Analysis of options in combining compressed air energy storage with a natural gas combined cycle

Energy storage is becoming increasingly important for addressing the imbalance between power demand and supply. This study analyzes the performance of a dual system that combines compressed air energy storage (CAES) with a natural gas combined cycle (NGCC). The first was thermal integration, where the exhaust air from the CAES outlet is supplied to the bottoming steam cycle of the NGCC. The second was flow integration where some air from the CAES high-pressure expander outlet is injected to the gas turbine combustor of the NGCC. The reference design conditions were an inlet temperature of 900 degrees C for the low-pressure expander (LPE) of the CAES and a turbine inlet temperature of 1500 degrees C for the NGCC. Simple thermal integration could not improve the performance compared to independent operation, but the flow integration improved the power. An 8 % increase in power is expected at 20 % injection. When both the thermal and flow integrations were used simultaneously, the power increment decreased slightly, but the efficiency improved. An increase in the temperature of the LPE improves the CAES performance but reduces the synergistic effect from the integration with the NGCC.