Modeling of photovoltaic fields in mismatched conditions for energy yield evaluations

In this paper a systematic approach suitable for modeling the behavior of a photovoltaic field operating in both uniform and mismatched conditions is shown. The proposed approach is intended for the evaluation of the long-term energetic performances of photovoltaic fields on a daily, monthly or yearly basis where a fast computation process must be achieved. Two aspects characterize the novel modeling approach: the first one is the evaluation in closed form of the inflection voltage points which represent, in mismatched conditions, the array voltages where the bypass diodes turn off. The second one is the identification of a new set of non-linear equations that describe the photovoltaic field in a simple way, thus speeding up the model solution and the evaluation of the operating voltage and current. The model employs a simple analytical formulation of the photovoltaic field characteristics, allowing a fast evaluation of the energetic performance of different configurations to select the most efficient one in a given irradiance and temperature conditions. The performance of the proposed solution was contrasted with a traditional model obtaining satisfactory results. Finally, numerical examples based on experimental irradiance measurements illustrate the usefulness of the model in the evaluation of photovoltaic field configurations. (C) 2010 Elsevier B.V. All rights reserved.