Ground Source Heat Pumps
Ground source heat pumps (GSHPs) use pipes that are buried in the garden to extract heat from the ground. This heat can then be used to heat radiators, underfloor or warm air heating systems and hot water in your home.
A ground source heat pump circulates a mixture of water and antifreeze around a loop of pipe, called a ground loop, which is buried in your garden.
Heat from the ground is absorbed into the fluid and then passes through a heat exchanger into the heat pump.
The ground stays at a fairly constant temperature under the surface, so the heat pump can be used throughout the year.
The length of the ground loop depends on the size of your home and the amount of heat you need.
Longer loops can draw more heat from the ground, but need more space to be buried in. If space is limited, a vertical borehole can be drilled instead.
The benefits of ground source heat pumps
Could lower your fuel bills, especially if you replace conventional electric heating
Could provide you with income through the government’s Renewable Heat Incentive
Could lower home carbon emissions, depending on which fuel you are replacing
No fuel deliveries needed
Can heat your home as well as your water
Minimal maintenance required
Unlike gas and oil boilers, heat pumps deliver heat at lower temperatures over much longer periods.
During the winter they may need to be on constantly to heat your home efficiently. You will also notice that radiators won't feel as hot to the touch as they might do when you are using a gas or oil boiler.
Air Source Heat Pumps are usually easier to install than ground source as they don't need any trenches or drilling, but they are often less efficient than ground source heat pumps.
Water source heat pumps can be used to provide heating in homes near to rivers, streams and lakes.
How do ground source heat pumps work?
Heat from the ground is absorbed at low temperatures into a fluid inside a loop of pipe (a ground loop) buried underground. The fluid then passes through a compressor that raises it to a higher temperature, which can then heat water for the heating and hot water circuits of the house.
The cooled ground-loop fluid passes back into the ground where it absorbs further energy from the ground in a continuous process as long as heating is required.
If there is enough space, the collector loop can be laid horizontally in a trench about a metre or so below ground. Where there isn’t room to do this you can drill vertical boreholes to extract heat from much further down, typically 90 – 160 metres deep.
The space you need for a horizontal loop, and the depth you need for a borehole, will depend on many factors – your heat pump installer will design the collector array based on local conditions and the heat requirements of your home.
Heat pumps have some impact on the environment as they need electricity to run, but the heat they extract from the ground, the air, or water is constantly being renewed naturally.