Review of researches and developments on solar stills

Single-effect solar still is a simple solar device used for converting the available brackish or waste water into potable water. This device has many advantages like, easily fabricated from locally available materials and cheap maintenance with low skilled labor. A lot of works were undertaken to improve the productivity of the still. Throughout the review on solar still performance, the results indicated that, the basin water depth is considered the main parameter that affects the still performance. Also the review showed that; the solar still cover with inclination equal to latitude angle receives sun rays close to normal sun rays throughout the year. The still productivity also increases with decreasing the cover thickness and increasing its thermal conductivity. The still basin material plays an important role in improving the productivity of the still, rubber basin was considered the best used material in improving the absorption, the storage and the evaporation effects. The previous studies also showed that, the daily production of still was greatly enhanced by using sponge cubes, fins and stepped. The coupling of a solar collector, hot water tank, external reflector, internal condenser and greenhouse with a still increased the productivity. Finally; from the previous efforts it was clear that; using the sun tracking is more effective than the fixed system in enhancing the still productivity; also the PCM is more effective for lower masses of basin water on winter season.

Research highlights
► Review of research and development on solar stills is presented in this paper.
► The coupling of a solar still with a hot water tank generally doubles the free water.
► The coupling of a solar collector with a still has increased productivity by 24–36%.
► The PCM is more effective for lower masses of basin water on winter season.
► The concave solar still efficiency reached about 45%.