THE RELATION BETWEEN PARTIAL SHADINGS AND IRRADIATION LOSSES IN BIPV SYSTEMS IN DIFFERENT LOCATIONS AROUND THE WORLD

摘要

Partial shadings are a common situation in urban PV systems, especially BIPV systems. With the increasing number of this type of installations, it is important to understand the relation between the shaded area and its corresponding irradiation losses. This research is focused on the application and evaluation of a simplified method for energy losses analysis caused by partial shadings previously presented elsewhere, now in a greater number of cases, thus broadening the scope of previous work. The original method was based on computational simulations using the Ecotect software for two horizontal surfaces in two locations: Florianopolis (27.48°S) and Singapore (1.04°N), comparing in different time basis (hourly, daily, monthly and annually) the shading percentage and the percentage of irradiation reduction. In the present research, a new 3D model was designed, with five surfaces (rooftops) with different tilt angles and azimuthal deviations. The 3D model was simulated using the same software in 10 cities located in different latitudes, covering, therefore, a representative mesh of cases around the world. Results have shown that this method is more useful to quantify irradiation losses caused by shadings on rooftops more ideally oriented because, in these cases, values of annual shading percentage and percentage of incident radiation reduction tend to be coincident. These results simplify future shading losses analysis for similar cases, demonstrating that a simple annual shading analysis would already reflect possible losses in the power generation of a partially shaded PV system. So, this method can be used even before the PV system is electrically designed; instead, it can be used as a first tool to decide where to install BIPV systems and what the energetic consequences of each decision are.