Thermodynamic and economic analysis of an adiabatic compressed air energy storage system coupled with an air separation unit

Energy storage technologies facilitate the integration of renewable energy sources and enhance both the stability and operational efficiency of power grids. In recent years, adiabatic compressed air energy storage (ACAES) systems have reached a relatively mature stage of development. Accordingly, an innovative ACAES-ASU integrated system is proposed in this study to enhance renewable energy utilization and mitigate the high energy consumption and operational costs typically associated with the air separation unit (ASU). During the energy storage stage, ambient air is compressed in multiple stages and stored in the salt cavern, while the resulting compression heat is captured and retained by a thermal energy storage (TES) system. In the energy release stage, the stored thermal energy is utilized to preheat the air prior to expansion in the turbine units. Supplying high-pressure air to the ASU significantly reduces the load on the main compressor (MCP), and a load-shifting strategy is employed to power auxiliary ASU components. Following a multi-parameter genetic algorithm optimization of the proposed ACAES-ASU system, under the air supply ratio of 6.50 %, the integrated system demonstrates favorable performance, achieving an overall efficiency of 71.62 % and an exergy efficiency of 79.71 %. The air supply strategy reduces the ASU's energy consumption for gas production during the energy release stage by 42.91 %. Consequently, the net present value (NPV) and levelized cost of electricity (LCOE) of the ACAES-ASU system are estimated at 650 million USD and 0.085 USD/kWh, respectively.