Pyramid floating solar still with enhanced condensation surfaces operating under actual weather conditions

The potential solution offered by floating solar still (FSS) to water scarcity confronts challenges associated with condensate droplet loss and structural instability under oceanic and swaying condition. A novel pyramid FSS with reduced wettability surfaces (silicon nano-coated) was proposed, utilizing central symmetry structure of pyramid to reinforce the stability and adopting nano-coated surfaces to enhance the condensation. A 4-day outdoor experiment was conducted to evaluate the performance. The highest yield of nano-coated FSS was 1.017 kg/m2/d under an accumulated irradiation of 15.166 MJ/m2/d, which was 16.76 % higher than that of uncoated FSS. Furthermore, the yield of nano-coated FSS was 0.949 kg/m2/d in the river experiment, showing a significant improvement. Next, the enhancement of nano-coated surface on droplet collection was numerically analyzed, showing that the condensation droplets could retain their complete shape until detachment. In contrast, the detachment process on the uncoated surface involved a separation of neck, leaving a residue of liquid behind. Quantitative analysis showed longer movement distances and faster travel velocities for droplets on the nano-coated surface, and these two improvements could facilitate condensate collection. Furthermore, the cost analysis reveals a CPL of 0.129 $/L for the proposed FSS, suggesting its affordability for off-grid communities.