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Data Sheet:
Ground Source Heat Pumps - Vertical Data Sheet

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

Technical information

GSHPs utilise the heat energy stored in the ground to heat water that can be distributed to the heating systems, domestic hot water systems, and appliances within a building. The GSHP works by passing heat from the ground through buried pipework that carries a brine mixture that converts it into higher temperatures for use within the home.

A vertical closed loop and borehole system is composed of pipes that run vertically down into the ground. Holes are bored in the ground, typically 25–150m deep. Two pipes (pipe pairs) in the hole are joined with a U-shaped cross connector at the bottom, forming a continuous loop. The borehole is commonly filled with a heat conducting grout that surrounds the pipe to provide a thermal connection to the surrounding soil or rock to improve heat transfer. Vertical loop fields are typically used when there is a limited area of land available. Bore holes are spaced at least 10-15m apart and the depths depend on ground characteristics (which dictate the ability of the ground to generate heat) and building characteristics (which dictates the heating requirement itself).

Once installed, 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. In this, 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 and 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 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).

Main_borehole

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 draft proofed.

Ground Source Heat Pumps can work better in conjunction with the use of underfloor heating systems, as they produce low levels of heat which will reduce efficiency.

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