Wave-Powered Desalination

dptalia writes, "Scientists think they've found a way to harness the energy of waves to desalinate salt water. Currently desalination is an energy-intensive process, but this new design harnesses the renewable energy of waves to produce fresh water. Many countries depend on desalinated water to support their populations, and this invention could lower the cost of water generation." Production versions of the "desalination ducks" would be about 10 meters in diameter and 20 meters long. Each would supply water for more than 20,000 people.

Wow.

[NerveGas (168686)]

2,000 cubic meters per day of desalinated water from each unit. That's over 350 gallons per minute. Impressive!

Re:

[Rudisaurus (675580)]

I thought so too. So why do they always have to find some nay-sayer -- this Nidal dude, for instance -- who has an obvious axe to grind and is therefore completely blind to the possibilities? Scale has nothing to do with it; it's cost per unit fresh water produced that matters -- and in places where energy is scarce or infrastructure is lacking, the desalination ducks sound like an awesome solution.

Plus -- they won't plug off the way RO membranes do. :)

Re:Wow.

[by Anonymous Coward]

Why do they always have to find some nay-sayer -- this Nidal dude, for instance -- who has an obvious axe to grind and is therefore completely blind to the possibilities?

I couldn't agree with you more. They keep telling me that my perpetual motion machine will never work, but I know that I have the calculations correct! And after I patent my time travel machine and my warp engine designs I'll definitely win a Nobel prize!

I hate those people with such small minds thinking only about facts and the truth. I know how things really work, I feel it in my gut.

Re:

[dbIII (701233)]

I'm sure you have good intentions but here we have another post asking how do people with absolutely nothing do anything? The answer as always is you do what you can with what you have got or get other resources in if you can.

Its actually only 305 real gallons per minute

[Maddog Batty (112434)]

I do love Googles [google.co.uk] conversion function though. I didn't think it would work that one out OK but it did.

Re:Wow.

[grozzie2 (698656)]

It would be more impressive if it didn't require the water to be pre-heated to 100C. I think it's safe to say, pour boiling seawater into just about anything with some condenser tubes setup, and you'll get fresh water out of the condenser. It appears to be insulated with Impossiblium, you know, the stuff that'll allow it to maintain internal temperature for a month while it works, with no heat input. I'm willing to bet, read the fine print in the marketing manuals, and you will find the Mark II version will have double the production if you power it with snake oil too....

Re:Wow.

[finity (535067)]

The water that must be pre-heated is the "ballast" water. That water is already fresh water. The salt water doesn't have to be heated to 100 C, it's pulled to a low pressure with the ballast water, so it doesn't have to be heated as much.

Re:Wow.

[pla (258480)]

hell all they need is a $2 magnifying glass lens

A 20x10 meter lens for $2? Please sell me a dozen! ;-)


Actually, though, they wouldn't need to focus the light... That serves to concentrate light into a very small area to raise the spot temperature, but doesn't actually raise the temperature if you add in the area shadowed by the lens.

Just paint the tops of the ducks matte-black, and you'll get the desired solar heating effect.

Re:

[steveo777 (183629)]

A dozen? Why? Got some giant ant [horror-wood.com] problems?

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[daem0n1x (748565)]

That's about 1400 litres per minute.

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[caudron (466327)]

That's over 350 gallons per minute.

And over a full Library of Congress every three days! Wow! That's a whole lotta got-dang water!

Tom Caudron
http://tom.digitalelite.com/ [digitalelite.com]

Correction

[Maddog Batty (112434)]

2000 ((cubic meters) per day) = 117409.801 hogshead per fortnight

According to Google [google.co.uk] that is.

Stick one of these near the British Royal Family

[Timesprout (579035)]

And Australias salination problems are solved.

cool

[joe 155 (937621)]

This could be really useful in the UK, we are getting frightening low on water during the summer months to the point where we thought that we might have to go back to stand pipes. We would have the money to build something like this and the energy to heat the water (it needs to be pretty hot to do it) - I do wonder though if it would be practical for the very poor countries because of the requirements on the heat (although maybe solar could take care of that) and the cost of building them... I wonder if it will be prohibitavely high

also "One unit should be able to produce around 2000 cubic metres a day", that's pretty amazing.

