Combined heat and power (CHP) integrates the production of usable heat and power (electricity), in one single, highly efficient process.
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 is 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. See the ‘CHP – capturing heat and cutting waste’ breakout box for more detail about these losses.
Their relative sophistication means that the overall efficiency of CHP plants can reach in excess of 80% at the point of use. This compares with the efficiency of CCGTs, which in the UK which ranged between 49% and 52% over the period 2006 to 2008. Coal-fired plant fare less well with an efficiency of around 38%.
As an energy generation process, CHP is fuel neutral. This means that a CHP process can be applied to both renewable and fossil fuels. The specific technologies employed, and the efficiencies they achieve will vary, but in every situation CHP offers the capability to make more efficient and effective use of valuable primary energy resources.
CHP plants generally meet local energy needs; certainly heat, also power and increasingly cooling. As such, it normally also avoids additional efficiency losses of around 7% incurred through transmission and distribution of electricity through the National Grid and local distribution networks – as energy is lost travelling long distances to reach its end user. When taking account of these losses, the respective efficiencies of both coal and CCGT plant fall further at the point of use.