examples==

J.williams: 1 revision imported

2015-09-03T18:22:00Z

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Jmdonev at 21:14, 27 August 2015

2015-08-27T21:14:19Z

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	===Fuel===		===Fuel===
	Most of the world's primary energy (~95%) comes from fuels (see ~~figure~~ 1). Of these [[primary fuel]]s like [[coal]] and [[natural gas]] are put into power plants. Crude [[oil]] is processed into [[secondary fuel]]s, like [[gasoline]], [[diesel]] and [[kerosene]]. Most cars are propelled by igniting a fuel like gasoline or diesel. Coal, natural gas, gasoline, and diesel are all considered to be fuels, because the energy we take from them is stored discretely inside them, and once we use it up, the fuel is gone. Fuels are [[dispatchable source of electricity\|dispatchable]], which means the energy is available whenever it is needed.		Most of the world's primary energy (~95%) comes from fuels (see Figure 1). Of these [[primary fuel]]s like [[coal]] and [[natural gas]] are put into power plants. Crude [[oil]] is processed into [[secondary fuel]]s, like [[gasoline]], [[diesel]] and [[kerosene]]. Most cars are propelled by igniting a fuel like gasoline or diesel. Coal, natural gas, gasoline, and diesel are all considered to be fuels, because the energy we take from them is stored discretely inside them, and once we use it up, the fuel is gone. Fuels are [[dispatchable source of electricity\|dispatchable]], which means the energy is available whenever it is needed.

	===Flow===		===Flow===
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	[[Public attitudes towards energy sources\|Public perception]]s of these fuels and flows are complex, but the science is clear: each fuel and flow has its own advantages and drawbacks. Comparing which is the best is not straightforward, and depends on many parameters.		[[Public attitudes towards energy sources\|Public perception]]s of these fuels and flows are complex, but the science is clear: each fuel and flow has its own advantages and drawbacks. Comparing which is the best is not straightforward, and depends on many parameters.

	Flows almost always have fewer [[emission]]s and [[pollution]] than fuels (although nuclear fuels lead to very few emissions). This is especially true of the [[CO2 footprint]], which has led to aggressive pursuit of flows, especially by environmental groups. While there is usually no direct [[pollution vs waste\|waste]] from flow harvesting technologies [[life cycle analysis]] often shows that there is waste that should be taken into consideration. The [[carbon dioxide]] released from harvesting flows is almost always quite a bit less ([[greenhouse ~~gasses~~ from hydropower]] are a problem, and in theory it's possible to [[~~CCS~~\|capture and sequester carbon]] dioxide from fossil fuel plants. Although as of 2015 only the [http://www.saskpowerccs.com/ccs-projects/boundary-dam-carbon-capture-project/ \|Boundary Dam project] in Saskatchewan Canada is actually capturing [[Carbon dioxide\|CO2]].		Flows almost always have fewer [[emission]]s and [[pollution]] than fuels (although nuclear fuels lead to very few emissions). This is especially true of the [[CO2 footprint]], which has led to aggressive pursuit of flows, especially by environmental groups. While there is usually no direct [[pollution vs waste\|waste]] from flow harvesting technologies [[life cycle analysis]] often shows that there is waste that should be taken into consideration. The [[carbon dioxide]] released from harvesting flows is almost always quite a bit less ([[greenhouse gases from hydropower]] are a problem, and in theory it's possible to [[carbon capture and storage\|capture and sequester carbon]] dioxide from fossil fuel plants. Although as of 2015 only the [http://www.saskpowerccs.com/ccs-projects/boundary-dam-carbon-capture-project/ \|Boundary Dam project] in Saskatchewan Canada is actually capturing [[Carbon dioxide\|CO2]].

	Flows like [[wind]], [[sunlight]] and [[tidal power]] are [[non-dispatchable source of electricity\|non-dispatchable]] and [[intermittent electricity\|intermittent]], meaning that there is little to no control over when the energy comes. Issues with [[energy storage]] make this a difficult challenge to overcome in using flows. Fuels are ready whenever they're needed. For example, both [[wind]] and [[tidal force\|tides]] have been used for years for sailing ships. The ships go when the flows take them, because "Time and the tide wait for no one."		Flows like [[wind]], [[sunlight]] and [[tidal power]] are [[non-dispatchable source of electricity\|non-dispatchable]] and [[intermittent electricity\|intermittent]], meaning that there is little to no control over when the energy comes. Issues with [[energy storage]] make this a difficult challenge to overcome in using flows. Fuels are ready whenever they're needed. For example, both [[wind]] and [[tidal force\|tides]] have been used for years for sailing ships. The ships go when the flows take them, because "Time and the tide wait for no one."

J.williams: 1 revision imported

2015-08-26T21:31:07Z

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Jmdonev at 21:00, 15 August 2015

2015-08-15T21:00:18Z

New page

[[category:371 topics]]
[[category:Lecture 1B_Human_effects]]
[[Category:Done 2015-08-21]]
[[category:fuels]]
[[category:energy flows]]
<onlyinclude>Different types of [[primary energy]] fall into two main categories: '''[[fuel]]s and [[flow]]s'''. '''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 [[tidal power|tides]].</onlyinclude><ref>Wolfson, "Earth's Energy Endowment," ''Energy, Environment, and Climate,'' Second edition. London, England: Norton, 2012, chapter 1.6</ref> Once the energy is extracted from a fuel, it's gone, but extracting the energy from a flow is different. Natural processes put energy back into flows over time making them [[renewable and sustainable energy|renewable]].

