Geothermal energy: ground source heat pumps

Geothermal energy and ground source heat pumps (GSHPs) provide a means to access and use the heat energy that is contained naturally in the ground.

GSHPs use underground pipes to transfer heat from the ground to the inside of a building to provide heating, hot water or cooling. Water and anti-freeze is pumped around these pipes to absorb underground heat, which is then delivered to the heat pump.

GSHPs use a renewable heat source, but their heat exchangers must be driven by gas or electricity. They are therefore only classified as a renewable energy technology when the power used to drive them is supplied by a renewable energy source, such as a wind turbine.

Geothermal energy can be derived from geologically suitable areas where heat from the earth's core rises to the surface as hot springs or steam. The energy can be accessed by drilling boreholes into the ground and can provide heating or hot water. In some cases it is used to drive geothermal power plants.

Advantages of GSHPs

You can also drive GSHPs in reverse to provide cooling.
GSHP technology is well established.
GSHPs can be used to supplement a traditional boiler system.
Planning permission is not always required, although you should always check with your local area planning office.

Disadvantages of GSHPs

Installing a GSHP requires significant civil engineering works, so it is easier to install a GSHP at the build stage.
The initial installation of GSHPs is relatively expensive; payback periods can vary from 8-15 years.
GSHPs are not in themselves classed as a renewable energy technology. In order to be truly renewable, the power used to run them must be supplied by a renewable energy source.
Geothermal energy is extremely site specific.

Environmental authorisations for closed loop pumps

Closed loop GSHPs pump water and anti-freeze around a self-contained underground piping system. The mixture contained in the piping system absorbs the heat contained within the ground and transfers it to a building via a heat exchanger.

You need authorisation from the Northern Ireland Environment Agency (NIEA) or the Scottish Environment Protection Agency (SEPA) to install a closed loop pump if:

drilling underground causes groundwater from different underground strata to mix together
your pump causes changes in groundwater temperature
your pump is at risk of causing groundwater pollution.