Ground Source Heat Pumps (GSHP) utilise the heat energy stored in the ground to heat water that can be distributed to the heating system, domestic hot water system and appliances within a building. Horizontal collectors are laid underground in trenches (compared to bore holes in vertical systems). The GSHP works by passing heat from the ground through buried pipework that carries a brine mixture which converts it into higher temperatures for use within the home.
GSHPs utilise the heat energy stored in the ground to heat water that can be distributed to the heating system, domestic hot water system and appliances within a building. The GSHP works by passing heat from the ground through buried pipework that carries a brine mixture which converts it into higher temperatures for use within the home.
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 coils are placed horizontally inside the same trench. Horizontal loops tend to be more cost effective to install than boreholes.
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 buffer tank. This heat can then be transferred to radiators and under-floor heating systems, as well as being used to heat domestic hot water.
The length of the ground loop array depends on the heat demand, 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).
Hints & 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.