In Central Europe the ground temperature at a depth of 10-20 metres averages around 11-12 °C. In the soil layers above this, the temperature will depend on weather conditions. Every square metre of ground surface is irradiated by approximately 1100 kW of solar energy on an annual basis. In the lower layers of the ground, geothermal influences predominate, causing the temperature of the ground mass to increase by around 1 °C for every 33m of depth. The basic idea is to extract the thermal energy from the ground via the foundations (near-surface geothermal energy) and to provide the appropriate systems which allow that energy to be utilized in buildings. Conversely, this principle can also be used for cooling by dissipating excess heat into the ground. Providing that the ground conditions permit, this means that cooling and heating energy can be stored on a seasonal basis. There are various methods for tapping the energy stored in the ground. The most widely known systems are vertical bore hole heat exchangers, horizontally laid earth collectors, trenched collectors and absorber systems integrated into strip footings and ground slabs. In the case of horizontal ground loops, the availability of land as a heat source is relatively limited and vertical ground loops involve considerable additional costs for drilling the holes in the ground and installing the loop. NÄGELE GmbH began installing absorber systems in steel-reinforced concrete piles and diaphragm walls over 20 years ago and has developed the technology to its present state of the art.