Integrated cold release-purification method for enhanced efficiency in packed bed cryogenic energy storage systems

Abstract

This study focuses on the critical need for cryogenic thermal energy storage, particularly for liquid air energy storage systems that have recently drawn extensive attention. A novel method integrating a solid particle packed bed with air purification was proposed and validated, wherein the cold storage unit freezes moisture and carbon dioxide in the ambient air to enhance the overall energy and material efficiency of the system. Parametric numerical analysis was performed to examine the dynamic characteristics of the novel thermal storage with particle diameters varying across a wide range of 8–150 mm. The freezing regions of water and CO₂ in thermal storage and their influence on energy storage performance were analyzed according to temperature profiles in the packed bed. Results showed that smaller particles promote convective heat transfer, but also significantly increase pressure drop. When the particle diameter increased from 8 mm to 80 mm, the pressure drop in the cold storage decreased by 79.5 %. With constant cold storage demand in each cycle, the height of the packed bed with 80 mm particles increased by 62.4 % compared to the 8 mm configuration. Economic analysis showed that the construction cost of the packed bed increases with particle diameter, while the operational cost decreases. For packed beds with 20 mm and 80 mm particles, the cost-equilibrium period is 4.8 years. This research provides a theoretical basis for particle size optimization of cold storage and a high-efficiency alternative option for the design of cryogenic energy storage.