A new class of materials that can passively harvest water from air(blog.seas.upenn.edu)
blog.seas.upenn.edu
A new class of materials that can passively harvest water from air
https://blog.seas.upenn.edu/penn-engineers-discover-a-new-class-of-materials-that-passively-harvest-water-from-air/
206 comments
It's research-in-progress, but I think the promise is slightly different from dehumidifier bags (also in other parts of the world, Thirsty Hippos [1]) which are single use.
You're correct in that: (1) it doesn't break the law of physics; (2) to remove the droplets, you still need energy. But it sounds like if the droplets are moving to the surface, the energy needed to release the droplets could be far lower than most active dehumidification methods (e.g. Peltier junctions).
[1] Thirsty Hippos -- which are very effective in small spaces.
https://www.amazon.sg/Thirsty-Hippo-Dehumidifier-Moisture-Ab...
Basically a supercharged silica gel.
You're correct in that: (1) it doesn't break the law of physics; (2) to remove the droplets, you still need energy. But it sounds like if the droplets are moving to the surface, the energy needed to release the droplets could be far lower than most active dehumidification methods (e.g. Peltier junctions).
[1] Thirsty Hippos -- which are very effective in small spaces.
https://www.amazon.sg/Thirsty-Hippo-Dehumidifier-Moisture-Ab...
Basically a supercharged silica gel.
Probably a small piezo junction could be used to provide a solid-state vibrator for releasing water from a proportionately considerably larger area of the material, or at larger scales perhaps a technique similar to the ultrasonic sensor cleaners built into interchangeable-lens cameras.
Do you mean like an ultrasonic humidifier[1]?
[1] https://www.amazon.com/Ultrasonic-Humidifiers/s?k=Ultrasonic...
[1] https://www.amazon.com/Ultrasonic-Humidifiers/s?k=Ultrasonic...
Sure, why not?
> > Ultrasonic humidifier
> Sure, why not?
https://dynomight.net/air/ estimates that using an ultrasonic humidifier for one night shortens your life by 50 minutes. Getting rid of any ultrasonic humidifiers is his top tip to extend your life cheaply.
Dedicated post on them: https://dynomight.net/humidifiers/
> Sure, why not?
https://dynomight.net/air/ estimates that using an ultrasonic humidifier for one night shortens your life by 50 minutes. Getting rid of any ultrasonic humidifiers is his top tip to extend your life cheaply.
Dedicated post on them: https://dynomight.net/humidifiers/
That was a great read. I didn’t know that blog and a quick glimpse at the about page made me bookmarked it. Thanks for sharing.
I've got some bad news if you live near a road.
I am aware that cars are ruining millions of people's health. That car drivers are privatising the convenience and externalising the harms of driving. That car drivers are a privileged, wealthy, class of people who can literally kill others and walk away without a jail sentence using the defence "I didn't see them":
https://www.cambridge-news.co.uk/news/cambridge-news/cyclist...
https://www.cyclingweekly.com/news/latest-news/driver-carele...
https://veronews.com/2022/08/06/no-jail-time-for-driver-of-c...
many other examples exist
https://www.cambridge-news.co.uk/news/cambridge-news/cyclist...
https://www.cyclingweekly.com/news/latest-news/driver-carele...
https://veronews.com/2022/08/06/no-jail-time-for-driver-of-c...
many other examples exist
Sure. And if any particulate emitted by an ultrasonic humidifier could be dangerous enough to shorten your life by ~10% with consistent use or 50 minutes per roughly 8-hour night's sleep as this timecuber of yours appears to claim, then I should think the tire and brake dust burden anywhere near an actively used road would be not just instantly but flagrantly fatal.
I'm aware of the hundred thousand words spent justifying the idea. I will consider reading them once I've been convinced to ignore the result of this trivial - and I do use the following phrase with careful consideration aforethought - sanity check. You'll more likely give the goalpost another kick, though, I suspect.
I'm aware of the hundred thousand words spent justifying the idea. I will consider reading them once I've been convinced to ignore the result of this trivial - and I do use the following phrase with careful consideration aforethought - sanity check. You'll more likely give the goalpost another kick, though, I suspect.
Explain where I have given any goalposts any kick at all?
From the articles:
> A good heuristic is that an increase of 33.3 PM2.5 μg/m³ costs around 1 disability-adjusted life year. Correia et al. (2013) estimated something close to this from different counties in the US, and more recent data from many different countries confirm this. The most polluted cities in the world have levels around 100 PM2.5 μg/m³.
> When inhaled during an 8-hr exposure time, and depending on mineral water quality, humidifier aerosols can deposit up to 100s of μg minerals in the human child respiratory tract and 3–4.5 times more μg of minerals in human adult respiratory tract. > (Yao et al., 2020)
The amount of particles people breathe in in a night of worst case ultrasonic humidifier use is 8x more than the particle level in the air of the most polluted cities in the world.
From the articles:
> A good heuristic is that an increase of 33.3 PM2.5 μg/m³ costs around 1 disability-adjusted life year. Correia et al. (2013) estimated something close to this from different counties in the US, and more recent data from many different countries confirm this. The most polluted cities in the world have levels around 100 PM2.5 μg/m³.
> When inhaled during an 8-hr exposure time, and depending on mineral water quality, humidifier aerosols can deposit up to 100s of μg minerals in the human child respiratory tract and 3–4.5 times more μg of minerals in human adult respiratory tract. > (Yao et al., 2020)
The amount of particles people breathe in in a night of worst case ultrasonic humidifier use is 8x more than the particle level in the air of the most polluted cities in the world.
And of course every relationship is both bijective and linear from one data point over an infinite domain.
We could talk about this utter misrepresentation of https://pubmed.ncbi.nlm.nih.gov/23211349/ but why? You haven't read it. You won't. At most you will follow the examples you cite in prooftexting from it like a Southern Baptist inveighing against homosexuality. Kindly find someone else whose time so to waste.
We could talk about this utter misrepresentation of https://pubmed.ncbi.nlm.nih.gov/23211349/ but why? You haven't read it. You won't. At most you will follow the examples you cite in prooftexting from it like a Southern Baptist inveighing against homosexuality. Kindly find someone else whose time so to waste.
I said, explain where I kicked any goalposts. You haven't, because I didn't. Ad-homs, against the author and against me, pre-deciding your conclusion, refusing to explain your objections, pretending "we could talk about it" while turning to insults to shut down any talking about it.
I get it, you're desperate to appear smart and superior, but arguing that lamely isn't doing it. Of course I'm not going to read your link, try and guess what misrepresentations you're coming up with, make some argument about them and their context in the wider post, only for you to ignore it and post some more nonsense in response. Or engage with you further.
I get it, you're desperate to appear smart and superior, but arguing that lamely isn't doing it. Of course I'm not going to read your link, try and guess what misrepresentations you're coming up with, make some argument about them and their context in the wider post, only for you to ignore it and post some more nonsense in response. Or engage with you further.
This isn't reddit. Please kindly take your anger, ad homonims, and bad-faith arguments back over there. I'm sorry you had a bad day but nobody in this thread caused it, so take a deep breath.
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Yes this requires energy to extract the water, but if it's much less energy than dehumidifiers -say, one order of magnitude less- then it could make harvesting water from humid air economical.
Dehudifier bags (e.g. silica, CaCl) aren't single-use. Microwave, then reuse. Some even are color-changing so you know how much moisture they've absorbed.
Microwaving is adding energy, obviously. But the idea here is that the water is recoverable, not that the air is now drier.
Concur; the idea behind this class of devices is to take advantage of a daily humidity cycle. Whether it's CaCl (absorption) or Silica (adsorption), or the latest lab-designed adsorption surface.
This is a good time to note that I see one of these articles ~once every two years, for the past 10 years. I haven't observed one make it beyond the initial discovery phase.
This is a good time to note that I see one of these articles ~once every two years, for the past 10 years. I haven't observed one make it beyond the initial discovery phase.
This, and solutions for male pattern baldness.
Male pattern baldness is a solved problem, if caught early enough; people just don't usually bother, because the cleanest solution (a 5α-RI) can interfere with sexual function, the "proper" fix for that (low-dose topical application) is time-consuming (so people normally just kludge it with Viagra), and the medicines involved can (indirectly) cause breast growth with prolonged use (unlikely to be a problem with low-dose topical application, and can also be mitigated, although overshooting that mitigation can cause osteoporosis) and are "don't even touch this if you're pregnant" class (they can interfere with fœtal development).
Started with topical Minoxidil at age 21. Have (almost) a full head of hair. Now I take it in pill form.
No breasts. And no other issues.
No breasts. And no other issues.
Minoxidil is a sledgehammer: it's got all sorts of other effects (e.g. reducing your blood pressure, beta something something). I wouldn't expect it to cause breast development, though, since it doesn't act on œstrogen receptors.
You seem knowledgeable. Where's a safe place to order the topical application from? I'm not in the US or Europe, our doctors aren't going to be bothered with (or knowledgeable about) something like treating baldness.
My Gmail username is the same as my HN username if you prefer to answer in private. Thanks
My Gmail username is the same as my HN username if you prefer to answer in private. Thanks
I don't have the savvy for stuff like actually acquiring medicines, unfortunately. You might be able to just buy it from your local pharmacy; but if not, you could check https://hrtcafe.net/ or – as a sibling commenter suggested – look into minoxidil (which works via a different mechanism). I wouldn't recommend minoxidil unless its other effects would be beneficial to you, since I'm leery of things that affect blood pressure and circulation – but I'm not actually trained in this stuff, so maybe it's considered safer.
