This work presents an experimental analysis of the thermal performance of a phase change material (PCM)-integrated thermal energy storage (TES) system designed for sustainable water heating. While traditional latent heat storage often employs vertically stacked capsules that restrict fluid circulation and uniform heat transfer, this study introduces a novel unstacked spherical encapsulation configuration within a compact tank with a 1:1 aspect ratio (AR). A cylindrical TES tank with a 1:1 AR (280 mm height × 280 mm diameter) was examined under controlled charging and discharging cycles in 2 configurations with and without PCM integration. The PCM, paraffin wax, encapsulated within 14 stainless steel spherical capsules, was characterized using thermo-gravimetric analysis and differential scanning calorimetry, disclosing a melting range of 69–74.4 °C and excellent thermal stability. The results demonstrate that this design innovation notably mitigates thermal dead zones, increasing thermal efficiency from 55.62% to 61.97% and extending the delivery of usable hot water (> 60 °C) by 100% (from 30 min to 60 min). The unstacked spherical encapsulation enhanced heat-transfer uniformity, promoted thermal stratification, and prolonged discharge duration. The proposed configuration demonstrates significant potential for solar water heating systems and medium-temperature industrial processes, offering an efficient, compact, and thermally stable TES solution. • Unstacked PCM spheres improve heat transfer and eliminate thermal dead zones. • Thermal efficiency enhanced by 6.35% through latent heat storage integration. • Functional discharge duration (>60 °C) extended by 100% in the compact TES tank. • Cumulative heat energy release increased from 21,102 to 24,493 kJ. • Paraffin wax exhibits excellent cyclic stability for sustainable water heating.
Shanmugavalli et al. (Thu,) studied this question.