View source for Chemistry:Power station

{{short description|Facility generating electric power}}
{{Power engineering}}
[[File:Greater Cape Town 12.02.2007 16-41-31.2007 16-41-33.JPG|thumb|upright=1.2|The Athlone Power Station in Cape Town, South Africa]]
[[File:DSCN1028.JPG|right|thumb|upright=1.2|Hydroelectric power station at Gabčíkovo Dam, Slovakia]] thumb|upright=1.2|Hydroelectric power station at [[Glen Canyon Dam, Page, Arizona]]

A '''power station''', also referred to as a '''power plant''' and sometimes '''generating station''' or '''generating plant''', is an industrial facility for the [[Engineering:Electricity generation|generation]] of [[Physics:Electric power|electric power]]. Power stations are generally connected to an [[Engineering:Electrical grid|electrical grid]].

Many power stations contain one or more [[Engineering:Electric generator|generators]], rotating machine that converts mechanical power into [[Physics:Three-phase electric power|three-phase electric power]]. The relative motion between a [[Physics:Magnetic field|magnetic field]] and a [[Physics:Electrical conductor|conductor]] creates an [[Physics:Electric current|electric current]].

The energy source harnessed to turn the generator varies widely. Most power stations in the world burn fossil fuels such as [[Earth:Coal|coal]], [[Chemistry:Petroleum|oil]], and [[Chemistry:Natural gas|natural gas]] to generate electricity. Low-carbon power sources include [[Physics:Nuclear power|nuclear power]], and use of [[Engineering:Renewable energy|renewables]] such as [[Engineering:Solar power|solar]], wind, [[Earth:Geothermal power|geothermal]], and hydroelectric.

==History==
In early 1871 Belgian inventor Zénobe Gramme invented a generator powerful enough to produce power on a commercial scale for industry.<ref>{{Cite book |last=Thompson |first=Silvanus Phillips |url=https://archive.org/details/dynamoelectricm01thomgoog |title=Dynamo-electric Machinery: A Manual for Students of Electrotechnics |publisher=E. & F. N. Spon |year=1888 |location=London |page=[https://archive.org/details/dynamoelectricm01thomgoog/page/n158 140]}}</ref>

In 1878, a hydroelectric power station was designed and built by William, Lord Armstrong at Cragside, {{wipe|England}}. It used water from lakes on his estate to power Siemens [[Engineering:Dynamo|dynamo]]s. The electricity supplied power to lights, heating, produced hot water, ran an elevator as well as labor-saving devices and farm buildings.<ref>{{Cite news |title=Hydro-electricity restored to historic Northumberland home |work=BBC News |date=27 February 2013 |url=https://www.bbc.co.uk/news/uk-england-tyne-21586177 |access-date=21 July 2018 |archive-date=29 December 2019 |archive-url=https://web.archive.org/web/20191229044113/https://www.bbc.co.uk/news/uk-england-tyne-21586177 |url-status=live }}</ref>

In January 1882 the world's first public [[Finance:Coal-fired power station|coal-fired power station]], the Edison Electric Light Station, was built in London, a project of [[Biography:Thomas Edison|Thomas Edison]] organized by Edward Johnson. A Babcock & Wilcox boiler powered a {{convert|125|hp|order=flip|abbr=in}} steam engine that drove a {{convert|27|long ton|tonne|order=flip|adj=on}} generator. This supplied electricity to premises in the area that could be reached through the [[Engineering:Culvert|culvert]]s of the viaduct without digging up the road, which was the monopoly of the gas companies. The customers included the City Temple and the Old Bailey. Another important customer was the Telegraph Office of the General Post Office, but this could not be reached through the culverts. Johnson arranged for the supply cable to be run overhead, via Holborn Tavern and Newgate.<ref>{{Citation |last=Jack Harris |title=The electricity of Holborn |date=14 January 1982 |url=https://books.google.com/books?id=bfVKt7UzjnEC&pg=PA89 |work=New Scientist |access-date=21 November 2015 |archive-date=4 February 2023 |archive-url=https://web.archive.org/web/20230204142006/https://books.google.com/books?id=bfVKt7UzjnEC&pg=PA89 |url-status=live }}</ref>

In September 1882 in New York, the Pearl Street Station was established by Edison to provide electric lighting in the lower Manhattan Island area. The station ran until destroyed by fire in 1890. The station used reciprocating [[Physics:Steam engine|steam engine]]s to turn direct-current generators. Because of the DC distribution, the service area was small, limited by voltage drop in the feeders. In 1886 George Westinghouse began building an alternating current system that used a [[Engineering:Transformer|transformer]] to step up voltage for long-distance transmission and then stepped it back down for indoor lighting, a more efficient and less expensive system which is similar to modern systems. The [[Physics:War of the currents|war of the currents]] eventually resolved in favor of AC distribution and utilization, although some DC systems persisted to the end of the 20th century. DC systems with a service radius of a mile (kilometer) or so were necessarily smaller, less efficient of fuel consumption, and more labor-intensive to operate than much larger central AC generating stations.

[[File:Edison Central Station Dynamos and Engine.jpg|thumb|Dynamos and engine installed at Edison General Electric Company, New York 1895]]

AC systems used a wide range of [[Physics:Utility frequency|frequencies]] depending on the type of load; lighting load using higher frequencies, and traction systems and heavy motor load systems preferring lower frequencies. The economics of central station generation improved greatly when unified light and power systems, operating at a common frequency, were developed. The same generating plant that fed large industrial loads during the day, could feed commuter railway systems during rush hour and then serve lighting load in the evening, thus improving the system [[Engineering:Load factor (electrical)|load factor]] and reducing the cost of electrical energy overall. Many exceptions existed, generating stations were dedicated to power or light by the choice of frequency, and rotating [[Engineering:Frequency changer|frequency changer]]s and rotating converters were particularly common to feed electric railway systems from the general lighting and power network.

