Pomegranate peels as a potential eco-friendly support for sustainable energy storage phase change composites

Advanced energy storage materials gained wide interest since they proved high energy efficiency and renewable source utilization. However, environmental issues, high cost, and energy consumption in the manufacturing process of certain latent heat storage composites let scientists look for more efficient and suitable alternatives. Bio-based materials have shown promising solutions to be used as supporting matrices. In this study, pomegranate peels (PGP) have been investigated as an eco-friendly material for elaborate porous structures. Four matrices have been prepared; two from raw PGP differ by the extraction of tannins, and two other ones were transformed to activated carbon using physical (PHAC) and physicochemical (PCAC) processes. The obtained samples were loaded with paraffin wax (RT27) by direct and vacuum impregnations for different particle sizes. The loading rates were ordered as follows: 40.55%, 48.90%, 44.29%, and 54.41% for RPGP, WPGP, PHAC, and PCAP, respectively. The maximum loading amount of PCM was achieved by vacuum impregnation, and for the smallest particle size, using the PCAC sample, it reached almost 55% wt. Different techniques were used to characterize these samples such as TG/DTA, DSC, FTIR, and SEM. The FTIR and TG/DTA analyses of the obtained composites proved their chemical compatibility and thermal stability. According to DSC results, the WPGP had the highest latent heat of melting and freezing of 55.723 J/g and 44.702 J/g, respectively. This result proved a good affinity between pomegranate peel and organic PCM and efficient leakproof during heating and cooling cycles. Thus, PGP can be considered as a potential low-cost material to support PCM that can be used in different energy storage applications.