Parametric assessment and multi-objective optimization of an ejector-enhanced compressed air energy storage system based on conventional and advanced exergy

Compressed air energy storage systems offer an effective solution to the intermittency and fluctuation challenges associated with renewable energy grid integration. A significant challenge in current compressed air energy storage systems is the substantial energy loss incurred during the discharge due to throttling processes, which is crucial for improving round-trip efficiency. Therefore, an ejector-enhanced compressed air energy storage system (EA-CAES system) is proposed in this study, characterized by the employment of ejector to reduce the pressure loss caused by the throttling process. The performance of the system is analyzed from both sensitivity analysis and multi-objective optimization. Conventional exergy analysis is used to estimate the locations and magnitudes of exergy destruction within the system, and advanced exergy analysis is applied to determine the interactions among components and to identify the potential for system performance improvement. The results showed that, compared to the advanced adiabatic compressed air energy storage system, the round-trip efficiency of the proposed system increased by 3.07%, and the total exergy destruction during the pressure reduction process was reduced by 401.9 kW. As for the sensitivity for components in the EA-CAES system, the avoidable exergy destruction of the ejector is the most sensitive to changes in all parameters, followed by the unavoidable exergy destruction of the heat exchangers in the charging and discharging processes influenced by the air storage pressure and throttling pressure, respectively. Finally, based on the best trade-off solution among multi-objective optimization, the ejector, turbine, and compressor should be paid special attention to the system improvement according to the advanced exergy analysis.