CHP or CCHP
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In conventional power stations heat is usually rejected to the atmosphere, losing over 45% of the energy generated. Further losses occur in the transmission of electricity over long distances. Combined heat and power (CHP) systems work by generating electricity near or on-site, capturing the heat for space and water heating. CCHP systems use some of the heat to drive an absorption chiller, which provides. Small scale CHP can be used for individual buildings, or larger systems for community heating. Existing power stations can be converted to provide heat via district heat networks.
Type
- Various fuels: gas, biogas, diesel, bio-diesel, biomass, waste
- Various sizes
Other components
- Heat store, such as large hot water cylinder
- Heat network for community schemes, including heat interface units for end users, eg per dwelling
- Additional boilers for peak heat demand
- Absorption chillers for CHP
- External flue for exhaust gases, above the roofline
Typical saving
Fossil fuel CHP can reduce primary energy use and emissions by 35% compared to conventional power stations and boilers. Biofuel CHP emissions savings can approach 100%.
Indicative cost
With good use of the heat produced, CHP is economical due to fuel savings compared to conventional heat and power supply, and can attract investment, eg from ESCOs. The payback can be 3-5 years with maintenance costs met by ongoing savings. District heating infrastructure can be very costly.
Main issues affecting feasibility
- Heat demand: Year-round heat demand required for efficient operation.
- Fuel source: Local, sustainable fuel source should be used to reduce transport and other associated impacts. May not suit city centre locations.
- Emissions: Nitrous oxide emissions can be higher than gas boilers.
- Management: Provision needed for long term management of equipment and sales of heat and electricity. ESCOs may provide this service.
