Abstract
The search for the reduction of costs for the implementation of renewable energies implies in the optimization of the parameters of the manufacturing processes of consolidated technologies. Among these technologies are the solar collectors composed of absorber films characterized by high absorption in the spectrum range corresponding to solar radiation and low emittance in the infrared range, allowing an increase in the collector's operating temperature (300 to 700°C). The present work produced selective surfaces based on black chrome absorber films on stainless steel substrate by electrodeposition. The substrates were immersed in a chromium trioxide bath with hexafluorosilicic acid using a Pb-Sn electrode. In the project some parameters of deposition were evaluated (time, distance and voltage) and their influence on the surface roughness of the coatings obtained by correlating them with the absorptions of the produced surfaces. For this, the surfaces produced were characterized by UV-Vis-NIR, profilometry and SEM. The results indicate that the working distance directly influenced the increase of the films absorption and that the influence of the surface roughness on the film absorption is related to the electrodeposition time as the voltage is raised.
Highlights
The study of renewable sources of energy has become extremely relevant ahead of the growing world demand for energy[1]
The absorptive films produced by electrodeposition of black chromium, through alternation of voltage, anodecathode distance and residence time in the electrolytic bath, were subjected to radiation with wavelengths in the range of 220 nm to 1400 nm, in order to determine spectral reflectance of these films
When considering the standard deviation, sample 6 reached a maximum absorptance of 96%. This means that, regarding the electrodeposition parameters, the 5V and 5 cm distance between anode-cathode and the time of 5 minutes in the electrolytic bath allowed the best conditions in terms of absorption and stability
Summary
The study of renewable sources of energy has become extremely relevant ahead of the growing world demand for energy[1]. One of its forms of exploitation is through the use of solar collectors, which promote the conversion of solar energy into thermal energy[2] This conversion might have its efficiency amplified by the use of special coatings, called selective surfaces, which absorb the maximum possible radiation in the ultraviolet, visible and near infrared (UV-Vis-NIR) range of the electromagnetic spectrum[3], while emitting little in the medium and distant infrared region, that is, they have an absorptance above 85% and emittance below 15% in the wavelength ranges mentioned[4]. There are several techniques for obtaining selective solar coatings, such as: Electrodeposition, Chemical Vapor Deposition, Sputtering, Chemical Oxidation and Sol-Gel[5]
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