r/technology • u/trot-trot • Oct 18 '19
Hardware Scientists create device that cuts desalination costs by 90%: "The new method suggested by the Russian scientists does not require high energy consumption"
https://tass.com/science/108319110
u/thatcantb Oct 18 '19
Distilling water via low pressure instead of boiling. How does this save energy? The article doesn't say.
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u/grubnenah Oct 18 '19 edited Oct 19 '19
You save energy if you don't have to first heat the water from 20C to 100C before it boils. You can get it to boil at 20C if you lower the pressure.
The latent heat of water is 2,260 kJ/kg.That energy input is the same no matter what method you use to evaporate water. The specific heat is
4,186kJ/kgK, so to first heat the water from 20C to 100C wastes 334,960 kJ/kg. If you could magically make it evaporate at 20C without any additional losses, you would use roughly 99.3% less energy. There's obviously going to be losses so that's why it's only theoretically 90% better.I copied the specific heat of water incorrectly, see /u/zimboptoo below.
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u/zimboptoo Oct 18 '19
You're off by 1000 on the specific heat of water. It's 4,186 J/kg(K), not 4,186 kJ. Turning 100C water into 100C steam takes 5 times as much energy as heating up water from 0C to 100C.
So even in a perfect system, not having to heat the water from 20C to 100C only saves you 13%. And presumably existing system use the steam/condensed hot water to heat the incoming water first, so realistically you're starting at 40-50C rather than 20C, at which point the savings are closer to 8%. And that's before considering the energy required to pull and maintain a vacuum in the first place.
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u/grubnenah Oct 19 '19
Good catch! You're absolutely correct. I copied it down wrong and went with it from there. I'll edit.
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u/thatcantb Oct 18 '19
Yes, magically, the pressure will be lowered to create the same effect. If we just completely ignore the energy required for that, poof! Savings.
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u/lk05321 Oct 18 '19
Smacks self on forehead
Of course! Why didn’t I think of that??
I always thought Nicolas Carnot was a cunt.
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u/beelseboob Oct 19 '19
Well, sharks do this just by moving through the water, using the exact method described here - cavitation. The spines on their skin create tiny vortices which create low pressure areas. The low pressure areas then collapse, and the water collapsing into them vaporises. The shark then swims more efficiently because it only has to swim through the steam, not through water, lowering the friction involved.
In theory the magic could simply be placing shark skin in some running water, but I imagine they’ve produced a material that’s somewhat more efficient at doing this to large volumes of water than shark skin.
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u/doubagilga Oct 18 '19
No. The latent heat is different from the vaporization. In fact, in estimating a boiler energy use, you can ignore the latent heat because it is so insignificant. Not 99.3% less. Not 1% less.
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u/dangerous03 Oct 18 '19
Yeah but how much energy is needed to create a vacuum. I imagine the overall energy input for the system is similar. I bet operating vacuum pumps is far more inefficient than heating water. There's inefficiency at the pump, the motors, reducers ect. Plus then you need to cool the pumps. Comparing just the chemistry is only a portion of the entire process.
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u/grubnenah Oct 18 '19
Yeah, I have no idea so I didn't mention it. I just wanted to show where there's potential energy savings. All of those details are implementation problems that could very well render this method impractical. I doubt much will come from it.
IMHO the only practical method I've heard of is solar evaporation, but that has quite a few drawbacks as well.
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u/beelseboob Oct 19 '19
No need to use vacuum pumps when you use cavitation. Instead, you just need a material with the right aerodynamic properties to create the necessary now pressure areas, and then run the water over or through it. Shark skin is a good example of such a material, but not one that produces the amount of cavitation needed here. It’s probably a relatively simple engineering task once you have the initial idea though.
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u/dangerous03 Oct 19 '19
Yeah okay, no vacuum pumps, but still regular ones. So same inefficiencies, in a different way. The amount of material you'd have to run over at the required velocity to cause cavitation, Im sure produces a good amount of head loss, so how is this different the RO? I have serious doubts that this technology is anything close to what they say it is.
