Power station

Power station

Overview

A power station is an industrial facility for the generation
Electricity generation
Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...

 of electric energy.

At the center of nearly all power stations is a generator, a rotating machine that converts mechanical energy into electrical energy by creating relative motion between a magnetic field and a conductor. The energy source harnessed to turn the generator varies widely. It depends chiefly on which fuels are easily available and on the types of technology that the power company has access to.

The world's first power station was built by Sigmund Schuckert in the Bavaria
Bavarian
Bavarian is the adjective form of the German state of Bavaria, and refers to people of ancestry from Bavaria. Bavarian may also refer to:* Austro-Bavarian, a group of closely related dialects of German, spoken in parts of Bavaria, most of Austria and the Alto Adige/Südtirol* Bavarian cream, a...

 town of Ettal
Ettal
Ettal is a German municipality in the district of Garmisch-Partenkirchen, in Bavaria.-Geography:Ettal is situated in the Oberland area in the Graswangtal between the Loisachtal and Ammertal, approx. 10 km north of Garmisch-Partenkirchen, the district capital, and approx...

 and went into operation in 1878.
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Encyclopedia

A power station is an industrial facility for the generation
Electricity generation
Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...

 of electric energy.

At the center of nearly all power stations is a generator, a rotating machine that converts mechanical energy into electrical energy by creating relative motion between a magnetic field and a conductor. The energy source harnessed to turn the generator varies widely. It depends chiefly on which fuels are easily available and on the types of technology that the power company has access to.

History


The world's first power station was built by Sigmund Schuckert in the Bavaria
Bavarian
Bavarian is the adjective form of the German state of Bavaria, and refers to people of ancestry from Bavaria. Bavarian may also refer to:* Austro-Bavarian, a group of closely related dialects of German, spoken in parts of Bavaria, most of Austria and the Alto Adige/Südtirol* Bavarian cream, a...

 town of Ettal
Ettal
Ettal is a German municipality in the district of Garmisch-Partenkirchen, in Bavaria.-Geography:Ettal is situated in the Oberland area in the Graswangtal between the Loisachtal and Ammertal, approx. 10 km north of Garmisch-Partenkirchen, the district capital, and approx...

 and went into operation in 1878. The station consisted of 24 dynamo
Dynamo
- Engineering :* Dynamo, a magnetic device originally used as an electric generator* Dynamo theory, a theory relating to magnetic fields of celestial bodies* Solar dynamo, the physical process that generates the Sun's magnetic field- Software :...

 electric generators which were driven by a steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

. It was used to illuminate a grotto in the gardens of Linderhof Palace.

The first public power station was the Edison Electric Light Station, built in London at 57, Holborn Viaduct
Holborn Viaduct
Holborn Viaduct is a bridge in London and the name of the street which crosses it . It links Holborn, via Holborn Circus, with Newgate Street in the City of London, passing over Farringdon Street and the now subterranean River Fleet.It was built between 1863 and 1869, at a cost of over two million...

, which started operation in January 1882. This was an initiative of Thomas Edison
Thomas Edison
Thomas Alva Edison was an American inventor and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. In addition, he created the world’s first industrial...

 that was organized and managed by his partner, Edward Johnson. A Babcock and Wilcox
Babcock and Wilcox
The Babcock & Wilcox Company is a U.S.-based company that provides design, engineering, manufacturing, construction and facilities management services to nuclear, renewable, fossil power, industrial and government customers worldwide. B&W's boilers supply more than 300,000 megawatts of installed...

 boiler powered a 125 horsepower steam engine that drove a 27 ton generator called Jumbo
Jumbo
Jumbo was a large African Bush Elephant, born 1861 in the French Sudan – present-day Mali – imported to a Paris zoo, transferred to the London Zoo in 1865, and sold in 1882 to P. T...

