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The objective of this work is to quantify de degradation originated by UV radiation and temperature in silvered-glass reflectors exposed in three locations with high solar irradiance and to replicate the degradation mechanisms observed in outdoors through accelerated aging tests.

The solar-thermal parabolic trough power plant Andasol 3 (AS3) near Granada/Spain operated by Marquesado Solar SL (MQS) was commissioned in autumn 2011. The installed capacity of 49.9 MWel in combination with thermal energy storage (TES) capacity for 7.5 hours at full load results in a net annual energy production of more than 165 GWh1 (Dinter and Gonzalez 2014). The German Aerospace Center (DLR) has developed a tool for airborne characterization of entire parabolic trough plants. The approach called QFlySURVEY uses an unmanned aerial vehicle (UAV) equipped with a high resolution digital still camera and delivers effective mirror slope deviation and the absolute orientation of the optical axis of each solar collector element (SCE). In order to validate and demonstrate QFlySURVEY, a comprehensive measurement campaign was undertaken in the AS3 power plant in cooperation with MQS between 2016-10-24 and 2016-11-14. The main objective was to demonstrate the advantages of airborne solar field characterization in terms of rapid data acquisition, negligible interference with plant operation, and without the need of any additional installation of measurement equipment in the solar field. QFlySURVEY provides accurate quantitative measures of optical performance of the solar field and supports the maximization of the thermal energy collected from the solar field by identifying low performing areas and the causes for optical losses.The solar-thermal parabolic trough power plant Andasol 3 (AS3) near Granada/Spain operated by Marquesado Solar SL (MQS) was commissioned in autumn 2011. The installed capacity of 49.9 MWel in combination with thermal energy storage (TES) capacity for 7.5 hours at full load results in a net annual energy production of more than 165 GWh1 (Dinter and Gonzalez 2014). The German Aerospace Center (DLR) has developed a tool for airborne characterization of entire parabolic trough plants. The approach called QFlySURVEY uses an unmanned aerial vehicle (UAV) equipped with a high resolution digital still camera and delivers effective mirror slope deviation and the absolute orientation of the optical axis of each solar collector element (SCE). In order to validate and demonstrate QFlySURVEY, a comprehensive measurement campaign was undertaken in the AS3 power plant in cooperation with MQS between 2016-10-24 and 2016-11-14. The main objective was to demonstrate the advantages of airborne solar field characterization i...

Back-silvered glass mirrors exposed in Abu Dhabi outdoor conditions for 7 years along with corresponding as-received mirrors from the same manufacturing batch which were preserved in a warehouse are analyzed in the present study. The availability of both the as-received mirrors and the exposed ones over a time longer than that in previous studies presents an opportunity to validate accelerated aging tests through comparison with naturally aged mirrors. The exposed mirrors showed substantial reflectance degradation. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) was used to characterize both as-received and exposed samples and compare the as-received sample to a reference mirror from the state-of-the-art commercial solar mirrors. The analyses identified 5 possible causes of the rapid degradation observed for the mirrors in question in comparison to the lifetime expectation for commercial solar mirrors. The findings will serve to guide ongoing and future accelerated-aging studies on the same mirrors.

Two spectra of solar direct normal irradiance (including circumsolar) are estimated based on spatio-temporal averages of the relevant atmospheric parameters extracted from two different databases: MODIS satellite sensor retriev-als and AERONET sun photometer network. The satellite database is used to calculate an average spectrum for the area of the Atacama Desert. The AERONET database is used for two purposes: (i) to apply bias-removal linear methods to correct the MODIS parameters over Atacama Desert, and (ii) to calculate an average local spectrum for the Paranal station. The SMARTS radiative transfer model is used to obtain the three representative spectra developed in this study. Both the Atacama Desert and Paranal spectra are compared against each other and also to the world reference, ASTM G173. In one of the cases, significant differences are found for short wavelengths. In order to quantify the relative im-portance of these spectral differences, the propagation of errors due to the use of each spectrum is evaluated for CSP applications over the Atacama Desert, considering twelve different scenarios involving the reflectance, transmittance or ab-sorptance of various materials.

