Battery Turns Saltwater Into Drinking Water 114
An anonymous reader writes "German researchers have developed a battery that can remove sodium and chloride ions from seawater. In theory, their invention could be far more energy efficient than thermal desalination or reverse osmosis. This would cut the cost of using salt water for drinking or irrigation. It could also be used to make compact desalination systems for boats and life rafts, or crops. Each battery is made with manganese oxide nanorod electrodes, which absorb sodium when an electrical current passes through them. When the current is reversed, they dump the sodium ions out into waste water."
How much energy? (Score:5, Interesting)
Re:How much energy? (Score:0, Troll)
Re:P.S. First! (sorry, I couldn't resist!) (Score:2, Informative)
Please do. Help End the Dumb First Post meme.
(Dr. Emmett Brown) "According to my calculations, the nature of the First Post directly influences the quality of the entire thread. When a really good First Post is made, the quality of the thread increases between 25-75%, because in most neutral (non flame bait) stories, once the "famous first slot" is taken, and then there are some five to seven good replies, trolls don't bother as much with low grade slots down farther in the chain. The improvements to the quality include a 20% drop in "Slashdot sux" comments too.
(/Dr. Emmett Brown)
Say what you like about those awesome back to the future movies, Doc Brown was awesome because his math was almost never wrong.
Re:P.S. First! (sorry, I couldn't resist!) (Score:1)
(Dr. Emmett Brown) "According to my calculations, the nature of the First Post directly influences the quality of the entire thread.
Perhaps in the future but I don't think this is true today.
Re:true today. (Score:2)
It's definitely Non-Random, and positive. That's why I threw a big range at it.
The easy way to look at it: In those second tier stories that only get some 40 comments, a couple of typical Forrest Posts will waste about 10 comments all by themselves.
No less than NYCL himself complained about this problem, in that story updating us on his ReDigi client.
Re:P.S. First! (sorry, I couldn't resist!) (Score:2)
Maybe the priviledge of the first post should go to the article submitter or someone with meta-moderation status?
It's "privilege" not "priviledge" (Score:0)
The origin of the word is the Latin privilegium - from privus ‘private’ plus lex, leg- ‘law.’
Re:P.S. First! (sorry, I couldn't resist!) (Score:3)
Comment removed (Score:2)
Re:P.S. First! (sorry, I couldn't resist!) (Score:2)
Re:P.S. First! (sorry, I couldn't resist!) (Score:0)
I, for one, welcome our post-scripting-first-post second-posting thread lords.
Re:How much energy? (Score:2)
Sweet Irony... a +5 post followed by a Troll post. Now it just needs to be down-modded to -1.
And it wasn't a troll or flame bait. Redundant would be a better mod.
I think Slashdot needs more mods tho.
More +1's and more -1's.
Re:How much energy? (Score:2)
Re:How much energy? (Score:5, Informative)
They call it a battery because it is a series of electrical cells. The term "battery" means the series arrangement; it comes from a military term for a series of guns. Generating electricity is the best-known use of an electrical battery, but isn't the definition.
Re:How much energy? (Score:5, Informative)
As with " battery hens", few readers will know what "battery" means in that context.
Cannon artillery analogies are as obsolete as ballista analogies.
Re:How much energy? (Score:1)
Uncle Tom: "No. Some of them run off the mains."
-- The Goodies [wikipedia.org]
Re:How much energy? (Score:0)
So then what's Beowulf cluster of batteries? Is that when a 'series' of cells operate in 'parallel'?
Re:How much energy? (Score:2)
Re:How much energy? (Score:1)
Batteries do not generate electricity. They simply STORE electricity and make it available for use. Batteries need to be recharged by other devices which do generate electricity.
Re:How much energy? (Score:3)
It's "an electrochemical cell that can desalinate seawater".
You can thank Aaron Rowe for calling it a battery. I'm sure he plays with his food with his feet.
Re:How much energy? (Score:5, Informative)
Actually, the authors call it a battery in their paper. [acs.org] And it is.
