Micro Combined Heat and Power (mCHP)
What is it?
This refers to a heating technology which generates heat and
electricity simultaneously, from the same energy source, in
individual homes or buildings. This contrasts with conventional
ways of generating electricity where vast amounts of heat is simply
wasted.
Whilst strictly not renewable, as currently CHP installations
burn gas or oil as a heating fuel, it is considered a ‘low carbon
technology’ because of it’s efficiency in providing both heat and
electricity.
How does it work?
There are 3 main micro-CHP technologies. The difference is the
way in which they generate electricity, which can be done in the
following ways:
- Stirling engine
- Fuel cell
- Internal combustion engine
Stirling Engine micro-CHP
Stirling engines are typically for buildings with smaller heat
demands and would be appropriate for domestic applications in the
UK. The latest Stirling engine based micro CHP units allow
electricity to be generated sooner after being turned on, and are
more efficient at producing heat.
Fuel cell
CHP technology is new to the market in the UK and globally. Fuel
cells work by taking energy from fuel at a chemical level rather
than burning it.
Internal combustion engine
CHP is the most proven technology. These are essentially, and
sometimes literally, truck diesel engines modified to run on
natural gas or heating oil, which are connected directly to an
electrical generator. Heat is then taken from the engine’s cooling
water and exhaust manifold. Generally they produce twice as much
heat as electrical power and have, to date, been primarily used in
larger commercial-scale applications in the UK.
Systems consist of one of the above, a generator to produce
electricity, a heat recovery system to obtain the useable heat from
the engine, a cooling system to dissipate heat, combustion and
ventilation air systems to provide fresh air and remove exhaust
air, a control system to maintain safe and efficient operation and
lastly an enclosure to provide a physical barrier and form of
protection.
Most domestic micro CHP systems will have two burners, one small
(engine burner) and one large (supplementary burner). If you want
hot water only then the boiler will use the small burner, and
generate electricity at the same time. However, if you want to heat
hot water and water for space heating at the same time the boiler
may have to use the larger burner, which uses more gas, but will
not produce any additional electricity.
Electricity generation comes second to the production of heat
(typical ratio of about 6:1 for domestic appliances) i.e. –
electricity is only generated when heat is produced.
Is it suitable?
- A micro-CHP unit resembles a gas condensing boiler and can be
wall hung, or floor standing.
- Installation is easy, however an electrician will also be
required. Existing radiators do not need to be replaced.
- Servicing costs and maintenance are estimated to be similar to
a standard boiler – although a specialist will be required.
- Electricity is only generated when heat is produced, therefore
in the warmer months when you do not heat your home you will have
to draw more electricity from the grid.
- The carbon saving potential of Micro-CHP has been found to be
best in buildings which require long and consistent heating
periods, i.e. care homes, hotels etc.
- CHP may be an option for hard to treat properties (ie. Solid
wall, older buildings) which have a higher than normal heat load
and cannot easily/ cost effectively be insulated.
What are the benefits?
A typical micro CHP until will deliver the same comfort levels
as a conventional boiler.
A reduction in electricity bills, as you only need to draw on
electricity from the National Grid when heating is not required. A
typical domestic system is expected to have the potential to
generate up to 1kW of electricity per hour once warmed up. This
would be enough to power the lighting and appliances in a typical
home. The amount of electricity generated ultimately depends on how
long the system is running.
Noise levels are comparable with conventional central heating
systems.
Micro CHP systems installed by an accredited contractor (MCS
approved) can earn you money from the Government’s Feed in Tariff Scheme (FITs).
Contact Us
Climate Change Officer
Property, Leisure and Waste Management
White Cliffs Business Park
Dover
Kent CT16 3PJ
Email: energy@dover.gov.uk
