Black Body-Inspired Chemically Oxidized Nanostructures with Varied Perforations: A New Frontier in Solar Desalination

Ideal black bodies absorb all electromagnetic energy without reflecting it. As it does not reflect or transmit light, it appears black when cold. Heated black bodies emit black body radiation, a temperature-dependent spectrum. This idea helps scientists and engineers comprehend heat radiation and design efficient solar desalination absorbers. This work uses the black body concept to create three non-contact nanostructured single-slope solar stills (NCNSSSs) with varied perforation diameters (2.4 mm, 3.2 mm, and 3.8 mm). The chemical oxidation of mirror-polished perforated stainless steel 304 sheets resulted in highly absorptive top surfaces with 90% absorptivity. The structures’ bottom surfaces were coated with a commercial high-emissivity coating to make them 85% emissive. The developed non-contact nanostructures absorbed maximum solar light and converted it into infrared radiation using a highly emissive bottom coating and a very absorptive top coating. Water, an excellent absorber of infrared (IR) radiation, readily absorbs the IR radiations and evaporates through the perforations, thus producing a desalination effect. Experiments were conducted parallelly in three NCNSSSs under the same weather conditions at three water depths. It was observed that non-contact nanostructure perforation diameters affected solar still performance. The NCNSSS-3 (3.8 mm) achieved a 9.89% and 13.47% higher productivity than the NCNSSS-2 (3.2 mm) and NCNSSS-1 (2.4 mm) at a 5 mm water depth. Additionally, fouling studies, expedited corrosion studies, and water quality assessments (TDS, salinity, fluoride, chlorides, nitrates, sodium) were performed. Water eminence examinations confirmed that the collected freshwater was bacteria-free and safe to drink.