Finasteride is less potent, but is normally recommended for cis men; not sure why. Theoretically, I'd expect dutasteride to be the better medication (and https://doi.org/10.2147/CIA.S192435 bears that out) if you can get hold of it.
I'd have thought finasteride and dutasteride weren't safe to take if there's a chance of you getting someone pregnant, but https://www.nhs.uk/medicines/finasteride/fertility-and-pregn... says it's fine, actually. https://doi.org/10.4103/0974-1208.86093 goes into more detail on that. (I'm not aware of any other impacts on fœtal development, only the intersex condition mentioned in that article – note that the backdoor pathway described in https://doi.org/10.1002/dvdy.23892 also requires the 5α-reductase enzyme –, but I'd still advise caution.)
Finasteride is less potent, but is normally recommended for cis men; not sure why. Theoretically, I'd expect dutasteride to be the better medication (and https://doi.org/10.2147/CIA.S192435 bears that out) if you can get hold of it.
I'd have thought finasteride and dutasteride weren't safe to take if there's a chance of you getting someone pregnant, but https://www.nhs.uk/medicines/finasteride/fertility-and-pregn... says it's fine, actually. https://doi.org/10.4103/0974-1208.86093 goes into more detail on that. (I'm not aware of any other impacts on fœtal development, only the intersex condition mentioned in that article – note that the backdoor pathway described in https://doi.org/10.1002/dvdy.23892 also requires the 5α-reductase enzyme –, but I'd still advise caution.)
Thank you. This is an extremely informative comment that gives me many avenues to pursue. Much appreciated.
If I have to relinquish my sexual function and grow breasts to reduce baldness, then baldness is not a solved problem.
Low-dose topical application doesn't have those problems. Heck, even "dose your entire body" doesn't always lead to sexual dysfunction. (And breast development is a rare side-effect that you'd notice before anything permanent happens, and is easily-addressed.) However, it is topical application of a medicine that can interfere with fœtal development.
Oh, almost forgot: any messing around with sex hormone levels puts you at risk of depression. That's big side effect #3 (though again, many people don't even notice it).
Oh, almost forgot: any messing around with sex hormone levels puts you at risk of depression. That's big side effect #3 (though again, many people don't even notice it).
out of curiosity, what else would you expect the side effect profile of something mediating the effects of a potent androgen on the body to look like?
it's not estrogen where you would expect breast growth (and can't count on any particular changes to sexual function anyway), it's inhibiting conversion of testosterone to dihydrotestosterone which could have that effect, much like you could spontaneously develop gynecomastia without intentionally fiddling with your hormone balance. calling it unsolved sounds a lot like calling the very many conditions with medications that have more likely and worse side effects equally unsolved.
it's not estrogen where you would expect breast growth (and can't count on any particular changes to sexual function anyway), it's inhibiting conversion of testosterone to dihydrotestosterone which could have that effect, much like you could spontaneously develop gynecomastia without intentionally fiddling with your hormone balance. calling it unsolved sounds a lot like calling the very many conditions with medications that have more likely and worse side effects equally unsolved.
> what else would you expect the side effect profile of something mediating the effects of a potent androgen on the body to look like?
That's what the patient information sheet is for, and why everyone's supposed to have access to a trained medical professional they can freely consult for things like this.
> it's not estrogen where you would expect breast growth
Actually, it is. Reducing DHT levels causes the body to elevate both testosterone and œstrogen levels, via homeostasis. But yeah, it's not a direct effect, and if it's a problem you can twiddle further to make it go away. (You could even do that pre-emptively, though you normally get days and days of warning before breast development actually starts, so I'd advocate the "wait and see" approach.)
Actually, it is. Reducing DHT levels causes the body to elevate both testosterone and œstrogen levels, via homeostasis. But yeah, it's not a direct effect, and if it's a problem you can twiddle further to make it go away. (You could even do that pre-emptively, though you normally get days and days of warning before breast development actually starts, so I'd advocate the "wait and see" approach.)
A condition is typically considered solved if there are drugs or procedures that cure it and either (a) have extremely rare side effects, or (b) have side-effects that are not as big a problem as the condition they are curing. If a pill existed that cured trh common cold but had a 1% chance of giving you cancer of the throat, people wouldn't proclaim "we've cured the common cold!".
By the 24th century, no one will care that you are bald.
I'm doubtful that President Camacho could've gained so much power without that fantastic coif
Unless you are Brian “Hairlacher” formerly of the Chicago Bears and shilling hair replacement on Chicago area billboards for years now.
Devices that automate this are readily available, I have one running now. "Desiccant dehumidifiers."
If something breaks the laws of physics it simply means the laws of physics were incomplete, so we update them and now it no longer breaks them
However, if something claims to break the laws of physics, 99 times out of 100, it simply means that either a) the person making the claim missed something, or b) the person making the claim is lying.
Or c) the person making the claim has no interest in the truth, but strong interest in some other thing.
Which is the same as b)
Don't complicate
Don't complicate
It is really as simple as that and even applies to soon what will seem like free energy. It is not free energy, it is just energy from a field we were previously ignoring and previously fighting against.
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What is the source of this seemingly free energy that we've been ignoring and fighting against (I assume at different points in time)?
For example, Earth's magnetic field has been claimed as a source of "free" energy.
Those are usually just calcium chloride in a bag, it's very hygroscopic and fairly cheap... also makes a halfway decent de-icer. The issue I see with this thin-film method is that no mention is made of the rate of production at a given relative humidity for a given area of the film.
It's interesting, but without the details (and with a lot of PR speak) I'm skeptical as hell about this in practice.
It's interesting, but without the details (and with a lot of PR speak) I'm skeptical as hell about this in practice.
Thanks for the explanation. My first thought reading the headlines was somebody thinks they discovered a perpetual motion machine.
What is the theoretical limit on the energy cost to remove water from air? A dew years back 3m had some super inexpensive way that invovled a reusable water andorber that released its water under only slightly decreased pressure and slightly increased temperature. The incoming air and the waste heat from the downstream ac unit provided all the warming with the pressure change being all that was necessary. It had two banks so one could dump water while the other absorbed. It made the whole system rund double digiymore efficient than just the ac alone. And that was neglecting that the felt temperature would be lower with the dessicated air.
> "remove water from air? A dew years back"
"dew" was a funny typo there :)
"dew" was a funny typo there :)
The loss of tactile keyboards on mobile devices is a tragedy.
The red flags in the uni PR are not so curious compared to the ones in the paper.
From figure 4 (& backed up by simulation fig 3E) it looks like stuff begins to happen only at 97% relative humidity & after a few minutes (at micrometer scale)
https://www.science.org/doi/10.1126/sciadv.adu8349
Granted, it's almost easy enough to try at home: melt some poly gloves into "freeze dried" silica powder
From figure 4 (& backed up by simulation fig 3E) it looks like stuff begins to happen only at 97% relative humidity & after a few minutes (at micrometer scale)
https://www.science.org/doi/10.1126/sciadv.adu8349
Granted, it's almost easy enough to try at home: melt some poly gloves into "freeze dried" silica powder
Is there some sort of conservation of energy question in this form of water collection that establishes some minimum amount of energy that would be required to collect 1L of water from the air?
I'd assume if the amount of energy required to collect the water is low then we're looking at something interesting.
I'd assume if the amount of energy required to collect the water is low then we're looking at something interesting.
Yes, water vapor condensing to liquid water at humidity below 100% is an exothermic reaction, and the amount of energy released is (per Google) 2259kJ/kg. So any device that wants to condense 1kg of water has to dissipate at least 2259kJ of energy somewhere, assuming it is in any way temperature-dependent (if it can keep condensing water even if it becomes hotter, then this is somewhat evaded).
For context, that amount of heat is five times the amount needed to heat 1kg of liquid water from 0° to 100°C (without thawing or boiling it). So it's not in any way a trivial amount.
For context, that amount of heat is five times the amount needed to heat 1kg of liquid water from 0° to 100°C (without thawing or boiling it). So it's not in any way a trivial amount.
Yeah, "harvesting" probably oversells it unless there's a passive or low-energy way to actually collect the water. Like, maybe coupling it with a wicking surface or capillary-driven transfer system could help, but that’s an open question.
Yes it is impossible to break the laws of physics. If they appear broken then it is only because our understanding was wrong. Similar, the laws cannot be “defied”. You can only do what the universe allows, nothing more.
So the question is how much more efficient is it? I spend hundreds of dollars per month running dehumidifiers in my house so I am keen to know.
Me too! Because dust mites? Curious to share notes with you, I’m running 4 aeockys right now but they don’t seem to last long
When a publication I was involved in got a university PR piece, they were in direct communication with us
University PR folk are sometimes quite scientifically illiterate. Their job is basically marketing. They need to turn an esoteric, jargon heavy, and heavily qualified paper into a hype piece that the money people can understand. Everything must be a ground-breaking, world-shaking, all-time first. They sometimes make dubious claims no matter how many times you tell them not to. Ultimately, they report to the university's money people and not to researchers.
If you want science, read journals. If you want to see who is likely to get more money, read university PR releases.
If you want science, read journals. If you want to see who is likely to get more money, read university PR releases.
Amusingly, I have the same experience as you and GP. Thee university wants to hear what the researchers have to say, but subsequently they decide independently what they're writing, strict scientific honesty be damned.
Honesty pays no bills for professional liars.
Like diplomats, they're sent abroad to lie for their university, and the university president cries all the way to the bank for the sins of his hirelings.
Like diplomats, they're sent abroad to lie for their university, and the university president cries all the way to the bank for the sins of his hirelings.
I've observed the same. University science PR pieces are usually unreliable -- they are optimized toward generating buzz than scientific accuracy. They usually link to the actual science papers, but the prose is usually a stretch.
