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How does CHP work?

CHP is a very efficient technology for generating electricity and heat together. A CHP plant is an installation where there is simultaneous generation of usable heat and power (usually electricity) in a single process. The term CHP is synonymous with cogeneration and total energy, which are terms often used in the United States or other Member States of the European Community. The basic elements of a CHP plant comprise one or more prime movers usually driving electrical generators, where the heat generated ln the process is utilised via suitable heat recovery equipment for a variely of purposes including: invading: industrial processes, community heating and space heating.

CHP can provide a secure and highly efficient method of generating electricity and heat at the point of use. Due to the utliisation of heat from

electricity generation and the avoidance of transmission losses because electricity is generated on site, CHP typically achieves a 35 per cent reduction in primary energy usage compared with power stations and heat only boilers. This can allow the host organisation to make economic savings where there is a suitable balance between the heat and power loads. The current mix of CHP installations achieves a reduction of over 30 per cent in C02 emissions in comparison with generation from coal-fired power stations, and over 10 per cent in comparison with gas fired combined cycle gas turbines. The newest Installations achieve a reduction of over 50 per cent compared with generation from coal-fired power stations.

CHP installations by capacity size ranges in 1996.

Electrical capacity size range.

Number of installations.

Share of total.

Total electricity capacity.

Share of total.

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Less than 100 kWe

Grater than

Since 1988 capacity has almost doubled, representing an average growth rate over the period of 9 per cent per annum. Growth over the last year has been lower than this at 2 per cent with an increase of 71 MWe. Growith depends on the rate of retirement of old plant as well as the rate at which

new plant are built.

CHP installations are dominated by schemes with an installed electrical capacity of less than 100 kWe (50 per cent of sites), and between 100 kWe and 999 kWe (34 per cent of sites). However, schemes larger than 10 MWe represent represent 79 per cent of the total electrical capacity. It is estimated that the total number of sites with CHP in the UK in 1996 was l,336 with a total installed capacity of 3,562 MWe. Of these, 304 sites (86 per cent of capacity) are in the industrial sector and 1,032 sites (14 per cent of capasity) are in the commercial, public and residential sectors.