Re:

[whathappenedtomonday (581634)]

This could be really useful in the UK, we are getting frightening low on water during the summer months

The UK? Yeah, very serious drought [news.com.au] there every summer... [bom.gov.au]

Re:

[cloricus (691063)]

Haha yeah...How about this for frighteningly low; in early 2008 my city runs out of water. There are no backup plans and no prospects in the pipe line at the moment, due to a rather stupid population voting on our water future based on popularity (the good looking one was the dumb one) not on science, so all 100,000 residence and twice that in the near by regions will be out of water. I hear the huge storms that hit Brisbane over the last three days are only adding a weeks worth of water to their supplies

Re:cool

[lisaparratt (752068)]

Or you could just heavily fine the water companies 'til they fix their pipes, rather than letting such huge amounts of water leak away.

Re:

[pubjames (468013)]

Except that in the UK the news about a "drought" every year is just bullshit. The UK is drowning in fresh water compared to many countries. Did you know that the UK only uses about 10% of the fresh water available to it each year?

I don't understand why a big fuss is made every year about this. Perhaps it is an attempt by the water companies to get tax breaks from the government or something, I don't know. But I find it a bit sad that so many people in the UK seem to swallow it every year.

Re:

[Fr. Teddy (171470)]

While that is strictly speaking accurate, it is of course not the full story. The vast majority of that water is in parts of the country where it is not able to be used. Perhaps a huge canal down the middle of the country might solve it - but nothing short of that would.

Oh the Irony

[MarsBar (6605)]

The inventor's name is Stephen Salter. Heh.

Why not solar?

[jonadab (583620)]

I've often wondered why solar power isn't harnessed to distill seawater. It ought to be a simple matter to hook up a glass-topped insulated-on-the-bottom pyramid or somesuch with an inlet that lets seawater in (and the concentrated result back out for that matter) whenever a larger-than-average wave passes, set it up so the seawater passes over a metal plate, add some mirrors and/or lenses to heat the thing enough to create some steam, and pipe the steam out the top and over to a shaded receptacle with a n

Re:

[will_die (586523)]

They are called solar stills [serve.com].
While easy in design they are rather expensive, require huge areas of land to produce sizable quantities of water and weather dependant. Also you cannot have moving water since it needs time to heat up so that steam is produced

Solar Stills

[Noryungi (70322)]

Actually, I happened to see one design of solar still the other day, that was touted as both cheap and small.

The design used something pretty close to a solar panel: a flat white plastic surface, with a thick, dark-tinted, glass panel. Between the plastic back of the panel and the glass, the inventor put a black felt surface, on top of a black plastic sheet. The felt that was wetted by a plastic tube in which (very) small holes had been punched to create a drip.

The felt, the plastic sheet and the glass pane

Re:

[Noryungi (70322)]

Yes, I know there is more to a solar panel than painting a piece of glass black. Happy? ;-)

However, let me point out that there are two types of solar panels out there: photovoltaics [wikipedia.org] and thermal solar [solarserver.de]. The design I was talking about is, of course, a "thermal solar" type of panel, that does not generate electricity (that's a photovoltaics) but that uses the heat radiated by the sun.

Of course, someone out there is going to say: "Aha! But thermal solar can also be used to generate electricity", to which I repl

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[salec (791463)]

Actually, the sun has already done its part - the air above the sea surface and on the shore is humid because of evaporation. Now, all you have to do is to cool a surface which is not reachable neither by sunlight, nor by seawater and to collect condensed water. A simple long, vertical, floating, white or reflective-colored metal flask could do that (as long as the sea is cooler then the air above - otherwise, a metal panel up in the air would do the trick).

Re:

[salec (791463)]

The point is: by the sea, the air *is* already humid! Just do the condensation part...

Offtopic but cool

[dbIII (701233)]

I've often wondered why solar power isn't harnessed to distill seawater.

It turns out that it isn't an easy problem to solve but there is a physicist sponsored by rotary international that is on the job with a good design (I'm sick and it's late so I can't remember even a name). With a source of reasonably hot water that does not have to be clean it can go from a trickle suitable for a village to turning out clean water in industrial quantities - even if the source is full of salt, heavy metals or bacteria

Floating all your eggs in one basket?

[Rogerborg (306625)]

All floating platforms are subject to damage or loss during storms. You don't want interruptions in your fresh water supply, ever, and you especially don't want to lose it after a big storm, exactly when you need it most. This looks like a good idea in theory, but you don't base risk management on best case scenarios.

