Browsing by Author "Sutter, Florian"
Now showing 1 - 6 of 6
Results Per Page
Sort Options
- Advanced cyclic accelerated aging testing of solar reflector materialsPublication . Wette, Johannes; Sutter, Florian; Tu, Mai; Fernández-Garcia, Aránzazu; Buendia, Francisco; Carvalho, Maria João; Cunha Diamantino, TeresaABSTRACT: Lifetime prediction methods for the components of concentrated solar power (CSP) plants have been in the focus of interest of manufacturers and plant developers for the past years. Recently, an accelerated aging standard for solar mirrors was published by the Spanish AENOR committee [1]. This standard allows performing comparative testing but it is not suited to derive meaningful life-time estimations. Firstly, the testing defined in the standard is not aggressive enough to produce significant degradation on most of the materials and secondly, it has been shown that the passing of these tests does not guarantee a high durability during outdoor exposure [2]. These findings have proven the need for the investigation of more realistic procedures. To provoke the mechanisms that are detected during outdoor exposure, a more realistic application of environmental stresses is being investigated. In this work a series of tests is conducted in which several weathering stresses are combined and applied in a cyclic manner. Some of these cycles have shown to correlate better with real outdoor behavior.
- Detection of corrosion on silvered glass reflectors via image processingPublication . Wiesinger, Florian; Baghouil, Sarah; Le Baron, Estelle; Collignon, Romain; Santos, Filipa; Cunha Diamantino, Teresa; Catarino, Isabel; Facão, Jorge; Ferreira, Cristina; Páscoa, Soraia; Sutter, Florian; Fernández-García, Aránzazu; Wette, JohannesABSTRACT: A novel characterization technique based on image analysis is presented, intended to complement state-of-the-art reflectometer measurements. The technique is developed by experts from different laboratories (OPAC, AGC, CEA and LNEG), which subsequently conduct two Round Robin experiments on corroded solar reflectors for validation. Regarding the inter-comparability, it is found that parameters like the corrosion spot density or the penetration maximum on coated edges exhibit an average coefficient of variation of 62.6 % and 54.9 %. Better agreement is found for parameters like the total corroded area and the maximum edge corrosion penetration, with coefficients of variation of 14.3 % and 13.4 %, respectively. The developed methodology is further applied during a 68-month lasting outdoor exposure campaign of two types of solar reflectors at two representative sites, one exhibiting corrosivity class C2 and the other C3. On the commercial coating RL1, a total corroded area of 59 mm2 and 426 mm2 is measured after the outdoor exposure on the C2 and the C3 site, respectively, while on the novel low-lead coated reflector RL3 corresponding values are 280 mm2 and 1308 mm2. This shows the superior quality of the coating RL1 in terms of corrosion resistance. Furthermore, the analysis highlights the importance of proper edge sealing for corrosion protection, since corrosion penetration is increased by a factor between 1.3 and 4.0 if the edges are unprotected. The reflectance decrease after the outdoor exposure is regarded as negligible (0.000 - 0.005), thus not permitting any of the conclusions that are made from the novel image analysis technique.
- Dynamic corrosion testing of metals in solar salt for concentrated solar powerPublication . Sutter, Florian; Oskay, Ceyhun; Galetz, Mathias Christian; Cunha Diamantino, Teresa; Pedrosa, Fátima; Figueira, Isabel; Glumm, Stefan; Bonk, Alexander; Aguero, Alina; Rodríguez, Sergio; Reche-Navarro, Tomas Jesus; Caron, SimonABSTRACT: Potassium nitrate and sodium nitrate in mixing proportion of KNO3-NaNO3 40-60 wt% (also called solar salt) has been successfully used for over a decade as heat storage medium for concentrated solar power parabolic-trough collector plants at temperatures up to 400 degrees C. At temperatures of 560 degrees C, reached in state-of-the-art solar tower systems, corrosion of metallic components in contact with solar salt can become an issue and has caused leaks and plant shut-downs in recently built tower projects. While the corrosion rates of several materials have been determined for different temperatures in static molten salt immersion experiments, there is a lack of corrosion data for dynamic in-service conditions. In this work, a dynamic corrosion test has been conducted on 19 different material types including protective coatings, mimicking flow-rate, temperature gradient and draining of inservice operation of a receiver in a concentrated solar power tower. The measured corrosion rates are presented and compared to static corrosion tests reported in literature.
