Combined heat and power CHP
Combined heat and power (CHP), sometimes referred to as cogeneration, is a process in which the heat that is created as a by-product of power generation is captured and used rather than simply being wasted.
According to the Combined Heat and Power Association, “In today’s coal and gas fired power stations, up to two thirds of the overall energy consumed is lost in this way, often seen as a cloud of steam rising from cooling towers.”
Whilst there are a range of different forms of CHP, typically, a gas-powered turbine or reciprocating engine is used to produce electricity, and the heat recovered is used for local water or space heating, or to support an industrial process. Increasingly absorption cooling can use the heat recovered to produce cooling. Sometimes this process is referred to as trigeneration or combined cooling, heat and power (CCHP).
Alternative systems have heat generation as their primary function, and then use a steam turbine to generate electricity.
CHP as a process is not dependent on a specific fuel and so renewable fuels such as biomass feedstocks can be used.
Very broadly, CHP is appropriate in circumstances where there is a continuous local demand for heat and power, such as district heating schemes, hotels and leisure centres, industrial applications that require heat for manufacturing processes and so on. If excess electricity is generated, this can be exported back to the national grid.
The Department of Energy and Climate Change (DECC) lists the advantages of CHP as:
- An efficiency of over 80%, compared to 38% for a coal-fired power station.
- Up to 30% savings on energy bills.
- Up to 30% reduction in carbon emissions.
- Reduced transmission and distribution losses.
- Increased fuel supply security.
CHP can be a very significant investment and requires careful consideration. However, where they are certified as Good Quality (GQ) CHP, they are exempt from the Climate Change Levy for fuel inputs and electricity outputs. They may also qualify as Enhanced Capital Allowances (ECA) and be eligible for business rates exemption.
CHP plant can be manufactured as packaged units or can be custom designed and built. Increasingly, micro CHP units can be used to supply small-scale and domestic needs. In effect, these replace conventional boilers. Heat is the primary output of micro CHP, with the ratio of heat to electricity for domestic appliances typically around 6:1, generating up to 1kW of electricity. As with larger CHP plant, if excess electricity is generated, this can be exported back to the national grid. This may be eligible for Feed-in Tariffs in England and Wales and is considered an ‘eligible measure’ suitable for funding under the Green Deal.
[edit] Related articles on Designing Buildings
- Big growth in district heating markets - now and on the horizon.
- Biomass.
- Biomass CHP.
- BSRIA guide to heat interface units.
- Capital allowances.
- Can the Zeroth Energy System reduce the carbon footprint of HVAC services?
- Carbon capture and storage.
- Coefficient of Performance CoP.
- Community energy network.
- District energy.
- Fuel cell.
- Future of electricity in domestic buildings.
- Green Deal.
- Heat pump COP & EER and central plant SCOP in ambient loops.
- Heat Networks Investment Project HNIP.
- Liquefied petroleum gas (LPG).
- Low Carbon Energy Centre, London.
- Low carbon heating and cooling.
- Microgeneration.
- Micro-CHP.
- Micro-grid.
- On-site generation of heat and power.
[edit] External references
Featured articles and news
Professional practical experience for Architects in training
The long process to transform the nature of education and professional practical experience in the Architecture profession following recent reports.
A people-first approach to retrofit
Moving away from the destructive paradigm of fabric-first.
International Electrician Day, 10 June 2025
Celebrating the role of electrical engineers from André-Marie Amperè, today and for the future.
New guide for clients launched at Houses of Parliament
'There has never been a more important time for clients to step up and ...ask the right questions'
The impact of recycled slate tiles
Innovation across the decades.
EPC changes for existing buildings
Changes and their context as the new RdSAP methodology comes into use from 15 June.
Skills England publishes Sector skills needs assessments
Priority areas relating to the built environment highlighted and described in brief.
BSRIA HVAC Market Watch - May 2025 Edition
Heat Pump Market Outlook: Policy, Performance & Refrigerant Trends for 2025–2028.
Committing to EDI in construction with CIOB
Built Environment professional bodies deepen commitment to EDI with two new signatories: CIAT and CICES.
Government Grenfell progress report at a glance
Line by line recomendation overview, with links to more details.
An engaging and lively review of his professional life.
Sustainable heating for listed buildings
A problem that needs to be approached intelligently.
50th Golden anniversary ECA Edmundson apprentice award
Deadline for entries has been extended to Friday 27 June, so don't miss out!
CIAT at the London Festival of Architecture
Designing for Everyone: Breaking Barriers in Inclusive Architecture.
Mixed reactions to apprenticeship and skills reform 2025
A 'welcome shift' for some and a 'backwards step' for others.
Comments
To start a discussion about this article, click 'Add a comment' above and add your thoughts to this discussion page.