Effect Of Water Basin Depth on The Thermal Performance of The Double-Basin Solar Still Under Iraqi Climatic Conditions

This work investigates the effect of water depth on the productivity and thermal efficiency of a double-basin solar still (DBSS). The lower basin measured 0.4 x 1 m, while the upper basin, installed above the lower basin’s glass cover, consisted of six sub-basins. Water depths in both the lower and upper basins were studied, ranging from 10 to 30 mm. The double-basin solar still DBSS configurations are denoted by two values, where the first value represents the lower-basin water depth and the second value represents the upper-basin water depth. For comparison, a single-basin still with base dimensions identical to the two-basin still was constructed. The experimental results obtained under the climatic conditions of Baghdad, Iraq (33.3° N, 44.3° E) in October 2025 are as follows: The best DBSS configuration was the 10-10 mm DBSS, which produced 8.75 L/m²·day and 83.24% daily thermal efficiency. The minimum productivity and daily thermal efficiency were for the 30-30 mm DBSS, that is, 5.138 L/m²·day and 71.59%. The maximum improvement in water productivity of the 10-10 mm DBSS was 37.5%, and the minimum of the 30-30 mm DBSS was 19%, compared to single-basin solar still SBSS at 10 mm water depth. The improvement in the daily thermal efficiency of the 10-10 mm and 30-30 mm DBSS was 24% and 12%, respectively, compared with the SBSS at 10 mm water depth. The maximum moisture content for the lower basin of the 10-10 mm DBSS was 700 g/kg dry air at 12 hr, while it was 520 g/kg dry air for the upper basin. The maximum temperature was recorded on the lower basin glass cover of the 10-10 mm DBSS, reaching about 90 °C.