Study on the thermodynamic response of salt cavern hydrogen storage under long-term thermo-mechanical coupling

Due to its favorable physical properties, salt rock is considered an ideal medium for large-scale, long-duration hydrogen storage, making salt cavern hydrogen storage (SCHS) a key direction in geological storage. However, the distinct thermodynamic properties of hydrogen, including low density, high specific heat capacity, and low critical pressure and temperature, combined with frequency cycling demands, may pose risks such as pronounced temperature fluctuations, cold-induced tensile fracturing, and creep-accelerated volume shrinkage. To explore the differences between hydrogen and natural gas storage, a long-term thermo-mechanical coupling model was developed and applied to a real salt cavern in Jintan, China. The analysis compares temperature and pressure changes within the cavern and their effects on surrounding rock stress. Results show that: (1) Under identical cycling conditions, natural gas exhibits stronger thermal effects. Hydrogen appears to pose even lower risks. (2) Increasing hydrogen injection temperature raises cavern temperature and pressure, but remains within a controllable range. (3) The heat transfer coefficient in the range of 0–10 W/m2·K significantly affects the surrounding rock. (4) As the annual injection-withdrawal frequency increases from 1 to 10 times, cavern temperature and pressure fluctuations rise markedly from 24.33 K to 10.628 MPa to 80.80 K and 12.42 MPa, leading to significant changes in stress state and volume shrinkage of the surrounding rock. It is necessary to reasonably adjust the operating pressure design to ensure the stability of salt caverns. These findings provide theoretical support for optimizing the safe operation and design of SCHS systems and advancing large-scale hydrogen storage technology.