| Topic: |
Science > Physics |
| User: |
"" |
| Date: |
14 Aug 2005 02:53:13 AM |
| Object: |
which metal for best reflectance of solar heat? |
Solar insolation has a spectrum of wavelengths.
And different metals have different reflectances at various
wavelengths.
in an application requiring REFLECTANCE of solar insolation, which
metallization will reflect away, the most solar thermal gain? Gold,
Rhodium?
I prefer to avoid silver because it requires heavy to remediate
tarnishing.... or is it so good that the maintenance effort is worth
it?
How close does plain old aluminum foil come to the others?
I know that there is range of reflectance materials commercially sold;
they might eventually be chosen. In the mean time, I'm curious about
the above questions.
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| User: "CWatters" |
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| Title: Re: which metal for best reflectance of solar heat? |
14 Aug 2005 02:36:00 PM |
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<phlegmatico@yahoo.com> wrote in message
news:1124005993.534481.236750@o13g2000cwo.googlegroups.com...
Solar insolation has a spectrum of wavelengths.
And different metals have different reflectances at various
wavelengths.
in an application requiring REFLECTANCE of solar insolation, which
metallization will reflect away, the most solar thermal gain? Gold,
Rhodium?
or more ordinary materials (scroll down)
http://www.glacierbay.com/Heatprop.asp
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| User: "Uncle Al" |
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| Title: Re: which metal for best reflectance of solar heat? |
14 Aug 2005 02:36:05 PM |
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wrote:
Solar insolation has a spectrum of wavelengths.
And different metals have different reflectances at various
wavelengths.
in an application requiring REFLECTANCE of solar insolation, which
metallization will reflect away, the most solar thermal gain? Gold,
Rhodium?
I prefer to avoid silver because it requires heavy to remediate
tarnishing.... or is it so good that the maintenance effort is worth
it?
How close does plain old aluminum foil come to the others?
I know that there is range of reflectance materials commercially sold;
they might eventually be chosen. In the mean time, I'm curious about
the above questions.
Depends on your wavelength window. Pull a CRC Handbook and look it up
- "Optical Properties of Metals and Semiconductors" Aluminum is tops
in the UV to visible, gold edges it out as you go deeper into the IR.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
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| User: "Ken S. Tucker" |
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| Title: Re: which metal for best reflectance of solar heat? |
15 Aug 2005 01:27:03 AM |
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Uncle Al wrote:
phlegmatico@yahoo.com wrote:
Solar insolation has a spectrum of wavelengths.
And different metals have different reflectances at various
wavelengths.
in an application requiring REFLECTANCE of solar insolation, which
metallization will reflect away, the most solar thermal gain? Gold,
Rhodium?
I prefer to avoid silver because it requires heavy to remediate
tarnishing.... or is it so good that the maintenance effort is worth
it?
How close does plain old aluminum foil come to the others?
I know that there is range of reflectance materials commercially sold;
they might eventually be chosen. In the mean time, I'm curious about
the above questions.
Depends on your wavelength window. Pull a CRC Handbook and look it up
- "Optical Properties of Metals and Semiconductors" Aluminum is tops
in the UV to visible, gold edges it out as you go deeper into the IR.
I put Al on the walls near my wood stove, 4" away
the Al was cool when the stove was cooking hot IR.
Yet windows a few feet away where very warm.
Ken
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| User: "Andy Resnick" |
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| Title: Re: which metal for best reflectance of solar heat? |
19 Aug 2005 11:48:32 AM |
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wrote:
Solar insolation has a spectrum of wavelengths.
And different metals have different reflectances at various
wavelengths.
in an application requiring REFLECTANCE of solar insolation, which
metallization will reflect away, the most solar thermal gain? Gold,
Rhodium?
I prefer to avoid silver because it requires heavy to remediate
tarnishing.... or is it so good that the maintenance effort is worth
it?
How close does plain old aluminum foil come to the others?
I know that there is range of reflectance materials commercially sold;
they might eventually be chosen. In the mean time, I'm curious about
the above questions.
What's your application? Are you concerned with long-term oxidation of
the metal (i.e. aluminum vs. gold)? Chemical resistance? Is there a
waveband of particular importance (i.e. UV, visible, IR, far-IR, etc)?
What about specular vs. diffuse reflections? AFAIK, Spectralon reflects
greater than 99% of incident light from the UV through the IR (although
there's Infragold as well....)
A great reflector in the millimeter-wave are those metallized insulation
panels for home construction. Cheap, flat, and nearly perfect
reflectiors in the GHz.
--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University
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| User: "" |
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| Title: Re: which metal for best reflectance of solar heat? |
20 Aug 2005 04:02:20 AM |
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Andrew Resnick asked:
What's your application?
well, let's see what the original poster said:
an application requiring REFLECTANCE of solar insolation, which
metallization will reflect away, the most solar thermal gain?
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| User: "TokaMundo" |
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| Title: Re: which metal for best reflectance of solar heat? |
19 Aug 2005 12:12:23 PM |
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On Fri, 19 Aug 2005 12:48:32 -0400, Andy Resnick
<andy.resnick@op.case.edu> Gave us:
phlegmatico@yahoo.com wrote:
Solar insolation has a spectrum of wavelengths.