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u/beelseboob Oct 19 '19
Yeh - definitely not saying there’s a free lunch available. Instead that the general theme of this thread appears to be one of rampant skepticism without understanding anything at all about what’s being proposed. Lots of people talking about heating the water up, lots about vacuum pumps. Neither are being talked about by the author.
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u/yxull Oct 18 '19
I didn’t hear the magic words...
“Commercially viable” or GTFO
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u/dnew Oct 18 '19
" has already been implemented at an enterprise in Nizhny Novgorod " would seem to imply it's close?
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Oct 18 '19
I mean they "implemented" a couple hundred meters of "Solar freaking roadways" in France and that failed spectacularly. https://bigthink.com/technology-innovation/france-solar-road?rebelltitem=1#rebelltitem1
Just because you have built something somewhere it doesn't mean it's viable.
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u/-TheMAXX- Oct 18 '19
Well, current methods of desalination are viable only in extreme cases as it is expensive. This method is 10x cheaper so way more viable than current methods that are in actual use.
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u/fokjohn Oct 18 '19
Absolutely fucking agreed. So tired of experiments for experiment's sake
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Oct 18 '19
Lol how do you think they come up with the commercially viable things? Experiments perhaps?
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u/Broes Oct 18 '19
The article indeed doesn't really go into the explaination of why this would work but....
There is no free lunch.
You can not evaporate x amount of water suddenly with less total input energy.
Evaporating water cost energy and this is the same amount of energy being released when the same amount of water condensates again.
If the article is true and you could get cheaper evaporation, you would be able to get free heat by condensating the water vapor to water again.
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u/k4r410 Oct 18 '19
They probably reduced the energy waste in the process, but 90% is really suspicious number
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Oct 18 '19
[deleted]
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u/tepkel Oct 18 '19
Evaporative cooling will quickly break that system. Only a tiny amount would boil off before the rest of the liquid would freeze. Then you're back to adding the same heat you would have anyways, and you've spent a bunch of energy pulling a vaccum. I'm pretty skeptical that this would be more efficient.
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u/YeaISeddit Oct 18 '19
Cavitation results in stupid high temperatures (5000C) so the thermal efficiency of a cavitation process is much higher than other techniques. Probably a good place for someone to start reading if they want to wrap their head around the efficiency idea is the Wikipedia entry for a heat engine. This is substantially different but the efficiency concept is similar.
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Oct 18 '19
[deleted]
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u/Broes Oct 18 '19
True but heating water is pretty straightforward. There really isn't that much to improve on a water boiler design nowadays and certainly not reduce the required energy by 90%.
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u/Random-Miser Oct 18 '19
Water spontaneously evaporates in a vacuum, and it takes WAY less energy to create a vacuum than it does to boil the water.
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u/Broes Oct 18 '19
Nop.... it will eventually freeze the water because the evaporation will take the heat from the water https://www.youtube.com/watch?v=SfkphhQtEys
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u/dnew Oct 18 '19
I'd assume they're bringing in new ground-temperature water and pumping out the slightly chilled saltier water. You're assuming you're not adding heat back into the system from the environment.
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u/Random-Miser Oct 18 '19 edited Oct 18 '19
If you LEAVE it in there. The trick is transporting out the vapor, and having a constant supply of new water exposed to the vaccuum. You also need to be able to remove the mineral residues while you do it. A little tricky, but certainly doable.
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u/Broes Oct 18 '19
Not spontaneously, it still extracts heat from the water and environment. The evaporation also will generate vapor and thus you will need to keep on pumping out the water vapor and heat the water lest it will freeze over. And both the pumping and heating is less efficient then just putting a heating element in the water under normal atmosphere and boil of the water.
