Analytical methods for thermo-mechanical coupling of artificial caverns of the compressed air energy storage

The air temperature, pressure, as well as the temperature, stress, and strain of the sealing layer, concrete liner, and surrounding rock in the compressed air energy storage artificial cavern undergo variations during the inflation and extraction cycles. Jointly solving these variables is a key technique in engineering design and a difficulty in theoretical analysis. This article proposes a coupling calculation method between the thermodynamic of air inside the artificial cavern and the thermal conduction of the cavern wall, based on the one-dimensional basic solution of heat conduction and the basic solution of air temperature in the artificial cavern. The validity of the methodology was confirmed through a rigorous comparison with numerical simulation outcomes. An illustrative case study of a steel-sealed cavern was conducted. The findings reveal that the process of inflating and extracting air within the cavern leads to a substantial variation in air temperature, with the amplitude of pressure fluctuations exceeding those predicted under the assumption of constant temperature. The depth of the tunnel wall is minimally affected by periodic temperature fluctuations. Once the thickness of the concrete lining surpasses the influence range of periodic temperature fluctuations, the temperature of the adjacent rock mass gradually increases until it reaches a stable state. The analysis of the strength and stability of the surrounding rock can be proceed without considering the influence of periodic temperature fluctuations. The sealing layer is significantly affected by the dual effects of temperature and air internal pressure, necessitating the consideration of thermal-mechanical fatigue in its design. The characteristics of hoop stress and radial strain exhibit notable disparities between the inner and outer surfaces of concrete lining. Depending on the working conditions, the hoop stress on the inner and outer surfaces may approach the compressive and tensile strengths of concrete, both of which are crucial design considerations. Concrete lining mitigates the pressure of surrounding rock, albeit with limited effectiveness. At an appropriate burial depth, selecting the appropriate inflation pressure ensures that the surrounding rock remains in an elastic state.