Enhancing the performance of stepped solar stills: A comprehensive study on design optimization, material integration, and techno-economic feasibility

Access to clean water remains a critical global challenge, particularly in regions facing water scarcity and limited energy resources. Solar distillers provide a sustainable desalination solution, yet conventional designs suffer from low yield and efficiency, hindering widespread adoption. This research addresses these limitations by enhancing stepped solar still (STSS) performance through systematic design modifications and parametric optimization. Three distinct absorber geometries were investigated—regular flat (RSTSS), finned (FnSTSS), and corrugated (CrSTSS)—alongside various wicking materials (jute, charcoal, steel wool fibers, and water coral fleece) and thermal storage options including gravel, yellow sand, and phase change materials (PCM) such as paraffin wax. Experimental and analytical evaluations revealed that FnSTSS and CrSTSS configurations achieved respective productivity gains of 39 % (3750 mL/m²) and 54 % (4155 mL/m²) over the baseline RSTSS system (2695 mL/m²). The CrSTSS configuration, when augmented with water coral fleece wicking material, yielded 5450 mL/m²—a 91 % improvement over the baseline. Further integration of paraffin wax as PCM elevated daily output to 6940 mL/m² with 59 % thermal efficiency, demonstrating superior latent energy recovery capabilities. Techno-economic analysis confirmed the optimized CrSTSS design reduces freshwater production costs by 87 %, from $0.20 to $0.026 per liter. These findings contribute significantly to advancing solar still technology for sustainable desalination applications, offering an economically viable solution for meeting clean water demands in resource-constrained environments.