Boosting Solar Distiller Performance Using Floating Polystyrene Balls to Lower the Basin’s Water Surface Tension: 4E Analysis

Solar distillation offers a sustainable solution to global water scarcity, yet its efficiency depends on optimizing thermophysical properties like surface tension. This study introduces a novel approach to enhance conical solar still performance using floating polystyrene (PS) balls to reduce water surface tension, a previously unexplored method. Unlike chemical surfactants, hydrophobic PS balls disrupt water molecule cohesion, lowering the energy barrier for evaporation without risking contamination. We investigated the impact of PS ball color (white and black) on distillation performance through experiments conducted at El-Oued University, Algeria, on June 30, 2024. Three conical solar stills were tested under identical conditions: a simple conical solar still (SCSS), one with white PS balls (CSS-PB&W), and one with black PS balls (CSS-PB&B). The CSS-PB&B achieved a cumulative yield of 6.35 L·m⁻²·day⁻¹, a 29.59% increase over the SCSS (4.90 L·m⁻²·day⁻¹), while CSS-PB&W yielded 4.40 L·m⁻²·day⁻¹, a 10.20% decrease due to poor sunlight absorption. Black PS balls also improved thermal and exergy efficiencies to 86.88 and 6.27%, respectively, compared to 79.14 and 2.96% for SCSS. Economically, CSS-PB&B reduced the cost per liter to 0.048 $ L⁻¹ (4% interest rate), and environmentally, it mitigated 22.78 tons CO₂ year⁻¹, 1.30 times that of SCSS. These findings highlight the potential of black PS balls to optimize solar still performance through combined surface tension reduction and thermal enhancement, offering a sustainable solution for freshwater production.