Power station
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A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid.
Many power stations contain one or more generators, rotating machine that converts mechanical power into three-phase electric power. The relative motion between a magnetic field and a conductor creates an electric current.
The energy source harnessed to turn the generator varies widely. Most power stations in the world burn
History
In early 1871 Belgian inventor Zénobe Gramme invented a generator powerful enough to produce power on a commercial scale for industry.[1]
In 1878, a hydroelectric power station was designed and built by
In January 1882 the world's first public
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 steam engines 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 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 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.
AC systems used a wide range of 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 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 frequency changers 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
Thermal power stations
In thermal power stations, mechanical power is produced by a
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
In 2018,
Classification
By heat source
- nitrogen oxides, and carbon dioxide. Some of the gases can be removed from the waste stream to reduce pollution.
- Nuclear power plants[8] use the heat generated in a nuclear reactor's core (by the 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.
- 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.[9]
- Biomass-fuelled power plants may be fuelled by waste from sugar cane, municipal solid waste, landfill methane, or other forms of biomass.
- In integrated steel mills, blast furnace exhaust gas is a low-cost, although low-energy-density, fuel.
- Waste heat from industrial processes is occasionally concentrated enough to use for power generation, usually in a steam boiler and turbine.
- Solar thermal electric plants use sunlight to boil water and produce steam which turns the generator.
- Hydrogen power plants can use green hydrogen from electrolysis to help balance supply and demand from Variable renewable energy sources.[10]
By prime mover
A prime mover is a machine that converts energy of various forms into energy of motion.
- 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.[11]
- 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[12] being the world's first, commissioned in 1959.
- Combined cycleplants 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 reciprocating engines 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, natural gas, and landfill gas.
- Microturbines, Stirling engine and internal combustion reciprocating engines are low-cost solutions for using opportunity fuels, such as landfill gas, digester gas from water treatment plants and waste gas from oil production.[citation needed]
By duty
Power plants that can be dispatched (scheduled) to provide energy to a system include:
- Base load power plantsrun 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.
- Peaking power plants 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.
- Load following power plantscan 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]
Cooling towers
All thermal power plants produce
However, the mechanical induced-draft or forced-draft wet cooling towers in many large thermal power plants, nuclear power plants, fossil-fired power plants,
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]
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]
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
Water consumption by power stations is a developing issue.[18]
In recent years, recycled wastewater, or 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]
Power from renewable energy
Power stations can generate electrical energy from renewable energy sources.
Hydroelectric power station
In a hydroelectric power station water flows through turbines using
Solar
A solar photovoltaic power plant converts sunlight into direct current electricity using the photoelectric effect. 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.[20]
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]
Wind
Marine
Marine energy or marine power (also sometimes referred to as ocean energy or ocean power) refers to the energy carried by
The term marine energy encompasses both wave power—power from surface waves, and 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 wind, even if the wind turbines are placed over water.
The oceans 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 renewable energy around the world.[24]
Osmosis
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 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 November 2009. In January 2014, however, Statkraft announced not to continue this pilot.[25]
Biomass
Storage power stations
It is possible to store energy and produce electrical power at a later time as in pumped-storage hydroelectricity, thermal energy storage, flywheel energy storage, battery storage power station and so on.
Pumped storage
The world's largest form of storage for excess electricity, 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 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 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
The power generated by a power station is measured in multiples of the watt, typically megawatts (106 watts) or gigawatts (109 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
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.[26] As of 2022[update], the largest photovoltaic (PV) power plants in the world are led by Bhadla Solar Park in India, rated at 2245 MW.
Solar thermal power stations in the U.S. have the following output:
- Ivanpah Solar Power Facility is the largest of the country with an output of 392 MW
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.[27]
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
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
In some cases operators deliberately produce less power for economic reasons. The cost of fuel to run a
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
- Gross generation = net generation + usage within the plant (also known as in-house loads)
Net generation is the amount of
- Net generation = gross generation − usage within the plant (a.k.a. in-house loads)
Operations
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
See also
- Cogeneration
- Cooling tower
- Cost of electricity by source
- District heating
- Electricity generation
- Environmental impact of electricity generation
- Flue-gas stack
- Fossil-fuel power station
- Geothermal electricity
- Gravitation water vortex power plant
- 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
- Nuclear power plant
- Plant efficiency
- Public utility building
- Unit commitment problem
- Virtual power plant
References
- ^ Thompson, Silvanus Phillips (1888). Dynamo-electric Machinery: A Manual for Students of Electrotechnics. London: E. & F. N. Spon. p. 140.
- ^ "Hydro-electricity restored to historic Northumberland home". BBC News. 27 February 2013. Archived from the original on 29 December 2019. Retrieved 21 July 2018.
