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 .
96-612: 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 fossil fuels such as coal , oil , and natural gas to generate electricity. Low-carbon power sources include nuclear power , and use of renewables such as solar , wind , geothermal , and hydroelectric . In early 1871 Belgian inventor Zénobe Gramme invented
192-459: A generator is a device that converts motion-based power ( potential and kinetic energy ) or fuel-based power ( chemical energy ) into electric power for use in an external circuit . Sources of mechanical energy include steam turbines , gas turbines , water turbines , internal combustion engines , wind turbines and even hand cranks . The first electromagnetic generator, the Faraday disk ,
288-441: A motor-generator set. Also devices with mercury arc rectifiers or vacuum tubes were in use. With the advent of solid state electronics , it has become possible to build completely electronic frequency changers. These devices usually consist of a rectifier stage (producing direct current ) which is then inverted to produce AC of the desired frequency. The inverter may use thyristors , IGCTs or IGBTs . If voltage conversion
384-653: A steam power plant . The first practical design was the AVCO Mk. 25, developed in 1965. The U.S. government funded substantial development, culminating in a 25 MW demonstration plant in 1987. In the Soviet Union from 1972 until the late 1980s, the MHD plant U 25 was in regular utility operation on the Moscow power system with a rating of 25 MW, the largest MHD plant rating in the world at that time. MHD generators operated as
480-698: A topping cycle are currently (2007) less efficient than combined cycle gas turbines . Induction AC motors may be used as generators, turning mechanical energy into electric current. Induction generators operate by mechanically turning their rotor faster than the simultaneous speed, giving negative slip. A regular AC non-simultaneous motor usually can be used as a generator, without any changes to its parts. Induction generators are useful in applications like minihydro power plants, wind turbines, or in reducing high-pressure gas streams to lower pressure, because they can recover energy with relatively simple controls. They do not require another circuit to start working because
576-579: 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
672-479: A British electrician, J. E. H. Gordon , in 1882. The first public demonstration of an "alternator system" was given by William Stanley Jr. , an employee of Westinghouse Electric in 1886. Sebastian Ziani de Ferranti established Ferranti, Thompson and Ince in 1882, to market his Ferranti-Thompson Alternator , invented with the help of renowned physicist Lord Kelvin . His early alternators produced frequencies between 100 and 300 Hz . Ferranti went on to design
768-419: 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. 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
864-436: A foot pump, such generators can be practically used to charge batteries, and in some cases are designed with an integral inverter. An average "healthy human" can produce a steady 75 watts (0.1 horsepower) for a full eight hour period, while a "first class athlete" can produce approximately 298 watts (0.4 horsepower) for a similar period, at the end of which an undetermined period of rest and recovery will be required. At 298 watts,
960-456: A generator and load is shown in the adjacent diagram. The generator is represented by an abstract generator consisting of an ideal voltage source and an internal impedance. The generator's V G {\displaystyle V_{\text{G}}} and R G {\displaystyle R_{\text{G}}} parameters can be determined by measuring the winding resistance (corrected to operating temperature ), and measuring
1056-430: A generator consists of a rotating part and a stationary part which together form a magnetic circuit : One of these parts generates a magnetic field, the other has a wire winding in which the changing field induces an electric current: The armature can be on either the rotor or the stator, depending on the design, with the field coil or magnet on the other part. Before the connection between magnetism and electricity
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#17327728825201152-425: A generator powerful enough to produce power on a commercial scale for industry. In 1878, a hydroelectric power station was designed and built by William, Lord Armstrong at Cragside , England . It used water from lakes on his estate to power Siemens dynamos . The electricity supplied power to lights, heating, produced hot water, ran an elevator as well as labor-saving devices and farm buildings. In January 1882
1248-425: A hydroelectric power station water flows through turbines using hydropower to generate hydroelectricity . Power is captured from the gravitational force of water falling through penstocks to water turbines connected to 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 storing water . Hydropower
1344-403: 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,
1440-449: A magnetic field produces a current which changes direction with each 180° rotation, an alternating current (AC). However many early uses of electricity required direct current (DC). In the first practical electric generators, called dynamos , the AC was converted into DC with a commutator , a set of rotating switch contacts on the armature shaft. The commutator reversed the connection of
1536-404: A material that enhances the mixing of the upflowing air and the down-flowing water. 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
