Wave-powered Edinburgh Duck desalinates seawater
By Darren Murph 
posted November 8th 2006 12:06PM
posted November 8th 2006 12:06PM
Sure, in theory we could use the LifeStraw to purify enough water to quench the thirst of thousands of people, and if Aqua Sciences proves successful in its endeavor to pull water out of thin air, desalinating the seas could prove unnecessary. Nevertheless, Stephen Salter at Edinburgh University in the UK is working with a research team to perfect the "Edinburgh Duck" and provide useful water for needy individuals. The desalinating critters convert wave energy into pressure changes that aid the collection of pure water (in the form of steam) from seawater; by lowering air pressure, the system can draw steam from water at lower temperatures. The pressure-driven machines operates sans electricity by using the crashing motion of waves to operate its innards in a "piston-like motion," slowly but surely creating salt-free water that's pumped back ashore through the two legs that tether the duck to the seabed. Although current prototypes are only pumping air, finalized units could be 10 meters in diameter and 20 meters long -- a device large enough to supply water for "more than 20,000 people." While we're sure the targeted audience here is arid countries with good access to seawater, those days at the beach would be much more enjoyable without generous helpings of NaCl finding their way into our mouths.[Via Slashdot]
Okay, I've been an avid Engadet reader for sometime, and I feel that I can safely say that this is the weirdest article you've ever posted. Does anyone else see it that way, or is it just me?
I think the PS3 is weird.
"While we're sure the targeted audience here is arid countries with good access to seawater, those days at the beach would be much more enjoyable without generous helpings of NaCl finding their way into our mouths."
Actually, this would theoretically increase the NaCl levels in the oceans/seas. If you're removing just H20 from an H20/NaCl mixture you're increasing the NaCl content.
Engadget - stick to the report, not the logic that may ensue.
You couldn't be further from being right. Not only is there such a vast amount of water on this planet that desalination won't make a huge impact on salt concentration, but also water is constantly redeposited through various means back into the ocean, reverting the salt concentration to normal.
You people need to use your heads instead of finding something wrong with the article to make you feel good about yourselves.
If this extracts water from the ocean, "those days at the beach" would be much LESS, not more, enjoyable since the salt concentration of the ocean will be higher.
Yes, and when we desalinate the water from the oceans completely, it'll be 904200 A.D. Idiot.
-C
That's right Fred. Because once water is taken from the ocean, it never returns. Fred you are a twit.
Heard of the water cycle - water in, water out. Considering 97% of the earths water is stored in the oceans, and all water will eventually run to the oceans, the fresh water this supplies will simply run through a person/a field/an animal and filter through the ground and into rivers back to the sea. Whether it will increase pollution levels (more water = more potential for pollution runoff) is a different story.
The main issue here is that the localised area around the duck is likely to becoming very saline. However, if the water was collected by ship and released gradually as the ship moved then that would provide a means of stopping it. However, that is unlikely to happen :D
christopher, you're the idiot. The blog post implies that this would be a good idea at the beach because it would make the beach water less salty. The device would make the beach water more salty.
I never said that the whole ocean would be affected. Only the local beach water would be affected.
I knew it! Stephen Salter works with my dad - anything to do with wave power and desalination always involves him...
If this actually goes anywhere, then it might work... :D
and if I had an arm that could reach anywhere in the world, Id slap you for being so obvious.....
Its a sweet idea. Go Scots.
This is nuts. If you desalinate the ocean, it will disturb the aquatic habitat, meaning more endangered/extinct species. I feel as though humans are the least considerate beings of all...
Your point would be true if the ocean didn't have currents. DUH
It's glad to see that us Scots haven't totally abandoned our ingenuity. It's also excellent to hear that a viable solution to water has been found for the poor African nations!
As much as your point does and some truth behind it, there is still issues.
Ocean currents cannot move all the water within an area and spread it out. Most ocean currents carry water down a very specific path, and carry the same water very long distances. If anything, ocean currents would make the effect worse, as if the desalination duck was in an area with a high speed ocean current, that current may take the super-saline solution huge distances.
http://en.wikipedia.org/wiki/Desalination#Environmental for more information on the environmental costs on ecosystems.
And of course, ocean currents tend not to run 10km from the shore.
more like Stephen de-Salter... if you catch my drift
Bunch o' Idjuts.
To double the salinity in an area you'd have to remove enough water to fill same area. You'd have to remove hundreds of thousands of tons of water to have even the slightest effect on the local salinity. And, yes, ocean water moves. Look up studies on the movement of sand from beach erosion. That happens because the water is moving and mixing whether or not there are nearby major current.
Extracting water from air is already possible. This is a product from Hyflux that extracts water from the atmosphere and it is already on sale.
http://www.hyflux.com/pdt_aquovate.html
fellipe, while I sympathise with your concerns I really feel that this is unlikely to affect the surrounding ecosystem much. The ocean is massive, by any measurement. Realistically this is not much different than a warm water current resulting in heightened evaporation and rain on areas such as Britain or the "Wet" coast of NA. The Oceans are no more salty there than in other areas. What this allows is for countries with a lcak of adequate drinking water, such as many coastal middle eastern states and African countries, to draw drinkable water off the ocean.
As for the concentrated salty water the ducks will produce, this will make the water heavier than the surrounding water making it sink and mix with the rising water replacing it.
Over all I would argue that the effects of a human population on the local ocean shores are a lot more apparent than the reduction of salinity in the same waters. Since this damage has already occured and that the human population in that area is unlikly to move on we can justify slight rises in the local salinity of that water as well in order to provide potable water to this population.
I congratulate the Scots for this invention.
You may also want to remember that the melting ice-caps are freshwater...