POWER STATIONS AND ELECTRICITY




A power station (also referred to as generating station or power plant) is an industrial facility for the generation of electric power.[1][2][3]

Power plant is also used to refer to the engine in ships, aircraft and other large vehicles. Some prefer to use the term energy center because it more accurately describes what the plants do, which is the conversion of other forms of energy, like chemical energy, gravitational potential energy or heat energy into electrical energy. However, power plant is the most common term in the U.S., while elsewhere power station and power plant are both widely used, power station prevailing in many Commonwealth countries and especially in the United Kingdom.



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 what fuels are easily available and the types of technology that the power company has access to.

Thermal power stations

Rotor of a modern steam turbine, used in power stationMain article: Thermal power station
In thermal power stations, mechanical power is produced by a heat engine, which transforms thermal energy, often from combustion of a fuel, into rotational energy. Most thermal power stations produce steam, and these are sometimes called steam power stations. About 80% of all electric power is generated by use of steam turbines.[citation needed] Not all thermal energy can be transformed to mechanical power, according to 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 the Middle East uses byproduct heat for desalination of water.


[edit] Classification

CHP plant in Warsaw, Poland
Geothermal power station in Iceland
Coal Power Station in Tampa FL
480 megawatt GE H series power generation gas turbineThermal power plants are classified by the type of fuel and the type of prime mover installed.


[edit] By fuel
Nuclear power plants[4] use a nuclear reactor's heat to operate a steam turbine generator.
Fossil fuelled power plants may also use a steam turbine generator or in the case of natural gas fired plants may use a combustion turbine.
Geothermal power plants use steam extracted from hot underground rocks.
Renewable energy plants may be fuelled by waste from sugar cane, municipal solid waste, landfill methane, or other forms of biomass.
In integrated steel mills, blast furnace exhaust gas is a low-cost, although low-energy-density, fuel.
Waste heat from industrial processes is occasionally concentrated enough to use for power generation, usually in a steam boiler and turbine.

[edit] By prime mover
Steam turbine plants use the dynamic pressure generated by expanding steam to turn the blades of a turbine. Almost all large non-hydro plants use this system.
Gas turbine plants use the dynamic pressure from flowing gases to directly operate the turbine. Natural-gas fuelled 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[5] being the world's first, commissioned in 1959.
Combined cycle plants have both a gas turbine fired by natural gas, and a steam boiler and steam turbine which use the exhaust gas from the gas turbine to produce electricity. This greatly increases the overall efficiency of the plant, and many new baseload power plants are combined cycle plants fired by natural gas.
Internal combustion Reciprocating engines are used to provide power for isolated communities and are frequently used for small cogeneration plants. Hospitals, office buildings, industrial plants, and other critical facilities also use them to provide backup power in case of a power outage. These are usually fuelled by diesel oil, heavy oil, natural gas and landfill gas.
Microturbines, Stirling engine and internal combustion reciprocating engines are low cost solutions for using opportunity fuels, such as landfill gas, digester gas from water treatment plants and waste gas from oil production.