During the summer, the sun warms the ground and heat is stored in the soil. This heat is collected by burying plastic collector pipes known as a surface ground collector or horizontal ground collector, 1 metre under the surface with each length at least 1 metre apart. An environmentally-friendly non-freezing solution is circulated in the surface ground collector, collects this heat and delivers it to the heat pump. Typically the length of surface ground collector pipe required for a house is between 200 and 600 metres depending on the heat demand and size of heat pump being installed.
The surface ground collector method is cost effective where sufficient useable land is available. The higher the water content of the soil the better as this facilitates good transfer of heat from the ground to the non-freezing solution circulating inside the horizontal ground collector.