Even in this case -- "defying the laws of physics" is sensationalist narrative manufacturing.
The real claim is actually more moderate, and the research is not really close to commercial yet.
Even in this case -- "defying the laws of physics" is sensationalist narrative manufacturing.
The real claim is actually more moderate, and the research is not really close to commercial yet.
From the actual paper ( https://www.science.org/doi/10.1126/sciadv.adu8349 ):
"All measurements were performed at 20° ± 0.2°C maintained by an air circulation system unless otherwise noted. The temperature of the films was controlled using a heating/cooling unit (THMS350V, Linkam Scientific Instruments, Salfords, UK) when necessary."
So the latent heat is conducted away by the cooling apparatus, it's just not explicitly stated, to sound more sensational.
"All measurements were performed at 20° ± 0.2°C maintained by an air circulation system unless otherwise noted. The temperature of the films was controlled using a heating/cooling unit (THMS350V, Linkam Scientific Instruments, Salfords, UK) when necessary."
So the latent heat is conducted away by the cooling apparatus, it's just not explicitly stated, to sound more sensational.
Another part from the paper that a lot of people here seem to be ignoring: "Specifically, macroscopic water droplets isothermally form when the NP size is ≤22 nm, RH is >~90%, and ϕPE ranges from 0.05 to 0.35." and "Initial water droplets that are observable under optical microscopy (~1 μm in size) appear within a few seconds after being exposed to 97% RH."
This is really moist air that's only barely short of forming dew. A lot of people are focusing on sensational "violation of physics", when it's an incremental improvement on process that happens naturally.
This is really moist air that's only barely short of forming dew. A lot of people are focusing on sensational "violation of physics", when it's an incremental improvement on process that happens naturally.
I think the interesting bit is less about "breaking physics" and more about how finely tuned the material is to encourage this behavior without external cooling.
Keeping the temperature constant with a thermostat is not an issue here. That would only explain things if the surface were kept cooler than the surrounding air (below the dew point), but from the description in the paper that does not seem to be the case. They basically claim that macroscopic droplets form spontaneously from an unsaturated vapor. And no, this is not something permitted by the second law of thermodynamics.
> And no, this is not something permitted by the second law of thermodynamics.
— Sir Arthur Stanley Eddington, The Nature of the Physical World (1927)
While I generally agree that it sounds dubious, this argument depends on whether the entropy of the liquid in the pore is lower than the entropy of the vapor in the air in the pore. I could see a highly hydrophilic capillary restricting a vapor enough to where it has better entropy in a liquid state.
If that's true we just need to balance energy, which the cooler does.
If that's true we just need to balance energy, which the cooler does.
> I could see a highly hydrophilic capillary restricting a vapor enough to where it has better entropy in a liquid state.
My other comment here (and and a reply to a similar question) has more detail [1], but in short: this is true for capillaries and pores, it is not true for "collectable" droplets on a flat surface.
1. https://news.ycombinator.com/item?id=44099078
My other comment here (and and a reply to a similar question) has more detail [1], but in short: this is true for capillaries and pores, it is not true for "collectable" droplets on a flat surface.
1. https://news.ycombinator.com/item?id=44099078
Replied to that comment as well but per the article they're not droplets on a flat surface, but rather droplets connected to pores by surface tension.
Practically it just means that the energy to form the droplets is coming from somewhere else, just not via cooling the surface below the dew point. For instance, you could imagine something like squeezing a material that undergoes capillary condensation to get the water out, since you'd pay the requisite energy cost via mechanical work.
Ah that seems to explain it to me, if instead of presenting it as breaking some physics they should have said what actually makes it useful.
My understanding of it now is that since it can work at a higher temperature in an environment where the ambient temperature is low enough the latent heat can be passively radiated away. Even if using an active heat pump the higher temperatures would allow for a more efficient process. A closed system would eventually reach an equilibrium but there is no need to maintain a closed system.
My understanding of it now is that since it can work at a higher temperature in an environment where the ambient temperature is low enough the latent heat can be passively radiated away. Even if using an active heat pump the higher temperatures would allow for a more efficient process. A closed system would eventually reach an equilibrium but there is no need to maintain a closed system.
I think the work stands out anyway. Unlike adsorption techniques there is zero change to the mechanism which just keeps pulling water from the air. Presumably, they will put a layer of this material on aluminum to conduct the latent heat and have something that just produces water full time, without additional energy input. consider a 'cube' of fins of this stuff sitting in shade with a collection bucket underneath it. It will be interesting when they build something like that how many liters/day it can extract from ambient air and under what conditions.
Devices like that would be essential during 'wet bulb' days where the temperature and water content of the air created dangerous conditions for people. A passive device that takes no energy and just sucks water out of the air? Could be a lifesaver.
Devices like that would be essential during 'wet bulb' days where the temperature and water content of the air created dangerous conditions for people. A passive device that takes no energy and just sucks water out of the air? Could be a lifesaver.
To conduct the latent heat away, the aluminum sheet needs to be below the ambient temperature of the condenser plate.
You didn't read the paper did you :-). First, it isn't a "condenser" (which is kind of the cool science here) it is more of a molecular sieve that exploits two materials (one that repels, and one that attracts) the molecule in question (water). The water vapor is "forced[1]" together by the nano-structure, which result in a phase change (vapor to water) and that phase change releases heat into the nano-structure (and pushes the liquid water out to the surface) which makes the nano-structure warmer than the ambient temperature. The aluminum conducts that heat and is convectively radiating it into air on surfaces not covered with the nano-structure.
The researchers also noted that the water that was expressed to the surface of the material did not evaporate (as one would expect). There some interesting speculation as to why that is. It wasn't clear whether or not the water would move across the nano-structure if it was affected by gravity (aka dripping) but I can imagine several ways to transport it off the surface so I'm sure the researchers can too.
[1] The description in the paper is that capillary action forces the vapor into the interior of the structure where it collapses into liquid.
The researchers also noted that the water that was expressed to the surface of the material did not evaporate (as one would expect). There some interesting speculation as to why that is. It wasn't clear whether or not the water would move across the nano-structure if it was affected by gravity (aka dripping) but I can imagine several ways to transport it off the surface so I'm sure the researchers can too.
[1] The description in the paper is that capillary action forces the vapor into the interior of the structure where it collapses into liquid.
I read it. It sounds like nonsense.
This is basic thermodynamics, you can do however much hydrophobic/hydrophilic nanomaterials, but you won't get condensation unless you somehow conduct away the latent heat. This can be done by storing energy in the material itself (that's how desiccants work), or by providing a temperature gradient (a cooler).
This is basic thermodynamics, you can do however much hydrophobic/hydrophilic nanomaterials, but you won't get condensation unless you somehow conduct away the latent heat. This can be done by storing energy in the material itself (that's how desiccants work), or by providing a temperature gradient (a cooler).
Okay I think we're saying the same thing, but let me check that..
> This can be done by storing energy in the material itself (that's how desiccants work)
This is exactly where the energy goes. From the paper (in it's Materials and Methods section) -- All measurements were performed at 20° ± 0.2°C maintained by an air circulation system unless otherwise noted. The temperature of the films was controlled using a heating/cooling unit (THMS350V, Linkam Scientific Instruments, Salfords, UK) when necessary.
So the hypothesis is that the heat in the water vapor goes into the nano-pore material, which in their experiment they were actively maintaining at 20 degrees C. So yes, they are actively removing the heat created by the phase change.
One difference with desiccants is that once they are saturated you have to restore them through heating them up, but this stuff doesn't have that property. And while it may sound like nonsense it was reproduced in another lab[1].
Apparently capillary condensation is a thing, its the popping out of the liquid water that was unexpected.
[1] With a material that could potentially defy the laws of physics on their hands, Lee and Patel sent their design off to a collaborator to see if their results were replicable.
> This can be done by storing energy in the material itself (that's how desiccants work)
This is exactly where the energy goes. From the paper (in it's Materials and Methods section) -- All measurements were performed at 20° ± 0.2°C maintained by an air circulation system unless otherwise noted. The temperature of the films was controlled using a heating/cooling unit (THMS350V, Linkam Scientific Instruments, Salfords, UK) when necessary.
So the hypothesis is that the heat in the water vapor goes into the nano-pore material, which in their experiment they were actively maintaining at 20 degrees C. So yes, they are actively removing the heat created by the phase change.
One difference with desiccants is that once they are saturated you have to restore them through heating them up, but this stuff doesn't have that property. And while it may sound like nonsense it was reproduced in another lab[1].
Apparently capillary condensation is a thing, its the popping out of the liquid water that was unexpected.
[1] With a material that could potentially defy the laws of physics on their hands, Lee and Patel sent their design off to a collaborator to see if their results were replicable.
>>>> consider a 'cube' of fins of this stuff sitting in shade with a collection bucket underneath it.
There is no cube. The droplet's are attached strongly to the surface.
If the droplets drop to a cube, you can replace the cube with a cotton mat and let the water evaporate and get a low temperature mat. And then use the difference of temperature to generate electricity https://en.wikipedia.org/wiki/Thermoelectric_generator and turn on a lamp. And now you are breaking the second law of thermodynamics.
Consider a typical unplugged dehumidifier with Calcium Chloride. It generates water that drops to a cube, but it's salt water that evaporates less than fresh water, so you can't do the trick.
If you use silica gel, the water is trapped inside the material, so there is no cube.
With this new material the droplets are on the surface, but they refuse to fall down.
With an AC you get a cube full fresh water, but it obviously work only while plugged, so there is no magic.
