Simplified model to correct thermopile pyranometer solar radiation measurements for photovoltaic module yield estimation

Abstract

This article presents and evaluates the performance of a simplified model to generate 10-min global horizontal synthetic solar radiation data that would correspond to the measurements of a calibrated photovoltaic monocrystalline cell. The model, which only requires global horizontal solar radiation data measured with a thermopile pyranometer as input, is based on the characterization of the relation between the data measured with a thermopile pyranometer and a calibrated cell as a function of the sky condition and the solar elevation. We have used an extensive solar radiation database for the location of Seville (Spain) for the training of the model that has been tested in Seville and Lancaster (USA), showing satisfactory results and suggesting a global applicability with no local adaptation or calibration requirement.The model shows the best results for high levels of solar radiation and solar elevations and decreases its performance on days with high levels of diffuse irradiation and for very low solar elevation angles. We obtain a daily RMSD between measured and synthetic data of 1.9% in Seville and 5.2% in Lancaster. The frequency distribution of the synthetic datasets shows a KSI of 3.7 W/m2 in Seville and 8.6 W/m2 in Lancaster. We also evaluate the ramp rates of measured and synthetic sets through the KSI of the measured and synthetic ramp rates sets, obtaining 0.11 W/m2۰min in Seville and 0.20 W/m2۰min in Lancaster.