Co-generation
Cogeneration (also combined heat and power or CHP) is the use of a power station to simultaneously generate both heat and electricity. CHP allows a more total use of energy than conventional generation, potentially reaching an efficiency of 70-90%, compared with approximately 50% for conventional plants. This means that less fuel needs to be consumed to produce the same amount of energy.
Thermal power plants (including those that use uranium or burn coal, petroleum, or natural gas) do not convert all of their available energy into electricity. Inevitably, a large amount of heat is released as a by-product. Conventional power stations emit this heat into the environment through cooling towers, as Gas turbine CHP plants using the waste heat in the flue gas of gas turbines
Small cogeneration units for hospitals, swimming pools or groups of dwellings are also economic if standardized, mass-produced CHP plants are used. Examples are the internal combustion (IC) engines (gas or diesel engines) used for car manufacture. They use the waste heat in the flue gas and cooling water of gas or diesel engines and replace the traditional gas- or oil-fired boiler (furnace) used in central heating systems.
Generating high-temperature heat (e.g. from industrial processes) usually results in some wasted low-temperature heat, which is simply dumped into the environment. A CHP system can also be used to recover some of this waste heat and to use it to generate electric power. For small systems, the waste heat can be recovered by a Stirling engine.
A problem with cogeneration is that heat transmission over long distances requires thick, heavily insulated pipes, whereas electricity can be transmitted along a comparatively simple wire.
See also