, after the celebrated elephant. This supplied electricity to premises in the area that could be reached through the culvert
Culvert
A culvert is a device used to channel water. It may be used to allow water to pass underneath a road, railway, or embankment. Culverts can be made of many different materials; steel, polyvinyl chloride and concrete are the most common...

s of the viaduct without digging up the road, which was the monopoly of the gas companies. The customers included the City Temple
City Temple (London)
City Temple Church is a church on Holborn Viaduct in London, most famous as the preaching place of 20th century liberal theologian Leslie Weatherhead.Other notable preachers include Thomas Goodwin and Joseph Parker....

 and the Old Bailey
Old Bailey
The Central Criminal Court in England and Wales, commonly known as the Old Bailey from the street in which it stands, is a court building in central London, one of a number of buildings housing the Crown Court...

. Another important customer was the Telegraph Office of the General Post Office but this could not be reached though the culverts. Johnson arranged for the supply cable to be run overhead, via Holborn Tavern and Newgate
Newgate
Newgate at the west end of Newgate Street was one of the historic seven gates of London Wall round the City of London and one of the six which date back to Roman times. From it a Roman road led west to Silchester...

.

In September 1882 in New York, the Pearl Street Station
Pearl Street Station
Pearl Street Station was the first central power plant in the United States. It was located at 255-257 Pearl Street in Manhattan on a site measuring 50 by 100 feet, just south of Fulton Street. It began with one direct current generator, and it started generating electricity on September 4, 1882,...

 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 engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...

s to turn direct-current generators. Because of the DC distribution, the service area was small, limited by voltage drop in the feeders. The War of Currents
War of Currents
In the "War of Currents" era in the late 1880s, George Westinghouse and Thomas Edison became adversaries due to Edison's promotion of direct current for electric power distribution over alternating current advocated by several European companies and Westinghouse Electric based out of Pittsburgh,...

 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
Utility frequency
The utility frequency, line frequency or mains frequency is the frequency at which alternating current is transmitted from a power plant to the end-user. In most parts of the world this is 50 Hz, although in the Americas it is typically 60 Hz...

 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
Load factor
Load factor may refer to:* Load factor , the ratio of the lift of an aircraft to its weight* Load factor , the ratio of the number of records to the number of addresses within a data structure...

 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 changer
Frequency changer
A frequency changer or frequency converter is an electronic device that converts alternating current of one frequency to alternating current of another frequency. The device may also change the voltage, but if it does, that is incidental to its principal purpose.Traditionally, these devices were...

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 steam turbine
Steam turbine
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....

 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
Sebastian Ziani de Ferranti
Sebastian Pietro Innocenzo Adhemar Ziani de Ferranti was an electrical engineer and inventor.-Personal life:...

 planned what would have been the largest 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
George Westinghouse
George Westinghouse, Jr was an American entrepreneur and engineer who invented the railway air brake and was a pioneer of the electrical industry. Westinghouse was one of Thomas Edison's main rivals in the early implementation of the American electricity system...

 and Samuel Insull
Samuel Insull
Samuel Insull was an Anglo-American innovator and investor based in Chicago who greatly contributed to creating an integrated electrical infrastructure in the United States. Insull was notable for purchasing utilities and railroads using holding companies, as well as the abuse of them...

 in the United States, Ferranti and Charles Hesterman Merz
Charles Hesterman Merz
Charles Hesterman Merz was a British electrical engineer who pioneered the use of high-voltage three-phase AC power distribution in the United Kingdom, building a system in the North East of England in the early 20th century that became the model for the country's National Grid.-Life:Merz was then...

 in UK, and many others.

Thermal power stations




In thermal power stations, mechanical power is produced by a heat engine
Heat engine
In thermodynamics, a heat engine is a system that performs the conversion of heat or thermal energy to mechanical work. It does this by bringing a working substance from a high temperature state to a lower temperature state. A heat "source" generates thermal energy that brings the working substance...

 that transforms thermal energy
Thermal energy
Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system's temperature....

, often from combustion
Combustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...

 of a fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

, into rotational energy. Most thermal power stations produce steam, and these are sometimes called steam power stations. Not all thermal energy can be transformed into mechanical power, according to the second law of thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...

. Therefore, there is always heat lost to the environment. If this loss is employed as useful heat, for industrial processes or district heating
District heating
District heating is a system for distributing heat generated in a centralized location for residential and commercial heating requirements such as space heating and water heating...

