Considerations before using CHP

When thinking about Combined Heat & Power (CHP), the first consideration should be whether the application requires the simultaneous need for electricity and heat over extended operating periods, typically more than 6,000 hours a year, or 17 hours a day. The longer the operating hours the greater the economic and environmental benefit delivered by CHP to the end user. Examples of applications include large chemical plants and paper mills, to smaller properties such as hotels, leisure centres, nursing homes and sheltered accommodation.

Thermally, the CHP unit should be selected to match the base heating load of the site to maximise the running hours. For engine based technologies such as the DACHS the key to success of the CHP scheme is integration with the building’s heating system. The CHP unit must be installed as lead heating appliance with existing or new boiler plant providing additional capacity to satisfy peak demand.

From an electricity generating perspective, the CHP unit should be selected to meet the site’s base load. This avoids or minimises the “spilling” or exporting of electricity to the grid network, which on many sites would not offer a financially viable proposition. The key to maximising the economic benefit of the CHP scheme is to utilise all the electricity generated on site. When operating in parallel with the local supply network, any electricity required above the output of the CHP unit would be imported from the grid network.