Presumably...

[turbosaab (526476)]

A sensible installation would accompany the floating platforms with a large reservoir to act as a buffer and prevent such interruptions.

Re:

[Threni (635302)]

Perhaps you could pull them a few metres underwater during a storm?

Or even...

[stomv (80392)]

have a spare one or two on land, ready to deploy? This is a good idea anyway, since one of the ducks could fail for any other reason, leaving people thirsty. If you lose a duck to a storm, you replace it with one stored on land.

It ain't perfect, but it ain't bad either. Combine that with reservoirs (either big lake, or lots of 1 gallon jugs of freshwater at homes), and it's much better than the status quo.

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[artecco (1020333)]

I do not know what kind of platforms you reffering to, but I at least don't see any technical problems with build such plant. Within my industry (Norwegian oil&gas) we build offshore equipment and platforms, and the dimensioning of equipment are all well within what's technical achievable. Even in worst case scenarios

So since we already dimension Oil rigs and equipment for mammoth storms, freak waves and gas explosions (happening at the same time for your pleasure), I would guess it wouldn't be a proble

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[muellerr1 (868578)]

This thing is powered by waves. Bigger storm surge waves will mean even MORE fresh water!

Vitally Important

[Surasanji (938753)]

This particular type of technology could be extremely important in countries with few water sources. Say such as much of the Middle East. Israel has a single fresh water source for the entire country, the Kinnert (Or Galilee) This same freshwater sea is the water source for a great part of Jordan. Both countries have coasts on the Red Sea- and already there are massive desalinization plants there, on the Israeli side. But, what about Egypt? All the African Countries on the coast that are still pretty dry. This particular technology could also be of great use in the first world, as someone else stated, in places like England. I'm sure they aren't the only country with a water problem.

Re: Vitally Important

[ajs318 (655362)]

The problem is that you can't build anything anywhere in the UK without someone protesting. Ten years ago when they were trying to build the Newbury Bypass, the protestors (very, very few of whom actually came from Newbury, BTW) were chanting "Homes not roads". Today, the protestors are active whenever someone tries to build houses. When they tried to build factories in the past, at least the locals would generally support the effort on the basis that a new factory would bring jobs to the area. Now if you tried to build a factory, you'd get rent-a-mob outsiders protesting against it and the locals would also most probably be protesting that the factory would bring immigrants to the area.

Building a reservoir essentially involves digging a very large hole and filling it with water, incidentally drowning any cute fluffy bunnies et anal. that can't be bothered to learn to swim. (Actually, you have to do more than that; for a start, you have to undercut the hole to avoid evaporation, but we'll simplify things a little here.) So you'll get various groups of protestors turning up with their own agendas. Maybe they will be too preoccupied with in-fighting amongst the various factions ("you aren't a True Believer, you're only concerned about the value of your house and you eat m**t!" "Well you aren't even local, you've nothing to be worried about, you can just sod off back to where you came from and live off my taxes" "Yeah? Well how many diggers have you sabotaged?") to do any serious protesting.

But it's not just the protestors you have to worry about, it's the workers and working conditions. You can't dig big holes in the winter, because it rains and they just fill up with water. And you can't dig holes in the summer, because it's dusty, thirsty work; the workers need showers and drinks, but there's a water shortage on .....

Engineer

[Rostin (691447)]

Stephen Salter is an engineer, not a "scientist." The distinction can be blurry, but I think this is pretty clearly an example of engineering rather than science.

The only reason I point that out is that I'm an engineer, and I'd like credit to go where it's due. :)

Neither engineer nor scientist. An inventor.

[jetxee (940811)]

The author is an inventor [wikipedia.org] or a designer. To become an engineer he needs to take into account all the practical aspects of the implementation. Not only technical questions. Cost, producibility and serviceability should also be addressed in engineering. Once we see working implementations used in production we may call him an engineer.

However, his invention is really interesting. And I really hope to see it in production.

According to Wikipedia:

The crucial and unique task of the engineer is to identify,

Floater

[Konster (252488)]

Just use that Russian flaoting nuclear plant to heat the water up first...it'll work!

The economics are hopeless.

[Ancient_Hacker (751168)]

If you read The Fine Article, you might notice a certain shortage of facts. Like the costs. Economics are important. You don't want to waste money on schemes that are many many times more expensive than proven methods.

