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ajb 8 hours ago [-]
There is a fundamental minimum amount of energy needed to desalinate: you can't take less energy to do it,than you could gain back (from osmotic pressure) if you allowed the desalinated water to expand a cylinder containing the residual brine. This is large. This paper is a thermal method, so it doesn't have an electricity input, but to justify their efficiency claim, they should really compare against what you could do by using the same surface area for solar panels, driving a conventional setup. My (limited) understanding is that conventional reverse osmosis is not far from the theoretical optimum, energy-wise, the main difficulties being operational (the membranes need declogging). And of course RO is more expensive than rain.
This paper is interesting, however, in directly producing crystalline salt, which is lower volume than brine and easier to dispose of, maybe even valuable.
otterdude 2 hours ago [-]
Thermal methods require energy, it seems like this substrate is effective at maintaining its solar-thermal absorbing properties better than a material that will attract salts
> 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
CuriouslyC 6 hours ago [-]
If this can be applied to mine effluent, you could replace the maybe with most certainly. Sulfuric acid effluent lakes leech all sorts of valuable metals out of the ground.
8 hours ago [-]
cyberax 4 hours ago [-]
> My (limited) understanding is that conventional reverse osmosis is not far from the theoretical optimum, energy-wise, the main difficulties being operational (the membranes need declogging). And of course RO is more expensive than rain.
RO is about 2-4x the theoretical minimum, depending on how much water you're willing to reject.
xyzzyz 6 hours ago [-]
Brine is very easy to dispose of: you just pump it back to where it came from. Solid crystalline salt, on the other hand, is a hassle.
ceejayoz 5 hours ago [-]
> Brine is very easy to dispose of: you just pump it back to where it came from.
Easy, but not necessarily good for the spot you're pumping concentrated salt back into.
ashdksnndck 2 hours ago [-]
If you use fat pipes that go a decent distance from shore, diluting your brine with ocean water, you’ll have a negligible impact on the ocean. The problem is if you dump lots of brine in shallow waters. Old designs did have that flaw, but it’s not that difficult to design around this constraint now that we know about it.
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.
SoftTalker 5 hours ago [-]
The brine came from the ocean. So just dilute it back to close to ambient salinity using municipal waste water that you are discharging anyway.
ceejayoz 5 hours ago [-]
> The brine came from the ocean.
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?
Joker_vD 3 hours ago [-]
> Sure, and enriched uranium comes from the ground
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.
numpad0 2 hours ago [-]
Japan is also barred from doing own enrichment, being a non-nuclear state. Though, there nevertheless is a dormant set of requisite facilities.
SoftTalker 5 hours ago [-]
The analogy would be if you "un-enrich" it. Then it's safe. Or at least no worse than when you took it out of the ground.
ceejayoz 5 hours ago [-]
> The analogy would be if you "un-enrich" it.
But you're doing that with the same water you're trying to make in the first place!
SoftTalker 5 hours ago [-]
You could just dilute it using fresh seawater, if you used enough and (maybe) spread it over a wider area. The amount of water people need for drinking is a relative drop in the ocean.
ceejayoz 5 hours ago [-]
Brine doesn't necessarily behave the way you imagine.
You can dilute the brine in a facility before disposing.
ceejayoz 2 hours ago [-]
Go on. With what?
asdff 16 minutes ago [-]
Seems like you could just dilute it with seawater at like 100:1 ratio and it would be negligible done offshore. We already dump our shit 5 miles out.
pasquinelli 11 minutes ago [-]
gasoline
wlesieutre 2 hours ago [-]
With fresh water, we’ll get it from desalinization! Hey wait a second…
Enginerrrd 5 hours ago [-]
Municipal waste water is a much cheaper way to get desalinated water in the first place though.
lazide 4 hours ago [-]
except for the pharmaceuticals anyway
shermantanktop 2 hours ago [-]
Hey, it's free viagra, prozac, progesterone and multivitamin supplements, all in a glass.
xyzzyz 2 hours ago [-]
Maybe, but dumping crystalline salt is even worse to the spot you’re dumping it on.
asdff 14 minutes ago [-]
It doesn't need to be crystalline salt. Just mix the brine with seawater at a really high ratio of sea water to brine then dump that out. 100:1 ratio should be fine I would guess. Quick search suggests seawater salinity variance is already like 10%-15% or so. Even better if you pipe it offshore where currents will take it and not somewhere that doesn't circulate.
