Recent Progress in Reducing the Uncertainty in and Improving Pyranometer Calibrations

The Measurements and Instrumentation Team within the Distributed Energy Resources Center at the National Renewable Energy Laboratory, NREL, calibrates pyranometers for outdoor testing solar energy conversion systems. The team also supports climate change research programs. These activities led NREL to improve pyranometer calibrations. Low thermal-offset radiometers measuring the sky diffuse component of the reference solar irradiance removes bias errors on the order of 20 Watts per square meter (W/m 2 ) in the calibration reference irradiance. Zenith angle dependent corrections to responsivities of pyranometers removes 15 to 30 W/m 2 bias errors from field measurements. Detailed uncertainty analysis of our outdoor calibration process shows a 20% reduction in the uncertainty in the responsivity of pyranometers. These improvements affect photovoltaic module and array performance characterization, assessment of solar resources for design, sizing, and deployment of solar renewable energy systems, and ground-based validation of satellite-derived solar radiation fluxes.

[1]  J. Kendall,et al.  Two blackbody radiometers of high accuracy. , 1970, Applied optics.

[2]  Daryl R. Myers,et al.  Uncertainty estimates for global solar irradiance measurements used to evaluate PV device performance , 1989 .

[3]  G. A. Zerlaut,et al.  Solar radiometry instrumentation, calibration techniques, and standards , 1986 .

[4]  M. Iqbal.  An introduction to solar radiation , 1983 .

[5]  Ibrahim Reda,et al.  Measurement of Broadband Diffuse Solar Irradiance Using Current Commercial Instrumentation with a Correction for Thermal Offset Errors , 2001 .

[6]  Arild Gulbrandsen,et al.  On the Use of Pyranometers in the Study of Spectral Solar Radiation and Atmospheric Aerosols , 1978 .

[7]  Richard Perez,et al.  Design and development of a rotating shadowband radiometer solar radiation/daylight network , 1988 .

[8]  T. Stoffel,et al.  Results of NREL Pyrheliometer Comparisons (NPC1999), October 4-10, 1999, Golden, Colorado , 2000 .

[9]  J. Michalsky.  The Astronomical Almanac's algorithm for approximate solar position (1950 - 2050). , 1988 .

[10]  I. Reda.  Calibration of a Solar Absolute Cavity Radiometer with Traceability to the World Radiometric Reference , 1996 .

[11]  P. Ineichen,et al.  Equivalence of pyrheliometric and monochromatic aerosol optical depths at a single key wavelength. , 1998, Applied optics.

[12]  I. Reda,et al.  Calculating the Diffuse Responsivity of Solar Pyranometers , 1999 .

[13]  Daryl R. Myers,et al.  Current Issues in Terrestrial Solar Radiation Instrumentation for Energy, Climate and Space Applications Preprint prepared for New RAD '99 , 1999 .

[14]  Barry N. Taylor,et al.  Guidelines for Evaluating and Expressing the Uncertainty of Nist Measurement Results , 2017 .

[15]  R. Willson,et al.  Active cavity radiometer. , 1973, Applied optics.