GeoSolar is an innovative 4-year research project that transforms end-of-life and abandoned coal mines into large-scale thermal energy storage systems. By combining mine water geothermal and solar thermal energy, the project demonstrates how former mining regions can play an important role in Europe’s clean energy transition.
Across Europe, many coal mines are approaching closure and hold millions of cubic meters of naturally warmed mine water at depths where temperatures reach 20-30°C. Although this heat is not hot enough for direct use in district heating, mine sites are often next to cities with high seasonal heat demand, making them ideal for sustainable repurposing.
GeoSolar addresses this opportunity by creating a system where solar energy heats mine water in summer to 70-90°C, which is then injected into deeper mine workings for long-term storage. In winter, the stored heat is recovered at temperatures suitable for high-temperature district heating networks, reducing dependence on fossil fuels. This approach supports the transition of coal regions, giving new life and purpose to former industrial landscapes while reducing environmental impacts.
Why does GeoSolar matter?
The project aims to give new life to coal mines approaching closure by transforming them into sustainable, long-term energy resources.