On-site BIPV array shading evaluation tool using stereo-fisheye photographs

It is difficult to estimate precisely total irradiance on photovoltaic (PV) arrays without consideration of the effect of shadow by surroundings, especially for building integrated photovoltaic (BIPV) systems in an urban area. The accurate evaluation of actual irradiation on the arrays may contribute to the verification of the performance of PV systems. In this research, the authors propose the method of calculating the shading factor by applying the photo survey method using fisheye photographs to capture whole surroundings. The shading factor is defined as the ratio of actual irradiation on PV arrays to ideal irradiation with no shading modules. Actual irradiation on a certain array can be calculated easily by using the shading factor.