This paper is interesting, however, in directly producing crystalline salt, which is lower volume than brine and easier to dispose of, maybe even valuable.
ps. I have no clue what I'm talking about
Animals in the ocean of course do live without fresh water. Some of them just live off of water extracted directly from their food or from metabolizing that food, which produces water. Some animals have specialized cells that excrete salt so that can take in salt water and separate out the salt.
> Testing their solar-thermal desalination technique using samples of water from the Pacific, Atlantic, and Indian Oceans, Guo and his team were able to make the surface self-cleaning. In other words, it extracted freshwater and directed the remaining salts to the passive region where they could be later collected without reducing the panel’s efficiency.
This is not "large" this is a moderate improvement. Albedo is likely only marginally affected, and the solar power input over area is the same.
Depending on this cost of this process it could very likely be a wash in terms of NPV
An RO desalination plant needs electric energy to drive the pumps, which might be generated by panels which are 15-20% efficient. So, if you can have cheap thermal desalination panels, they come out ahead even if 6x less energy eficient, you avoid the whole expensive and fragile desalination plant and you gain a low skill, distributed setup.
"Desalination system could produce freshwater that is cheaper than tap water" (2023) https://www.eurekalert.org/news-releases/1002811
ScholarlyArticle: "Highly efficient and salt rejecting solar evaporation via a wick-free confined water layer" (2022) https://www.nature.com/articles/s41467-022-28457-8
"Solar-powered system offers a route to inexpensive desalination" (2022) https://news.mit.edu/2022/solar-desalination-system-inexpens...
Easy, but not necessarily good for the spot you're pumping concentrated salt back into.
IMO this is an issue where NIMBYs are using environmental concerns as a smokescreen to block new desal plants from ruining the vibe at their beachfront property. Rhymes with the opposition against offshore wind farms.
I think that problem was known (and discarded as not important) when the first serious water desalination plants were built.
Most of the carbon we spew into the atmosphere came from the air. Ancient plants took it in via respiration.
Sure, and enriched uranium comes from the ground, but that doesn't mean it's safe to dump it back in after the enrichment process!
> So just dilute it back to close to ambient salinity using municipal waste water…
Wouldn't it generally be easier to process that municipal waste water, as is already fairly common?
Uranium can also come from the ocean water (there is, apparently, quite a lot of it in there, relatively speaking). Japan experimented with the technology in the nineties, but it really was much cheaper to just mine it from the ground, so they abandoned it.
If you think otherwise and you're not wrong, and I think you ARE not mistaken since this isn't the first time someone other than myself mentioned it here, that means they're making bombs because we in Japanese public aren't told about it. There has only been just some routine commentaries from local mayors at most.
It's a bit weird though that they have a graph of tons of uranium hexafluoride shipped that shows the last shipment in 2018 and nothing since then.
But you're doing that with the same water you're trying to make in the first place!
A phase diagram tells you exactly how far you need to go.
You know this makes more thermodynamic sense than carbon capture, right?
Just wait for the saltwater to come back around in the sewer.
But, so what? 30% sewage is still a strong dilluant... especially when mixed with more seawater
Im shocked how many people cannot grasp that you can dilute brine's salinity arbitrarily close to seawater's with energetically cheap pumps.
The advanced treatment stages take care of it. Between UV, ozone, and nanofiltration, etc. we can remove the pharmaceuticals.
Actually the problem is the water comes out too pure out of a well designed water reuse system, to the point where the mineral content can be too low and you need to add some back in.
But wait! There's water mass loss due to leaky pipes and outdoor pools!
Mixing salt water and brine is perfectly ok. Just use a phase diagram.
It's not every day that industrial waste happens to be not only edible but also tasty. Too tasty, in fact. Salt is addictive.
Ohio DOT's use of road salt would allow for fresh water to be provided for somewhere in the neighborhood of 160,000 people.
On one hand, that's nowhere near enough people; it's a small drop in a giant thirsty bucket of water consumption. So we'll still need salt mountains, salt re-distribution vessels, and/or other ways to deal with excess salt.
On the other hand, 160k is a lot of humans. So perhaps we should look into doing things like this anyway.
(But we probably won't. Ohio gets road salt primarily from a mine under Lake Erie that has a very conveniently-located terminus near downtown Cleveland. The mine directly loads trucks, freight trains, and ships...and it's near the point of use already. It's pretty efficient.)
Come on guys please at least attempt to think what you’re about to type, please, I beg you.
Just put it on your fries.