Throughout the first few decades of the 20th century central stations became larger, using higher steam pressures to provide greater efficiency, and relying on interconnections of multiple generating stations to improve reliability and cost. High-voltage AC transmission allowed hydroelectric power to be conveniently moved from distant waterfalls to city markets. The advent of the [[Engineering:Steam turbine|steam turbine]] in central station service, around 1906, allowed great expansion of generating capacity. Generators were no longer limited by the power transmission of belts or the relatively slow speed of reciprocating engines, and could grow to enormous sizes. For example, Sebastian Ziani de Ferranti planned what would have reciprocating steam engine ever built for a proposed new central station, but scrapped the plans when turbines became available in the necessary size. Building power systems out of central stations required combinations of engineering skill and financial acumen in equal measure. Pioneers of central station generation include George Westinghouse and Samuel Insull in the United States, Ferranti and Charles Hesterman Merz in UK, and many others<ref>{{Cite web |date=1 October 2022 |title=History of Power: The Evolution of the Electric Generation Industry |url=https://www.powermag.com/history-of-power-the-evolution-of-the-electric-generation-industry/ |url-status=live |archive-url=https://web.archive.org/web/20230128050002/https://www.powermag.com/history-of-power-the-evolution-of-the-electric-generation-industry/ |archive-date=28 January 2023 |access-date=27 February 2023 |website=Power}}</ref>.{{Citation needed|date=July 2021}}


==Thermal power stations==
{{Main|Physics:Thermal power station}}
[[File:Dampfturbine Laeufer01.jpg|thumb|upright|Rotor of a modern steam turbine, used in a power station]]
In thermal power stations, mechanical power is produced by a [[Physics:Heat engine|heat engine]] that transforms [[Physics:Thermal energy|thermal energy]], often from [[Physics:Combustion|combustion]] of a fuel, into rotational energy. Most thermal power stations produce steam, so they are sometimes called steam power stations. Not all thermal energy can be transformed into mechanical power, according to the [[Physics:Second law of thermodynamics|second law of thermodynamics]]; therefore, there is always heat lost to the environment. If this loss is employed as useful heat, for industrial processes or [[Physics:District heating|district heating]], the power plant is referred to as a [[Physics:Cogeneration|cogeneration]] power plant or CHP (combined heat-and-power) plant. In countries where district heating is common, there are dedicated heat plants called [[Engineering:Heat-only boiler station|heat-only boiler station]]s. An important class of power stations in the Middle East uses by-product heat for the [[Chemistry:Desalination|desalination]] of water.

The efficiency of a thermal power cycle is limited by the maximum working fluid temperature produced. The efficiency is not directly a function of the fuel used. For the same steam conditions, coal-, nuclear- and gas power plants all have the same theoretical efficiency. Overall, if a system is on constantly (base load) it will be more efficient than one that is used intermittently (peak load). Steam turbines generally operate at higher efficiency when operated at full capacity.

Besides use of reject heat for process or district heating, one way to improve overall efficiency of a power plant is to combine two different thermodynamic cycles in a [[Physics:Combined cycle|combined cycle]] plant. Most commonly, [[Physics:Exhaust gas|exhaust gas]]es from a gas turbine are used to generate steam for a boiler and a steam turbine. The combination of a "top" cycle and a "bottom" cycle produces higher overall efficiency than either cycle can attain alone.

In 2018, Inter RAO UES and [https://g.esgcc.com.cn/ State Grid] {{Webarchive|url=https://web.archive.org/web/20211221190902/https://g.esgcc.com.cn/ |date=21 December 2021 }} planned to build an 8-GW thermal power plant, <ref>{{cite news|url=http://www.mofcom.gov.cn/article/i/jyjl/e/201807/20180702769118.shtml|title=China and Russia accelerate pace of power cooperation|date=2018-07-24|publisher=Ministry of Commerce|access-date=29 July 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204142009/http://www.mofcom.gov.cn/404.shtml|url-status=live}}</ref> which's the largest coal-fired power plant construction project in {{wipe|Russia}}.<ref>{{cite news|url=http://www.cankaoxiaoxi.com/finance/20180604/2276134.shtml|title=Inter RAO UES cooperates with State Grid Corporation of China|date=2018-06-04|publisher=Reference News|access-date=29 July 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204142011/http://www.cankaoxiaoxi.com/finance/20180604/2276134.shtml|url-status=live}}</ref>
===Classification===
[[File:Power station in blocks.jpg|upright=2.35|thumb|Modular block overview of a power station. Dashed lines show special additions like combined cycle and cogeneration or optional storage.]]
[[File:DTE St Clair.jpg|thumb|right|St. Clair Power Plant, a large coal-fired generating station in Michigan, {{wipe|United States}}]]
[[File:Ikata Nuclear Powerplant.JPG|thumb|Ikata Nuclear Power Plant, {{wipe|Japan}}]]
[[File:Martinlaakson voimalaitos.JPG|thumb|A large gas and coal power plant in Martinlaakso, Vantaa, Finland]]
[[File:NesjavellirPowerPlant edit2.jpg|thumb|Nesjavellir Geothermal Power Station, Iceland]]

