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Acceptance criteria for accelerated aging testing of silvered-glass mirrors for concentrated solar power technologies
摘要： Solar reflectors for Concentrating Solar Power (CSP) technologies are required to maintain their optical properties in demanding environments for more than 20 years of service-life. The durability of the commonly used silvered-glass reflectors is typically qualified by means of accelerated aging. Recently, the Spanish standardization committee UNE has published the first specific standard for this topic, which defines a set of accelerated aging tests for CSP reflectors. However, the standard does not contain pass/fail criteria. This paper proposes useful acceptance criteria for the accelerated tests defined by UNE, helping to interpret the obtained degradation results. The criteria have been determined by analyzing the collected accelerated aging data over the past 5 years in the OPAC laboratory, a joint research group of DLR and CIEMAT. Data from six different 4 mm silvered-glass manufacturers is presented, covering nearly the entire market of commercially available silvered-glass mirrors, and going way beyond the recommended testing times of the UNE standard. The data may be used to benchmark initial reflective properties (before aging) and the performance during accelerated durability testing. In addition, recommendations for improvements of the standard are given and an estimate of the acceleration factor of the Copper Accelerate Salt Spray (CASS) test with respect to a highly corrosive outdoor environment is presented.
关键词： Durability,Accelerated aging testing,Reflectance,Acceptance criteria,Solar reflector,Concentrated solar power
更新于2025-10-22 19:40:53
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Identification of Maize Kernel Vigor under Different Accelerated Aging Times Using Hyperspectral Imaging
摘要： Seed aging during storage is irreversible, and a rapid, accurate detection method for seed vigor detection during seed aging is of great importance for seed companies and farmers. In this study, an artificial accelerated aging treatment was used to simulate the maize kernel aging process, and hyperspectral imaging at the spectral range of 874–1734 nm was applied as a rapid and accurate technique to identify seed vigor under different accelerated aging time regimes. Hyperspectral images of two varieties of maize processed with eight different aging duration times (0, 12, 24, 36, 48, 72, 96 and 120 h) were acquired. Principal component analysis (PCA) was used to conduct a qualitative analysis on maize kernels under different accelerated aging time conditions. Second-order derivatization was applied to select characteristic wavelengths. Classification models (support vector machine?SVM) based on full spectra and optimal wavelengths were built. The results showed that misclassification in unprocessed maize kernels was rare, while some misclassification occurred in maize kernels after the short aging times of 12 and 24 h. On the whole, classification accuracies of maize kernels after relatively short aging times (0, 12 and 24 h) were higher, ranging from 61% to 100%. Maize kernels with longer aging time (36, 48, 72, 96, 120 h) had lower classification accuracies. According to the results of confusion matrixes of SVM models, the eight categories of each maize variety could be divided into three groups: Group 1 (0 h), Group 2 (12 and 24 h) and Group 3 (36, 48, 72, 96, 120 h). Maize kernels from different categories within one group were more likely to be misclassified with each other, and maize kernels within different groups had fewer misclassified samples. Germination test was conducted to verify the classification models, the results showed that the significant differences of maize kernel vigor revealed by standard germination tests generally matched with the classification accuracies of the SVM models. Hyperspectral imaging analysis for two varieties of maize kernels showed similar results, indicating the possibility of using hyperspectral imaging technique combined with chemometric methods to evaluate seed vigor and seed aging degree.
关键词： hyperspectral imaging technology,standard germination tests,support vector machine model,accelerated aging,principal component analysis,maize kernel
更新于2025-09-23 15:22:29
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Effects of temporary fogging and defogging in plastic scintillators
摘要： Recent studies have shown that under certain environmental conditions, plastic scintillators which are used in a variety of applications in outdoor environments develop defects called "fogging", resulting in a reduced useful lifetime and increased maintenance cost. Applications of plastic scintillators include scanning recycled steel going into a processing plant, personnel portals to scan employees, and scanning cargo and cars crossing borders of many countries. In this report, fogging was studied in conventional PVT and PS-based plastic scintillators, both field aged and freshly cast. A new fogging-resistant PVT-based formulation developed by scientists at Lawrence Livermore National Laboratory (LLNL) was tested as well. We used accelerated aging experiments via temperature and humidity cycling in controlled laboratory conditions to create observable temporary fogging defects in small samples (≤1 in3). Photoluminescence and optical transmission studies were used to evaluate the effect of the fogging. The time evolution of the induced temporary fogging formation and defogging (i.e. fading of defects in ambient conditions over time) were recorded using optical microscopy, time-lapse photography, and gravimetric analysis.
关键词： Accelerated aging,Optical microscopy,Scintillator,Gamma detection
更新于2025-09-23 15:22:29
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Accelerated aging of absorber coatings for CSP receivers under real high solar flux – Evolution of their optical properties
摘要： The use of durable high solar absorptance receivers is a key element in a CSP plant project. In this article, different receiver materials are studied: four alloy substrates (T91, T22, VM12, Inconel 617) combined with four new absorber coatings, operable in solar towers with molten salts or steam as heat transfer fluids, and a classic Pyromark? paint considered as a reference. In order to test the durability of the coatings, 200 solar accelerated aging cycles were applied on the samples, using a concentrated solar facility (named SAAF). The cycles were defined so as to apply realistic high solar flux and temperature on the front side of the samples, and with high cooling and heating rates reproducing the fast variation of solar irradiation due to cloudy weather and subsequent thermal shocks. The optical characteristics of the coatings were measured at the beginning and at regular intervals during the aging procedure. Different behaviors of the coatings were observed depending on the substrate, before any aging cycle. After this first aging campaign, some evolutions were observed on the solar absorptance or thermal emittance, depending on the substrate and the coating. Nevertheless, the degradations noticed are not significant enough to conclude about the durability of the coatings.