card_zero 2 hours ago [-]
I wonder. It would have to dissolve, a big block of salt would take a while, kind of like the erosion of cliffs where the salt comes from in the first place. Eh, I guess you're right though, the fish wouldn't like that at all.
galaxyLogic 5 hours ago [-]
I think I read somewhere that salt can be used as energy storage medium? So we could get both water and batteries for renewal energy.
xyzzyz 2 hours ago [-]
It’s about thermal storage, you don’t use table/sea salt for that, and you don’t need a lot of salt, because the salt is in a closed loop; it’s not being consumed.
galaxyLogic 1 hours ago [-]
But more thermal storage you want more salt you want, and it's gotta cost something, right?
If you read the article you sent me, you'll learn that, just as I said, you don't use sodium chloride, aka table salt, aka sea salt, for these purposes.
qurren 5 hours ago [-]
Why? Just build mountains out of it and maybe even open a salt-ski park in the tropics for people who don't have snow.
asdff 12 minutes ago [-]
There are salt mountains lining most midwestern freeways as it is for winter.
RobotToaster 4 hours ago [-]
> Solid crystalline salt, on the other hand, is a hassle.
Just put it on your fries.
nkrisc 5 hours ago [-]
In an ideal world that crystalline salt by product could be used to offset any imported or mined salt, further reducing the environmental impact of those operations.
5 hours ago [-]
lightedman 5 hours ago [-]
"Solid crystalline salt, on the other hand, is a hassle."
Just make prettier-than-Himalayan salt lamps out of it and sell it to hippies. Easy solution.
cyanydeez 2 hours ago [-]
yeah, if you like to kill everything in a few 100 feet radius and kill some more in the zone of reliance.
this is delusional ecological
xyzzyz 2 hours ago [-]
Brine might be bad to the place you dump into, but crystalline salt is even worse.
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.
aaron695 42 minutes ago [-]
[dead]
Animats 6 hours ago [-]
The paper: [1]
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.
It reminds me of how the Panama canal was built, and actually the first major attempt failed and they gave up. What they learned for the second attempt was that digging was not the hard(est) part to solve - it was how to move the dirt! So much dirt!
Great book on this BTW: Path Between the Seas. I couldn't put it down.
Animats 5 hours ago [-]
Fragility is a common problem in surface treatments, sometimes called "nanotechnology". There are super hydrophobic surface treatments that are very effective.
They generate a surface which is a forest of tiny sharp points. The surface tension of water is too high to cling to such a surface. You can make something that just will not get wet.
The problem is that the points are fragile, and wear destroys the effect.
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.
pchristensen 4 hours ago [-]
It's such a good book! Like any dad reading history, I have been annoying my family for years with fun facts I learned in that book. David McCullough's other books like The Great Bridge (about building the Brooklyn Bridge) are also great.
Nifty3929 1 hours ago [-]
You and I are the same person apparently. Let me tell you about malaria! Or the bends! Or tetanus! Please! Wait, where's everybody going?
jmward01 5 hours ago [-]
This is an interesting tech, but I have big doubts. In the picture you can see some salt coating the surface. Even just a little seems like too much for this type of system. I really hope they can make this work and scale this up.
YeGoblynQueenne 2 hours ago [-]
>> The solar-powered system uses specially engineered black metal to absorb sunlight.
The new system replaces the earlier version that used specially engineered death metal.
BLKNSLVR 1 hours ago [-]
Which was a big upgrade from the prior system which just used a heavy rock.
fhdkweig 8 hours ago [-]
This appears to be the same New Rochester article as 4 days ago with 20 comments.
Awesome, love seeing stuff out of Rochester - RIT or UofR or any of the nearby schools.
Totally underrated area for academic pursuits.
mmmBacon 6 hours ago [-]
UofR physic grad that also worked at the LLE here. Agree Rochester schools are underrated (although admittedly a little biased).
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.
haritha-j 6 hours ago [-]
Indeed, it’s the same university that gave us room temperature superconductors.
0x59 7 hours ago [-]
Agree! Shout out to the Laboratory for Laser Energetics
dyauspitr 6 hours ago [-]
RIT is pretty well known as a good school I believe.
gaiagraphia 4 hours ago [-]
Always wondered why the coast of the Red Sea isn't littered with channels which get flooded with seawater, which then evpporate into glassed ceilings; creating freshwater, and leaving behind salts for mining.
