
Lasers etch a 'perfect' solar energy absorber - clouddrover
https://www.rochester.edu/newscenter/lasers-etch-a-perfect-solar-energy-absorber-414902/
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pjc50
So the interesting thing is

> reduces heat dissipation at other wavelengths

Most of the time we use the "blackbody" approximation; and we're familiar with
the idea that black objects radiate and absorb heat well, while white or shiny
ones do not. This lets us make something that absorbs like a black object and
emits like a white one. In effect its own surface is like a tiny greenhouse
effect.

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logfromblammo
Or absorbs at visible light frequencies and reflects at lower thermal infrared
frequencies.

Until the object starts to glow red-hot, it will have low radiative losses.
Once it gets that hot--maybe 3000K--it will radiate very well, until cooling
enough to radiate mostly at the longer reflective wavelengths.

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adrianN
This is of course a neat tech demo, but I don't really see the application.
Thermal electrical generation seems to be crap compared to photovoltaics and
for just heating stuff up, black paint must be orders of magnitude cheaper,
even if it might not be a "perfect" absorber of sunlight.

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VBprogrammer
I guess concentrating solar collectors might be a useful application?

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mikro2nd
I'd hazard that this would be an obvious "first application" for this
technique. If they can improve the absorption efficiency by 130%, that
translates to reducing the number of mirrors by something like 25%, so a
fairly significant cost saving. Alternately, if you can capture and store that
energy without increasing costs too much you end up with a more efficient
power plant per unit-area of land. Sounds good to me!

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strangeloops85
To be clear - selective solar absorbers that absorb the solar spectrum well
and have low infrared emissivity (so they don't radiate heat well), are a
mature concept and can be achieved by multilayer coatings pretty well. This is
a nice manufacturing process and could also be a competitive approach compared
to conventional thin film deposition. However, I don't think the specific
performance is dramatically different from things that are used in commercial
solar thermal systems.

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scotty79
> This improved the efficiency of thermal electrical generation by 130 percent
> compared to untreated tungsten.

I wish they would include comparison to tungsten painted black.

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jandrese
Maybe this is for applications where paint would be baked off by the intense
concentrated thermal radiation?

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wiggler00m
Various potential applications in biomedical, environmental, and energy
fields.[1]

Could improve the efficiency of solar thermal power stations:

 _" Control over the absorption spectral range of surfaces is of major
importance for a wide range of applications, such as selective solar
absorbers, thermal emitters, structural colouring water condensation and
daytime and night-time radiative cooling. In particular, for a solar-thermal
energy absorber operating at high temperature, the absorber should be an SSA
since the main cooling mechanism is thermal radiation... an ideal solar light
absorber has nearly 100% absorbance within the solar spectrum and negligible
thermal emittance within the blackbody radiation spectral range at mid-to-high
temperatures (100–500 °C), i.e., an SSA. SSAs can thus maximise the
temperature of solar absorbers and increase the efficiency of a heat engine
driven by solar radiation."_

[1]
[https://www.nature.com/articles/s41377-020-0242-y](https://www.nature.com/articles/s41377-020-0242-y)
(full text paper)

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icedistilled
Or maybe they catch use the tech to launch a competitor to the holographic
chocolate.
[http://www.morphotonix.com/chocolate/](http://www.morphotonix.com/chocolate/)

Edit: Oh sad day, it seems the chocolate may have just been a demo of the
etching and molding technology.

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solarkraft
Maybe not! The mold in the first picture is made by Kaupert, a company
specializing in chocolate molds. Of course they might mean that Kaupert made
the base mold and Morphotonix added the holograph ...

Either way I see a lot of value in this technology, even if it's just for
novelty and a piece of that chocolate would cost 100€, I think there's still a
significant market in the luxury segment.

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griffman99h
The Article also talks about hydrophilic and hydrophobic patterns using the
same setup. I would be interested in seeing the properties of a channel or via
through the tungsten etched with these patterns. It might change the thermal
absorption rate of water passing through the hole or some other neat behavior
like a change to the capillary effect. This could improve concentrated solar
applications even further.

~~~
BlueTemplar
Just like the jellycat turbines ?

[https://www.youtube.com/watch?v=mB5nztzXo24](https://www.youtube.com/watch?v=mB5nztzXo24)

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ww520
This sounds like magic. Very exciting. Is there a diagram or video showing
what the geometry looks like?

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mark-r
Is there any way to create a paint with the same properties, absorbing visible
wavelengths but reflecting infrared?

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vorpalhex
Can we get a title update? Article reads `Lasers etch a 'perfect' solar energy
absorber`.

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logfromblammo
> _"...etching a full-color photograph of a family into the refrigerator door;
> or proposing with a gold engagement ring that matches the color of your
> fiancee’s blue eyes."_

Yeah... they should have stopped at car colors.

