Modeling and experimental validation and thermal performance assessment of a sun-tracked and cooled PVT system under low solar irradiation

Abstract

The PV panels cooling allows one to increase the photovoltaic conversion efficiency, as well as to obtain the waste heat, which can be utilized for various purposes. This paper presents the model of the radiator used for photovoltaic (PV) panels cooling. The cooling liquid is a water-glycol mixture, the PV panel electrical power output is 280 W. The radiator consists of a various number of segments (U-tube), that are located at the PV panel width. The three-dimensional control volume method formulation is used to calculate the temperature distribution within the PV panel surface (glass, silica layer, protective foil), and aluminum radiator. The one-dimensional energy equation is used to calculate the cooling liquid outlet temperature. The effect of an increasing number of radiator segments and the mass flow rate is studied to optimize the heat transfer performance and decrease the manufacturing costs. The simulations are conducted for various conditions, including the cloudy and sunny days. The simulation results are compared with experimental data collected at a stand installed at the laboratory of the Department of Energy at the Cracow University of Technology. The measurement results and the numerical simulation shows quite good agreement. For the studied case, it is shown that lowering the temperature of the panels increases the gross efficiency of the entire system. Moreover, the waste heat obtained from the PV cooling may be utilized as low-temperature heat for domestic hot water preheating or heat pump system applications.