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- 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.