1632-403: A million amperes , because the homopolar generator can be made to have very low internal resistance. A magnetohydrodynamic generator directly extracts electric power from moving hot gases through a magnetic field, without the use of rotating electromagnetic machinery. MHD generators were originally developed because the output of a plasma MHD generator is a flame, well able to heat the boilers of
1728-513: A much-lower-powered circuit that converts radio frequency signals at one frequency to another frequency , especially in a superheterodyne receiver . See frequency mixer . The circuit usually consists of a local oscillator and frequency mixer (analog multiplier) that generates sum and difference frequencies from the input and local oscillator, of which one (the Intermediate frequency ) will be required for further amplification, while
1824-568: 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. Wind turbines can be used to generate electricity in areas with strong, steady winds, sometimes offshore . Many different designs have been used in
1920-592: 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 intermittent energy source . Operators try to pull maximum available power from such power plants, because their marginal cost
2016-488: A series of discoveries, the dynamo was succeeded by many later inventions, especially the AC alternator , which was capable of generating alternating current . It is commonly known to be the Synchronous Generators (SGs). The synchronous machines are directly connected to the grid and need to be properly synchronized during startup. Moreover, they are excited with special control to enhance the stability of
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#17327728825202112-438: A sliding magnet moves back and forth through a solenoid , a copper wire or a coil. An alternating current is induced in the wire, or loops of wire, by Faraday's law of induction each time the magnet slides through. This type of generator is used in the Faraday flashlight . Larger linear electricity generators are used in wave power schemes. Grid-connected generators deliver power at a constant frequency. For generators of
2208-434: A small DC voltage . This design was inefficient, due to self-cancelling counterflows of current in regions of the disk that were not under the influence of the magnetic field. While current was induced directly underneath the magnet, the current would circulate backwards in regions that were outside the influence of the magnetic field. This counterflow limited the power output to the pickup wires and induced waste heating of
2304-450: A stable power supply. Electric scooters with regenerative braking have become popular all over the world. Engineers use kinetic energy recovery systems on the scooter to reduce energy consumption and increase its range up to 40-60% by simply recovering energy using the magnetic brake, which generates electric energy for further use. Modern vehicles reach speed up to 25–30 km/h and can run up to 35–40 km. An engine-generator
2400-420: A steam turbine. Bioenergy can also be processed through a range of temperatures and pressures in gasification , pyrolysis or torrefaction reactions. Depending on the desired end product, these reactions create more energy-dense products ( syngas , wood pellets , biocoal ) that can then be fed into an accompanying engine to produce electricity at a much lower emission rate when compared with open burning. It
2496-641: 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 State Grid Archived 21 December 2021 at the Wayback Machine planned to build an 8-GW thermal power plant, which's the largest coal-fired power plant construction project in Russia . A prime mover is a machine that converts energy of various forms into energy of motion. Power plants that can be dispatched (scheduled) to provide energy to
2592-494: A system include: 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. All thermal power plants produce waste heat energy as
2688-681: 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. Biomass energy can be produced from combustion of waste green material to heat water into steam and drive
2784-414: A type of frequency changer. Unlike a VFD, which is an indirect frequency changer since it uses an AC-DC stage and then a DC-AC stage, a cycloconverter is a direct frequency changer because it uses no intermediate stages. Another application is in the aerospace and airline industries. Often airplanes use 400 Hz power so a 50 Hz or 60 Hz to 400 Hz frequency converter is needed for use in
2880-443: A typical wet, evaporative cooling tower. 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. Electric companies often prefer to use cooling water from
2976-417: A water- or wind-powered generator to trickle-charge the batteries. A small propeller , wind turbine or turbine is connected to a low-power generator to supply currents at typical wind or cruising speeds. Recreational vehicles need an extra power supply to power their onboard accessories, including air conditioning units, and refrigerators. An RV power plug is connected to the electric generator to obtain
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3072-487: 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
3168-403: Is a type of frequency changer used for speed control of AC motors such as used for pumps and fans. The speed of a synchronous or induction AC motor is dependent on the frequency of the AC power supply, so changing frequency allows the motor speed to be changed. This allows fan or pump output to be varied to match process conditions, which can provide energy savings. A cycloconverter is also
