Optimization of the geometry of a solar still

Abstract

The functioning of a solar still is governed by two combined phenomena: (i) a component in the mixture is brought up to evaporation by absorption of solar radiation; (ii) the respective vapor is condensed onto a colder surface from where pure liquid is collected and extracted to the outside. An optimal solar still geometry emerges from the trade-off between the area allocated to collect solar radiation and the area allocated for vapour condensation. In this paper we show that the geometry of the still can be optimized so that the heat transfer by the condensing surface to the environment is maximized under some functional constraints. The optimization is constrained by a fixed solar still bottom area (geometry parameters such as the inclination and the length of cover and lateral surfaces are allowed to vary) and is conducted for a solar still situated in Évora.