Performance Analysis and Optimization of a Pumped Hydro-Compressed Air Energy Storage System Based on a Combined Water-Storage-Gas-Storage Cycle

With the accelerating energy transition, efficient energy storage is essential for higher renewable energy consumption. Based on a combined water-gas storage cycle, pumped hydro-compressed air energy storage (PH-CAES) shows great promise in energy storage due to its large capacity and flexible siting. However, as parameter impacts on system operation are unclear, efficient system design is challenging. This paper thus proposes a method for the performance analysis and optimization of a PH-CAES system. Firstly, this paper outlines the system's structure and operation modes and then establishes a thermodynamic model for rated operation. Secondly, this paper conducts a thermodynamic simulation of the system's operating characteristics and sensitivity analyses of three key parameters (storage pressure, compressor isentropic efficiency, etc.) regarding two evaluation indices (electrical-electrical conversion efficiency and storage density). Finally, a comprehensive energyefficiency analysis identifies the optimal combination of operating parameters for maximizing system energy efficiency. The results indicate that optimizing compressor and turbine isentropic efficiencies maximizes system energy efficiency, which offers a reference for future PH-CAES system development.