====By heat source====
* Fossil-fuel power stations may also use a steam turbine generator or in the case of natural [[Chemistry:Gas-fired power plant|gas-fired power plant]]s may use a [[Engineering:Gas turbine|combustion turbine]]. A coal-fired power station produces heat by burning coal in a steam boiler. The steam drives a [[Engineering:Steam turbine|steam turbine]] and [[Engineering:Electric generator|generator]] that then produces [[Physics:Electricity|electricity]]. The waste products of combustion include ash, [[Chemistry:Sulfur dioxide|sulfur dioxide]], nitrogen oxides, and [[Chemistry:Carbon dioxide|carbon dioxide]]. Some of the gases can be removed from the waste stream to reduce pollution. 
* [[Engineering:Nuclear power plant|Nuclear power plant]]s<ref>[http://www.iaea.org/cgi-bin/db.page.pl/pris.oprconst.htm Nuclear Power Plants Information] {{Webarchive|url=https://web.archive.org/web/20050213081431/http://www.iaea.org/cgi-bin/db.page.pl/pris.oprconst.htm |date=13 February 2005 }}, by [[Organization:International Atomic Energy Agency|International Atomic Energy Agency]]</ref> use the heat generated in a [[Physics:Nuclear reactor|nuclear reactor]]'s core (by the [[Physics:Nuclear fission|fission]] process) to create steam which then operates a steam turbine and generator. About 20 percent of electric generation in the USA is produced by nuclear power plants.
* [[Earth:Geothermal power|Geothermal power]] plants use steam extracted from hot underground rocks. These rocks are heated by the decay of radioactive material in the Earth's core.<ref>{{Cite web |last=Roberts |first=David |date=2020-10-21 |title=Geothermal energy is poised for a big breakout |url=https://www.vox.com/energy-and-environment/2020/10/21/21515461/renewable-energy-geothermal-egs-ags-supercritical |access-date=2022-04-13 |website=Vox |language=en |archive-date=4 February 2023 |archive-url=https://web.archive.org/web/20230204142009/https://www.vox.com/energy-and-environment/2020/10/21/21515461/renewable-energy-geothermal-egs-ags-supercritical |url-status=live }}</ref>
* [[Biology:Biomass#Energy|Biomass-fuelled power plants]] may be fuelled by [[Biology:Bagasse|waste from sugar cane]], [[Engineering:Incineration|municipal solid waste]], landfill [[Chemistry:Methane|methane]], or other forms of [[Biology:Biomass|biomass]].
* In integrated [[Engineering:Steel mill|steel mill]]s, [[Chemistry:Blast furnace gas|blast furnace exhaust gas]] is a low-cost, although low-energy-density, fuel.
* [[Physics:Cogeneration|Waste heat from industrial processes]] is occasionally concentrated enough to use for power generation, usually in a steam boiler and turbine.
* [[Physics:Solar thermal energy|Solar thermal]] electric plants use sunlight to boil water and produce steam which turns the generator.
* [[Physics:Combined cycle hydrogen power plant|Hydrogen power plant]]s can use [[Engineering:Green hydrogen|green hydrogen]] from [[Physics:Electrolysis of water|electrolysis]] to help balance supply and demand from [[Engineering:Variable renewable energy|Variable renewable energy]] sources.<ref>{{cite magazine|url=https://www.powermag.com/ready-for-the-energy-transition-hydrogen-considerations-for-combined-cycle-power-plants/|title=Ready for the Energy Transition: Hydrogen Considerations for Combined Cycle Power Plants|first=Sebastian|last=Mulder|date=Oct 29, 2021|magazine=Power}}</ref>

====By prime mover====
A prime mover is a machine that converts energy of various forms into energy of motion.
* [[Engineering:Steam turbine|Steam turbine]] plants use the dynamic pressure generated by expanding steam to turn the blades of a turbine. Almost all large non-hydro plants use this system. About 90 percent of all electric power produced in the world is through use of steam turbines.<ref name="Wiser">{{Cite book |last=Wiser |first=Wendell H. |url=https://books.google.com/books?id=UmMx9ixu90kC&pg=PA190 |title=Energy resources: occurrence, production, conversion, use |publisher=Birkhäuser |year=2000 |isbn=978-0-387-98744-6 |page=190 |access-date=21 November 2015 |archive-date=23 January 2023 |archive-url=https://web.archive.org/web/20230123202054/https://books.google.com/books?id=UmMx9ixu90kC&pg=PA190 |url-status=live }}</ref>
* [[Engineering:Gas turbine|Gas turbine]] plants use the dynamic pressure from flowing gases (air and combustion products) to directly operate the turbine. Natural-gas fuelled (and oil fueled) combustion turbine plants can start rapidly and so are used to supply "peak" energy during periods of high demand, though at higher cost than base-loaded plants. These may be comparatively small units, and sometimes completely unmanned, being remotely operated. This type was pioneered by the UK, Princetown<ref>[http://www.swehs.co.uk/docs/news13su.html SWEB's Pocket Power Stations<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20060504055822/http://www.swehs.co.uk/docs/news13su.html |date=4 May 2006 }}</ref> being the world's first, commissioned in 1959.
* [[Physics:Combined cycle|Combined cycle]] plants have both a gas turbine fired by natural gas, and a steam boiler and steam turbine which use the hot exhaust gas from the gas turbine to produce electricity. This greatly increases the overall efficiency of the plant, and many new baseload power plants are combined cycle plants fired by natural gas.
* Internal combustion [[Engineering:Reciprocating engine|reciprocating engine]]s are used to provide power for isolated communities and are frequently used for small cogeneration plants. Hospitals, office buildings, industrial plants, and other critical facilities also use them to provide backup power in case of a power outage. These are usually fuelled by diesel oil, heavy oil, [[Chemistry:Natural gas|natural gas]], and [[Chemistry:Landfill gas|landfill gas]].
* [[Engineering:Gas turbine#Microturbines|Microturbines]], [[Physics:Stirling engine|Stirling engine]] and internal combustion reciprocating engines are low-cost solutions for using opportunity fuels, such as [[Chemistry:Landfill gas|landfill gas]], digester gas from water treatment plants and waste gas from oil production.{{Citation needed|date=July 2021}}