, the power plant is referred to as a cogeneration
Cogeneration
Cogeneration is the use of a heat engine or a power station to simultaneously generate both electricity and useful heat....

 power plant or CHP (combined heat-and-power) plant. In countries where district heating is common, there are dedicated heat plants called heat-only boiler station
Heat-only boiler station
A heat-only boiler station generates thermal energy in the form of hot water for use in district heating applications. Unlike combined heat and power installations which produce thermal energy as a by-product of electricity generation, heat-only boiler stations are dedicated to generating heat.The...

s. An important class of power stations in the Middle East uses by-product heat for the desalination
Desalination
Desalination, desalinization, or desalinisation refers to any of several processes that remove some amount of salt and other minerals from saline water...

 of water.

The efficiency of a steam turbine is limited by the maximum temperature of the steam produced and 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).

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. Most commonly, exhaust gases from a gas turbine are used to generate steam for a boiler and steam turbine. The combination of a "top" cycle and a "bottom" cycle produces higher overall efficiency than either cycle can attain alone.

Classification



Thermal power plants are classified by the type of fuel and the type of prime mover installed.

By fuel

  • Fossil fuelled power plants
    Fossil fuel power plant
    A fossil-fuel power station is a power station that burns fossil fuels such as coal, natural gas or petroleum to produce electricity. Central station fossil-fuel power plants are designed on a large scale for continuous operation...

     may also use a steam turbine generator or in the case of natural gas
    Natural gas
    Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...

     fired plants may use a combustion turbine
    Gas turbine
    A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....

    . A coal-fired power station
    Coal-fired power station
    A coal-fired power station produces electricity, usually for public consumption, by burning coal to boil water, producing steam which drives a steam turbine which turns an electrical generator...

     produces electricity
    Electricity
    Electricity is a general term encompassing a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning, static electricity, and the flow of electrical current in an electrical wire...

     by burning coal to generate steam, and has the side-effect of producing large amounts of sulfur dioxide
    Sulfur dioxide
    Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

     which pollutes air and water and carbon dioxide
    Carbon dioxide
    Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

    , which contributes to global warming
    Global warming
    Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

    . About 50% of electric generation in the USA is produced by coal fired power plants
  • Nuclear power plant
    Nuclear power plant
    A nuclear power plant is a thermal power station in which the heat source is one or more nuclear reactors. As in a conventional thermal power station the heat is used to generate steam which drives a steam turbine connected to a generator which produces electricity.Nuclear power plants are usually...

    s use a nuclear reactor
    Nuclear reactor
    A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

    's heat to operate a steam turbine
    Steam turbine
    A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....

     generator. About 20% of electric generation in the USA is produced by nuclear power plants.
  • Geothermal power
    Geothermal power
    Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet and from radioactive decay of minerals...

     plants use steam extracted from hot underground rocks.
  • Biomass-fuelled power plants may be fuelled by waste from sugar cane
    Bagasse
    Bagasse is the fibrous matter that remains after sugarcane or sorghum stalks are crushed to extract their juice. It is currently used as a biofuel and as a renewable resource in the manufacture of pulp and paper products and building materials....

    , municipal solid waste
    Incineration
    Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials. Incineration and other high temperature waste treatment systems are described as "thermal treatment". Incineration of waste materials converts the waste into ash, flue gas, and...

    , landfill methane
    Methane
    Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

    , or other forms of biomass
    Biomass
    Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

    .
  • In integrated steel mill
    Steel mill
    A steel mill or steelworks is an industrial plant for the manufacture of steel.Steel is an alloy of iron and carbon. It is produced in a two-stage process. First, iron ore is reduced or smelted with coke and limestone in a blast furnace, producing molten iron which is either cast into pig iron or...

    s, blast furnace
    Blast furnace
    A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron.In a blast furnace, fuel and ore and flux are continuously supplied through the top of the furnace, while air is blown into the bottom of the chamber, so that the chemical reactions...

     exhaust gas is a low-cost, although low-energy-density, fuel.
  • Waste heat from industrial processes
    Cogeneration
    Cogeneration is the use of a heat engine or a power station to simultaneously generate both electricity and useful heat....

     is occasionally concentrated enough to use for power generation, usually in a steam boiler and turbine.
  • Solar thermal
    Solar power
    Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...

     electric plants use sunlight to boil water, which turns the generator.

