"Water From Air" is the best applied science I've seen all year

YouTube link.

I first heard about this development in a BBC podcast of Science in Action where Dr. Varanasi was interviewed.

A new system devised by MIT engineers could provide a low-cost source of drinking water for parched cities around the world while also cutting power plant operating costs.

About 39 percent of all the fresh water withdrawn from rivers, lakes, and reservoirs in the U.S. is earmarked for the cooling needs of electric power plants that use fossil fuels or nuclear power, and much of that water ends up floating away in clouds of vapor. But the new MIT system could potentially save a substantial fraction of that lost water — and could even become a significant source of clean, safe drinking water for coastal cities where seawater is used to cool local power plants.

The principle behind the new concept is deceptively simple: When air that’s rich in fog is zapped with a beam of electrically charged particles, known as ions, water droplets become electrically charged and thus can be drawn toward a mesh of wires, similar to a window screen, placed in their path. The droplets then collect on that mesh, drain down into a collecting pan, and can be reused in the power plant or sent to a city’s water supply system.

The system, which is the basis for a startup company called Infinite Cooling that last month won MIT’s $100K Entrepreneurship Competition, is described in a paper published today in the journal Science Advances, co-authored by Maher Damak PhD ’18 and associate professor of mechanical engineering Kripa Varanasi. Damak and Varanasi are among the co-founders of the startup, and their research is supported in part by the Tata Center for Technology and Design.

Most people are aware of the way fog or mist condenses into water droplets on a mesh or screen (or on the bodies of insects in the Namib Desert or on redwood trees).  A power plant tower is basically creating distilled water - all you have to do is harvest it.  The principle has been demonstrated in a laboratory setting; now it's being scaled up.  It's cheaper by a log power than fashioning new desalination plants.

Reposted to add an image and text from a more recent BBC report:

If the emerging ‘water from air’ (WFA) devices can crack it, it could go a long way towards solving the world’s freshwater problem...

There are several companies adapting dehumidifier technology for drinking water. Mechanical dehumidifiers contain chilled metal coils filled with a refrigerant gas, much like a kitchen fridge-freezer, which create an artificial ‘dew-point’ (the temperature at which water vapour in the air saturates, turning from a gas into a liquid, like the beads on the side of your ice-cold drink). Water vapour entering a WFA machine condenses on a chilled coil in the same way, but once collected it is filtered, sterilised by UV light, mineralised, and stored in a food-grade tank ready to drink...

There are, however, some important conditions for many of these devices to function at their best. The efficiency, for instance, often depends on the relative humidity – the amount of water present in air, as a percentage of the amount needed to reach saturation. For most of the devices, that figure is above 60% for optimal functioning...

But a new UK company, Requench, is entering the market later this year (2018) with a unit literally the size of a shipping container, and it can reportedly function at a relative humidity of just 15%. The prototype produces 2,000 litres a day in humid conditions and no less than 500 litres even in dry climates.

Another solution may come from entirely different WFA technology. Instead of refrigeration coils, a ‘desiccant’ material absorbs water from the air like a chemical sponge, needing no energy to do so... “You need something that absorbs water at ultra-low humidity, even 5% humidity. For example, when you leave the lid off the sugar bowl, it gets kinda clumpy. Sugar is a natural desiccant...

But there is one more WFA approach that requires zero electricity – solar or otherwise – and is designed for the poorest regions of the world. In rural Ethiopia, Togo, and soon Haiti, stands the near 10-metre tall ‘Warka Tower’. Looking like something from Glastonbury Festival, a giant vase-shaped bamboo frame supports hundreds of square metres of fine polyester mesh. The mesh collects the morning mist and drips down into an underground tank via a stone-based filtration system... Such dew harvesting, however, relies on very high humidity and fog.