Title: Comparative analysis of photovoltaic - thermal (PVT) and photovoltaic (PV) modules

Abstract

Solar photovoltaic and thermal (PVT) is a hybrid technology that combines photovoltaic (PV) solar cells, which converts solar energy into electricity, with a solar thermal collector, which transfers the unused excess heat from the PV module into the useful thermal energy in the form of heated water or air. The hybrid PVT system proves to be more energy efficient with improved electrical efficiency due to cooling of PV cells and obtained thermal energy due to heat absorbed from heated PV cells. Nevertheless, the utilization of these systems does not grow rapidly due to the controversial operational problems. In this work, the operational problems of PVT technology are investigated. The comparative analysis of properties of PVT modules and general PV module has been conducted. The operating temperatures of solar cells in PV and PVT modules under the dependence of ambient temperature and other parameters theoretically and experimentally have been investigated. On the base of comparison of operating temperatures of solar cells in PV and PVT modules, the efficiency of PVT hybrid module has been analyzed. It is demonstrated that when the ambient temperature is low, the temperature of PVT module can be higher than the temperature of the general PV module, due to the decreased convection cooling of PVT in comparison with the PV module. The ambient temperature, below which the PVT module is hotter than the PV module, is called “critical”. As a result of this process, the electrical efficiency of the PVT module becomes smaller than the efficiency of the PV module. This effect is called the “reverse” process. It has been concluded, that to overcome this operational problem, the PVT system and its functionality must be optimized taking into consideration the weather conditions under which the PVT system will be used.