Combined Heat and Power
Combined Heat And Power
Find out more about domestic (micro) combined heat and power systems
heating | energy efficiency | biomass | generalWhen
electricity is generated by burning fuel such as gas or coal in power stations, the main byproduct of generation -
heat - is often wasted. However, some commercial generators and districts around the world actually distribute the heat generated so that it can be used locally for
hot water and/or home and office heating. Such a system design is known as
combined heat and power or
cogeneration and offers a great leap in efficiency over standard electricity generation and heating systems.
Note also that if the fuel burned is waste
biomass, or wood chips for example, then it is possible to generate both electricity
and heat in a relatively
carbon neutral manner - the only
carbon footprint coming from transporting the
fuel to the generator rather than from the (carbon-neutral) fuel itself.
Domestic Combined Heat and Power
Micro-CHP is the name commonly given to combined heat and power systems designed for use in individual homes - acting as a mini
power station. These are typically set up to burn mains gas and generate both heat and power.
At the centre of a micro-CHP system is a
Stirling engine - a form of
external combustion engine which converts heat (generated by burning gas) into mechanical power (used to turn a turbine to
generate electricity).
Since the maximum electricity output is usually just 1-2kW (compared to the 3kW required by just one kettle, and much more by an electric oven), a micro-CHP system is usually treated as a "
boiler which generates electricity" - i.e. it will make all the hot water you need to run baths and showers, central heating, and/or
under floor heating as per a standard boiler, while also
generating electricity.
In order to work
efficiently, a micro-CHP system should ideally be left running all the time (unlike modern combi-boilers which fire up each and every time the hot tap is turned on). By connecting the system to the National Grid, generated electricity (which is typically cheaper than mains electricity per unit) can be exported 24 hours per day making the home-owner some
money, and hot water is always available.
Gas burned in a micro-CHP system generates electricity very efficiently - more efficiently than centralised gas-fueled power stations. By generating and using the electricity at home, there are no
transmission losses so overall efficiency is even better. The efficiency of a
micro-CHP system can be over 85% which compares very favourably to the best conventional power stations which manage just 50-60% efficiency. The electricity, if not used in your home, will likely be used by one of your neighbours, so although they will not notice the difference, they will be using more efficiently generated and transmitted electricity!
More Information
For more information about
combined heat and power in the UK, click here to visit the website for the
Combined Heat and Power Association.
Click here to view the
Wikipedia article on
Cogeneration.
Article Last Modified: 10:27, 31st Mar 2009Comment on this Article
If you have any comments on this article, please email them to
neil@reuk.co.uk.
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