By prime mover

  • Steam turbine
    Steam turbine
    A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....

     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% of all electric power produced in the world is by use of steam turbines.
  • Gas turbine
    Gas turbine
    A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....

     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 being the world's first, commissioned in 1959.
  • Combined cycle
    Combined cycle
    In electric power generation a combined cycle is an assembly of heat engines that work in tandem off the same source of heat, converting it into mechanical energy, which in turn usually drives electrical generators...

     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 reciprocating engine
    Reciprocating engine
    A reciprocating engine, also often known as a piston engine, is a heat engine that uses one or more reciprocating pistons to convert pressure into a rotating motion. This article describes the common features of all types...

    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, natural gas
    Natural gas
    Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural...

    , and landfill gas
    Landfill gas
    Landfill gas is a complex mix of different gases created by the action of microorganisms within a landfill.-Production:Landfill gas production results from chemical reactions and microbes acting upon the waste as the putrescible materials begins to break down in the landfill...

    .
  • Microturbines, Stirling engine
    Stirling engine
    A Stirling engine is a heat engine operating by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work....

     and internal combustion reciprocating engines are low-cost solutions for using opportunity fuels, such as landfill gas
    Landfill gas
    Landfill gas is a complex mix of different gases created by the action of microorganisms within a landfill.-Production:Landfill gas production results from chemical reactions and microbes acting upon the waste as the putrescible materials begins to break down in the landfill...

    , digester gas from water treatment plants and waste gas from oil production.

Cooling towers



All thermal power plants produce waste heat
Waste heat
Waste heat sometimes called Secondary heat or Low-grade heat refers to heat produced by machines, electrical equipment and industrial processes for which no useful application is found. Energy is often produced by a heat engine, running on a source of high-temperature heat...

 energy as a byproduct of the useful electrical energy produced. The amount of waste heat energy equals or exceeds the amount of electrical energy produced. Gas-fired power plants can achieve 50% 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 of greenhouse-gas emissions from the same power plant. Natural draft wet cooling tower
Cooling tower
Cooling towers are heat removal devices used to transfer process waste heat to the atmosphere. Cooling towers may either use the evaporation of water to remove process heat and cool the working fluid to near the wet-bulb air temperature or in the case of closed circuit dry cooling towers rely...

s at many nuclear power plants and large fossil fuel fired power plants use large hyperbolic chimney
Chimney
A chimney is a structure for venting hot flue gases or smoke from a boiler, stove, furnace or fireplace to the outside atmosphere. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing air into the combustion in what is known as the...

-like structures (as seen in the image at the left) that release the waste heat to the ambient atmosphere by the 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, petroleum refineries
Oil refinery
An oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...

, petrochemical plants
Petrochemical
Petrochemicals are chemical products derived from petroleum. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as corn or sugar cane....

, geothermal
Geothermal power
Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet and from radioactive decay of minerals...

, biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

 and waste to energy plants use fans
Fan (mechanical)
A mechanical fan is a machine used to create flow within a fluid, typically a gas such as air.A fan consists of a rotating arrangement of vanes or blades which act on the air. Usually, it is contained within some form of housing or case. This may direct the airflow or increase safety by preventing...

 to provide air movement upward through downcoming water and are not hyperbolic chimney-like structures. The induced or forced-draft cooling towers are typically rectangular, box-like structures filled with a material that enhances the contacting of the upflowing air and the downflowing water.

In areas with restricted water use a dry cooling tower or radiators, directly air cooled, may be necessary, since the cost or environmental consequences of obtaining make-up water for evaporative cooling would be prohibitive. These have lower efficiency and higher energy consumption in fans than a wet, evaporative cooling tower.

Where economically and environmentally possible, electric companies prefer to use cooling water from the ocean, or a lake or river, or a cooling pond, instead of a cooling tower. This type of cooling can save the cost of a cooling tower and may have lower energy costs for pumping cooling water through the plant's heat exchanger
Heat exchanger
A heat exchanger is a piece of equipment built for efficient heat transfer from one medium to another. The media may be separated by a solid wall, so that they never mix, or they may be in direct contact...

s. However, the waste heat can cause the temperature of the water to rise detectably. Power plants using natural bodies of water for cooling must be designed to prevent intake of organisms into the cooling cycle. A further environmental impact would be organisms that adapt to the warmer plant water and may be injured if the plant shuts down in cold weather.

