Parameters identification of the single-diode model for amorphous photovoltaic panels

The single-diode model, which is widely used for describing the behaviour of the photovoltaic crystalline and multi-crystalline cells, requires to be properly adapted for reproducing the electrical behaviour of amorphous thin film silicon cells. As for the former case, five parameters must be identified for having a good fitting with respect to the experimental measurements or the data reported in the module data sheet. Nevertheless, due to the strong nonlinearity of the model, the fitting procedures suffer from convergency problems and are sensible to the initial guess solution. In this paper a set of explicit equations is developed in order to calculate the approximated values of the five parameters characterising the PV model. These equation have been obtained by extending, to the amorphous case, the procedure already developed for the crystalline single diode model, thus by generalising and reinforcing the validity of that approach. The new formulas have been validated by comparing the results of the proposed approach with the experimental values reported in the data sheet of some amorphous silicon panels.