Developing a Framework for Reference Cell Standards for PV Resource Applications

Habte, Aron; Sengupta, Manajit; Xie, Yu; Dooraghi, Mike; Reda, Ibrahim; Diresse, Anton; Gueymard, Christian A.; Wilbert, Stefan; Vignola, Frank

doi:10.2172/1487333

Cited by 5 publications

(2 citation statements)

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“…Although complete knowledge of PV reference cell characteristics is desirable, it is not always practical to acquire and use it, even if it is available. Parallel and complementary efforts are underway to promote increased homogeneity and further standardization (Habte et al 2018). Future editions of this handbook will expand on these and other topics related to PV reference cells.…”

Section: Recent and Ongoing Researchmentioning

confidence: 99%

Best Practices Handbook for the Collection and Use of Solar Resource Data for Solar Energy Applications: Third Edition

Sengupta

Habte

Wilbert

et al. 2021

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Section: Recent and Ongoing Researchmentioning

confidence: 99%

Best Practices Handbook for the Collection and Use of Solar Resource Data for Solar Energy Applications: Third Edition

Sengupta

Habte

Wilbert

et al. 2021

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“…The National Renewable Energy Laboratory's (NREL's) Solar Radiation Research Laboratory (SRRL) is expanding its effort to deploy, measure, and evaluate various photovoltaic (PV) reference cells and pyranometers at different plane-of-array orientations and at multiple locations. The purpose is to develop new methods/processes and to improve the accuracy (based on using standard thermopile radiometers) from the current uncertainty levels by investigating methods to (1) calibrate reference cells and (2) accurately quantify the PV resource by considering various sources of uncertainty, such as the spectral response and directional response or angle-of-incidence effects (Habte et al 2018). In general, better PV resource measurements enable stakeholders to more accurately estimate PV power production as well as better define its uncertainty.…”

Section: Introductionmentioning

confidence: 99%

PV Reference Cells for Outdoor Use: An Investigation of Calibration Factors

Driesse¹,

Gotseff²,

Sengupta³

2021

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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 of the solar PV resource. 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 when compared to the Cell Lab 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 events 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 events (provided in Appendix B) 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.v

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