====By duty====
Power plants that can be dispatched (scheduled) to provide energy to a system include:
* Base load power plants run nearly continually to provide that component of system load that does not vary during a day or week. Baseload plants can be highly optimized for low fuel cost, but may not start or stop quickly during changes in system load. Examples of base-load plants would include large modern coal-fired and nuclear generating stations, or hydro plants with a predictable supply of water.
* [[Engineering:Peaking power plant|Peaking power plant]]s meet the daily peak load, which may only be for one or two hours each day. While their incremental operating cost is always higher than base load plants, they are required to ensure security of the system during load peaks. Peaking plants include simple cycle gas turbines and reciprocating internal combustion engines, which can be started up rapidly when system peaks are predicted. Hydroelectric plants may also be designed for peaking use.  
* [[Engineering:Load following power plant|Load following power plant]]s can economically follow the variations in the daily and weekly load, at lower cost than peaking plants and with more flexibility than baseload plants.

Non-dispatchable plants include such sources as wind and solar energy; while their long-term contribution to system energy supply is predictable, on a short-term (daily or hourly) base their energy must be used as available since generation cannot be deferred. Contractual arrangements ("take or pay") with independent power producers or system interconnections to other networks may be effectively non-dispatchable.{{Citation needed|date=July 2021}}

===Cooling towers===
{{main|Physics:Cooling tower}}
[[File:RatcliffePowerPlantBlackAndWhite.jpg|thumb|Cooling towers showing evaporating water at Ratcliffe-on-Soar Power Station, {{wipe|United Kingdom}}]]
[[File:Cooling tower power station Dresden.jpg|thumb|"Camouflaged" natural draft wet cooling tower]]

All thermal power plants produce [[Astronomy:Waste heat|waste heat]] energy as a byproduct of the useful electrical energy produced. The amount of waste heat energy equals or exceeds the amount of energy converted into useful electricity{{Clarify|date=October 2021}}. Gas-fired power plants can achieve as much as 65% conversion efficiency, while coal and oil plants achieve around 30–49%. The waste heat produces a temperature rise in the atmosphere, which is small compared to that produced by greenhouse-gas emissions from the same power plant. Natural draft wet [[Physics:Cooling tower|cooling tower]]s at many nuclear power plants and large fossil-fuel-fired power plants use large [[Hyperboloid structure|hyperboloid]] [[Engineering:Chimney|chimney]]-like structures (as seen in the image at the right) that release the waste heat to the ambient atmosphere by the [[Physics:Evaporation|evaporation]] of water.

However, the mechanical induced-draft or forced-draft wet cooling towers in many large thermal power plants, nuclear power plants, fossil-fired power plants, [[Chemistry:Oil refinery|petroleum refineries]], [[Chemistry:Petrochemical|petrochemical plants]], [[Earth:Geothermal power|geothermal]], [[Biology:Biomass|biomass]] and waste-to-energy plants use fans to provide air movement upward through down coming water and are not hyperboloid chimney-like structures. The induced or forced-draft cooling towers are typically rectangular, box-like structures filled with a material that enhances the mixing of the upflowing air and the down-flowing water.<ref>{{Cite book |editor=J. C. Hensley |url=http://spxcooling.com/en/library/detail/cooling-tower-fundamentals/ |title=Cooling Tower Fundamentals |publisher=SPX Cooling Technologies |year=2006 |edition=2nd |access-date=13 September 2007 |archive-date=18 June 2013 |archive-url=https://web.archive.org/web/20130618074805/http://spxcooling.com/en/library/detail/cooling-tower-fundamentals |url-status=live }}</ref><ref name="Beychok">{{Cite book |last=Beychok, Milton R. |title=Aqueous Wastes from Petroleum and Petrochemical Plants |publisher=John Wiley and Sons |year=1967 |edition=4th |lccn= 67019834}} (Includes cooling tower material balance for evaporation emissions and blowdown effluents. Available in many university libraries)</ref>

In areas with restricted water use, a dry cooling tower or directly air-cooled radiators may be necessary, since the cost or environmental consequences of obtaining make-up water for evaporative cooling would be prohibitive. These coolers have lower efficiency and higher energy consumption to drive fans, compared to a typical wet, evaporative cooling tower.{{Citation needed|date=July 2021}}

=== Air-cooled condenser (ACC) ===
Power plants can use an air-cooled condenser, traditionally in areas with a limited or expensive water supply. Air-cooled condensers serve the same purpose as a cooling tower (heat dissipation) without using water. They consume additional auxiliary power and thus may have a higher carbon footprint compared to a traditional cooling tower.{{Citation needed|date=July 2021}}

