What is combined heat and power (CHP)?
Combined heat and power (CHP), also called cogeneration, is producing electricity and useful heat at the same time in a single installation. In a conventional power station a large share of the fuel energy is lost as waste heat through cooling towers or cooling water. CHP uses that heat for space heating, hot water or industrial processes. In Dutch it is called “warmtekrachtkoppeling” (WKK).
How does it work?
An engine or turbine, usually running on natural gas or biogas, drives a generator. Heat from the exhaust, cooling water and lubricating oil is recovered through heat exchangers and sent to a heating system, a heat network or a process. Because both outputs are used, CHP achieves a higher overall efficiency than producing electricity in a power station and heat in a boiler separately.
Applications
- Greenhouses: heat for the glasshouse, CO₂ from cleaned flue gas for plant growth, and electricity for lighting or the grid.
- Hospitals, leisure centres and industry: buildings with a large, steady heat demand.
- District heating: large CHP plants supply heat networks.
- Micro-CHP: small units for homes, replacing a boiler.
Pros and cons
Advantages: better use of fuel and lower CO₂ emissions than separate generation with the same fossil fuel; electricity is generated locally.
Disadvantages: usually still gas-fired; only economic with a large, constant heat demand; engines need more maintenance than boilers. Compared with a heat pump on renewable electricity, the advantage shrinks.
Tips
- Size on heat demand, not electricity demand.
- Combine with a thermal store so the unit runs for long periods.
Related terms
- Central heating boiler
- Heat network
- Heat exchanger
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