Here's the salient part of the paper:
In this work, we demonstrate a novel electrochemical cell named a “mixing entropy battery”, which extracts energy from the difference in concentration of two solutions and stores it as chemical energy inside the electrode material’s bulk crystal structure. This approach allows us to overcome the challenges of supercapacitor electrodes based on activated carbon. This device consists of a reversible electrochemical system where the salts in the electrolyte are the reactants and the electrode stores ions. We employed two different electrodes: an anionic electrode, which interacts with Cl ions selectively; and a cationic electrode, which interacts with Na+ ions selectively. These electrodes are initially submerged in a low ionic strength solution (river water) in their discharged states, when the electrode materials contain the respective ions incorporated in their structures. In this dilute solution, the battery is charged by removing the Na+ and Cl ions from the respective electrodes (Figure 1a, step 1). Successively, the dilute electrolyte is exchanged for a concentrated solution (seawater), which is accompanied by an increase in the potential difference between the electrodes (Figure 1a, step 2). At this higher potential difference, the battery is discharged, as the anions and cations are reincorporated into their respective electrodes (Figure 1a, step 3). The concentrated solution is then removed and substituted by the dilute electrolyte (river water), which results in a decrease in potential difference between the electrodes (Figure 1a, step 4). We note that the exchange of solution could also be carried out via a flow process, which could be attractive for large scale energy extraction.
Re:How much energy? (Score:2, Funny)
Sounds like a prima facie case of A Salt and Battery...
Re:How much energy? (Score:5, Interesting)
What I'd really want to know is if it is more efficient to use a solar panel to charge the battery to then separate the salt or simply to use the sun to desalinate the water using the tradition process.
Re:How much energy? (Score:1)
Re:How much energy? (Score:5, Informative)
Seriously?
We already do utilize the water that falls from the sky, you know those river things that run into the ocean and most communities were built around?
Water is finite, even that magic skywater. Upstream communities cannot take all the water they want, as downstream communities rely on the same water source. Desalinization technologies not only allow coastal communities to grow where there isn't a major river, but also frees up water for greater upstream use.
Re:How much energy? (Score:2, Offtopic)
Water is finite
No it isn't. In an infinite universe, nothing is finite. Water on earth is finite, even if there is an enormously huge amount of it. But water isn't used up; there is as much water as there ever was. The trouble is its management, not its quantity.
Re:How much energy? (Score:1)
So you believe in the Sam Kenison method of eliminating world hunger:
http://www.youtube.com/watch?v=vN7ehccspao&feature=related [youtube.com]
Re:How much energy? (Score:2)
You sound like you been smoking too much fucking dope.
Re:How much energy? (Score:0)
Actually, you can and it works pretty well. My area went through a near-decade drought, and I installed six rain barrels for outdoor watering. Now with a quarter inch of rainfall, I collect nearly 200 gallons.
I wouldn't drink the water, but it's fine for watering trees and bushes.
Re:How much energy? (Score:2)
Re:How much energy? (Score:5, Informative)
Nonetheless, I don't know how they propose to be more energy efficient than a mirror-based distillation rig. Besides keeping the parabola aimed at the sun, which requires negligible energy, the main costs of running such a rig are keeping it supplied with water to distill and flushing it out with solvent once in a while to prevent salt buildup. (You can even use filtered seawater for the solvent.) The latter costs seem unavoidable for electrical-cell-based desalination, and the former is, as I said, negligible.
Of course, it only works in parts of the world that get a lot of sunshine, so for example it would be a non-starter in northern Ohio. (Not that we need desalination in Ohio. Most of our water management issues involve finding ways to get the water to drain away more efficiently so it doesn't flood our basements; that seems likely to be common in places that don't get enough sunshine to boil water with a parabolic mirror... but I suppose there could be exceptions.)
Re:How much energy? (Score:5, Funny)
Of course, it only works in parts of the world that get a lot of sunshine, so for example it would be a non-starter in northern Ohio.
