Reflector-Augmented Photovoltaic Power Output Incorporating Temperature-Dependent Photovoltaic Efficiency

The power output produced by Photovoltaic (PV) panels depends on the quantity of solar energy incident on the PV surface, the surface area of the module and the efficiency of the system which is a function of the module’s surface temperature. Concentration of solar irradiation onto a PV surface augments the solar energy flux on the module surface as has been shown by published literature. However, concentrated solar irradiation increases the PV surface temperature, decreasing the efficiency of the module. In this work, the influence of temperature-dependent module efficiency on the power extracted from a reflector-augmented Photovoltaic (PV) module is explored. A reflector-collector system is considered theoretically having a variable angle between the reflector and collector as well as a variable angle between the reflector and the horizontal axis. The hourly solar radiation incident on the PV module and the reflector are obtained using TMY3 data. The total solar radiation (direct and reflected components) striking the collector is calculated on an hourly basis which is in turn used to determine the temperature of the PV module. The electrical power produced on an hourly basis is then calculated. In order to determine the influence of a reflector on system behavior, this study determines the electrical power produced by the system for two separate cases: direct solar irradiation only (beam and diffuse) incident on the collector as well as direct and reflected (beam and diffuse) solar irradiation incident on the collector.[MRB1]  For both cases specified above, four separate geometric arrangements are evaluated, being different combinations of reflector-collector angle as well as reflector-horizontal angle. Finally, the power produced by the solar panel is determined using temperature-dependent efficiency as well as temperature-independent efficiency in order to determine the influence of temperature on the final power output. Results indicate that the output power of a PV module with temperature-dependent efficiency is less than the output power of the same PV module having a constant efficiency for both direct and direct/reflected cases and for all tested panel-reflector geometry arrangements. The monthly average increase in power produced with a reflector as opposed to without a reflector follows a similar trend when temperature-dependent and temperature-independent efficiencies are considered. The addition of a reflector has a greater influence on output power during cold winter months as opposed to hot summer months. Likewise, certain geometric conditions experience the least benefit from adding a reflector during the spring and fall seasons. Panels modeled with a temperature-independent efficiency consistently produced greater power than panels modeled as having a temperature-dependent efficiency. The existence of a reflector was most advantageous when the PV panel was positioned horizontally and the reflector was positioned perpendicular to the ground, giving an increase of 35% in power for temperature-independent efficiency and an increase of 26% in power for temperature-dependent efficiency, with these peaks occurring in the summer for temperature-independent systems and in the winter for temperature-dependent systems.