Numerical model and parametric analysis of a liquid based hybrid photovoltaic thermal (PVT) collector

Abstract A hybrid photovoltaic thermal (PVT) panel is a module in which the photovoltaic (PV) layer is not only producing electricity, but also operates as a thermal absorber. As a result, thermal and electrical energy are being produced simultaneously, operating as a micro-cogeneration equipment. As in any cogeneration system, there is tight link between the electrical and thermal performance and it is dependent on multiple parameters: climate conditions, thermo-physical, geometrical and electrical properties. This paper investigates the effect of the variation of several of these parameters on the electrical and thermal performance, as well as on the global output. In order to achieve this, a dynamic numerical model is proposed, which simulates the heat exchange between the layers of the PVT panel. The model was applied to two different climatic conditions: Bucharest, Romania and Strasbourg, France, in order to assess and compare their behavior and performance. The simulation computes the temperature of each layer at any particular time, and a slightly higher outlet temperature of the working fluid can be observed in Bucharest during the summer, and in Strasbourg during the winter. The model is validated against data from the literature and can be applied to any climatic conditions and adapted for multiple geometrical and thermo-physical configuration. Next, a one-factor-at-a-time parametric analysis is carried out in order to assess the impact of various parameters on the electrical, thermal and global efficiency. The results showed in most cases a compromise between the electrical and thermal performance: in terms of wind speed and insulation, the thermal benefits of low wind and high insulation overcome the decrease in electrical efficiency. The packing factor was found to be optimum when maximized, as the electrical benefits are more significant than the thermal loss. The width of the channels in the heat exchanger should also be maximized as far as technologically possible for best performance.