Hexagonal Boron Nitride-based Nano-phase Change Materials Integrated with Water Coolants in Photovoltaic Thermal Systems

This study investigates the effect of hexagonal boron nitride (hBN)-enhanced nano-phase change material (nPCM) combined with active water cooling on the thermophysical properties of paraffin and the performance of a photovoltaic thermal system. Paraffin-based nPCM was prepared with hBN mass fractions of 0.5%, 1.0%, and 2.0%, and experimentally evaluated under coolant flow rates of 5, 10, and 15 mL/s. The materials were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermal property measurements. The results confirmed that hBN interacted physically with paraffin without forming new chemical compounds. Increasing hBN concentration increased density and thermal conductivity, with the 2% hBN formulation showing the highest density (847.2 kg/m³) and thermal conductivity (0.191 W/m·°C), compared with 820 kg/m³ and 0.18 W/m·°C for pure paraffin. However, latent heat decreased from 224.63 to 216.45 kJ/kg as the hBN loading increased. In the photovoltaic thermal (PVT) application, all PVT/nPCM configurations outperformed the uncooled photovoltaic module and the conventional PVT/PCM system by reducing cell temperature and improving electrical efficiency. The best performance was achieved by the PVT/nPCM system with 2% hBN at a coolant flow rate of 15 mL/s, which reduced the peak cell temperature to 42.7 °C and delivered the highest electrical efficiency of 25.34%. These findings demonstrate that hBN/paraffin nPCM combined with active water cooling is a promising thermal management strategy for improving PVT efficiency and stability.