Just make prettier-than-Himalayan salt lamps out of it and sell it to hippies. Easy solution.
this is delusional ecological
Overall though, it’s just such a tiny concern. Ocean is huge. If we kill everything in a 100 foot radius, that’s 0.0000000008% of the ocean being destroyed. Less than a drop in a bucket.
RO is about 2-4x the theoretical minimum, depending on how much water you're willing to reject.
They're still at lab scale in glass. They haven't built a usable system, even a small one. The big claim here is that it doesn't clog; capillary action moves the salt out of the active area to another area, where some yet to be developed mechanism removes it. That needs to be demonstrated. If they can come up with something that runs for years without clogging or replacing the active material, that's a real advance.
Laser surface preparation is known.[2] It's useful for roughening smooth surfaces in a very structured way, in preparation for painting. The result is a smooth paint surface. If you sandblast to roughen, the first paint layer is somewhat irregular. Then you need to sand and paint again to get a smooth surface. Laser roughening has been tried for auto painting, but didn't go mainstream. A good question here is whether commercial laser surface prep systems can make the material this new process uses.
Great book on this BTW: Path Between the Seas. I couldn't put it down.
Another example is ultra black coatings. Those are a forest of tiny black objects arranged so that light gets reflected multiple times and is absorbed. The commercial version is called "Vantablack". It doesn't wear well, but for optical applications such as the insides of camera lenses and telescopes, that's fine.
Another MIT paper on desalination from 2024 has a more conventional electrically powered system that can adjust its operating speed depending on how much power is coming in. So it can run off intermittent power sources such as its own solar panels.[3] Rather than buffering the energy with batteries, just buffer the water in a tank. This made it to field test and has some efficiency numbers.
It's annoying to see these one-off announcements with no followup. A short note a year later reporting why there's no further work would be useful to later workers.
[1] https://news.mit.edu/2023/desalination-system-could-produce-...
[2] https://drl.mit.edu/publications/journal/
[3] https://www.greenmemag.com/science-technology/breakthrough-m...
Obviously it needs to be cleaned regularly otherwise the salt encroaches into the sensitive bits. However the cleaning method doesn't require dissolving, just scraping.
The new system replaces the earlier version that used specially engineered death metal.
Totally underrated area for academic pursuits.
At least in the sciences you have access to lots of opportunities you don’t have at bigger name schools.
They set me up in life in a way that I don’t think would have happened elsewhere.
Slow it down from trickling down a slope and you have two things: more vegetation (which also retains water) and more time for that water to penetrate the ground for local wells.
You can completely "terraform" a desertic region https://youtube.com/shorts/cfhbtgon4Nk?is=oAExB5UeMAsShBux
Israel desalinates 75-85% of its drinking water. The problem is political and economic dysfunction.
California for example could be doing widespread desalination with nuclear power and technology from the 1970s. They could also greatly expand reservoirs and waterways, but don’t do it. Very similar to Rome in the 400s, when people were using aqueducts built by a past civilization but lost the ability to construct them.
Solar on the other hand is very cheap, and you don't need to desalinate 24/7 -- just do it when power is cheapest (which is during the sunny times if you have large amounts of solar, during windy if you have large amounts of wind, etc)
The good news in a desert: plenty of sunshine. So you can generate a lot of electricity with some cheap solar panels, there is plenty of space to put some down, and there aren't a lot of NIMBYs around to complicate the permitting process for that.
Some desert ecosystems actually depend on condensation with specialized plants and animals harvesting humidity from ocean breeze. Large parts of e.g. the Sahara border on the Atlantic ocean. Lots of water in the air but not a lot of rain. And even if humidity is low, there still is some water in the air usually.
But the simple fact of course is that there is a lot more water in water than there is in air. If you want to extract meaningful amounts of water from air, you need to process a lot of it.
And who's going to know if you are drinking it or watering your garden?
My well is 100' and 13 years old.
It also requires more infrastructure to get yield. In theory all you'd need to have is these etched metal plates, a transparent dome and a source of briny water. (and a cleaning mechanism)
The etched plates creates 100% humidity (probably more as it'll condense out)
The reason it doesn't actually work is that it is extremely inefficient. Getting water to condense requires you to somehow reject massive quantities of heat. That's fundamental to physics.
Also, literally anywhere a dehumidifier is reasonably effective, is humid and usually doesn't have such dire water problems. Deserts have extremely low humidity and dehumidifiers working in a desert will produce very little water.
Even a good humidifier in a humid environment is burning KW to generate on the order of ten liters of water a day.
There are a couple places on earth that are essentially deserts but have an early morning humid fog roll through regularly, and those places figured out capturing that water in the air long long before we invented the refrigeration cycle.
