Accuracy analysis for fifty-four clear-sky solar radiation models using routine hourly global irradiance measurements in Romania

Fifty-four broadband clear-sky models for computation of global solar irradiance on horizontal surfaces are tested by using measured data from Romania (South-Eastern Europe). The input data to the models consist of surface meteorological data, column integrated data and data derived from satellite measurements. The testing procedure is performed in twenty-one steps for two different sites in Romania. The models accuracy is reported for various sets of input data. No model ranked “the best” for all sets of input data. However, some of the models were ranked among the best for most of the testing steps, and thus performed significantly better than others. These “better” models are, on an equal footing, ESRA3, Ineichen, METSTAT and REST2 (version 8.1). The next “better” models are, on an equal footing, Bird, CEM and Paulescu and Schlett. Details about the accuracy of each model are found in the Electronic Supplementary Content for all testing steps.

► A much larger sample of clear sky models than in any previous study.
► Models are analyzed under identical climate conditions and using a unique testing procedure.
► The models accuracy for various input databases is reported.