Airtightness evaluation of lined rock caverns for compressed hydrogen energy storage: a modified numerical solution incorporated with hydrogen permeation in steel

Compressed hydrogen storage (CHES) is a large-scale renewable energy storage technology that primarily using salt caverns but faces geographical limitations. Hard rock caverns present a potential alternative to storage hydrogen whose airtightness is vital to the economy and efficiency of CHES systems. This paper established a thermal-mechanical-permeable coupled model to assess hydrogen leakage of CHES steel-lined caverns, proposing an accurate numerical leakage solution considering various driving forces for permeation. To reduce calculation, a simplified formula for hydrogen permeation is proposed to modify the numerical model by incorporating leakage impacts on stored hydrogen. Findings reveal that the daily hydrogen leakage rate of a 4130X steel-lined cavern under 4.08–7.08 MPa is 8.83 × 10−4 %, with the concentration gradient contributing 95 % of the leakage, meeting the sealing requirement. With leakage's impact on thermodynamic responses considered, a smaller leakage rate (8.43 × 10−4 %) is obtained. Key parameters influencing leakage include the hydrogen permeability of the steel lining, hydrogen charging duration, cavern radius (negatively correlated), burial depth, mass flow rate of charging, and steel lining thickness (negatively correlated). Optimizing these factors can mitigate cavern leakage. This study constructs the airtightness evaluation framework of CHES and expands CHES technology's applicability by repurposing abandoned spaces, advancing global decarbonization and energy transition.