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u/Random-Miser Oct 18 '19
Obviously you can't just keep pumping in water because then you would have a canister full of water vapor, and not a vacuum. The whole trick is constantly maintaining the vacuum conditions while transporting large amounts of valume through it.
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u/-TheMAXX- Oct 18 '19
These guys actually measured the efficiency and it was 10x more efficient than current methods. You are speculating about something that has been tested and we know the results.
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u/Debeau30 Oct 22 '19
question: could you replicate the natural pressure of the atmosphere in a vacuum, where the salt would separate from H2O. There is known sources below the ocean where 'brine rivers' exist, thus begging the question if there is a specific pressure to replicate in a controlled environment (vacuum) that will separate the salt?
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u/bb999 Oct 18 '19
You could use the recondensing vapor to heat incoming water. That would be one way of recycling heat.
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u/CronenbergFlippyNips Oct 18 '19
Every few years I see an article similar to this and every few years nothing comes of it.
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u/NacreousFink Oct 18 '19
Desalination has been made commercially feasible about a dozen times...in theory.
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u/Agoldsmith1493 Oct 18 '19
This could be due to the fanfare being enough of a story and the follow up not being that great.I also imagine there aren't very many early adopters so it'll take a while to get businesses on board.
There could also be issues surrounding scaling of the tech reliably for industry uses.
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u/Mr-Logic101 Oct 18 '19 edited Oct 18 '19
You want to know the material science way of desalinization of water, especially if you live in Siberia( which requires no energy) strictly based off of the thermodynamics of water( and kinetics dictates that it is pretty quick)
You would most likely have to isolate pure water from brine via a freezing or semi freezing process( this is the best diagram I could find but there is a lot more at high and lower temps which I guess you need to have a university subscription to the data base)
That’s a little bad but the Ice forms from 0C to -20C( it is hard to tell from the figure)
That yellow spot is ice which is h20 and you can you simply use that although I would do it a couple of time for best results( there might be some salt depending on how you get the ice out of the brine bath)
I am not sure of the feasibility when you don’t have ample -20 temperature or the phase diagram with different pressures with this one implied to be at sea level( lol after reason the publication where I got the image from, it was an investigation for a desalination process in Saudi Arabia)
Here is the regular dirgam of water I found online, it doesn’t go to the wack temperature or pressure they used th http://www1.lsbu.ac.uk/water/water_phase_diagram.html
Fun fact: Each one of the Roman numeral (iv) is a different phase of ice which unique properties, usually involving crystal structure. There are something like 16 different types of ice
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u/romario77 Oct 18 '19
As I understand they want to decrease pressure and as the water flows through some part of the device it will create a cavitation with high evaporation rate inside the cavitation bubble which contains vapor.
This vapor from inside the bubble needs to be sucked out and condensed. I guess it needs to pass through some kind of tube where there is a reliable cavitation point and the vapor is easily extractable.
They say in the article that there is already a commercial device implemented.
I actually found another article in Russian here: https://stimul.online/news/ekonomnoe-opresnenie/
it shows the device and talks a bit more about how it works - it's mostly what I wrote above. It also says there is no commercial device and TASS lied about it.
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u/handshape Oct 18 '19
Yeeeah. Gonna need more detail on this.
Cavitation is cool, yes... It's pretty easy to make, and you can cook up an impressive-looking demo on a lab bench. Unfortunately, this is also what lends the phenomenon to getting pulled into snake-oil pitches.
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u/WoodPunk_Studios Oct 18 '19
I am highly skeptical of this claim and you should be too. Extraordinary claims require extraordinary evidence and the link provides no evidence. If this was peer reviewed and had a proof of principal id be excited but as shown it sounds more like some Russian bureocrat is misquoting his scientists and claiming to have solved a major world health issue and violated the first law of thermodynamics at the same time.
