Shape stable composite phase change material with improved thermal conductivity for electrical-to-thermal energy conversion and storage

Limited thermal conductivity and leakage of phase change material (PCM) are among the most challenging obstacles that impede their effective applications in real-world scenarios. This study focussed on enhancing the thermal conductivity (TC), address leakage issues and incorporate thermoelectric conversion capabilities by using a single multifunctional scaffold. The shape stable PCM (ss-PCM) composite has been prepared using medium temperature range (~46 °C) commercial grade paraffin wax (PW) as organic PCM while expanded graphite (EG) as an encapsulating scaffold. The composite was prepared using vacuum impregnation method, incorporating various weight percentages (wt.%) of EG. In particular, the three wt.% of EG that has been used to encapsulate PCM are 5 % (ss-PCM1), 10 % (ss-PCM2) and 15 % (ss-PCM3). Then the composite was evaluated for its thermal stability, potential chemical interactions, leakage prevention, optical properties, thermal conductivity and thermo-electric conversion capability. Results revealed that the incorporation of 15 wt% EG in PCM (ss-PCM3) demonstrated no traces of leakage even after heating the composite at 60 °C. In addition, a significant increment of 447 % in thermal conductivity and 98 % in light absorbance has been observed. However, the composite showed a slight decrement of 13.83 % in latent heat related to base PCM. Finally, ss-PCM3 was put through to 500 heating-cooling cycles to evaluate its reliability and potential defects due to thermal fatigue. The characterization results of the composite were in close agreement before and after the thermal cycling, indicating its potential for practical applications. The electro-thermal conversion measurement findings indicate that the ss-PCM3 can achieve a conversion ability of 61.89 % when operated at 4.8 V. Several potential applications for this composite include energy-efficient buildings, infrared thermal concealment, solar energy utilization, and heat insulation.