A thermodynamic model and experimental validation of internal heat exchangers for active air temperature control in lined rock cavern for compressed air energy storage

Compressed air energy storage (CAES) is a promising large-scale energy storage technology for integrating intermittent renewable sources. However, air temperature fluctuations in a lined rock cavern (LRC) affect system efficiency and energy storage density. This study introduces an active thermal and pressure management strategy using internal heat exchangers and waste heat. A new thermodynamic model was developed to simulate the dynamic responses of air temperature and pressure, and experiments were performed to validate both the effectiveness of internal heat exchangers in controlling air temperature and the accuracy of the proposed model. Experiments and simulations show that the internal heat exchanger can reduce air temperature fluctuations by over 50 %. Experimental results reveal that thermal stratification of air is intensified vertically after activating the internal heat exchanger, but horizontal uniformity is maintained even with a heat exchanger length equivalent to only one-third of the total tank length. By implementing the internal heat exchanger, the energy storage density and gas storage capacity can increase by 11.8 % and 12.5 %, and the discharge duration is extended by 81.9 min. This study contributes to the optimization and future development of efficient and economical CAES systems.