Water consumption by power stations is a developing issue.

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
Wisconsin
Wisconsin is a U.S. state located in the north-central United States and is part of the Midwest. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin's capital is...

 as well as the Calpine Mankato power station in Minnesota
Minnesota
Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

 are among these facilities.

Other sources of energy


Other power stations use the energy from wave
Wave
In physics, a wave is a disturbance that travels through space and time, accompanied by the transfer of energy.Waves travel and the wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass...

 or tidal motion
Tidal power
Tidal power, also called tidal energy, is a form of hydropower that converts the energy of tides into useful forms of power - mainly electricity....

, wind
Wind power
Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships....

, sunlight
Solar power
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...

 or the energy of falling water, hydroelectricity
Hydroelectricity
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...

. These types of energy sources are called renewable energy
Renewable energy
Renewable energy is energy which comes from natural resources such as sunlight, wind, rain, tides, and geothermal heat, which are renewable . About 16% of global final energy consumption comes from renewables, with 10% coming from traditional biomass, which is mainly used for heating, and 3.4% from...

.

Hydroelectricity



Dams
DAMS
Driot-Arnoux Motorsport is a racing team from France, involved in many areas of motorsports. DAMS was founded in 1988 by Jean-Paul Driot and former Formula One driver René Arnoux. It is headquartered near Le Mans, only 2 km from the Bugatti Circuit.- History :The year after its foundation,...

 built to produce hydroelectricity
Hydroelectricity
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...

 impound a reservoir of water and release it through one or more water turbine
Water turbine
A water turbine is a rotary engine that takes energy from moving water.Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. They harness a clean and renewable energy...

s, connected to generators, and generate electricity, from the energy provided by difference in water level upstream and downstream.

Pumped storage


A pumped-storage
Pumped-storage hydroelectricity
Pumped-storage hydroelectricity is a type of hydroelectric power generation used by some power plants for load balancing. The method stores energy in the form of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost off-peak electric power is used to run the pumps...

 hydroelectric power plant is a net consumer of energy but can be used to smooth peaks and troughs in overall electricity demand. Pumped storage plants typically use "spare" electricity during off peak periods to pump water from a lower reservoir or dam to an upper reservoir. Because the electricity is consumed "off peak" it is typically cheaper than power at peak times. This is because the "base load" power stations, which are typically coal fired, cannot be switched on and off quickly so remain in service even when demand is low. During hours of peak demand, when the electricity price is high, the water pumped to the high reservoir is allowed to flow back to the lower reservoir through a water turbine connected to an electricity generator. Unlike coal power stations, which can take more than 12 hours to start up from cold, the hydroelectric plant 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, one to the East of Cape Town (Palmiet) and one in the Drakensberg, Natal

Solar



Solar energy can be turned into electricity either directly in solar cell
Solar cell
A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....

s, or in a concentrating solar power plant by focusing the light to run a heat engine.


A solar photovoltaic power plant converts sunlight into direct current electricity using the photoelectric effect
Photoelectric effect
In the photoelectric effect, electrons are emitted from matter as a consequence of their absorption of energy from electromagnetic radiation of very short wavelength, such as visible or ultraviolet light. Electrons emitted in this manner may be referred to as photoelectrons...

. Inverter
Inverter
Inverter may refer to* Inverter , a device that converts direct current to alternating current** Inverter , an air conditioner that can continuously regulate its output by altering the compressor speed in response to cooling demand** Uninterruptible power supply, which often are based on an...

s 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.

Solar thermal power plants are another type of solar power plant. They use either parabolic troughs or heliostat
Heliostat
A heliostat is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating for the sun's apparent motions in the sky. The target may be a physical object, distant from the heliostat, or a direction in space...

s 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. Again, the heat is used to produce steam to turn turbines that drive electrical generators.

