How 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, that can then heat water for the heating and hot water circuits of the house or business premises.

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 between 90m and 160m deep.

The space you need for a horizontal loop, and the depth you need for a borehole, will depend on many factors. We will provide advice on system design and layout following a site visit.

How the process works

  1. A cold water anti-freeze mix is pumped through the ground within a series of energy-absorbing pipes. These pipes are called a ground array. As heat naturally flows from warmer to cooler places, the anti-freeze mix circulating the array is constantly warmed by the ground’s low-grade heat.
  2. Having increased in temperature, the anti-freeze mixture is fed into a heat exchanger called the evaporator.
  3. Within the secondary sealed side of the evaporator heat exchanger is a refrigerant that acts as a heat transfer fluid. When the water anti-freeze mixture enters the evaporator, the energy absorbed from the ground is transferred into the refrigerant which begins to boil and turn into a gas.
  4. The refrigerant never physically mixes with the water anti-freeze mixture. They are separated like sandwich layers by the plates of the heat exchanger which permit the heat transfer.
  5. This gas is then fed into a compressor. The pressure of the refrigerant gas is increased in the compressor, causing the gas temperature rise.
  6. The hot refrigerant gas then flows into a second heat exchanger, called the condenser, which features an identical set of heat transfer plates.
  7. The condenser delivers water hot enough to serve the space heating system and the property’s hot water needs. Having transferred its heat, the refrigerant gas reverts to a liquid.
  8. This liquid is then passed through an expansion valve at the end of the cycle to reduce its pressure and temperature, ready to start the cycle again.
  9. 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.

Caplor Energy specifically partners with the UK’s leading manufacturer of Ground Source Heat Pumps, Kensa.

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