Thermodynamic Models for the Temperature and Pressure Variations Within Adiabatic Caverns of Compressed Air Energy Storage Plants

The temperature and pressure variation limits within the cavern of a compressed air energy storage (CAES) plant affect the compressor and turbine works, the required fuel consumption and therefore the overall plant performance. In the present work, the thermodynamic response of adiabatic cavern reservoirs to charge/discharge cycles of CAES plants are studied. Solutions for the air cavern temperature and pressure variations were derived from the mass and energy conservation equations, and applied to three different gas state equations, namely, ideal, real, and a self-developed simplified gas models. Sensitivity analyses were conducted to identify the dominant parameters that affect the storage temperature and pressure fluctuations. It is demonstrated that a simplified gas model can adequately represent the air thermodynamic properties. The stored air maximal to minimal temperature and pressure ratios were found to depend primarily on, both the ratio of the injected to the initial cavern air mass, and the reservoir mean pressure. The results also indicate that the storage volume is highly dependent on the air maximum to minimum pressure ratio. Its value should preferably be in between 1.2 and 1.8, where the exact selection should account for design and economic criteria.