Thermo-fluid-structural coupled analysis and safety assessment of SCO₂ storage tanks in compressed gas energy storage

This paper investigates the high-pressure gas storage module of a compressed supercritical CO₂ (S-CO₂) energy storage system by modeling a single storage tank. A three-dimensional model is established to analyze mechanical and thermal responses during the filling process using thermo–fluid–structural coupling. The filling process finishes in about 250 s for the given working condition. Severe circumferential stress concentration emerges at the head-shell junction under mechanical loads, with a maximum principal stress of 174.47 MPa. Although thermal stress distributions exhibit similar spatial characteristics, their magnitudes are much smaller, with peak values below 2.28 MPa, demonstrating that mechanical loads dominate the structural response. Further analysis shows that the head–shell transition regions govern the minimum safety factor and fatigue life, with fatigue life decreasing to approximately 23,163 cycles under high loads. These junctions are the life-limiting region and should be prioritized in detailed design, weld-quality control, inspection planning, and in-service monitoring.