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.
dirt_like 4 hours ago [-]
Slightly different idea to take Red Sea water, concentrate it, and flow into the Dead Sea to stabilize the water level in the Dead Sea which is a big problem. A billion or so was spent but the project is on hold for some combination of financial, political and environmental issues.
I love projects like this. A shame the west has handed over the baton to the Chinese and Saudis when it comes to actually being daring with megaprojects.
(Similar ideas proposed for Lake Eyre, the lakes in Tunisia, and the Afar Depression in Djibouti, too).
AlexandrB 32 minutes ago [-]
The Saudis aren't "daring" with megaprojects. They're fucking[1] stupid[2]. Saying their megaprojects are "daring" is like saying I'm "daring" for claiming I'm going to build a catapult that will launch me to the moon.
A comparison that only works if you say it and sink a few billion into foundations for said catapult.
jrumbut 4 hours ago [-]
If you've ever been to the beach, you can smell the salt air and rotting seaweed and hear the birds.
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.
gaiagraphia 3 hours ago [-]
The Saudis were fucking around with the idea of solar domes at one point. Haven't heard anything about it for a while though (probably due to maths, lol). A shame, I've always been fascinated by Egypt and the empty expanses of nothingness. On long bus journeys around the country, the imagination can run wild.
So crazy question: take a dehumidifier, attach some solar panels, and deploy at scale for non-potable water suitable for crop irrigation anywhere that isn't a desert. Does it work? And if not, why?
LarsAlereon 6 hours ago [-]
It takes too much energy and produces water too slowly to scale. In general any area with sufficient moisture in the air to explore this also has easier access to rain and ground water.
LogicFailsMe 6 hours ago [-]
Great point, in my case in the PNW, the water from my local well is infested with manganese (as in clogging the household plumbing in the absence of a sediment filter) and other contaminants and the water company providing it is owned by private equity. Legally, I can drill my own well for non-potable irrigation, but god forbid I filter and/or chlorinate it for my own household use. So I end up considering options like this, thanks for debunking.
SoftTalker 5 hours ago [-]
You don't need to chlorinate water from your own well, unless maybe you have a cistern that you are filling for storage.
And who's going to know if you are drinking it or watering your garden?
LogicFailsMe 4 hours ago [-]
At the very least I would UV disinfect anything coming from the ground and absolutely make use of a 20 micron sediment filter if only to address cognitive load: Another place, another time, coliform bacteria from the well. Super fun(not).
oceanplexian 2 hours ago [-]
The short answer is all those problems have already been solved.
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.
wagwang 4 hours ago [-]
The humid areas where they might work probably already have a lot of water?
mrguyorama 6 hours ago [-]
It "works" in the sense that this is what 99% of "Get water from air" scams are.
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.
casey2 6 hours ago [-]
What do you mean work? No, because there is no single dehumidifier on the market that will get you enough water, so you are out $80 grand, you could have just paid for water delivery.
5 hours ago [-]
scythe 7 hours ago [-]
They are talking about lithium recovery, but there is a less exotic byproduct I'm interested in. One tonne (≈ 1 m^3) of seawater contains about 1.3 kilograms of magnesium, equivalent to about 4 kg of magnesite ore. Typical desal prices are on the order of $1 per tonne. Magnesite ore goes for about $100 per tonne, so the crude magnesium in a tonne of seawater is worth about $0.40, which could account for a substantial fraction of the desalination cost. (These numbers are very rough.)
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.
cjbenedikt 4 hours ago [-]
Calcining Mg(OH)₂ -which is what you find in seawater -
converts the soft compound into magnesium oxide, a valuable mineral commonly used in refractories, catalysts, and ceramics.The Chemical Equation: \(Mg(OH)_2 \xrightarrow{\Delta} MgO + H_2O\)Temperature Requirements: You need to heat the magnesium hydroxide to a temperature range between 500°C and 900°C. Heating at the lower end (around 500°C) yields a highly reactive, porous form of nano-MgO, while heating above 1,200°C creates "dead-burned" MgO used in high-heat industrial bricks.The Yield: The weight of your final MgO product will be roughly 69% of the original Mg(OH)₂ mass, as the evaporated water accounts for the 31% weight difference.
