Uncertainty of rotating shadowband irradiometers and Si-pyranometers including the spectral irradiance error

Wilbert, Stefan; Kleindiek, Stefan; Nouri, Bijan; Geuder, Norbert; Habte, Aron; Schwandt, Marko; Vignola, Frank

doi:10.1063/1.4949241

Cited by 36 publications

(37 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Ineichen and Perez [9] present a formulation of TL to remove its original dependence on air mass. In the first step of the cloud detection, the TL of each timestamp and its temporal gradient is analyzed as described in [10] and [11]. The algorithm detects a cloud if an upper threshold for TL (calculated according to [9]) of 13 is exceeded or if the TL displays a strong temporal variability (more than 0.06 difference between two time steps of 1 min).…”

Section: Deriving the Sunshape From Csc Or Csrmentioning

confidence: 99%

Sunshape measurements with conventional rotating shadowband irradiometers

Wilbert

Röger

Csambor

et al. 2018

AIP Conference Proceedings

Self Cite

View full text Add to dashboard Cite

Because of forward scattered radiation in the atmosphere, the circumsolar region closely surrounding the solar disk looks very bright. The radiation coming from this region, the circumsolar radiation, is in large part included in direct normal irradiance (DNI) measurements at the usual 2.5° pyrheliometer opening half angle, but only partially intercepted by the receivers of focusing solar collectors. Therefore, circumsolar radiation measurements are recommended to be included in solar resource assessment. Circumsolar radiation can be characterized using the radial angular distribution of the radiance around the center of the sun-the so-called sunshape. Several sunshape measurement methods have been developed recently. Most approaches use cameras or pyrheliometers with different apertures which require daily maintenance. The Rotating Shadowband Irradiometer (RSI) based method discussed here uses a conventional RSI without any hardware modification to enable sunshape measurements without affecting the RSI's fundamental function as a DNI measurement device. Thus, it allows to measure circumsolar radiation without any additional hardware and with significantly lower maintenance requirements. The presented RSI-based sunshape measurement algorithm has been validated with four RSIs and more than two years of data. After a short description of the method to derive the circumsolar contribution, the validation results are shown. Then the required calibration method is discussed, followed by the results from the measurement campaigns at four sites in Spain, India and Morocco. It was found that no individual calibration is required per instrument and the algorithm can be used for automatic data processing so that common RSI stations can measure the sunshape with comparably low extra effort. Furthermore, we explain how to derive sunshapes from the RSI measurements.

show abstract

Section: Deriving the Sunshape From Csc Or Csrmentioning

confidence: 99%

Sunshape measurements with conventional rotating shadowband irradiometers

Wilbert

Röger

Csambor

et al. 2018

AIP Conference Proceedings

Self Cite

View full text Add to dashboard Cite

show abstract

“…The Linke turbidity is calculated from DNI or GHI measurements using the Linke turbidity model from . Via the temporal variation of the Linke turbidity, shaded ground measurements are excluded using a Linke turbidity–based method presented in the previous studies . Afterwards, the current Linke turbidity is determined using a linearly time‐weighted average of the most recent Linke turbidities derived from unshaded irradiance measurements.…”

Section: Validation Of Cloud Segmentationmentioning

confidence: 99%

Validation of an all‐sky imager–based nowcasting system for industrial PV plants

Kuhn¹,

Nouri²,

Wilbert³

et al. 2017

Progress in Photovoltaics

Self Cite

View full text Add to dashboard Cite

International audienceBecause of the cloud-induced variability of the solar resource, the growing contributions of photovoltaic plants to the overall power generation challenges the stability of electricity grids. To avoid blackouts, administrations started to define maximum negative ramp rates. Storages can be used to reduce the occurring ramps. Their required capacity, durability, and costs can be optimized by nowcasting systems. Nowcasting systems use the input of upward-facing cameras to predict future irradiances. Previously, many nowcasting systems were developed and validated. However, these validations did not consider aggregation effects, which are present in industrial-sized power plants. In this paper, we present the validation of nowcasted global horizontal irradiance (GHI) and direct normal irradiance maps derived from an example system consisting of 4 all-sky cameras (“WobaS-4cam”). The WobaS-4cam system is operational at 2 solar energy research centers and at a commercial 50-MW solar power plant. Besides its validation on 30 days, the working principle is briefly explained. The forecasting deviations are investigated with a focus on temporal and spatial aggregation effects. The validation found that spatial and temporal aggregations significantly improve forecast accuracies: Spatial aggregation reduces the relative root mean square error (GHI) from 30.9% (considering field sizes of 25 m2) to 23.5% (considering a field size of 4 km2) on a day with variable conditions for 1 minute averages and a lead time of 15 minutes. Over 30 days of validation, a relative root mean square error (GHI) of 20.4% for the next 15 minutes is observed at pixel basis (25 m2). Although the deviations of nowcasting systems strongly depend on the validation period and the specific weather conditions, the WobaS-4cam system is considered to be at least state of the art

show abstract

“…To provide accurate measurements of incident irradiance during the morning and evening hours, the effects of the spectral distribution shift need to be considered. Work on modeling the effect of spectral shift was discussed early on , 1998, Vignola, 1999 and has been the foundation of adjustment algorithms that remove systematic effects for rotating shadowband radiometers the utilize photodiode-based pyranometers (Augustyn, 2004, Lee, 2016, Vignola, 2014, Wilbert, 2016.…”

Section: Discussionmentioning

confidence: 99%

Proceedings of the SOLAR 2017 Conference

2017

View full text Add to dashboard Cite

Uncertainty of rotating shadowband irradiometers and Si-pyranometers including the spectral irradiance error

Cited by 36 publications

References 12 publications

Sunshape measurements with conventional rotating shadowband irradiometers

Sunshape measurements with conventional rotating shadowband irradiometers

Validation of an all‐sky imager–based nowcasting system for industrial PV plants

Proceedings of the SOLAR 2017 Conference

Contact Info

Product

Resources

About