Performance analysis of non-contact nanostructure solar desalination system by varying water depth at a constant air gap

Abstract

Solar desalination could be one potential solution to the grandest challenge of water scarcity. Recent works have been carried out in developing high solar energy-absorbing materials in direct contact with water to enhance the productivity of the solar still. However, due to the direct contact with contaminated water, the solar absorbing materials undergo degradation/fouling over time. To overcome this fouling problem, in this work, we have designed and developed a novel non-contact nanostructure (NCNS) through chemical oxidation and coating process that is physically and thermally decoupled from the water inside the solar still. The developed non-contact nanostructure absorbs solar radiation due to the high absorptive nanocoating on top, converts the absorbed solar energy to infrared radiations through thermal down-conversion, and emits the infrared (IR) radiations from the bottom through the high emissive coating. Water, an excellent absorber of IR radiations, readily absorbs the IR radiations and evaporates through the perforations, thus producing a desalination effect. Due to this non-contact mode of heat transfer, fouling is wholly avoided. Experiments were performed to analyze the effect of water depth at a constant air gap. It was found that enhancement in productivity for 1 cm water depth case, when compared with 2 cm and 3 cm water depth case, was 11.11% and 25%, respectively. Analytical modeling, fouling study, accelerated corrosion study, and in-depth water quality assessments were also performed, and the results were so promising that the freshwater obtained was safe for drinking and free from impurities, bacteria, and viruses.