I think the fact that Ohio is not near any source of saltwater would be the real non-starter.
Re:How much energy? (Score:0)
Re:How much energy? (Score:0)
Re:How much energy? (Score:2)
Of course, it only works in parts of the world that get a lot of sunshine, so for example it would be a non-starter in northern Ohio.
I think the fact that Ohio is not near any source of saltwater would be the real non-starter.
Love how you excised the OP's context-clarifying statement that said, "Not that we need desalination in Ohio"
Still pretty darn funny, though
Re:How much energy? (Score:1)
Granted.
Re:How much energy? (Score:2)
That depends on your definition of "generate". Generators don't create energy either, they just convert it from kinetic energy. Batteries (except rechargeable batteries) just convert chemical energy to electricity.
Re:How much energy? (Score:2)
Re:How much energy? (Score:1)
Well, thermodynamics preaches that nothing generates energy.
Re:How much energy? (Score:5, Informative)
Interesting, but how much energy does it take to run this thing? (they call it a 'battery', but I don't think it actually generates electricity).
Re-read TFA. They came up with this desalination gizmo by reversing another gizmo that does create electrical energy.
I think this's brilliant thinking. They didn't just read the paper. They read it, understood its implications, and extrapolated them in the opposite direction. That's what I expect from scientists. I wish I saw that kind of thinking more often.
As for this gizmo, I'd like to see it built as a group of looping boxes, progressively yielding purer product as it goes through them in sequence. Add other boxes in the chain to filter out other stuff that this gizmo doesn't filter, and you end up with an office water-cooler machine that produces pure water and recyclable sludge. I'd definitely buy one!
Re:How much energy? (Score:0)
Actually, the whole understanding the implications and building something based on isn't science, it's engineering.
Science investigated phenomena; Engineering makes use of those phenomena.
Re:How much energy? (Score:3)
Actually, the whole understanding the implications and building something based on [it] isn't science, it's engineering. Science investigated phenomena; Engineering makes use of those phenomena.
Engineering is a superset which includes science. Engineering isn't engineering without the scientific component.
Is the LHC science or engineering, or both? NASA? :-)
Re:How much energy? (Score:2)
The theory is the science; applying it is the engineering.
Re:How much energy? (Score:2)
The theory is the science; applying it is the engineering.
I think we're getting pretty close to splitting hairs here (or arguing about how many angels can dance on the head of a pin).
Some of the !@#$ NASA does looks like engineering ("implementation"/engineering), but they're really just making it up as they're doing it ("inventing"/science). Ditto, LHC.
It's a fine line, is all I'm saying.
I'm not trying to diss either engineers or scientists, btw. I love 'em both for what they bring to the table. I'm personally more comfortable around engineers, but I (not so secretly) idolize scientists.
Mmmm, Samantha Carter, mmmmm, ...
Re:How much energy? (Score:5, Informative)
From the abstract: "Here, we demonstrate an energy consumption of 0.29 Wh lâ"1 for the removal of 25% salt using this novel desalination battery, which is promising when compared to reverse osmosis ( 0.2 Wh lâ"1), the most efficient technique presently available."
Re:How much energy? (Score:3)
Isn't this similar to electrodeionization?
Re:How much energy? (Score:3)
Yes, though the closest analogue is probably electrodialysis reversal [wikipedia.org]. The difference is that no existing technology has been able to economically remove salt in concentrations as high as seawater (though they have been used for brackish water).
Re:How much energy? (Score:2, Informative)
Very pure water is bad for you, as it leeches good minerals out of your cells (reverse reverse osmosis, if I'm not mistaken aka osmosis). If your desalination does too good a job, you have to "cut" that water with impure water.
Re:How much energy? (Score:3, Insightful)
Passing pure water through plumbing is a bad idea since it would dissolve all sorts of bad stuff (some places still have lead pipes so they need "hard water") and then you'd drink it... And drinking pure water without taking enough salts and minerals in your diet would cause problems. But that doesn't prove it's bad for you. That's like saying fruits are bad for you because you're not getting enough calcium from them.
