Improving the performance of double slope solar still with external reflector: Thermodynamic analysis and water production

Access to clean drinking water is an increasing global challenge due to population growth, industrialization, and environmental deterioration. Solar stills have garnered attention as promising technologies for water purification because they are sustainable, environmentally friendly, and cost-effective. However, their performance is often limited by suboptimal thermal management and low evaporation rates. To address these limitations, this study develops a two-dimensional numerical model using COMSOL Multiphysics to investigate a double-slope solar still equipped with an actively rotating external reflector. The model simulates coupled heat and mass transfer processes and is validated against experimental data, enabling a comprehensive analysis of thermal behavior and distillate yield. Simulation results demonstrate that optimizing the reflector angle significantly enhances the temperature distribution within the desalination chamber, leading to a 9% increase in pond water temperature and a 5.5% rise in glass cover temperature. Moreover, adjusting the reflector's angle results in a 36.4% improvement in daily freshwater productivity. The simulation outcomes closely match the experimental findings, with a maximal deviation below 7%. In conclusion, the integration of an actively rotating external reflector substantially improves the performance of double-slope solar stills by maximizing solar flux concentration, boosting evaporation rates, and increasing overall output efficiency. This approach provides a promising strategy for sustainable and efficient freshwater production in regions with high solar irradiance.