Influence of Ni–Al coating thickness on spectral selectivity and thermal performance of parabolic trough collector

• Published in: Materials for renewable and sustainable energy Vol. 7; no. 3; pp. 1 - 9
• Main Authors: Suriwong, Tawat, Bunmephiphit, Chanon, Wamae, Warisa, Banthuek, Sathit
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.08.2018; Springer Nature B.V; SpringerOpen
• Subjects: Absorptance; Absorptivity; Aluminum coatings; Aluminum oxide; Austenitic stainless steels; Chemical composition; Chemistry and Materials Science; Coatings; Materials Science; Morphology; Nickel; Ni–Al; Original Paper; Parabolic trough collector (PTC); Reflectance; Renewable and Green Energy; Selectivity; Solar absorber; Solar absorptance; Solar collectors; Solar energy; Solar energy absorbers; Solar radiation; Stainless steel; Statistical analysis; Statistical methods; Thermal energy; Thermal performance; Thermodynamic efficiency; Ni–Al; Parabolic trough collector (PTC); Solar absorptance; Solar absorber; Thermal performance
• ISSN: 2194-1459; 2194-1467
• DOI: 10.1007/s40243-018-0121-0

This study investigates the influence of Ni–Al coating thickness on the spectral selectivity and thermal performance of a parabolic trough collector (PTC). Three thicknesses of Ni–Al coating for use as solar absorber material were successfully prepared on the outer surface of a stainless steel 316L (SS) tube by flame spray. The phase, morphology, and reflectance ( R ) of the Ni–Al coatings were characterized using several techniques. The PTC and solar receiver tube were specially designed and constructed for observing the collector thermal performance by following ASHRAE 93-1986. Looking at the results, the actual average thicknesses of the three Ni–Al coatings turn out to be 195, 215, and 299 μm. The morphology and chemical composition of all three thicknesses are similar. The chemical composition in the cross-sectional view exhibits non-uniform distribution. The three thicknesses of the coating are composed of NiO and Al 2 O 3 phases, which also corresponded to the results of SEM–EDX mapping. The differences in a solar absorptance ( α ) of the three thicknesses of Ni–Al coating are not statistically significant, with an average α value of 0.74–0.75. However, there are differences in thermal efficiency of the PTC depending on the thickness of the Ni–Al coating. Of the three samples, the thickest one (299 µm) demonstrates the highest ability to convert solar radiation into thermal energy.