Advanced measurement techniques to characterize the near-specular reflectance of solar mirrors

Sutter, Florian; Fernández-García, Aranzazú; Heimsath, Anna; Montecchi, M.; Pelayo, Cristina

doi:10.1063/1.5117618

Cited by 8 publications

(5 citation statements)

References 8 publications

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“…The comparison of reflectometer data with this kind of reference data, achieved with an advanced laboratory device (e.g. as in [2]), is planned for a future campaign and the agreement of data at comparable parameters (especially the φ) will be investigated. In addition, newly developed advanced optical models for soiled and degraded reflectors will be used to evaluate measurements with simulated results for comparison.…”

Section: Eroded Silvered-glass Mirrormentioning

confidence: 99%

“…wavelength of the light, λ, the incidence angle, θi, the divergent angle of the light-source, φi and the acceptance angle, φ. The measurement of this reflectance parameter is not trivial and nowadays can only be performed by specialized laboratories [2,3]. For practical reasons, different reflectance parameters that are easier to measure are used.…”

Section: Introductionmentioning

confidence: 99%

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Comparison of Commercial Reflectometers for Solar Mirrors

Wette,

Sutter,

Sánchez-Moreno

et al. 2023

SolarPACES Conf Proc

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The important in-field characterization of solar mirror reflectance can be performed by a variety of commercial portable reflectometers. In this study the most common commercially available reflectometers are evaluated in a campaign comparing different reflector materials, covering a wide range of realistic reflectance and specularity values. Where possible, measurements are compared to reference values measured with laboratory equipment. In general, good agreement between measurements is detected for highly specular mirrors (average deviation 0.005±0.004) and methods for improvement are proposed when deviations are detected. Important differences between measurements are found for less specular reflectors, which are caused by the disparity of the measurement parameters of the devices. These differences confirm that detailed knowledge about the device characteristics is important, to be able to correctly interpret and utilize gained results, especially for soiled and degraded mirrors.

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Section: Eroded Silvered-glass Mirrormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparison of Commercial Reflectometers for Solar Mirrors

Wette,

Sutter,

Sánchez-Moreno

et al. 2023

SolarPACES Conf Proc

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“…This value describes the amount of energy reflected around the specular direction according to the law of reflection and is bounded by ϕ. Measurement of spectral specular reflectance is problematic at this time because adequate instrumentation that can define representative ϕ for CST technologies and in a wide λ range is not marketed although, in the past years, several prototype instruments and methods have been developed to determine it [10], [13]- [15]. In commercial reflectometers, specular reflectance can only be appropriately measured at a certain selected λ and a fixed near-normal ϕ.…”

Section: A Reflectance Definitionsmentioning

confidence: 99%

Uncertainty Study of Reflectance Measurements for Concentrating Solar Reflectors

Buendía-Martínez

Fernández-García

Sutter³

et al. 2020

IEEE Trans. Instrum. Meas.

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The solar reflector is one of the main components of concentrated solar thermal systems. Therefore, accurate knowledge of its solar-weighted, near-specular reflectance is highly important. Currently, this parameter cannot be properly measured with a single commercial instrument. There is a great interest in having a suitable procedure that can guarantee the accuracy of reflector quality analysis, which already led to the publication of an international measurement guideline (title "Parameters and method to evaluate reflectance properties of reflector materials for concentrating solar power technology"). Still, more research work is needed to improve the state of the art. At present, both the specular reflectance and the spectral hemispherical reflectance are measured by using commercial portable reflectometers and spectrophotometers, respectively, to gain enough information. This article concentrates on the evaluation and calculation of the type-B (nonstatistical) uncertainties associated with these employed instruments and, therefore, leads to a more accurate definition of the measurement uncertainty. Considering type-B uncertainty, the expanded uncertainties of measurements for most of the reflector types are U B,ref = 0.006 for monochromatic specular reflectance and U B,spec = 0.016 for solar-weighted hemispherical reflectance.

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“…For all these reasons, the development of new specular reflectometer laboratory prototypes is being supported in the SolarPACES task III by several research institutes e.g. SMQ2 by ENEA, S2R by DLR, VLABS by Fraunhofer-ISE and a custom spectrophotometer by the University of Zaragoza summarized in [5]. This paper aims to investigate how different dust levels and colors affect the reflectance value and to validate the performances of the laboratory automatized soiling sensor previously described in [6] developed in Wascop project [7] and patented [8] by comparison with various commercial equipment [9] [10].…”

Section: Introductionmentioning

confidence: 99%

Study of Dust Particles on Solar Mirrors for Measurement of Soiling by Specular Reflectance and Imaging Assessment

Le Baron,

Grosjean,

Disdier

2024

SolarPACES Conf Proc

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During the life time of Concentrated Solar Power plants (CSP), optical performances of solar mirrors are affected by soiling phenomena and surface degradations. In order to provide an adequate cleaning strategy, operators must determine the performance loss induced by soiling. Several commercial instruments already exist to measure optical reflectance, but they are dedicated to a single wavelength range or angle, contact and punctual measurements or to laboratory analyses. CEA has developed a new kind of sensor to measure separately the loss of specular reflectance thanks to a CCD camera and photodiodes. In this study, we compared the cleanliness factor calculated with the specular reflectance measured by commercial devices with the image processing performed with our equipment on different artificially soiled solar mirrors. The aim is to ensure that different levels of dirt on the mirrors can be easily assessed with a camera and image processing. We conclude that the level of soiling and the calculation of the percentage of dirty surface are similar to the measurement of the absolute reflectance for all the mirrors tested. These combinations of non-contact, automated, fast and precise measurement with image processing are reproducible for all levels of soiling.

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Advanced measurement techniques to characterize the near-specular reflectance of solar mirrors

Cited by 8 publications

References 8 publications

Comparison of Commercial Reflectometers for Solar Mirrors

Comparison of Commercial Reflectometers for Solar Mirrors

Uncertainty Study of Reflectance Measurements for Concentrating Solar Reflectors

Study of Dust Particles on Solar Mirrors for Measurement of Soiling by Specular Reflectance and Imaging Assessment

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