Already energy intensive. To get to magnesium ore is another step.
scythe 2 hours ago [-]
>Calcining Mg(OH)₂ -which is what you find in seawater
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.
noripcord 5 hours ago [-]
you can now extract (like mining) minerals from the ocean, sounds kind of dangerous for the ecosystem maybe? making it profitable to extract magnesium, lithium, salt... we can probably guess how this story goes.
i'm hoping it doesn't scale, honestly.
fc417fc802 40 minutes ago [-]
You're wildly underestimating the scale of the ocean. If we could extract all our necessary minerals from it rather than mining them that would alleviate a huge cause of environmental damage.
card_zero 5 hours ago [-]
You're worried we might use all the salt in the sea for some kind of ... salt pyramids, send the water back out through sewers, and consequently leave the world's oceans diluted? That's about 1 followed by 21 zeroes, I think, in liters.
noripcord 3 hours ago [-]
no, just take the water, remove the salt & minerals. Over time it'll dilute. Water falls again in the form of rain, obviously, but not the salt.
You're not worried? If it's for batteries? For sure they'll extract whatever they can.
card_zero 3 hours ago [-]
Right, remove the salt and minerals. We don't need that much salt, so we'd have to build pyramids or something with it. We drink the water, but then it ends up back in the oceans. The reason I mention that part is because if it didn't, if we could destroy the water, then the remaining water would retain the same salinity, and the concern would be that we drain the ocean dry, which is silly (I refer you back to how big it is). But we don't destroy water when we use it, so instead the worry is that we dilute all the world's ocean, which is also silly (I again refer you back to how big it is). We need a lot of batteries, but the sea is not useful as a source of lithium except as a byproduct. Even if it was the only source, the old batteries themselves would soon become a better source, as concentrated stores of lithium compared to the very-much-not-concentrated lithium in the ocean. But anyway the good places to mine lithium are on land (and are dried-up bits of ancient ocean, I think).
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.
photochemsyn 6 hours ago [-]
After looking at the paper, this looks like the core result:
“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?
nandomrumber 2 hours ago [-]
I’m not even going to night clicking on a title that is clearly a load of bullshit.
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.
excalibur 5 hours ago [-]
> The solar-powered system uses specially engineered black metal to absorb sunlight.
Brutal. 𖤐 \m/ 𖤐
shevy-java 4 hours ago [-]
If true then this might be indeed a game changer, but numerous
academic publications turned out to be unfit for upscaling.
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.
kogasa240p 6 hours ago [-]
Probably some of the best news I've seen in a while.
mkl 7 hours ago [-]
> without waste
...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".
eimrine 7 hours ago [-]
Persian Gulf has 20% more salt in water because of the humans which are throwing the oversalinated waste back into the sea. Dehidrated salt may be a big deal for some areas because of no waste into input.
Jblx2 7 hours ago [-]
>Persian Gulf has 20% more salt in water because of the humans
I would like to read more about this from an authoritative source.
tdb7893 7 hours ago [-]
Through the magic of Googling "Persian Gulf salinity" it seems like it's more that it's a shallow Gulf in a dry area so it has significant evaporation. Desalination does effect it but it's only a few percent of the total evaporation (which is still surprisingly big) and doesn't sound like the main driving factor or an imminent ecological concern.
pardon my ignorance. But, all that salt was there already. right? Is it that we have less water there now ?
fc417fc802 25 minutes ago [-]
If salt and water flow in but only water flows out you will be left with salt. Same reason that concentrated brine comes out of a desalination plant, or that the dead sea is what it is.
Jblx2 6 hours ago [-]
I thought the HN-way was to be more charitable than just directly calling out obvious bullshit.
mkl 1 hours ago [-]
The brine is waste, and the dehydrated salt is also waste. Maybe dry waste is better, but it's still waste.
7 hours ago [-]
fluorinerocket 6 hours ago [-]
Can we please ban university press releases
cush 5 hours ago [-]
why
doublerabbit 7 hours ago [-]
What about removing oil from water, have we conquered that yet?