Wind




Wind turbines can be used to generate electricity in areas with strong, steady winds, sometimes offshore
Shore
A shore or shoreline is the fringe of land at the edge of a large body of water, such as an ocean, sea, or lake. In Physical Oceanography a shore is the wider fringe that is geologically modified by the action of the body of water past and present, while the beach is at the edge of the shore,...

. Many different designs have been used in the past, but almost all modern turbines being produced today use a three-bladed, upwind design. Grid-connected wind turbines now being built are much larger than the units installed during the 1970s, and so produce power more cheaply and reliably than earlier models. 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 airborne animals.

Typical power output


The power generated by a power station is measured in multiples of the watt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...

, 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 the USA. As of 2011, the Roscoe Wind Farm
Roscoe Wind Farm
The Roscoe Wind Farm in Roscoe, Texas, owned and operated by E.ON Climate & Renewables is the world's largest capacity wind farm with 627 wind turbines and a total installed capacity of 781.5 MW, which surpasses the nearby 735.5 MW Horse Hollow Wind Energy Center.Roscoe was constructed in four phases...

 is the largest onshore wind farm in the world, producing 781.5 MW of power, followed by the Horse Hollow Wind Energy Center
Horse Hollow Wind Energy Center
Horse Hollow Wind Energy Center is a large wind farm with 735.5 megawatt capacity. It consists of 291 GE 1.5 MW wind turbines and 130 Siemens 2.3 MW wind turbines spread over nearly 47,000 acres of land in Taylor and Nolan County, Texas....

 (735.5 MW). As of November 2010, the Thanet Offshore Wind Project
Thanet Offshore Wind Project
The Thanet Wind Farm is an offshore wind farm off the coast of Thanet district in Kent, England. As of September 2010, it is the world's biggest offshore windfarm. It has a nameplate capacity of 300 MW and it cost £780-900 million...

 in United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 is the largest offshore wind farm in the world at 300 MW, followed by Horns Rev II (209 MW) in Denmark.

As of 2011, the largest photovoltaic (PV) power plants in the world are rated up to 97 megawatts. Larger power stations are under construction, some proposed will have a capacity of 150 MW or more. A planned installation in China will produce 2000 megawatts at peak.

Solar thermal power stations in the U.S. have the following output:
The country's largest solar facility at Kramer Junction
Solar Energy Generating Systems
Solar Energy Generating Systems is the largest solar energy generating facility in the world. It consists of nine solar power plants in California's Mojave Desert, where insolation is among the best available in the United States...

 has an output of 354 MW
The planned Blythe Solar Power Project
Blythe Solar Power Project
The Blythe Solar Power Project is a solar power station under construction in Riverside County, California. The project is being developed by Solarhybrid/Solar Millennium's subsidiary Solar Trust of America, in a joint venture with Chevron Energy Solutions....

 will produce an estimated 968 MW


Large coal-fired, nuclear, and hydroelectric power stations can generate hundreds of Megawatts to multiple Gigawatts. Some examples:
The Three Mile Island Nuclear Generating Station
Three Mile Island Nuclear Generating Station
Three Mile Island Nuclear Generating Station is a civilian nuclear power plant located on Three Mile Island in the Susquehanna River, south of Harrisburg, Pennsylvania. It has two separate units, known as TMI-1 and TMI-2...

 in the USA has a rated capacity of 802 megawatts.
The coal-fired Ratcliffe-on-Soar Power Station
Ratcliffe-on-Soar Power Station
Ratcliffe-on-Soar power station is a coal-fired power station operated by E.ON UK at Ratcliffe-on-Soar in Nottinghamshire, England. Commissioned in 1968 by the then Central Electricity Generating Board, the station has a capacity of 2,000 MW...

 in the UK has a rated capacity of 2 gigawatts.
The Aswan Dam
Aswan Dam
The Aswan Dam is an embankment dam situated across the Nile River in Aswan, Egypt. Since the 1950s, the name commonly refers to the High Dam, which is larger and newer than the Aswan Low Dam, which was first completed in 1902...

 hydro-electric plant in Egypt has a capacity of 2.1 gigawatts.
The Three Gorges Dam
Three Gorges Dam
The Three Gorges Dam is a hydroelectric dam that spans the Yangtze River by the town of Sandouping, located in the Yiling District of Yichang, in Hubei province, China...

 hydro-electric plant in China will have a capacity of 22.5 gigawatts when complete; 18.2 gigawatts capacity is operating as of 2010.


