Highly conductive phase change composites based on paraffin-infiltrated graphite panels for photo/electrothermal conversion and storage

Abstract

The extensive utilization of phase change materials (PCMs) for thermal energy harvesting, storage, and thermal management is often constrained by their inadequate thermal and electrical conductivity, form instability, and lack of photoabsorbance. To overcome these challenges, a phase change composite was prepared by vacuum infiltration of paraffin wax (PW) into a highly conductive scaffold of graphite panel (GP). Various PW grades with different phase change temperatures were tested to study their suitability for a wide range of applications. Graphite-based skeleton ensured high thermal and electrical conductivity and impeded liquid PW leakage in all composites. The composite thermal conductivity was enhanced up to 677 and 22 times that of PW in the axial and radial directions, respectively. The latent heat capacity of the composites varied between 88.5 and 102.7 J/g, depending on the PW grade. The composites are capable of harvesting thermal energy either by applying a small voltage of 1.8 V with a high electrothermal conversion efficiency of up to 71.1 % or by simulated sunlight with an excellent photothermal conversion efficiency of up to 76.5 %. The simple fabricating technique, a broad range of applications with different PW grades, and their efficient thermal properties meet the requirements for widespread utilization in thermal energy harvesting, storage, and thermal management of electronics, buildings, etc.