Self-shadow analysis of bifacial solar photovoltaic and its implication on view factor computation

Abstract

A solar photovoltaic (PV) module is subject to self-shadow on the ground, requiring careful consideration during PV system design. The effect of self-shadow is more prominent for bifacial PV where a significant energy gain can be achieved from reflected radiation at the rear side. The self-shaded area blocks the global horizontal radiation underneath the module. It creates a variation between view factor from the shaded and non-shaded regions and causes non-uniformity of the reflected radiation which the module receives at the rear side. This reflected radiation depends on the view factor from solar PV to the ground. Therefore, to compute the reflected radiation at the rear side accurately, it is important to determine the view factor to the shaded and non-shaded regions separately.The unique contribution of this work is it applies the view factor computation model developed by the authors to compute view factor to the shaded and non-shaded ground. This paper applies a shadow projection algorithm to determine the coordinates of shadow on the available ground. Here, the view factor is computed at different ground clearance height (GCH) and tilt angle of the PV module. It is found with the increase of height; the effect of self-shading diminishes and the view factor to non-shaded region increases in comparison to the shaded region. However, beyond the ground clearance height of 1m and tilt angle of 45°, the view factor decreases significantly. Results are analysed on different days of the month. Finally using, Solaris Prospect data, the reflected irradiance at the rear side of the module is computed.