Seasonal Hydrogen Storage in Salt Caverns: Numerical Modelling of Cyclic Operation and Long-term Integrity
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Seasonal energy storage supports renewable balancing, and salt-cavern underground hydrogen storage can shift surplus electricity to peak demand; its long-term integrity is controlled by creep and cyclic pressurization–induced stress changes. This contribution presents a numerical framework to quantify how pore-fluid effects modify the long-term mechanical response of hydrogen salt caverns under realistic operating regimes. We develop an axisymmetric finite-element model that couples viscoplastic salt creep with pore-pressure diffusion through Darcy flow (poro-viscoplastic coupling), enabling direct comparison against a conventional viscoplastic-only formulation. Simulations examine two representative operational strategies—long seasonal cycles and shorter, more frequent cycling—capturing depth-driven lithostatic loading and geothermal-gradient-controlled creep behavior. Results show that pore-pressure diffusion alters effective stress paths and relaxation in the surrounding salt. Coupling generally smooths deformation and reduces peak strains, but deep and aggressively cycled cases can lose stability margin due to modified effective stresses and delayed redistribution. These insights help define operating envelopes for grid-driven storage and identify when viscoplastic-only models may be over-optimistic.