A correct validation of the National Solar Radiation Data Base (NSRDB)

The physical solar model (PSM) data from the National Solar Radiation Data Base offers half-hourly and hourly satellite-derived irradiance data on a regular 0.04°×0.04° grid over most of America, from 1998 to 2016. Previously in “The National Solar Radiation Data Base (NSRDB)” [Renewable & Sustainable Energy Reviews 89 (2018) 51-60] and “Evaluation of the National Solar Radiation Database (NSRDB): 1998-2015” [National Renewable Energy Laboratory technical report NREL/TP-5D00-67722], the accuracy of the PSM data is validated against the ground data from the SURFRAD network. Unfortunately, those validations appear to be incorrect, most likely due to a data-aggregation issue. Whereas the PSM data is valuable for solar system design, simulation and evaluation, the high data uncertainty reported limits the confidence in using the dataset. The validation of the PSM data is herein reiterated. It is found that the actual uncertainty is much lower than those reported earlier.