ENERGY RATING OF PV MODULES BASED ON PVGIS IRRADIANCE AND TEMPERATURE DATABASE

ABSTRACT: A method for estimating the performance of PV modules over large geographical regions has previously been presented. The performance is based on solar radiation and temperature geospatial data that are modeled in a geographical information system (PVGIS), and a relation for the conversion efficiency of crystalline silicon PV modules at varying irradiance and temperature to obtain values for the loss of efficiency at any location. Using this system, predictions of performance of crystalline silicon have been made at different locations around Europe. In order to evaluate the accuracy of these predictions, a study has been made of the algorithm used to calculate daily variations of both irradiance and temperature from the monthly means contained in the geographical information system. The algorithm uses calculated sun position and airmass, combined with an estimated clear sky index to obtain instantaneous in-plane global irradiance. Instantaneous ambient temperatures are calculated from the average daily temperature from a model of daily temperature variation. To perform the evaluation, the real outdoor measured performance of a poly-crystalline module measured over a 12 month period at Ispra, north Italy, was compared with the estimated performance based on the algorithm. In order to avoid having to compare a specific year with the 10-year averages contained in the database, monthly averages from locally measured irradiance and temperature data were calculated and used by the algorithm. In this way, the algorithm was studied on a comparable dataset, and over the year in question, the predicted and measured energy production come within approximately 5 %, indicating that the method is sufficiently accurate for PV performance estimation