Thermo-Hydraulic Leaky-Tank Model for Inventory Analysis of Hydrogen Storage, Loading, and Unloading in Subsurface Salt Caverns

Abstract The formulation of the hydrogen thermodynamics and behavior are incorporated into the mass, momentum, and energy conservation equations to determine the conditions of the hydrogen reserves in the subsurface storage salt caverns coupled with the inflow and outflow through the loading/unloading wells. The hydrogen storage salt cavern is treated like a leaky tank having permeable and conductive walls allowing heat transfer and gas leakage through the interlayer formations, and the cracks and fractures created by thermal and stress variation during hydrogen loading/unloading processes. The numerical solution of the set of differential equations forming the dynamic thermo-hydraulic mathematical model subject to prescribed initial and boundary conditions is facilitated to determine the temperature, pressure, flow, and accumulation/depletion conditions as functions of time during loading, storage, and unloading. This allows an effective inventory analysis of the hydrogen storage in subsurface salt caverns. This paper provides the relevant thermodynamics relationships and the important theoretical background and mathematical formulations required for development of large-scale simulators which can be applied for effective designing, optimizing, controlling, management, and inventory analysis of the hydrogen gas storage processes in large subsurface salt caverns, practical view and concept of the salt cavern storage of the hydrogen gas as a leaky tank, description of the hydrogen gas behavior and storage processes in subsurface salt caverns at different levels of sophistication, rigorous mathematical formulations of the theoretical relationships of the governing processes at the subsurface salt cavern storage pressure and temperature conditions, and the demonstration of an application and numerical solution by a simplified salt cavern macroscopic model.