And I've had RO and distilled water that wasn't actually pure - some had the taste of acetone, some had some other weird acrid taste. So if the study is not done correctly with actually pure water you might be poisoning the animal/human with the impurities. The problems might not be the pure water.
You want enough minerals, eat more sardines with bones for calcium and a potato/banana for potassium.
Re:How much energy? (Score:5, Informative)
A report reviewing some of the research as of 1980: Health Risks from Drinking Demineralised Water [who.int].
Re:How much energy? (Score:0)
Re:How much energy? (Score:0)
Fortunately, "very pure water" isn't "very" pure by the time it gets into contact with permeable cells, having been mixed with your stomach contents and blood...
Re:How much energy? (Score:3)
Re:How much energy? (Score:3)
From the abstract: "Here, we demonstrate an energy consumption of 0.29 Wh lâ"1 for the removal of 25% salt using this novel desalination battery, which is promising when compared to reverse osmosis ( 0.2 Wh lâ"1), the most efficient technique presently available."
My first impression was that this is was largely just an academic project / exercise, there are other way more interesting applications for these nanorods. 15 times the energy to remove only 25% of the salt? geez, I guess it works, but not to make potable water in any quantity.
Reverse osmosis is already deployed at a comparatively low cost, and scales very well, I don't see this or anything else displacing that as a desalination process any time in the near (or even somewhat further) future.
Re:How much energy? (Score:2)
Interesting, but how much energy does it take to run this thing? (they call it a 'battery', but I don't think it actually generates electricity). Many of the places that are short on fresh water are also short on electricity (especially "green" energy), so this may not be as helpful as it sounds.
True, but there are many countries that would be all agog if it would work more efficiently than reverse osmosis, places where salt water is abundant but drinking water is scarce, and energy is (relatively) abundant; think Persian Gulf states, north africa coastal states etc.
Almost there! (Score:5, Informative)
Not sure what math they're using when 50% removal of ions is considered "de-salinated". I guess they're getting there, so by publishing this article, maybe they'll be able to snag some venture capital?
Re:Almost there! (Score:2)
Re:Almost there! (Score:1)
I think that they can start using it now. According to Wikipedia [wikipedia.org], we might be able to drink 2 cups of sea water per day, when mixed with a cup of fresh water. So, if we take 2 cups of the "almost there" water, and then add a cup of fresh water, we can get something fairly useable. No?
a total bust, not energy efficient at all (Score:3)
Re:a total bust, not energy efficient at all (Score:0)
Show me a thermal desalination plant that's either sized for a lifeboat or runs without electricity.
Re:a total bust, not energy efficient at all (Score:4)
Re:a total bust, not energy efficient at all (Score:2)
Re:a total bust, not energy efficient at all (Score:0)
The question is how much this technology can improve in the future. As of now, it's unusable but so was solar panels in it's early life. Hopefully it can improve enough to be useful and still being near it's theoretical better energy efficiency.
It's is news from a researcher, not like there are plans for it's commercialization yet. Research is a good thing as more research is needed to see if this will be beneficial to us in the future or simply something to note.
Re:a total bust, not energy efficient at all (Score:2)
I can show you a reverse osmosis rig with a solar-powered pump and a manually-operated backup mode....
Re:a total bust, not energy efficient at all (Score:5, Informative)
Re:a total bust, not energy efficient at all (Score:5, Informative)
Re:Almost there! (Score:2)
Couldn't they run it through a few times to get it desalinated further? Or is it like how some fish will always be small enough to slip through a net?
Re:Almost there! (Score:1)
The article states 25% desalination for the first pass, and the limit at 50%, so I assume they already ran it more than once.
Re:Almost there! (Score:4, Informative)
If they're really the first to implement a new chemical process here, then the GP implying this is not significant in itself and they just published it so they could get venture capital is pretty sad. There used to be this thing called "research." Most of it went nowhere, yet it created the world we live in.
