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Title: Measuring Broadband IR Irradiance in the Direct Solar Beam (Presentation)

Solar and atmospheric science radiometers, e.g. pyranometers, pyrheliometers, and photovoltaic cells are calibrated with traceability to a consensus reference, which is maintained by Absolute Cavity Radiometers (ACRs). The ACR is an open cavity with no window, developed to measure extended broadband direct solar irradiance beyond the ultraviolet and infrared bands below and above 0.2 um and 50 um, respectively. On the other hand, pyranometers and pyrheliometers are developed to measure broadband shortwave irradiance from approximately 0.3 um to 3 um, while the present photovoltaic cells are limited to approximately 0.3 um to 1 um. The broadband mismatch of ACR versus such radiometers causes discrepancy in radiometers' calibration methods that has not been discussed or addressed in the solar and atmospheric science literature. Pyrgeometers are also used for solar and atmospheric science applications and are calibrated with traceability to consensus reference, yet are calibrated during nighttime only, because no consensus reference has yet been established for the daytime longwave irradiance. This poster shows a method to measure the broadband IR irradiance in the direct solar beam from 3 um to 50 um, as a first step that might be used to help develop calibration methods to address the mismatch between broadbandmore » ACR and shortwave radiometers, and the lack of a daytime reference for pyrgeometers. The irradiance was measured from sunrise to sunset for 5 days when the sun disk was cloudless; the irradiance varied from approximately 1 Wm-2 to 16 Wm-2 for solar zenith angle from 80 degrees to 16 degrees respectively; estimated uncertainty is 1.5 Wm-2.« less
Authors:
Publication Date:
OSTI Identifier:
1176751
Report Number(s):
NREL/PR-B310-63830
DOE Contract Number:
AC36-08GO28308
Resource Type:
Conference
Resource Relation:
Conference: Presented at the 2015 ARM/ASR Joint User Facility PI Meeting, 16-20 March 2015, Vienna, Virginia; Related Information: NREL(National Renewable Energy Laboratory)
Research Org:
National Renewable Energy Laboratory (NREL), Golden, CO.
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy Solar Energy Technologies Office
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; 14 SOLAR ENERGY; PYRANOMETERS; PYRHELIOMETERS; CALIBRATION IR IRRADIANCE IN SOLAR BEAM; PYRANOMETER; PYRHELIOMETER; PYRGEOMETER; CALIBRATION