
A Rooftop Device That Can Make Solar Power and Cool Buildings - blue_devil
https://news.stanford.edu/press-releases/2018/11/08/new-device-can-cy-cool-buildings/
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dublin
An interesting idea, but it's total wishcraft at this point. One significant
thing the article misses is that if ( _big_ if!) they can make this work, it
could significantly increase the power output of the solar cells, since PV
cell voltage is inversely a function of junction temperature. (Current is a
function of insolation. This is why PV panels make much more power on a cold,
clear winter day than they do in the middle of a Texas summer - the extra
voltage more than makes up for the smaller winter current. And why although
they've never caught on for cost reasons, hybrid PV/thermal panels can make
sense on two fronts.)

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chopin
Afaik the radiative cooling element should not point to the sun for good
performance. On the other hand you want to have your solar cell pointing _to_
the sun. So at least one of them doesn't perform well.

Eg. on a building with tilted roof (prevalent in Middle Europe ) one would
like to mount the former on the north side and the latter on the south side
for good performance. Unfortunately the article does make no mention of it.

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richardw
I think you can lens the lower radiation away from the sun. A fresnel-like
arrangement that points light from under the panel in a direction other than
that of the panel.

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pwinnski
"...That Can Make Solar Power and Cool Buildings" but "What they weren’t able
to test is whether the device also produced electricity. The upper layer in
this experiment lacked the metal foil, normally found in solar cells, that
would have blocked the infrared light from escaping."

They've invented an over-elaborate heat shield until they can demonstrate what
the title promises.

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RenRav
What I'm more interested in is passive cooling for solar panels. We lose so
much efficiency from higher temps. Placing them on our hot roofs, even with an
air gap, is just ridiculous.

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Yetanfou
Combine that passive cooling with a heat pump to create hot water from PV
panel waste heat and you'll both gain efficiency as well as a hot water
source.

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thinkcontext
Here's a DIYer that did that but instead of hot water used a minisplit

[https://renewablesystemstechnology.com/solar-heat-pump-
syste...](https://renewablesystemstechnology.com/solar-heat-pump-system.html)

~~~
Yetanfou
Although a simpler solution to build due to the absence of liquid coolant I'd
still choose a combination of PV-panels with liquid-based collectors attached
to the back as this also makes it possible to circulate warm coolant through
the collector to de-ice/snow the panels in wintertime.

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sumnulu
(video)
[https://www.ted.com/talks/aaswath_raman_how_we_can_turn_the_...](https://www.ted.com/talks/aaswath_raman_how_we_can_turn_the_cold_of_outer_space_into_a_renewable_resource/transcript?language=en)

> "What if we could use the cold darkness of outer space to cool buildings on
> earth? In this mind-blowing talk, physicist Aaswath Raman details the
> technology he's developing to harness "night-sky cooling" \-- a natural
> phenomenon where infrared light escapes earth and heads to space, carrying
> heat along with it -- which could dramatically reduce the energy used by our
> cooling systems (and the pollution they cause). Learn more about how this
> approach could lead us towards a future where we intelligently tap into the
> energy of the universe."

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gns24
This makes no sense to me. The article states that there is one frequency of
radiation that will pass through the atmosphere, so the device radiates at
that wavelength. But why would it make any difference? The atmosphere might
reflect most radiation back to earth, but not back to the point it came from.
So it shouldn't matter what frequency the device is radiating - its radiation
will be reflected elsewhere, and radiation from elsewhere will be reflected to
it.

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TeMPOraL
IANAPhysicist, but AFAIU, radiators work both ways. That is, they're also
absorbers. So on the frequencies that don't pass through the atmosphere, "your
heat" may end up elsewhere on the planet, but you'll also catch radiation
emitted everywhere else. You'll eventually reach equilibrium with the average
amount of heat that is "available" on this frequency. On the other hand, if
your radiator is tuned to the frequency that passes through the atmosphere,
you emit your heat, but don't absorb heat in return. The equilibrium point
you'll be trying to reach is that of deep space.

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the8472
Emitters in the infrared window have been in the news before[0], but has there
been any realworld deployments?

[0] [https://news.stanford.edu/news/2014/november/radiative-
cooli...](https://news.stanford.edu/news/2014/november/radiative-cooling-
mirror-112614.html)

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Tade0
A similar cooling effect, though less powerful, has been achieved in specially
treated wood:

[https://www.sciencemag.org/news/2019/05/engineered-wood-
radi...](https://www.sciencemag.org/news/2019/05/engineered-wood-radiates-
heat-space-potentially-slashing-cooling-costs)

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mrfusion
I wonder if they could make that material into shirts or hats?

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iamgopal
Doesn't solar cell does that too ?

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benj111
_Make_ solar power?

Surely the sun makes the solar power and a solar panel turns that into
electrical power?

