Design and Thermodynamic Investigation of a Waste Heat‐Assisted Compressed Air Energy Storage System Integrating Thermal Energy Storage and Organic Rankine Cycle

Compressed air energy storage (CAES) technology has attracted growing attention because of the demand for load shifting and electricity cost reduction in energy‐intensive industries. To increase the round‐trip efficiency and energy storage density and simplify the structure of advanced adiabatic CAES (AA‐CAES) systems, a waste heat‐assisted CAES (WH‐CAES) design integrating a tube‐in‐tube thermal energy storage unit and an organic Rankine cycle (ORC) is described herein. Thermodynamic models of the proposed WH‐CAES system are established, and the effects of waste heat temperature, ratio of compression ratios, ratio of expansion ratios, and air storage cavern pressure on the performance of different systems, including AA‐CAES and WH‐CAES with and without ORC, are investigated. The results show that when the waste heat temperature is 500 °C, the input work of the compressors reaches its minimum value at a ratio of compression ratios of 1.14, and the optimal ratio of expansion ratios is 0.39. Under these optimal operating conditions, compared with the AA‐CAES system, the round‐trip storage efficiency, energy storage density, and system energy efficiency of the WH‐CAES system can be increased significantly. The findings validate the potential of the proposed WH‐CAES system.