Bob McDonald's blog: Researchers propose a new idea for harvesting fresh water from ocean air
Science thrives on new ideas, and a new study published in the journal Nature last month has floated an ambitious proposal for supplying much-needed drinking water to arid regions near the ocean. It involves inventing a new technology to capture moisture-rich air rising off the surface of the ocean, and condensing it into fresh water.
If the researchers' idea pans out, it just might be an alternative to energy-intensive and environmentally problematic technologies like desalinization, but there's a long way to go to make it a reality.
Fresh water is becoming a rare commodity in areas such as the coastal southwest of the U.S., where years of drought have lowered reservoirs to dangerous levels. Much of the region's groundwater has been overexploited, and is not being replenished; additionally, the glaciers and snowpack that have supplied rivers are threatened.
The eastern Mediterranean, Middle East, South Africa and Western Australia are all plagued by similar issues, as arid regions that lack fresh water, but have an ocean of undrinkable water right next door.
Researchers at the University of Illinois Urbana–Champaign are proposing that we tap into a huge source of fresh water that evaporates from the surface of the oceans, even in drought-stricken areas.
Their rough idea is to design and deploy large collectors, similar in size to a big oil rig, which would use fans to suck up moist air that naturally evaporates from the ocean surface. Set up several kilometres offshore, machinery would then pump the water-laden air to land. There, the air would flow into condensers, where it would be cooled so that the moisture condenses as fresh water.
The researchers suggest the condensers and pumps could be powered by clean energy sources such as wind and solar.
This is analogous to what nature does as part of the natural water cycle. When water vapour evaporates from oceans and lakes, it rises in the atmosphere, where it cools to produce rain. The proposed solution is also not terribly different from the household dehumidifier you use in your basement — expanded to a massive scale.
The team calculated that one of these units could satisfy the daily potable water needs for about 500,000 people, at a cost comparable to desalinization. And it wouldn't create the concentrated waste stream of salt and toxic metals produced by desalinization plants.
Now to be clear, they've built nothing — the study is a proposal with some informed, but not tested, ideas about a potential solution, as well as the associated complexities and costs. So this is all very hypothetical, but it suggests we could access large amounts of fresh water from a very large, untapped source.
And water is a special kind of resource. Unlike oil, which can be replaced with alternatives, we cannot live without water. Wars have been fought over other resources; the last thing we need are water wars. Rather than fighting over dwindling sources, nations could work together to tap a bountiful new supply of fresh water for the future.
It's a big idea, but it might be a great idea, too, and we're in dire need of those as we deal with our environmental and population struggles.
ABOUT THE AUTHOR
Bob McDonald is the host of CBC Radio's award-winning weekly science program, Quirks & Quarks. He is also a science commentator for CBC News Network and CBC-TV's The National. He has received 12 honorary degrees and is an Officer of the Order of Canada.
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