Resource utilization of spent coffee grounds into eco-friendly phase change composite for thermal energy storage...

Thermal energy storage systems have gained increasing attention in recent years as effective solutions for improving energy efficiency and promoting sustainability. In this study, an eco-friendly phase change material (PCM) composite was developed by upcycling spent coffee grounds (SCG) into a value-added thermal energy storage material. SCG were employed as a natural supporting matrix, while a eutectic mixture of lauric acid (LA) and stearic acid (SA) with a mass ratio of 70:30 served as latent heat storage component. The composite was prepared by using a vacuum impregnation method. To determine the optimal PCM loading, the LA-SA content was varied between 10 and 70 wt%, and a maximum stable loading of 30 wt% was identified based on leakage performance. The leakage behavior, morphological structure, chemical composition, and thermal properties of composites were systematically investigated by leakage tests, FTIR, XRD, DTA/TG, and DSC analyses. 5%CuO@e-PCMC coded composite showed an effective heat storage efficiency (E), relative thermal storage efficiency (μ), and enthalpy efficiency (λ) as 9%, 80%, and 0.1, respectively. Thermal analysis tests confirmed that the composite structure remained stable without significant degradation over repeated phase change cycles. The results demonstrated that the developed SCG-based PCM composite was a cost-effective and an environmentally friendly candidate for low-temperature thermal energy storage applications, particularly in 33-36 °C range, making it well suited for textile and thermal comfort applications. The ability of SCG to stably accommodate up to 30 wt% of the LA-SA eutectic mixture highlighted their potential as a sustainable and natural alternative supporting material for thermal energy storage and thermal management systems.