Material Evaluation and Charging–Discharging Characteristics of Packed‐Bed Cold Energy Recovery Units

Liquid air energy storage (LAES) is a promising large‐scale energy storage technology owing to its high energy density and environmental compatibility. The thermal behavior of the packed‐bed cold storage unit plays a decisive role in determining system efficiency. In this work, a cryogenic experimental platform is developed to characterize thermal‐front propagation, thermocline thickness evolution, and cycle‐dependent performance. A comprehensive evaluation integrating thermophysical properties, cryogenic structural stability, and practical viability is used to screen candidate filler materials. Among candidate fillers, cobblestones demonstrate superior overall performance by combining high thermal conductivity, moderate specific heat capacity, and excellent structural integrity after repeated cryogenic cycles. Experimental results show that lower inlet temperature slows thermal‐front propagation and increases thermocline thickness, whereas higher flow rate enhances convective heat transfer but broadens the temperature distribution. The best performance, considering thermocline control and process duration, occurs at a medium inlet temperature (121.9 K) and low‐flow rate (0.037 kg/s). After six cycles, cycle efficiency increases from 18.3% to 98.1% without observable thermal or structural degradation. These results confirm the repeated‐use stability of cobblestone‐packed beds and provide experimental validation for the LAES system design.