Comparison of Predicted PV System Performance with SURFRAD versus TMY

Solar resource is important for predicting PV system performance. Historical Typical Meteorological Years (TMY) from 1960-1990 (TMY2) and 1990-2010 (TMY3) are commonly used in the United States, but recently there have been concerns by stakeholders whether these datasets may lead to overpredictions. Therefore we simulated performance of a fictional PV system with over 20-years of accurate ground based surface radiation (SURFRAD) measurements at 7 locations and compared the median year performance with simulations using TMY data. We found that TMY overpredicted the median SURFRAD performance at 5 of the 7 sites, the NREL Physical Solar Model V3 (PSM3) performance predictions were greater than 90% of SURFRAD years at 5 of the 7 sites, and TMY3 predictions were closest on average to the median. Both TMY2 and TMY3 were within their uncertainty range.