A Multiphysics Modeling Framework for Productivity Enhancement in Solar Stills

Abstract

Water scarcity remains a critical global challenge, particularly in arid and semi-arid regions, where access to clean water is limited. Solar stills offer a simple and sustainable desalination solution; however, their productivity is inherently low. This study presents a multiphysics modeling framework to investigate passive enhancement strategies for solar still systems, capturing the coupled heat and mass transfer processes governing evaporation, including conduction, buoyancy-driven convection, radiation, and phase change. The analysis focuses on the integration of vertical rods and wick-assisted evaporation to enhance heat redistribution and effective evaporation area. A detailed parametric study was conducted to evaluate the influence of rod geometry, wick thickness, surface emissivity, and material properties on system performance. The results show that productivity is primarily governed by the effective evaporation area rather than temperature alone, with the optimized configuration increasing the evaporation area by 86%. This configuration achieved productivity enhancements of up to 84% under fall conditions and 97% under winter conditions. Seasonal analysis revealed that the enhancement mechanism is more pronounced under low solar radiation, where the wick acts as an additional heat-absorbing surface, while under high radiation conditions the basin water becomes the dominant driver of evaporation. An economic evaluation demonstrated that the optimized design reduces the cost of produced water from 0.14 USD/L to approximately 0.113 USD/L. These findings confirm that the proposed passive enhancement is technically effective and capable of reducing the cost of water production in solar desalination systems.