Today, about half of Europe’s energy is used for heating and cooling, of which only about 25% comes from renewable sources. Countries such as Germany, the Netherlands and Belgium get overall less than 30% of their energy from renewable sources. To decarbonise the energy supply, the integration of seasonal heat storage is essential. One possibility could be the use of partially flooded mines. A test storage system has been installed in a mine in Freiberg, Germany. A mobile heat pump test rig is used to store and extract heat cyclically in a storage basin (volume approx. 21 m3). Temperature sensors in the water and rock are used to evaluate the effectiveness and efficiency of the system. Emphasis is placed mostly on the heat exchanger, which eventually suffer from fouling caused by the polluted mine water. Initial tests show that storage is possible and that storage efficiencies of around 50% are achieved. In conjunction with the underground investigations, the connection of the mines to the surface heat supply is being analysed. Using GIS-supported modelling, possible sources of waste heat from industry, active cooling of buildings or solar thermal energy are systematically mapped and their possible coupling with heat storage in the mine is investigated. The example analysis of Freiberg shows that a total of 4 districts are well suited for a grid-connected heat supply including mine heat storage.