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Data Sheet:
Ground Source Heat Pumps - Horizontal Data Sheet

Information suitable for:
New build
Retrofit
  • Sustainable
  • Energy saving
  • Renewable energy
  • Responsible sourcing
  • Water saving

Technical information

GSHPs utilises the heat energy stored in the ground to heat water that can be distributed to the taps, appliances and heating systems within a building. The GSHP works by passing the low energy heat captured from the ground through a refrigerant cycle that converts it into higher temperatures for use within the home. The heat is collected via means of a loop array that may be placed in a trench (c.1.5-2m deep). GSHPs can also be used for summer cooling.

A horizontal closed loop field is composed of pipes that run horizontally in the ground. A long horizontal trench, deeper than the frost line, is dug and U-shaped or slinky coils are placed horizontally inside the same trench. Horizontal loops tend to be more cost effective to install, but are generally less efficient than vertical or radial loops due to the fact that they are more susceptible to seasonal performance fluctuations near the surface and can be at higher risk of post installation damage. Furthermore, a large plot is required in order to excavate the required trenches. The excavation of the trenches can also result in considerable disruption and require extensive landscaping post installation. The land is also rendered unfit for any development over a large area for the benefit of just one GSHP installation.

Once installed the GSHPs offer a reliable and low cost form of heating requiring only relatively small amounts of electricity to drive the pumps. Heat pumps aim to supply a constant temperature to buildings. They initially heat the building and then top-up any heat loss on a constant flow basis.

The efficient design of GSHPs is critical to their good and long term performance and an understanding of both the ground, groundwater conditions and available drilling techniques is crucial in this. Mostly, the heat absorbed is solar heat stored in the surface of the earth but at depth, it is likely to be a mixture of solar and planetary heat. For the majority of GSHP implementation stored solar heat is the major heat source.

This heat is then passed onto the heat pump unit, which compresses the liquid further (the Law of Thermodynamics) creating an even hotter liquid, which is then used to heat the water in the water tank. This heat can then be transferred to radiators and under-floor heating systems, as well as being used to heat water.

The length of the ground loop depends on the size of the building, its energy performance and the sub-surface ground conditions.

The pump will still need electricity to run, but the idea is that it uses less electrical energy than the heat it produces. This is called the co-efficient of performance (COP).

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Hints and Tips

For each Ground Source Heat Pump installation we recommend that you undertake an independent assessment of the site to ensure your design is optimised to suit the ground conditions and building.

For optimum results you need to ensure that the fabric of the building is well insulated and draught proofed.

Ground Source Heat Pumps can work better in conjunction with the use of under floor heating systems.

Ensure that the sun has access to the area of the ground where the loop is situated.

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