Enhancing the vapor condensation efficiency of a solar water purifier by rapid heat dissipation to bottom bulk water

Abstract

The solar-driven interfacial photothermal evaporation-based water purification process has become a promising sustainable strategy for clean water production. However, conventional evaporation-based solar purification suffers from the limited efficiency of the subsequent vapor collection due to the very low heat dissipation from the vapor to the outside ambient air. Here, we designed an efficient vapor condensation device via dissipating the heat mainly to a metal Al array-based condenser and finally to bottom bulk water. As the metal Al and bottom bulk water have thermal transfer capabilities that are tens to hundreds of times greater than those of the cooling medium air and glass cover in the conventional device, we achieved a greatly enhanced vapor condensation rate of 1.16 kg m⁻² h⁻¹ (0.8 kW m⁻²) with a vapor collection efficiency of 75.7%. Our bottom bulk water cooling device can stably generate clean water during a nine-day continuous self-floating experiment on a lake surface, with a water generation rate of around 8.09 kg m⁻² d⁻¹, indicating that it represents a passive and simple device for practical water supplementation via direct placement and self-floating on the surface of a body of water.