We contribute to a drastic reduction in the greenhouse gas carbon dioxide by exploiting groundwater for heating and cooling. The groundwater is removed warm in winter and the energy thus gained is used to heat the rooms; in summer the rooms are cooled using this environmentally-friendly method with cold groundwater. The room conditions are always comfortable – without the otherwise customary exploitation of energy.

State-of-the-art technology is used to save energy at the Clarion Hotel Hirschen in Freiburg. At the heart of the whole project is the large heat pump with which 3°C of heat is obtained from 6 - 8 litres of groundwater. Thus approx. 86 kW of heat is produced from the 17 kW of electricity that the heat pump consumes, and is thus available for hot water, heating and air conditioning.
 
In such plants, it is important that the heat exchanger is as large as possible so that a lower inlet temperature of about 50 - 52°C can be used. This increases the efficiency of the heat pump. Large air/air heat exchangers are also important in order to regain about 70% of the energy from the exit air, because preventing energy consumption is the best way to save energy.