Mark 51°7 is a 70-hectare area located in the city of Bochum in Germany. It has undergone several transformations over the years: it was originally the Dannenbaum coal mine, then the Opel company produced a car factory there from 1963 to 2000. Today, it is home to an innovative energy concept throughout the area: the fifth-generation district heating and cooling grid co-created by FUW GmbH and Stadtwerke Bochum Holding GmbH. 

Coal mines, which are usually a source of fossil fuels, can now be used as a geothermal energy source.To provide heat, the mine water, which has a temperature of around 30°C, is extracted from the boreholes and heated to about 45°C using heat pumps.

For cooling, the grid uses the shallowest borehole and pumps water from the mine, which is around 18°C.

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