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Combined Heat and Power
Overview
Conventional power stations operate at efficiencies between 30% and 50%. That is, only one
third to one half of the primary energy input is converted into electric power. The
remainder is given off as heat. Another 5% or so of electric power is lost in transmission
and transformation of electricity.
Decentralised solutions for the generation of power, in the form of combined heat and power
(CHP) stations, allow the heat which is given off during the generation of power to be used.
This can give an overall efficiency of over 80%. In other words, 80% of the primary energy
input to the system can be put to good use, some as electricity, the rest as heat.
There is rarely an exact balance between the heat and electricity requirements from a plant.
A distinction is, therefore, made between two types of operation: power-driven and heat-driven.
In the case of power-driven CHPs, the prime consideration is the production of electricity
when it is most profitable. In the case of heat-driven CHPs, considerations of the overall efficiency
are at the forefront; electricity is only generated when there is a use for the 'waste' heat.
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