Evaluating Solar Resource Data Obtained from Multiple Radiometers Deployed at the National Renewable Energy Laboratory

Aron Habte, Manajit Sengupta, Afshin Andreas, Stephen Wilcox, Thomas Stoffel

Research output: NRELPoster


Solar radiation resource measurements from radiometers are used to predict and evaluate the performance of photovoltaic and concentrating solar power systems, validate satellite-based models for estimating solar resources, and advance research in solar forecasting and climate change. This study analyzes the performance of various commercially available radiometers used for measuring global horizontal irradiances (GHI) and direct normal irradiances (DNI). The radiometers in this study were deployed for one year (from April 1, 2011, through March 31, 2012) and compared to measurements from radiometers with the lowest values of estimated measurement uncertainties for producing reference GHI and DNI. The differences were calculated as a percent of reading for solar zenith angles ranging from 17.5 degrees to 85 degrees (the range of available solar zenith angles throughout the year at SRRL, excluding data near sunrise and sunset). Under clear-sky conditions when the solar zenith angle was less than 60 degrees, differences of less than 5% were observed for both GHI and DNI measurements when they were compared to the reference radiometers. These normalized differences increased during partly cloudy sky conditions and when the solar zenith angle was greater than 60 degrees. The intent of this paper is to present a general overview of each radiometer's performance. The National Renewable Energy Laboratory made no effort to ensure that the radiometers presented here were representative units; therefore, this paper does not guarantee the same results for all radiometers from the same manufacturer or model.
Original languageAmerican English
StatePublished - 2014

Publication series

NamePresented at the 2014 European Photovoltaic Solar Energy Conference and Exhibition, 22-26 September 2014, Amsterdam, The Netherlands

NREL Publication Number

  • NREL/PO-5D00-62788


  • DHI
  • diffuse horizontal irradiance
  • direct normal irradiance
  • DNI
  • GHI
  • global horizontal irradiance
  • National Renewable Energy Laboratory (NREL)
  • NREL
  • pyranometers
  • pyrheliometers
  • rotating shadowband irradiometers
  • solar radiation measurements


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