Introduction  There is an obvious pressure energy loss in the electricity output process of Compressed Air Energy Storage (CAES) system, which is caused by pressure regulating valves. The existing of pressure energy loss results in an efficiency drop of CAES system.

  Method  In this manuscript, the ejector technology was introduced into CAES systems to finish the air flow pressure regulating process. The target air flow with middle pressure parameter could be obtained by high pressure air flow ejecting low pressure air flow in ejectors. It causes less pressure energy loss than pressure regulating valves. In this investigation, we built and analyzed the performance of three CAES systems with three different pressure regulating methods, including "pressure regulating process only through valves" , "ejectors with fixed throat area" and "ejectors with adjustable throat area" .

  Result  The results show that ejector technology can recover the pressure energy loss by increasing working air flow amount. There is about 2% percent additional air flow under ejector with fixed throat area. There is also about 4.1% percent additional air flow under ejector with adjustable throat area. The energy conversion efficiency of CAES system with pressure regulating valves is 59.26%, and those of CAES systems with fixed ejector and adjustable ejector increase to 59.60% and 59.97%, respectively.

  Conclusion  The optimized CAES systems can be combined with renewable resource power plants to form united-power plants, which has positive effect in grid-connection of renewable power.