Thermodynamic and applicability analysis of a hybrid CAES system using abandoned coal mine in China

China's wind and solar (WS) energy grow rapidly but simultaneously cause high wind and solar resource abandonments. Large-scale energy storage facilities, such as compressed air energy storage plants (CAES) must be complimented to balance the intermittent of these powers. However, in China's wind-solar-rich places (Three North Region), there is no salt formations for CAES construction. Thus we propose a hybrid WS-CAES system using roadways of abandoned coal mines as compressed air storage space. And the thermodynamic performance of the WS-CAES system and the suitability of roadways as compressed air storages are analyzed. This system has an average system efficiency of 50.31% and an energy storage density of 3.23 kW h/m3. Service potential analyses of roadway were conducted for various roadway depths and different permeabilities of concrete lining and surrounding rock. It shows that roadway depth has little influence on the efficiency and output power. When the surrounding rock has a constant permeability (10−16 m2), the maximum allowable permeability of concrete lining was 4.17 × 10−18 m2. The surrounding rock with a permeability of 10−16-10−19 m2 could impose a significant effect on the leakage and efficiency. Finally it is indicated the main ventilation roadway and main haulage roadway have the suitability potential.