It is literally cheaper to desalinate.
Maybe you could build giant greenhouses to fill with sea water and let the sun evaporate the water and collect that with a dehumidifier? Still absurdly inefficient. Water has such an obscene specific capacity for heat that any thermal avenue of separating it from something else will use immense energy.
Sand -> Glass -> heated saltwater -> freshwater + minerals -> ??? -> profit?
Combined with some mangrove farms, surely desert coasts are able to support more life.
Wonder if this is scalable tech, and how quickly it can 'process' water. I guess if they're combined with transparent solar panels, it could be quite an epic tech.
https://en.wikipedia.org/wiki/Red_Sea%E2%80%93Dead_Sea_Water...
Some over stuff whhich are cool to read about:
Redirecting Siberian rivers into Central Asia https://en.wikipedia.org/wiki/Northern_river_reversal
Redirecting Congo basin rivers to replenish Lake Chad https://en.wikipedia.org/wiki/Lake_Chad_replenishment_projec...
Filling in a depression in Egyptian Sahara desert and fllooding it with Mediterrraanean water to generate huuuuuuuuuuuuge hydro https://en.wikipedia.org/wiki/Qattara_Depression_Project
(Similar ideas proposed for Lake Eyre, the lakes in Tunisia, and the Afar Depression in Djibouti, too).
It's all gonna get on the glass (from above and below), and eventually the salt left behind is going to build up. The salt left behind is very hard on any structure or machinery used to move it which makes repairing the large glass enclosure a pain. All this for a slow trickle of water is generally not worth it.
https://www.solarwaterplc.com/featured-news/whats-inside-thi...
[1] https://news.mit.edu/2024/how-light-can-vaporize-water-witho...
Now you ask: why don't we just recover magnesium from brines if it's so great? Magnesium recovery from seawater isn't that easy: typically you have to treat it with some kind of alkali (often Ca(OH)2), so the cost is dominated by the extraction process (your alkali is consumed!), and you're competing with a pretty cheap ore. But if you have a solid byproduct, instead of a liquid, the options for magnesium recovery might be a lot more efficient, potentially offsetting the cost.
The fourth-most-prevalent ion, sulfate, might also be interesting, at least in a hypothetical post-petroleum future where sulfur as a byproduct of fossil fuel extraction is no longer "free". Sulfate is also annoying to extract from seawater, but again if we have a solid, the rules change.
As for the "table" salt itself, I think we'd quickly saturate (!) the market.
At least read what you're pasting
I'm not sure what to say, because it looks like you are copy-pasting from Wikipedia or something like that. Anyway, Mg(OH)2 is not found in seawater. Mg2+ is found as a dissociated ion. When you dry it, it mostly becomes MgCl2 with a little MgSO4. Mg(OH)2 is produced from seawater by the alkaline extraction process I mentioned before, and the process in TFA is interesting because it might be better.
Also, nobody would ever make magnesite ore. I referenced magnesium ore prices to estimate the value of the magnesium-as-ore in sea salt, because using finished magnesium prices would be misleading. Magnesium is mostly consumed either as the metal or as the oxide in cements and ceramics.
“We collected a total of 9.3 g freshwater along with 0.343 g of sea salt from the ABF-STIC with a 9 cm2 surface area over the course of 9 hours. This is equivalent to generating 10.33 liters m−2 of freshwater and 0.38 kg m−2 of sea salt per day. The salinity of the desalinated water is found well below the WHO and EPA standards for safe drinking water.”
However the enclosure system required looks rather complicated and might be sensitive to external temperature (maybe a solar PV-powered cooling loop would help) and I imagine the cost-per-square-meter of the material is rather high, so this looks more like something for emergency response situations or maybe a desal system for a mega-yacht. If it could be scaled the idea is interesting, maybe as lithium separation from concentrated geological brines?
Brutal. 𖤐 \m/ 𖤐
Who all has access to a femto laser? As far as I know these are all patented, and most of those patents (or at the least companies with rights to production) are in the USA, according to a professor who told us so some years ago in university (in central Europe, but he is quite old already, so I am not sure if his information was 100% up to date; but otherwise I do not doubt the validity of his claim made). So someone is going to milk rather than help. Will be interesting to see what happens to that in some years. My current guesstimate is that nothing will really happen or change.
I suppose you could water down the ocean water it’ll was drinkable, or like just add half a teaspoon of sea water to a cup or drinking water.
Buy all work done eventually decades in to waste heat.
...except for the huge piles of salt.
If the salt was not waste, surely people would already be extracting it from the brine and the existing methods would also be "without waste".
