Freshwater is necessary for all life on Earth, but water scarcity caused by climate change, pollution, and rising human demand makes it increasingly difficult to get. Water shortages affect over two billion people worldwide. According to UNICEF, by 2025, that figure might have risen to half of the world’s population. According to research conducted in 2019, over half of the United States’ 204 freshwater basins would have monthly shortages by 2071.
Of course, there is one enormous supply of water that spans 70% of the planet: the ocean. Unusable saltwater is transformed into freshwater using a filtering process known as desalination. It’s a technique that’s been used mostly in the Middle East, but it’s also becoming more popular in water-stressed areas of the United States, notably California.
One important issue that desalination systems confront is the fouling of equipment caused by salt accumulation, which necessitates frequent cleaning of device parts or replacement completely if damaged. In quest of a solution, researchers at MIT and Shanghai Jiao Tong University in China created a solar-powered desalination device that prevents salt accumulation and may provide a family with continuous drinking water for as little as $4.
The researchers describe their new invention in a new paper published on Monday in Nature Communications: a floating, low-cost, solar-powered desalination device that takes advantage of a natural phenomenon known as convection, which is the tendency of fluids (and gases) to rise to the top when heated and sink when cooled.
While typical desalination systems use a wick to pull salt and other impurities from the water via a device, the researchers devised a wickless, multilayer method. The bottom layer is perforated with small holes, which drive water up toward the upper layer, which is constructed of a dark substance that absorbs sunlight. Water at the surface is warmed by the sun’s rays, evaporates, and accumulates as potable water on a condensed surface. The salt that remains after the water evaporates runs down through the microscopic holes to the bottom layer.
According to Evelyn Wang, a mechanical engineer at MIT and co-author of the new work, this perforated layer allows for convection by permitting “natural convective circulation between the warmer top layer of water and the cooler reservoir below.”
The researcher’s test apparatus ran for a week without showing any evidence of salt buildup. When the researchers subjected the gadget to circumstances resembling waves on an ocean or a lake, it performed admirably and remained steady.
So now, this is only a proof of concept on a bench, but the researchers intend to evolve their technology into something that can be mass-produced and utilized by people and families, particularly those living in isolated regions. These gadgets might potentially be used to deliver clean water during disaster relief operations.
The study team also believes that the device’s solar power, which has been demonstrated to be 80% effective in converting solar energy into water vapor, has the potential to create concentrated steam that may be used to aid sterilize medical items in remote regions.
“I believe the developing world represents a significant potential,” Wang remarked. “Because of the simplicity of the design, I believe that is where the most likely influence will be felt in the short future.” [However], if we truly want to get it out there, we also need to engage with the end-users to ensure that they can adapt the way we design it and are eager to utilize it.”