Fatty Acid/Expanded Graphite Composites as Phase Change Material for Latent Heat Thermal Energy Storage

Abstract

The fatty acid/expanded graphite (EG) composites as phase change material (PCM) for latent heat thermal energy storage were prepared by means of vacuum impregnation method and their thermal properties and heat charging/discharging characteristics were determined. In the composites, the fatty acids (capric, lauric, and myristic acids) act as a phase change latent heat storage material, and the EG serves like an absorptive material that penetrates melted fatty acid into its porous structure. The maximum fatty acids absorption of EG was found as 80 wt% without melted fatty acid oozing from the composites. Thermal properties of fatty acid/EG composites were measured by differential scanning calorimetry (DSC) method. DCS results indicated that the melting and solidification temperatures of the composite PCMs were almost the same as those of fatty acids, and the latent heats of composites were little less than those of the pure fatty acids. The heat charging and discharging rate of the composites were obviously increased due to expanded graphite that had a high thermal conductivity. The prepared fatty acid/EG composites as PCM have great potential for thermal energy storage applications in terms of their satisfactory thermal properties, improved thermal conductivity, and good heat charging and discharging characteristics.

Keywords:

• expanded graphite
• fatty acid
• phase change material
• thermal energy storage

Acknowledgments

The authors wish to thank Dr. Beytullah Afşin for BET surface area measurement and Dr. Orhan Uzun for DSC and SEM analyses.