Geothermal energy: Shallow sources

Abstract

Below a depth of around 5 to 8 metres below the surface, the ground displays a temperature which is effectively constant and a degree or two above the weighted mean annual air temperature at that particular location. In Melbourne, the ground temperature at this depth is around 18°C with temperatures at shallower depths varying according the season. Further north, these constant temperatures increase a little; while for more southern latitudes, the temperatures are a few degrees cooler. Shallow source geothermal energy (also referred to as direct geothermal energy, ground energy using ground source heat pumps and geoexchange) uses the ground and its temperatures to depths of a few tens of met..