Parameters influencing the productivity of solar stills - A review

In this paper, a review is made on the various parameters influencing the productivity of the solar stills. The researches on the factors improving productivity such as area of absorption, minimum depth of water, water-glass cover temperature difference, inlet water temperature, heat storage, phase change materials, vacuum technology and other methods such as using reflectors, condensers, multi effect distillation, etc. are discussed here. The review showed that the productivity increases when the area of the absorption is increased. The basin water depth is the main parameter that affects the productivity of the still. The increase of the water-glass cover temperature difference (Tw−Tg) also plays a vital role in increasing the productivity. Preheating the feed water to the still basin shows a considerable improvement in the productivity. The studies showed that solar stills with heat storage medium and phase change materials can produce distillate during off-shine hours (nocturnal distillation) and thereby, enhance the productivity. Maintaining vacuum conditions and the use of reflectors and condensers improves the performance of the solar stills. Various modifications in the solar stills such as weir type stills, multi effect distillation, thermoelectric cooling, inclined type stills, etc. enhanced the productivity of the solar stills.