Introduction  Energy storage technology becomes an essential supporting technology to build a new power system with renewable energy as the main power source. Liquid air energy storage (LAES) is one of the emerging large-scale energy storage solutions, which is technically and economically feasible and has a wide range of application prospects. The pilot plant built by Highview Power is the only LAES for which test data have been made public. The paper aims to explore the thermodynamic principle of LAES and seek ways to improve the cycle efficiency of LAES.

  Method  A thermodynamic model was established according to the process flow of Highview Power's pilot plant. The thermodynamic model was verified by the test data of the pilot plant. Exergy analysis was carried out. The influence of key operating parameters on the charging and discharging process was studied by the control variable method.

  Result  The results show that the key equipment limiting the cycle efficiency are recycle compressor and evaporator. Increasing the compression pressure and post-throttling pressure, increasing the mass flow rate and inlet temperature of the cryogenic expander, and recovering the cooling capacity of the regenerator are beneficial to improving the liquefaction rate and reducing the energy consumption of liquefaction. Moreover, increasing the high pressure and the inlet temperature of turbine expansion unit can help to improve the output power and cycle efficiency of LAES.

  Conclusion  Some improvement measures are put forward to improve cycle efficiency, such as recovery of compression heat, improvement of compressor isentropic efficiency and reduction of heat transfer temperature difference of evaporator.