New Type of Solar Structure Cools Buildings in Full Sunlight

[OKIsItJustMe]

http://engineering.stanford.edu/news/new-type-solar-structure-cools-buildings-full-sunlight

[font face=Serif][font size=5]New Type of Solar Structure Cools Buildings in Full Sunlight[/font]

[font size=4]A Stanford team has designed an entirely new form of cooling panel that works even when the sun is shining. Such a panel could vastly improve the daylight cooling of buildings, cars and other structures by radiating sunlight back into the chilly vacuum of space.[/font]

[font size=3]
Andrew Myers | Stanford Engineering

Homes and buildings chilled without air conditioners. Car interiors that don't heat up in the summer sun. Tapping the frigid expanses of outer space to cool the planet. Science fiction, you say? Well, maybe not any more.

A team of researchers at Stanford has designed an entirely new form of cooling structure that cools even when the sun is shining. Such a structure could vastly improve the daylight cooling of buildings, cars and other structures by reflecting sunlight back into the chilly vacuum of space. Their paper describing the device was published March 5 in Nano Letters.

“People usually see space as a source of heat from the sun, but away from the sun outer space is really a cold, cold place,” explained Shanhui Fan, professor of electrical engineering and the paper’s senior author. “We’ve developed a new type of structure that reflects the vast majority of sunlight, while at the same time it sends heat into that coldness, which cools manmade structures even in the day time.”

…

Using engineered nanophotonic materials the team was able to strongly suppress how much heat-inducing sunlight the panel absorbs, while it radiates heat very efficiently in the key frequency range necessary to escape Earth’s atmosphere. The material is made of quartz and silicon carbide, both very weak absorbers of sunlight.

…[/font][/font]

http://dx.doi.org/10.1021/nl4004283

[Kurovski]

1. I wish people overall prized and honored high levels of intelligence, knowledge and creativity.

After all, they'll be saving our collective asses, maybe. "Nerds are cool" and other such movements are to be encouraged.

At very minimum it would serve as apology for being so very dumb as a whole. Thanks smart folks.

Or is this solar structure not a smart idea? I don't posses the knowledge to know with certainty.

K&R just in case.

[drm604]

2. The article on the Stanford.edu site doesn't seem very clear, at least to me.

It seems to be describing something that would violate the laws of thermodynamics. Of course, I'm no physicist so I could be missing something.

[Gore1FL]

3. It seems to reflect the energ rather than destroy or create it.

The benefits of this specific idea is that it uses materials that reflect significantly better than they absorb. Think of heat/light absorbing/reflecting differences of black paper and white paper under a light. Perhaps another way to think of it is a high tech version of the polar ice caps that reflect the sun's rays back into space. The difference is the reflection is better and concentrates on bandwidths of light energy that are most easily reflected through the atmosphere.

[OKIsItJustMe]

6. It actually does more than that (in theory at least)

It reflects energy, and it also radiates energy.

Imagine a typical roof. It radiates heat, but it is absorbing sunlight, which means it generates heat as well. In full sunlight, it may easily generate more heat than it radiates (as anyone who has walked on a hot roof can tell you.)

So, let’s put a mirror on the roof. Now, it absorbs less sunlight, yet it still radiates heat.

In this case, they’re proposing optimizing both.

http://pubs.acs.org/doi/abs/10.1021/nl4004283

…

In conclusion, we have numerically demonstrated for the first time a macroscopically planar structure capable of achieving radiative cooling in the daytime, even in the presence of realistic nonradiative heat transfer. In contrast to previous approaches to radiative cooling, we have used concepts from nanophotonics to design a dielectric reflector, which minimizes solar absorption, and a two-layer 2D photonic crystal of SiC and quartz, which selectively emits thermal radiation in the atmospheric transparency window. These two functionalities are combined into a single device that achieves the ultrabroadband performance needed to radiatively cool in the daytime. Currently, applications of thermal light sources are being explored mainly in the field of thermophotovoltaic power conversion but the demands of high-operating temperatures inevitably leads to nano- and microscopic material degradation, presenting a formidable challenge. In our work, we have presented another application of thermal light emission from microstructured materials, radiative cooling. In contrast to previous applications, using thermal light emission to cool structures does not require high temperature operation. We thus anticipate that radiative cooling will motivate continued interest and research in thermal nanophotonics and metamaterials.

