Advancing pyramid solar still productivity through combined thermoelectric and air cooling techniques

The study aimed to improve the water condensation process in a pyramidal solar still through thermal techniques, focusing on Karbala, Iraq’s hot and dry climate. Various cooling methods—including air and thermoelectric cooling with water were integrated and tested in a multi-stage pyramid-shaped solar still to enhance condensation on separate glass surfaces. The system uniquely combines two cooling techniques to address the high thermal load resulting from multiple condensation surfaces. Air cooling (2–8 m/s) and water cooling (105–620 W) were evaluated. Air cooling was applied at speeds of 2, 4, 6, and 8 m/s with corresponding wattages of 80, 120, 160, and 200 W. Water cooling with thermoelectric and heat sink methods involved wattages of 105, 210, 315, and 410 W for each condensation glass, with initial solar radiation intensity measured at 995 W/m² on 24 May 2024. Air cooling increased condensation speed by up to 12% at noon, aided by the dry environment. Water temperature in the basin without cooling reached 65°C, dropping to 53.3°C with a maximum 620 W cooling power consumption. Productivity analysis showed a 48.3% improvement in the morning at an input power of 330 W, which increased to 55% at 620 W. The system achieved a maximum water productivity of 2797 mL/m², with an estimated production cost of 0.078 USD per liter. However, increased energy consumption for cooling reduced overall thermal efficiency due to larger condensation areas in the pyramid solar still requiring more energy, despite enhancing water productivity.