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A coupled thermo-hydro-mechanical model for evaluating air leakage from an unlined compressed air energy storage cavern

Wu, Di, Wang, J.G., Hu, Bowen, Yang, Sheng-Qi
Renewable energy 2020 v.146 pp. 907-920
air, caves, energy, guidelines, mass flow, mathematical models, model validation, permeability, renewable energy sources, seepage, storage technology, temperature
Compressed air energy storage (CAES), a large-scale energy storage technology, is a link between unstable renewable energy and conventional power grids. Air leakage may significantly impact the CAES efficiency. This paper presented a coupled thermo-hydro-mechanical model to evaluate the air leakage from an unlined CAES cavern. This model was validated with field tests, numerical simulations, and an analytical solution. The impacts of air leakage on the variations of temperature and pressure within a CAES cavern and the air seepage in surrounding rock were numerically analyzed. Finally, the effects of rock permeability, mass flow rate of air injection, and cavern radius on air leakage were investigated. It is found that rock permeability is a key parameter to air leakage. For the first cycle and under operational pressure of 5 and 8 MPa, rock permeability should be smaller than 3 × 10−19 m2 to satisfy the tightness requirement for an unlined CAES cavern. That is less than 1% daily air leakage percentage. Larger cavern radius and higher mass flow rate of air injection are helpful to reducing the daily air leakage percentage. These results can provide guidelines for tightness requirements for existing cavern repair or new CAES cavern construction design.