No abstract

As solar energy costs continue to drop, the number of large-scale deployment projects increases, and the need for different analysis models for photovoltaic (PV) modules in both academia and industry rises. This paper proposes a modified equivalent-circuit model for PV modules. A PV module comprises several series-connected PV cells, to generate more electrical power, where each PV cell has an internal shunt resistance. Our proposed model simplifies the standard one-diode equivalent-circuit (SEC) model by removing the shunt resistance and including its effect on the diode part of the circuit, while retaining the original model accuracy. Our proposed equivalent circuit, called here a modified SEC (MSEC), has less number of circuit elements. All of the PV cells are assumed operating under the same ambient conditions where they share the same electric voltage and current values. To ensure the simplification did not come at a reduction in the accuracy of the SEC model, we validate our MSEC model by simulating both under the same conditions, calculate, and compare their current/voltage (I/V) characteristics. Our results validate the accuracy of our model with the difference between the two models falling below 1%. Therefore, the proposed model can be adopted as an alternative representation of the equivalent circuit for PV cells and modules.

This paper presents a closed form for the behavior of the ideality factor n of amorphous silicon (a-Si:H) photovoltaic cells under different illumination intensity U levels and applied voltage V. The advantage of this model, over other existing models, is its effectiveness of describing the dependency of n on both V and U even without evaluating n itself. Therefore, the errors of calculating n using various existing methods are minimized in this paper. The variations of the current voltage J/V data under different levels of U are monitored where the illumination intensity dependence of parallel resistance R p (U) is taken into account. The resulting model is a first order differential equation with non-constant coefficients whose solution expresses the variations of n in V-and U-domain. From the solution of the differential equation, it is found that n increases as V or U increases. V C 2015 AIP Publishing LLC.