3264-431: Is an electronic or electromechanical device that converts alternating current ( AC ) 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, since voltage conversion of alternating current is much easier to achieve than frequency conversion. Traditionally, these devices were electromechanical machines called
3360-562: Is an industrial facility that generates electricity . Most power stations contain one or more generators, or spinning machines converting mechanical power into three-phase electrical 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 fossil fuels such as coal , oil , and natural gas to generate electricity. Cleaner sources include nuclear power , and increasingly use renewables such as
3456-662: Is desired, a transformer will usually be included in either the AC input or output circuitry and this transformer may also provide galvanic isolation between the input and output AC circuits. A battery may also be added to the DC circuitry to improve the converter's ride-through of brief outages in the input power. Frequency changers vary in power-handling capability from a few watts to megawatts. Frequency changers are used for converting bulk AC power from one frequency to another, when two adjacent power grids operate at different utility frequency . A variable-frequency drive (VFD)
3552-583: 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. 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
3648-517: 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 may be relatively high, and the cost of fuel to run a 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 ("spinning reserve") most of
3744-464: Is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. Solar energy can be turned into electricity either directly in solar cells , or in a concentrating solar power plant by focusing
3840-497: Is provided by one or more electromagnets, which are usually called field coils. Large power generation dynamos are now rarely seen due to the now nearly universal use of alternating current for power distribution. Before the adoption of AC, very large direct-current dynamos were the only means of power generation and distribution. AC has come to dominate due to the ability of AC to be easily transformed to and from very high voltages to permit low losses over large distances. Through
3936-415: Is self- excited , i.e. its field electromagnets are powered by the machine's own output. Other types of DC generators use a separate source of direct current to energise their field magnets. A homopolar generator is a DC electrical generator comprising an electrically conductive disc or cylinder rotating in a plane perpendicular to a uniform static magnetic field. A potential difference is created between
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4032-405: Is the ability to independently supply electricity, allowing the units to serve as backup power sources. A generator can also be driven by human muscle power (for instance, in field radio station equipment). Human powered electric generators are commercially available, and have been the project of some DIY enthusiasts. Typically operated by means of pedal power, a converted bicycle trainer, or
4128-485: Is the combination of an electrical generator and an engine ( prime mover ) mounted together to form a single piece of self-contained equipment. The engines used are usually piston engines, but gas turbines can also be used, and there are even hybrid diesel-gas units, called dual-fuel units. Many different versions of engine-generators are available – ranging from very small portable petrol powered sets to large turbine installations. The primary advantage of engine-generators
4224-410: 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 combined cycle plant. Most commonly, exhaust gases from a gas turbine are used to generate steam for a boiler and
4320-805: The Deptford Power Station for the London Electric Supply Corporation in 1887 using an alternating current system. On its completion in 1891, it was the first truly modern power station, supplying high-voltage AC power that was then "stepped down" for consumer use on each street. This basic system remains in use today around the world. After 1891, polyphase alternators were introduced to supply currents of multiple differing phases. Later alternators were designed for varying alternating-current frequencies between sixteen and about one hundred hertz, for use with arc lighting, incandescent lighting and electric motors. As
4416-758: The Roscoe Wind Farm is the largest onshore wind farm in the world, producing 8000 MW of power, followed by the Zhang Jiakou (3000 MW). As of January 2022, the Hornsea Wind Farm in United Kingdom is the largest offshore wind farm in the world at 1218 MW, followed by Walney Wind Farm in United Kingdom at 1026 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. As of 2022,
4512-488: 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: Large coal-fired, nuclear, and hydroelectric power stations can generate hundreds of megawatts to multiple gigawatts. Some examples: Gas turbine power plants can generate tens to hundreds of megawatts. Some examples: The rated capacity of
4608-439: The 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 district heating , the power plant is referred to as a cogeneration 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 stations . An important class of power stations in
