from the we've-been-doing-it-all-wrong? dept.
https://news.mit.edu/2023/surprising-finding-light-makes-water-evaporate-without-heat-1031
https://www.pnas.org/doi/full/10.1073/pnas.2312751120 Note that the paper is not paywalled.
A newly identified process could explain a variety of natural phenomena and enable new approaches to desalination.
Evaporation is happening all around us all the time, from the sweat cooling our bodies to the dew burning off in the morning sun. But science's understanding of this ubiquitous process may have been missing a piece all this time.
In recent years, some researchers have been puzzled upon finding that water in their experiments, which was held in a sponge-like material known as a hydrogel, was evaporating at a higher rate than could be explained by the amount of heat, or thermal energy, that the water was receiving. And the excess has been significant — a doubling, or even a tripling or more, of the theoretical maximum rate.
After carrying out a series of new experiments and simulations, and reexamining some of the results from various groups that claimed to have exceeded the thermal limit, a team of researchers at MIT has reached a startling conclusion: Under certain conditions, at the interface where water meets air, light can directly bring about evaporation without the need for heat, and it actually does so even more efficiently than heat. In these experiments, the water was held in a hydrogel material, but the researchers suggest that the phenomenon may occur under other conditions as well.
The findings are published this week in a paper in PNAS, by MIT postdoc Yaodong Tu, professor of mechanical engineering Gang Chen, and four others.
The phenomenon might play a role in the formation and evolution of fog and clouds, and thus would be important to incorporate into climate models to improve their accuracy, the researchers say. And it might play an important part in many industrial processes such as solar-powered desalination of water, perhaps enabling alternatives to the step of converting sunlight to heat first.
The new findings come as a surprise because water itself does not absorb light to any significant degree. That's why you can see clearly through many feet of clean water to the surface below. So, when the team initially began exploring the process of solar evaporation for desalination, they first put particles of a black, light-absorbing material in a container of water to help convert the sunlight to heat.
Additionally,
It's the most fundamental of processes — the evaporation of water from the surfaces of oceans and lakes, the burning off of fog in the morning sun, and the drying of briny ponds that leaves solid salt behind. Evaporation is all around us, and humans have been observing it and making use of it for as long as we have existed.
[...] In a series of painstakingly precise experiments, a team of researchers at MIT has demonstrated that heat isn't alone in causing water to evaporate. Light, striking the water's surface where air and water meet, can break water molecules away and float them into the air, causing evaporation in the absence of any source of heat.
The astonishing new discovery could have a wide range of significant implications. It could help explain mysterious measurements over the years of how sunlight affects clouds, and therefore affect calculations of the effects of climate change on cloud cover and precipitation. It could also lead to new ways of designing industrial processes such as solar-powered desalination or drying of materials.
https://news.mit.edu/2024/how-light-can-vaporize-water-without-heat-0423
(Score: 2) by RamiK on Wednesday July 03 2024, @07:58PM (2 children)
https://soylentnews.org/article.pl?sid=23/11/04/0337248 [soylentnews.org]
compiling...
(Score: 1) by Runaway1956 on Wednesday July 03 2024, @11:43PM (1 child)
My bad - sorry. Somehow I missed or forgot the first posting, and fell all over myself subbing the story here.
“I have become friends with many school shooters” - Tampon Tim Walz
(Score: 3, Informative) by RamiK on Thursday July 04 2024, @11:43AM
Nah it's just that it's a follow-up paper that confirmed the original and added some details but you happened to use the old summary from the previous press release:
2023: "Plausible photomolecular effect leading to water evaporation exceeding the thermal limit" ( https://www.pnas.org/doi/10.1073/pnas.2312751120 [pnas.org] ) with MIT's press release: https://news.mit.edu/2023/surprising-finding-light-makes-water-evaporate-without-heat-1031 [mit.edu]
2024: "Photomolecular effect: Visible light interaction with air–water interface" ( https://www.pnas.org/doi/10.1073/pnas.2320844121 [pnas.org] ) with MIT's press release: https://news.mit.edu/2024/how-light-can-vaporize-water-without-heat-0423 [mit.edu]
Anyhow, it's good to see Gang Chen back to work after the false indictment and following exoneration [wikipedia.org].
compiling...