We investigated the forced convective heat loss from a model of a multi-MW cavity receiver of a concentrated solar power (CSP) tower system in a high-pressure wind tunnel. Measurements of 5 geometrical configurations of this model are reported in this contribution. The experiment covered a Reynolds number range of between 2 ⋅ 106 and 8 ⋅ 106, based on the external flow field. The results show that the maximum forced convective heat loss for all configurations occurs when the wind blows from frontal directions of between 60° and 80° relative to the tower symmetry plane. We found that the peak location does not vary for different inclinations, but does vary for different apertures. Also, the results show that the direction of the wind causes the forced convective heat loss to vary with a factor of up to 6.3. Last but not least, we augmented the interpretation of our heat loss measurements with images produced with a Background-oriented Schlieren Imaging (BOS) setup.

This paper presents results from a characterization of DLR’s second generation sun simulator test facility (OptiRec) for determining the optical performance of parabolic trough receivers. The configuration of the test bench is an elliptical mirror trough with flat end mirrors. Solar simulator lamps are situated in one focal line, the receiver in the other focal line. Water at ambient temperature flows through the receiver and allows for a calorimetric measurement of the absorbed power. Compared to the first generation test bench (ElliRec) the mirror material is changed from aluminum to glass, the ellipse size is changed and the handling is improved. Based on 34 measurements of the absorbed power the repeatability for OptiRec measurements is measured to 0.13% (1σ), compared to 0.2% in the ElliRec. Seven receivers from different manufacturers are measured in both test benches yielding consistent relative optical efficiency with

Solar reflectors for concentrating solar power applications can be subject to performance losses due to their permanent exposure to the environment. In this work the risk of erosion due to sandstorms is evaluated. Aluminum and glass reflector samples were exposed in Missour and Zagora (Morocco) and measurements of the wind velocity and the particle concentration were carried out. Both measured quantities were connected to the single particle momentum distribution SPMD. This novel parameter is shown to be adequate to describe the erosion characteristics of outdoor sites and laboratory setups. Its deduction will be explained and it will be applied to both outdoor sites and two accelerated erosion simulation setups, a sand trickling device -named soil pipe- and a closed loop wind channel with particle injection. Furthermore different erosion failure modes are described and explained by the use of the SPMD.

The optical and thermal efficiency of parabolic trough collector solar fields is dependent on the performance and assembly accuracy of its components such as the concentrator and absorber. For the purpose of optical inspection/approval, yield analysis, localization of low performing areas, and optimization of the solar field, it is essential to create a complete view of the optical properties of the field. Existing optical measurement tools are based on ground based cameras, facing restriction concerning speed, volume and automation. QFly is an airborne qualification system which provides holistic and accurate information on geometrical, optical, and thermal properties of the entire solar field. It consists of an unmanned aerial vehicle, cameras and related software for flight path planning, data acquisition and evaluation. This article presents recent advances of the QFly measurement system and proposes a methodology on holistic qualification of the complete solar field with minimum impact on plant Operation.

Guaranteeing the durability of concentrated solar power (CSP) components is crucial for the success of the technology. The reflectors of the solar field are a key component of CSP plants, requiring reliable methods for service lifetime prediction. So far, no proven correlations exist to relate accelerated aging test results in climate chambers with relevant CSP exposure sites. In this work, correlations have been derived for selected testing conditions that excite the same degradation mechanisms as for outdoor exposure. Those testing conditions have been identified by performing an extensive microscopic comparison of the appearing degradation mechanisms on reference samples that have been weathered outdoors with samples that underwent a high variety of accelerated aging experiments. The herein developed methodology is derived for aluminum reflectors and future work will study its applicability to silvered-glass mirrors.