On 6 October 2026, at a geothermal energy conference in North Rhine-Westphalia held in Bochum, Fraunhofer IEG and the Post-Mining Research Center of Georg Agricola University of Applied Sciences (FZN/THGA) signed a memorandum of understanding. The partners are launching a joint project to systematically explore how mine water geothermal energy can serve Germany’s former coal regions. The ambition goes beyond a single pilot: the goal is to produce standards and guidelines ready for broad-scale deployment.
Key points:
- The MoU was signed on 6 October 2026 in Bochum, Germany.
- Partners: Fraunhofer IEG and the Georg Agricola Post-Mining Research Center (FZN/THGA).
- In 2022, two research boreholes were already drilled at the MARK 51°7 site in Bochum into a flooded coal mine.
- Large mine water district heating networks are already operating in the United Kingdom and the Netherlands.
What Fraunhofer IEG and THGA agreed to research
According to thinkgeoenergy.com, the partnership is centred on repurposing coal-era infrastructure for the energy transition. Within this framework, flooded mines become either a source of heating and cooling or a seasonal energy storage system. The parties agreed to work across technical, environmental, legal, and economic dimensions of implementation — not just the engineering.
The expected output is a set of practical standards and guidelines that municipalities, energy suppliers, and other stakeholders in post-mining regions can apply to connect existing underground infrastructure with modern heat supply needs. The project also has an educational dimension: young professionals will be engaged through diploma theses, internships, and field placements.
“The collaboration combines the strengths of both partners: the university brings deep expertise in education and research on mining, post-mining, and geo-resources, while Fraunhofer IEG specialises in taking new technologies through to deployment together with industry and the public sector,” says Florian Hahn, head of Fraunhofer IEG’s Competence Center for Post-Mining Land Use.
How mine water works as a heat carrier
The principle is straightforward: water that floods shafts and tunnels after a mine closes maintains a relatively stable temperature year-round. It is pumped through heat exchangers, and heat pumps extract low-grade thermal energy into district heating networks. In summer the process can be reversed — excess heat is returned to the mine, effectively turning it into a seasonal thermal reservoir. For former coal towns, this means that the boreholes, shafts, and collectors built over previous decades need not become stranded assets.
Germany already has a testbed. In 2022, two boreholes were drilled at the MARK 51°7 site in Bochum, providing direct access to water in abandoned coal mines. From this base, the project plans to extend its geographic scope across the entire Ruhr Basin and other former coal districts.
The benchmark: the United Kingdom and the Netherlands
The project authors explicitly point to international precedents: large mine water district heating networks are already operational in the United Kingdom and the Netherlands, delivering naturally warmed water from abandoned mines into heat grids at scale. For Fraunhofer IEG and THGA, this is evidence that the technology has moved beyond the pilot stage and now requires a proper regulatory framework — standardised solutions, monitoring requirements, and rules for integration into local energy systems.
“Former mining infrastructures can make a significant contribution to the energy transition. Mine water in particular allows us to rethink existing structures and develop them for future-oriented heat supply,” says Frank Sachse, head of Innovation and Transfer at Fraunhofer IEG.
Why this case matters for post-mining regions
Mine water geothermal energy addresses two challenges simultaneously: it delivers local, low-carbon heat and restores economic relevance to territories whose core industry has left. Ukraine has its own legacy of coal mining, with many mines already taken out of operation. When planning for the recovery of those regions gets underway, the set of German guidelines being developed here is worth treating as a ready methodological framework — covering everything from assessing the mine water resource to fitting it within tariff and environmental regulation.
For broader industry context, see our articles on geothermal energy challenges and opportunities and government support for geothermal projects in the United States.
Sources: thinkgeoenergy.com
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