Offshore structures could harvest city drinking water from ocean air

It’s a cruel irony that over 70% of the Earth’s surface is covered in water, but it’s undrinkable. Scientists at the University of Illinois Urbana-Champaign (UIUC) have now modeled the feasibility of a hypothetical system that can capture water vapor from above the ocean surface and condense it into fresh drinking water, at a large scale.

Water scarcity is an ongoing issue that’s projected to only get worse, as climate change makes dry areas even drier. The oceans, home to over 96% of all water on Earth, represents a huge potential reservoir, but desalination is a tricky prospect to scale up thanks to the toxic wastewater it produces.

But nature already has a pretty efficient desalination system in place – the Sun is constantly heating up the surface of the ocean and evaporating water out of it, which of course goes on to become rain. In a new study, the UIUC team devised a method to potentially tap into this resource.

The team proposes that structures could be built several kilometers offshore to capture air rich in water vapor from above the ocean surface. That air can then be piped back to land and condensed in another unit. This fresh water could then be used for drinking, agriculture, or whatever else a region needs it for. The whole system, according to the scientists, could be powered by offshore wind farms and land-based solar panels.

The researchers evaluated 14 cities around the world, including Abu Dhabi, Rome, Los Angeles and Barcelona, analyzing how much water could feasibly be extracted based on the offshore atmosphere in those locations. This would involve building water vapor-extracting structures standing 100 m (328 ft) tall and 210 m (690 ft) wide.

Based on their models, the scientists found that these devices could generate between 37.6 billion and 78.3 billion liters of water per year, depending on the conditions in a specific location. The team then calculated how many structures would be needed to provide enough water for the populations of each city, based on an assumed usage of 300 liters of water per person per day. From this, as few as two or as many as 10 units could provide enough water to service a city.

The team says that the solution is fairly elegant, since it essentially works like the natural water cycle except that the vapor is guided to where it’s needed. And while many proposed drinking water sources could become less feasible as climate change progresses, this one should actually get even better.

“The climate projections show that the oceanic vapor flux will only increase over time, providing even more fresh water supply,” said Afeefa Rahman, co-author of the study. “So, the idea we are proposing will be feasible under climate change. This provides a much needed and effective approach for adaptation to climate change, particularly to vulnerable populations living in arid and semi-arid regions of the world.”

Of course, this idea is still wildly hypothetical, but it’s an important area to consider and further studies could explore the feasibility further.

The research was published in the journal Scientific Reports.

Source: UIUC

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