[Gore1FL]

9. Thanks!! n/t

[TexasProgresive]

5. As someone said,"There is no free lunch"

If this works there will be at least 1 or 2 downsides. How do the panels transmit radiant heat to space? especially with the increasing "green house effect."

[OKIsItJustMe]

7. “How do the panels transmit radiant heat to space?”

Well, the Earth is constantly radiating heat into space. The “greenhouse effect” means that it is radiating a bit less at certain wave lengths (but not at all wave lengths.)
http://www.climatedata.info/Forcing/Emissions/introduction.html



http://pubs.acs.org/doi/full/10.1021/nl4004283

…

The Earth’s atmosphere has a transparency window for electromagnetic waves between 8–13 μm that coincides with peak thermal radiation wavelengths at typical ambient temperatures. By exploiting this window one can cool a body on the Earth’s surface by radiating its heat away into cold outer space. This radiative cooling mechanism is attractive to energy efficiency improvement efforts because it provides a purely passive cooling strategy for terrestrial structures without the need for any energy inputs.

…

[NYC_SKP]

14. Intuitively, I think these new surfaces are reflecting radiation at higher frequencies...

Higher frequencies than would be reflective by traditional materials like white or bright roofs.

Just as inbound high frequency radiant energy is able to pass though atmospheric GHGs while outbound lower frequency radiation is "absorbed" or re-reflected, it follows then that higher frequency reflected radiation would make it to deep space.

That's my take.

[OKIsItJustMe]

15. (In theory) they would do more than that

http://pubs.acs.org/doi/full/10.1021/nl4004283

…

In conclusion, we have numerically demonstrated for the first time a macroscopically planar structure capable of achieving radiative cooling in the daytime, even in the presence of realistic nonradiative heat transfer. In contrast to previous approaches to radiative cooling, we have used concepts from nanophotonics to design a dielectric reflector, which minimizes solar absorption, and a two-layer 2D photonic crystal of SiC and quartz, which selectively emits thermal radiation in the atmospheric transparency window. These two functionalities are combined into a single device that achieves the ultrabroadband performance needed to radiatively cool in the daytime. Currently, applications of thermal light sources are being explored mainly in the field of thermophotovoltaic power conversion but the demands of high-operating temperatures inevitably leads to nano- and microscopic material degradation, presenting a formidable challenge. In our work, we have presented another application of thermal light emission from microstructured materials, radiative cooling. In contrast to previous applications, using thermal light emission to cool structures does not require high temperature operation. We thus anticipate that radiative cooling will motivate continued interest and research in thermal nanophotonics and metamaterials.

…

[Voice for Peace]

4. "Thanks smart folks"

love it.

[caraher]

8. The way it's described is a bit confusing

To understand this, start with something familiar - 24 hours of clear skies. During the day, the dominant effect is transfer of energy from the hot sun to the cooler Earth, which happens because the atmosphere is largely transparent to sunlight. At night, the reverse happens because outer space is very cold; the extent to which this occurs depends in part on the atmosphere being at least partially transparent to the infrared light the Earth emits by virtue of its temperature. (As you've also probably noticed, it doesn't cool much on cloudy nights, because clouds are not transparent to that infrared light.)

This material has two main features. The first is that it simply reflects most sunlight, and therefore doesn't absorb much energy in the first place. This could be achieved with any good mirror. The novel part lies in its infrared emissions. Ordinary materials emit infrared light across a continuous band of infrared wavelengths, with the exact distribution governed mainly by temperature. Some of that infrared light is at wavelengths the atmosphere absorbs - that's the greenhouse effect. But not all wavelengths are absorbed equally.



What they've engineered is a material that emits less infrared at the wavelengths the atmosphere tends to absorb and more at the wavelengths to which the atmosphere is transparent. This is how they achieve net cooling. It doesn't violate the laws of thermodynamics because energy is still spontaneously flowing from the warmer body (the material) to a colder one (outer space).

[drm604]

10. But the article says that it cools during the day.

[caraher]

11. Yes

The sun does not fill the entire sky; the cooling part of the heat exchange is with the non-sun parts of the sky. Clouds will reduce the cooling effect, but since they also reduce the solar heat load on a building that isn't a big problem

[Gregorian]

12. And radiation is a 4th power of Temp. So it could be very effective.

Thanks for posting that, since I am too lazy to read the article.

