Performance Evaluation of a Photovoltaic/Thermal (PVT) Collector with Numerical Modelling

Abstract: In Photovoltaic/Thermal (PVT) technology, both PV and solar thermal technology are integrated in the same module for simultaneous electricity and heat production. Research has shown that there are multiple benefits from integrating PVT collectors with a ground source heat pump (GSHP) system, since it allows for seasonal storage of thermal energy over the year. Furthermore, it leads to reduced operating temperatures for the PVT collectors which can increase efficiency and lifetime. The aim of this study is to present the electric and thermal performance of a PVT collector developed by Solhybrid i Småland AB, for different environmental and fluid inlet conditions that can occur when PVT collectors are connected to a GSHP system. Furthermore, the performance of this PVT design is evaluated with ASHRAE (Standard 93-2003), to allow for comparison with other PVT collector designs, with values on the overall heat loss coefficient (UL) and heat removal factor (FR). The modelling tool used for the study is the software COMSOL Multiphysics, which uses the finite element method to solve the partial differential equations in heat transfer and fluid flow problems. Based on the performance curves, the thermal and electrical efficiency of the collector is approximately 48.0-53.4% and 19.0-19.2% respectively at a reduced temperature of zero and irradiance levels of 800-1000 W/m2 for the mass flow rate of 0.026 kg/sm2 which was determined as most suitable to increase thermal performance. Furthermore, these results resulted in a heat removal factor (FR) and overall heat loss coefficient (UL) of 0.56-0.62 and 53.4-53.5 W/m2 K respectively. The results on the performance of the PVT collector in different weather conditions shows that the inlet water temperature can significantly affect operating time and the amount of thermal energy that can be extracted during the year, especially if the collector operates in a colder climate like Sweden. To assess the accuracy of the created model, future work includes experimental testing of the studied PVT collector.