Steady-State Thermodynamic Analysis for Compressed Air Energy Storage in Salt Caverns

Under the global transition toward low-carbon energy systems, compressed air energy storage in salt caverns has emerged as a critical large-scale energy storage solution, though its thermodynamic modeling still faces two fundamental challenges: (1) inadequate characterization of the coupled effects between salt rock creep and microleakage; and (2) parameter sensitivity analysis for multiphase dynamic processes remains incomplete. This study presents a breakthrough by establishing a steady-state explicit mathematical model based on energy conservation principles, which for the first time, to the best of our knowledge, enables synchronous coupling calculations of creep rate and leakage volume. The Python-based numerical analysis platform developed for this research reveals three dominant control factors for temperature variation during the injection phase in the given storage system: formation temperature gradient, surrounding rock heat transfer coefficient, and air injection rate. Temperature changes during the second storage phase are shown to depend on the pressure stabilization state following the production phase, requiring case-specific analysis. Notably, the first storage phase and production phase consistently exhibit stable entropy reduction trends across all tested operating conditions. Pressure evolution in the first three phases demonstrates characteristic patterns of rapid rise, slow decline, and rapid decline, respectively, while the fourth phase is governed by dual regulation of mass and temperature. Compared with conventional methods, this model incorporates more comprehensive salt cavern characteristics, providing a novel theoretical framework for real-time parameter optimization in compressed air energy storage plants.