> And while it may sound like nonsense it was reproduced in another lab [1].
They reproduced the visible droplets in the surface of the material. In neither lab they had a cube filing process. The sentence you quoted in [1] is very misleading.
There is no cube. The droplet's are attached strongly to the surface.
If the droplets drop to a cube, you can replace the cube with a cotton mat and let the water evaporate and get a low temperature mat. And then use the difference of temperature to generate electricity https://en.wikipedia.org/wiki/Thermoelectric_generator and turn on a lamp. And now you are breaking the second law of thermodynamics.
Consider a typical unplugged dehumidifier with Calcium Chloride. It generates water that drops to a cube, but it's salt water that evaporates less than fresh water, so you can't do the trick.
If you use silica gel, the water is trapped inside the material, so there is no cube.
With this new material the droplets are on the surface, but they refuse to fall down.
With an AC you get a cube full fresh water, but it obviously work only while plugged, so there is no magic.
> And while it may sound like nonsense it was reproduced in another lab [1].
They reproduced the visible droplets in the surface of the material. In neither lab they had a cube filing process. The sentence you quoted in [1] is very misleading.
Okay, I see where we diverge. The 'cube' was something I was thinking about not in the paper. I'll see if I can describe what I was thinking and you can tell me it breaks the rules :-).
You coat a piece of aluminum with nano-pore material and hang it vertically. Air flows over it and droplets appear on its surface (based on the paper). You also hang a frame of vertical wires (unenergized just small diameter wires, kind of like a screen but without the horizontal members) in front of the sheet by 1/2 the droplet's diameter. The wires don't touch the surface, they are suspended 1/2 droplet away.
Now when a droplet forms, it grows and intersects the wire (which is not hydrophobic) Surface tension puts the droplet around the wire and it slides down to the bottom of the wire frame, impacting any other droplets that had formed below it.
The resulting liquid water drops off the bottom of the wire frame into a catch pan below.
If one of these assemblies generates net water production from RH 70% air then an array of then would generate more water.
What am I missing?
You coat a piece of aluminum with nano-pore material and hang it vertically. Air flows over it and droplets appear on its surface (based on the paper). You also hang a frame of vertical wires (unenergized just small diameter wires, kind of like a screen but without the horizontal members) in front of the sheet by 1/2 the droplet's diameter. The wires don't touch the surface, they are suspended 1/2 droplet away.
Now when a droplet forms, it grows and intersects the wire (which is not hydrophobic) Surface tension puts the droplet around the wire and it slides down to the bottom of the wire frame, impacting any other droplets that had formed below it.
The resulting liquid water drops off the bottom of the wire frame into a catch pan below.
If one of these assemblies generates net water production from RH 70% air then an array of then would generate more water.
What am I missing?
The second law of thermodynamics. It's now trivially easy to create a free energy:
1. Have the drops fall on some surface and let them evaporate. This can happen because the relative humidity is below 100%.
2. This surface will get cooled by the evaporation.
3. Now use that temperature gradient to get free energy!
1. Have the drops fall on some surface and let them evaporate. This can happen because the relative humidity is below 100%.
2. This surface will get cooled by the evaporation.
3. Now use that temperature gradient to get free energy!
Does hydroelectric power violate the second law of thermodynamics in your opinion? I mean
1. Drops fall from the sky
2. They collect and flow down a river
3. We use that river to generate hydroelectric power to get free energy!
Water vapor, in air, has both thermal and potential energy that under the right conditions can be converted into a more useful form. We agree on that yes?
1. Drops fall from the sky
2. They collect and flow down a river
3. We use that river to generate hydroelectric power to get free energy!
Water vapor, in air, has both thermal and potential energy that under the right conditions can be converted into a more useful form. We agree on that yes?
No, we don't.
In case of hydroelectric power, there's a temperature gradient, driven by the Sun. Water evaporates in higher temperatures, radiates the heat into space, and falls out as rain.
In case of hydroelectric power, there's a temperature gradient, driven by the Sun. Water evaporates in higher temperatures, radiates the heat into space, and falls out as rain.
This:
"Water evaporates in higher temperatures, radiates the heat into space, and falls out as rain."
The paper says, "Water vapor in the nano-pores radiates its heat into the material and comes out to the surface as liquid water."
So you don't believe that the researchers experiment did what they say it did?
That's fine, typically in science you go and see if you can reproduce it.
So you don't believe that the researchers correctly described what was going on when it did what it did?
That's fine, typically in science you go and propose a way to falsify their hypothesis and test that.
My point was simply, if the researchers were presumptively accurate in their understanding (that's the principle of giving them the benefit of the doubt), then it would imply their material would pull liquid water out of the air below the temperature and conditions in which it would normally precipitate out.
They go to some length in their exposition to describe how they think it does that and where the energy comes from and where it goes. But if you don't believe them, then sure.
"Water evaporates in higher temperatures, radiates the heat into space, and falls out as rain."
The paper says, "Water vapor in the nano-pores radiates its heat into the material and comes out to the surface as liquid water."
So you don't believe that the researchers experiment did what they say it did?
That's fine, typically in science you go and see if you can reproduce it.
So you don't believe that the researchers correctly described what was going on when it did what it did?
That's fine, typically in science you go and propose a way to falsify their hypothesis and test that.
My point was simply, if the researchers were presumptively accurate in their understanding (that's the principle of giving them the benefit of the doubt), then it would imply their material would pull liquid water out of the air below the temperature and conditions in which it would normally precipitate out.
They go to some length in their exposition to describe how they think it does that and where the energy comes from and where it goes. But if you don't believe them, then sure.
I agree, but let's try to explain the microdetails of the scenario.
The new material is very hydrophilic, so the water prefer to be attached to it than been vapor.
If the wire is even more hydrophilic then the droplets will jump and collect around the wires, but they will be so attached that they will not fall down from the lower extreme of the wires.
If the wires are not so hydrophilic, the water will prefer to keep attached to the surface, or even the droplets will be smaller to avoid the wires and the collection will stop earlier.
Tweaking smartly the hydrophilic values and separations between the wires and the separation with the surface you may get interesting capillarity effect, but the water will be trapped again.
Anyway, it's difficult to look at all the details, but at the end of the day "The second law of thermodynamics. It's now trivially easy to create a free energy:"
The new material is very hydrophilic, so the water prefer to be attached to it than been vapor.
If the wire is even more hydrophilic then the droplets will jump and collect around the wires, but they will be so attached that they will not fall down from the lower extreme of the wires.
If the wires are not so hydrophilic, the water will prefer to keep attached to the surface, or even the droplets will be smaller to avoid the wires and the collection will stop earlier.
Tweaking smartly the hydrophilic values and separations between the wires and the separation with the surface you may get interesting capillarity effect, but the water will be trapped again.
Anyway, it's difficult to look at all the details, but at the end of the day "The second law of thermodynamics. It's now trivially easy to create a free energy:"
To add to this, there is a well-known "free energy" device design: have wicks moving water from a lower reservoir to a higher reservoir. Then use it to drive a water wheel.
It sounds good on paper because everybody knows that water can travel up a wick. But of course, if the end of the wick in the upper reservoir is submerged in the water, then water will just as happily travel _down_ the wick. And if the end of the wick is in free air, then water will not drip from it because the same capillary forces prevent it.
It sounds good on paper because everybody knows that water can travel up a wick. But of course, if the end of the wick in the upper reservoir is submerged in the water, then water will just as happily travel _down_ the wick. And if the end of the wick is in free air, then water will not drip from it because the same capillary forces prevent it.
You could coat them with an ultraemissive material and point them at the sky, if its not cloudy it will get significantly below the ambient air temp.
But the paper suggest that it will condense at ambient anyways, because it gets warmer so radiation to ambient is enough for it to work.
But the paper suggest that it will condense at ambient anyways, because it gets warmer so radiation to ambient is enough for it to work.
Looking at the paper, it seems like they put some silicon-dioxide nanoparticles on a substrate, then add a plastic (poly-ethylene) layer on top and melt it (annealing). The spaces between the nanoparticles gets partially filled with plastic. The ratio of plastic to particles is the poly-ethylene volume fraction (ϕPE). They tested different fractions and found that a certain range caused the wetting behavior.
Their experiments suggest that tiny water droplets appear inside the material at 70% RH (relative humidity). If this is true, then I expect there is a way to extract the droplets using very little energy. Ideas:
- make open collection points on the film
- use ultrasound to bounce the droplets around and consolidate them
- make the film on a material that can be saturated with water so the new droplets can easily join the flow
https://en.wikipedia.org/wiki/Volume_fraction
Their experiments suggest that tiny water droplets appear inside the material at 70% RH (relative humidity). If this is true, then I expect there is a way to extract the droplets using very little energy. Ideas:
- make open collection points on the film
- use ultrasound to bounce the droplets around and consolidate them
- make the film on a material that can be saturated with water so the new droplets can easily join the flow
https://en.wikipedia.org/wiki/Volume_fraction
> So the latent heat is conducted away by the cooling apparatus, it's just not explicitly stated, to sound more sensational.
In theory, if that makes it hotter than ambient air in the process, that would be a good thing - usually we have to cool things down below ambient air to get moisture out.
Not a good thing if you want to measure maximum moisture extraction, but cooling something to ambient temperatures is a much easier task.
In theory, if that makes it hotter than ambient air in the process, that would be a good thing - usually we have to cool things down below ambient air to get moisture out.
Not a good thing if you want to measure maximum moisture extraction, but cooling something to ambient temperatures is a much easier task.
[deleted]
This point is essential though! As soon as I saw the headline I knew it couldn't be the full story (there's no free osmotic lunch).
