Most reflective material for solar shortwave and most emissive for terrestrial long wave?

[shane21]

Looking for recommendations for two commercially available films and coatings, the best for...

#1 - Maximum reflectance, regardless AOI, for short wave sunlight primarily and, secondarily,
reflects some or a lot of long wave, and thirdly, also good emissivity for any of the spectrum.
Appreciate any suggestions for commercially available film and also for a coating.

#2 - A coating or paint that has maximum emissivity for long wave spectrum and is, secondarily,
also highly thermally conductive, too.

Thank you for any suggestions.

 

[davefitz]

Check the NASA database, the engineered selection of surface preparations that separately control emissivity and reflectivity at different wavelengths is discussed in Nasa's Siegel and Howell radiation heat transfer text.

"In this bright future, you can't forget your past..." Bob Marley

 

[shane21]

davefitz, Excellent resource, thanks for that.

Found this, too, from NASA, while searching...
Spacecraft Thermal Control Coatings References

http://www.aztechnology.com/pdfs/nasa-tp-2005-212792-lauder.pdf

...which lists many materials, coatings and paints for reflection and emissivity.

Just have to sort out what's both commercially available, too, and not priced solely for the space program.

 

[davefitz]

Don't forget you will need to wash off the surfaces from time to time, as a coating of dust or oil will completely change the surface properties. That does not seem to be an issue in outer space, though. What may work in space might not be viable on planet earth.

"In this bright future, you can't forget your past..." Bob Marley

 

[IRstuff]

Space, at least, local space, has its own version of dust, namely the thousands of particles of debris from booster exhaust to bits of flotsam and jetsam of broken satellites. While they don't necessarily deposit onto surfaces, some do punch holes into them

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I can do absolutely anything. I'm an expert!

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[shane21]

I've been a fan of aluminum radiant barrier for years for reflecting heat and flat black paint for gaining it or emitting it, but am checking here for what's 'new & improved' to squeeze the maximum %'s.

For current application, I'm looking for the best commercially available film and a coating that's specifically for reflecting a majority of the short wave solar.

And, another coating that's best tuned for emitting the majority of long waves to clear night sky.

 

[IRstuff]

I think you'll find, per table 4.2, that white paint is probably close to ideal. Barium The only other possible solution is quartz (or glass) over silver (or aluminum), which gives you high reflectivity, but the quartz cuts off by around 5 um and becomes emissive beyond that.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529

 

[shane21]

IRstuff,

Yes, white paint is very good, can't go wrong there, I'm just wanting to make sure I've done a comprehensive survey of what all 'new & improved' is out there today.

I see so many ingenious new formulations pushing the envelope, tweaking with nano tech additives, etc.

Upping reflective base from say a respectable 95% to 97-98% or better, is important to me here to get that little extra, if it's out there and affordable.

 

[Compositepro]

"White" only describes how the eye perceives a color. Differing whites can behave very differently in the non-visible wavelengths.

 

[shane21]

Compositepro, true, won't be going for anything I can't get a spectral transmittance chart on it.

- Shane