Re:Almost there! (Score:0)
We need to leave that much salt to improve the taste of the industrial pollutants.
Hee'uk (Score:2)
Maganese oxide? I thought Maganese was used for Galvanizing metal. Doesn't that mean it doesn't "oxidate"? :P
Re:Hee'uk (Score:3)
Maganese oxide? I thought [Manganese] was used for Galvanizing metal.
Don't you mean zinc?
Re:Hee'uk (Score:2)
Yeah. One of Maganese's uses is to control rust in steel. I used Galvanizing as a generalized term. I should have know better on /.
Re:Hee'uk (Score:2)
Maganese oxide? I thought [Manganese] was used for Galvanizing metal.
Don't you mean zinc?
Yeah. One of [Manganese's] uses is to control rust in steel. I used Galvanizing as a generalized term. I should have [known] better on /.
It averages out. I didn't know that about manganese. Now we're both richer. :-)
Some of us (well, I am anyway) are a veritable bottomless pit full of useless information. Put me in a room with iron ore, coal, and zinc, and I doubt I'd be coming out with any galvanized steel any time soon.
Re:Hee'uk (Score:0)
That's magnesium you're thinking of, and no, that means it's more susceptible to oxidation than iron. See wikipedia. [wikipedia.org]
As it happens, manganese is also slightly more electronegative than iron, but not enough to make it useful as a galvanic electrode.
Re:Hee'uk (Score:2)
Manganese is a transition metal, and it certainly oxidises very readily - down to +7 in fact. I'm sure most people who have done high school chemistry remember the dark purple KMnO4 solution.
Zinc is also a transition metal, and is what is used in the galvanising process.
Battery? (Score:3)
Isn't this called electrolysis?
Re:Battery? (Score:1)
Isn't this called electrolysis?
Most electrolysis cells deposit the metal on the elctrode; you can't do that with sodium, because it reacts with the water. The trick here seems to be that the sodium gets absorbed into the electrode, and so is actually removed from the water. Neat, but no coconut - yet.
Hmm (Score:5, Informative)
Of course, (good) reverse osmosis cleans out a LOT more out of the water then just salt, e.g. bacteria, viruses.
Re:Hmm (Score:2)
Re:Hmm (Score:0)
For irrigation, less than perfect desalinization is catastrophic.
How did Rome destroy Carthage? By salting their fields.
What destroyed the Mesopotamian empire? Their gravity-irrigated fields became so loaded with salt that nothing would grow.
Re:Hmm (Score:2, Funny)
It's electrolytes!! That's what plants crave!
Re:Hmm (Score:1)
For things like those, it's easy to go through a filtration system. Salt on the other hand tends to clog up filters relatively fast making filtration on a mass scale difficult (as in costly which is why you don't see much desalination plants for water).
Re:Hmm (Score:5, Informative)
Of course, (good) reverse osmosis cleans out a LOT more out of the water then just salt, e.g. bacteria, viruses.
Do you have a sense of how dramatically expensive RO is and how much cheaper it would be if 50% of the salt in seawater could be removed in a relatively low cost preliminary separation? Somehow most of the comments on this story, both positive and negative, seem to assume its main use needs to be as a desalinization gadget where you put the saltwater in one side and delicious drinking water comes out the other. That would be amusing but not particularly useful or realistic. The value of a separation technique is going to come in the form of energy and labor savings. If I talked about this tech at work I'd hear comments like, "imagine the RO fouling reduction!"
Re:Hmm (Score:0)
Somehow most of the comments on this story, both positive and negative, seem to assume its main use needs to be as a desalinization gadget where you put the saltwater in one side and delicious drinking water comes out the other. That would be amusing but not particularly useful or realistic.
I agree that's not realistic, but it certainly sounds useful.
