Pyrgeometer Calibration at the National Renewable Energy Laboratory (NREL)

Ibrahim Reda, John R. Hickey, Tom Stoffel, Daryl Myers

    Research output: Contribution to journalArticlepeer-review

    27 Scopus Citations

    Abstract

    Pyrgeometers are used to measure longwave terrestrial radiation. Regular pyrgeometer calibration against an internationally recognized standard is required in order to measure the longwave radiation consistently at different sites around the globe. At present, there is no internationally recognized standard to calibrate pyrgeometers. A well-characterized blackbody is, however, an accepted approach. This paper describes a method of establishing a precise blackbody reference and using it to calibrate a group of four transfer reference pyrgeometers. The group is then deployed outdoors to evaluate the precision of the blackbody calibration. The results from the outdoor data shows that the percentage mean-square-error of each transfer reference pyrgeometer is 0.12%, 0.07%, 0.46%, and 0.10% with a resultant percentage root-mean-square of 0.43%. The errors are calculated with respect to the average of the irradiance readings of the transfer reference pyrgeometers. To minimize the number of transfer reference pyrgeometers and to allow more space for calibrating test pyrgeometers, a sub-set of the transfer reference pyrgeometers is then used to calibrate a test pyrgeometer outdoors. The calibration of the test pyrgeometer resulted in reducing its error from +4.00% to ±0.32% with respect to the irradiance measured by the sub-set of the transfer reference pyrgeometers. The outdoor calibration method can minimize the calibration cost resulting from using the lengthy and costly blackbody calibration because many pyrgeometers can be calibrated at the same time. Appendix A shows a diagram that describes the paper's concept.

    Original languageAmerican English
    Pages (from-to)1623-1629
    Number of pages7
    JournalJournal of Atmospheric and Solar-Terrestrial Physics
    Volume64
    Issue number15
    DOIs
    StatePublished - 2002

    NREL Publication Number

    • NREL/JA-560-30096

    Keywords

    • Blackbody
    • Calibration
    • Longwave
    • Outdoor
    • Pyrgeometer
    • Terrestrial

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