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Optical, structural and thermal performances of black nickel selective coatings for solar thermal collectors
Journal
Solar Energy
ISSN
0038092X
Date Issued
2022-03-01
Author(s)
Kafle, Bhim P.
Basnet, Bijaya
Timalsina, Bikash
Deo, Akash
Malla, Tek N.
Acharya, Nayan
Adhikari, Anish
Abstract
In the present study, the possibility of devising efficient and durable black nickel selective coating based solar thermal collectors (STCs) at ambient temperature was explored. For this, NASA electrochemical bath initially formulated by Peterson and Lin [Final Report: NASA-CR-149928, 1976] was employed. Quality of the STCs were optimized by evaluating pH, temperature, electric current density (Id) and deposition time (Td) dependence of optical, structural and thermal performance of the black nickel coating on the copper sheets and tubes. The optical measurements in the UV–Vis–NIR and NIR-MIR ranges inferred us that at pH ≈ 5.8, temperature in the range 20–25 °C, 2 mA/cm2 ≤ Id ≤ 4 mA/cm2 and 5 min. ≤ Td ≤ 7 min. result in reasonably good black nickel coatings with optimal selectivity factor. Moreover, from the analysis of XRD spectra, for the first time we observed the significantly larger crystallites size of coatings on Cu sheets than that of the coating on tubes. Observed thermal performances (evaluated by measuring the collector efficiencies) indicate that the electro-deposited black nickel-based STCs were superior by more than 20% over black paint based STCs.
Subjects