===Once-through cooling systems===
Electric companies often prefer to use cooling water from the ocean or a lake, river, or cooling pond instead of a cooling tower. This single pass or once-through cooling system can save the cost of a cooling tower and may have lower energy costs for pumping cooling water through the plant's [[Physics:Heat exchanger|heat exchanger]]s. However, the waste heat can cause [[Physics:Thermal pollution|thermal pollution]] as the water is discharged. Power plants using natural bodies of water for cooling are designed with mechanisms such as [[Biology:Fish screen|fish screen]]s, to limit intake of organisms into the cooling machinery. These screens are only partially effective and as a result billions of fish and other aquatic organisms are killed by power plants each year.<ref>{{cite court |litigants=Riverkeeper, Inc. v. U.S. EPA |vol=358 |reporter=F.3d |opinion=174 |pinpoint=181 |court=2d Cir. |date=2004 |url=http://openjurist.org/358/f3d/174/riverkeeper-inc-llc-v-united-states-environmental-protection-agency |access-date=2015-08-22 |quote=A single power plant might impinge a million adult fish in just a three-week period, or entrain some 3 to 4 billion smaller fish and shellfish in a year, destabilizing wildlife populations in the surrounding ecosystem.}}</ref><ref>U.S. Environmental Protection Agency, Washington, DC (May 2014). [http://www2.epa.gov/sites/production/files/2015-04/documents/final-regulations-cooling-water-intake-structures-at-existing-facilities_fact-sheet_may-2014.pdf "Final Regulations to Establish Requirements for Cooling Water Intake Structures at Existing Facilities."] {{Webarchive|url=https://web.archive.org/web/20200619180853/https://www.epa.gov/sites/production/files/2015-04/documents/final-regulations-cooling-water-intake-structures-at-existing-facilities_fact-sheet_may-2014.pdf |date=19 June 2020 }} Fact sheet. Document no. EPA-821-F-14-001.</ref> For example, the cooling system at the Indian Point Energy Center in New York kills over a billion fish eggs and larvae annually.<ref>{{Cite news |last=McGeehan |first=Patrick |date=2015-05-12 |title=Fire Prompts Renewed Calls to Close the Indian Point Nuclear Plant |work=The New York Times |url=https://www.nytimes.com/2015/05/13/nyregion/fire-prompts-renewed-calls-to-close-the-indian-point-nuclear-plant.html |access-date=3 March 2017 |archive-date=11 September 2019 |archive-url=https://web.archive.org/web/20190911085219/https://www.nytimes.com/2015/05/13/nyregion/fire-prompts-renewed-calls-to-close-the-indian-point-nuclear-plant.html |url-status=live }}</ref>  A further environmental impact is that aquatic organisms which adapt to the warmer discharge water may be injured if the plant shuts down in cold weather{{Citation Needed|date=October 2021}}.

Water consumption by power stations is a developing issue.<ref>American Association for the Advancement of Science. AAAS Annual Meeting 17 - 21 Feb 2011, Washington DC. "Sustainable or Not? Impacts and Uncertainties of Low-Carbon Energy Technologies on Water." Dr Evangelos Tzimas, European Commission, JRC Institute for Energy, Petten, Netherlands.</ref>

In recent years, recycled wastewater, or [[Earth:Greywater|grey water]], has been used in cooling towers. The Calpine Riverside and the Calpine Fox power stations in Wisconsin as well as the Calpine Mankato power station in Minnesota are among these facilities.{{Citation needed|date=July 2021}}

==Power from renewable energy==
Power stations can generate electrical energy from [[Engineering:Renewable energy|renewable energy]] sources.

===Hydroelectric power station===
[[File:ThreeGorgesDam-China2009.jpg|thumb|Three Gorges Dam, Hubei, China]]
In a hydroelectric power station water flows through turbines using [[Physics:Hydropower|hydropower]] to generate hydroelectricity. Power is captured from the gravitational force of water falling through penstocks to water turbines connected to [[Engineering:Electric generator|generators]]. The amount of power available is a combination of height and water flow. A wide range of Dams may be built to raise the water level, and create a lake for [[Earth:Reservoir|storing water]].
Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. {{wipe|China}} is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use.{{Citation needed|date=July 2021}}

===Solar===
{{Main|Engineering:Solar power}}
[[File:Giant photovoltaic array.jpg|thumb|Nellis Solar Power Plant in Nevada, United States]]

[[Physics:Solar energy|Solar energy]] can be turned into electricity either directly in [[Physics:Solar cell|solar cell]]s, or in a concentrating solar power plant by focusing the light to run a heat engine.<ref>{{Cite web|url=https://www.energy.gov/eere/solar/concentrating-solar-power|title=Concentrating Solar Power|website=Energy.gov|access-date=7 May 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204142009/https://www.energy.gov/eere/solar/concentrating-solar-thermal-power|url-status=live}}</ref>

A solar photovoltaic power plant converts sunlight into direct current electricity using the [[Physics:Photoelectric effect|photoelectric effect]]. [[Engineering:Power inverter|Inverters]] change the direct current into alternating current for connection to the electrical grid. This type of plant does not use rotating machines for energy conversion.<ref>{{Cite web|url=https://sites.lafayette.edu/egrs352-sp14-pv/technology/conversion-from-sunlight-to-electricity/|title=Conversion from sunlight to electricity – Solar photovoltaic|website=sites.lafayette.edu|access-date=7 May 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204142009/https://sites.lafayette.edu/egrs352-sp14-pv/technology/conversion-from-sunlight-to-electricity/|url-status=live}}</ref>

Solar thermal power plants use either parabolic troughs or heliostats to direct sunlight onto a pipe containing a heat transfer fluid, such as oil. The heated oil is then used to boil water into steam, which turns a turbine that drives an electrical generator. The central tower type of solar thermal power plant uses hundreds or thousands of mirrors, depending on size, to direct sunlight onto a receiver on top of a tower. The heat is used to produce steam to turn turbines that drive electrical generators.{{Citation needed|date=July 2021}}

