Energy and thermo- fluid - dynamics evaluations of photovoltaic panels cooled by water and air

The main limit of photovoltaic (PV) systems is the low conversion efficiency of cells, that is strongly influenced by their operating temperature. As the temperature increases the short circuit current (Isc) increases moderately, while the open circuit voltage (Voc) decreases considerably. The cell temperature reduction is a methodology that could be used in order to improve the PV panels performance both new and already installed as well. In accordance with the maximum producibility that occurs when the radiation is powerful, therefore the cell temperature is great, this solution becomes interesting. Furthermore this solution is an alternative to PVT (Thermal - Photovoltaic) systems in which the water flow needs to be cooled during the maximum solar radiation hours with the purpose of not worsen the performance of panels. The purpose of this work is to evaluate the performance of different cooling systems. Various solutions that adopt respectively a cooling water system and an airflow lapping the back of the panels in an open circuit will be investigated to individuate the best cooling solution. A finite element software that describes in a detailed manner the thermal exchange between PV cells, the external environment and the cooling system will be used in order to assess the reached temperature of the cells with different cooling system configurations calculating for each considered configurations the top loss coefficient. Regarding the air cooling system configuration, that results less invasive, it is also forecasted a comparison between the simulated and the measured in laboratory air speed. Energy hourly simulations using the software TRNSYS will be carried out on the best identified configurations to evaluate the annual performances.