What is a Ground Source Heat Pump (GSHP) and how does it work?
A Ground Source Heat Pump works by absorbing heat from under the ground. Heat from the sun is stored in the ground.
This in turn means the ground is at a constant 10° to 11°celcius all year round. A ground loop (pipe)
is fitted between one to two meters below ground level. This loop is filled with a mixture of
antifreeze and water and this is circulated through the ground. When in circulation the mixture
absorbs the ground heat. This heat is then sent through a heat exchanger to the heat pump where
the heat is compressed and lastly sent to the heat distribution system i.e. radiators or underfloor
heating and hot water.
For the ground loop to be fitted trenches need to be dug. The length of the trenches depends on the
size of the system which in turn depends of the size of the home or building and the type of
distribution system. This is worked out when the site assessment is carried out. The Ground loop is
most commonly a horizontal loop between one and two meters below ground level, however is
space is an issue due to urban location a vertical loop could be fitted (planning permission may be
required). Vertical loop systems usually go to depths between 50 and 150 meters below ground.
A GSHP works best with low temperature radiators or underfloor heating. This is because the heat
pump manages to reach temperatures of around 50° and this is slightly lower than a conventional
gas boiler which is around 65°. This in turn means the GSHP works more efficiently with underfloor
heating and larger radiators.
GSHP emit 0 C02 gases and if the electricity used to run the pump is from a renewable supplier than
it can be said that the pumps have absolutely 0 carbon footprint.
GSHP are part of the Renewable Heat Incentive (RHI). The stunning 20.89p per KW hour is paid by
the RHI. For a standard 4 bedroom detached house this is estimated to be in the region of £2,300 –
£3,000 per year. For further information on the RHI please click here.
A GSHP is costly to install however due to the RHI tariff they usually pay for themselves. It also needs
to be taken into account that GSHP are 50% to 70% more efficient compared to gas boilers and
general convection heating systems.
Because of the space needed for a GSHP to be fitted they are more suited to rural houses and new
build houses where the cost of the pump can be incorporated into the build cost.