Numerical Simulation on the Evaluation of Charging–Storage–Discharging Thermodynamic Process and Long-Term Operation Performance of Compressed Air Energy Storage Rock Cavern

Periodic charging–storage–discharging induces cyclic variations in temperature and pressure inside the rock cavern, forming a complex thermo-hydro-mechanical (THM) coupling problem that impacts the structural stability and energy storage efficiency of the cavern. In this study, a thermodynamic model of CAES rock caverns incorporating heat exchange and air leakage was established, enabling accurate characterization of temperature and pressure variations in the cavern during charging–storage–discharging. Based on this, the influences of heat transfer coefficient and charging temperature on the thermodynamic process were discussed. The primary reason for the pressure and heat losses during the high-pressure storage stage was analyzed. Finally, a long-term performance simulation of a CAES cavern over a 365-day operation period was conducted. Results indicated that: (1) Temperature, pressure, and air leakage rate all presented a trend of “up-down-down-up”, synchronized with the four operation stages of charging, high-pressure storage, discharging, and low-pressure storage; (2) during high-pressure storage, continuous heat exchange between compressed air and the cavern wall causes a reduction in pressure and temperature. The magnitude of this reduction decreases with increasing heat transfer coefficient but increases with rising charging temperature; (3) after 365 days of operation, the air leakage rate decreased from 10−2 magnitude to 10−3, with increased pore pressure in the surrounding rock reducing the pressure gradient, thereby impeding air leakage from the cavern under the assumption of constant permeability.