In general, it's not feasible to capture wave power. The stuff is too diffuse-- it takes too much infrastructure to capture too little energy to even pay back the cost of building the contraption.

It doesnt matter whether you use the mechanical energy to generate electricity, desalinate water, or make tea. You can't build a wave energy capture device that's rugged enough to survicve the storm, corrosion and other hazards at a reasonable cost.

As a starting point, let's take their (unsubstantiated) estimate of 2,000 cubic meters per day. A quick google shows that's worth about $1,000 to $3,000. Assuming the waves are active 75% of the time we could expect maybe $2,000 a day from this device. That's about $700,000 a year. Kinda impressive at first glance. But will that be enough to even pay for the gadget over time? Let's estimate, generously, that the device will last ten years. And that we can borrow money to build it at 5% interest. If it and the pipeline to shore can be built for $10 million, we need to pay at least approx $1.5 mil a year to make headway on the principal and interest. Plus the cost of staff and maintenance. We're still a factor of more than two away from breaking-even. And that's assuming no risks due to weather or unanticipated problems with new technology.

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[Alcari (1017246)]

10 years, Are you kidding? You can easily build it to last 75 or hundreds of years with proper maintenance. Take the word of a civil engineer. The moving parts may be more difficult, but I doubt it. We've got movable dams that are just about zero maintenance, that have been standing there for almost 40 years now. Of course, If you put multiple installations nearby, it saves the immense cost of laying another pipeline underwater (Probably costs more then the whole facility.) Also, funding for projects like

It is too early to set loose the economists

[dbIII (701233)]

If you read The Fine Article, you might notice a certain shortage of facts. Like the costs

It is too early for costs. If you consider reality costs are variable based upon manufacturing techniques, materials used, supply, economies of scale, administrative costs, delays by regulatory groups and other things that are not immediately apparent even after construction of the first prototype. First you find out if it can be done - then you work out how to do it well for as little as possible based on better as

Renewable waves?

[ScentCone (795499)]

the renewable energy of waves

Come on, this is supposed to be a science/engineering summary of a science/engineering article. The term "renewable" should at least mean something. Bio-fuel crops are arguably "renewable." Waves simply are. Nobody needs to re-plant our gravitational interaction with the moon once we've harvested it. Swine waste methane is not the same as tidal activity. It's the article summary, for cryin' out loud. At least get the fundamental concepts behind the word choice straight. "Renewable" isn't the same as "something other than oil."

Hmmm

[LizardKing (5245)]

As an added bonus, this could all be funded by selling the extracted salt to crisp companies.

'Bout Time

[viewtouch (1479)]

It's about time. The energy efficient, low cost derivation of safe, potable water from ocean water is one of a handful of technological achievements that is urgently needed to prevent the ongoing suffering, impoverishment and deaths of a significant percentage of people throughout our planet. Here's hoping that technology can achieve this, finally, this time.

TFA is light on detail

[hcdejong (561314)]

How about giving some numbers? kWh required for classic desalinisation of 1 l water vs. when using a duck?
How efficient can the insulation of the freshwater be when the central partition (in direct contact with the freshwater) acts as a heat exchanger?

desalination ducks

[The evil doctor Matt (847030)]

desalination ducks... Wonder if they'll use the salt to make saltine quackers...

What about waste disposal?

[cellocgw (617879)]

Unmentioned so far: what to do with the leftover salt. Unless you wait for 100% of the water to evaporate, you end up with highly salinized waste water. IIRC there are some desalinization plants in the Middle East or India, and significant "dead zones" in the ocean nearby. None of the indigenous aquatic life can tolerate raised salt levels.

Re:

[maroberts (15852)]

So long as there's a Moon there'll be a power source.

And even if there wasn't a moon, there is always the odd subsea earthquake to generate suitable waves for energy. Just think how much desalinated water a Beowulf cluster of these devices could generate from tidal waves!

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[mrjb (547783)]

What happens after a couple of years of having this duck farm and the water contains a slightly larger percentage of minerals? Simple. This will not happen. As the water is used and/or evaporates, eventually it find its way back to the sea, restoring the salt balance.

Ocean Thermal Energy Conversion ..

[rs232 (849320)]

"As long as the temperature between the warm surface water and the cold deep water differs by about 20C (36F), an OTEC system [nrel.gov] can produce a significant amount of power."

was Re:This is a life saving innovation