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This study aims to investigate the thermal properties of a phase change material (PCM) based on coconut oil for building energy storage applications. Coconut oil is classified as an organic PCM composed of fatty acids made from renewable feedstock. However, low thermal conductivity is one of the major drawbacks of organic PCMs that must be improved. Graphene could be an effective material to enhance the thermal performance of organic PCMs. In this study, coconut oil with a latent heat capacity of 114.6 J/g and a melting point of 17.38°C was used. PCMs were prepared by sonicating graphene into coconut oil, as a supporting material. The mass fractions of the prepared PCMs were 0, 0.1, 0.2, 0.3, 0.4 and 0.5. Thermal conductivity tests were performed using a KD2 thermal property analyser under different ambient temperatures of 5, 10, 15, 20 and 25°C simulated with a circulating thermostatic bath. The latent heat, melting point and freezing point were determined through differential scanning calorimetry, the thermal stability was determined using thermogravimetric analysis (TGA) and the morphology and chemical structure were examined using transmission electron microscopy and Fourier-transform infrared spectroscopy, respectively. The results of this study showed that graphene addition to coconut oil improved the thermal performance, with the highest improvement seen in a 0.3 wt% sample at 20°C. The latent heat decreased by 11% owing to molecular movements within the PCM. However, TGA revealed that the composite PCMs showed good thermal stability in ambient building temperature ranges.

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This study aimed to characterize Phase Change Materials (PCM) by improving their properties using shape stabilization; this was achieved by adding nanoparticles as a support material. PCM soy wax was modified using two nanoparticles, graphene, and MAXene Ti3AlC2. The synthesis process comprised stirring using a magnetic stirrer and ultrasonication using an ultrasonic processor with various percentages of 0.1, 0.5, and 1 wt.% of soy wax with nanoparticles. Based on the results, the morphologies of graphene and MAXene Ti3AlC2 were found to be in the form of sheets. These sheets had a large surface area, so soy wax could adsorb more nanoparticles to increase the stability of the material. The thermal conductivity increased with increasing percentage addition of nanoparticles. The highest values from the synthesis with graphene and MAXene Ti3AlC2 were 0.89 W/mK and 0.85 W/mK, respectively. The thermal conductivity of soy wax increased with the ratio of pure soy wax and nano-soy wax; the thermal conductivity was 6.01 for soy wax+graphene and 5.71 for soy wax+Ti3AlC2. Differential scanning calorimetry (DSC) results showed an increase in the melting and solidifying points of pure soy wax. The modified soy wax with 0.1 wt.% graphenes experienced a reduction in the melting and solidification points up to 15% and 14%, respectively. Similar results were obtained for 0.1 wt.% MAXene Ti3AlC2. In this case, there was a reduction in the melting and solidifying points by 16% and 13%, respectively. Finally, the addition of MAXene improved the material stability and thermal conductivity of soy wax and has the potential to be used as a thermal energy storage material for building applications.