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Electricity From Salty Water
BuzzSkyline writes "It's possible to produce energy by simply mixing fresh and salty water. Although chemists and physicists have long known about the untapped energy available where fresh water rivers pour into salty oceans — it's equivalent to 'each river in the world ending at its mouth in a waterfall 225 meters [739 feet] high' — the technology for exploiting the effect has been lacking. An Italian physicist seems to have solved the problem with the experimental demonstration of a 'salination cell' that creates power given nothing more than input sources of salty and fresh water. The researcher believes that this renewable, environmentally friendly energy source could be deployed in coastal areas and could provide another addition to the green-tech roster. A paper describing the technology is due to be published in an upcoming issue of the journal Physical Review Letters."
Quick! Grab all your salt shakers and run to the bathtub!
leather-dog muksihs
Blog: @muksihs
he key ingredient in a salt-water capacitor is "activated carbon," extremely porous carbon made from wood, coal, or coconut shells.
Gilligan could have lived well on that island.
...for pissing in a swimming pool?
So can we expect this to work in parallel with existing hydro power generation techniques?
I hope the Energizer Bunny owns water fins and a snorkel!
A device that gleans usable energy from the mixing of salty and fresh waters has been developed by University of Milan-Bicocca physicist Doriano Brogioli. If scaled up, the technology could potentially power coastal homes, though some scientists caution that such an idea might not be realistic.
Forget scaling it up. Put one such device in every fresh water toilet bowl.
Keep in mind desalination is
salt_water -> salt + water
whereas this reaction is
water + salt_water -> less_salty_water
You'll note that they're not exactly inverses of each other.
Don't bother. PETA and Greenpeace both called and said it'll kill too many endagered fish species.
While PETA and Greenpeace may have different definitions of "too many" than you do, balancing concern about impacts on fish stocks with concerns about energy is a perfectly reasonable thing to do, given that fish are part of our food supply (and food chain).
There's also issues like whether or not a given fresh water supply might have better uses.
Tweet, tweet.
It produces less (laws of thermodynamics are a bitch). But you point out an interesting way to describe it to people. i.e. It takes energy to desalinate sea water, this process is sort of like running desalination in reverse to generate energy.
The world is made by those who show up for the job.
Actually the technology was already available, and is to be used to power most the majority of homes in the Netherlands, including mine, if the proposal is approved:
http://ecoworldly.com/2009/03/08/saltwater-power-could-supply-energy-for-most-dutch-homes/
Or the original publication:
http://pubs.acs.org/doi/full/10.1021/es9004224?cookieSet=1
Too late, Exxon already bought the patent.
There are serious transportation issues with piping potable water from places where it is plentiful to places where it is needed. That's WHY we have a potable water crisis in some areas (especially the American Southwest) while we have no problem whatsoever in others (like the Northeast or the mouth of the Missisippi). In those places there's already huge amounts of water flowing into the ocean. This technology would allow that water that is already being mixed with ocean water to generate electricity in the process.
Also there are situations where water is not potable due to issues other than salinity, and for the purposes of this process might be considered "fresh" compared to saline water.
An interesting thing would be if this could be used to provide for cheap solar power - Some of the largest "solar power" we use today are salt concentration ponds - they don't provide electrical power BUT they do provide the function of separating salt from water in large solar ponds. It would be horrendously inefficient per unit of surface area, but the cost is so low that large surface areas could be achieved.
retrorocket.o not found, launch anyway?
PETA and Greenpeace both called and said it'll kill too many endagered fish species.
Dang it! I warned these people. Last month I sent them a letter:
Dear PETA,
While I love animals as much as the next guy, I'm sick and tired of your stupid press releases. You do more harm than good by making animal lovers seem rediculous to the general public.
Therefore, I have no choice but to make you reconsider your PR tactics. Starting next week, any time you issue a press release that does animals more harm than good, I'm going to the pet store, and buying a hampster. Then I'm going to take it out in the parking lot and hit it with a shovel.
Sincerely,
LocalMan57
I suspect this could have a profound effect on environments where salt and fresh water mix gradually and where the mix changes with tidal flow. I live in Virginia, and I can't imagine this would work without significant environmental challenges to the coastal waterways like those that flow into the Chesapeake Bay.
If you RTFA (pardon me, I forgot this is SlashDot) the same effect can be gotten by mixing salt water with more highly salinated water (made by evaporating sea water - say, using a solar evaporation pool) or lightly polluted water (non-potable).
