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.

Comments

Wow.

[NerveGas]

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

Re:Wow.

[pla]

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.

Floating all your eggs in one basket?

[Rogerborg]

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.

Vitally Important

[Surasanji]

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:cool

[lisaparratt]

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

Presumably...

[turbosaab]

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

Or even...

[stomv]

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.

The economics are hopeless.

[Ancient_Hacker]

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.

Re:The economics are hopeless.

[Anonymous Coward]

You are making two assumptions that aren't necessarily true.

First, that water is cheap. It may be where you are, but there are many countries where water is scarce. Australia and Israel, for example. Water starts becoming insanely expensive once you have low supply and high demand. It's not like we can do without it.

Second, that the objective here is to make money. How about providing enough water so the population don't all die?

There is often no alternative - in Australia, dams don't work well because there just isn't enough rain, for example. The electricity grid can't cope with the load that's already put on it, especially on the east coast, and there's not enough land near the sea for a solar-powered desalination plant. Something like this would be great. We just need to get the government to pay for it.

Oh, and if you have water supply entirely in private hands, you're just asking for trouble.

Renewable waves?

[ScentCone]

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."

What about waste disposal?

[cellocgw]

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.