Self-shading losses of fixed free-standing PV arrays

The energy yield of a photovoltaic (PV) system with fixed free-standing PV arrays is affected also by the self-shading effects. The rows of PV modules in arrays may partially shade the PV modules in the rows behind. In this paper the effects of the row distance on the PV system's energy yield are evaluated. The estimation of the self-shading losses by the irradiation losses simply overestimates the losses; therefore we developed a simulation model to simulate the real energy loss due to shading of the preceding row in a PV system. The model demonstrates that the self-shading energy losses are at commonly used distances between rows from 20 to 40% lower than the irradiation losses at the modules' bottom considering the shading conditions. The self-shading energy loss is studied in the case of Ljubljana, Slovenia which may refer to the whole Central Europe. To estimate the self-shading losses a technology- and with parameter modifications also location-independent empirical equation based on module-to-cell width ratio was derived and validated. (c) 2011 Elsevier Ltd. All rights reserved.