Ground Source Heat Pumps

By Katie Anderson on August 2nd, 2011

Ground Source heat pumps enable you to heat your home with natural heat absorbed from the ground, providing you with heat and hot water.

A ground source system – also known as geothermal heating – can be used all year round, because beneath the surface, the ground stays at a fairly constant temperature. This means that the outside temperature isn’t a contributing factor, and heat pumps will be capable of working, even in the midst of a harsh winter.

The heat pump works by using pipes that are buried in the ground to extract heat, which is usually used to heat underfloor heating systems or radiators, and to provide hot water.

Ground source heating systems are made up of three parts: a ground loop, a heat pump and a heat distribution system:

  • Ground loop – this is a loop of plastic pipe, normally laid flat or coiled in trenches about two metres deep. In situations where there is not enough space, it is possible to install a vertical loop down into the ground to a depth of up to 100 metres, in the case of a typical domestic home.
  • Heat pump – is a device which moves the water around the loop. Heat pumps are made up of three parts – the evaporator, the compressor and the condenser.
  • Heat distribution system – can be under floor heating or radiators, and is used to extract the heat before releasing it into a building.

How do ground source heat pumps work?

1. The heat pump circulates a mixture of antifreeze and water around a loop of plastic pipe known as a ground loop, which is buried in the ground. The pipes are laid in the ground in horizontal trenches (or boreholes) dug to a depth of two metres below ground level.

2. Heat from the ground gets absorbed into this fluid and is pumped through a heat exchanger in the pump, transporting it around the pipe circuit.

3. Low grade heat that is passed through the heat pump compressor is concentrated into a higher temperature of useful heat, which is capable of heating water for the heating and hot water circuits of the house.

4. Ground loop fluid passes back into the ground to absorb further energy.

Would a ground source heat pump be viable for my home?

If you’re interested in installing a ground source heat pump, there’s a few points worth considering, including:

  • It is important to have a well insulated home for a ground source heating system to be most effective, due to the fact that heat pumps produce a lower temperature heat than traditional boilers.
  • With heat pumps, large radiators or underfloor heating systems perform better than standard radiator-based systems, due to the lower water temperatures required. So you’ll need to take into consideration what type of heating system you’ll be using.
  • Whilst your garden doesn’t have to be a large area, the ground does however need to be suitable for digging a borehole or a trench. It also needs to be accessible for the digging machinery required.
  • Ground source heat pumps will be able to save you more on heating bills if you are replacing an electric or coal heating system. Heat pump systems are not recommended for homes connected to the gas network.

Costs and savings

The installation of a typical ground source heating system can range from around £9,000 to £17,000.

The amount of money you can save by installing a geothermal heating system depends on a variety of factors, including fuel prices and what sort of system you are using to distribute heat. Things like temperature setting and learning how to use the system’s controls effectively will also factor in to the savings you can achieve.

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