The success of the energy transition from fossil fuels to renewable energies depends significantly on storage capacities for electric energy. The decommissioning of coal-fired power plants in Germany over the next ten years will lead to a supply deficit of approx. 35 GW at night without wind power. On sunny days, however, a surplus of photovoltaic electricity of over 100 GW is expected in the near future. At some days currently (1. May 2026) already exist a surplus of 40 GW with strong negative prices at the exchange. The traditional technology for storing large amounts of electricity is pumped storage. This robust technology has a service life of approximately 100 years, compared to batteries with approximately 20 years. However, there are very few sites for new pumped storage power plants available and approved in Germany. Therefore, alternative locations must be found.
This article describes new approaches that proposes using existing, old open-cast lignite mines as sites for new pumped storage power plants in two different areas in Germany with different geological conditions. In the Renish mining district – a region between Cologne, Erkelenz, and Aachen – three large open-cast lignite mines are currently in operation, but these will be decommissioned in the coming years. The open-cast lignite mines reach depths of between 200 and 400 meters, thus offering ideal conditions for pumped-storage power plants. The Hambach mine, in particular, with its 400-meter depth, is exceptionally well-suited for such an unconventional pumped-storage power plant.
The locations Hambach, Garzweiler and Inden provide the advantage that a high voltage grid system (generating station Neurath and Weisweiler) already exists. Pumped-storage hydro-electric systems are well suited to this current power grid better than batteries. Consequently, pumped-storage systems would also reduce the costs associated with grid expansion, as they can be seamlessly integrated into the prevailing energy distribution system.
In the Lausitzer Revier exist coal mines with lower depth (approx. 100 m) but they got a vertical an deep sealing against groundwater inflow so that the can operate with low water levels independent from the environment.
A key feature of the here presented hydro power plant in the Rhenish revier is the separation of the water volume between the upper and lower storage basins from the residual water in the retention basins. The lower storage basin can be constructed in large, reinforced tube concrete caverns with a diameter of over 20 meters. The upper storage basin is located near the former ground level. The Hambach site allows for the installation of a capacity exceeding 6 GW and a storage capacity of more than 50 GWh, which would surpass the maximum output of the largest pumped-storage power plant in Germany by at least five times. This Hambach pumped-storage power plant could cover a large portion of Germany’s total storage demand during the day-night cycle.
Furthermore such a huge storage capacity would improve the profitability of the green hydrogen production in Germany, since the electrolysis stations can obtain also during night time the needed electric power from these hydro power plants. Electrolysis stations must not switched –off after sun set and must not be heated up next morning. Thus electrolysis operation time increases from about 1400 hours per year up to 5000 hours.
Citation: Risse, H. et al., (2026). Innovative Approaches of Pumped Hydro in Mining Areas as Key Technology in solving the Energy Storage Problem in the Energy Transition. .Adv Earth & Env Sci; 7(2):1-7.
DOI : https://doi.org/10.47485/2766-2624.1093