Optimizing Photovoltaic-Thermal (PVT) System Performance with LiNO3-NaNO3-NaCl/Sands-based Phase Change Materials

Solar energy is a prominent renewable energy source, with photovoltaic (PV) systems offering sustainable solutions. However, the efficiency of PV panels declines with rising temperatures. This study tackles this limitation by integrating a hybrid composite phase change material (CPCM) made of LiNO3-NaNO3-NaCl and sand (8:2 ratio) with a PV system for real-time thermal energy storage. Heat capture is facilitated by a 12.7 mm copper pipe beneath the PV panel, with water circulating at 2.4 L/min. The thermophysical properties of the CPCM were analyzed using X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), focusing on phase transitions and melting-solidification behavior. Results showed an 8°C reduction in PV panel temperature, increasing power output from 22.3 W (standard panel) to 24.8 W. The CPCM achieved a thermal energy storage capacity of 30 kJ and a maximum temperature of 63.6°C. This enhanced the electrical efficiency of the PV system by 1.2%, yielding an overall efficiency of 12%, while thermal efficiency reached 70%. The exergy efficiency also improved by 1.5%, achieving 9.2% compared to the standard panel. These findings underscore the CPCM's potential to enhance the performance of PV systems by simultaneously improving thermal management and energy efficiency.