Improving the performance of stepped solar still

• The experimental study including the comparison between the conventional still and stepped still with improvement
• The hot air passes under the base of stepped still used to heat the saline water
• Use of aluminum filling as thermal storage material beneath the absorber plate
• The effect of water flow over the glass cover was studied.
• The productivity of stepped still with improvement increased above 120% over conventional still.

In this paper, the experimental performance of a stepped solar still coupled with a solar air-heater was investigated. A single slope passive solar still (conventional still) and stepped active solar still integrated with a solar air-heater collector were fabricated with an area of 0.5 m2. The hot air from the solar air heater passes under the base of stepped still used to heat the saline water. The higher saline water temperature was achieved by the active stepped solar still compared to the passive solar still due to the additional thermal energy supplied by hot air. Use of aluminum filling as thermal storage material beneath the absorber plate keeps the operating temperature of the still high enough to produce distillated water during the lack of sunshine, particularly at night. Also, the effect of water flow over the glass cover was studied. Results showed that, water productivity increased by 112% over conventional still, when the system was coupled with a solar air-heater and glass cover cooling, for stepped solar still. The productivity of the stepped still is increased by integrating aluminum filling by about 53% over conventional still.