The Impact of Indoor and Outdoor Radiometer Calibration on Solar Measurements: Preprint

Research output: Contribution to conferencePaper


Accurate solar radiation data sets are critical to reducing the expenses associated with mitigating performance risk for solar energy conversion systems, and they help utility planners and grid system operators understand the impacts of solar resource variability. The accuracy of solar radiation measured by radiometers depends on the instrument performance specification, installation method, calibration procedure, measurement conditions, maintenance practices, location, and environmental conditions. This study addresses the effect of calibration methodologies and the resulting calibration responsivities provided by radiometric calibration service providers such as the National Renewable Energy Laboratory (NREL) and manufacturers of radiometers. Some of these radiometers are calibrated indoors, and some are calibrated outdoors. To establish or understand the differences in calibration methodology, we processed and analyzed field-measured data from these radiometers. This study investigates calibration responsivities provided by NREL's broadband outdoor radiometer calibration (BORCAL) and a few prominent manufacturers. The reference radiometer calibrations are traceable to the World Radiometric Reference. These different methods of calibration demonstrated 1% to 2% differences in solar irradiance measurement. Analyzing these values will ultimately assist in determining the uncertainties of the radiometer data and will assist in developing consensus on a standard for calibration.
Original languageAmerican English
Number of pages7
StatePublished - 2016
EventEuropean PV Solar Conference and Exhibition (EU PVSEC) - Munich, Germany
Duration: 20 Jun 201624 Jun 2016


ConferenceEuropean PV Solar Conference and Exhibition (EU PVSEC)
CityMunich, Germany

NREL Publication Number

  • NREL/CP-5D00-66659


  • diffuse global irradiance
  • direct normal irradiance
  • global horizontal irradiance
  • measurement uncertainty
  • photodiode
  • pyranometer
  • pyrheliometers
  • radiometer calibration
  • responsivity
  • thermopile


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