High-performance shape-stabilized phase change material modified by bio-based nano porous graphene for electro-to-thermal and solar-to-thermal conversion and storage

The efficient conversion and storage of thermal energy are crucial for sustainable energy systems, and phase change materials (PCMs) offer a promising solution for latent heat storage (LHS). However, because these materials present problems such as phase-change leakage and low electrical and thermal conductivities, they cannot be used efficiently for energy conversion and storage. In this study, a sustainable bio-nano-phase change material (bio-nano-PCM), which converts electrical and solar energy into thermal energy using waste and recoverable raw materials, is presented. For this purpose, fat extracted from sheep waste was impregnated as bio-PCM into various mass fractions of bio-based nano porous graphene (bio-NPG) from coconut coir using solution impregnation. The SEM image showed that the bio-PCM was well coated in the pores of the bio-NPG. The FT-IR and XRD confirmed the good physicochemical compatibility between the components of the bio-nano-PCM. The DSC analysis indicated that the thermal energy storage material containing 25 % bio-NPG showed the highest melting and freezing enthalpies at 109.37 J/g and 70.19 J/g, respectively. Moreover, the thermal and electrical conductivities of the bio-nano-PCM at 25 % bio-NPG are 0.469 W/mK and 16.2 S/m, which are higher than other samples. The electro-to-thermal energy storage efficiency was 87.06 % at 5 V voltage. In addition, the solar-to-thermal energy storage efficiency under simulated sunlight was 91.16 %. These results show that the bio-NPG displays a quite high electrical and thermal conductivity, which makes it a good candidate to produce a new type of high-performance PCMs. Furthermore, the fat/bio-NPG<inf>25</inf> with no leakage might be a promising choice not only for the electrical and solar energy conversion into thermal energy but also for other thermal storage applications.