Thermodynamic analysis of an advanced adiabatic compressed air energy storage system integrated with a high-temperature thermal energy storage and an Organic Rankine Cycle

Abstract

Advanced adiabatic compressed air energy storage (AA-CAES) system has drawn great attention owing to its large-scale energy storage capacity, long lifespan, and environmental friendliness. However, the performance of the air turbine during the discharging process is limited by the low temperature of the compression heat. Thus, this study proposes an integrated AA-CAES system incorporating high-temperature thermal energy storage and an Organic Rankine Cycle (ORC). The high-temperature thermal energy storage is introduced to heat the discharging compressed air to enhance the air turbine performance, and the Organic Rankine Cycle is integrated to utilize the waste heat. Notably, two preheaters are deployed in a special tandem to recover the heat from the air exiting the turbine and the water exiting the hot water tank, respectively. This paper develops a thermodynamic model to simulate the proposed system, assessing the effects of heat storage temperature, ambient temperature, and inlet conditions of the air turbine on performance metrics, including exergy efficiency and exergy destruction. The simulation results indicate that, compared to thermal oil and Hitec salt, employing solar salt as the heat storage medium for the solar thermal collection and storage unit yields the best performance. The energy storage efficiency, roundtrip efficiency, exergy efficiency, exergy conversion coefficient, and energy storage density of this system are 115.6 %, 65.7 %, 78 %, 79.4 %, and 5.51 kWh/m3, respectively. Exergy analysis reveals that the exergy efficiency of interheaters (IH) is the lowest at 76.7 %, while air turbines (ATBs) exhibit the highest exergy efficiency at 91.2 %. Moreover, due to the irreversible processes of compression, expansion, and throttling, ATBS, compressors, and throttle valves collectively contribute to an exergy destruction rate as high as 79.2 %. The parameter analysis demonstrates that low ambient temperature, high inlet temperature, and high inlet pressure of the air turbine enhance energy storage performance.