Bio-based pomegranate peel/paraffin wax phase change composites for enhanced thermal energy storage

• Pomegranate Peel matrix encapsulates Paraffin Wax (PW) via vacuum impregnation. • Composite achieves 52.2 wt% PW loading with no leakage during melting. • Theoretical Paraffin encapsulation reached a relative enthalpy value of 53.86%. • High enthalpy efficiency (REE around 100%) indicates effective encapsulation • Particles sized 0.2–0.315 mm allow max PW loading and strength of 2.7 MPa. • The addition of 5% aluminum improves the thermal conductivity of the host matrix. • Pilot test shows thermal response of composite closely matches pure PW. Composites incorporating Phase Change Materials (PCMs) have regained interest for their multifunctional potential in advanced thermal management systems. These materials provide a sustainable and efficient solution for thermal energy storage, offering thin, lightweight, mechanically robust, and thermally insulating or conductive structures. However, leakage in the molten state remains a critical barrier to large-scale deployment. To address this limitation, we developed a low-cost, bio-sourced composite matrix using pomegranate peel (PPM), an abundant agricultural waste, as a porous support for PCM encapsulation. The selected PCM, paraffin wax (PW) with a melting point of approximately 60 °C, was impregnated into the PPM matrix using vacuum-assisted techniques. Comprehensive micro- and macroscopic characterizations, including both static and dynamic analyses, were performed on raw materials and the resulting composites to assess the effects of processing. The results reveal a strong physical affinity between the fossil-based PCM and the biosourced matrix, enabling a high PCM loading rate of 52 wt%. This loading corresponds to a theoretical encapsulation ratio of 54%, which aligns closely with experimental data (R² = 99.77%). The PPM/PW composite reached a latent heat of 68 J/g, and exhibited excellent mechanical strength, with a compressive force of 226 ± 1.26 N and stress of 2.9 MPa for particle sizes below 125 µm. Furthermore, the most promising composite was tested in a pilot-scale heat exchanger, demonstrating significant potential for mid-temperature thermal energy storage and management. This leakage-resistant, eco-friendly composite derived from agricultural waste, offers a viable pathway toward sustainable thermal energy systems.