Experimental and Numerical Investigations of Small-Scale Lined Rock Cavern at Shallow Depth for Compressed Air Energy Storage

Lined rock cavern at shallow depth is identified as a promising alternative and cost-effective solution for air storage of large-scale compressed air energy storage (CAES) plant. To better understand the thermodynamic process of the compressed air in the underground cavern and the response of the surrounding rock during air charging and discharging phases, a small-scale pilot cavern with concrete liner and fiber-reinforced plastic (FRP) sealing layer was constructed in China. The test program includes one trial charging test, eight short-term charging tests, and one long-term charging test. Numerical simulations were carried out along with the experiments. The results show that the air pressure in the pilot cavern increased/decreased approximately linearly during the charging/discharging phase when the air was injected/released at a constant mass rate. The heat exchanging system could maintain the temperature of the compressed air in the cavern in a designed range. Excellent sealing performance of the FRP was validated in the test, with only 3.2% air mass leaked during the high-pressure storage phase. The influence of the high air pressure on the surrounding rock was limited and only elastic deformation was observed in all the tests. Good quality of rock mass could guarantee the structural safety of the underground cavern under high inner pressure. Generally, there are reasonable agreements between the numerical simulation and the results of the experiment. The study confirms the feasibility of CAES in lined rock caverns at shallow depth.