This study develops a novel composite phase change material (PCM) based on<lb>paraffin/hydrophobic expanded perlite and exfoliated graphene nanoplatelets as heat transfer<lb>promoter. The experimental analysis was systematically carried out on fabrication,<lb>characterization and testing the thermal storage properties of composite PCM. The micro-<lb>morphology characteristics of composite PCM showed that the xGnP forms an<lb>interconnecting network with the porous EP, indicating the improvement in the heat transfer<lb>performance of composite PCM. Contact angle measurements showed that the composite<lb>PCM can prevent the PCM leakage in the TES system due to the hydrophobic surface<lb>properties of supporting material. Furthermore, thermal conductivity measurements revealed<lb>that the composite PCM with 1 wt% of xGnP boosts the thermal conductivity by up to 49%<lb>compared to the ordinary composite PCM.