- Influence of gaseous pollutants and their synergistic effects on the aging of reflector materials for concentrating solar thermal technologiesPublication . García-Segura, A.; Fernández-Garcia, Aránzazu; Ariza, M. J.; Sutter, Florian; Cunha Diamantino, Teresa; Martínez-Arcos, L.; Reche-Navarro, T. J.; Valenzuela, L.ABSTRACT: Concentrating solar thermal technologies have experienced an important boost in the last few years. Besides the production of electricity, they are particularly useful for the supply of industrial process heat. The industrial atmospheres affecting these solar plants typically contain gaseous pollutants that are likely to promote corrosion on the components of the solar facility, specifically solar reflectors, thereby compromising their optimal performance and the overall system efficiency. Seven accelerated aging tests were designed to study the effects of three air pollutants (H2S, SO2 and NO2) on the durability of two commercially available reflector types (silvered glass and aluminum), both in single-gas tests and in multicomponent gas mixtures. Additionally, the same material types were exposed outdoors at five representative polluted sites, including industrial, urban and coastal environments. Reflectance and optical microscope monitoring corroborated which degree of corrosion was developed on a specific type of reflector in the different tests with gaseous pollutants, as well as the synergistic effects of gas combinations. For example, tests with sulfur were harmful for silvered-glass reflectors (up to a total of 16 corrosion spots), whereas aluminum was particularly affected by tests with NO2 (numerous micro spots of around 50 pm size). Moreover, comparisons of the corrosion patterns found in accelerated-aging and outdoor exposures revealed which laboratory test reproduced the different real polluted atmospheres in the most realistic way, which is the main goal of this work. For instance, the degradation found at Site 2 was reproduced by Test NO2+SO2, with an acceleration factor of 27.
- Intercomparison of opto-thermal spectral measurements for concentrating solar thermal receiver materials from room temperature up to 800 °CPublication . Caron, Simon; Farchado, Meryem; San Vicente, Gema; Morales, Angel; Ballestrin, Jesus; Carvalho, Maria João; Páscoa, Soraia; Baron, Estelle; Disdier, Angela; Guillot, Emmanuel; Escape, Christophe; Binyamin, Yaniv; Baidossi, Mubeen; Sutter, Florian; Roger, Marc; Manzano-Agugliaro, FranciscoABSTRACT: An intercomparison of opto-thermal spectral measurements has been performed for some relevant receiver materials in concentrating solar thermal applications, from room temperature up to 800 degrees C. Five European laboratories performed spectral measurements at room temperature, while two laboratories performed infrared spectral measurements at operating temperature up to 800 degrees C. Relevant materials include Haynes 230 (oxidized, Pyromark 2500 and industrial black coating) and silicon carbide. Two key figures of merit were analyzed: i) solar absorptance alpha sol at room temperature, over the spectral range [0.3 - 2.5] mu m, ii) thermal emittance epsilon th(T), over the common spectral range [2-14] mu m, derived from spectral measurements performed from room temperature up to 800 degrees C. Oxidized H230 reached an alpha sol value of 90.9 +/- 1.0%. Pyromark 2500 reached an alpha sol value of 96.3 +/- 0.5%, while the industrial black coating achieved an alpha sol value of 97.0 +/- 0.4%. Silicon carbide reached an alpha sol value of 93.5 +/- 1.1%. Low standard deviations in alpha sol indicate reproducible measurements at room temperature. For oxidized H230, the epsilon th,calc(T) value varied from 55% at room temperature up to 81% at 800 degrees C. For Pyromark 2500 and the industrial black coating, epsilon th,calc(T) fluctuated between 90% and 95%, with a weak temperature dependence. For silicon carbide, epsilon th,calc(T) varied from 70% at room temperature up to 86% at 800 degrees C. The typical standard deviation among participating laboratories is about 3%. epsilon th,meas(T) values derived from spectral measurements at operating temperature were consistent within a few percentage points in comparison to epsilon th,calc(T) values derived from spectral measurements at room temperature.
- The importance of developing accelerated tests on the reliability of solar absorber and solar reflector coatingsPublication . Cunha Diamantino, Teresa; Gonçalves, Rita; Páscoa, Soraia; Alves, Isabel N.; Carvalho, Maria João; Fernández-García, Aránzazu; Wette, Johannes; Sutter, FlorianABSTRACT: Selective absorber coatings for solar thermal collectors and reflector coatings for Concentrating Solar Power (CSP) plants are the key components of these technologies and their durability is one of their most important characteristics. They should be low cost and withstand 20-30 years under different kinds of environments without significant loss of optical performance. Commercially, there are different physical vapour deposition (PVD) coatings for aluminium absorbers and reflectors. Results obtained with two commercial PVD solar absorber coatings (SA) and two solar reflector coatings (SR), under different accelerated aging tests (AAT), are presented and correlated with outdoor exposure. An Outdoor Exposure Testing (OET) site with maritime and industrial influence was used for an exposure campaign of the absorbers and reflectors for two years. Alternative artificial aging tests are proposed for absorbers and reflectors that better reproduce the corrosion mechanism obtained in natural conditions with maritime and industrial influence. The characterization of the coatings and degradation mechanisms of different aluminium absorbers and reflectors were evaluated optically, morphologically and chemically. The results obtained in an atmosphere with high corrosivity as in marine and/or industrial areas are a reliable way to verify the corrosion resistance of new materials in a short time and are a valuable tool to validate the different methodologies of accelerated aging tests.