RESUMEN
This study focuses on modifying the porous structure of acid-treated rice husk ash (ARHA) to enhance the thermal energy storage capacity of poly(ethylene glycol) (PEG) confined within shape-stabilized phase change materials. The modification process involved a cost-effective sol-gel method in which ARHA was initially dissolved in an alkaline solution and subsequently precipitated in an acidic environment. ARHA, being a mesoporous SiO2-based material with a high surface area but low pore volume, had limited capacity to adsorb PEG (50%). Furthermore, it hindered the crystallinity of impregnated PEG by fostering abundant interfacial hydrogen bonds (H-bonds), resulting in a diminished thermal energy storage efficiency. Following modification of the porous structure, the resulting material, termed mARHA, featured a three-dimensional macroporous network, providing ample space to stabilize a significant amount of PEG (70%) without any leakage. Notably, mARHA, with a reduced surface area, effectively mitigated interfacial H-bonds, consequently enhancing the crystallinity of impregnated PEG. This modification led to the recovery of thermal energy storage efficacy from 0 J/g for PEG/ARHA to 109.3 J/g for PEG/mARHA. Additionally, the PEG/mARHA composite displayed improved thermal conductivity, reliable thermal performance, and effective thermal management when used as construction materials. This work introduces a straightforward and economical strategy for revitalizing thermal energy storage in PEG composites confined within RHA-based porous supports, offering promising prospects for large-scale applications in building energy conservation.
RESUMEN
Poly(ethylene glycol) (PEG) boasts excellent thermal energy storage capabilities but lacks efficiency in thermal conductivity and solar absorption. Simultaneously, the escalating concern surrounding the substantial volume of discarded cotton fabric underscores environmental issues. In this study, we devised composite phase change materials (PCMs) by embedding PEG into a carbon cotton material (CCM), varying PEG content from 50 to 80%, and conducted a comprehensive analysis of their thermal properties and solar-to-thermal conversion. The CCM, crafted from a waste 100% cotton towel through carbonization, provided an optimal porous structure that accommodated a significant 70% PEG content without any leakage, thanks to interactions such as surface tension, capillary forces, and interfacial hydrogen bonds. These PEG/CCM composites exhibited impressive crystallization fractions (>92%), resulting in notable thermal energy storage capacities ranging from 85.3 to 143.2 J/g as the PEG content increased from 50 to 80%. Moreover, these composites showed high thermal stability and exceptional cycling durability even after 500 melting/crystallization cycles. Notably, their thermal conductivities markedly increased to a range of 0.46-0.85 W/m·K compared to pure PEG's modest 0.24 W/m·K. Furthermore, the PEG/CCM composites substantially augmented visible and near-infrared (VIS-NIR) light absorption. Evaluation of solar-to-thermal conversion illustrated the composite's ability to efficiently convert solar energy into thermal energy, storing and subsequently releasing it through melting and crystallization processes. This study introduces a novel class of composite PCMs characterized by cost-effectiveness, outstanding thermal performance, and impressive solar-to-thermal conversion capabilities. These composite PCMs hold significant promise for large-scale solar-to-thermal energy storage applications while contributing to the sustainability of cotton waste management.
