Modeling and simulation of a hybrid PV/Thermal collector

The paper presents the simulation and analysis of an hybrid PV/Thermal solar collector, a combination of photovoltaic (PV) and solar thermal systems for the simultaneous production of electricity and heat from one integrated component. It is well known that the efficiency of a photovoltaic solar cell is adversely affected if the panel temperature exceeds the design value (typically, a loss of 0.5% results per degree in excess). This led to the idea of constructing a hybrid solar panel in which a coolant circulating on the bottom side of the photovoltaic cells (their non-irradiated side) allows to lower their operating temperature, thereby increasing both their efficiency and their life. The sensible heat of this coolant can be then recovered by generating domestic hot water or contributing to space heating. The plate-and-tube, water cooled PVT analysed in this work is the one that currently displays the most promising market perspectives. It consists of a glass plate, a photovoltaic panel, a metal plate welded on the backside and thin parallel tubes for the circulation of the cooling fluid. The model presented here is based on macroscopic mass-and energy balances of the individual components of the collector, allowing to calculate its electrical output and the outlet water temperature as a function of local solar irradiation and panel geometry data. The thermodynamic model of the PV/Thermal collector has been implemented in the library of a modular object-oriented Process Simulator, Camel-Pro™ and the exergetic performance of the systems has been analyzed and compared with the performance of photovoltaic and thermal solar panel. A detailed analysis of the exergy destruction at component level is also presented, to better assess the distribution of irreversibilities across the process and to gain useful design insight.