Evaluation of Potential Residual Silica as Antireflective Layer for Selective Solar Surface of Black Chromium

Abstract

Selective surfaces have the function of absorbing strongly the sunlight, while ideally losing little heat to the environment via convection and radiation. The present study sought to obtain a selective surface of black chromium coated with an antireflective (AR) layer based on sugarcane bagasse ash using copper as a substrate. From this selective surface the electrodeposition parameters (time, working distance, voltage) as well as the surface behavior were analyzed in order to determine if the AR layer provided an increase in the absorption levels of the film. By means of the present study it was possible to conclude that, in terms of the electrodeposition parameters evaluated, the anode-cathode distance of 5 cm stimulated the obtaining of higher levels of absorption. The addition of the antireflective layer on the black chromium films favored the increase of the absortance average in all the adopted parameter sets, besides reducing the standard deviation around the average. As for the microstructure of the obtained films, the increase of the parameter Ra promoted the increase of the absorption, due to the formation of optical traps.

Effect of Electrodeposition Time on Absorptance, Roughness and Thermal Stability of Black Chromium Absorbing Surfaces

“…The roughness is a fundamental characteristic in defining the radiation absorption capacity in the visible and near infrared region. Thus, it can be seen in Table 3 that the increase in roughness leads to an increase in absorptance until the time of 10 min 11 . For longer electrodeposition time, increasing R p , R v and R a parameters does not increase light trapping.…”

“…To perform the electrodeposition, an Agilent model E3631A power supply was used as a current source. A voltage of 5 V was established based on results obtained in the literature 8,11 . In addition, the electrodes were spaced 30 mm apart, temperature was set at 30 ºC, and the electrodeposition time was varied in 9 conditions (0.5, 1, 2, 5, 10, 20, 40, 60, and 120 minutes).…”

“…One of the factors that influence the results obtained from the electrodeposition is the time. Several authors choose to establish fixed conditions (distance between electrodes, voltage, among others) and evaluate the surfaces with various times [7][8][9][10][11] , aiming to obtain efficient selective surfaces.…”

Electrolytic Deposition of Ni/NiO on Stainless Steel for Production of Selective Surfaces

“…Electrolytic deposition is a simple technique with a low production cost and that allows to obtain films with good properties. In addition, this deposition technique can be carried out at room temperature and atmospheric pressure, which is attractive for the industry 11 .…”