ELECTRICAL AND THERMAL PERFORMANCE OF PHOTOVOLTAIC-THERMAL MODULE (PVT) UNDER DIFFERENT SKY CONDITIONS

Abstract

Solar energy is a renewable energy option that is capable of providing both electricity and heat. To take the most of the available solar energy, a photovoltaic (PV) module is converted into a photovoltaic-thermal (PVT) module by installing a polypropylene (PP) heat exchanger. The aim is to verify the performance of a PVT module, on clear and cloudy sky days, using water to cool the PV cells and use it heated for other purposes. The test bench has one PVT module near one PV module for comparing their energy performance with data collected between 11:00 and 13:00 hours. The root mean square (RMS) of solar irradiance on a tilted surface on a clear day (Day 1) is 857 W/m² and on a cloudy day (Day 2) is 459 W/m². On Day 1, the difference between inlet and outlet water temperatures is about 0.7 °C greater than the temperature difference on Day 2. Thus, the highest solar irradiation produces a maximum thermal power of 980 W on Day 1, while on Day 2, 735 W. However, the PP heat exchanger has an average thermal efficiency with similar RMS values, independently of sky conditions. In turn, electrical efficiency strongly depends on weather conditions, as both solar irradiance and ambient temperature influence PV operating temperature. On Day 1, due to the higher irradiance in the analyzed period, the electrical efficiency is lower than the efficiency of Day 2, because the PVT module presents a higher temperature on Day 1 compared to Day 2. The greater energy advantage of the PVT module compared to PV is due to its higher electrical performance as well as thermal performance on clear and cloudy days.