A few metres beneath the surface, the ground keeps a constant temperature of about 11 degrees centigrade. Ground source heat pumps (GSHPs) take advantage of this constant temperature to extract the geothermal heat they need.
Loops of pipework are buried underground, either in long or coiled pipes in trenches (1-1.5 metres deep) or a long loop inserted into a vertical borehole (typically between 100-250 metres).
The pipes contain fluid which absorbs geothermal heat and passes it to a refrigerant which is then compressed to raise its temperature. A heat exchanger then extracts the heat and transfers it to central heating and hot water systems.
The ground stays at a constant temperature ensuring the heat pump can be used throughout the year.