4704-490: 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 in central station service, around 1906, allowed great expansion of generating capacity. Generators were no longer limited by
4800-671: The Air ), medical and other needs in remote stations and towns. A tachogenerator is an electromechanical device which produces an output voltage proportional to its shaft speed. It may be used for a speed indicator or in a feedback speed control system. Tachogenerators are frequently used to power tachometers to measure the speeds of electric motors, engines, and the equipment they power. Generators generate voltage roughly proportional to shaft speed. With precise construction and design, generators can be built to produce very precise voltages for certain ranges of shaft speeds. An equivalent circuit of
4896-570: The Drakensberg, Ingula Pumped Storage Scheme . The power generated by a power station is measured in multiples of the watt , typically megawatts (10 watts) or gigawatts (10 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,
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#17327728825204992-493: The Middle East uses by-product heat for the 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
5088-626: The United States, Ferranti and Charles Hesterman Merz in UK, and many others. 2021 world electricity generation by source. Total generation was 28 petawatt-hours . In thermal power stations, mechanical power is produced by a heat engine that transforms thermal energy , often from 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
5184-478: The armature winding to the circuit every 180° rotation of the shaft, creating a pulsing DC current. One of the first dynamos was built by Hippolyte Pixii in 1832. The dynamo was the first electrical generator capable of delivering power for industry. The Woolrich Electrical Generator of 1844, now in Thinktank, Birmingham Science Museum , is the earliest electrical generator used in an industrial process. It
5280-436: The armature winding. When the generator first starts to turn, the small amount of remanent magnetism present in the iron core provides a magnetic field to get it started, generating a small current in the armature. This flows through the field coils, creating a larger magnetic field which generates a larger armature current. This "bootstrap" process continues until the magnetic field in the core levels off due to saturation and
5376-402: The assistance of power electronic devices, these can regulate the output frequency to a desired value over a wider range of generator shaft speeds. Alternatively, a standard generator can be used with no attempt to regulate frequency, and the resulting power converted to the desired output frequency with a rectifier and converter combination. Allowing a wider range of prime mover speeds can improve
5472-464: The average "healthy human" becomes exhausted within 10 minutes. The net electrical power that can be produced will be less, due to the efficiency of the generator. Portable radio receivers with a crank are made to reduce battery purchase requirements, see clockwork radio . During the mid 20th century, pedal powered radios were used throughout the Australian outback , to provide schooling ( School of
5568-409: The bicycle's tire on an as-needed basis, and hub dynamos which are directly attached to the bicycle's drive train. The name is conventional as they are small permanent-magnet alternators, not self-excited DC machines as are dynamos . Some electric bicycles are capable of regenerative braking , where the drive motor is used as a generator to recover some energy during braking. Sailing boats may use
5664-597: The center of the disc and the rim (or ends of the cylinder), the electrical polarity depending on the direction of rotation and the orientation of the field. It is also known as a unipolar generator , acyclic generator , disk dynamo , or Faraday disc . The voltage is typically low, on the order of a few volts in the case of small demonstration models, but large research generators can produce hundreds of volts, and some systems have multiple generators in series to produce an even larger voltage. They are unusual in that they can produce tremendous electric current, some more than
5760-549: 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. For example, the cooling system at the Indian Point Energy Center in New York kills over a billion fish eggs and larvae annually. A further environmental impact is that aquatic organisms which adapt to the warmer discharge water may be injured if
5856-436: The copper disc. Later homopolar generators would solve this problem by using an array of magnets arranged around the disc perimeter to maintain a steady field effect in one current-flow direction. Another disadvantage was that the output voltage was very low, due to the single current path through the magnetic flux. Experimenters found that using multiple turns of wire in a coil could produce higher, more useful voltages. Since
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#17327728825205952-407: The difficulty of insulating machines that produced very high voltages, electrostatic generators had low power ratings, and were never used for generation of commercially significant quantities of electric power. Their only practical applications were to power early X-ray tubes , and later in some atomic particle accelerators . The operating principle of electromagnetic generators was discovered in
6048-411: The energy carried by ocean waves , tides , salinity , and ocean temperature differences . The movement of water in the world's oceans creates a vast store of kinetic energy , or energy in motion. This energy can be harnessed to generate electricity to power homes, transport and industries. The term marine energy encompasses both wave power —power from surface waves, and tidal power —obtained from
