Three-dimensional multi-physics simulation and sensitivity analysis of cyclic hydrogen storage in salt caverns

Abstract: Large-scale storage technologies are crucial to balance consumption and intermittent production of renewable energy systems. One of these technologies can be developed by converting the excess energy into compressed air or hydrogen, i.e., compressed gas, and store it in underground solution-mined salt caverns. Salt caverns are proven seals towards compressed air and hydrogen. However, several challenges including fast injection/production cycles and operating them in a system of caverns fields are yet to be resolved in order to allow for their safe scaled-up utilization for energy storage. The present study investigates time-dependent mechanical behaviors of salt caverns, individually and in multi-cavern systems. The stress conditions and model constructions are chosen to be relevant for underground energy storage purpose, and reflect the essential microscopic deformation mechanisms for reliable predictions. Built on these, the impact of model calibration and parameter estimation on cavern-scale performance are investigated. Moreover, the impact of the transient and reverse creep, cavern complex geometry, and non-salt interlayers on salt cavern performance are studied in detail. Importantly, the presented studies include quantification of the interaction of the caverns in a system of caverns. These are achieved by developing an open-source three-dimensional finite element simulator, named as "SafeInCave", which also incorporates a comprehensive salt rock constitutive model. The findings provide insights into improving the reliability of numerical simulations for safe and efficient operation of salt caverns in energy storage applications.