Geomechanical and energy analysis on the small- and medium-scale CAES in salt domes

The concept of small- or medium-scale CAES using salt domes at a depth shallower than 500 m and in the capacity of 10–100 MW was recently suggested to address a burden associated with geologic exploration and high investment cost. In this study, we employed an analytical approach to calculate the hoop and radial stresses at the crown and sidewall of the storage cavity under the given cavity depth (h), the dimension of the cavity (W/H), the ratio of horizontal-to-vertical geologic stresses (K), and the internal air pressure (Pin). A good match of the hoop and radial stresses were observed for all tested parameters. The analysis of stress paths implies that the mechanical stability at the crown of the storage cavity could be a decisive factor for allowable storage pressure ranges. The allowable maximum storage pressure (Pmaxallow) can be determined at the moment when the stress path touches the tensile failure criterion, while the allowable minimum storage pressure (Pminallow) needs to be set to maintain stress paths below the shear failure envelope. A higher K and W/H values are advantageous for securing higher storage pressure, and the energy storage capacities are estimated between 1 and 10 MJ/m3 from this study.