A new testing system to the permeability coefficient of flexible sealing materials for compressed air energy storage caverns and its application

To accurately assess the airtightness of flexible sealing materials (FSMs) in compressed air energy storage (CAES) caverns, determining the permeability coefficient (PC) of these materials under varying temperatures and pressures is crucial. However, existing commercial gas permeation testing devices are typically limited to low-pressure conditions (with a maximum pressure of 0.1 MPa). To address this issue, a new high-pressure permeation testing system specifically designed for measuring the PC of FSMs in CAES caverns has been developed in this study. The system consists of a compressor, a booster pump, a gas storage tank, intake and exhaust valves, a high-pressure sealing box, a water bath, and a micro gas measurement device. The system enables the testing of PC under various temperatures and pressures, offering advantages over conventional systems in terms of simplicity, ease of use, and result accuracy. Using this system, the effects of temperature, pressure, and thermal aging on the permeability characteristics of FSMs were systematically investigated. Based on the experimental data, an empirical predictive model was established to describe the relationship between the permeability coefficient and temperature/pressure. The findings revealed that: (1) The permeability coefficient is highly sensitive to temperature variations, exhibiting a typical nonlinear growth. Under a constant pressure of 10 MPa, when the temperature increased from 25 °C to 80 °C, the permeability coefficient rose significantly from 3.09 × 10⁻¹⁷ to 12.64 × 10⁻¹⁷ [m³·(STP)·m/(m²·s·Pa)], representing a 309 % increase; (2) At the same temperature, the permeability coefficient showed a slight decreasing trend with increasing pressure; (3) After 28 days of thermal cycling aging (0~65°C), the material's permeability coefficient decreased by 3.62 %, indicating that moderate thermal aging can enhance gas barrier performance. These findings provide a theoretical foundation for the airtightness evaluation of FSMs in CAES caverns.