Thermal power plants are classified by the type of fuel and the type of prime mover installed.
· Nuclear power plants use a nuclear reactor's heat to operate a steam turbine generator. About 20% of electric generation in the USA is produced by nuclear power plants.
· 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. A coal-fired power station produces electricity by burning coal to generate steam, and has the side-effect of producing a large amount of carbon dioxide, which is released from burning coal and contributes to global warming. About 50% of electric generation in the USA is produced by coal fired power plants
· Geothermal power plants use steam extracted from hot underground rocks.
· Renewable energy plants or Biomass Fuelled Power Plants may be fuelled by waste from sugar cane, municipal solid waste, landfill methane, or other forms of biomass.
· In integrated steel mills, blast furnace exhaust gas is a low-cost, although low-energy-density, fuel.
· Waste heat from industrial processes is occasionally concentrated enough to use for power generation, usually in a steam boiler and turbine.
· Solar thermal electric plants use sunlight to boil water, which turns the generator.
· Steam turbine plants use the dynamic pressure generated by expanding steam to turn the blades of a turbine. Almost all large non-hydro plants use this system. About 80% of all electric power produced in the world is by use of steam turbines.
· Gas turbine plants use the dynamic pressure from flowing gases (air and combustion products) to directly operate the turbine. Natural-gas fuelled (and oil fueled) combustion turbine plants can start rapidly and so are used to supply "peak" energy during periods of high demand, though at higher cost than base-loaded plants. These may be comparatively small units, and sometimes completely unmanned, being remotely operated. This type was pioneered by the UK, Princetown 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 hot exhaust gas from the gas turbine to produce electricity. This greatly increases the overall efficiency of the plant, and many new baseload power plants are combined cycle plants fired by natural gas.
· Internal combustion Reciprocating engines are used to provide power for isolated communities and are frequently used for small cogeneration plants. Hospitals, office buildings, industrial plants, and other critical facilities also use them to provide backup power in case of a power outage. These are usually fuelled by diesel oil, heavy oil, natural gas and landfill gas.
· Microturbines, Stirling engine and internal combustion reciprocating engines are low-cost solutions for using opportunity fuels, such as landfill gas, digester gas from water treatment plants and waste gas from oil production.