Is there a corollary to Betteridge's Law that says that popular science journalism will always overatate the result?
Is there a corollary to Betteridge's Law that says that popular science journalism will always overatate the result?
Would this not invalidate the conclusions of the paper? considering they are not just claiming to form water droplets, but that they do so isothermally.
It could still be a useful material, but the science would be bad.
It could still be a useful material, but the science would be bad.
Unless they have buried some really important caveat somewhere in the paper [1], it really looks like they are making claims that are incompatible with the second law of thermodynamics. They claim that water droplets are condensing on their nanomaterial at constant temperature and less than 100% relative humidity. This is absolutely forbidden by thermodynamics as we understand it. Under these conditions droplets can condense within pores (forming a concave surface), but they can never form a convex droplet on a flat surface.
Their mumbo-jumbo about water being "squeezed out" onto the surface by the hydrophobic component is totally bogus as well. The condensation will just stop earlier, without overflowing. Water condensing in concave pores and being squeezed into convex droplets requires hydrostatic pressure to be positive and negative at the same time.
The possibilities I see are: 1) contaminated surfaces 2) miscalibrated relative humidity or 3) they've neglected to mention a cooling plate that keeps the material below ambient.
1. https://www.science.org/doi/10.1126/sciadv.adu8349
Their mumbo-jumbo about water being "squeezed out" onto the surface by the hydrophobic component is totally bogus as well. The condensation will just stop earlier, without overflowing. Water condensing in concave pores and being squeezed into convex droplets requires hydrostatic pressure to be positive and negative at the same time.
The possibilities I see are: 1) contaminated surfaces 2) miscalibrated relative humidity or 3) they've neglected to mention a cooling plate that keeps the material below ambient.
1. https://www.science.org/doi/10.1126/sciadv.adu8349
I'm not sure what's forbidden here. You don't need 100% relative humidity to grab water from the air in fact in any wood has a moisture content that in equilibrium is in relation to the air moisture content. The moisture diffuses into every material and evaporates based on where it finds less vapor pressure. That's why you may have dry lips at 40% RH versus moisturized lips at 70% RH.
What you're referring to is condensation and is caused by air oversaturation due to a temperature drop which doesn't seem to be the case here.
Theoretically speaking, you can have a material that somehow absorbs high moisture from the air but has microscale properties that promote creation of droplets then somehow these droplets are separated from the rest of the air (with something like a smart vapor retarder, a passive material) and the water gets harvested.
What you're referring to is condensation and is caused by air oversaturation due to a temperature drop which doesn't seem to be the case here.
Theoretically speaking, you can have a material that somehow absorbs high moisture from the air but has microscale properties that promote creation of droplets then somehow these droplets are separated from the rest of the air (with something like a smart vapor retarder, a passive material) and the water gets harvested.
What you are referring to is called capillary condensation [1]. When you have a hydrophilic surface with thin capillaries or small pores, they can pull water from the air below 100% RH. However, this process requires an enclosed space with a very small radius and the air-water interface is always concave in this case (it's just how capillary forces work).
Forming a convex surface, on the other hand, requires an at least slightly hydrophobic material and produces a positive internal pressure. This is a key difference, because condensation into a hydrophilic pore is favorable in terms of free energy, while condensing onto a hydrophobic surface is unfavorable (unless you have a supersaturated vapor).
> Theoretically speaking, you can have a material that somehow absorbs high moisture from the air but has microscale properties that promote creation of droplets then somehow these droplets are separated from the rest of the air
That "somehow" is what makes the paper's claims impossible. The water condenses spontaneously into the pore because it thereby lowers its free energy. Extruding it onto the surface is then even more unfavorable than direct condensation. Unfortunately, no passive system can achieve this feat, no matter how cleverly nanostructured, as it would go against the arrow of increasing entropy. You need an external energy source to drive that process.
1. https://en.wikipedia.org/wiki/Capillary_condensation
Forming a convex surface, on the other hand, requires an at least slightly hydrophobic material and produces a positive internal pressure. This is a key difference, because condensation into a hydrophilic pore is favorable in terms of free energy, while condensing onto a hydrophobic surface is unfavorable (unless you have a supersaturated vapor).
> Theoretically speaking, you can have a material that somehow absorbs high moisture from the air but has microscale properties that promote creation of droplets then somehow these droplets are separated from the rest of the air
That "somehow" is what makes the paper's claims impossible. The water condenses spontaneously into the pore because it thereby lowers its free energy. Extruding it onto the surface is then even more unfavorable than direct condensation. Unfortunately, no passive system can achieve this feat, no matter how cleverly nanostructured, as it would go against the arrow of increasing entropy. You need an external energy source to drive that process.
1. https://en.wikipedia.org/wiki/Capillary_condensation
Thank you, this is a very clear explanation for me.
It filled the critical gaps in my intuition that I didn't have the brain cycles to formulate hypotheses against.
It filled the critical gaps in my intuition that I didn't have the brain cycles to formulate hypotheses against.
The reverse problem is also true with such materials:
Water harvesting in pristine lab conditions may break down rapidly in realistic scenarios. Something that’s wet attracts dust and microbes. Dust plus water means more microbes. You’ll have lichen growing on this stuff in no time.
Water harvesting in pristine lab conditions may break down rapidly in realistic scenarios. Something that’s wet attracts dust and microbes. Dust plus water means more microbes. You’ll have lichen growing on this stuff in no time.
Also wouldn't be the first time an experiment overlooked a small temperature gradient or calibration issue
Did you read the article? They're not droplets on a flat surface. They're droplets being held by surface tension to water inside pores.
Repost from four days ago: https://news.ycombinator.com/item?id=44060712
Also, they do a really good job of making it sound like it violates thermodynamics. Since it doesn't, and dehumidifiers already do a good job of getting water out of air for the energy price you have to pay, there has to be some other selling point. Right? But I'm not sure I see it.
Also, they do a really good job of making it sound like it violates thermodynamics. Since it doesn't, and dehumidifiers already do a good job of getting water out of air for the energy price you have to pay, there has to be some other selling point. Right? But I'm not sure I see it.
> dehumidifiers already do a good job of getting water out of air for the energy price you have to pay
They do a terrible job. Condensate dehumidifiers are as expensive to run as an AC, produce unwanted heat, and are noisy. Dessicant dehumidifiers are even less energy-efficient.
If there's a way to extract moisture from the air with less energy and less noise, that would be huge.
They do a terrible job. Condensate dehumidifiers are as expensive to run as an AC, produce unwanted heat, and are noisy. Dessicant dehumidifiers are even less energy-efficient.
If there's a way to extract moisture from the air with less energy and less noise, that would be huge.
Less energy would definitely be a huge plus but unless this violates our understanding of thermodynamics there will still be unwanted heat put out into the air. The heat from a dehumidifier comes primarily from the latent heat in the water being released so that the water can become liquid. This heat must be released somehow in this process unless they actually did find something that breaks our understanding of physics.
Obligatory Technology Connections video on the topic: https://www.youtube.com/watch?v=j_QfX0SYCE8
Obligatory Technology Connections video on the topic: https://www.youtube.com/watch?v=j_QfX0SYCE8
That's true, but I was under the impression that most of the heat generated by current compressor dehumidifiers is just waste heat from the mechanical operation of the compressor itself. The phase change heat is there too, but it's significantly less. So there should still be a lot of room for improvement, theoretically.
Yeah, there's certainly some of that, but going off of Alec's numbers and trial above you end up with a larger portion coming from the latent heat than from the mechanism, for the same reason that a heat pump is more efficient than an electric heater: it's condensing more water than it is running mechanisms.
That said, his demo is not under typical operating conditions in that a dehumidifier is normally expected to actually be able to catch up and reduce humidity in the room, while his demo ensures that the humidity levels stay high throughout the hour. So it's likely that under normal operating conditions the mechanism's proportion of the waste heat is higher than it is in his demo.
That said, his demo is not under typical operating conditions in that a dehumidifier is normally expected to actually be able to catch up and reduce humidity in the room, while his demo ensures that the humidity levels stay high throughout the hour. So it's likely that under normal operating conditions the mechanism's proportion of the waste heat is higher than it is in his demo.
> That's true, but I was under the impression that most of the heat generated by current compressor dehumidifiers is just waste heat from the mechanical operation of the compressor itself.
Nope. It's almost all (>80%) latent heat. I believe, the theoretical limit is around 90% for typical room temperatures.
Nope. It's almost all (>80%) latent heat. I believe, the theoretical limit is around 90% for typical room temperatures.
typical room temperatures is doing a lot of work there.
>The heat from a dehumidifier comes primarily from the latent heat in the water being released so that the water can become liquid.
A dehumidifier movies heat from one side to another using electricity to do the work. One side gets cold so the water can condense on it, while the other side gets hot from extracting the heat from the cold side. Heat is still generated from this process even if there are 0 water molecules in the air and no water is collected. The water does not create the heat, the electricity does.
I don't think there has to be any heat involved with collecting water molecules in the air into a larger volume of water, depending on the process used.
A dehumidifier movies heat from one side to another using electricity to do the work. One side gets cold so the water can condense on it, while the other side gets hot from extracting the heat from the cold side. Heat is still generated from this process even if there are 0 water molecules in the air and no water is collected. The water does not create the heat, the electricity does.
I don't think there has to be any heat involved with collecting water molecules in the air into a larger volume of water, depending on the process used.
> I don't think there has to be any heat involved with collecting water molecules in the air into a larger volume of water, depending on the process used.
For the water to condense, there must be heat given off, unless I’m fundamentally misremembering my high school physics class.
