Underground hydrogen storage in salt caverns in the Netherlands - Storage performance and implications for geomechanical stability

Hydrogen is expected to become an important cross-sectoral energy carrier, providing flexibility through large-scale storage and on-demand production of hydrogen via electrolysis as the proportion of energy produced from intermittent renewable energy sources increases (i.e. wind and solar). van Gessel et al. (2018, 2021) evaluated various scenarios to estimate the need and potential for deploying hydrogen storage capacities in subsurface formations. While there is a need to balance at seasonal timescales, new analyses reveal that optimizing flexibility in the energy system may significantly alter the way storages are used throughout the year. Rather than a single-cycle (seasonal) profile, bi-weekly and monthly cycles, with higher injection and withdrawal rates, may increase the effective utilization of the storages while reducing the capacity needed. Additional long-term (seasonal) storage capacities may be required for strategic reserve or arbitrage purposes. Salt caverns have proven potential for pure hydrogen storage with favourable operational conditions. The estimated maximum practical storage that may be required in the Netherland by 2050 is ca. similar to 15 TWh, consisting of 60 caverns with a geometrical volume of 1 million m(3) each. This necessitates development of several clusters consisting of multiple salt caverns. Higher storage capacity demands may require additional storage volumes potentially in depleted natural gas fields. Large-scale implementation of cavern storage poses a geomechanical challenge, due to long-term subsidence effects. Additionally, better understanding is needed regarding integrity issues in the near-wellbore area during fast cyclic loading and unloading.