CHP (Combined Heat and Power)
Simultaneous generation of electricity and useful heat from one fuel input, reaching total efficiencies of 75–90% versus about 35–60% for power-only plants.
Combined heat and power, or cogeneration, captures heat that a conventional power station would reject to cooling towers or rivers and uses it for district heating, industrial process steam or building heat. Prime movers include gas engines, gas turbines with heat-recovery steam generators, steam turbines (back-pressure or extraction-condensing), and fuel cells.
Power-to-heat ratio = E_elec / Q_heat
Example gas engine: 42% electric + 45% heat = 87% total (LHV)
Primary energy saving (EU Directive 2012/27): PES = 1 - 1 / (η_heat/η_ref,heat + η_el/η_ref,el)
Typical electrical efficiencies: reciprocating gas engines 35–45%, combined-cycle CHP 40–50%, biomass steam CHP 20–30%. Power-to-heat ratios range from about 0.3 (back-pressure steam) to 1.2 (combined cycle).
The benefit depends on finding a steady heat demand near the plant. Under the EU framework, "high-efficiency cogeneration" must save at least 10% primary energy against separate production. Denmark, Finland and the Netherlands generate a large share of electricity from CHP. As heating electrifies, fossil CHP faces competition from large heat pumps, but biomass and waste CHP remain important; flexible CHP with thermal storage can follow power prices.
Related terms
All terms →- District heating
A network of insulated pipes distributing hot water or steam from central heat sources to many buildings for space heating and hot water.
- Heat rate
The fuel energy a thermal power plant consumes per kWh of electricity generated; the inverse of efficiency, usually in BTU/kWh or kJ/kWh.
- Combined-cycle gas turbine (CCGT)
A power plant that runs a gas turbine and uses its hot exhaust to raise steam for a second, steam turbine, reaching electrical efficiencies of 55–64%.
- Primary energy
Energy in its raw natural form before conversion, such as crude oil, coal, natural gas, uranium, biomass, and the electricity or heat from renewables.
- Natural gas
A fossil fuel composed mainly of methane, used for power generation, industrial and residential heat, and as a chemical feedstock for hydrogen and ammonia.
- Thermal energy storage
Storing energy as heat or cold, in sensible, latent (phase-change) or thermochemical form, for later use as heat or for power generation.