Elizabeth Barrette (ysabetwordsmith) wrote,
Elizabeth Barrette

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Radiative Cooling

My partner read me an article about SkyCool Systems, which has invented a film that can do passive cooling by radiating energy out into space. It has some very interesting potential, although pinning down some important aspects is a challenge.

* My first question was, "What's the limiting ingredient?" Because most fancy science tricks are done with rare earths or something else in short supply, which minimizes the scalability. (Peak lithium could screw us a lot harder than peak oil, but that's only one example.) But later in the article it mentioned the eerie effect of touching something cold on a hot day, and I've actually had that experience in White Sands. The gypsum not only didn't heat in the sun, it cooled a foot or two of air above it, creating a bizarre tangible gradient. Gypsum is common as dirt, so if that's the key ingredient, the technology is much more scalable than if it relies on rare earth(s). Alas, I could not pin down the ingredients used to make the film, so this aspect remains unknown.

* It uses nanotech. It's possibly the most responsible use of that technology I've seen yet. However, nanotech is ruinously expensive at this state of development; it doesn't get cheap until rather later. This limits applications in places where it's needed most, like developing nations. We'll have to wait and see what economies of scale can do for it.

* It's billed as passive cooling. Now, it can work that way, just by itself. But the system they're promoting most is actually an active cooling system that pipes water through tubes under the panel, which cools the water and thus makes an attached air conditioner more efficient. You don't need energy to make the panel work, but you do to move the water -- which means probably electricity. You could pump with animal or human power, but most places don't do that anymore. Always read the fine print. Me, I'd try the actually passive version as a shade to minimize heating of parking spaces. Hell, it'd be useful just as a heat pump to get thermal energy the fuck off this planet.

They're also exploring some other things. One uses heat differential to make light. Now, we've had variations of this one in the past, generating energy from heat differentials; cute trick but it's a side step. If the claim is accurate that the film radiates energy into space -- if they're taking heat waves and altering the wavelength so they actually leave the atmosphere instead of just hanging around in the air -- then they just did the hardest part of treating the electromagnetic spectrum as a slinky. The most useful application for that is actually in killing waste heat, which is a big problem in some industries and will get worse as global warming drives up the temperatures. If you could turn waste heat into something harmless or even useful, instead of merely moving it around or using it as raw material for the next factory, that would be an enormous help. Of course, if you can manipulate wavelengths, you can also change nonvisible waves into visible waves directly. The most efficient way to do that is to find a material that naturally squeezes or stretches the slinky, like this film is described doing, only for visible light you need different output ranges.

Bear in mind that manipulating the electromagnetic spectrum -- not just using accessible parts of it, but directly squeezing or stretching it to make it do what you want -- is a keystone technology of advanced spacefaring civilizations. Usually you start out with starships using radiators to dump waste heat into space, rather than recapturing it to make desirable energy, which is a much cruder use of radiative heating. And if the articles are accurate, then these guys just did the hard thing on a planet. Damn. That's impressive. Once you've got the concept "energy is a slinky" then iterating that to other exchanges is fairly straightforward; you just need to hunt for materials and/or shapes that change an unwanted bandwidth into a wanted bandwidth along different ranges.
Tags: energy, environment, news, science
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