Heat from soil, groundwater and sewage
At a certain depth, the ground has an almost constant temperature of 9 to 11 °C throughout the year. It can therefore be deployed with heat pumps and thermo-active component systems and can also be used as a heat source or heat sink, as is the case with the groundwater flowing through it. Similar to groundwater, wastewater from industry and commerce can also be used as a heat source.
Water is pumped through borehole heat exchangers, ground absorbers or thermally activated foundation piles for buildings, so that the ground releases or absorbs heat depending on the season. In heating operation, heat pumps supply three to five times the drive energy. In free cooling operation, these systems are significantly even more efficient because only the drive energy for the circulating pumps is required.
However, it is quite complex to implement a scheme involving a renewable heat source, low-exergy system and building operation management system, especially since seasonal effects and the regenerative capacity of the heat source have to be considered. Because of the low temperature differences between the ground and the heating or cooling system, the systems react very sensitively to faulty operation and disturbances. This reduces the current efficiency of the system, which can have a serious impact in the subsequent years. Various system concepts have been scientifically evaluated and optimised over several years.