For the water to condense, there must be heat given off, unless I’m fundamentally misremembering my high school physics class.
state change takes 63 calories per cubic centimeter of H2O
unless I am misremembering my high school science class.
at least for water solid to liquid
at least for water solid to liquid
Both processes create/release heat, and in Alec's tests in the linked video the bulk of the heat from the dehumidifier running in a humid space is coming from latent heat released from the water. That may not be true in regular operating conditions, but there will always be a substantial amount of heat released from the water when you trigger a phase shift.
> I don't think there has to be any heat involved with collecting water molecules in the air into a larger volume of water, depending on the process used.
The only other option is to increase the pressure in the room or in a space within the room, which this material pretty clearly isn't doing.
> I don't think there has to be any heat involved with collecting water molecules in the air into a larger volume of water, depending on the process used.
The only other option is to increase the pressure in the room or in a space within the room, which this material pretty clearly isn't doing.
It’s not just the electricity creating the perceived heat
https://en.wikipedia.org/wiki/Enthalpy_of_vaporization
If water changes phase from a gas to a liquid, it releases a large amount of energy (enough heat to heat five times as much water from 0 to 100°C). That's likely far more heat than the electricity generates - though, of course, the heat released by electricity is very real as well, and as you say will even happen if the air is completely dry.
Possibly this doesn't happen if the condensation happens in a capillary (there is some funkyness related to energy levels), but then it must stay trapped there.
Possibly this doesn't happen if the condensation happens in a capillary (there is some funkyness related to energy levels), but then it must stay trapped there.
[deleted]
> If there's a way to extract moisture from the air with less energy and less noise, that would be huge.
Less noise: I agree, but you still need some air flow so the corners of the room that are far away also get dehumidified. Perhaps a slow fan in enough, and when you run them slowly they are quieter.
Less energy: It's not clear that this uses less total energy. It's easier to imagine what is happening if you compare it to a high tech Dehumidifier Bag. https://www.amazon.com/Wisesorb-Moisture-Eliminator-Fragranc... But instead of sending the drops down, they get attached to the device. You can use it only once unplugged. Then you have to buy a new one or use energy to extract the water (like boiling the water of the dehumidifier bad until you get the crystals again). It's not clear if building a new copy of this is cheaper than building some new calcium chloride salts, and/or if regenerating the new device is cheaper than regenerating the calcium chloride salts (that is usually not done).
Less noise: I agree, but you still need some air flow so the corners of the room that are far away also get dehumidified. Perhaps a slow fan in enough, and when you run them slowly they are quieter.
Less energy: It's not clear that this uses less total energy. It's easier to imagine what is happening if you compare it to a high tech Dehumidifier Bag. https://www.amazon.com/Wisesorb-Moisture-Eliminator-Fragranc... But instead of sending the drops down, they get attached to the device. You can use it only once unplugged. Then you have to buy a new one or use energy to extract the water (like boiling the water of the dehumidifier bad until you get the crystals again). It's not clear if building a new copy of this is cheaper than building some new calcium chloride salts, and/or if regenerating the new device is cheaper than regenerating the calcium chloride salts (that is usually not done).
So, is this new method less noisy and/or more energy efficient? The article doesn't really say.
>without the need for any external energy.
That sure seems to imply that there's no need for a noisy and power hungry compressor.
That sure seems to imply that there's no need for a noisy and power hungry compressor.
It also seems to imply that it violates thermodynamics.
It takes energy to condense water, so where does it get it? If it isn't external, it runs out.
It takes energy to condense water, so where does it get it? If it isn't external, it runs out.
Condensation of water is exothermic. If you add a cold thing to the environment, ie, remove heat from the water, the water will condense all on its own. This reaches steady-state when the cold thing is warm and the water is condensed. No thermodynamics issue!
They’re claiming they have a material that will do it at higher temperatures. Assuming such a material gets hotter as it works, there’s no thermodynamics problem here.
They’re claiming they have a material that will do it at higher temperatures. Assuming such a material gets hotter as it works, there’s no thermodynamics problem here.
> They’re claiming they have a material that will do it at higher temperatures. Assuming such a material gets hotter as it works, there’s no thermodynamics problem here.
That's ok, but the amount of water you get is fixed - the process can't continue. You install the device into your room, it condenses 1L of water as droplets on its surface (or, more likely 1ml of water), and it's now done, that's all the water it's going to remove/produce, if this is the right explanation. It would be perfectly equivalent to bringing in a cold slab of metal from your fridge into your room - it will condense some water as it gets hotter, and it will eventually get as warm as the room and stop condensing anymore water, forever.
Conversely, if the process were continuous (say, as long as you remove the condensed droplets, new droplets form), as they seem to claim, that would very likely violate thermodynamics again.
That's ok, but the amount of water you get is fixed - the process can't continue. You install the device into your room, it condenses 1L of water as droplets on its surface (or, more likely 1ml of water), and it's now done, that's all the water it's going to remove/produce, if this is the right explanation. It would be perfectly equivalent to bringing in a cold slab of metal from your fridge into your room - it will condense some water as it gets hotter, and it will eventually get as warm as the room and stop condensing anymore water, forever.
Conversely, if the process were continuous (say, as long as you remove the condensed droplets, new droplets form), as they seem to claim, that would very likely violate thermodynamics again.
What about entropy? The reason you need to power AC for example is that if you didn't you could reduce entropy and generate power for free, and basically reverse time.
The amount of entropy in a closed system is not allowed to decrease, but it is allowed to be constant. The amount of energy released by the phase shift is equal to the amount of energy absorbed by the object as heat.
Sure, but then the temperature of the object has to increase. And as its temperature increases, it has to stop condensing water - at the very least, once it reaches ~100C, it will instantly boil off any extra water that it condenses.
You are super confident a thing that exists can't exist
https://en.wikipedia.org/wiki/Air_well_(condenser)
Check out the passive section of the above
https://en.wikipedia.org/wiki/Air_well_(condenser)
Check out the passive section of the above
Those depend on energy differentials so the sun is the external heat source.
Especially for somewhere like UAE that in summer has the upsetting combination of massive humidity, no rain, and huge water demand.
Someone here once posted a link to a story[0] about the Persian Cooling Towers, that you see all over the ME.
Thousands of years old, I think.
[0] https://www.bbc.com/future/article/20210810-the-ancient-pers...
Thousands of years old, I think.
[0] https://www.bbc.com/future/article/20210810-the-ancient-pers...
Perhaps OP was describing "swamp coolers" — or evaporative cooling?
That's the exact opposite of extracting moisture from the air.
You're right. I'll leave my original comment because I'm an idiot, ha ha.
Running a swamp cooler + dehumidifier that doesn't heat up would mean being able to do self contained cooling which would be a massive thing. Currently the only way to do that is with desiccant which needs recharging too often to be practical.
Tech Ingredients demonstrates how this works: "Revolutionary Air Conditioner!"
https://youtu.be/R_g4nT4a28U?si=MoRSi1mOyHiVbZUr
https://youtu.be/R_g4nT4a28U?si=MoRSi1mOyHiVbZUr
> If there's a way to extract moisture from the air with less energy and less noise, that would be huge.
I vote we write to our legislators to update the laws of thermodynamics to enable this. Typically I would agree we should leave well enough alone, but in this case it seems like the benefits outweigh the costs.
I vote we write to our legislators to update the laws of thermodynamics to enable this. Typically I would agree we should leave well enough alone, but in this case it seems like the benefits outweigh the costs.
That's not how the laws of thermodynamics work.
In reality, you would need to convene an international consortium to approve to the change, and the Chinese wouldn't sign on unless we agree to a temporary suspension of Newton's third law.
In reality, you would need to convene an international consortium to approve to the change, and the Chinese wouldn't sign on unless we agree to a temporary suspension of Newton's third law.
We would only need a committee's approval if changing it would break things.
I say we skip that process, test it in a lab somewhere in rural midwest where nobody lives, and see if gravity starts changing or whatever. As long as cows don't start to float in a 3 mile radius within 4-5 hours, that's probably good enough validation to move forward with changing thermodynamic legislation.
[edit] we should also probably make sure the boiling point of water stays the same
I say we skip that process, test it in a lab somewhere in rural midwest where nobody lives, and see if gravity starts changing or whatever. As long as cows don't start to float in a 3 mile radius within 4-5 hours, that's probably good enough validation to move forward with changing thermodynamic legislation.
[edit] we should also probably make sure the boiling point of water stays the same
Just run it in Australia, we already overturned mathematics.
I’m not sure the constitution grants Congress that power.
They already weighted in on the definition of π so why not?
https://en.wikipedia.org/wiki/Indiana_pi_bill
https://en.wikipedia.org/wiki/Indiana_pi_bill
It almost certainly doesn't violate our understanding of thermodynamics, but it's not clear that it would have to in order to condense ambient water vapor from the atmosphere.
From the paper [1]:
Remarkably, when these amphiphilic nanoporous PINFs are exposed to high yet subsaturating conditions [i.e., relative humidity (RH) < 100%], macroscopic water droplets appear spontaneously on the film surfaces without the need for cooling, as illustrated in Fig. 1C and shown in Fig. 1D.
1 - https://www.science.org/doi/10.1126/sciadv.adu8349
From the paper [1]:
Remarkably, when these amphiphilic nanoporous PINFs are exposed to high yet subsaturating conditions [i.e., relative humidity (RH) < 100%], macroscopic water droplets appear spontaneously on the film surfaces without the need for cooling, as illustrated in Fig. 1C and shown in Fig. 1D.
1 - https://www.science.org/doi/10.1126/sciadv.adu8349
Well, when water changes from vapor to liquid, it releases heat. The heat has to go somewhere.