5 hours ago [-]
7 hours ago [-]
kaonwarb 8 hours ago [-]
This reads like hyperbole:
> 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.
rconti 8 hours ago [-]
Sure, but typically desalination plants are located in a single physical place, so a discharge pipe dumping brine 24x7 is bad for all of the things around it, as the local concentration is extremely high.
joshred 8 hours ago [-]
Seems like you could run a long perforated tube to diminish that effect.
dieselgate 7 hours ago [-]
I wonder what the linear diffusion gradient would look like for that. Like the perforated garden hoses or whatever for soaking soil. Aquatic organisms grow so quick though very curious on the constraints for something like this.
dylan604 8 hours ago [-]
I liked the idea of loading it up on a ship that sails out releasing as it goes out and back. Make it solar powered or even go old school with literal sails.
sgc 7 hours ago [-]
I thought they tend to pipe far out and discharge as far below the surface as possible, since there is a lot of surface life and it is less damaging this way.
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.
dylan604 4 hours ago [-]
Ships wouldn't need a long submerged pipe. It'd just need a small hole like a bilge drain or maybe a live well on a fishing boat. Just let the boat cruise around slowly draining back into the ocean.
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
scythe 7 hours ago [-]
If you want to be really clever about it, maybe the ship is powered by the brine.
I like this! Though I’m not sure the math works. That page says ideal efficiency for that system would be something like 0.75 kWh/m^3. Compared to 4000 to 5000 kWh/m^3 of diesel. Now we don’t need to be efficient since the point is to use up our “fuel” and we don’t need to cary cargo for this to make sense but with numbers like that, I don’t think our boat will be able to make enough power to move at all.
01100011 8 hours ago [-]
And it doesn't even need to be a rigid pipe. A flexible pipe made out of, say, waterproof fabric, could be cheaply made to extend miles while remaining open due to the pressure of the water pumped into it.
dylan604 8 hours ago [-]
Things left underwater tend to collect things on it which would make this much less porous over time.
XorNot 3 hours ago [-]
The short version is brine is weird: it's surprisingly resistant to diffusing and tends to flow more like an immisicible fluid. So you have to put quite a lot of effort into getting it to actually disperse rather then just fall to the seafloor.
fc417fc802 17 minutes ago [-]
That's silly, you'd mechanically mix it with seawater rather than wait for it to diffuse. The concern would be the volume of desalinated water extracted from the local region versus the flux from ocean current. As long as that ratio is acceptable there won't be any long term problem.
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.
bilsbie 6 hours ago [-]
The brine thing is just a way to shut down conversation and let people feel superior for claiming there are no solutions to our problems except to reduce our standard of living.
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.
gausswho 7 hours ago [-]
It kinda depends where it's deposited, right? The expected AMOC collapse is fundamentally about salt imbalance.
wolfi1 8 hours ago [-]
depends of course, how easy does the brine dissolve, how long does it take that it is so diluted that it can't do any harm, without that information it's not easy to tell
dylan604 8 hours ago [-]
These are often built near shallower parts along the coast where changes are more pronounced.
boxed 7 hours ago [-]
I mean.. we really want to permanently desalinate the ocean somewhat too so putting the brine back seems kinda stupid. Put it on land, let it dry, sell some as table salt and dump the rest into abandoned mines.
wizzwizz4 6 hours ago [-]
Excellent idea! The largest abandoned mines I'm aware of are salt mines, which… hang on.
This paper is interesting, however, in directly producing crystalline salt, which is lower volume than brine and easier to dispose of, maybe even valuable.
> 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
RO is about 2-4x the theoretical minimum, depending on how much water you're willing to reject.
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.
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.
But you're doing that with the same water you're trying to make in the first place!
https://en.wikipedia.org/wiki/Brinicle
https://en.wikipedia.org/wiki/Brine_pool
https://en.wikipedia.org/wiki/Molten-salt_battery
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.
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.
[1] https://www.nature.com/articles/s41377-026-02315-4
[2] https://www.youtube.com/watch?v=BKYOglHYo_Y
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.
The new system replaces the earlier version that used specially engineered death metal.
https://news.ycombinator.com/item?id=48349507
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.
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).
[1] https://en.wikipedia.org/wiki/Trojena
[2] https://en.wikipedia.org/wiki/The_Line,_Saudi_Arabia
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...
And who's going to know if you are drinking it or watering your garden?
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.
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.
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.
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.
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.
“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?
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.
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.
...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...
> 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
https://en.wikipedia.org/wiki/Osmotic_power
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.