Stability Analysis of Multiple Thermal Energy Storage Caverns Using a Coupled Thermal-Mechanical Model

Cavern Thermal Energy Storage system stores thermal energy in caverns to recover industrial waste heat or avoid the sporadic characteristics of renewable-energy resources, and its advantages include high injectionand-extraction powers and the flexibility in selecting a storage medium. In the present study, the structural stability of rock mass pillar between these silo-type storage caverns was assessed using a coupled thermal-mechanical model in FLAC. The results of numerical simulations showed that thermal stresses due to long-term storage depended on pillar width and had significant effect on the pillar stability. A sensitivity analysis of main factors indicated that the influence on the pillar stability increased in the order cavern depth < pillar width < in situ condition. It was suggested that two identical caverns should be separated by at least one diameter of the cavern and small-diameter shaft neighboring the cavern should be separated by more than half of the cavern diameter. Meanwhile, when the line of centers of two caverns was parallel to the direction of maximum horizontal principal stress, the shielding effect of the caverns could minimize an adverse effect caused by a large horizontal stress.