Enhanced productivity in stepped solar stills: An experimental comparative study of brine flow rates, absorber-glass distances, and cooling mechanisms

This experimental study evaluates the performance of a stepped solar still under various operational conditions aimed at enhancing productivity and thermal efficiency. The investigation focuses on the impact of different inlet water flow rates, glass-absorber spacing, the implementation of a condenser, and the cooling effects of glass cover using fan and water. The experiments are carried out in winter and summer. Results show that increasing the flow rate from 3 to 6 L/m 2 /day in winter improves productivity by 3.5%, then the productivity decreases by 14% at a flow rate of 9 L/m 2 /day. The performance of the solar still in summer is similar to it in winter and the daily production has been effective in the inlet flow rate up to twice, consequently, the optimal flow rate of 6 L/m 2 /day in winter and 10 L/m 2 /day in summer are used for different cases. Further, A solar still with collector-to-glass distance of 8 cm obtains a 15% higher efficiency in winter compared to a 12 cm-distance. An artificially forced convection of air using a fan at an average velocity of 2.5 m/s increases productivity by 2% in winter and 1% in summer. But, using a 5 mm-thick water film reduces the productivity. • The performance enhancement of stepped solar still is investigated experimentally. • Effect of glass-cover distance, cover cooling, condenser and flow rate are studied. • Optimal brine flow rates are found 6 L/m²/day in winter, 10 L/m²/day in summer. • The absorber-glass distance of 8.8 cm achieves the highest efficiency of 82.6%. • Forced convection with a 2.5 m/s fan enhances yield by 2% in winter, 1% in summer.