In the lower subsoil of the so-called “near-surface geothermal layer” lies a heat source that can be utilized all year long, which has an almost constant temperature. It can be used for every possible building type, large or small, public or private. Depending on the region it is also referred to as, “vertical absorption, ground spit or ground lance”. It requires little space and the ground probe can be drilled on the smallest of plots. Therefore it is ideal for refurbishment or adaptation from a heating system fuelled by fossil fuels to the use of geothermal energy.

As with a surface collector a mixture of water-glycol circulates in a closed circuit (similar to the cooling system of a car). Depending on the necessary size of the heat pump unit a specialized company ascertains the depth and amount of bore holes in which the u-shaped plastic tubing is installed and pressed, in order to achieve good heat transfer.