I would like to read more about this from an authoritative source.
https://www.frontiersin.org/journals/marine-science/articles...
https://www.sciencedirect.com/science/article/abs/pii/S14635...
@GP: Instead of a plain complain, it's better to get an interesting discussion to write an explanation of why the post makes no sense, or instead find the good debunking comments and upvote them (there are two or three good comments near the top now).
I try to be that guy (personal hall of shame https://hn.algolia.com/?dateRange=all&page=0&prefix=false&qu... ) but life is too short and I have other things to do IRL.
Also, it's not my area. It's close enough to have a good guess, but in this case for me it's better to let someone else give an accurate reply.
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Back to this post:
It obviously makes no sense. You have salt water, you extract the water, you have to get rid of the salt. Why waste time reading the details? [There are some interesting technical ideas about new surfaces, more on this later.] Reading the details their brilliant idea is to make salt cubes and sell them. So there is no waste!
When you get rid of the salt using brine, it's easier to transport and dilute the liquid. With solid salt you must scrape it form your high tech surface (without scratching it?!) and now the solid salt is difficult to transport. Also, to sell it you must purify it because it will include nasty things like crabs legs and sea smell.
Once you extracted the 99% of the water, it's difficult to extract the other 1% of the water because it's saturated solution with a low osmotic pressure, vapor pressure and a high boiling temperature. Also, water inside the block of salt is difficult to extract, and you must crush the small blocks.
Salt production is done in big salt lakes areas, where energy is "free". I like to consider it like a huge natural solar panel. You get heat for "free" and dry wind for "free". You must pay for them in an industrial facility. Also, the normal process still requires a lot of manual labor of guys/gals with [mechanical] shovels to makes piles of salt, wait, turn it a few times, wait, turn it a few times, wait, ... and you now have a nasty salt that you still have to purify to be able to sell it.
So they will get salt that is too expensive to sell, and too much of it to flood the market, and if you put it in the garbage can it will be classified as [industrial] waste.
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The technical part looks interesting, but it's on the bottom of an unrealistic title and first paragraph. The interesting part is about the new surface with nano details and titanium oxide that absorbs Lithium. It sound interesting and they published it so there is some validation of the claim, but after the nonsensical first claims I'd want to take a look at the feasibility details.
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>> Can we please ban university press releases
> Why?
I work in an university and I expect technical accuracy from the press department of an university. We want people to give us money in exchange of doing real and interesting things. We want people to trust the medical doctors when they give health advice, or a lot of other specialist about other public policies.
A lot of press release of the universities have a lot of exaggerations, burning the trust of the people. Before opening one here, I like to guess what is the real result and what is the bullshit part. I think that a complete ban of university press release here is too much, but I understand why the GP is annoyed.
i'm hoping it doesn't scale, honestly.
You're not worried? If it's for batteries? For sure they'll extract whatever they can.
(I checked, some deposits are old lakebeds like https://en.wikipedia.org/wiki/Salar_de_Uyuni and others are igneous.)
It's also possible - true, I bet - that all the car batteries and storage batteries 8 billion people could possibly use are equivalent to only a tiny fraction of all the lithium in the ocean, but it would be harder arithmetic to confirm that, as well as being irrelevant on account of land-based mines existing.
That still means there's billions of tons of lithium in the seas, though.
> The brine byproduct wreaks havoc on sea life when it’s deposited back into the ocean by raising the salt level and lowering oxygen in the water.
Managing return of concentrated brine should be entirely tractable in the literal ocean.
Ships (with long submerged pipes) would be prone to weather events and generally less reliable than an installed pipe. Perforation would be prone to clogging from build up so a nonstarter I would expect. Adding flex tubing and a relocation robot would be a maintenance headache as well. Not sure there is an easy optimization.
As for surface life, I'm no oceanographer, but is that really the most vulnerable place? The surface is where fresh water rain meets the ocean, so that would dilute the salinity during storms. However, there's nothing to say that another pump couldn't be pulling from the ocean and mixing the brine into that so it's diluted before and not just pouring brine straight into the ocean
Regardless, it is totally possible to reintroduce the brine back to the ocean in a way to not be a shock to the local area. We have just chosen to make it harder on ourselves for some illogical reason.
Alternatively, in the absence of sensible regulations a cutthroat operator devoid of ethics constructs a plant that dumps concentrated brine in the immediate vicinity because that's the cheapest approach. Then reactionary elements raise talking points about environmental damage and pretend that it's a difficult problem to solve. Business as usual.
It’s obvious you can safely put salt back into the ocean with enough dilution. I bet a middle schooler could design a system to do it.