Numerical and experimental analysis of weathering effect in liquid air tank of liquid air energy storage system

Liquid Air Energy Storage (LAES) is a promising large-scale energy storage technology that relies on the liquefaction and subsequent re-gasification of air to generate electricity. However, during long-term storage, the preferential evaporation of nitrogen due to heat ingress leads to an increase in oxygen concentration, known as the weathering effect. This phenomenon presents safety hazards and affects the thermodynamic performance of the system. This study quantitatively investigates the weathering effect in liquid air storage tanks through both experimental measurements and a non-equilibrium thermodynamic model. A laboratory-scale cryogenic storage system was developed to measure oxygen concentration changes over time, and a non-equilibrium model for mixture fluid was formulated based on mass and energy conservation principles. The model, validated against experimental data, accurately predicts oxygen concentration dynamics and boil-off gas (BOG) rates. The validated model was further used to determine the maximum allowable storage duration before oxygen concentration exceeds 23.5 vol%, a critical safety threshold set by industrial guidelines. The study also establishes a relationship between boil-off rate and insulation performance, enabling the optimization of storage tank design. The results indicate that oxygen concentration increases with time, with the rate of increase accelerating for higher initial oxygen compositions. The proposed model provides a robust tool for assessing long-term storage performance and contributes to the safe and efficient operation of LAES systems.