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Solar Cell Cooling

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Posted by Glenn jacobs on November 16, 2005, 9:13 pm
 
It seems to me that it would be advantageous to paint the rear surface of
solar cells black to provide some cooling via radiation for the cell.  In
addition the fitting of fins on the back for convective fitting might also
improve the efficiency.  Has anyone tried any of these ideas and if so what
were the results.

JakeInHartsel

Posted by Christian Kaiser on November 16, 2005, 10:15 pm
 
Sounds good - although you should choose a paint which has a good heat
diffusion in order not to negate the effect.

Christian



Posted by Paul on November 17, 2005, 4:52 am
 : 7bit


It seems to me that it would be advantageous to paint the rear surface of
solar cells black to provide some cooling via radiation for the cell.  In
addition the fitting of fins on the back for convective fitting might also
improve the efficiency.  Has anyone tried any of these ideas and if so what
were the results.

JakeInHartsel

The last solar cell I bought had light gray paint on the back to reflect the
light back.
I assumed that was to keep the cell cooler and produce more energy. At this web
page you can see the light gray paint in the picture on the right.

http://www.siliconsolar.com/solar_cell.htm  

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<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV>"Glenn jacobs" &lt;<A
A>&gt;
wrote in message <A
3tc$.94qfh1tk0yxb$.dlg@40tude.net</A>...</DIV>
<DIV>It seems to me that it would be advantageous to paint the rear surface
of<BR>solar cells black to provide some cooling via radiation for the
cell.&nbsp; In<BR>addition the fitting of fins on the back for =
convective
fitting might also<BR>improve the efficiency.&nbsp; Has anyone tried any =
of
these ideas and if so what<BR>were the =
results.<BR><BR>JakeInHartsel</DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>The last solar cell I bought had light gray paint
on the back to reflect the light back.</FONT></DIV>

<DIV><FONT face=Arial size=2>I assumed that was to keep the cell cooler and
produce more energy. At this web </FONT></DIV>

<DIV><FONT face=Arial size=2>page you can see&nbsp;the light gray paint in the
picture on the right.</FONT></DIV>

<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV><FONT face=Arial size=2><A
href="http://www.siliconsolar.com/solar_cell.htm">http://www.siliconsol=
ar.com/solar_cell.htm</A></FONT></DIV></BODY></HTML>

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Posted by R.H. Allen on November 17, 2005, 2:38 pm
 Paul wrote:

Heatsinks are frequently attached to concentrator arrays, which would
otherwise get so hot that they would produce virtually no power at all.
For non-concentrating panels, I think the temperature difference between
the cells and the air is probably too small for heatsinks to have much
effect. Even if they do have an effect, it is quite possible the effect
is too small to justify the extra expense associated with the heatsinks.

As for radiative cooling, it is not terribly efficient at the low
temperatures at which solar cells typically operate. If anything, a
white backing material has been found to provide the biggest increase in
performance by helping to reflect light that would otherwise be lost
back into the PV module. However, most manufacturers would probably tell
you that the color of the backing material is of no consequence.


The gray "paint" you see is actually (mostly) oxidized aluminum. It's
applied to the back of the solar cell as a metal paste, then sintered at
high temperature. If you scrape the surface oxide away, you'd find shiny
aluminum underneath. It's used primarily to form the rear contact to the
solar cell, but it also reflects light that reaches the back of the
solar cell back toward the front to give it another chance at being
absorbed in the silicon.

Posted by Paul on November 17, 2005, 6:15 pm
 : 7bit


Paul wrote:

Heatsinks are frequently attached to concentrator arrays, which would
otherwise get so hot that they would produce virtually no power at all.
For non-concentrating panels, I think the temperature difference between
the cells and the air is probably too small for heatsinks to have much
effect. Even if they do have an effect, it is quite possible the effect
is too small to justify the extra expense associated with the heatsinks.

