Smart fabric heats up under the sun

https://uwaterloo.ca/news/media/smart-fabric-heats-under-sun

by gnabgib • 1 year ago

37 40 1 year ago

uwaterloo.ca

rokkamokka• 1 year ago

"... enabling the fabric to absorb heat and convert it into warmth" is a fun sentence

Ekaros• 1 year ago

"The design requires no external power"

Umm, so sunlight is not external power?

TuringTourist• 1 year ago

I take "external power" to mean power that is not "free" as in humans paid for it. Otherwise the phrase "External power" is meaningless, as all energy comes from somewhere else eventually. (unless you're at some point in time extremely close to the birth of the universe, then we might accept that it's actually internal or at least locally sourced)

nine_k2• 1 year ago

Converting heat into warmth is like converting meat into a burger. An abstract resource vs a directly consumable thing.

cluckindan3• 1 year ago

Don’t all fabrics already absorb IR and heat up?

This new fabric would need to be the outer layer of a garment to receive light, so no insulation and no layering. Most of the heat would not be warming you up. Seems kinda useless?

I would be more interested in a fabric that cools down under the sun.

mungoman2• 1 year ago

Do I have a treat for you https://youtu.be/G8YBV7GoF_s?feature=shared

rahimnathwani• 1 year ago

  Don’t all fabrics already absorb IR and heat up?

Yes, but the paper's abstract says this fabric heats up faster:

  Through the incorporation of a modest amount (as little as 0.5%) of photothermally active polyaniline (PANI) and polydopamine (PDA) nanoparticles, this fiber exhibits exceptional photothermal conversion performance compared to pure thermoplastic polyurethane (TPU) fiber. Notably, when exposed to 600 W m−2 irradiation for 600 s, the equilibrium temperature of the photo-thermochromic elastic fiber rises impressively from the ambient 20.0 °C to 53.5 °C.

cluckindan3• 1 year ago

So basically useless in winter above 60 degrees latitude, when and where it would be most needed: sun is up only a few hours per day, and only one or two of those hours get 100W per square meter on a clear day.

jajko• 1 year ago

Wear black non-glossy skin tight stuff all over and I can tell you it heats up darn fast to unbearable levels. Great for mountains and cold times though. This must be a smidge better and uses different colors so some evolution it seems.

Depends on price and tons of other aspects like long term durability and resistance to frequent washing to make it interesting for masses, I expect some major issues there

codr7• 1 year ago

Isn't that like, the default?

I would find it more impressive if it didn't.

SapporoChris• 1 year ago

Yes, I am confident that all materials get warmer when exposed to sunlight. Evaporative cooling might be argued as an exception, however I do not consider it so.

There might be some materials that do not absorb solar radiation, I'm not aware of them.

https://en.wikipedia.org/wiki/Evaporative_cooler

xhkkffbf• 1 year ago

What about a mirror?

wongarsu2• 1 year ago

There is radiative cooling paint that in addition to reflecting most light radiates heat in wavelengths that don't get absorbed by the atmosphere. That makes them cooler than ambient temperature when they are under the open sky.

They still get heated by the sun, just less so than everything else. But very similar sounding sentences about them would be true (because on a sunny day, in the shadow, they would be cooler than indoors at the same ambient temperature)

stevage• 1 year ago

It does it better than the default.

HTH.

yapyap• 1 year ago

Stupid fabric also heats up under the sun, as does braindead fabric.

water92• 1 year ago

Yeah, but this one will do your taxes /s

nine_k2• 1 year ago

Stupid fabric can only grab a few degrees, while the smart fabric acquires full 30. A genius fabric could likely boil water in the wintertime with sunlight alone!

cluckindan3• 1 year ago

A wet black sock around a beverage can in direct sunlight will cool down the can as it dries.

viraptor5• 1 year ago

Notably, when exposed to 600 W m−2 irradiation for 600 s, the equilibrium temperature of the photo-thermochromic elastic fiber rises impressively from the ambient 20.0 °C to 53.5 °C.

Does anyone know what's the expected raise from that much energy in basic cotton for comparison?

s0rce• 1 year ago

I naively tried to calculate in a closed system consisting of cotton canvas but I got a temperature rise of 600K. Oh well, I guess heat loss from the system is important.

600 W/m2 / (1.34 kJ/(kg K) * 390 g/m2) * 600s

hammock2• 1 year ago

If we assume a clothes dryer is 3000W, how long does it take a cotton shirt to get heated from 20c to 53c? A few minutes? So perhaps this fabric heats up 3-5x faster

viraptor5• 1 year ago

Different kind of heat transfer. Clothes in the dryer match the temperature of the heated air around them. This paper is about radiated heat captured by the cloth.

metalman• 1 year ago

Having trouble imagining an implimentable use case that will provide a net benifit. The biggest nix on this idea, is that nothing in nature has tried a similar approach, and artic animals have a whole bunch of optical light adaptations , as do sea creatures, many of them are startlingly efficient and complex. See polar bears, with optical fiber white hair that chanels light to black skin and riendeer who can see them by ulra violet light in cold snowy night, when.they are otherwise, invisible. Likely will have industrial uses however.

eqvinox• 1 year ago

After the recent "save 30% power in datacenters" thing¹, I've grown a bit weary of the university of waterloo, and "things get warm in the sun"² isn't helping.

¹ it was a IRQ polling change in the Linux kernel that only helps network-heavy applications under high load with good NIC offload capabilities. I'll accept it might save 30% in the "best degenerate" case, but it'll be nowhere close in general. https://news.ycombinator.com/item?id=42841981

² yes I'm exaggerating. The problem is I have no clue about this heat thing, but I do have an understanding Linux NAPI/IRQ behavior, and that made me with good reason call massive exaggeration there. So what am I to do when I see something from this same source that I don't know about?

foolswisdom• 1 year ago

So what am I to do when I see something from this same source that I don't know about?

Well there's always <https://en.m.wikipedia.org/wiki/Gell-Mann_amnesia_effect>. Sounds like your not as vulnerable though.

calmbonsai• 1 year ago

Gosh, it's almost as if ALL things heat-up under the sun. ;)

Given their (cough) publication history, one would hope UW would've learned by now avoid the terms "smart" and "nano particles".

In actuality, this is the university's PR department completely dropping the ball on how to describe a non-phase-change passive heater https://link.springer.com/article/10.1007/s42114-024-00994-4 .

It's not going to replace good 'ole phase-change pocket warmers or, god forbid, lighter-fluid burners (check out the W/m^2/s), and there's going to be some serious manufacturing R&D to make these fibers into wearable fabrics (hint, substituting phase-change for length-change (color is micro-length adjustment) does not bode well for durable stitching), but it's neither an outright outlandish engineering proposition nor as remotely as "sci-fi" as the article claims.

FWIW, the 600 W/m^2 is often used as a stand-in source for nominal solar irradiance though I can't find the specific spectra of the source. If you're changing color (length), spectra really matters.

I have little doubt the authors of the paper cringed when they saw that headline, but I'm also likewise as sure they're happy to get any press.

Smart fabric heats up under the sun

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