In the face of growing water scarcity, engineers are turning their attention to the atmosphere as a potential source of liquid gold. Even in the Atacama Desert, renowned as the driest place on Earth, fog and dew are estimated to yield a significant amount of water. Globally, the atmosphere holds a vast reservoir of water, estimated to be equivalent to the volume of Lake Superior, which is projected to increase by 27% over the next 50 years due to evaporation driven by global warming.
Harnessing this atmospheric water is essential, as over 2.3 billion people currently reside in water-stressed regions, and droughts are anticipated to displace millions more in the coming years. Atmospheric water harvesting is not a novel concept; the Inca utilized buckets to collect condensation from fog, while in the Canary Islands, certain trees are known as “fountain trees” for their ability to capture moisture.
Modern atmospheric water harvesting systems employ fine polymer mesh sheets as condensation traps, which attract tiny water droplets that eventually flow into a reservoir. A team led by Urszula Stachewicz at AGH University of Krakow has enhanced the productivity of these sheets by incorporating an electrical charge that attracts water droplets, resulting in a 50% increase in water yield. Further improvements were achieved by adding titanium dioxide to the mesh, which enhances its water-attracting properties under certain conditions.
In regions with limited fog, alternative solutions are necessary. One approach involves leveraging the water already present in the air through radiative cooling. As temperatures drop, the air’s water-carrying capacity decreases, causing water to condense onto surfaces, forming dew. This technique is particularly effective in arid regions with clear skies, high daytime temperatures, and cool nights.
Combining radiative cooling with superhydrophobic coatings eliminates the need for electricity to remove water droplets from collection surfaces. While promising, this technology faces challenges related to inefficiency, with current prototypes producing only 1.6 liters of water per kilogram of lithium chloride over ten hours in very arid conditions.
Despite these limitations, these technologies hold immense promise for providing sustainable water sources in arid regions. They offer the potential to transform even the driest landscapes into habitable environments, providing communities with a vital resource for life and prosperity.
