Calculation method of heat transfer in multi-layer sealing structure of artificial caverns for compressed air energy storage

Air temperature and pressure in underground caverns used for compressed air energy storage fluctuate throughout the charging and discharging cycles. These fluctuations alter the thermal field and induce structural deformation in the sealing layer, lining, and surrounding rock. Accurate prediction of stress and deformation in the sealing system during inflation and deflation is essential for reliable cavern design. Incorporating the thermal and physical properties of the materials in each layer of the sealing structure can enhance the accuracy of stress and deformation calculations for the sealing structure and also facilitate the analysis of the cavern’s energy storage capabilities. By integrating the air state analysis algorithm of the cavern with the numerical algorithm for multi-layer material heat conduction on the cavern wall, the temperature distribution across the multi-layered sealed structure can be ascertained, and the stress and strain at each point of the structure can be further determined. By accounting for the energy loss from thermal conduction through the cavern walls, and based on the concept of air exergy within the cavern, the energy recovery rate of the underground cavern during multiple inflation and deflation cycles can be quantified. Studies have shown that caverns constructed in surrounding rock with good thermal conductivity results in rapid diffusion of air heat within the caverns, leading to a more uniform temperature distribution across each sealing layer across the walls, a smaller deformation gradient of the sealing structure, and better adaptability to extreme charging and discharging conditions. However, this rapid heat diffusion can decrease energy-recovery efficiency. In low-conductivity rock, the opposite trend is expected. Therefore, engineering design should account for the differences in thermal and physical properties of sealed structures, as theses can substantially affect cavern operation.