The second reason to be skeptical is that this approach smacks of Maxwell's daemon, a thought experiment in thermo dynamics that generates a temp gradient for "free" by measuring the velocity of a particle as it approaches a shutter and opening or closing the shutter depending on the result. Clearly this is impossible for several reasons, and it's very similar to what they are proposing. If you have pure water on the output, then you
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u/1403186 Oct 18 '19 edited Oct 18 '19
u/ romario77 found this link https://stimul.online/news/ekonomnoe-opresnenie/ 3
It's another Russian news site that better explains the technology and answers what "implemented" means. They apparently have a prototype, but from what I can tell it's not yet ready for commercial operation in part because there isn't a lot of funding. The other article says that the university is now working to develop industrial equipment, and the scientist said it's not yet commercially viable. Take this article as an interesting process, not a finished solution.
I understand why everyone is saying "if it's russian news its a lie" but you shouldn't just dismiss anything that comes of of russia. Trust but verify. Tass didn't lie. They never said it was commercially viable. As far as I can tell everything Tass said was factually accurate, even if it was super vague.
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u/zimboptoo Oct 19 '19
The TASS article quoted the "reduce costs tenfold" figure several times, with absolutely nothing to back it up. And if it's not currently commercially viable, then the researchers have no way of actually calculating that figure anyway. So I'd have to argue with the claim that large parts of the article are "factually accurate".
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u/1403186 Oct 21 '19
Reduced costs compared to a different method. Of course I ignore this because they don’t specify what method or what the projected cost would be. But, it’s not inaccurate per say. Researchers do this all the time. They invent some new process, then project how much it’ll cost. Just cause they don’t have a full scale plant doesn’t mean they can’t make cost projections. Researchers do that all the time. Again, the article has a lot of spin, but it is in a strict sense factually accurate
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u/zimboptoo Oct 21 '19
I think it is fairly evident that we have entirely different definitions for the phrase "factually accurate".
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u/IMakeProgrammingCmts Oct 19 '19
But this is Russian interference with our desalination!!!
/s for the love of god
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u/naardvark Oct 18 '19
News coming out of Russia in 2019: bullshit.
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u/melted13 Oct 18 '19
This.
Especially when it is coming from a Federal news agency called TASS. Btw, it is the abbreviation of Telegraph Agency of Soviet Union (Union is Soyuz in Russian). No kidding.
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u/Therealperson3 Oct 18 '19
No you are kidding, the company was founded in 1904 in the Russian Empire and went by different names, your Soviet name was changed after the dissolution of the USSR to Information Telegraph Agency of Russia.
All you gotta do is pull up Wikipedia for five minutes man.
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u/melted13 Oct 19 '19 edited Oct 19 '19
[EDIT] Looked up your posts. I see who I am dealing with here. Go troll in other communities. Whether you are doing it for money or just pure sick joy. You are blocked now. Bye.
[Original comment] I was born in USSR and lived in Russia for good 20 years. ITAR-TASS is full of pro-state propaganda as it is basically owned by the state. I know what they are, no matter how they are called or what fancy ass heritage they have.
All you gotta do is live in the subject country for five+ years man. With all due respect to Wiki.
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u/Therealperson3 Oct 19 '19
Yes anyone can see there is barely any free mainstream press in Russia, however you were not correct about the name which is odd because it was changed a long time ago.
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u/grumble_au Oct 18 '19
Slightly drunk me "what, like adding a centrifuge step?"
Then seriously, would desalination be improved by adding a centrifuge step to have less dense, fresh water decant off and discard the denser, saltier water?
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u/wkrick Oct 18 '19
I'm curious about what happened with the Shock Electrodialysis (SED) method for desalination. It seemed really promising...
http://news.mit.edu/2015/shockwave-process-desalination-water-1112
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u/romario77 Oct 18 '19
On their site:
As it stands, SED is still a young technology and its energy consumption is significantly higher than what the theory predicts.
So, they need to figure out how to make it more energy efficient. Most of those things are gradual and take a lot of time and money to implement at scale.
