Ground Source Heat Pumps

A ground source heat pump takes advantage of the natural heat produced by the earth to provide a domestic property with heat and hot water.

How do ground source heat pumps work?

The temperature of the earth several meters below ground remains at a constant heat no matter the weather above ground. In the UK, this heat is approximately 10 – 15 degrees Celsius. Like the sun’s power, this heat (or energy) is a renewable and natural source which can be harnessed to heat your home and provide hot water.

A ground source heating system consists of three main parts and functions:

Ground loop - This absorbs heat from the earth. The heat is absorbed from the soil by using a network of plastic pipes which are laid in the ground in horizontal trenches or boreholes, which have been dug to a depth of two metres below ground level.

These pipes contain a water and antifreeze mixture which absorbs the heat from the ground and transports it around the pipe circuit.

Heat pump – A device which physically moves the water around the loop. The heat pump is made up of three parts – the evaporator, the compressor and the condenser. As the fluid moves around the pump it changes to gas as it heats up and later condenses to liquid as it is distributed to where it is needed.

The heat pump relies on electricity to run. However, the level of thermal energy, or heat, emitted is three to four times the amount of electrical energy needed to power the pump.

Heat distribution system – This is used to extract the heat and then releases it into a building. A heat distribution system can be radiators or under floor heating. For hot water supply, it is the cylinders used for water storage.

A ground source heat pump offers a typical CoP of three to four.

The benefits of ground source heat pumps

Using a renewable central heating source is both effective and environmentally friendly. Depending on the type of fossil fuel you replace your ground source heating system with, you can cut your households CO2 emissions by two to eight tonnes each year. This technology also qualifies for the upcoming Renewable Heat Incentive.

Ground source heating can be used all year round – in the winter to heat a home and in the summer to cool it if the operation is run in reverse. The system can also be used for domestic hot water, when the temperature of the water in the cylinder is topped up using an immersion heater.

Another benefit is a life expectancy of over 50 years, plus low maintenance.

The negatives of ground source heat pumps

Heat pumps are not recommended if a building is poorly insulated. In addition to this, a ground source heat pump requires substantial space to install the pipework.

Larger radiators are more effective when using ground source energy as they distribute more heat.

Ground source heat pump systems cost around £9,000 – £17,000. However, with an annual saving of around £400 – £800 on heating bills, it is a good long-term investment.