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Cody -<br>
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<div>That would be good for a concentrated solar array. Do you
have any idea how it works?</div>
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<a class="moz-txt-link-freetext" href="https://ui.adsabs.harvard.edu/abs/2019JPhD...52A5501O/abstract">https://ui.adsabs.harvard.edu/abs/2019JPhD...52A5501O/abstract</a><br>
<p>I always wondered if (when) someone would achieve this... as the
article alludes, the effect is similar to the visible-spectrum PV
we are familiar with, but in a much different spectrum (related to
a 1900-2400C black-body). TPVs in the near-infrared are not new
but the energy density isn't as nearly as high and I think
primarily used in very niche applications.
<a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Thermophotovoltaic">https://en.wikipedia.org/wiki/Thermophotovoltaic</a><br>
</p>
<p>You are probably already familiar with Thermocouples, Thermo
Electric Generators (TEG) and heat/cool solid state devices based
on the Seebeck or Peltier (respectively) effects. The TEG effect
is less sensitive to temperature *range* and depends only on a
temperature *gradient* and is related to differential movement of
charge-carriers in different metals. These have very low
efficiencies as well as most sources being intrinsically
low-energy density. Common examples are 12V coolers and woodstove
fans where convenience outweighs low efficiency.
<a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Thermoelectric_effect">https://en.wikipedia.org/wiki/Thermoelectric_effect</a> <br>
</p>
<p>There is also a technology known as Thermo Photonic Generation
(TPX) which has an extra level of indirection... with a *biased*
LED exposed to thermal radiation re-emitting the energy at a
frequency that can be used by a more conventional PV cell.
<a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Thermophotonics">https://en.wikipedia.org/wiki/Thermophotonics</a><br>
</p>
<p>There is a (roughly) 6 meter diameter solar collector near my
house (on Pojoaque Pueblo land) that was part of a
proof-of-concept project spinoff from LANL for concentrated solar
*hydrogen* conversion... I don't remember what temperatures they
were achieving at the focal point, but the "generator" on an
articulating boom is probabl .5x1.5 M across with a quartz? window
and well-insulated tubes coming in/out. As I understand it, the
hydrogen-generation was effected with/through high-temperature
steam. I don't know if the working fluid is steam or something
less corrosive. 15 years abandoned, it is now quite defunct with
individual mirror segments (.5mx.5m) dangling from their bases.
<br>
</p>
<p>An obvious problem with these very high temperature systems is
that common materials tend to be mechanically (melting) and/or
chemically (oxidizing, etc). <br>
</p>
<p>I don't know the practical limits on *linear* solar
concentrators, but with the sun offering up approximately
1000W/m^2 one can likely reach the temperatures for this new
device without the complications of 2D parabolics.</p>
<p>As a neo-retro (mostly) low-tech DIY guy, I am a fan of low-grade
energy sources.<br>
</p>
<p>It won't surprise you that I have 2 huge front-surface mirrors
just waiting for someone to put them to a good use. they are
roughly 1.5mx2.1m (5'x7') and are optical grade (not that this
matters) aluminized mylar stretched over a frame which happens to
be closed on the back. There are pressure-equalization holes
(valves) in the frame but in principle one could close them up and
draw a vacuum and get a very shallow concave (catenary?) shape.
They only weigh about 10-15kg and I could even deliver! I could
probably throw in a 3x5 fresnel lens if you want to make a
sand-fusing 3D printer or solar forge in your backyard? They
would also be useful in a dance studio or (narcissistic) gym
environment. Free for the taking (including delivery).<br>
</p>
<p>FWIW I tried to contritely use only CGS/SI units here... but I
continue to reserve the right, no matter the units, to take
advantage of the intuitively (and mechanically) convenient
fractional arithmetic that comes with folding or separating things
into halves, thirds, etc as well as working with 3/4/5
triangles. I grew up *just* before calculators and computers
were common and did learn a slide-rule and acknowledge that slide
rules do not have fractional inch measures on them. I once had a
roughly 1.5 meter one (from a classroom) and one probably no
longer than 10-15cm in length (yes, I have to calculate those from
my intuitive feet and inch estimates). Neither was particularly
practical.</p>
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data-smartmail="gmail_signature">
<div dir="ltr">Cody Smith</div>
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<div dir="ltr" class="gmail_attr">On Wed, Apr 13, 2022 at 10:43
AM Roger Critchlow <<a href="mailto:rec@elf.org"
moz-do-not-send="true" class="moz-txt-link-freetext">rec@elf.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr"><a
href="https://news.mit.edu/2022/thermal-heat-engine-0413"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">https://news.mit.edu/2022/thermal-heat-engine-0413</a><br>
<div><br>
</div>
<div>Thermophotovoltaic, converts 1900-2400C source photons
to electricity at >40% efficiency.</div>
<div><br>
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<div>-- rec --</div>
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