Fatty acid from recycled waste cooking oil as a phase-change material for thermal storage systems

Abstract

Fatty acids derived from waste cooking oil (WCO) are successfully processed as sustainable phase-change materials (PCMs) for thermal energy storage. This study investigated the conversion of WCO into fatty acid-based PCMs through hydrolysis and hydrogenation, optimizing reaction parameters to enhance thermal properties. A logarithmic model was developed to describe the relationship between hydrogenation time and the adjustment of melting point. The study also examined the correlation between WCO-derived fatty acids (WCOFAs) and their chemical structure, providing insights into optimizing hydrogenation conditions to achieve desired melting points (between 15 °C and 60 °C). The effects of different oil mixtures on thermal characteristics, such as melting point and latent heat, were analyzed to tailor WCOFA-based PCMs for industrial applications. Experimental results indicated that increasing hydrogenation time reduces carbon–carbon double bonds, increasing the melting point and latent heat, with fully hydrogenated WCOFAs exhibiting properties comparable to those of commercial PCMs (∼150 J g⁻¹). This study highlights WCOFAs as cost-effective, environmentally friendly alternatives for thermal energy storage, contributing to sustainable waste management and resource utilization.