===Wind===
[[File:GreenMountainWindFarm Fluvanna 2004.jpg|thumb|Wind turbines in Texas, {{wipe|United States}}]]

[[Physics:Wind turbine|Wind turbine]]s can be used to generate electricity in areas with strong, steady winds, sometimes [[Earth:Shore|offshore]]. Many different designs have been used in the past, but almost all modern turbines being produced today use a three-bladed, upwind design.<ref>{{Cite web|url=https://sciencing.com/places-wind-turbines-produce-electricity-5159049.html|title=The Best Places to Put Wind Turbines to Produce Electricity|website=Sciencing|access-date=7 May 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204152016/https://sciencing.com/places-wind-turbines-produce-electricity-5159049.html|url-status=live}}</ref> Grid-connected wind turbines now being built are much larger than the units installed during the 1970s. They thus produce power more cheaply and reliably than earlier models.<ref>{{Cite web|url=https://windexchange.energy.gov/small-wind-guidebook|title=WINDExchange: Small Wind Guidebook|website=windexchange.energy.gov|access-date=7 May 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204142035/https://windexchange.energy.gov/small-wind-guidebook|url-status=live}}</ref> With larger turbines (on the order of one megawatt), the blades move more slowly than older, smaller, units, which makes them less visually distracting and safer for birds.<ref>{{Cite web|url=https://www.aiche.org/chenected/2014/08/new-bird-friendly-wind-turbines-come-california|title=New "Bird-Friendly" Wind Turbines Come to California|date=14 August 2014|website=www.aiche.org|access-date=7 May 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204142046/https://www.aiche.org/chenected/2014/08/new-bird-friendly-wind-turbines-come-california|url-status=live}}</ref>

===Marine===
{{Main|Earth:Marine energy}}
'''Marine energy''' or '''marine power''' (also sometimes referred to as '''ocean energy''' or '''ocean power''') refers to the energy carried by ocean waves, [[Astronomy:Tide|tide]]s, [[Earth:Salinity|salinity]], and ocean temperature differences. The movement of water in the world's oceans creates a vast store of [[Physics:Kinetic energy|kinetic energy]], or energy in motion. This energy can be harnessed to [[Engineering:Electricity generation|generate]] electricity to power homes, transport and industries.

The term marine energy encompasses both [[Physics:Wave power|wave power]]—power from surface waves, and [[Engineering:Tidal power|tidal power]]—obtained from the kinetic energy of large bodies of moving water. Offshore wind power is not a form of marine energy, as wind power is derived from the [[Earth:Wind|wind]], even if the [[Physics:Wind turbine|wind turbine]]s are placed over water.

The [[Earth:Ocean|ocean]]s have a tremendous amount of energy and are close to many if not most concentrated populations. Ocean energy has the potential of providing a substantial amount of new [[Engineering:Renewable energy|renewable energy]] around the world.<ref>Carbon Trust, ''Future Marine Energy. Results of the Marine Energy Challenge: Cost competitiveness and growth of wave and tidal stream energy'', January 2006</ref>

===Osmosis===
[[File:Hurum osmosis power 02.JPG|thumb|Osmotic Power Prototype at Tofte (Hurum), Norway]]
{{Main|Physics:Osmotic power}}
Salinity gradient energy is called pressure-retarded osmosis. In this method, seawater is pumped into a pressure chamber that is at a pressure lower than the difference between the pressures of saline water and fresh water. Freshwater is also pumped into the pressure chamber through a membrane, which increases both the volume and pressure of the chamber. As the pressure differences are compensated, a turbine is spun creating energy. This method is being specifically studied by the Norwegian utility Statkraft, which has calculated that up to 25&nbsp;TWh/yr would be available from this process in Norway. Statkraft has built the world's first prototype osmotic power plant on the Oslo fjord which was opened on 24&nbsp;November 2009. In January 2014, however, Statkraft announced not to continue this pilot.<ref>{{Cite web |title=Is PRO economically feasible? Not according to Statkraft &#124; ForwardOsmosisTech |date=22 January 2014 |url=http://www.forwardosmosistech.com/statkraft-discontinues-investments-in-pressure-retarded-osmosis/ |url-status=live |archive-url=https://web.archive.org/web/20170118220928/http://www.forwardosmosistech.com/statkraft-discontinues-investments-in-pressure-retarded-osmosis/ |archive-date=2017-01-18 |access-date=2017-01-18}}</ref>

===Biomass===
[[File:Metz biomass power station.jpg|thumb|Metz biomass power station]]
[[Biology:Biomass|Biomass]] energy can be produced from combustion of waste green material to heat water into steam and drive a steam turbine. Bioenergy can also be processed through a range of temperatures and pressures in [[Physics:Gasification|gasification]], [[Chemistry:Pyrolysis|pyrolysis]] or [[Chemistry:Torrefaction|torrefaction]] reactions. Depending on the desired end product, these reactions create more energy-dense products ([[Chemistry:Syngas|syngas]], wood pellets, [[Chemistry:Torrefaction|biocoal]]) that can then be fed into an accompanying engine to produce electricity at a much lower emission rate when compared with open burning.{{Citation needed|date=July 2021}}

==Storage power stations==
{{Main|Grid energy storage}}It is possible to store energy and produce electrical power at a later time as in [[Engineering:Pumped-storage hydroelectricity|pumped-storage hydroelectricity]], [[Physics:Thermal energy storage|thermal energy storage]], [[Engineering:Flywheel energy storage|flywheel energy storage]], [[Physics:Battery storage power station|battery storage power station]] and so on.

