Ground Source Heat Pumps

Geothermal energy involves tapping into the heat generated by the Earth's absorption of the heat radiated by the Sun. Ground Source Heat Pumps (GSHP) extract this energy, and transfer it into a building for space and water heating, They can also remove heat from a building and deposit it into the ground to cool the building during hot weather.

According to The Carbon Trust's Renewable Energy Sources Technology Overview, "The heat is collected through a series of underground pipes laid about 1.5m below the surface, or from a borehole system. In both of these options, water is re-circulated in a closed loop underground and delivered to the heat pump, which is usually located inside the building. Heat pumps cover a wide range of capacities, from a few kw to many hundreds of kw machines that heat or cool large, multi-storey buildings."

The Energy Saving Trust's detailed guidance recommends careful consideration of the costs and benefits, noting that capital costs may be higher, although running costs may be lower, than for many other types of heating.

Site suitability will be determined by local geological conditions, but, as with many technologies, they are cheaper to install in a new build than to retrofit. The system requires accurate calculations, and the length of loop required needs to be determined exactly - adding a ‘safety margin' is not recommended.

The Energy Savings Trust's guide to installation is downloadable from www.est.org.uk/uploads/documents/housingbuildings/ce82.pdf