Experimental evaluation of a hemispherical solar distiller incorporated with a dish collector, V-corrugated basin, wick layer, nanofluid, and cover cooling

Freshwater scarcity, combined with the relatively low productivity and high unit water cost of conventional hemispherical solar stills, limits their practical deployment in decentralized desalination. This study experimentally investigates a reference hemispherical solar still and a modified configuration that combines parabolic dish-based feedwater preheating with four successive performance enhancements: a V-corrugated basin (Case 1), a wick layer to promote thin-film evaporation (Case 2), a carbon black nanofluid to improve solar absorption and heat transfer (Case 3), and external cover cooling to intensify condensation (Case 4). Experiments were conducted under comparable outdoor conditions while monitoring solar intensity, wind speed, ambient temperature, basin and cover temperatures, freshwater yield, and energy and exergy indicators. The main findings are: daily freshwater production increased from 3.39 L/m² for the conventional distiller to 7.17, 8.44, 9.67, and 10.87 L/m² for Cases 1–4, respectively, corresponding to a maximum gain of 220.7 % in the fully modified configuration; cumulative thermal efficiency improved by up to 114.0 % and exergy efficiency by up to 288.7 % relative to the reference still; the cost of produced water decreased from 0.0146 $/L to 0.0095 $/L, while the exergoeconomic factor rose from 2.62 to 7.29 kWh/$ and the exergoenvironmental factor from 0.91 to 5.37 tons of CO₂. Overall, the integrated use of geometric optimization, wick-assisted thin-film evaporation, nanoparticle-enhanced absorption, and cover cooling in a dish-preheated hemispherical solar still delivers substantial technical, economic, and environmental benefits, underscoring its potential as a sustainable solar desalination solution.