Innovative Experimental Investigation of a Pyramid Solar Still with Air-Cooled Single Glass for Enhanced Water Productivity

Abstract

A pyramidal solar still was modified to boost its water production with an external air impeller. This impeller improved condensation by directing airflow over a designated condensing surface. Separate water collection channels were installed for each glass surface to compare productivity. The improvement came from enhanced heat transfer due to increased airflow. Experiments used air velocities ranging from 2 to 8 m/s, with corresponding power consumption of the impeller being 80 W to 200 W. The temperature decrease on the condensing surface was directly linked to the airflow speed. The biggest temperature drop (4.75°C) occurred at 8 am on the unmodified glass, but this coincided with low solar radiation (631 W/m²) leading to low productivity. The most significant productivity increase, particularly in condensation, happened between 10 am and 11 am, with a rise of up to 33%. This improvement is attributed to moderate air temperatures and relatively high solar radiation during that time. Overall, directing airflow over the condensing surface resulted in a single-surface productivity increase of 2.7% to 10.5%. The daily water yield of the modified solar still improved by 1.8% to 7% compared to the unmodified one. However, the thermal efficiency of the modified passive solar still (MPSS) decreased with increasing airflow. It started at 48.5% with 2 m/s airflow (80 W) and dropped to 39.5% at 8 m/s airflow (200 W).