===Pumped storage===
{{main|Engineering:Pumped-storage hydroelectricity}}

The world's largest form of storage for excess electricity, [[Engineering:Pumped-storage hydroelectricity|pumped-storage]] is a reversible hydroelectric plant. They are a net consumer of energy but provide storage for any source of electricity, effectively smoothing peaks and troughs in electricity supply and demand. Pumped storage plants typically use "spare" electricity during off peak periods to pump water from a lower reservoir to an upper reservoir. Because the pumping takes place "off peak", electricity is less valuable than at peak times. This less valuable "spare" electricity comes from uncontrolled wind power and [[Engineering:Base load|base load]] power plants such as coal, nuclear and geothermal, which still produce power at night even though demand is very low. During daytime peak demand, when electricity prices are high, the storage is used for [[Engineering:Peaking power plant|peaking power]], where water in the upper reservoir is allowed to flow back to a lower reservoir through a turbine and generator. Unlike coal power stations, which can take more than 12 hours to start up from cold, a hydroelectric generator can be brought into service in a few minutes, ideal to meet a peak load demand. Two substantial pumped storage schemes are in South Africa, Palmiet Pumped Storage Scheme and another in the Drakensberg, Ingula Pumped Storage Scheme.

==Typical power output==
{{See also|List of largest power stations}}The power generated by a power station is measured in multiples of the [[Watt|watt]], typically [[Mega-|megawatts]] (10<sup>6</sup> watts) or [[Giga-|gigawatts]] (10<sup>9</sup> watts). Power stations vary greatly in capacity depending on the type of power plant and on historical, geographical and economic factors. The following examples offer a sense of the scale.

Many of the largest operational onshore wind farms are located in China. As of 2022, the [[Engineering:Gansu Wind Farm|Roscoe Wind Farm]] is the largest onshore wind farm in the world, producing 8000&nbsp;MW of power, followed by the Zhang Jiakou (3000 MW). As of January 2022, the Hornsea Wind Farm in {{wipe|United Kingdom}} is the largest offshore wind farm in the world at 1218&nbsp;MW, followed by Walney Wind Farm in {{wipe|United Kingdom}} at 1026&nbsp;MW.

In 2021, the worldwide installed capacity of power plants increased by 347 GW. Solar and wind power plant capacities rose by 80% in one year.<ref>{{Cite web |title=PERFORMANCE OF THE MECHANICAL ENGINEERING DIVISION |url=https://report.rosatom.ru/go_eng/2021/aem_2021_eng.pdf |access-date=2023-10-31 |website=Rosatom}}</ref> {{As of|2022}}, the largest photovoltaic (PV) power plants in the world are led by Bhadla Solar Park in India, rated at 2245&nbsp;MW.

Solar thermal power stations in the U.S. have the following output:
:[[Organization:Ivanpah Solar Power Facility|Ivanpah Solar Power Facility]] is the largest of the country with an output of 392&nbsp;MW

[[File:Koebergnps.jpg|thumb|The Koeberg Nuclear Power Station, South Africa]]
Large coal-fired, nuclear, and hydroelectric power stations can generate hundreds of megawatts to multiple gigawatts. Some examples:
:The Koeberg Nuclear Power Station in South Africa has a rated capacity of 1860 megawatts. 
:The coal-fired Ratcliffe-on-Soar Power Station in the UK has a rated capacity of 2 gigawatts.
:The Aswan Dam hydro-electric plant in Egypt has a capacity of 2.1 gigawatts.
:The Three Gorges Dam hydro-electric plant in China has a capacity of 22.5 gigawatts.

Gas turbine power plants can generate tens to hundreds of megawatts. Some examples:
:The Indian Queens simple-cycle, or open cycle gas turbine (OCGT), peaking power station in Cornwall UK, with a single gas turbine is rated 140 megawatts.
:The Medway Power Station, a combined-cycle gas turbine (CCGT) power station in Kent, UK, with two gas turbines and one steam turbine, is rated 700 megawatts.<ref>[https://wayback.archive-it.org/all/20170525170032/http://www.industcards.com/cc-england-south.htm CCGT Plants in South England], by Power Plants Around the World</ref>

The rated capacity of a power station is nearly the maximum electrical power that the power station can produce.
Some power plants are run at almost exactly their rated capacity all the time, as a non-load-following base load power plant, except at times of scheduled or unscheduled maintenance.

However, many power plants usually produce much less power than their rated capacity.

In some cases a power plant produces much less power than its rated capacity because it uses an [[Engineering:Intermittent energy source|intermittent energy source]].
Operators try to pull maximum available power from such power plants, because their [[Finance:Marginal cost|marginal cost]] is practically zero, but the available power varies widely—in particular, it may be zero during heavy storms at night.

In some cases operators deliberately produce less power for economic reasons.
The cost of fuel to run a [[Engineering:Load following power plant|load following power plant]] may be relatively high, and the cost of fuel to run a [[Engineering:Peaking power plant|peaking power plant]] is even higher—they have relatively high marginal costs.
Operators keep power plants turned off ("operational reserve") or running at minimum fuel consumption{{Citation needed|date=January 2011}} ("spinning reserve") most of the time.
Operators feed more fuel into load following power plants only when the demand rises above what lower-cost plants (i.e., intermittent and base load plants) can produce, and then feed more fuel into peaking power plants only when the demand rises faster than the load following power plants can follow.

