Development and testing of a vertical solar still Original Research Article

Solar distillation of brackish water is a practical alternative which offers life to those regions where the lack of fresh water hinders development. It has been shown that solar distillation remains the most favourable process for the supplying of water to small communities in remote locations where there is solar radiation as arid zones of Algeria. In arid zones of Algeria, man has depend on underground water reservoirs for fresh water requirements, but the use of water from such sources is not always possible on account of the presence of salt. When the demand of fresh water is not large, solar distillation is a suitable process. In this paper a development and testing of a vertical solar still prototype fabricated at solar station of Adrar: latitude 27.88°, longitude 0.28° and at an elevation of 360 m over sea level, has been described. The aim of our research work has been to devise a vertical solar distiller for arid zones, that should be very simple, hardy, easy to maintain and repair by every skilled village artisan with limited technical means. There is little information published in literature about vertical solar stills, some are constructed and tested in Australia, USA and Thailand. A prototype solar still having a vertical flat absorber of 0.817 m2 was designed, constructed and tested outdoors. It is constructed using locally available materials as well as local technical assistance. The total area of glass covers is 0.8769 m2, the absorbing surface consists of a set of a parallel black porous cloths wick plate located in an enclosure. The still is formed by a vertical absorbing surface, two transparent glass covers and a vertical back wall made of galvanised iron, darkened with black colour internally and covered externally with 5 cm of glass wool as insulator. Raw water from a constant head tank was feed on the top of the edge of the absorbing plate. Collecting through were provided at the lower edges of the inner surfaces of the vertical cover glass. Solar radiation, after passing the cover, is absorbed in the porous cloths and cause evaporation of water. Water vapour then condenses on and flows down the cover into collecting through. The work has led to the development of the vertical solar still and to a technical improvement. In order to achieve high yield of distilled water the still orientation should be the direction at which the highest average incident solar radiation is obtained.