A $4 desalination system provides continuous clean drinking water for a family

The new device employs a method that reduces harmful salt buildup.
Chris Young
The researchers' setup during tests.MIT

A team of scientists developed a new affordable method for solar-powered desalination that stops the build-up of salt seen in similar devices, a blog post from MIT reveals.

For the cost of only four dollars, a 10.8 ft2 (1 m2) model of the new device can provide daily clean drinking water for a family. It's also built using easily procured everyday materials, meaning the system is scalable and can be deployed to many people across the globe.

Tackling the world's water shortage problem

Water scarcity could affect half of the world's population by 2025, according to UNICEF. In fact, four billion people — almost two-thirds of the world's population — are already affected by severe water shortages for at least one month per year.

The researchers from MIT and Shanghai Jiao Tong University developed a solar desalination device without a wick — a part that typically needs a lot of cleaning or even replacing due to a buildup of salts. By doing so, they believe they have built a system that could help to address the world's water shortage problem with unprecedented efficiency.

The new device — outlined in a paper published in Nature Communications — is comprised of several layers that float atop a container of saltwater. Firstly, a thin layer of material with tiny perforations draws up a sliver of water from the container and dark material that absorbs heat from sunlight then evaporates this water, which is condensed and collected as drinkable water. The holes in the perforated material are just large enough to allow "for a natural convective circulation between the warmer upper layer of water and the colder reservoir below," the MIT researchers explain in their statement. In other words, a little warm salt water remains behind after the process, which is then naturally drawn into the rest of the cool water below where it becomes diluted.

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Bringing clean water to remote locations and disaster relief efforts

The researchers explained that the technique is more than 80 percent efficient at converting solar energy into water vapor with water that has up to 20 percent concentrations of salt. What's more, after a week of use, no fouling — harmful salt buildups that could damage or reduce the efficiency of the device — was detected. 

Desalination systems have the potential to bring clean drinking water to areas that currently suffer from water scarcities. Last year, the world's first wave-powered desalination system was powered up, and a designer, Henry Glogeau, won the Lexus Design Award for his desalination light system for remote locations. The MIT and Shanghai Jiao Tong University also said their system could be easily and quickly deployed in areas affected by natural disasters, helping disaster relief efforts worldwide.

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