Experimental study of 1-octadecanol composite phase change materials for solar energy storage system

Due to the low thermal conductivity of traditional phase change materials (PCMs), their widespread application in solar thermal energy storage systems is limited. Improving the heat transfer performance is crucial for optimizing energy storage systems. To address this, this study prepared composite phase change materials (CPCMs) based on 1-octadecanol (OD) using expanded graphite (EG) and nano-diamond particles as thermal conductivity enhancers. The study shows that when OD/EG7 CPCMs are used as the matrix, and diamond particles with an average size of 100 nm and a mass fraction of 3 % are added, the thermal conductivity of the CPCMs reaches 2.992 W/(m & sdot;K), which is a 900.67 % improvement over pure OD. The heat storage/release rates increase by 135.4 % and 84.04 %, respectively. This improvement is attributed to the network structure formed by EG, which effectively reduces the possibility of sedimentation and agglomeration of diamond particles. Additionally, its synergistic effect with the diamond particles creates more heat pathways and a larger heat exchange area, significantly enhancing the heat transfer capacity. After 200 thermal cycles, the phase change temperature of OD/EG7/Diamond3 CPCMs remains almost unchanged, and the phase change latent heat increases, ranging from 216.97 J/g to 227.83 J/g, with an increase of 1.29 % to 2.85 %. This demonstrates excellent thermal cycling stability. This study significantly improves the thermal conductivity of PCMs through the synergistic effect of expanded graphite and nano-diamond particles, providing an efficient solution for solar thermal energy storage systems with broad application prospects.