And different metals have different reflectances at various
wavelengths.
in an application requiring REFLECTANCE of solar insolation, which
metallization will reflect away, the most solar thermal gain? Gold,
Rhodium?
I prefer to avoid silver because it requires heavy to remediate
tarnishing.... or is it so good that the maintenance effort is worth
it?
How close does plain old aluminum foil come to the others?
I know that there is range of reflectance materials commercially sold;
they might eventually be chosen. In the mean time, I'm curious about
the above questions.
What's your application? Are you concerned with long-term oxidation of
the metal (i.e. aluminum vs. gold)? Chemical resistance? Is there a
waveband of particular importance (i.e. UV, visible, IR, far-IR, etc)?
What about specular vs. diffuse reflections? AFAIK, Spectralon reflects
greater than 99% of incident light from the UV through the IR (although
there's Infragold as well....)
A great reflector in the millimeter-wave are those metallized insulation
panels for home construction. Cheap, flat, and nearly perfect
reflectiors in the GHz.
Gold makes the best IR mirrors. That is why gold plated films
were/are used on the moon lander and on satellites. Probably
something to do with absorption rates, and surface quality.
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| User: "Timo Nieminen" |
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| Title: Re: which metal for best reflectance of solar heat? |
19 Aug 2005 03:23:02 PM |
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On Fri, 19 Aug 2005, Andy Resnick wrote:
A great reflector in the millimeter-wave are those metallized insulation
panels for home construction. Cheap, flat, and nearly perfect reflectiors in
the GHz.
You wouldn't happen to know how reflective aluminised paper is in the UHF
band, would you? I adopted the physicists solution to keeping out the
summer heat and stapled that stuff to my roof rafters. Works very well
indeed. But I've been considering getting a new teevee antenna, and had
thoughts about putting it in the roof cavity, where it would be below the
foil. I guess the thing to do is to actually try it and see, but a
theoretical perspective can't hurt.
--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html
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| User: "Andy Resnick" |
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| Title: Re: which metal for best reflectance of solar heat? |
22 Aug 2005 08:24:21 AM |
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Timo Nieminen wrote:
On Fri, 19 Aug 2005, Andy Resnick wrote:
A great reflector in the millimeter-wave are those metallized
insulation panels for home construction. Cheap, flat, and nearly
perfect reflectiors in the GHz.
You wouldn't happen to know how reflective aluminised paper is in the
UHF band, would you? I adopted the physicists solution to keeping out
the summer heat and stapled that stuff to my roof rafters. Works very
well indeed. But I've been considering getting a new teevee antenna, and
had thoughts about putting it in the roof cavity, where it would be
below the foil. I guess the thing to do is to actually try it and see,
I don't know what the reflection or absorption coefficient is in the
UHF. Most antennas are out in the open, right? I suspect you'd have
reception problems even without the panels.
--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University
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| User: "Timo Nieminen" |
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| Title: Re: which metal for best reflectance of solar heat? |
22 Aug 2005 02:41:36 PM |
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On Mon, 22 Aug 2005, Andy Resnick wrote:
Timo Nieminen wrote:
On Fri, 19 Aug 2005, Andy Resnick wrote:
A great reflector in the millimeter-wave are those metallized insulation
panels for home construction. Cheap, flat, and nearly perfect reflectiors
in the GHz.
You wouldn't happen to know how reflective aluminised paper is in the UHF
band, would you? I adopted the physicists solution to keeping out the
summer heat and stapled that stuff to my roof rafters. Works very well
indeed. But I've been considering getting a new teevee antenna, and had
thoughts about putting it in the roof cavity, where it would be below the
foil. I guess the thing to do is to actually try it and see,
I don't know what the reflection or absorption coefficient is in the UHF.
Most antennas are out in the open, right? I suspect you'd have reception
problems even without the panels.
Rabbit ears seem to work fine indoors, and there's more blocking their
signal than an antenna in the roof cavity would have. It's just concrete
tiles; corrugated iron roofs might be more troublesome.
I think extra height motivates outdoor placement, but I see that my
current VHF antenna is level with the roof cavity, rather than above it,
and works well.
Time to do an experiment! (Probably take me 3 months to get around to it.)
--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html
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| User: "Full Name EmailAddress" |
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| Title: Re: which metal for best reflectance of solar heat? |
14 Aug 2005 10:03:20 AM |
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On 14 Aug 2005 00:53:13 -0700, wrote:
Solar insolation has a spectrum of wavelengths.
And different metals have different reflectances at various
wavelengths.
in an application requiring REFLECTANCE of solar insolation, which
metallization will reflect away, the most solar thermal gain? Gold,
Rhodium?
I prefer to avoid silver because it requires heavy to remediate
tarnishing.... or is it so good that the maintenance effort is worth
it?
How close does plain old aluminum foil come to the others?
I know that there is range of reflectance materials commercially sold;
they might eventually be chosen. In the mean time, I'm curious about
the above questions.
Gold.
w.
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| User: "Autymn D. C." |
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| Title: Re: which metal for best reflectance of solar heat? |
14 Aug 2005 09:02:27 PM |
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You forget copper.
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