View source for Natural gas power plant

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[[Category:Done 2018-07-20]] 
[[File:Surgut.jpg|300px|thumb|Figure 1. The Surgut-2 power plant in Russia is the largest natural gas power plant in the world.<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/2/2e/Surgut_%28060%29.jpg</ref>]]

<onlyinclude>'''Natural gas power plants''' [[generate electricity]] by burning [[natural gas]] as their [[fuel]]. There are many types of natural gas power plants which all generate electricity, but serve different purposes.</onlyinclude> All natural gas plants use a [[gas turbine]]; natural gas is added, along with a stream of air, which [[combustion|combusts]] and expands through this turbine causing a [[generator]] to spin a magnet, making [[electricity]]. There is [[waste heat]] that comes from this process, because of the [[second law of thermodynamics]]. Some natural gas plants use this waste heat as well, which is explained below. 

Natural gas power plants are cheap and quick to build. They also have very high [[efficiency|thermodynamic efficiencies]] compared to other [[power plant]]s. Burning of natural gas produces fewer [[pollutant]]s like [[NOx]], [[SOx]] and [[particulate matter]] than [[coal]] and [[oil]].<ref>Environmental Law Institute Research Report, "Cleaner Power the benefits and costs of moving from coal generation to modern power technologies", 2nd edition, May 2001.</ref> On the other hand, natural gas plants have significantly higher [[emissions]] than a [[nuclear power plant]]. This means that [[air quality]] tends to improve (ie. reduces [[smog]]) when switching to natural gas plants from coal plants—but [[nuclear power]] does even more to improve air quality. 

Despite the improved air quality, natural gas plants significantly contribute to [[climate change]], and that contribution is growing (see [[pollutant vs greenhouse gas]]).<ref>Carbon dioxide and methane emissions are not included in air quality. Burning natural gas releases both, therefore, it contributes to climate change, while improving air quality.</ref> Natural gas power plants produce considerable [[carbon dioxide]], although less than coal plants do. On the other hand, the process of getting natural gas from where it's mined to the power plants leads to considerable release of [[methane]] (natural gas that leaks into the [[atmosphere]]). As long as natural gas plants are used to produce electricity their emissions will continue to warm the planet in dangerous ways. 

==Types==
There are two types of natural gas power plants: '''[[Simple cycle gas plant]]s''' and '''[[combined cycle gas plant]]s'''. The former consists of a gas turbine connected to a generator and the latter consists of a simple cycle plant, combined with another [[external combustion engine]], operating on the [[Rankine cycle]]—hence its name "combined cycle". 

The simple cycle is simpler but less [[efficiency|efficient]] than the combined cycle. However, simple cycle plants are able to [[dispatchable source of electricity|dispatch faster]] than [[coal-fired power plant]]s or nuclear plants. This means they can be turned on or off faster in order to meet societies electricity needs.<ref>T. Johnson and D. Keith, "Fossil electricity and CO2 sequestration: how natural gas prices, initial conditions and retrofits determine the cost of controlling CO2 emissions", Energy Policy, vol. 32, no. 3, pp. 367-382, 2004.</ref>  Often needed on the [[grid]] with [[wind power]] and [[solar power]], its purpose is to meet the fluctuating [[electricity]] needs of society, known as [[peaking power]]. Combined cycle plants are more efficient  because it makes use of the hot exhaust gases that would otherwise be dispelled from the system. These exhaust gases are used to [[boiling point|boil]] [[water]] into [[steam]]—which can then spin another turbine and generate more electricity. The [[thermal efficiency]] of the combined cycle can get up to 60%.<ref>Siemens, ''Efficiency Record of Combined Cycle Power Plant'' [Online], Available: http://www.siemens.com/innovation/en/news/2011/efficiency-record-of-combined-cycle-power-plant.htm</ref> Moreover, these plants produce one third of the [[waste heat]] of a plant with a 33% efficiency (like a typical [[nuclear power plant]] or an older coal power plant). 
See the [[thermal efficiency]] page for more information on this.

The cost of a combined cycle plants is generally higher since they cost more to build and run. The EIA estimated that for a simple cycle plant the cost is about US$389/[[watt|kW]], whereas combined cycle plants are US$500-550/kW.<ref>Paul Breeze. (2005) ''Power Generation Technologies'' [Online Book], Available: https://books.google.co.uk/books?id=D9qSDgTbRZoC&pg=PA59&dq=%22Simple+cycle+combustion+turbine%22&hl=en&sa=X&ei=8A4sUYaND4vA9QSSqIDIDw#v=onepage&q=%22Simple%20cycle%20combustion%20turbine%22&f=false</ref>

 
The use of natural gas accounts for around 23% of the world's electricity generation (see the [[Natural gas power plant#World Electricity Generation: Natural Gas|data visualization below]]). This is second only to [[coal]], and the fraction that is natural gas is expected to grow in coming years. This means that natural gas's contribution to climate change will continue to grow.


==Operation==

Natural gas turbines are theoretically simple and have three main parts as seen in Figure 2:<ref name=hsw>Brain, Marshall.  "How Gas Turbine Engines Work"  01 April 2000.  HowStuffWorks.com. [Online], Available: <http://science.howstuffworks.com/transport/flight/modern/turbine.htm>  28 May 2015.</ref>

#'''Compressor:''' Takes in air from outside of the turbine and increases its pressure. 
#'''Combustor:''' [[Combustion|Burns the fuel]] and produces high pressure and high [[velocity]] gas.
#'''Turbine:''' Extracts the energy from the gas coming from the combustor.


[[File:natgasturb.png|thumb|800px|center|Figure 2. A diagram of a gas turbine engine.<ref>Wikimedia Commons [Online], Available: https://upload.wikimedia.org/wikipedia/commons/4/4c/Jet_engine.svg</ref>]]

===Combined cycle===
The simple cycle stops here, however, the combined cycle extends beyond this to use more of the energy created in the combustion. The exhaust gases are made to flow towards the next unit, called the '''heat recovery steam generator''' (HRSG).<ref name=wart>Wartsila, ''Combined Cycle Plant for Power Generation: Introduction'' [Online], Available: http://www.wartsila.com/power-plants/learning-center/technical-comparisons/combined-cycle-plant-for-power-generation-introduction</ref> The HRSG is essentially a [[heat exchanger]], in which the hot gases [[boiling point|boil]] pre-heated water into steam. The steam then expands through a turbine, generating electricity. Once the steam has passed through, it condenses and is recycled through.

===Cogeneration===
Natural gas plants produce [[waste heat]], like all [[heat engine]]s. Sometimes this waste heat is captured to heat homes or for industrial uses. This process is known as [[cogeneration]].

==World Electricity Generation: Natural Gas==

The map below shows which primary energy different countries use to generate their electricity from. Natural gas is seen in red. Click on the region to zoom into a group of countries, then click on the country to see where its electricity comes from. Notable countries include the United States, Russia, Saudi Arabia, and Iran. 

<html><iframe class='charts-iframe' id='world-energy'></iframe></html>

==For Further Reading==
*[[Natural gas]]
*[[Natural gas formation]]
*[[Simple cycle gas plant]]
*[[Combined cycle gas plant]]
*[[Pollutant]] vs [[Greenhouse gas]]
*Or explore a [[Special:Random|random page]]

==References==
{{reflist}}
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