- ^ Jack Harris (14 January 1982), "The electricity of Holborn", New Scientist, archived from the original on 4 February 2023, retrieved 21 November 2015
- ^ "History of Power: The Evolution of the Electric Generation Industry". Power. 1 October 2022. Archived from the original on 28 January 2023. Retrieved 27 February 2023.
- ^ "Yearly electricity data". ember-climate.org. 6 December 2023. Retrieved 23 December 2023.
- ^ "China and Russia accelerate pace of power cooperation". Ministry of Commerce. 24 July 2018. Archived from the original on 4 February 2023. Retrieved 29 July 2020.
- ^ "Inter RAO UES cooperates with State Grid Corporation of China". Reference News. 4 June 2018. Archived from the original on 4 February 2023. Retrieved 29 July 2020.
- ^ Nuclear Power Plants Information Archived 13 February 2005 at the Wayback Machine, by International Atomic Energy Agency
- ^ Roberts, David (21 October 2020). "Geothermal energy is poised for a big breakout". Vox. Archived from the original on 4 February 2023. Retrieved 13 April 2022.
- ^ Mulder, Sebastian (29 October 2021). "Ready for the Energy Transition: Hydrogen Considerations for Combined Cycle Power Plants". Power.
- ISBN 978-0-387-98744-6. Archivedfrom the original on 23 January 2023. Retrieved 21 November 2015.
- ^ SWEB's Pocket Power Stations Archived 4 May 2006 at the Wayback Machine
- ^ J. C. Hensley, ed. (2006). Cooling Tower Fundamentals (2nd ed.). SPX Cooling Technologies. Archived from the original on 18 June 2013. Retrieved 13 September 2007.
- LCCN 67019834. (Includes cooling tower material balance for evaporation emissions and blowdown effluents. Available in many university libraries)
- ^ Riverkeeper, Inc. v. U.S. EPA, 358 F.3d 174, 181 (2d Cir. 2004) ("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.").
- ^ U.S. Environmental Protection Agency, Washington, DC (May 2014). "Final Regulations to Establish Requirements for Cooling Water Intake Structures at Existing Facilities." Archived 19 June 2020 at the Wayback Machine Fact sheet. Document no. EPA-821-F-14-001.
- ^ McGeehan, Patrick (12 May 2015). "Fire Prompts Renewed Calls to Close the Indian Point Nuclear Plant". The New York Times. Archived from the original on 11 September 2019. Retrieved 3 March 2017.
- ^ 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.
- ^ "Concentrating Solar Power". Energy.gov. Archived from the original on 4 February 2023. Retrieved 7 May 2020.
- ^ "Conversion from sunlight to electricity – Solar photovoltaic". sites.lafayette.edu. Archived from the original on 4 February 2023. Retrieved 7 May 2020.
- ^ "The Best Places to Put Wind Turbines to Produce Electricity". Sciencing. Archived from the original on 4 February 2023. Retrieved 7 May 2020.
- ^ "WINDExchange: Small Wind Guidebook". windexchange.energy.gov. Archived from the original on 4 February 2023. Retrieved 7 May 2020.
- ^ "New "Bird-Friendly" Wind Turbines Come to California". www.aiche.org. 14 August 2014. Archived from the original on 4 February 2023. Retrieved 7 May 2020.
- ^ Carbon Trust, Future Marine Energy. Results of the Marine Energy Challenge: Cost competitiveness and growth of wave and tidal stream energy, January 2006
- ^ "Is PRO economically feasible? Not according to Statkraft | ForwardOsmosisTech". 22 January 2014. Archived from the original on 18 January 2017. Retrieved 18 January 2017.
- ^ "PERFORMANCE OF THE MECHANICAL ENGINEERING DIVISION" (PDF). Rosatom. Retrieved 31 October 2023.
- ^ CCGT Plants in South England, by Power Plants Around the World
- ^ "What is the difference between electricity generation capacity and electricity generation? - FAQ - U.S. Energy Information Administration (EIA)". Archived from the original on 4 February 2023. Retrieved 24 December 2020.
- ^ "Glossary - U.S. Energy Information Administration (EIA)". Archived from the original on 4 February 2023. Retrieved 24 December 2020.
- ^ "Glossary:Gross electricity generation - Statistics Explained". Archived from the original on 4 February 2023. Retrieved 24 December 2020.
- ^ "What is the difference between electricity generation capacity and electricity generation?". U.S. Energy Information Administration. 4 February 2020. Archived from the original on 4 February 2023. Retrieved 29 May 2020.
External links
- Identification System for Power Stations (KKS)
- Largest Power Plants in the World
- Database of carbon emissions of power plants worldwide (Carbon Monitoring For Action: CARMA)
- Net vs Gross Output Measurement Archived from the original (pdf) on 21 October 2012
- Measuring power generation Archived from the original (pdf) on 2 October 2012