===Output metering===
Not all of the generated power of a plant is necessarily delivered into a distribution system. Power plants typically also use some of the power themselves, in which case the generation output is classified into ''gross generation'', and ''net generation''.

'''Gross generation''' or '''gross electric output''' is the total amount of electricity [[Engineering:Electricity generation#Turbines|generated]] by a power plant over a specific period of time.<ref>{{cite web|url=https://www.eia.gov/tools/faqs/faq.cfm?id=101&t=3|title=What is the difference between electricity generation capacity and electricity generation? - FAQ - U.S. Energy Information Administration (EIA)|access-date=24 December 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204142034/https://www.eia.gov/tools/faqs/faq.php?id=101&t=3|url-status=live}}</ref> It is measured at the generating terminal and is measured in [[Kilowatt hour|kilowatt-hours]] (kW·h), [[Kilowatt hour#Watt hour multiples and billing units|megawatt-hours]] (MW·h),<ref>{{cite web|url=https://www.eia.gov/tools/glossary/index.cfm?id=g|title=Glossary - U.S. Energy Information Administration (EIA)|access-date=24 December 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204142057/https://www.eia.gov/tools/glossary/index.php?id=g|url-status=live}}</ref> [[Kilowatt hour#Watt hour multiples and billing units|gigawatt-hours]] (GW·h) or for the largest power plants [[Kilowatt hour#Watt hour multiples and billing units|terawatt-hours]] (TW·h). It includes the electricity used in the plant auxiliaries and in the transformers.<ref>{{cite web|url=http://ec.europa.eu/eurostat/statistics-explained/index.php/Glossary:Gross_electricity_generation|title=Glossary:Gross electricity generation - Statistics Explained|access-date=24 December 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204142114/https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Gross_electricity_generation|url-status=live}}</ref>

:Gross generation =  net generation + usage within the plant (also known as in-house loads)

'''Net generation''' is the amount of [[Physics:Electricity|electricity]] generated by a power plant that is transmitted and distributed for consumer use. Net generation is less than the total gross power generation as some power produced is consumed within the plant itself to power auxiliary equipment such as pumps, motors and pollution control devices.<ref>{{Cite web|title=What is the difference between electricity generation capacity and electricity generation?|url=https://www.eia.gov/tools/faqs/faq.php?id=101&t=3|date=4 February 2020|website=U.S. Energy Information Administration|access-date=29 May 2020|archive-date=4 February 2023|archive-url=https://web.archive.org/web/20230204142047/https://www.eia.gov/tools/faqs/faq.php?id=101&t=3|url-status=live}}</ref>  Thus

:Net generation =  gross generation − usage within the plant ({{aka}} in-house loads)

==Operations==
[[File:Power plant control room.jpg|thumb|Control room of a power plant]]{{Unreferenced section|date=July 2021}}
Operating staff at a power station have several duties. Operators are responsible for the safety of the work crews that frequently do repairs on the mechanical and electrical equipment. They maintain the equipment with periodic inspections and log temperatures, pressures and other important information at regular intervals. Operators are responsible for starting and stopping the [[Engineering:Electrical generator|generators]] depending on need. They are able to synchronize and adjust the voltage output of the added generation with the running electrical system, without upsetting the system. They must know the electrical and mechanical systems to troubleshoot problems in the facility and add to the reliability of the facility. Operators must be able to respond to an emergency and know the procedures in place to deal with it.

==See also==
{{div col|colwidth=30em}}
* [[Physics:Cogeneration|Cogeneration]]
* [[Physics:Cooling tower|Cooling tower]]
* [[Finance:Cost of electricity by source|Cost of electricity by source]]
* [[Physics:District heating|District heating]]
* [[Engineering:Electricity generation|Electricity generation]]
* Environmental impact of electricity generation
* [[Physics:Flue-gas stack|Flue-gas stack]]
* Fossil-fuel power station
* Geothermal electricity
* Gravitation water vortex power plant 
* [[Physics:Grid-tied electrical system|Grid-tied electrical system]] mini-power plants
* List of largest power stations in the world
* List of power stations
* List of thermal power station failures
* [[Engineering:Nuclear power plant|Nuclear power plant]]
* [[Physics:Plant efficiency|Plant efficiency]]
* [[Finance:Unit commitment problem in electrical power production|Unit commitment problem]]
* [[Engineering:Virtual power plant|Virtual power plant]]
{{div col end}}

==References==
{{reflist}}

==External links==
* [https://web.archive.org/web/20070927104145/http://www.vgb.org/db_kks_eng.html Identification System for Power Stations (KKS)]
* [https://wayback.archive-it.org/all/20121006110626/http://www.industcards.com/top-100-pt-1.htm Largest Power Plants in the World]
* [https://web.archive.org/web/20180809183553/http://carma.org/ Database of carbon emissions of power plants worldwide (Carbon Monitoring For Action: CARMA)]
*[https://web.archive.org/web/20121021024835/http://www.epa.gov/airmarkt/progsregs/nox/docs/netgross.pdf Net vs Gross Output Measurement] ''Archived from [http://www.epa.gov/airmarkt/progsregs/nox/docs/netgross.pdf the original] (pdf) on 21 October 2012''
*[https://web.archive.org/web/20121002202041/http://www.epa.gov/airmarkt/progsregs/nox/docs/netvgrow.pdf Measuring power generation] ''Archived from [http://www.epa.gov/airmarkt/progsregs/nox/docs/netvgrow.pdf the original] (pdf) on 2 October 2012''

{{electricity generation}}

{{DEFAULTSORT:Power Station}}
[[Category:Chemical process engineering]]

{{Sourceattribution|Power station}}