From Reservoir to District Heating: Success Factors and Challenges of Medium‑Depth Geothermal Energy in North German Municipalities

This contribution presents results from case studies on medium-depth hydrothermal geothermal projects in the North German Basin (NGB). Despite well-explored locations, these projects have not yet progressed to implementation. All cases were selected based on favourable geohydraulic conditions, and their geology is representative of that of the NGB. The selected sites differ intentionally in terms of their heat-offtake situations, such as the heating network, the size of the municipality, or the presence or absence of commercial heat consumers.For each case study, technical concepts were developed that integrate geothermal heat for partial or full baseload coverage. A central element of all concepts is the use of one or more high capacity heat pumps to raise the production temperature to the required supply temperature of the district heating network. One of the key aspects of this work is to evaluate the operational feasibility of the proposed technical concepts. To this end, the authors performed thermal-hydraulic coupled simulations of the hydrothermal system. These simulations provide insights into long‑term reservoir behaviour under different production and injection scenarios. They form the basis for an energy balance while maintaining reservoir integrity.The results of the case studies will be generalised. Recommendations will be made to help the stakeholders of the heat transition to integrate medium-depth geothermal energy into the heat supply in a technically robust and economically viable way.The presented work is part of the research project Warm‑Up, funded by the Federal Ministry for Economic Affairs and Energy (BMWE) and conducted at the Federal Institute for Geosciences and Natural Resources (BGR). Project partners include the Leibniz Institute for Applied Geophysics (LIAG), the ECOLOG Institute for Social‑Ecological Research and Education and the Institute for Ecological Economy Research (IÖW).