Mirror augmented photovoltaics and time series analytics of the I–V curve parameters

Mirror augmented photovoltaics (MAPV) represents a potentially useful and cost effective path to increasing PV energy harvest. Collection of the full I-V curve enables extraction of information that can provide insights into the degradation phenomena. Because of the transcendental nature of the cell current as a function of voltage, it is not possible to solve in terms of I(V) explicitly, except by means of the Lambert W function. We investigated several techniques for parameterizing the I-V curve to extract the values of R_s and R_sh by developing our own custom models for solar cells and commercial modules using SPICE. Our models allowed for direct I-V curve generation given the input parameters of temperature, integrated irradiance, series and shunt resistance, reverse saturation current and diode ideality factor. Parameter variation in our SPICE model allowed for generation of I-V curves representing possible commercial modules. These digital I-V curves were analyzed as if they were collected from real, fielded modules and subjected to various parameter extraction techniques. Parameters extracted by these various techniques were then compared to the input values to verify accuracy and determine a relative error. We selected a method for accurately extracting values of R_s and R_sh and ideality factor over a range of interest. We will present this method, our current progress in automating this data collection and analysis process as well as the variation over 6 months of the daily values of n, R_s and R_sh for two mirror augmented PV modules.