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A Clever New Approach To Desalination
jbeaupre writes "The Economist reports on progress by a company called Saltworks on using saline gradients to do the heavy lifting of desalination. In essence, Saltworks uses solar energy or waste heat to concentrate sea water. They then use the ionic gradient between the concentrated brine and two sea-water streams to pull ions from from a 3rd sea-water stream. It appears to work with entropy by trading the reduced entropy of the desalinated water against the increased entropy of 'mixing' the brine and the other sea-water streams. The article only discusses Na and Cl, but even just removing these ions is a step in the right direction."
Thinking about desalination makes me remember that episode of "The Voyage the Mimi" in which they used the process to make drinking water:
http://video.google.com/videoplay?docid=-524069894840499801# (A/V's not synced)
Freedom is drinking a beer in the park when you're supposed to be at work.
Except for that last absurdly inaccurate statement (made me chuckle), this sounds really good. Not the fastest way to desalinate, so it would take an awful lot of these to meet demand (or one really gigantic one), but still this could be at least a partial solution.
Caveat Utilitor
Desalinization is most likely the wave of the future, given the rise in sea levels and melting ice. We might as well put the extra water to good use, rather than just let our low-lying lands drown.
Yeah, pretty much, for all practical purposes, but not quite, because sooner or later the fucking sun will in fact burn out.
You didn't need to read TFA. It's in the summary. Second sentence.
# cat
Damn, my RAM is full of llamas.
OK between this and the General Fusion guys http://www.generalfusion.com/ Canada has got water and energy completely licked. http://www.saltworkstech.com/ OK actually I'm still trying to run the numbers on the both of them (and waiting for some peer reviewed publications.)
Not really. The article clearly indicates that heat input is required (i.e. it doesn't purport to be a system that produces more energy than is put into it). The beauty of this system is that this energy is obtained from a source we don't have to pay for (i.e., the sun).
Other than the fact that they are consuming not producing energy, yeah exactly like that...
Yeah, pretty much, for all practical purposes, but not quite, because sooner or later the fucking sun will in fact burn out.
Or get bought out by Oracle after giving away all its energy for Free.
When information is power, privacy is freedom.
Comment removed based on user account deletion
The key piece of the work is an ion bridge. This has to permit the travel of one kind of ion but not the other, i.e. Na+ or Cl-. Looks like this material could be expensive. It might plug up need to be periodically replaced. How expensive these are? How non toxic these are? What is needed to manufacture them? These are the questions we need to ask.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
anyone else think this looks suspiciously like: http://en.wikipedia.org/wiki/Perpetual_motion
Only if you can't read.
There are no tiger attacks in my area and it's all because this rock I'm holding keeps the tigers away.
T
Laws are horrible moral guides, moral guides make even worse laws.
Thank you for that link to General Confusion. Made my day. Check out the freshman T-rex with his lava lamp and the sordid diatripe:
http://www.generalfusion.com/fossil_fuel_crisis.php
The planet was covered with dense clouds and the atmosphere contained a high concentration of carbon dioxide, producing tropical conditions north of the 45th parallel. For example, many dinosaur fossils were excavated in Alberta, Canada. As the earth's crust cooled down, volcanic activity reduced.
Riddle of Burgess Shale's fossil-rich deposits solved
The site, close to the B.C.-Alberta border, is considered crucial to understanding the so-called Cambrian "explosion" of life - a time when the future Canadian land mass was drifting in tropical climes close to the Earth's equator.
In my historical atlas, the equator is considerably south of the 45th latitude. The dinosaur fossils in Alberta are equatorial in origin. But hey, if you can't get that right, no obstacle to solving the fusion problem. Like it's not a hard problem or anything. The typical Alberta fat cat oilman probably doesn't believe in plate tectonics to begin with. Just a bunch of mud we turn into money. Now they're all excited about version 2: just a bunch of water we turn into money.
BTW, the Royal Tyrrell Museum in the Alberta badlands is pretty kick-ass if you're into bones.
And we could freeze a bunch of it and ship it to the poles.
I prefer rogues to imbeciles because they sometimes take a rest.
From the way they describe it, it sounds a lot like Maxwell's Demon. Since there is energy going into the system, however, it's clearly not that.
There ain't no such thing as a free Sun.
I feel like a single-celled organism subsisting on a decomposing lunch for only a few seconds.
Isn't this a large-scale demonstration of the same principle used in home reverse-osmosis systems? It sure sounds familiar.
