Optimization of an Lng-Coupled Liquid Air Energy Storage System Using Air Expansion Refrigeration: An Integrated Theoretical and Simulation Approach

Abstract

The integration of Liquefied Natural Gas (LNG) cold energy with a Liquid Air Energy Storage (LAES) system addresses the inefficiencies inherent in conventional LAES setups due to insufficient cold energy. This study analyzes an LNG-LAES system utilizing air expansion refrigeration, employing both theoretical analysis and computational simulations to explore the influence of adjustable parameters (namely charging pressure, secondary airflow ratio, and LNG flow ratio) on energy consumption and power output. Our findings reveal significant interdependencies among these parameters. Under fixed charging pressure, maintaining either the LNG flow ratio or the secondary airflow ratio at a constant level enables the determination of an optimal value for the remaining parameter, thus maximizing round-trip efficiency at that pressure. A quadratic relationship between round-trip efficiency and charging pressure was established, demonstrating an initial increase in efficiency with rising pressure, followed by a decline. Optimization of a 10 MW LNG-LAES system achieved a round-trip efficiency of 70%, with subsequent exergy analysis yielding an exergy efficiency of 66.05%. This research elucidates key optimization strategies for LNG-LAES systems, enhancing their operational performance and efficiency.

Keywords: Liquid air energy storage, The cold energy of LNG, Air expansion refrigeration, Charging pressure, Round-trip efficiency