Geothermal energy is derived from the thermal energy generated and stored in the Earth’s interior. In the case of shallow geothermal, the resource for energy is solar heat stored in the earth. This geothermal resource is renewable, as there is a constant heat flow to the surface and atmosphere from the solar radiation.
Near-to-surface geothermal technologies takes advantage of this renewable source for space and water heating by transferring at low temperature the geothermal heat to a pumped fluid through the ground. In warmer climates, this source can also be used in combination with reverse heat pumps as a sink for the heat extracted from the building, reducing the cooling load.