Waste pomelo peels-derived ultralow density 3D-porous carbon aerogels: Mechanisms of “Soft-rigid” structural formation and solar-thermal energy storage conversion

Renewable energy from a natural resource is currently significant awareness and is being discussed by researchers worldwide to solve the energy crises. This work paves the way for developing efficient solar-to-thermal energy storage conversion based on the "Soft-rigid" structural formation mechanism of carbon aerogel. Here, low-cost wasted pomelo peels derived three-dimensional (3D) porous networked carbon aerogels (PCAs) as a support matrix for paraffin wax (PW) as organic phase change materials (PCM). Moreover, composite phase change materials (CPCMs) show ultralow density, excellent thermal stability, enhanced thermal and electrical conductivities, outstanding shape stability, and leakage-proof ability. The impregnation loading ratio of PW-based CPCM3 reached 95.6%, ascribed to the unique "Soft-rigid" network structure of PCAs. More importantly, the change in the "Soft-rigid" structure endows PCA750 with a high compressive strength of 466 kPa at 60% compression rates. The obtained CPCM2 displayed a significant latent thermal storage capacity of 159.9 J/g and exhibited superior thermal reliability after 25 frequent heating/cooling cycles. The effective carbonization temperature of CPCM2 caused a significant increase in light absorbance; thus, high solar-to-thermal energy conversion efficiency (85.1%). This study provides new ways to convert waste low–value biomass materials into high-value renewable energy (solar-thermal-electricity) with long-term reusability via a simple and green technology. These are tremendous economic benefits in the thermal energy storage sectors.