
Material Cools Buildings by Sending Heat into Space - Rylinks
http://www.technologyreview.com/news/532826/material-cools-buildings-by-sending-heat-into-space/
======
dangayle
I'm no scientist, but would there be a way to combine this with solar panels
to also produce electricity? It seems the goals are counter to one another,
but it would really be amazing to accomplish both with one panel.

~~~
chockablock
At the very end of the methods section, they write: "Future designs and
configurations may find ways of using this reflected sunlight, enabling
shorter payback periods and lower levelized costs." I don't have any idea what
they have in mind.

This same group is also trying to solve a related problem, which is how to
keep solar panels cool, since they are less efficient when they heat up. They
have designed coatings that are transparent to sunlight and dump heat to space
(
[http://www.opticsinfobase.org/optica/fulltext.cfm?uri=optica...](http://www.opticsinfobase.org/optica/fulltext.cfm?uri=optica-1-1-32&id=296235)
)

~~~
saeguaiga
If it is used on top of a building certainly the defrosting features of masts
and other fittings look mootable; skylights have shades; you can use the stuff
as the concentrating optic of your choice, so to choose smaller water or
thermovoltaic systems, heat and circulate the pool (hot tub) on the roof, etc.
Taken to architectural limits, thermal cycling wear on all roofing is
lessened. Silage and water loop uses exist as LEED elements, and the swept
radiant flux can even agitate self-cleaning glass.

------
danjayh
One wonders if that this is used extensively in urban areas, could it mitigate
the urban heat island effect to some extent, and in doing so offset some
amount of measured global warming?

------
chockablock
Here's a link to the original article in Nature under their new [0] free read-
only access policy:

[http://rdcu.be/bKmA](http://rdcu.be/bKmA)

[0]: [http://www.nature.com/news/nature-makes-all-articles-free-
to...](http://www.nature.com/news/nature-makes-all-articles-free-to-
view-1.16460)

------
disbelief
So if, in the future, this material was in heavy use atop buildings and
dwellings across the planet, and the heat is all being radiated out the same
thermal window, does this mean that at some set distance from the earth,
there's a ring of extreme heat being generated?

~~~
disbelief
I'm probably missing something in the definition of "thermal window".

~~~
icegreentea
The thermal windows refers to the fact the earth's atmosphere is pretty good
at letting through longer wavelength IR than shorter wavelength IR.

[http://en.wikipedia.org/wiki/File:Atmosfaerisk_spredning.png](http://en.wikipedia.org/wiki/File:Atmosfaerisk_spredning.png)

As an example. Visible light is that little bit all the way to the left. That
entire big chunk on the right is the thermal window that they're talking
about.

------
mrfusion
I wonder if this would be useful for spacecraft?

~~~
chockablock
Surfaces optimized for reflecting and emitting light/heat are indeed used on
spacecraft (
[http://en.wikipedia.org/wiki/Optical_solar_reflector](http://en.wikipedia.org/wiki/Optical_solar_reflector)
)

However you wouldn't have to worry about optimizing these for the atmospheric
IR window, as you do on earth, which is the advance claimed in this paper.

------
diziet
What happens if it gets dirty / rained on?

~~~
GigabyteCoin
The same thing that would happen with glass windows and solar panels. They
would eventually be cleaned.

------
Florin_Andrei
So... a mirror?

~~~
sp332
Yes, but in addition to being a mirror, it absorbs heat energy and emits it as
infrared light in specific frequencies.

