Researchers at MIT and Shanghai Jiao Tong University in China have developed a solar-powered desalination device that avoids salt buildup. It’s cheap enough to produce and can provide a family with continuous drinking water for only $4. “Unless it unleashes new water sources, the world will be missing 40 percent of the water it needs to strike a balance by 2030,” Antoine Walter, host of the Don’t Waste Water podcast, told Lifewire in an email interview. “Actually, few technologies enable us to create drinking water ‘out of the box’ today: desalination comes with its drawbacks, and emerging techs like atmospheric water generation still have to scale up.”
Going Solar
Many solar desalination systems rely on a wick to draw the saline water through the device, but these wicks are vulnerable to salt accumulation and hard to clean. The MIT team focused on developing a wick-free system instead. The result is a layered system, with dark material at the top to absorb the sun’s heat, then a thin layer of water above a perforated layer of material, sitting atop a deep reservoir of the salty water such as a tank or a pond. At 2.5 millimeters across, these holes can be easily made using commonly available waterjets. “There have been a lot of demonstrations of really high-performing, salt-rejecting, solar-based evaporation designs of various devices,” MIT professor Evelyn Wang said in the news release. “The challenge has been the salt fouling issue that people haven’t really addressed. So, we see these very attractive performance numbers, but they’re often limited because of longevity. Over time, things will foul.” Translating the team’s concept into workable commercial devices should be possible within a few years. The first applications are likely to provide safe water in remote off-grid locations or disaster relief after hurricanes, earthquakes, or other disruptions of normal water supplies. “I think a real opportunity is the developing world,” Wang said. “I think that is where there’s the most probable impact near-term because of the simplicity of the design.” But, she adds, “if we really want to get it out there, we also need to work with the end-users, to really be able to adopt the way we design it so that they’re willing to use it.”
A Thirsty World
There’s an urgent need for drinking water in many countries. More than 1 billion people lack access to water and 2.7 billion experience water scarcity, according to the nonprofit World Wildlife Fund. One innovation that could help provide more drinking water is reverse osmosis, a water purification process that uses a partially permeable membrane, Gerald Joseph McAdams Kauffman, the director and associate professor at the University of Delaware Water Resources Center, said in an email. The method is energy-intensive but that issue can be offset with the use of low-cost solar and wind erected at the treatment plant footprint. “We’ll also need innovation in disinfection of drinking water to remove bacteria and pathogens to replace chlorination which has been used effectively for a century now and eliminated the scourges of cholera and diphtheria but can be replaced with safe, solar-powered UV light,” he added. Innovations are also needed to eliminate contaminants in drinking water, Amy Dindal, the director of environmental research and development at Battelle Memorial Institute, said in an email. Existing drinking water facilities use treatment methods that remove per- and polyfluoroalkyl substances (PFAS) PFAS from the drinking water, she said. But these treatment methods also generate a secondary waste stream. “New technology to regenerate the treatment methods on-site, such as Battelle’s GAC RENEW system will extend the life of treatment systems and reduce the total cost of ownership for facilities that operate drinking water treatment systems,” Dindal said. A good first step to preventing water shortages would be to stop losing 136 trillion liters of water a year on network leaks, Walter said. “Digitization of networks and leak detection tools such as radar associated with new approaches to network management could actually save the world $37 billion a year, just by solving the low-hanging fruits,” he added.
