To a researcher like Kripa Varanasi, an associate professor of mechanical engineering at MIT, a big nuclear power plant similar to the one that generates electricity near Cape Town, South Africa, is a fountain of water just waiting to be tapped.

The 1,800-megawatt Koeberg Station drinks in water from the nearby Atlantic Ocean and uses it as part of its thermal cooling cycle. Just as in other industrial settings, cooling towers are an inherent part of the power plant’s steam cycle. As the reactor heats ultra-pure water to create steam to spin a turbine and generate electricity, a cloud forms and rises from the cooling towers, akin to the plume of “steam” that wafts from the brim of a hot cup of coffee.

And with Cape Town—a city of more than four million people—facing a nearly existential crisis due to a drought that began in 2015 and that could see the city run out of potable water as soon as next year, Varanasi sees an opportunity for his remarkably simple technology.

He and colleagues from a new startup plan to demonstrate later this year at MIT’s main power plant that much of the vapor plume can be captured and turned into drinking water. The technology is expected to work at a low cost, both in terms of capital equipment and energy.

The idea of capturing water droplets from the plume of fog is nothing new. Existing systems tend to consist of little more than a screen door-type mesh structure stretched across the path of a fairly reliable fog bank. But these passive systems capture only a frustratingly small amount of water, as little as one to three percent of the plume, Varanasi said. That’s because moisture-laden air currents tend to travel around and not through the mesh screen material, carrying precious water droplets with them. (Read more and watch a video showing how the technology works.)