Integrated LNG cold energy-based system combining liquid air energy storage and air separation unit: A novel synergistic solution for supply-demand coordination and power grid peak-shaving

Large amount of cold energy stored in liquefied natural gas (LNG) exhibits huge application potentials and also the issues of significant cold load fluctuations and low utilization efficiency, in view of which this study proposes an integrated LNG cold energy-based system combining liquid air energy storage (LAES) and air separation unit (ASU), designated as LNG-LAES-ASU. Based on the variations in LNG temperature and electricity pricing, three operating modes (i.e., energy storage, power generation, and conventional modes) have been proposed for the system. The thermodynamic performance of the system is evaluated through process simulation, sensitivity analysis of key parameters and exergy analysis. The results show that the integrated system increases the exergy efficiency by 10 %, raises the ASU product output by 15 %, reduces the operating costs by 38 %, and enhances the overall revenue by 49 % compared with the standalone LNG cold energy ASU. Additionally, the system achieves a round trip efficiency of 72.9 % and an exergy efficiency of 75 % with an air expansion temperature of 150 °C. Economically, the system exhibits a dynamic payback period of 5.55 years within a 20-year lifespan, which could be further reduced with higher external heat source temperatures. This system can enhance the spatiotemporal coordination of LNG cold energy supply and demand by integrating its utilization with the power grid peak-shaving operations, thereby providing an efficient solution for large-scale LNG cold energy utilization.