(Score: 2) by crm114 on Wednesday July 03 2024, @08:08PM (2 children)
Growing up, my mom dried our clothes on a line, outside.
In the winter, when temps were well below freezing, I had "freeze-dry" underwear. Sun did its thing (UV and all that) and my t-shirts were stiff as a board.
Brought them inside, they folded nice, and they were 1) dry - more than normal 2) smelled wonderful (and yes, industrial near us)
My mom (the one who put the clothes on the line) Salutes you! And me too.... except we have a dryer, and not so clean, not so sanitary... but... hey.
(Score: 3, Touché) by c0lo on Wednesday July 03 2024, @08:48PM (1 child)
Are you sure it was the Sun? Because, you know, your underwear would have freeze-dried at night too, more efficiently so because of a drier air.
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 3, Insightful) by aafcac on Thursday July 04 2024, @12:54AM
Yes, also sublimation is a thing.
(Score: 2) by c0lo on Wednesday July 03 2024, @08:43PM (1 child)
From TFA
Hmmm... Pons & Fleischmann are still waiting for that confirmation.
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by c0lo on Thursday July 04 2024, @01:45AM
thunderf00t's bust of twobitdavinci's take on the topic [youtube.com]
Note: Thunderf00t does not say MIT's results are BS, he points that even the MIT authors have no explanation yet (and that MIT is not immune to occasionally authoring BS).
His beef is with twobitdavinci's sensationalizing of the original FA.
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 3, Disagree) by sonamchauhan on Thursday July 04 2024, @03:12AM (2 children)
Prof. Gerald Pollack at the University of Washington proved that light triggers charge separation in water. This leads to 'vesicle formation' (his term), which facilitates evaporation.
This is outlined in his book: "The fourth phase of water"
(Score: 2) by c0lo on Thursday July 04 2024, @05:05AM (1 child)
Picture me skeptical [unsw.edu.au]
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 3, Interesting) by sonamchauhan on Thursday July 04 2024, @10:18AM
I read this before. But in this battle of the professors (one American, and one Australian), color me skeptical of the Australian professor's skepticism.
The Australian professor is mistaken that the "extra hydrogen atom" will form H₂ molecules. In fact Professor Pollack's work, found the "extra hydrogen atom" in fact exists as a charged proton (H+),. How can a proton combine with another proton to form an H₂ molecule?
(Score: 1) by anubi on Thursday July 04 2024, @06:33AM (1 child)
Light doesn't simply go away when absorbed.
Nothing says it has to transmute directly to heat.
It may alter chemical bonds as well. Photosynthesis. ( Fun Fact - Photosynthesis is an Endothermic reaction ! You get the heat back when you burn plants. ), Photoreactives ( camera film, fading paint, deteriorating plastic ).
Photovoltaics.
-------------------------
https://duckduckgo.com/?q=is+photosynthesis+endothermic%3F&t=brave&ia=web [duckduckgo.com]
"Prove all things; hold fast that which is good." [KJV: I Thessalonians 5:21]
(Score: 3, Informative) by c0lo on Thursday July 04 2024, @12:00PM
As long as the energy is just right - that pesky quantum nature of molecules. Otherwise there's little or no absorption
Soooo... for hydrogen bonds, oscillation and rotation (those last two are quantified too) - the absorption spectrum is in IR. For chemical bonds, you need near UV to alter the chemical bonds.
Incidentally, water is the most transparent for the yellow-green light [wikimedia.org] (claimed to be found as the most efficient for "evaporation by light" by TFA - a thing that raises my suspicion)
https://www.youtube.com/@ProfSteveKeen https://soylentnews.org/~MichaelDavidCrawford
(Score: 2) by ElizabethGreene on Friday July 05 2024, @07:49PM
Roughly a third of my electrical consumption, about $80 per month, is spent evaporating and condensing liquid to move heat around. If there's a more efficient way to do this, I would very much like to know.