Oh, sh*t! Here he comes now...
Posted on 04/16/2013 7:41:37 PM PDT by 2ndDivisionVet
Scientists have found a way to cool houses without air conditioning — and without using any power at all.
Shanhui Fan, professor of electrical engineering at Stanford University, and graduate students, Aaswath Raman, and Eden Rephaeli, are working on a cooling panel that could possibly replace your air conditioner.
How? By radiating the vast majority of incoming sunlight into the outside world.
“The structure basically does two things: It radiates the heat out in the atmosphere into outer space, and the device reflects sunlight to ensure that the sunlight does not heat up the device itself,” explained professor Fan, a Ph.D. in physics from the Massachusetts Institute of Technology.
The device is a metal-dielectric photonic structure capable of radiative cooling in daytime outdoor conditions. The structure behaves as a broadband mirror for solar light, while simultaneously emitting strongly in the mid-infrared within the atmospheric transparency window. What that means: It reflects visible light, and also radiates heat back out with a frequency that allows the infrared waves to pass unimpeded through the atmosphere, back out into space. As a result, it achieves a net cooling power in excess of 100 watts per square meter at ambient temperature.
Furthermore, we’re told by the team that the panel will require no electrical input. Essentially, it will sit on the top of the roof of your house and keep you cool, even on the hottest of days, without drawing any power....
(Excerpt) Read more at venturebeat.com ...
It’s a giant mirror.
With no fans or active circulation isn’t it going to take forever for the heat in your house to make its way to the device for subsequent re-radiation?
I think of hot summer mornings here when the rising sun is heating the east wall of the house (and we need to turn on the A/C at about 9AM). Humidity not really a problem here, though. Tends to be about 40% in an air conditioned house.
Have nothing whatsoever to do with the topic here.
Oh, sh*t! Here he comes now...
I don’t know about it being a scam - they may just be a bit naive or optimistic.
I agree with you, though, a mirror would probably reflect more than this device, including IR, however the reflected IR from the mirror would most likely get absorbed by the atmosphere, whereas they claim that their reflected IR would not.
Regardless the mirror would still cause the house to be cooler, whether it’s enough to compensate for the ambient warm air is doubtful.
Obviously anything that reduces the heat load on the house is useful (that’s why houses are insulated).
So the key question is, is this new thing better and cheaper than insulation?
Even if they get this thing to work and even if it is cheap as dirt to instal and maintain your electricity bill will not go down because the rate will rise since the utility companies still have to fire the generators and the government will tax you on the power you might have used just like the rain taxes.
I stopped reading at the professor of electrical engineering's name -- "Shanhui Fan"!
Ahhhhhhhhhhhhh!
They aren’t very specific on how it removes the heat from the building but I am assuming that the roof load is removed and that might decrease the load on the ceiling but what do you do with the infiltration load and the loads that come from the windows, doors, walls, human activity, appliances and especially the Latent load? Do these panels send the given amount of energy back into space when the sun’s rays are shining directly down upon the panel or when the sun is at all positions during the day?
Two problems here. 1) The band they are using, according to the chart they had (~10 microns) is the wavelength the atmosphere itself radiates. (Which is why infrared astronomers have to build high or go into space). 2) Heat flows from hot to cold, not the other way around. The way an air conditioner works is to make a hot compressed fluid. The heat of the compressed gas is hotter than outside so it can flow outside. The fluid is then allowed to expand making it cooler than ambient. The heat from indoors flows into the cool fluid.
By itself, probably not. But if it can prevent the heating effect of sunlight on the roof it might moderate attic temperatures and reduce the cooling load. In sunlight with an air temp of 105 my attic might be 150 and the AC struggles. I'd love to be able to keep the attic at the ambient temperature.
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