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A Fresh Supply - Engineers testing cheaper method of desalination |
Their water desalination project built with $100,000 National Science Foundation grant, is nearly complete at the Natural Energy Laboratory on Hawaii at Keahole Point on the Big Island.
Patrick Sullivan, president of Oceanit Laboratories, said the "hurricane tower" is his brainchild and that of John Craven, former University of Hawaii/director of ocean studies and retired chief scientist for the Navy.
If the process works well as he and Craven expect, the technology could be beneficial in a range of situations:
Several units placed on a barge could provide a relatively cheap mobile desalination unit for military use.
Hurricane tower units could provide needed fresh water in developing nations and on remote Pacific Islands where fresh-water resources are limited.
The system could be used to provide drinking water in natural disasters and other emergencies.
More testing would be needed, but the system might also have applications beyond desalination, such as in extracting potable water from contaminated water sources, he said.
Sullivan and Craven studied the action of a hurricane in carrying very moist warm air from the ocean's surface to high elevations, where it condenses in the cold and develops into rainstorms.
The Natural Energy lab has a series of pipelines. Some collect water near the surface of the ocean, which is warm. Some bring cold water from the deep ocean off Keahole. The Oceanit project uses both.
Sullivan said they've built a structure that looks like a silo. They'll introduce sun-heated warm water into a pool at the bottom of the silo. Cold water will circulate through pipes at the top. Fresh water will condense onto those cold pipes the same way it condenses on the outside of a chilled glass of iced tea on a hot day.
But Sullivan and Craven are adding another factor. To increase the efficiency of the system, they'll use the equivalent of a big fan to start the air spinning inside the silo, creating a mini-hurricane. It should create an area of low pressure over the pool of water, enhancing evaporation and carrying the moist air up very quickly.
"It could go up to 100 miles an hour, but we expect it to be about 60," Sullivan said.
Once started, the spiral motion of the air should require little energy to keep going, he said.
The process still needs a lot of experimentation and fine tuning to discover what wind speed is best, what salt water temperatures produce the most fresh water and other answers.
Sullivan said that the ultimate cost of the water produced by this process depends on just how efficiently the scientists are able to make the system, work. They're are hoping they can make fresh water cheaper than the price for which the Honolulu Board of Water Supply sells it.
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