Performance analysis and optimization of an adiabatic compressed air energy storage system coupled with the packed-bed thermal energy storage device

In the adiabatic compressed air energy storage (A-CAES) system incorporating the packed-bed thermal energy storage device with encapsulated phase change material (PBTES), the thermocline characteristics of the PBTES device has significant impacts on the overall performance of the A-CAES system. In this work, an A-CAES system and its dynamic model are established taking the thermocline characteristics of the PBTES device into account. Next, the dynamic performance of the A-CAES system with a non-cascaded PBTES device is analyzed and compared to the system with a double-tank thermal energy storage (DTTES) device, elucidating the impacts of the PBTES device on the A-CAES system performance. Finally, in order to enhance the comprehensive performance of the A-CAES system, a two-cascaded PBTES device is introduced, and the melting temperature of the phase change material (PCM) is optimized to achieve the optimal A-CAES system round-trip efficiency. The results indicate that by implementing the two-cascaded PBTES device and optimizing the PCM melting temperature, the heat storage density of the device is increased by about 110.2 % compared with the DTTES device, and the round-trip efficiency of the A-CAES system is increased by 4.4 percentage points compared to the unoptimized system, achieving both high energy utilization efficiency and compactness.