Influence of series and shunt resistances in the ideality factor of photovoltaic modules

The ideality factor is a parameter that greatly influences the current / voltage curve of a photovoltaic (PV) module. Although some authors consider it constant during the analysis of the module operation, the ideality factor tends to be lowered with time, deteriorating the power output of the PV module. The ideality factor is modified by the increase of the shunt resistance and, particularly, with the series resistance variation. It is affected by several climate factors, which cause the corrosion of the PV module cells, manufacturing errors and defects known as “hot spots”. In this paper, the analysis of the ideality factor and the effects of series and shunt resistances in its value will be evaluated, as well as the influence in the I×V curve of the PV module.