Comparative analysis of solar still with and without use of coating of waste toner powder on absorber plate and hyperbolic fins

Solar stills are considered to be a simple apparatus used to convert saline water into potable water by the application of solar energy. Because of its low distillate yield, it is not used for industrial or domestic applications of potable water. This study introduces a modified solar still (MSS) that integrates a toner waste powder (TWP) nanocoating with composite hyperbolic fins, tested under the climatic conditions of Palanpur, Gujarat, India. Both fully and partially submerged fins were examined, and a partially submerged design showed superior thermal performance. Compared to the conventional solar still (CSS), the MSS achieved ~ 4 °C higher basin water temperature, yielding 45.84% more freshwater (0.999 L vs. 0.685 L per 0.25 m²), energy and exergy efficiencies increased by 45.6% and 72%, respectively. Despite 36% higher manufacturing costs, unit water cost decreased (0.0148 vs. 0.0158 USD/L), while payback time was shortened (3.76 vs. 4.02 months). These findings demonstrate that hyperbolic fins integrated with waste-derived nanocoating are a cost-effective and sustainable alternative to conventional nanomaterials for solar desalination.