Conventional and advanced exergy analysis of a novel transcritical compressed carbon dioxide energy storage system

The work presents a comprehensive investigation on a novel two-stage transcritical compressed carbon dioxide energy storage system using conventional and advanced exergy analyses. Conventional exergy analysis quantifies the exergy destruction of each component in an independent manner, and identifies cold storage as the most significant component for improvement due to the largest exergy destruction rate of 256.71 kW, sharing 19.23% of the total exergy destruction rate. The advanced exergy analysis can reveal more valuable information by taking the interconnections among system components and technological limitations of each component into consideration. The results indicate that the interactions among components are complex but not very significant, and the first compressor possesses the highest potential for improvement due to the largest avoidable exergy destruction rate of 159.01 kW that accounts for 22.55% of total avoidable exergy destruction and 11.91% of total exergy destruction. A comparison between the results of above two analysis approaches confirms that the conventional exergy analysis could mislead the designer and the results based on the advanced approach are more pragmatic. Besides, the system exergy efficiency is 59% for real cycle and the theoretical maximum for unavoidable cycle is 77.8%, meaning great potential for the improvement of system performance.