The mine water from the former coal mine, which is at around 27 to 28 degrees Celsius, will be heated to around 48 degrees Celsius using heat pumps before being distributed to the district heating network. This will be enough to supply 70% to 75% of the heating and cooling requirements of the companies and research institutions around the site.
The pump tests were done by Fraunhofer IEG with FUW GmbH, a subsidiary of Stadtwerke Bochum. Submersible centrifugal pumps were lowered along the borehole to a depth of around 300 meters. Data on the temperature, pressure, pumped volume, and composition of the mine water were collected for the next 17 days. Seismic monitoring was also done.
At 27 to 28 degrees Celsius, the temperature of the mine water was slightly below the expected 30 degrees Celsius. This does not hamper the project, but a reconfiguration of the system may be necessary.
Rolf Bracke, Head of the Fraunhofer IEG, said that drilling on a former hard coal mine was a special challenge. “The subsoil here sometimes resembles Swiss cheese.” The successful pump test is the first time that a geothermal resource in the North-Rhine Westphalia region has been proven as being able to contribute to the energy needs of the cities of Rhine and Ruhr.
