Cogeneration or combined heat and power (CHP) is the use of a heat engine or power station to generate electricity and useful heat at the same time. Trigeneration or combined cooling, heat and power (CCHP) refers to the simultaneous generation of electricity and useful heating and cooling from the combustion of a fuel or a solar heat collector. The terms cogeneration and trigeneration can be also applied to the power systems generating simultaneously electricity, heat, and industrial chemicals – e.g., syngas or pure hydrogen (article: combined cycles, chapter: natural gas integrated power & syngas (hydrogen) generation cycle). Source: Wikipedia
CHP generates electricity whilst also capturing usable heat that is produced in this process. This contrasts with conventional ways of generating electricity where vast amounts of heat are simply wasted. In today’s coal and gas-fired power stations, up to two-thirds of the overall energy consumed is lost in this way, often seen as a cloud of steam rising from cooling towers.
CHP is highly efficient
By using waste heat, CHP plants can reach efficiency ratings in excess of 80%. This compares with the efficiency of gas power stations, which range between 49% and 52%. Coal-fired plant fares less well with an efficiency of around 38%.
Common CHP Configurations
The two most common CHP system configurations are:
Combustion turbine, or reciprocating engine, with the heat recovery unit
Steam boiler with steam turbine
Combustion Turbine, or Reciprocating Engine, with Heat Recovery Unit
Combustion turbine or reciprocating engine CHP systems burn fuel (natural gas, oil, or biogas) to turn generators to produce electricity and use heat recovery devices to capture the heat from the turbine or engine. This heat is converted into useful thermal energy, usually in the form of steam or hot water.
Steam Boiler with Steam Turbine
With steam turbines, the process begins by producing steam in a boiler. The steam is then used to turn a turbine to run a generator to produce electricity. The steam leaving the turbine can be used to produce useful thermal energy. These systems can use a variety of fuels, such as natural gas, oil, biomass, and coal.
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