Ground source heat pumps
Ground source heat pumps harness natural heat to provide hot water and heating. They do this by pumping water through underground pipes before using electricity to increase the temperature.
Benefits of ground source heat pumps
Ground source heat pumps offer significant cost savings when compared to a traditional fossil fuel boiler or direct electric heaters. This makes it easier to meet Part L Energy Efficiency building regulations for new builds. Even greater savings can be made when combining an air source heat pump with solar PV or solar thermal.
They also offer large reductions in carbon emissions due to reduced consumption of fossil fuels, and are zero carbon, when used with a 100% renewable electricity tariff.
Single heating system
A ground source heat pump can provide all the heating and hot water you need without the requirement for additional systems, even during the coldest winter months.
Ground source heat pumps offer longer heating periods for less money and automatically maintain more consistent room temperatures than the traditional intermittent heating from a boiler.
Ground source heat pumps do not burn fossil fuels, eliminating the risk of carbon monoxide poisoning and improving air quality.
Ground source heat pumps have an expected operating life of 20 years, with serviceable parts extending this further. Equipment is installed internally so is protected from the weather. The ground loop pipe is “fit and forget” with up to 50-year structural defect warranties from manufacturers.
Grant funding – Renewable Heat Incentive
Ground source heat pumps qualify for the Domestic Renewable Heat Incentive (RHI).
You can make tax savings (reduced rate: 5% VAT) with your air source heat pump and all associated goods for domestic installations (0% for domestic new build properties). There are also enhanced capital allowances for commercial purchases.
How do ground source heat pumps work?
Ground source technology
A correctly sized ground source heat pump is typically 400% efficient. The heat pump consumes 1kW of electricity to collect a large volume of low temperature energy from the ground. It compresses this energy to produce an equivalent 4kW of higher temperature heating and hot water.
Horizontal ground loops
Ground loops are installed within 1m deep trenches, providing a stable year round ground temperature. Fluid within the pipework is warmed up by the ground and brought back to the heat pump. Ground loops range from 200m to 300m or can be installed in a shorter slinky arrangement. Loops can also be installed within lakes or other bodies of water.
Standard groundwork costs of £5-£10/m mean that they are much cheaper to install than boreholes at £40-£60/m.
Loops require a lot of space. You need approximately twice the heated floor area to install an efficient collector. E.G. 400m2 of ground area to heat a 200m2 floor area.
Vertical borehole loop
U-tubes are installed within 80m-100m deep boreholes and operate the same way as horizontal loops. Boreholes require very little space so can be installed on smaller sites, or save land for future use such as additional buildings.
Loop and borehole design is critical. The heat pump needs to collect a sufficient volume of energy to be able to efficiently meet the heating and hot water demand of the building.
Ground water can also be extracted and used as the energy source. This can be installed at lower cost and provides high efficiencies. However, ground water volume and quality needs to be guaranteed which is not always possible.