Subsurface renewable energy storage capacity for hydrogen, methane and compressed air – A performance assessment study from the North German Basin

The transition to renewable energy sources to mitigate climate change will require large-scale energy storage to dampen the fluctuating availability of renewable sources and to ensure a stable energy supply. Energy storage in the geological subsurface can provide capacity and support the cycle times required. This study investigates hydrogen storage, methane storage and compressed air energy storage in subsurface porous formations and quantifies potential storage capacities as well as storage rates on a site-specific basis. For part of the North German Basin, used as the study area, potential storage sites are identified, employing a newly developed structural geological model. Energy storage capacities estimated from a volume-based approach are 6510 TWh and 24,544 TWh for hydrogen and methane, respectively. For a consistent comparison of storage capacities including compressed air energy storage, the stored exergy is calculated as 6735 TWh, 25,795 TWh and 358 TWh for hydrogen, methane and compressed air energy storage, respectively. Evaluation of storage deliverability indicates that high deliverability rates are found mainly in two of the three storage formations considered. Even accounting for the uncertainty in geological parameters, the storage potential for the three considered storage technologies is significantly larger than the predicted demand, and suitable storage rates are achievable in all storage formations.