Development of Coconut Oil/Capric Acid Eutectic Phase Change Material with Graphene as Latent Thermal Energy Storage

In this study, a eutectic mixture of coconut oil (CO)-capric acid (CA) was synthesised and investigated with the aim of producing newly eutectic phase change materials (PCMs) with improved thermal properties as thermal energy storage (TES). Although eutectic fatty acids have been widely studied, the information on the thermal properties of the CO-CA eutectic mixture is very limited to the authors’ knowledge. Coconut oil offers good thermal and chemical stability with acceptable latent heat and melting temperature. The thermal properties of the eutectic mixture were enhanced by graphene addition at 1, 3, 5, and 7 wt% concentrations. The surfactant was added to the mixture to avoid the sedimentation of graphene. The material characterisation techniques include thermal conductivity measurement, Fourier Transform Infrared (FTIR) spectroscopy, Differential Scanning Calorimetry (DSC), and Thermal Gravimetric (TG) analysis. The results revealed that the pure eutectic CO-CA has a melting point of 23.5°C with a latent heat of 110 J/g. With the addition of graphene, the melting point of the mixture is 22.8°C, and the latent heat is 103 J/g. Overall, the findings showed that the thermal conductivity improved by 21.7% for 7wt% graphene concentration. The spectra from FTIR and TG analysis showed that the mixture offers thermal and chemical stability. The promising findings in this study showed that the newly developed eutectic mixture with improved thermal properties makes them favourable to be used as TES for low-temperature applications.