(i.e. it doesn't purport to be a system that produces more energy than is put into it)
"Perpetual motion" doesn't produce necessarily "more" energy than is put into it. It simply doesn't require energy at all apart from the initial "push". And that is, of course, absolute rubbish, thanks to friction, diminishing returns, and any other number of physical laws that favor entropy.
I just don't understand how this project is meant to work. Maintaining those "concentration gradients" is going to take more energy than just sunlight. Yes you could vary the volumes of the "pools" (and thus the amount of evaporation) to help maintain your concentrations within a given range. However eventually you are going to have to flush the whole system and start again, since it will always tend towards equilibrium. And if you started with salt water, equilibrium is NOT fresh water.
Human kidneys (something I know about as a doctor), for example, use salinity gradients to concentrate urine and also remove necessary salts - after all you don't want to be literally pissing all of your sodium, potassium and calcium away without SOME sort of control. However this control requires energy, in the form of ATP, and LOTS of it. This is one reason the kidneys are one of the most sensitive organs to oxygen deprivation, after the brain and the heart (but even heart muscle can take a beating - the problem there is more one of inadequate blood supply rather than oxygen demand) - even though the kidneys receive 20% of the body's blood flow. They NEED it to survive, because they consume tremendous amounts of oxygen to produce enough ATP to maintain all those gradients.
Frankly I think the article is badly written - probably intentionally especially if the inventors "think they're on to something" - and I fail to understand how it works on a fundamental level. But kudos to them if they're right. I guess we'll find out how it really worked in a few years. Or not.
Seven puppies were harmed during the making of this post.
... is if it would be possible to combine solar-thermal power generation with desalination.
Build Fresnel-lens solar concentrators and stick them near a source of seawater. Boil the water using the sunlight, and use it as the working fluid in an ordinary steam-turbine-type power generator. But instead of recycling the same water once the steam recondenses, realize that you've just made a giant distiller: drink the water and use "new" seawater.
Does the word "nigger" actually personally offend you? Or do you avoid it and frown on its use because you feel like you're supposed to? Real question, and maybe as an AC you can give a truly honest answer.
The word doesn't offend me. I avoid it because I realize that others may be offended by it, and I do not understand the complex history of its word. Besides, there are plenty of other ways to refer to other human beings besides the color of their skin. Consider their first and last name, for instance.
It's also,important to remember that it does not have to denote a race or skin color. I tend to evaluate people based on their actions, and I have learned that the epithet could be applied to many of the people that post flamebait as AC. You are what you do, this is your hood, and your question is just some more mostly worthless graffiti. I say mostly worthless because it DOES show YOUR true color, no matter your race.
I was thinking, "In this house we obey the laws of thermodynamics!"
Seems pretty simple to me. The ions flow down their concentration gradients creating opposite charges in streams that were once regular seawater, through some sort of bridge that only allows Cl ions into one stream and Na ions into the other stream. Then the seawater that needs to be desalinized is connected, the ions can't escape the charged streams due to their bridges, but the ions from the seawater to be desalinized travel to the charged streams. After that, you dump the charged streams and start over again. About the only thing I'm not sure on is the last part, as I imagine the ions would flow due to the charge and not be permitted to flow due to their concentration gradient due to the nature of the bridges?
Anyway, the first part certainly is simple enough to understand from a physiology perspective. Hell, thats how the action potential works. Create an imbalance using energy(ATP in the body, sunlight in this example) and then use semipermeable membranes to create a charge.
-The world would be a better place if everyone had a hoverboard
The winter in Poland is already plenty cold enough...
:-P
Cheers,
"What in the name of Fats Waller is that?"
"A four-foot prune."
This idea of ion bridges has been around a long time. The application here is basically misrepresented. All it is doing is replacing a small amount of commercial electric power with solar-generated potentials. But the process isn't feasible when run on commercial power, even if the power is free, so replacing the commercial power with solar (the germ of the "idea" here) is just disguising the dead horse. Reminds me of the algae gambit: the solar constant crossed by photosynthesis is dismal, so no biofuel (corn ethanol, biodiesel, etc) can possibly be effective, but if you photosynthesize with algae, the very irony of pond scum making something useful is enough to make you (briefly) forget physical limits. Notional fantasies vs genuine engineering.
Just like it takes energy to desalinate water the opposite is also true: energy can be produced from salinating water.