Re:Hmm (Score:4, Interesting)
You might be right that the place for this tech is a pre-treatment for an RO process, but it isn't mentioned in the article and the researchers appear to be looking for a gadget "where you put saltwater in one side and delicious drinking water comes out the other":
I'd be dubious about the efficiency of doing this electrochemical desalinization to remove so much of the salt, I would think that the resistance of the water is going to rise substantially as salt leaves so it seems like more and more electrical energy will be required per mole of salt ions as the concentration drops.
So by pre-treating water to remove much of the salt before sending it to RO the membranes will last longer before replacement? How much of the operating cost of an RO plant is determined by this? Would there be an impact on the RO process energy consumption?
Re:Hmm (Score:1)
http://www.membraneshop.com.au/products/BW30%252d2540-Filmtec-2.5%22-x-40%22-Brackish-Water-Membrane.html [membraneshop.com.au]
$289.00 15.5 bar GPD-850
http://www.membraneshop.com.au/products/SW30%252d2540-Filmtec-2.5%22-x-40%22-Sea-Water-Membrane.html [membraneshop.com.au]
$390.00 Bar-55 GPD-700
So about $100,40 bar,150GPD better for Brackish over salt.
Re:Hmm (Score:2)
Life Rafts (Score:0)
If this is small enough I see it very viable for life rafts. Add a solar panel to power it and you could drastically increase the time people can live at sea well waiting for a rescue ship to find them.
Re:Life Rafts (Score:2, Informative)
I think they already have RO filters with hand pumps that would fit that niche.
Re:Life Rafts (Score:2)
I think they already have RO filters with hand pumps that would fit that niche.
There are also inflatable solar stills. They generate a lot less water but they are passive and you can use a bunch of them at a time.
Greatest news ever. (Score:0)
We can now use ocean water for crops and to drink.
Good water to storage and waste salt to my table or back in the ocean.
Awesome We were about to see some nasty water wars.
Again.
Ah, I got it ... (Score:0)
We'll solve the problem of global warming/rising seas by mass desalination of the oceans and use the semi salinated water to irrigate more food crop, so we have have more population! We'll power it all with wind/solar. Then we can dump the excess salt in Utah or something. Or conversely, we can turn some other area into Utah. Great!
Re:Ah, I got it ... (Score:1)
actually we'd probably dump the salt back into the sea, since most of the water that is being added to the system has very low salinity. It would lower sea levels and bring the salinity to a more normal level.
Re:Ah, I got it ... (Score:0)
Actually, the Bonneville flats were mined for salt and were in danger of becoming dust flats. Google "save the salt". Utah would be happy to have massive loads of salt returned where they belong.
A long way from being useful (Score:3)
No, you don't put in salt water and get energy and fresh water out. You put in salt water and energy and get somewhat less salty water out.
As with most desalinization systems, getting rid of the salt and other crud is a big problem. They haven't solved that yet. "Researchers need to find ways to remove sulfates from seawater, lower the cost of the electrodes, and protect the system from deposits of biofilm and scale that could cripple the device." It took a long time (from 1748 to 1965) before reverse osmosis membranes were developed that could handle that problem. Reverse osmosis systems require an occasional freshwater flush, but this takes far less water than the system produces. It's not clear how the numbers work out on this new approach.
Soartowrks tech (Score:0)
Nothing new, it's just being suppressed. One can make solar desalination plants with cheap parts, check out www salt works tech com
So good, let those germans tell us how!
Now this is just a case of ... (Score:0)
wait for it ...
A "salt" and battery....
Late arrivals at the desalination party (Score:4, Informative)
Just the other day it was discovered water magically evaporates thru sheets of graphene about as fast as you can pour.
Kind of makes it difficult to see the point of experiments involving basic chemistry with lousy effeciency falling off a cliff as concentration of salt is reduced.
Why? (Score:2)
>When the current is reversed, they dump the sodium ions out into waste water.
Why not just keep the salt, and make it into a packaged sea salt so as to use all of the elements and save money by making even more money from the process.