Improved liquid air energy storage process utilizing LNG cold energy: Continuous and flexible energy storage

Integrating the cold energy of liquefied natural gas (LNG) into liquid air energy storage (LAES) systems represents a significant application for LAES technology. However, the high regeneration energy consumption of the air purification (AP) process in the LAES system, which accounts for approximately 27 % of the total energy consumption during energy storage, severely limits the system's round-trip efficiency. To address this challenge, an LNG-integrated LAES system with air purification (LNG-AP-LAES) has been proposed. This system utilizes backflow gas and expanded air from the energy storage process as the regeneration purge gas for the AP process, effectively eliminating the time constraints imposed by AP on energy storage. The optimized process not only enhances synergy between the charging and discharging phases of LAES but also drastically reduces the regeneration energy consumption of the AP process to just 1 % of the total energy consumption during storage. As a result, the round-trip efficiency of the LNG-AP-LAES system increases from 50.15 % to 67.87 %, while the exergy efficiency improves from 53.38 % to 67.31 %. Parametric optimization analysis reveals that the optimal energy storage pressure for the LNG-AP-LAES system is 12.7 MPa, and the energy release pressure is 9.4 MPa. Under these conditions, the system achieves a round-trip efficiency of 68.17 % and an exergy efficiency of 67.53 %. Economic analysis reveals a payback period of 5.85 years for the LNG-AP-LAES system when the peak-to-valley electricity price ratio is 5:1. The improved process enables continuous and flexible energy storage and power generation, providing a viable scenario for the commercial demonstration of liquid air energy storage technology.