I could also venture a guess, based on the fact this is a solution postulated for coastal locations, that the process could also be sited at or near the mouth of a river - say one the empties into the sea or ocean? In that case only fresh water that was destined to end up mixed into salt water would be used.
...carrier dead.....
This is actually really interesting! Think about it. We've been limited to solar cells for a long time for producing electricity, and those have limitations we are constantly struggling against. But... Now, you can make a simple isolated enviroment consisting of water and salt. Design it such that fresh water runs down from a resivoir into a lower resivoir with salt. Expose the lower resivoir to sunlight, and use the greenhouse effect to speed up the evaporation of the water. Direct the vapors up to the upper reservoir, where they precipitate out, and flow back down! Thus, we generate electricity and use the sun to separate the two components to repeat the cycle. (plus if you want, you can capture the heat from the condenser, for even more energy) Not something you could put in your car, but on a large scale I bet this could work. Similar to large steam powered plants.
"Brogioli maintains that his salinity cell could be ramped up faster than other salination approaches and could be made as affordable as solar power in a decade or so."
As affordable as Solar in a decade? Solar's main problem now is it's cost!
One of the best places (potentially) to grow algae for biofuels is in the desert. You could pump seawater inland, and circulate it in pools. If you covered those pools with greenhouses (which could just be big clear balloons... or not-so-big ones, if you use arrays of small pools) and collected water they'd make you some fresh water, which could then be combined with incoming salt water to produce energy to help run the system, whether that would be the pumps, mixing devices which keep the pools circulating, or what ever else have you.
Another idea for the waste water produced from this process is to pump it inland and use it in the algae pools... so you can have coastal plants whose effluent is used to grow algae for carbon-neutral biofuels, and [optionally] to raise the water table in the desert.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
This would be a great way to power all those desalinization plants on the coast!
æeee!
Windmills convert wind into electricity. The result...less wind on the far side. That changes climate I'm guessing. Not sure how wind affects things. Hotter animals because of less breeze? Smaller area of seed dispersal? Other things.
Solar panels take the heat energy out of the sunlight and convert it to electricity. I'd think that would cause the ground to heat up less, but that's probably insignificant compared to the direct change of 'being in the shade' for all the flora and fauna under the solar panels.
What do the hot/cold water exchange generators do? I would expect that pumping cold water from the ocean warms up the ocean...but that would be putting energy INTO the water instead of extracting it. So I'm a little confused. Lets just say it 'changes the ocean temperature'. That's enough to disrupt the ecosystem.
With this salty water thing. Whose energy are we stealing? If there's some sort of exothermic reaction going on in all river mouths, there's definitely something that's evolved to take advantage of that. Energy on the planet doesn't just SIT there doing nothing. (cept Oil...nobody uses Oil but us. :) ) What's the result of the environmental impact study? (I don't just mean habitat loss...I want to know who specifically was harvesting that energy.)
--Welcome to the Realm of the Hawke--
Keep in mind desalination is
salt_water -> salt + water
Show me a single commercial example where this is the case.
Desalination is:
lots of salt_water -> lots of slightly_saliter_water + a little fresh_water
High rejection ratios help reduce the energy requirements as greater temperatures or pressures (depending on the method) are required for greater salt concentrations.
need new "Missed Funny(+1) By *That* Much" moderation....
People in cars cause accidents....accidents in cars cause people
Nice to see somebody talking about energy from water salinization once in a while, but that is not the first experiment to gather a few microjoules at lab. Up to now, no aparatus could be scaled up, all of them hit that "we just need better materials" barrier. There is a reason for that, because of the way difusion works, each device can create at most 100mV, and that will fall almost exponentially down to near 10mV once one starts gathering more than 5% of the available energy.
Just put that on the right perspective, there are just a few specialized diodes that will dissipate less than 100mV on the charge going through it. A normal silicon diode will dissipate 700mV, and there is simply no diode that will dissipate less than 10mV. Also, to get some sane amount of power at 10mV one needs quite a big current, the charge is available to extract that current, but the resistence of your circuit (and the capacitor's dieletric is a piece of the circuit) is a huge barrier. To create 1kW, one'd need a total current of 10^5A (of ions flowing into and out of the coal, if not electrons flowiong throug the circuit), with a total resistence of 10^-7 ohms. To reach such small reistences it is normaly needed lots and lots of material, or "just" better material.
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There have been other ways to extract salinization energy: http://en.wikipedia.org/wiki/Reverse_electrodialysis
These methods are even being used in test sites to generate power. Main problems are that there's a lot of crap in rivers that you need to filter out to get high efficiencies.