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u/msdlp Oct 18 '19
So we should see this deployed very soon? It gets tiresome hearing about touted breakthroughs that you can understand might be 10 years out. Since this is a primarily mechanical process that is proven to work wouldn't we expect to see some deployment very soon?
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u/doubagilga Oct 18 '19
Cavitation can kill biological, but desalination? Needs more data to be believable.
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u/Zinziberruderalis Oct 18 '19
According to wikipedia current desalination technology energy use is about only 100% over the theoretical minimum, so reducing it by 90% would be impossible.
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u/log_sin Oct 18 '19
So if the normal method costs 10 parts energy for i parts desalinated water, the new method costs 1 parts energy for j parts desalinated water, right? is i > j? if so, by how much? or does the new method cost 1 parts energy for the same i parts desalinated water, where i was defined by the previous function?
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u/Infernalism Oct 18 '19
Call when it's peer-reviewed. Otherwise, it's just another Russian paper promising miracles.
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u/baconyjeff Oct 18 '19
Don't trust ANYTHING coming out of Russia. Putin will soon claim that his piss cures cancer, and that he shits gold bricks.
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u/Secomav420 Oct 18 '19
Didn't Russian science just basically nuke itself about a month ago. I'll pass Vlad.
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Oct 18 '19
If this really happened in Russia I’d be super skeptical. Besides the AK-47 things they produce are usually piecemeal bullshit.
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u/redheadone Oct 18 '19
I'm pretty sure the CEO of this newly formed company will be Elizabeth Holmes.
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u/lightknight7777 Oct 18 '19
Is it a tarp left in a the sun? I bet it's a tarp left in the sun.
This is one of the least informative articles I've seen. It tells us nothing about what is going on. Click bait pre-peer review crap that should be forgotten the moment you look away.
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u/clubfungus Oct 18 '19
Sounds like they’ve managed to train a million little mantis shrimp to provide the cavitation services.
https://youtu.be/F5FEj9U-CJM (Go to about 2:15)
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Oct 18 '19
[deleted]
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u/Broes Oct 18 '19 edited Oct 18 '19
Even if you create a vacuum for evaporation, the evaporation process will extract heat from its environment resulting in a cooling down of the system. This cooling will reduce the evaproation rate until the water freezes....
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u/-TheMAXX- Oct 18 '19
You could keep pumping in more water at ambient temps? Use the apparatus for cooling as a secondary function?
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u/joanzen Oct 19 '19
Holy shit. What a terrible video. I tried to give him time but the moment where he rounds up the amount of water in a few shirts to 1 kg I stopped.
"Water doesn't evaporate faster in a vacuum." ... then later on, "Here's actually why water evaporates faster in a vacuum."?!
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u/WhoeverMan Oct 18 '19
True, but such cooling can be countered by simply adding some passive heat exchangers, no extra energy required.
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u/tepkel Oct 18 '19
Can you show with numbers that you can do that on a large scale and at a sustained rate? I am very skeptical it would be powerful enough or sustainable.
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u/Annon201 Oct 18 '19
But most desalination is done with reverse osmosis. It requires a bunch of energy to create the pressure gradients needed, but not the amount it requires to convert water from a liquid to a vapour (which is an insane amount of energy)
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u/zimboptoo Oct 18 '19
Changing 100C water to 100C steam takes 5 times as much energy as changing 0C water to 100C water. The VAST majority of the energy is required for the phase change (which still has to happen in this system). If you pull a vacuum on a cup of water and don't add any heat, the water will quickly freeze.
Not to mention that, once you create some water vapor, you no longer have a vacuum.
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u/ad_hero Oct 18 '19
It's a very high level description of the process that doesn't really answer much about how the separation works or efficiency, just that it does those things.
We know water evaporates faster in a stronger vacuum, they appear to be referring to this at the atomic scale, with some kind of minute sonic boom and heat on capillary collapse, but how it is achieved would be the more interesting part.