Characterization of new and degraded mirrors with AES, ESCA and SIMS (original) (raw)
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The lifetime of mirrors in outdoor conditions is crucial in the correct operation of any concentrating solar power (CSP) installation. In this work, the corrosion behavior of two types of metallized surfaces was studied. The first was made of a flexible polymer having a deposited reflective silver metallic film. The second was made of the same surface type with a dielectric SiO2 protection coating by an atmospheric pressure plasma jet. Polycarbonate sheets were used as substrates on which metallic silver was deposited by the Dynamic Chemical Deposit technique. This electroless technique allowed producing the mirror finishing under environmental conditions by sequentially spraying; as aerosols projected towards the substrate surface, the activation and reducing-oxidizing solutions with rinsing after each one. The silver coatings were about 100 nm thick. Environmental and accelerated weathering degradation and salt and sulfide fogs were carried out. XPS analyses show that the corrosio...
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Durability analysis of solar mirrors is attracting attention from Concentrating Solar Power (CSP) developers because guaranties of a suitable optical behavior during the whole service life time are required. To give realistic life time estimations in affordable time, research institutes are investing a lot of effort in developing appropriate accelerated aging tests. In this paper, an extensive test campaign of accelerated aging tests has been performed with silvered-glass mirrors from several manufacturers. Three commercial outdoor-proven products, a not outdoor-proven mirror prototype and two mirrors which showed degradation after only three years of outdoor operation in Spain and Australia have been tested. The accelerated aging tests were conducted for an extended period of time in order to determine the testing time at which the two mirror materials that showed degradation outdoors start to fail under the accelerated conditions. The degradation of the outdoor exposed mirrors is ...
Solar Energy Materials and Solar Cells, 2017
Atmospheric pressure air plasma treatment was applied to glass substrates to improve the adhesion of the reflective silver layer of mirrors used in solar power systems. This treatment attempts to prevent problems related to the detachment of this layer that affect its energy performance. Untreated and plasma treated glass substrates were subjected to a spray coating process to fabricate mirrors. Chemical characterization by X-ray Photoelectron Spectroscopy (XPS) and measurements of the water contact angle (WCA) were undertaken on the glass substrates before the plating process. The reflectivity of the mirrors was studied by spectrophotometry in the wavelength range of 280-2500 nm, and the adhesion between the glass substrates and the silver layers was measured by pull-off tests. In order to determine the relationship between the parameters of the plasma treatment and the adhesion and reflectivity of the mirrors, different combinations of treatment speeds and gap distances between the glass substrates and the plasma nozzle were used. It was observed that the plasma treatment has a cleaning effect and forms oxygen-based functional groups that promote the hydrophilicity of the glass substrates. This double effect resulted in improved adhesion of the silver layer to the plasma treated substrates, with no significant loss of solar reflectance of the mirrors. The plasma treatment with the lowest gap distance (2 mm) and the lowest speed (1 m/min) achieved the best results in this work. It brought an improvement of 85.8% in the breaking strength of the untreated glass mirror and no significant variation in the solar reflectance in as-fabricated conditions. After accelerated aging, it maintained an improvement of 27.2% in the breaking strength and showed higher solar reflectance than the untreated glass mirror.
Outdoor exposure testing of silvered-glass reflectors under marine environment
SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems
Marine environments are characterized by aggressive climate conditions that are suitable for materials durability testing especially for solar mirrors. In order to obtain real data and significant results of new solar mirrors durability in shorter time, outdoor ageing tests could be conducted in such high corrosive environment since it provokes faster degradation. This paper presents the results of the first year of natural exposure testing of different type of silvered glass mirrors at a marine site in Morocco. Many failure modes were observed and analyzed during this study. Corrosion is the predominant failure mode that occurs in all mirror samples and causes a significant loss of their reflectivity. The behavior of tested mirrors was found to be depending especially to the used paint system.
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Silver (Ag) mirrors for astronomical telescopes consist of multiple metallic and dielectric thin films. Furthermore, the topmost surface of such Ag mirrors needs to be covered by a protection coating. While the protection coating is often deposited at room temperature and the entire mirrors are also handled at room temperature, various thin film deposition techniques offer protection coatings with improved characteristics when carried out at elevated temperatures. Thus, in this work, high-performance Ag mirrors were designed and fabricated with a new benchmark. The resulting Ag mirrors were annealed (i.e., post-fabrication annealing) at various temperatures to investigate the viability of introducing thermal processes during and/or after fabrication in improving overall optical performance and durability of protected silver mirrors. In our experiments, Ag mirror samples were deposited by electron-beam evaporation and subsequently annealed at various temperatures in the range from 60 °C to 300 °C, and then the mirror samples underwent an environmental stress test at 80 °C and 80% humidity for 10 days. While all the mirror samples annealed below 200 °C showed negligible corrosion after undergoing the stress testing, those annealed below 160 °C presented spectral reflectivity comparable to or higher than that of as-deposited reference samples. In contrast, the mirror samples annealed above 200 °C exhibited significant degradation after the stress testing. The comprehensive analysis indicated that delamination and voids caused by the growth of Ag grains during the annealing are the primary mechanisms of the degradation.
Physical and chemical reactivity of mechanically primed glass surfaces of CSP reflectors
SOLARPACES 2019: International Conference on Concentrating Solar Power and Chemical Energy Systems
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