Coupled thermodynamic and thermomechanical modelling for compressed air energy storage in underground mine tunnels

Compressed air energy storage (CAES) in underground mine tunnels using the technique of lined rock cavern (LRC) provides a promising solution to large-scale energy storage. A coupled thermodynamic and thermomechanical modelling for CAES in mine tunnels was implemented. Thermodynamic analysis of air during CAES operation was carried out. Difference in temperature and pressure evolution when considering real air thermophysical properties and varying heat transfer properties, as opposed to a simplified thermodynamic model, was revealed. Elastic plane strain (EPS) analysis was implemented to evaluate the influences of initial stress of the lining structure, quality grades of surrounding rock, thermal effect and the cyclic nature of loadings on mechanical behaviour. 3D elastoplastic damage (3DEPD) analysis considering steel reinforced concrete (SRC) lining was implemented to evaluate the damaged mechanical behaviour. Divergences between EPS analysis and 3DEPD analysis were unveiled. It is suggested that, when it comes to tunnel stability, simplifying the thermodynamic model is of least concern, instead, the initial stress of the lining structure is of critical importance and 3DEPD analysis considering SRC lining shall replace EPS analysis. The insights of this study will provide important guidance for the designing and feasibility study of LRC in mine tunnels for application of CAES.