===Fuel===
Most of the world's primary energy (~95%) comes from fuels (see figure 1). Of these [[primary fuel]]s like [[coal]] and [[natural gas]] are put into power plants. Crude [[oil]] is processed into [[secondary fuel]]s, like [[gasoline]], [[diesel]] and [[kerosene]]. Most cars are propelled by igniting a fuel like gasoline or diesel. Coal, natural gas, gasoline, and diesel are all considered to be fuels, because the energy we take from them is stored discretely inside them, and once we use it up, the fuel is gone. Fuels are [[dispatchable source of electricity|dispatchable]], which means the energy is available whenever it is needed.

===Flow===
Power sources like [[hydroelectricity]], [[tidal power]], [[wind power]], and [[solar power]] take advantage of energy flows, where energy is harnessed from natural energy sources. An energy flow differs from a fuel because an energy flow is simply a movement of energy from one place to another, whereas a fuel is a substance that stores energy.

==Why it matters==

Both fuels and flows can be [[renewable and sustainable energy|sustainable]], but for the most part, only flows are [[renewable and sustainable energy|renewable]]. For a discussion of why this distinction is important please see [[renewable and sustainable energy]].

[[Public attitudes towards energy sources|Public perception]]s of these fuels and flows are complex, but the science is clear: each fuel and flow has its own advantages and drawbacks. Comparing which is the best is not straightforward, and depends on many parameters.

Flows almost always have fewer [[emission]]s and [[pollution]] than fuels (although nuclear fuels lead to very few emissions). This is especially true of the [[CO2 footprint]], which has led to aggressive pursuit of flows, especially by environmental groups. While there is usually no direct [[pollution vs waste|waste]] from flow harvesting technologies [[life cycle analysis]] often shows that there is waste that should be taken into consideration. The [[carbon dioxide]] released from harvesting flows is almost always quite a bit less ([[greenhouse gasses from hydropower]] are a problem, and in theory it's possible to [[CCS|capture and sequester carbon]] dioxide from fossil fuel plants. Although as of 2015 only the [http://www.saskpowerccs.com/ccs-projects/boundary-dam-carbon-capture-project/ |Boundary Dam project] in Saskatchewan Canada is actually capturing [[Carbon dioxide|CO2]].

Flows like [[wind]], [[sunlight]] and [[tidal power]] are [[non-dispatchable source of electricity|non-dispatchable]] and [[intermittent electricity|intermittent]], meaning that there is little to no control over when the energy comes. Issues with [[energy storage]] make this a difficult challenge to overcome in using flows. Fuels are ready whenever they're needed. For example, both [[wind]] and [[tidal force|tides]] have been used for years for sailing ships. The ships go when the flows take them, because "Time and the tide wait for no one."

These flows (although not geothermal) tend to take up a large amount of [[renewable footprint | land]], compared to fuel use. Fuels are very dense. Flows are often, but not always more [[energy cost|expensive]] than fuels.
While flows have been used for millennia (like [[daylighting]] for light in buildings, or milling using hydropower), the technology necessary to get electricity out of flows tends to be harder to build. For example, it’s easier to make a [[coal-fired power plant]] than to make a [[photovoltaic cell]]. This means that in rapidly developing countries like China, coal is actually growing more rapidly than any of the flows (see [[world primary energy]].

==Examples==
===Flows===
'''[[Hydroelectricity]]''' uses the flow of water to turn turbines, connected to [[generator]]s, which create electricity. The [[potential energy]] put into this system (water evaporating, condensing, flowing in rivers), comes from the [[sun]], hydro power plants harness the [[kinetic energy]] of an already-moving system.

'''[[Wind power]]''' uses [[wind]] currents put into motion by the sun, harnessing their kinetic energy to spin turbines, then generators, creating electricity.

'''[[Solar power]]''' uses the [[radiation]] from the sun in order to create electricity. [[Solar thermal power plant]]s use the [[heat]] from the sun to spin turbines, whereas [[photovoltaic system]]s convert the energy directly.

===Fuels===
'''[[Petroleum|Petroleum products]]''' like [[gasoline]], [[Natural gas vehicle|liquid natural gas]], and [[diesel]] all are used as fuels to power vehicles.

'''[[Coal]]''' is a fossil fuel that is burned to create electricity in much of the world. It's currently the fastest growing [[primary energy]] source.

'''[[Uranium]]''' is a nuclear fuel used in [[nuclear reactor|reactors]] to create electricity.

<center><html><iframe style="border:1px solid #cccccc" src="http://www.energyeducation.ca/simulations/TFC/flows.php" width="520px" height="520px" scrolling='no'></iframe></html></center>

Figure 1. Approximately 95% percent of the primary energy in the world comes from fuels like [[oil]], [[coal]] and [[natural gas]]<ref>IEA (2014), "World energy balances", IEA World Energy Statistics and Balances (database). DOI: http://dx.doi.org/10.1787/data-00512-en
(Accessed February 2015)</ref> (all of which except nuclear fuels produce extensive [[greenhouse gas]]es when used). Most of the rest of the world's primary energy comes from [[hydropower]], although a small fraction is [[wind power]], [[solar power]], [[geothermal energy]], and [[tidal power]]. The amount of electricity that comes from flows increases to about 19% (still mostly hydro) because flows don't have the same limitations of having a [[thermal efficiency]]'s that [[heat engine]]s have and flows are used almost entirely for electricity generation.

==References==
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[[Category:Uploaded]]