Gas turbine power plants can generate tens to hundreds of megawatts. Some examples:
The Indian Queens
Indian Queens
Indian Queens is a village in Cornwall, United Kingdom. The village is situated west of Goss Moor and north of Fraddon approximately ten miles west-southwest of Bodmin....

 simple-cycle peaking power station in Cornwall UK, with a single gas turbine is rated 140 megawatts.
The Medway Power Station
Medway Power Station
Medway Power Station is a 688 megawatts gas-fired power station on the Isle of Grain in Medway next to the River Medway.- History :It is run by Scottish & Southern Energy under the name Medway Power Ltd. It was built by Marubeni , Tarmac and Kansas City-based Black & Veatch...

, a combined-cycle power station in Kent, UK with two gas turbines and one steam turbine, is rated 700 megawatts.


The rated capacity of a power station is nearly the maximum electrical power that that 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
Base load power plant
Baseload is the minimum amount of power that a utility or distribution company must make available to its customers, or the amount of power required to meet minimum demands based on reasonable expectations of customer requirements...

, 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 intermittent energy source.
Operators try to pull maximum available power
Maximum power point tracker
Maximum power point tracking is a technique that grid tie inverters, solar battery chargers and similar devices use to get the maximum possible power from the PV array. Solar cells have a complex relationship between solar irradiation, temperature and total resistance that produces a non-linear...

 from such power plants, because their marginal cost
Marginal cost
In economics and finance, marginal cost is the change in total cost that arises when the quantity produced changes by one unit. That is, it is the cost of producing one more unit of a good...

 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 load following power plant
Load following power plant
A load following power plant is a power plant that adjusts its power output as demand for electricity fluctuates throughout the day. Load following plants are typically in-between base load and peaking power plants in efficiency, speed of startup and shutdown, construction cost, cost of electricity...

 may be relatively high, and the cost of fuel to run a peaking power plant
Peaking power plant
Peaking power plants, also known as peaker plants, and occasionally just "peakers," are power plants that generally run only when there is a high demand, known as peak demand, for electricity.-Peak hours:...

 is even higher—they have relatively high marginal costs.
Operators keep them turned off ("operational reserve") or running at minimum fuel consumption ("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.

Operations


The power station operator has several duties in the electricity-generating facility. 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 inspection
Inspection
An inspection is, most generally, an organized examination or formal evaluation exercise. In engineering activities inspection involves the measurements, tests, and gauges applied to certain characteristics in regard to an object or activity...

s and log temperatures, pressures and other important information at regular intervals. Operators are responsible for starting and stopping the generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...

s 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 in order 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



  • Battery-to-grid mini-power plants
  • Combined heat and power
    Combined Heat and Power
    Combined Heat and Power may refer to:* Cogeneration* Combined Heat and Power Solar...

  • Cooling tower system
  • District heating
    District heating
    District heating is a system for distributing heat generated in a centralized location for residential and commercial heating requirements such as space heating and water heating...

  • Electricity generation
    Electricity generation
    Electricity generation is the process of generating electric energy from other forms of energy.The fundamental principles of electricity generation were discovered during the 1820s and early 1830s by the British scientist Michael Faraday...

  • Environmental concerns with electricity generation
    Environmental concerns with electricity generation
    The environmental impact of electricity generation is significant because modern society uses large amounts of electrical power. This power is normally generated at power plants that convert some other kind of energy into electrical power...

  • Flue gas stacks
  • Fossil fuel power station
  • Geothermal power
    Geothermal power
    Geothermal energy is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Earth's geothermal energy originates from the original formation of the planet and from radioactive decay of minerals...

  • KKS Power Plant Classification System
  • Relative cost of electricity generated by different sources
  • Plant efficiency
    Plant efficiency
    The efficiency of a plant is the percentage of the total energy content of a power plant's fuel that is converted into electricity. The remaining energy is usually lost to the environment as heat unless it is used for district heating....

  • Virtual power plant
    Virtual power plant
    A virtual power plant is a cluster of distributed generation installations which are collectively run by a central control entity....


External links