Effect of Ellipsoidal Capsule Geometry on Energy Storage Characteristics of Packed Bed Encapsulated Phase Change Material System

Abstract This study aims to investigate the use of ellipsoidal capsules in a thermal energy storage system based on phase change materials (PCMs). The research focuses on two types of structured packed bed arrangements: uniform and graded. The objectives are to analyze the impact of the aspect ratio or slenderness of the capsules on the energy storage characteristics and to examine the effects of using capsules with varying shapes in the same packed bed. The findings indicate several advantages of using nonconventional ellipsoidal capsules over spherical ones. Specifically, the use of ellipsoidal capsules of aspect ratio 0.34 leads to an average 16.2% improvement in melting time. Additionally, the study demonstrates that a graded packed bed arrangement outperforms conventional spherical encapsulated PCM thermal energy storage systems by a margin of 20–30%. Overall, this investigation highlights the potential of employing ellipsoidal capsules in phase change material-based thermal energy storage systems, showcasing their enhanced performance compared to spherical capsules.