See http://en.wikipedia.org/wiki/Osmotic_power
What this system does is to concentrate seawater by evaporation and then use the salinity gradient between that concentrated brine and normal seawater to produce energy. This energy is then used to desalinate another stream of seawater. In principle, there is no reason to use this energy specifically for desalination. It could also be fed to the grid.
Is there anything inherently more efficient in using energy derived from osmotic power for desalination compared to using electricity from any other source? The answer to this question will probably determine whether this process can have any real benefits over the alternatives.
One potential advantage is that this system uses only ion flows and not electron flows. AFAIU, using electricity would have resulted in unwanted electrolysis byproducts which this system elegantly avoids. There is also no need for any power conversion circuits, wires, etc.
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
Ice displaces water, which will just make the sea level even higher, you bloody fool !
I've long wondered about a few things when it comes to desalination, desert areas etc.
If it's cheap to make water with this process and remove the salt - would it be a good idea to create a huge bunch of these machines in desert-areas, pumping desalinated water into fields to promote vegetation to grow, fighting back the desert? I would think this wouldn't require the water to be further cleaned, after removing the salts..
Am I completely off my rockers, or is it a maybe-sort-of workable idea?
"Rune Kristian Viken" - http://www.nwo.no - arca
Yes I got THAT part. What I don't get is how they plan on maintaining this potential difference across the membrane. In the human body it's done by Na/K ATPase pumps that trade 2 sodium atoms for 1 potassium atom. But these pumps are working all the time (even during depolarization, when the Na gates open), and consuming ATP all the time. It's ACTIVE transport, and requires a lot of energy. That's why neurons die when deprived of oxygen after only 4 minutes, while other tissues can survive hours.
I find it hard to understand that this phenomenon will just "happen" by itself under bright sunlight. There's diminishing returns to consider. As you start moving ions out of your brine and combining them with the fluids on either side, through diffusion gradients or electrical gradients, the difference in concentration/charge will decrease and an equilibrium is reached. And as I stated before, I doubt that that point will result in "fresh" water. Oh I can see "less salty" water, but not fresh water. Now if I take that less salty water and repeat the process n times, perhaps I could get relatively fresh water - but how many times does the system have to be flushed or reset, and who's counting all the energy required to do this?
Like I said, the article is vague. There's no numbers to run. Maybe it works, and good for them. But I doubt it's a miraculous process - just slightly more energy efficient.
Seven puppies were harmed during the making of this post.
The source of the energy to evaporate the water is irrelevant, solar works just as well for either process. Assuming an essentially unlimited supply of seawater for cooling to the distillation step, I don't see how they can make enough concentrated brine to filter the seawater more cheaply.
Your body has to pump the salt because it's going from a low concentration gradient (blood) to a high concentration gradient (urine). Obviously. This is just the opposite. In each side, one ion is going down a *major* concentration gradient (20% to 3.5%), while the other ion is going up a *minor* concentration gradient (0% to 3.5%). So entropy favors the reaction, and it will continue until the ions run out from the freshwater; you're ending in both a lower entropy and energy state. The key is that you have to create that major concentration gradient (20%), which is a lower entropy state. That's done through evaporation.
The advantage of this process over evaporating it and condensing it (say, with a transparent roof) is building and maintaining a pond with a transparent roof costs about 10x more than building and maintaining an empty pond. Glass costs a fortune and can be damaged. Plastic is cheaper, but it has to be thick enough to withstand the elements and it photodegrades, meaning it has to be replaced every several years.
Look at me, still talking while there's science to do.
I think the answer is cost. Near where I live a company makes table salt. They have acres and acres of these shallow ponds, and when the tide comes in they open the valves, filling up the ponds. Then they close the valves and wait for a few days for it all to dry into this muddy slush that gets scooped up by heavy machinery and, I hope, purified.
Aside from the land itself the entire operation is so cheap it's almost free. Sure, you could somehow trap that water vapor and cool it enough to change it back to a liquid, but the increase in cost would be enormous on a percentage basis.
Well... Then we'll stack it up on the continents!
Semi-automatic amateur armchair Australian philosopher; conjecture ready at any moment...
i'm curious about your sig - what does it mean? I can't quite figure it out...
(1.21 gigawatts) / (88 miles per hour) = 30 757 874 newtons
Not an expert, but from what I've seen (on shows like World's Toughest Fixes, etc.), modern steam turbines are very sensitive to impurities. Even the size of water droplets matters. Running seawater vapor through one would probably not work without a redesign.
That's the beautiful thing about water based catastrophie! Too much is as bad as too little.