Heating and cooling with river water An important building block for decarbonization
The use of river water for heat pumps offers a sustainable way to decarbonize in order to generate thermal energy and heat or cool buildings. In this process, water is taken from a river or other body of water and passed through a heat exchanger. The river water transfers its heat energy to a refrigerant in the heat pump, which evaporates at a low temperature. The vaporized refrigerant is then compressed by a compressor, which further increases its temperature. The heat obtained in this way can then be used for heating purposes. In summer, the process can be reversed to cool buildings by transferring the heat from the building to the cooler river water.
Europe's largest river heat pump was put into operation in Mannheim in October 2023 with an output of 20 MW to supply around 3,500 households via a district heating network. The river water of the Rhine in Mannheim is up to 25°C warm in summer and only around 5°C in winter. This thermal energy is sufficient to heat the district heating water to between 83°C and 99°C. The technical potential of river heat pumps has not yet been exhausted. According to conservative estimates, at least 500 MW of thermal energy could be extracted from the Rhine and Neckar rivers in Mannheim alone. This could supply around 50,000 households with heat.
