Enhancing the stepped solar still performance using a built-in passive condenser

In this study, an improved stepped solar still with a built-in passive condenser is proposed and experimentally investigated. In the new design, the solar still body is divided by a central inclined stepped absorber assembly carrying a group of basins into two parallel chambers; The upper chamber is an evaporation chamber, and the bottom chamber is called the condensation chamber and is located on the under of the absorber assembly. Solar radiation heated the saline water and evaporated it. A fraction of the resulting vapor is condensed on the inner glass cover surface while the rest is naturally circulated to the condenser chamber to be condensed there. Air is naturally circulated between the chambers through two slits at the bottom and the top of the absorber assembly. The improved stepped solar still (ISS) was designed and fabricated, and its performance was experimentally evaluated under Kerman climatic conditions in June and October. For comparison, a standard stepped solar still (SSS) with the same size and properties is also constructed and tested. Results show that for the same condition, the daily yield of the improved stepped solar still is 30% to 150% higher than the standard stepped solar still. Also, the daily efficiency of the ISS reached as high as 36%. The influence of brine water flow rate and glass cover thickness on the performance of the stepped solar still is also investigated. Finally, the cost of distillate water for the improved stepped solar still and standard stepped solar still is estimated.