Decoupling heat-pressure potential energy of compressed air energy storage system: Using near-isothermal compressing and thermal energy storage

Compressed air energy storage (CAES) system is a promising solution for matching the intermittent renewable energy sources and stable electricity demand of end users. However, the heat loss during the compression heat utilization is the vital aspect for thermodynamic performance improvement of CAES. Therefore, a novel hybrid CAES system consists of advanced adiabatic CAES and near isothermal CAES is proposed in this study. Compared with the traditional adiabatic compression process, the conduction of near isothermal compression process could avoid the generation of compression heat significantly under the same pressure ratio. The results show that the conduction of near isothermal compression process could enhance the thermodynamic performance of the CAES system. In addition, since the thermal energy storage (TES) is the key equipment for the proposed system to achieve convergent operation condition, the mathematical model of TES was established in this paper to investigate the thermodynamic performance of the proposed system. Furthermore, the system performance could be enhanced by taking the higher values of height of TES, outlet pressure of compressor and specific heat capacity of filling material, while lower values of diameter and thermal conductivity coefficient of filling material. Through the comprehensive thermodynamic analysis, the proposed system could achieve the highest energy efficiency of 72.47 % when the storage pressure of the air storage tank equals 11 MPa.