| Description |
1 online resource (vii, 60 pages) : color illustrations. |
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text txt rdacontent |
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computer c rdamedia |
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online resource cr rdacarrier |
| Series |
NREL/SR ; 5D00-80437 |
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NREL/SR ; 5D00-80437.
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| Note |
"September 2021." |
| Bibliography |
Includes bibliographical references (page 23). |
| Type Of Report |
Subcontract report. |
| Funding |
DE-AC36-08GO28308 |
| Note |
Description based on online resource; title from PDF title page (NREL, viewed May 4, 2022). |
| Summary |
Reference cells are widely used in the photovoltaic (PV) industry to measure irradiance. For field applications and outdoor use, a variety of products are on the market, and they are often perceived as a low-cost alternative to thermopile radiometers. But reference cell characteristics differ substantially from the latter, therefore measurements made by one category of instrument cannot be substituted for or directly compared with the other. The National Renewable Energy Laboratory's (NREL's) Solar Radiation Research Laboratory is currently in a multiyear effort to develop guidance and recommendations for the design and use of outdoor reference cells, with a view to reducing inconsistencies and measurement uncertainty. The core of this effort is the long-term deployment of 39 units of 10 distinct types made by 6 manufacturers. This report compares the calibration factors provided by manufacturers - which most users rely upon - to those measured at a high level of accuracy by NREL's Cell Lab. It also reports on the application of the Broadband Outdoor Radiometer Calibration (BORCAL) method to reference cells. As a group, the factory calibrations for the crystalline silicon cells showed a small positive bias of +0.7%, with a tight distribution around this value. This is a very good result for the manufacturers. The two World Photovoltaic Scale cells constituted outliers, with a mean deviation of -0.8%, which is still within the reported uncertainty ranges. The data collected during the BORCAL procedures show a strong and systematic fluctuation of the apparent responsivity of the reference cells over the course of a day, which was anticipated. Consequently, the standard BORCAL R@45 calibration factors underestimated the reference cell responsivities by 1%-4%. An alternate responsivity indicator was developed, R'@30, incorporating adjustments for temperature response, spectral response, and directional response. This reduced the mean deviation to -0.4% compared to the Cell Lab. Further, two independent BORCAL sessions were able to produce the same values to within 0.2%. This could be a viable approach for verifying reference cells using existing BORCAL infrastructure, for example, to evaluate their long-term stability. The daily profiles of responsivity obtained during the BORCAL sessions (provided in Appendix A) show clear patterns of differences between models, which provides evidence that their directional responses differ from each other; thus, two sensors that are calibrated correctly might give the same reading at 30° zenith angle but systematically different readings at 60°. The impact of these inconsistencies in field operation will be quantified using the long-term observations started in 2020. |
| Subject |
Photovoltaic cells -- Calibration -- United States.
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Pyranometer -- Calibration.
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Cellules photovoltaïques -- Étalonnage -- États-Unis.
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Pyranomètres -- Étalonnage.
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Pyranometer -- Calibration
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United States https://id.oclc.org/worldcat/entity/E39PBJtxgQXMWqmjMjjwXRHgrq
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| Indexed Term |
BORCAL |
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broadband outdoor radiometer calibration |
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calibration |
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photovoltaic |
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PV |
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reference cell |
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solar resource assessment |
| Added Author |
Gotseff, Peter, author.
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Sengupta, Manajit, author.
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National Renewable Energy Laboratory (U.S.), issuing body.
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United States. Department of Energy. Solar Energy Technologies Office, sponsoring body.
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| Added Title |
Photovoltaic reference cells for outdoor use |
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Investigation of calibration factors |
| Standard No. |
1823768 OSTI ID |
| Report No. |
DOE/GO-102021-5599 |
| Gpo Item No. |
0430-P-05 (online) |
| Sudoc No. |
E 9.18:NREL/SR-5 D 00-80437 |
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