Siphon-Driven Reverse Water Supply for Efficient Solar Desalination and Hydrovoltaic Electricity Generation

Abstract Freshwater scarcity poses a global challenge, and solar-driven interfacial evaporation has emerged as a promising solution for sustainable and energy-efficient desalination. However, conventional systems face critical limitations under high-salinity conditions: insufficient water supply with increasing steam generator (SG) height and rapid salt crystallization at the evaporation interface severely compromise stability and performance. Moreover, most studies focus solely on water production, overlooking the possibility of electricity generation via hydrovoltaic effects from the continuous water flow. To address these issues, this study proposes a siphon-driven reverse water transport strategy, which is implemented through a shell-shaped SG integrated with a water-absorbing wick. Capillary action lifts water to the top, after which it flows down under gravity, establishing a continuous flow cycle that ensures ample supply and uses shear force to wash away salts. The implemented system achieves a stable evaporation rate of 11.6 kg m−2 h−1 under 1 sun for 20 wt % brine, without salt crystallization during prolonged operation. Crucially, the sustained flow directly enables hydrovoltaic power generation, delivering outputs of ∼0.87 V voltage and 16.8 μW cm−2 power density for 3.5 wt % brine. This work presents an integrated freshwater–electricity coproduction system that combines efficient solar desalination with hydrovoltaic power generation, offering a promising solution for hypersaline wastewater treatment and multifunctional water–energy supply.