Nanostructured coatings for enhanced photothermal conversion in solar desalination systems

Conventional solar driven desalination systems have suffers from low thermal efficiency and salt accumulation. This paper examines the use of black silicon and carbon nanotube based surface coatings to increase photothermal performance of solar desalination systems. The absorber plates were spray coated with these coatings using a low cost spray coating technique and tested in outdoors weather conditions. The maximum evaporation rate reached 2.65 kg/m²·h under solar irradiance of 870 W/m² for the coated system, compared to 1.12 kg/m²·h for the uncoated control. Consequently, more than 99 % of the total dissolved solids (TDS) concentration was removed from the collected water, as confirmed by spot water tests that fell within WHO's potable water limits. First, the coatings showed sufficient thermal stability after 1000 h at 900 °C and a preliminary economic analysis indicated a projected coating cost ranging from USD 8–12/m² with a return on investment favorable for offgrid deployment. This work distinguishes itself from the previous studies by simply combining spectrally optimized nanomaterial with scalable fabrication with the evaluation of environmental impact, anti-fouling behavior and ion rejection mechanisms. These results indicate that black silicon–carbon nanotube composites are a durable, efficient and scalable approach toward sustainable solar based desalination technologies.