Large-scale storage capacities as the backbone of a renewable energy system

Thermal energy storage is one of the key challenges of the energy transition, since a large portion of the final energy consumption is used for heating purposes and industrial processes and heat is subject to large seasonal fluctuations in supply and demand. To overcome this seasonal mismatch, geothermal storage offers a large, mostly unexploited potential with capacities that are unequalled by other technologies. The technology of high-temperature thermal storage in aquifers has a crucial role to play, since it could serve the need for large storage capacities. We highlight two aquifer types to which we attach a high importance as future technology.