Ground Source Heat Pumps

Borehole Collector

Compact Collector

Horizontal Ground Collector

Ground source heat pumps is attracting greatest interest at present since it promises to deliver the best year-round energy-efficiency. The ground source heat pumps (GSHP) extracts heat stored in the ground. This is sometimes referred to as “geothermal”, however, the heat is mostly from the surface (solar gain), and very little is from the earth’s core.

At depths of 1m and more, the ground temperature does not deviate very much from the average summer/winter surface temperatures (around 9 -12C in the UK depending on location). At this depth, there is an enormous store of heat that can be usefully tapped for heating in the winter.

The most practical way of extracting this energy is to bury a large amount of pipe in the ground. This is usually laid in horizontal trenches at 1 – 2m depth, alternatively vertical bore-holes give similar results.

Water source

The water source should ideally be fairly close to the property, and should not require pumping up any significant height or the power for pumping it may detract from the energy savings. Having said that, water could be taken over considerable distances if the pipe diameter is big enough, especially in a downward direction. It is a relatively simple exercise to calculate the pump power required (if any) to get the water to and through the heat pump unit.

Permission should be sought from the relevant authorities as an abstraction licence may be needed.