Shape-Stabilized Phase Change Materials with Expanded Graphite for Thermal Management of Photovoltaic Cells: Selection of Materials and Preparation of Panels

Organic phase change materials (PCMs) have been widely studied for thermal management applications, such as the passive cooling of silicon photovoltaic (PV) cells, whose efficiency is negatively affected by rising temperature. The aim of the present study is to investigate the shape stabilization of PCMs by using expanded graphite (EG) as a highly conductive supporting matrix, leading to the development of novel PCM/EG composites with melting temperatures in the range 30–50 °C. Different organic PCMs were selected and compared, i.e., two paraffins and a eutectic mixture of fatty acids (myristic and palmitic acid). The EG was vacuum-impregnated with organic PCMs, and, subsequently, powdery composites were cold-compacted to obtain dense heat-absorbing panels. The thermal conductivity was enhanced up to 6 W/m·K, guaranteeing composites with a melting enthalpy of 160 to 220 J/g. This study found that the EG vacuum impregnation method is suitable for PCM shape stabilization, and cold compaction allows for the formation of solid panels with improved thermal response. The obtained PCM/EG composites were utilized to produce panels of about 6 × 6 × 2 cm3, suitable for the thermal management of silicon PV.