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.
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.
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.
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.
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.
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.
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...
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.
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.
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.
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.
Now make this a marketable power-less air dehumidifier. This is one of those 'changing whole industries' things.
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.
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Is it just me or does extracting moisture from the air seem like a really bad idea?
this was certainly amazing to see (at least two years 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-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...