Performance Evaluation of a Hybrid PVT-ST System under the Influence of Dual Water Flows and a Single Airflow Velocity

Abstract

Solar thermal (ST) collectors are an efficient technology for generating thermal energy without the need for an electrical source, unlike photovoltaic thermal (PVT) collectors, which combine photovoltaic and thermal conversion to produce electricity and low-grade thermal energy. This research aims to present a low-cost strategy for improving the dual performance of PVT and ST systems by connecting them in series, under operating conditions that include different water flow rates and constant air flow in the ST unit. This work evaluates the thermal and electrical performance of a hybrid (PVT-ST) system, focusing on the effect of incorporating porous media and phase change materials (PCMs) into the system design. The results demonstrate that the integrated system enhances the heating efficiency of both water and air, contributing to an increase in the overall energy production efficiency. Experimental data showed that decreasing the water flow rate increased temperatures, while increasing the flow reduced temperature fluctuations and improved thermal production. The highest water temperature difference in the PVT system was recorded at 15.9°C at the lowest water flow, and the highest outlet air temperature was 58.5°C under the same conditions. The PVT-ST system's maximum total thermal power output was 756.13 W, achieving an overall thermal efficiency of 110.6%, an electrical efficiency of 12.22%, and a maximum electrical output of 142.69 W. The integration of thermal energy storage technologies enhances the stability of the system's performance, especially during periods of low solar radiation. The use of porous media improves internal heat transfer and distribution, while phase change materials help store and gradually release thermal energy, reducing temperature fluctuations and enhancing the stability and efficiency of the thermal and electrical systems