Uncertainty analysis of degradation parameters estimated in long-term monitoring of photovoltaic plants

This paper deals with the uncertainty analysis of parameters estimated during long-term monitoring of photovoltaic plants. A specifically developed data-acquisition system is briefly described, which has been conceived to be easily calibrated and, if necessary, adjusted to compensate for measuring-chain drifts, in order to assure the traceability of the estimated parameters. The measurement capabilities of the acquisition system are reported in terms of measured quantities and expected uncertainty. Results that refer to a three-year monitoring of ten photovoltaic plants based on different technologies and architectures are reported. The obtained uncertainty is suitable to distinguish the behavior of the different plants, thus allowing a preliminary comparison to be performed among technologies and architectures. Experimental results highlight an important difference between crystalline silicon devices and thin film technologies in regards to degradation.