- Give a man a fire and he's warm for a day, but set him on fire and he's warm for the rest of his life.
You start sentences "I clubbed that thing" often enough to "have a saying" for it? :)
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It isn't a water problem, it's a stupid people problem.
But people are mostly made of water, so now you have a stupid water problem...
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Don't bother. PETA and Greenpeace both called and said it'll kill too many endagered fish species.
Fish? Oh, you mean sea kittens.
As such, any time we find a new source of power, you can damn well bet nature has gotten there first, and that our exploitation of said power will have negative consequences for the species already using it.
This sentiment of yours is dangerous in the sense that it is wrong yet rational enough that too many people could believe it.
Nothing was using the energy stored in uranium or oil until we got around to using it. And neither us nor any other creature is harnessing e.g. the energy of deuterium and tritium contained in seawater. Nothing is even using the energy of the sun shining on the desert.
Another problem with your idea: energy cannot be really "used", it can only be directed elsewhere. Sooner or later every form of energy will change into heat. We cannot stop this, but before it takes place we can transform energy into other forms to do something useful. Example: when the sun shines on the desert, it is converted to heat straight away. But when we put solar panels there, we can redirect a part of the energy to our homes and use the energy from the sun there, where in the end it will also be turned into heat.
I could go on about how humans are not artificial, but part of nature, but the main premise of your post is already invalidated so I'll stop.
Those who would give up liberty to obtain working drivers, deserve neither liberty nor working drivers.
Here's the problem. Gravity is only interested in moving stuff in one direction, down. At some water will have to move against the gradient. Does the process produce enough energy to do that? If it does, how much water do you need in how much space, but just as importantly, what is the rate of production?
Oh, we'll put it on the coast, people say. Do the mixing reservoirs have access to the ocean? Good luck with the tides.
That wont bother PETA at all. They have nothing against killing animals senselessly. They only get angry if you try to justify the death of the animal by using its fur or meat for something useful, but if you just throw it all out it's all good with them. http://www.petakillsanimals.com/
I have mod points here, but I didn't see any other posts addressing this point, so I'll say it instead.
The big problem with all of these kinda wacky energy schemes (from the perspective of energy independence and global warming advocates who clamor for these things) is that none of them show any potential of producing enough energy to measurably offset the use of any of our major energy sources like oil, gas, coal, and nuclear. It may be cool and there may be a useful niche for it somewhere, but unless you can get at least gigawatts if not tens of gigawatts or more reliably, then it won't have any effect on our importation of fossil fuels or overall global carbon emissions. And there's also the question of how much other environmental damage and disruption would be caused by deploying something like this on a multi-gigawatt scale.
I don't reply to ACs
Dude, I am totally going to put one of these awesome banners on my site!
I think you need to consider this more deeply.
You need two water sources, fresh and salty. The chambers are flushed alternately from each source. The only way this happens naturally is if you use the tides. Which gives you a total of 1 cycle a day.
Nature is not going to do all of the work. At some point, water needs to be moved against a gradient.
He needs a pump in the lab. If you used a river delta, where there's a natural water flow, you only need a series of diversion gates; one to let fresh water in, one to let seawater in.
He states that in theory you could capture 1.6KJ/Litre of water. 1 Liter water =~ 1 kg. Assuming you want 1m of elevation difference (it simplifies the math and that much head is a pretty solid flush), that's 9.81 J/liter at 100% pump efficiency. Assuming ~30% total pump efficiency, you're at ~30 J/liter. Now say that he has to pump both fresh and salt water, so it takes a total of 60 J of pumping per liter of fresh water reaction. If his system can reach 50% theoretical efficiency (0.8 KJ/liter) then you'd generate ~0.74 KJ/L of fresh water.
Using my example above of diverting ~10% of the mississippi river, Mississippi = 572,000 ft^3/s * 28 L/ft^3 x 10% x 0.74 KJ =~ 1.2GJ/s =~ 1.2GW.
I'd say a 1.2GW power plant is a pretty nifty goal.
Of course at the moment he's generating 0.00005J/liter in his proof-of-concept unit, so that 50% theoretical may be lofty, but with ~60 J/L of overhead, he starts positive power production at 4% theoretical. Not sure what percentage he needs to produce more power than manufacturing the the carbon and other plant facilities requires.
I've been on slashdot so long I'm starting to get out of touch with the cool stuff if it ain't on slashdot.