Parameter design of the compressed air energy storage salt cavern in highly impure rock salt formations

Compressed air energy storage (CAES) salt caverns are suitable for large-scale and long-time storage of compressed air in support of electrical energy production and are an important component for realizing renewable energy systems. In this paper, the use of sediment voids in highly impure rock salt formations for CAES is proposed. The interaction between the insoluble sediment and the cavern wall is analyzed. A geomechanical model is established to optimize the design parameters of CAES salt caverns. The simulation results show that as the cavern height increases, the displacement decreases in the bottom sediment region and increases in the waist. As the internal air pressure increases, the safety factor increases, while the volume shrinkage and displacement decrease. The plastic zone and the strength utilization rate decrease, and the safety factor increases with increasing pillar width. Based on the above results, the long cylindrical cavern is recommended to have a height in the range of 260–280 m and a diameter of 80 m. The minimum internal air pressure is 10–12 MPa, and the maximum internal air pressure is 16–18 MPa. The pillar widths between caverns are approximately 2.0–2.5 times the cavern diameter. In this study, for a single cavern with a diameter of 80 m and a height of 260–280 m, the upper free volume (excluding sediment) and the lower sediment filled volume of a single cavern are approximately 4.6–5.0 × 105 m3 and 7.2–7.8 × 105 m3, respectively. The sediment voids used for storing compressed air increase by at least approximately 3.6 × 105 m3, which is approximately 0.8 times the upper free cavern volume. The results show that the CAES salt cavern in highly impure rock salt is feasible and has great potential.