6144-409: 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
6240-413: The first major industrial uses of electricity. For example, in the 1870s Siemens used electromagnetic dynamos to power electric arc furnaces for the production of metals and other materials. The dynamo machine that was developed consisted of a stationary structure, which provides the magnetic field, and a set of rotating windings which turn within that field. On larger machines the constant magnetic field
6336-476: The generator reaches a steady state power output. Very large power station generators often utilize a separate smaller generator to excite the field coils of the larger. In the event of a severe widespread power outage where islanding of power stations has occurred, the stations may need to perform a black start to excite the fields of their largest generators, in order to restore customer power service. A dynamo uses commutators to produce direct current. It
6432-637: The ground power unit used to power the airplane while it is on the ground. Airlines might also utilize the converters to provide in-air wall current to passengers for use with laptops and the like. Radio and combat systems equipment on Navy warships is often also powered by 400 Hz to reduce noise on the DC signal after rectification. In renewable energy systems, frequency converters are an essential component of doubly fed induction generators ( DFIGs ) as used in modern multi-megawatt class wind turbines. An HVDC -system can serve as frequency converter for large loads. Frequency converter may also refer to
6528-406: 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
6624-533: The largest power plants terawatt-hours (TW·h). It includes the electricity used in the plant auxiliaries and in the transformers. Net generation is the amount of 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. Thus Electric generator In electricity generation ,
6720-423: The light to run a heat engine. 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. Solar thermal power plants use either parabolic troughs or heliostats to direct sunlight onto
6816-479: 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 heat exchangers . However, the waste heat can cause thermal pollution as the water is discharged. Power plants using natural bodies of water for cooling are designed with mechanisms such as fish screens , to limit intake of organisms into
6912-423: The open-circuit and loaded voltage for a defined current load. This is the simplest model of a generator, further elements may need to be added for an accurate representation. In particular, inductance can be added to allow for the machine's windings and magnetic leakage flux, but a full representation can become much more complex than this. Frequency changer A frequency changer or frequency converter
7008-413: The output voltage is proportional to the number of turns, generators could be easily designed to produce any desired voltage by varying the number of turns. Wire windings became a basic feature of all subsequent generator designs. Independently of Faraday, Ányos Jedlik started experimenting in 1827 with the electromagnetic rotating devices which he called electromagnetic self-rotors . In the prototype of
7104-443: The overall energy production of an installation, at the cost of more complex generators and controls. For example, where a wind turbine operating at fixed frequency might be required to spill energy at high wind speeds, a variable speed system can allow recovery of energy contained during periods of high wind speed. A power station , also known as a power plant or powerhouse and sometimes generating station or generating plant ,
7200-554: 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. They thus 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 birds. Marine energy or marine power (also sometimes referred to as ocean energy or ocean power ) refers to
7296-671: 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 as well as the Calpine Mankato power station in Minnesota are among these facilities. Power stations can generate electrical energy from renewable energy sources. In
7392-472: The power system. Alternating current generating systems were known in simple forms from Michael Faraday 's original discovery of the magnetic induction of electric current . Faraday himself built an early alternator. His machine was a "rotating rectangle", whose operation was heteropolar : each active conductor passed successively through regions where the magnetic field was in opposite directions. Large two-phase alternating current generators were built by
7488-404: 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 generated by a power plant over a specific period of time. It is measured at the generating terminal and is measured in kilowatt-hours (kW·h), megawatt-hours (MW·h), gigawatt-hours (GW·h) or for
7584-559: 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
7680-399: The requirements for larger scale power generation increased, a new limitation rose: the magnetic fields available from permanent magnets. Diverting a small amount of the power generated by the generator to an electromagnetic field coil allowed the generator to produce substantially more power. This concept was dubbed self-excitation . The field coils are connected in series or parallel with
7776-727: 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 . In September 1882 in New York, the Pearl Street Station
