Synthesis and characterisation of lauric acid phase change material with graphite/carbon nanotubes for thermal energy storage application

Abstract

The advancement of renewable solar energy has led to the emergence of phase change materials (PCMs) as thermal energy storage. Besides acting as a heat storage material, PCM is able to absorb excess heat that enables the reduction of operating temperature of a solar system. Organic PCM (i.e. fatty acid) as a latent heat storage is capable of storing fourteen times more heat per volume unit than other sensible heat storage. This property became among the pulling factors for the researchers in incorporating PCM in their solar system. Nevertheless, commercial organic PCMs encounter several drawbacks for instance low energy conversion ability and the low thermal conductivity. Doping of reinforcement material such as graphene-based material/carbon nanotube is capable of improving the performance of fatty acid as PCM composite. In this work, lauric acid (LA) based PCM using graphite powder (G) and multi-walled carbon nanotubes (MWNT) as filler with mass concentrations of 7 wt% are prepared. Surface morphology and X-ray powder diffraction analysis show no new functional groups were produced after the composite synthesis. Energy storage efficiency, including melting/solidification temperatures and enthalpies, are measured using a differential scanning calorimeter (DSC). It is exhibited that the presence of the supporting material has considerable influence on the phase change temperature and enthalpies, at 38.22 °C and 169.34 J/g for LA-MWNT and 39.03 °C and 120.49 J/g for LA-G. The scanning electron microscope demonstrates that the LA-based PCM could be filled with the pores of graphite and MWNT. LA-MWNT based PCM composite exhibited excellent heat energy storage efficiency (at 89.0%) if compared with LA-G. This indicated that the LA-MWNT has huge potential to be a frontier material for thermal energy storage.