Sorry, I don't know the correct physics lingo. Heat of enthalpy or formation or whatever.
Sorry, I don't know the correct physics lingo. Heat of enthalpy or formation or whatever.
Tangent but this may solve a mystery of mine. When I make scrambled eggs I add a little bit of water to make them fluffy. When I turn off the heat there’s a puff of steam I can’t explain. Since it seems to me more heat is needed to produce that extra puff of steam. However, maybe the fast condensing of the water vapor that happens when I turn off the stove produces a. I start of extra heat and therefore the steam?
Is it gas stovetop?
If so, it could be that the water vapor coming from the eggs no longer mixing with the hot gases coming from the flame around the pan, allowing it to drop below the dew temp (?) and allowing it to condense right above the pan. IOW the water vapor is always there, you just can't see it until it is able to condense in lower ambient temps.
If so, it could be that the water vapor coming from the eggs no longer mixing with the hot gases coming from the flame around the pan, allowing it to drop below the dew temp (?) and allowing it to condense right above the pan. IOW the water vapor is always there, you just can't see it until it is able to condense in lower ambient temps.
I don't think the fast condensing of steam would cause enough heat to cause more steam, though. Because the reason it condenses fast is because there's heat being removed from the system (cooling to the room, and no longer more heat getting added). So the heat is already "spoken for" - it's the reason that steam turned back into water.
The other commenter that wonders if it's a gas stove might be onto something.
The other commenter that wonders if it's a gas stove might be onto something.
Maybe the drop in temp stops a Leidenfrost effect that was reducing the surface area of the food that was contacting the pan.
Sure, but it could get absorbed/radiated away in the base material.
If water vapor is condensing on the material, wouldn't there be a transfer of heat energy?
Heat transfer is not transfer of heat energy
The idea here is that you don't need to cool down the air to get water.
First you get water, and as a result material heats up a little bit, then it can cool down passively back to ambient.
First you get water, and as a result material heats up a little bit, then it can cool down passively back to ambient.
> there has to be some other selling point. Right? But I'm not sure I see it.
Windtraps [0].
[0]: https://dune.fandom.com/wiki/Windtrap
Windtraps [0].
[0]: https://dune.fandom.com/wiki/Windtrap
or moisture vaporators
https://starwars.fandom.com/wiki/Moisture_vaporator
https://starwars.fandom.com/wiki/Moisture_vaporator
But moisture farming? Really? A man of your talents?
Those exist, but, as the GP points out, they're called "dehumidifiers". Or sometimes clothes driers. The question was, what makes this new dehumidifier any better than existing dehumidifiers.
Windtraps are passive, like this material. They work solely on temperature differential and wind.
I'm not aware of any passive, solid state dehumidifiers which are not chemical, which condense water to a chemically loaded solution, which what a Windtrap is not.
I'm not aware of any passive, solid state dehumidifiers which are not chemical, which condense water to a chemically loaded solution, which what a Windtrap is not.
There is no way to make a passive, solid-state humidifier that doesn't involve some chemical reaction with water. Thermodynamics dictates that precipitating water from a non-saturated atmosphere must generate large amounts of heat (assuming pressure doesn't change) and so can't be a self-sustaining process.
So, even though it may not be 100% clear how from their description, their device is nothing but a novel way of making a dehumidifier that needs some kind of active component - perhaps the AC that is keeping the temperature steady in their experiment (since water condensation generates large amounts of heat, it's likely that, without the AC, temperature would rise and their water droplets would evaporate right back).
So, even though it may not be 100% clear how from their description, their device is nothing but a novel way of making a dehumidifier that needs some kind of active component - perhaps the AC that is keeping the temperature steady in their experiment (since water condensation generates large amounts of heat, it's likely that, without the AC, temperature would rise and their water droplets would evaporate right back).
> There is no way.
No, there's a way without running afoul of thermodynamics. You need to bleed the heat to a cooler surface efficiently, and you can do it without any external power.
You can use heat pipes to effectively wick away heat to a heat sink, like the Earth itself. Similar systems exists for cooling and heating, which uses buried pipes to extract or dump heat to the Earth's crust. You can sink the heat similarly without any external power (sans wind to push air through the material).
In the Windtrap example, the other side of the opening is a deep well basically. Cooler than outside world. The rocks sink the heat probably, too. Sı it's possible to create self-sustaining process without external electricity. Yes, an heat-pipe is not solid-state per se, but it's insulated and works on the principle of heat difference only.
> their device is nothing but a novel way of making a dehumidifier that needs some kind of active component...
No, their paper say that they forced air through it and it worked on a temperature differential. Maybe a compressor or Peltier device can acclerate the process, sure, but sinking the heat to the earth and blowing air through it will work equally well.
Have a friend who designs heat-pipes for space applications. That things are way faster than we see on computer applications, but equally more expensive.
No, there's a way without running afoul of thermodynamics. You need to bleed the heat to a cooler surface efficiently, and you can do it without any external power.
You can use heat pipes to effectively wick away heat to a heat sink, like the Earth itself. Similar systems exists for cooling and heating, which uses buried pipes to extract or dump heat to the Earth's crust. You can sink the heat similarly without any external power (sans wind to push air through the material).
In the Windtrap example, the other side of the opening is a deep well basically. Cooler than outside world. The rocks sink the heat probably, too. Sı it's possible to create self-sustaining process without external electricity. Yes, an heat-pipe is not solid-state per se, but it's insulated and works on the principle of heat difference only.
> their device is nothing but a novel way of making a dehumidifier that needs some kind of active component...
No, their paper say that they forced air through it and it worked on a temperature differential. Maybe a compressor or Peltier device can acclerate the process, sure, but sinking the heat to the earth and blowing air through it will work equally well.
Have a friend who designs heat-pipes for space applications. That things are way faster than we see on computer applications, but equally more expensive.
None of this matches the setup the paper describes, though of course you are right that bleeding heat into the Earth is a time-tested and known to function way to build such systems.
From the article:
> Before they understood what was happening, the researchers first thought that water was simply condensing onto the surface of the material due to an artifact of their experimental setup, such as a temperature gradient in the lab. To rule that out, they increased the thickness of the material to see if the amount of water collected on the surface would change.
There's a temperature gradient in their lab setup. i.e. one side of the material is cooler than the other side. This is where I extrapolated that you can increase the performance of the material by bleeding the heat into the Earth.
> Before they understood what was happening, the researchers first thought that water was simply condensing onto the surface of the material due to an artifact of their experimental setup, such as a temperature gradient in the lab. To rule that out, they increased the thickness of the material to see if the amount of water collected on the surface would change.
There's a temperature gradient in their lab setup. i.e. one side of the material is cooler than the other side. This is where I extrapolated that you can increase the performance of the material by bleeding the heat into the Earth.
This would be passive and solid state.
Except we know that is impossible from simple thermodynamics, so there's no point in contemplating this "what if".
Have you done any work with this material?
No, but I don't need to work on a perpetual motion machine to know that it doesn't work.
My question would be do you have enough experience to know that it is a perpetual motion machine. I read the article and nothing sounds like perpetual motion to me. The atmosphere is always dynamic and my reading of the article was that it is using 2 different changes to harness these changes. Surface tension and atmospheric pressure seem to be the mechanisms.
I was trying to figure out if your comment was informed.
I was trying to figure out if your comment was informed.
> Repost from four days ago
Thanks! there were a few comments there and we'll merge them hither.
Thanks! there were a few comments there and we'll merge them hither.
I wish they hadn't used "physics-defying" in their press release because I'm certain this is an important discovery for water condensers, but claiming it doesn't need an external energy source is massively negligent.
I'm fairly certain they've created some form of a Brownian Ratchet: https://en.wikipedia.org/wiki/Brownian_ratchet
People love to claim there's no external energy source, but then when you look closely, you'll find a hot-cold differential, and then you need external energy to maintain that differential. I'd put a large sum of money that either the material is colder than the ambient environment or the incoming moisture is warmer than the ambient environment. It might even be a differential within their material, and the lab lights are warming one side! There's a lot of passive devices that rely on the hot-cold cycle of day and night, that still counts as energy input from the sun.
The article even mentions they tried to rule out a thermal gradient by increasing the thickness of the material, I'm not sure I understand why that would rule it out... the gradient would still exist.
I hate this, because if they aren't intentionally supplying energy, it's probably really efficient (assuming they aren't taking samples out of the freezer or something) so it's still a big deal and important but apparently we have to claim something is a perpetual motion machine to get attention among the public.
I'm fairly certain they've created some form of a Brownian Ratchet: https://en.wikipedia.org/wiki/Brownian_ratchet
People love to claim there's no external energy source, but then when you look closely, you'll find a hot-cold differential, and then you need external energy to maintain that differential. I'd put a large sum of money that either the material is colder than the ambient environment or the incoming moisture is warmer than the ambient environment. It might even be a differential within their material, and the lab lights are warming one side! There's a lot of passive devices that rely on the hot-cold cycle of day and night, that still counts as energy input from the sun.
The article even mentions they tried to rule out a thermal gradient by increasing the thickness of the material, I'm not sure I understand why that would rule it out... the gradient would still exist.
I hate this, because if they aren't intentionally supplying energy, it's probably really efficient (assuming they aren't taking samples out of the freezer or something) so it's still a big deal and important but apparently we have to claim something is a perpetual motion machine to get attention among the public.
Yeah I understand the need for an university to make the news once in a while, and the fact that this made the front page here proves the effectiveness of the method, but the terms "Passively Harvest" and "Defies Physics" should be used very carefully in the context of a scientific publication, even though it's only a blog post so we don't expect peer-reviewed journal levels of rigor.