7872-777: The same power plant. Natural draft wet cooling towers at many nuclear power plants and large fossil-fuel-fired power plants use large hyperboloid chimney -like structures (as seen in the image at the right) 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 , petrochemical plants , geothermal , 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
7968-449: The single-pole electric starter (finished between 1852 and 1854) both the stationary and the revolving parts were electromagnetic. It was also the discovery of the principle of dynamo self-excitation , which replaced permanent magnet designs. He also may have formulated the concept of the dynamo in 1861 (before Siemens and Wheatstone ) but did not patent it as he thought he was not the first to realize this. A coil of wire rotating in
8064-521: The stator field. Wheatstone's design was similar to Siemens', with the difference that in the Siemens design the stator electromagnets were in series with the rotor, but in Wheatstone's design they were in parallel. The use of electromagnets rather than permanent magnets greatly increased the power output of a dynamo and enabled high power generation for the first time. This invention led directly to
8160-512: 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
8256-611: The sun , wind , waves and running water . Motor vehicles require electrical energy to power their instrumentation, keep the engine itself operating, and recharge their batteries. Until about the 1960s motor vehicles tended to use DC generators (dynamos) with electromechanical regulators. Following the historical trend above and for many of the same reasons, these have now been replaced by alternators with built-in rectifier circuits. Bicycles require energy to power running lights and other equipment. There are two common kinds of generator in use on bicycles: bottle dynamos which engage
8352-476: The synchronous or induction type, the primer mover speed turning the generator shaft must be at a particular speed (or narrow range of speed) to deliver power at the required utility frequency. Mechanical speed-regulating devices may waste a significant fraction of the input energy to maintain a required fixed frequency. Where it is impractical or undesired to tightly regulate the speed of the prime mover, doubly fed electric machines may be used as generators. With
8448-448: 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. Not all of the generated power of a plant is necessarily delivered into a distribution system. Power plants typically also use some of
8544-421: The turning magnetic field is provided by induction from the one they have. They also do not require speed governor equipment as they inherently operate at the connected grid frequency. An induction generator must be powered with a leading voltage; this is usually done by connection to an electrical grid, or by powering themselves with phase correcting capacitors. In the simplest form of linear electric generator,
8640-565: The world's first public coal-fired power station , the Edison Electric Light Station , was built in London, a project of Thomas Edison organized by Edward Johnson . A Babcock & Wilcox boiler powered a 93 kW (125 horsepower) steam engine that drove a 27-tonne (27-long-ton) generator. This supplied electricity to premises in the area that could be reached through the culverts of the viaduct without digging up
8736-414: The world. 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,
8832-409: The years of 1831–1832 by Michael Faraday . The principle, later called Faraday's law , is that an electromotive force is generated in an electrical conductor which encircles a varying magnetic flux . Faraday also built the first electromagnetic generator, called the Faraday disk ; a type of homopolar generator , using a copper disc rotating between the poles of a horseshoe magnet . It produced
8928-429: Was discovered, electrostatic generators were invented. They operated on electrostatic principles, by using moving electrically charged belts, plates and disks that carried charge to a high potential electrode. The charge was generated using either of two mechanisms: electrostatic induction or the triboelectric effect . Such generators generated very high voltage and low current . Because of their inefficiency and
9024-406: 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
9120-635: Was invented in 1831 by British scientist Michael Faraday . Generators provide nearly all the power for electrical grids . In addition to electricity- and motion-based designs, photovoltaic and fuel cell powered generators use solar power and hydrogen-based fuels, respectively, to generate electrical output. The reverse conversion of electrical energy into mechanical energy is done by an electric motor , and motors and generators are very similar. Many motors can generate electricity from mechanical energy. Electromagnetic generators fall into one of two broad categories, dynamos and alternators. Mechanically,
9216-597: Was used by the firm of Elkingtons for commercial electroplating . The modern dynamo, fit for use in industrial applications, was invented independently by Sir Charles Wheatstone , Werner von Siemens and Samuel Alfred Varley . Varley took out a patent on 24 December 1866, while Siemens and Wheatstone both announced their discoveries on 17 January 1867 by delivering papers at the Royal Society . The "dynamo-electric machine" employed self-powering electromagnetic field coils rather than permanent magnets to create
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