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A new class of materials that can passively harvest water from air
- DocTomoe 1y agoNow make this a marketable power-less air dehumidifier. This is one of those 'changing whole industries' things.
- WalterGR 1y agoThose 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?
- DocTomoe 1y agoDehumidifier bags are bulky. Surfaces, on the other side, can be folded into loops, which should increase the amount of humidity they can absorb.
- the__alchemist 1y agoSurfaces as you describe go into the bags.
- fuzzfactor 1y agoNever 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.
- gus_massa 1y ago> a new class of nanostructured materials that can pull water from the air, collect it in pores and release it onto surfaces without the need for any external energy As a similar comment note, it's like a high tech Dehumidifier bag. https://www.amazon.com/Wisesorb-Moisture-Eliminator-Fragrance-Dehumidifier/dp/B088N8DGP6?th=1 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-class-of-materials-that-passively-harvest-water-from-air/ https://blog.seas.upenn.edu/penn-engineers-discover-a-new-cl...
- Evidlo 1y agoWhen a publication I was involved in got a university PR piece, they were in direct communication with us
- Y_Y 1y agoAmusingly, 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.
- B1FF_PSUVM 1y agoHonesty 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.
- mistrial9 1y agothis was certainly amazing to see (at least two years ago)
- vintermann 1y agoRepost from four days ago: https://news.ycombinator.com/item?id=44060712 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.
- bayindirh 1y ago> 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 https://dune.fandom.com/wiki/Windtrap
- detourdog 1y agoor moisture vaporators https://starwars.fandom.com/wiki/Moisture_vaporator https://starwars.fandom.com/wiki/Moisture_vaporator
- moffkalast 1y agoBut moisture farming? Really? A man of your talents?
- simiones 1y agoThose 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.
- bayindirh 1y agoWindtraps 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.
- PaulHoule 1y agoSee https://en.wikipedia.org/wiki/Air_well_(condenser) https://en.wikipedia.org/wiki/Air_well_(condenser) and https://en.wikipedia.org/wiki/Fog_collection https://en.wikipedia.org/wiki/Fog_collection and https://en.wikipedia.org/wiki/Atmospheric_water_generator https://en.wikipedia.org/wiki/Atmospheric_water_generator
- Quarrel 1y agoI'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) https://en.wikipedia.org/wiki/Dune_(novel)
- kayodelycaon 1y agoAll 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.
- scotty79 1y agoThis 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.
- salomon812 1y agoI 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 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.
- abracadaniel 1y agoPET 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.
- ajnin 1y agoYeah 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.
- hollosi 1y agoFrom the actual paper ( https://www.science.org/doi/10.1126/sciadv.adu8349 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.
- cjbgkagh 1y agoAh 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.
- Y_Y 1y agoThis 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?
- gopalv 1y ago> 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.
- delusional 1y agoWould 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.
- ChiMan 1y agoUses in AC and clothing seem like obvious use cases.
- andrewrn 1y agoThis 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.
- wheelerwj 1y agoIs it just me or does extracting moisture from the air seem like a really bad idea?
- B1FF_PSUVM 1y agoI 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.
- wheelerwj 1y agoA surplus according to who? Those ecosystems exist for a reason. Are we talking about terraforming Earth? For what purpose?
- circles_for-day 1y agoThis seems like it could be improved with ai-assisted molecular dynamics that have been in the news for drug discovery and protein folding.
- lightedman 1y agoWe 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.
- fblp 1y agoGot a link to how this was made?
- lightedman 1y agoI 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.
- davedigerati 1y agoWith 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-c5cae6726fe6 https://grok.com/share/bGVnYWN5_e80e8100-3682-4157-879e-c5ca...
- gus_massa 1y agoGrok is wrong. The description violates the second law of thermodynamics. But I don't blame Grok, the PR is very misleading.
- mppm 1y agoUnless 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 https://www.science.org/doi/10.1126/sciadv.adu8349
- a1371 1y agoI'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.
- mppm 1y agoWhat 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 https://en.wikipedia.org/wiki/Capillary_condensation
- dfilppi 1y ago[dead]
- fuddy 1y agoI 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.)
- elil17 1y agoPeople 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.
- crazygringo 1y agoDoes 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?
- rtpg 1y agoMy 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.
- scubadude 1y agoRemoving 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.
- bilsbie 1y agoCould 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.
- bilsbie 1y agoI 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.
- ggm 1y agoMangle, 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.
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- TimByte 1y agoI 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.
- Elaris 1y agoIf 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.