Characterization of a novel sustainable shape stabilized phase change material based on oil ash for photovoltaic thermal management

Abstract

Phase change material (PCM) are becoming more desired for passive cooling in various applications, especially in photovoltaic (PV) thermal management. However, several issues arise when integrating PCM with PV panels, such as leakage, PCM container design, tilt angle considerations, and PCM low thermal conductivity, which affects the overall PV thermal management process. To address these issues, a novel sustainable shape-stabilized phase change material (SSPCM) based on oil ash derived from burning oils is used as a carrier for RT-42 PCM. This material aims to improve thermal conductivity, eliminate leakage, tilt angle issues, and the need of PCM container. In this study, the SSPCM was prepared using a two-step vacuum impregnation method, and its thermophysical properties and stability were investigated using various characterization techniques. Results showed that oil ash has a spherical, highly porous structure with particle sizes ranging from 13 µm to 50 µm, enabling effective absorption and distribution of PCM. Different RT-42 PCM loadings within the oil ash were examined, and results indicated that the optimal PCM loading is 40 % of the total weight, leading to a stable material with no signs of leakage. However, exceeding this percentage may result in leakage issues. Moreover, the results confirmed the uniform presence of PCM inside the oil ash with no chemical reactions occurring between the components. The SSPCM exhibited a latent heat of 71.54 J/g and a melting point of 38.1 °C. Additionally, the thermal conductivity of the material increased significantly from 0.19 W/m·K to 0.7352 W/m·K at 45 °C, representing a 287 % enhancement. To ensure the stability of the material and its properties, 100 melting-solidification cycles were performed. Results showed no leakage issues or changes in latent heat and thermal conductivity, confirming the material’s long-term reliability. To evaluate the practical performance of the SSPCM in PV thermal management applications, the temperature of a heat sink base exposed to a 2-watt heat load mimicking a PV panel under solar irradiance was measured and compared with an empty heat sink and a heat sink loaded with RT-42 PCM. Results demonstrated that the developed SSPCM reduced the heat sink temperature by a maximum of 4.7 °C during the heating phase and facilitated faster heat dissipation, with a maximum temperature difference of 4.2 °C compared to an empty heat sink.