Groundwater of a former underground slate exploitation in Martelange-Rombach (Luxembourg) and its renewable energy potential 

The role of geothermal energy in the energy transition is rapidly gaining recognition. Its storage technologies provide flexible solutions to address the intermittent nature of other renewable resources. Abandoned mines and other underground caverns have recently attracted particular attention as valuable geothermal reservoirs.In this context, a pilot project was recently initiated in the flooded abandoned underground slate exploitation area of Martelange (Belgium & Luxembourg). This area, with its long industrial history, represents a significant opportunity for future geothermal applications. The large volume of water stored within these underground caverns, in combination with heat-pumps, is sufficient to provide heating and cooling for a quite large number of buildings.Where natural regeneration, depending on groundwater flows and the thermal conductivity of the surrounding soil, proves insufficient and where water temperature changes exceed 5 °C, active regeneration may be implemented. This involves the installation of (un)glazed solar thermal absorbers to collect low-cost solar heat during summer and cold during winter, transforming the system into a form of solar district heating. In such a scenario, the flooded slate caverns would function as a seasonal energy storage body.The objective of the project is to develop a modern, highly energy-efficient urbanized area with a commercial zone, based on a low-temperature urban heat and cold network fed by heat-pumps. Achieving this requires a detailed assessment of the local geological and hydrogeological conditions, especially the structure and connections of the slate caverns, to ensure optimal and sustainable use of the available water resources. The first results from this study will be presented.