Simplified Thermodynamic Analysis of Adiabatic Compressed Air Energy Storage Integrated with High-Temperature Thermal Storage

Compressed air energy storage (CAES) presents promising potential as a low-cost, long-duration, and large-scale energy storage solution. However, the lower specific work output and less flexibility are the limitations of the current state of the art. An adiabatic compressed air energy storage (ACAES) system integrated with high-temperature thermal energy storage (HTES), known as Hi-CAES, is investigated to address these challenges. This integration aims to enhance specific work output and operational flexibility. The proposed Hi-CAES system uses excess renewable energy to charge the compressor and the HTES through joule heating elements. The system achieves higher specific work output by increasing the turbine inlet temperature. A simplified thermodynamic analysis evaluates the round-trip efficiency (RTE) and specific work output of both ACAES and Hi-CAES systems. The results indicate that the RTE of the ACAES system with a 2-stage compression/expansion reaches a maximum of 80% within the cavern operating pressure range of 143-170 bar, declining thereafter. While the Hi-CAES system’s RTE is lower than the ACAES, the Hi-CAES demonstrates a specific work output 1.9 times higher than the ACAES. Furthermore, in the Hi-CAES system, the external heat supplied is converted into work with a significantly higher efficiency of up to 57%, which surpasses the efficiency of conventional heat-to-work conversion devices.