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The Cheng cycle is a simplified form of combined cycle where the steam turbine is eliminated by injecting steam directly into the combustion turbine. This has been used since the mid 1970s and allows recovery of waste heat with less total complexity, but at the loss of the additional power and redundancy of a true combined cycle system.
Cogeneration or combined heat and power (CHP) is the use of a heat engine [1] or power station to generate electricity and useful heat at the same time. Cogeneration is a more efficient use of fuel or heat, because otherwise- wasted heat from electricity generation is put to some productive use.
Large (land-based) electric powerplants built using this combined cycle can reach conversion efficiencies of over 60%. [1] If the turbines do not drive a propeller shaft directly and instead a turbo-electric transmission is used, the system is known as COGES (combined gas turbine-electric and steam).
Emissions controls may also be located in the HRSG. Some may contain a selective catalytic reduction system to reduce nitrogen oxides (a large contributor to the formation of smog and acid rain) or a catalyst to remove carbon monoxide. The inclusion of an SCR dramatically affects the layout of the HRSG.
Some larger installations utilize combined cycle generation. Usually this consists of a gas turbine whose exhaust boils water for a steam turbine in a Rankine cycle. The condenser of the steam cycle provides the heat for space heating or an absorptive chiller. Combined cycle plants with cogeneration have the highest known thermal efficiencies ...
Load-following power plants can be hydroelectric power plants, diesel and gas engine power plants, combined cycle gas turbine power plants and steam turbine power plants that run on natural gas or heavy fuel oil, although heavy fuel oil plants make up a very small portion of the energy mix. A relatively efficient model of gas turbine that runs ...
Integrated gasification combined cycle (IGCC) is a coal-based power generation technology that uses a high-pressure gasifier to convert coal (or other carbon-based fuels) into pressurized synthesis gas (syngas). The gasification process allows the use of a combined cycle generator, typically achieving higher efficiency. IGCC also facilitates ...
The Cheng cycle is a thermodynamic cycle which uses a combination of two working fluids, one gas and one steam. It can therefore be considered a combination of the Brayton cycle and the Rankine cycle .