[wtmusic]

13. "Desert refrigerators" have been around for millennia

"Nocturnal ice making

In India before the invention of artificial refrigeration technology, ice making by nocturnal cooling was common. The apparatus consisted of a shallow ceramic tray with a thin layer of water, placed outdoors with a clear exposure to the night sky. The bottom and sides were insulated with a thick layer of hay. On a clear night the water would lose heat by radiation upwards. Provided the air was calm and not too far above freezing, heat gain from the surrounding air by convection would be low enough to allow the water to freeze by dawn."

http://en.wikipedia.org/wiki/Radiative_cooling

[IrishAyes]

19. I'm impressed

Not only by what you describe but also another ancient desert method of cooling: the clay pots buried in a pit which has been well covered.

One of the smartest houses I ever read about in Architectural Digest was a place in the AZ desert, somewhere around Phoenix if memory serves. The builder had run long underground pipes radiating in all directions, and they ended with a covered u-turn popup just above ground. At the middle of the hub, in the central hall, the cooled air got sucked up a tall chimney and carried any heat in the house up with it by natural air flow. According to the article, the homeowner said the house kept itself at a maximum of 78 degrees even in the worst of summer with no mechanical aid required. He had also backed the house up against a rock cliff which absorbed heat in the day; then when the curtains were opened on cold nights, the radiated heat warmed the house.

That's how I'd build if money were no problem. Since it is, I might someday sell my beloved Vic and just build myself a little one-story straw bale house. (haha - I could paint it pink and attach a fake curly stovepipe to the outside for a 'tail', then wait to see if anyone got the joke; which they wouldn't around here.) Set up enough solar panels and I might even succeed in going off grid entirely. I don't care for modern design much, unless it's extremely futuristic. But I'm absolutely mad about modern technology.

[wtmusic]

22. If you swap out your Vic be sure to get a gazebo

so you have something to sand and paint every five years. (8-o

That article sounds familiar, I know there is much passive cooling experimentation going on in AZ which seems to be getting hotter every year.

[IrishAyes]

23. Yeah, I wouldn't know how to keep busy w/o rehab

The house, I mean - the house! My own estimate as well as the Amish contractors I use gave the place no more than a few years before it would've been beyond repair. At least with all the time in between projects, I'm saved from possible haste-makes-waste.

Since such a major undertaking sucks up so much $, even with the Amish, I've continued indulging my recycle habits. The arbor out front is made from pieces of metal I picked up when the town used to conduct twice-yearly major cleanup days. I hung a little sign on my "new" arbor announcing that it was the future home of trumpet vines. Thank goodness the winds didn't knock it over before the vines grew big and strong enough to keep it upright. When I see something interesting curbside that's plainly visible, my first reaction is always "What can I make with that?"

Actually, I dread the prospect of nothing to do, because staying busy is the only way I can keep out of trouble and therefore out of jail.

[Progressive dog]

16. Doesn't explain how the building's heat would reach the panels

Isn't that important?

[OKIsItJustMe]

17. Try this Google search

http://www.google.com/search?q=radiative+cooling+buildings

[IrishAyes]

24. Thanks

That's a great link; should keep me busy a good long time.

[IrishAyes]

18. I hope

that this new technology becomes affordable for the public faster than Bloom Boxes have. I'm still waiting on mine. Yet hopefully...

[OKIsItJustMe]

20. I rather doubt it will

“Bloom Boxes” exist today. These panels are much more theoretical.

[IrishAyes]

21. Probably won't happen in my lifetime

I keep hoping the industry giants currently using Bloom Boxes will help speed development of an affordable home version, but I'd never be so foolish as to hold my breath waiting either.

Meanwhile at least I can avail myself of as much passive and active methodology from the past and present as I can.

I also largely escaped the clutches of modern Western 'medicine' most of my life. I'm a fair herbalist and bush medic, not to mention unofficial veterinarian. It goes with the territory.

[Bill USA]

25. fascinating! I missed this, thought others might have too. so kicked. recommended!

[SamKnause]

26. Awesome

Science rocks !!!!!

K&R