Caverns like this one in the Salina Slănic salt mine in Romania could serve as large storage tanks for hydrogen from renewable energies.

Photo: Dan Tamas / Janos Urai

Salt caverns for storing energy from renewable sources have long been in focus. EWE, for example, wants to build a redox flow battery with an output of 120 megawatts in the caverns of a former salt dome near Oldenburg by 2023 . And RWE Gas Storage West GmbH and CMBlu Energy AG have started a joint research project aimed at converting the salt caverns previously used for gas storage into large, organic river batteries . Underground salt caverns are also seen as a promising storage option for storing hydrogen as an energy source. A team from RWTH Aachen University, Forschungszentrum Jülich and Fraunhofer IEG rolled out how large their storage potential is in EuropeStudy in the specialist magazine "International Journal of Hydrogen Energy" illuminated.

The interdisciplinary team estimates the total energy storage potential in the form of hydrogen in salt caverns on land and at sea to be 84.8 petawatt hours, with 23.2 petawatt hours on land and 61.6 petawatt hours at sea. According to the analysis, Germany has a total of 35.7 petawatt hours, of which 9.4 petawatt hours are on land - the largest national potential on land in Europe. For comparison: the potential for pumped water storage power plants in Europe is around 0.123 petawatt hours.

"Salt caverns are the most promising option for large storage facilities due to the low investment costs, good sealing and low shielding gas requirement," says Peter Kukla, Head of the Georesources Department at Fraunhofer IEG and Professor of Geology at RWTH Aachen University. In order to estimate the economic potential of the salt storage, a more detailed energy system analysis is necessary. This could correlate economic and ecological aspects, energy profiles as well as locations with high energy demand, high energy supply and high storage capacity.