I feel that it disserves science in the end, the belief that some magic material is going to break the second law of thermodynamics is closer to alchemy than chemistry.
I feel that it disserves science in the end, the belief that some magic material is going to break the second law of thermodynamics is closer to alchemy than chemistry.
PET is a decent insulator, and they seem to be trying to ensure it wasn’t the temperature difference causing condensation, but the nano structure itself. I’m assuming they were controlling temperature and humidity, so it would mean the material must get hotter, but that seems like it can also be passively solved with a radiator. What they are describing would be a pretty big deal and seems plausible.
This is pretty cool! Basically changes the thermodynamic delta required for a condensation-evaporation cycle from climatic mediation to material mediation.
What if you could eventually program the pore size? This would mean you could change the inflow/outflow balance of the reservoirs on-demand. Imagine smart clothing. Hot out -> increase pore size so the material dumps water, cold out -> pore size shrinks so the water is less likely to evaporate.
I am peeved by the "violates physics" verbiage in the article though.
What if you could eventually program the pore size? This would mean you could change the inflow/outflow balance of the reservoirs on-demand. Imagine smart clothing. Hot out -> increase pore size so the material dumps water, cold out -> pore size shrinks so the water is less likely to evaporate.
I am peeved by the "violates physics" verbiage in the article though.
See https://en.wikipedia.org/wiki/Air_well_(condenser) and https://en.wikipedia.org/wiki/Fog_collection and https://en.wikipedia.org/wiki/Atmospheric_water_generator
This apparently can collect vapor (not fog) in ambient temperature, although the material heats up a little bit while absorbing water and needs to cool back down, which should be fine since when warm it's warmer than ambient air.
All of those rely on condensation, which is caused by temperature getting low enough the air can’t hold water. The mechanism for the new material is completely different. It doesn’t appear to require the air to be saturated.
We already have substances that remove water from air. In those the water becomes absorbed. This seems to work on a similar principle. The real difference is the water doesn’t stay absorbed.
We already have substances that remove water from air. In those the water becomes absorbed. This seems to work on a similar principle. The real difference is the water doesn’t stay absorbed.
I'm so tempted to link this..
Like, not even ironically.
I know this isn't reddit and all, but, well..
https://en.wikipedia.org/wiki/Dune_(novel)
Like, not even ironically.
I know this isn't reddit and all, but, well..
https://en.wikipedia.org/wiki/Dune_(novel)
People need to understand that the minimum energy required to separate water from air is much higher than the minimum energy required to separate water from salt. This fact of physics means desalination will always be more efficient than water harvesting.
My understanding is that with desalination you now have the problem of all the brine (on top of needing a good amount of consumable material to do the desalination when looking at existing products).
Seems to me that if you have a device that requires no extra material consumable input that's pretty interesting? Plenty of places with access to electricity that could benefit from the lack of other material input in theory.
Seems to me that if you have a device that requires no extra material consumable input that's pretty interesting? Plenty of places with access to electricity that could benefit from the lack of other material input in theory.
Does that include transportation costs?
If you have power, you can harvest water from the air wherever you are. Desalination generally requires trucking the water from the ocean to you.
I don't have the slightest idea whether transportation costs can ever be large enough to make water harvesting more efficient?
If you have power, you can harvest water from the air wherever you are. Desalination generally requires trucking the water from the ocean to you.
I don't have the slightest idea whether transportation costs can ever be large enough to make water harvesting more efficient?
With respect to energy balance comments and comparing this to other technologies: both processes of absorption and condensation are happening within the same material passively, meaning you do not need to put energy into it. The heat gained from absorption is lost in the next step of condensation. The impact of this discovery, therefore, is that you don't need the power of your AC or your dehumidifier or your moisture vaporator on the south ridge.
Always testing the AI's I thought this might be a fun one to watch how they think through it since it is about technology that they would not have been trained on. Grok thought through the process more thoroughly than I (B.S.ChemE) would've .
https://grok.com/share/bGVnYWN5_e80e8100-3682-4157-879e-c5ca...
Always testing the AI's I thought this might be a fun one to watch how they think through it since it is about technology that they would not have been trained on. Grok thought through the process more thoroughly than I (B.S.ChemE) would've .
https://grok.com/share/bGVnYWN5_e80e8100-3682-4157-879e-c5ca...
Grok is wrong. The description violates the second law of thermodynamics. But I don't blame Grok, the PR is very misleading.
We did something similar to this in the middle of the Mojave with carbonate rock, charcoal, and a big corrugated metal tube.
It produces about 3 gallons of water a night.
34.997387, -116.380048
See the big tube sticking up? There's a miner's hotel built there.
It produces about 3 gallons of water a night.
34.997387, -116.380048
See the big tube sticking up? There's a miner's hotel built there.
Got a link to how this was made?
I do not, I'm sorry. Basically the bottom is charcoal for a filter, the top is porous carbonate rock to catch moisture from the air, and the large metal tube serves as a way to heat things up and then at night chill down below ambient a bit faster so that water condenses out of the rock and drips through the charcoal and through piping to a water collection system.
I think people are being too critical in the comments.. I see nothing requiring free energy or physics defying in an ideal condensation material. This process is going on all the time in less optimized materials and we usually are not happy about it. (There's also a very interesting logical argument that we only exist because the water molecule has such unusual properties compared to its environment.)
If this technology can be widely applied in water scarce areas, it would be incredibly meaningful. People in these regions would no longer have to worry about water shortages. It could truly change lives by providing access to clean water without relying on external resources, making a significant impact on communities that need it the most.
Mangle, looped band of material. Energy can be totally mechanical to move the loop through the mangle, or PV harvested electrical.
There's no free lunch, but removing water from a fabric matrix is a well understood process. Thats what washerwomen have done for millenia.
There's no free lunch, but removing water from a fabric matrix is a well understood process. Thats what washerwomen have done for millenia.
I hope this pans out. There are 1000s of applications:
Put one of these next to every tree. Or lines of them along rows of crops.
Run one in homes to make your ac more efficient and manage humidity.
Collect water on mountains or tall buildings and make hydro power?
Keep your pool topped off.
Put one of these next to every tree. Or lines of them along rows of crops.
Run one in homes to make your ac more efficient and manage humidity.
Collect water on mountains or tall buildings and make hydro power?
Keep your pool topped off.
I love that it's not just about absorption but this continuous cycle of condensation and release. That's what makes it potentially useful beyond niche cases.
This seems like it could be improved with ai-assisted molecular dynamics that have been in the news for drug discovery and protein folding.
Could this lead to a superior desalination method?
Basically Let salt water saturate the air in a closed system and use these to collect the water.
Basically Let salt water saturate the air in a closed system and use these to collect the water.
Now make this a marketable power-less air dehumidifier. This is one of those 'changing whole industries' things.
Those exist in the form of dehumidifier bags, and they're inexpensive and easy to get. Does this material have benefits over what's currently in use?
Dehumidifier bags are bulky. Surfaces, on the other side, can be folded into loops, which should increase the amount of humidity they can absorb.
Surfaces as you describe go into the bags.
Uses in AC and clothing seem like obvious use cases.
Removing water from the atmosphere on scale can only be devastating to global weather patterns. Sorry country B, you get no more rain because country A is harvesting all the water.
Never quit experimenting on something worthwhile, for one thing so you're always experimenting.
The best things may come by accident, which is where it sometimes just starts to get good.
But what are the difference in odds for someone who is constantly experimenting versus someone who experiments not at all?
Regardless of what you really set out to accomplish to begin with.
And which has the momentum to continue experimenting, even in the case of a major pivot?
Looks like they really have hit the sweet spot and it's a bit like creating molecular sieves which are tuned to release the collected moisture without excess energy.
Could also be harvesting a little ambient energy and working to "zone refine" the atmospheric fluid.
The best things may come by accident, which is where it sometimes just starts to get good.
But what are the difference in odds for someone who is constantly experimenting versus someone who experiments not at all?
Regardless of what you really set out to accomplish to begin with.
And which has the momentum to continue experimenting, even in the case of a major pivot?
Looks like they really have hit the sweet spot and it's a bit like creating molecular sieves which are tuned to release the collected moisture without excess energy.
Could also be harvesting a little ambient energy and working to "zone refine" the atmospheric fluid.
[deleted]
Is it just me or does extracting moisture from the air seem like a really bad idea?
I take it you do not live on the south or east coast of a northern hemisphere continent?
People there usually have a surplus of moisture in the air most of the time.
People there usually have a surplus of moisture in the air most of the time.
A surplus according to who? Those ecosystems exist for a reason. Are we talking about terraforming Earth? For what purpose?
this was certainly amazing to see (at least two years ago)
As a similar comment note, it's like a high tech Dehumidifier bag. https://www.amazon.com/Wisesorb-Moisture-Eliminator-Fragranc... The bags have Calcium Chloride and absorb water from unsaturated air and make small drops of water. It's obvious that they get depleted, and to use them again you must buy a new one or boil all the water to get the crystals again.
In this new material, the droplets are attached to the material. To remove them you must use energy. They don't just drop to a bucket bellow the device magically. You can't use it to "harvest" water without energy. You can sweep the droplets with a paper towel, but now to remove the water from the paper towel you need energy.
> With a material that could potentially defy the laws of physics in their hands
This does not break the laws of physics. It would be nice that the PR department of the universities get a short course explaining that if they believe the laws of physics are broken, then they must double check with the authors and then triple check with another independent experts. Tech journalist should take the same course.
Note that the bad sentence and the misleading title is from the university https://blog.seas.upenn.edu/penn-engineers-discover-a-new-cl...