关键词： Optical characterization,CSP receiver absorber coatings,Solar furnace,Accelerated aging
更新于2025-09-19 17:15:36
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Photovoltaic Modules (Technology and Reliability) || 10. Accelerated aging tests
摘要： All environmental simulation tests which allow an accelerated analysis of material degradation processes through intensified environmental stress levels compared to real life can be summarized under the notion of accelerated aging tests. This type of test is especially useful for products with long service lifetimes, such as photovoltaic modules. As guarantees for PV modules cover up to 30 years of service life, accelerated aging tests are of high economic importance for PV modules manufacturers. As PV manufactures aim for utilizing materials which are both economically and technically suitable, accelerated aging tests on full PV modules as well as on separate materials and material combinations are necessary. It is in the interest of the customer as well the investor and the insurance that the product achieves the expected service life without major performance losses. The aim of accelerated aging tests is to achieve reliable results within a very short period of time and with minimum costs in order to keep pace with the rapid innovation cycles. In order to ensure the transferability of the testing result on real life performance, a specific adaptation of the test conditions to the specific materials and stress factors is indispensable. Otherwise, climatic conditions may be induced which either exceed or undermine those under standard operation, and this may subsequently lead to altered physical or chemical degradation processes. Thus, the processes which occur under standard operation should be accelerated but at the same time simulated as close to reality as possible.
关键词： photovoltaic modules,service life,environmental stress,material degradation,accelerated aging tests
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 12th International Symposium on Diagnostics for Electrical Machines, Power Electronics and Drives (SDEMPED) - Toulouse, France (2019.8.27-2019.8.30)] 2019 IEEE 12th International Symposium on Diagnostics for Electrical Machines, Power Electronics and Drives (SDEMPED) - Parametric degradation model of OLED using Design of Experiments (DoE)
摘要： This article presents an original parametric degradation model using Design of Experiments. This method is based on the estimation of a Weibull function under accelerated conditions. It is applied on cold white organic light emitting diodes OLEDs from Philips with a 10000 hrs theoretical lifetime. Accelerated degradation using thermal and electrical stress is tested. The predicted degrading model is a function of time, temperature, current density and their interaction. It illustrates the behaviour of the degradation of the OLED using multiple stress factors without really knowing the physics of these degradations. The proposed model is tested on experimental data for different luminances. The average error of the predicted model compared to real values is around 3 %. The proposed model is then compared to a previously developed lifespan model. The results obtained with the present approach are closer to the real values.
关键词： Degradation,Electrical stresses,Modeling,Thermal stresses,Design for Experiments,Accelerated aging,Organic light emitting diodes,Weibull distribution,Lifetime estimation
更新于2025-09-12 10:27:22
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Framework for predicting the photodegradation of adhesion of silicone encapsulants
摘要： We developed a framework to predict and model the photodegradation of adhesion and cohesion of a silicone encapsulant for concentrator photovoltaic applications. Silicone encapsulant specimens were artificially weathered under narrow band UV filters to determine the effects of individual wavelengths within the UV spectrum on the photodegradation of the cohesion of encapsulant material and its adhesion with adjacent interfaces. The threshold wavelength, signifying the upper bound of the damaging action spectrum for the silicone, was identified from the results. In addition, specimens were artificially weathered with different relative humidities to understand the effects of moisture on the rate of photodegradation. The adhesion energy was measured using a fracture mechanics approach. The complementary delaminated surfaces were characterized to determine the failure pathway and chemistry changes resulting from photodegradation. A previously developed model was modified to account for the effects of damaging wavelengths in the terrestrial solar spectrum and reciprocity law failure due to varying UV intensity during weathering. With these modifications, the model showed good agreement with the behavior of the silicone encapsulant exposed in an outdoor solar concentrator simulating concentrator photovoltaics operating conditions. Similar studies can be adopted to develop models that can have high predictive accuracies based on accelerated aging studies.
关键词： Accelerated aging,Concentrator photovoltaics,Photodegradation,Encapsulant,Lifetime prediction,Silicone
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Thermally Triggered SiC MOSFET Aging Effect on Conducted EMI
摘要： In this paper, thermally triggered SiC MOSFET aging effect on SiC based boost PFC converter’s conducted EMI is investigated. Existing EMI evaluation and suppression studies are mostly based on power devices at healthy state. This study provides a comprehensive EMI evaluation at different state of health of SiC MOSFET used in continuous conduction mode (CCM) Boost PFC converter. For this purpose, SiC MOSFET samples are exposed to accelerated aging and the corresponding device degradations are triggered by thermal stresses. To study device characteristics at different state of health, devices under test (DUT) electrical parameters and switching transients are evaluated over aging to support SiC based AC/DC converter’s conducted EMI discussion. Respectively, device aging effect on differential mode (DM) noise and common mode (CM) noise changes are discussed in detail. An 800W single phase CCM Boost PFC prototype is built to evaluate both DM and CM noise in band B frequency range (150kHz~30MHz) with experimental testing results. According to the study, high frequency noise decrement is observed after SiC MOSFET is thermally aged.
关键词： thermal stress,power factor correction (PFC),Accelerated aging,SiC power MOSFET,EMI/EMC
更新于2025-09-04 15:30:14