As for radiative cooling, it is not terribly efficient at the low
temperatures at which solar cells typically operate. If anything, a
white backing material has been found to provide the biggest increase in
performance by helping to reflect light that would otherwise be lost
back into the PV module. However, most manufacturers would probably tell
you that the color of the backing material is of no consequence.


The gray "paint" you see is actually (mostly) oxidized aluminum. It's
applied to the back of the solar cell as a metal paste, then sintered at
high temperature. If you scrape the surface oxide away, you'd find shiny
aluminum underneath. It's used primarily to form the rear contact to the
solar cell, but it also reflects light that reaches the back of the
solar cell back toward the front to give it another chance at being
absorbed in the silicon.

  Well, you sound like an expert on the subject. However, this "sintered
metal paste" came off with paint remover and what was left were deposited
metal strips, just like on the front.

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<HTML><HEAD>
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<META content="MSHTML 6.00.2900.2769" name=GENERATOR>
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<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV>
<DIV>"R.H. Allen" &lt;<A
nIxXCOHenZ2dnUVZ_tKdnZ2d@giganews.com</A>...</DIV>
<DIV>Paul wrote:<BR>&gt;&nbsp; <BR>&gt; "Glenn jacobs" &lt;<A
A>
<BR>&gt; &lt;<A
d.net</A>&gt;&gt;
wrote in message <BR>&gt; <A
3tc$.94qfh1tk0yxb$.dlg@40tude.net</A>...<BR>&gt;
It seems to me that it would be advantageous to paint the rear surface
of<BR>&gt; solar cells black to provide some cooling via radiation for the
cell.&nbsp; In<BR>&gt; addition the fitting of fins on the back for =
convective
fitting might also<BR>&gt; improve the efficiency.&nbsp; Has anyone =
tried any of
these ideas and if so what<BR>&gt; were the results.<BR><BR>Heatsinks =
are
frequently attached to concentrator arrays, which would <BR>otherwise =
get so hot
that they would produce virtually no power at all. <BR>For =
non-concentrating
panels, I think the temperature difference between <BR>the cells and the =
air is
probably too small for heatsinks to have much <BR>effect. Even if they =
do have
an effect, it is quite possible the effect <BR>is too small to justify =
the extra
expense associated with the heatsinks.<BR><BR>As for radiative cooling, =
it is
not terribly efficient at the low <BR>temperatures at which solar cells
typically operate. If anything, a <BR>white backing material has been =
found to
provide the biggest increase in <BR>performance by helping to reflect =
light that
would otherwise be lost <BR>back into the PV module. However, most =
manufacturers
would probably tell <BR>you that the color of the backing material is of =
no

consequence.<BR><BR>&gt; The last solar cell I bought had light gray paint on
the back to reflect <BR>&gt; the light back.<BR>&gt; I assumed that was =
to keep
the cell cooler and produce more energy. At <BR>&gt; this web<BR>&gt; =
page you
can see the light gray paint in the picture on the right.<BR>&gt;&nbsp; =
<BR>&gt;
<A
href="http://www.siliconsolar.com/solar_cell.htm">http://www.siliconsol=
ar.com/solar_cell.htm</A><BR><BR>The
gray "paint" you see is actually (mostly) oxidized aluminum. It's =

<BR>applied to
the back of the solar cell as a metal paste, then sintered at <BR>high
temperature. If you scrape the surface oxide away, you'd find shiny =
<BR>aluminum
underneath. It's used primarily to form the rear contact to the =
<BR>solar cell,
but it also reflects light that reaches the back of the <BR>solar cell =
back
toward the front to give it another chance at being <BR>absorbed in the
silicon.</DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>&nbsp; Well, you sound like an expert on the
subject. However, this "sintered</FONT></DIV>

<DIV><FONT face=Arial size=2>metal paste" came off with paint remover and what
was left were deposited</FONT></DIV>

<DIV><FONT face=Arial size=2>metal strips, just like on the front.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT>&nbsp;</DIV></BODY></HTML>

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