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Program or device to show how light rays go in diagram?

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Posted by brian on August 17, 2008, 6:29 pm
I want to to make a compound parbolic concentrator. (ideally like a big bell
upside down). But mylar does not go to bell shapes easily. I was going
instead to make 4 mylar troughs joined together to make a reasonably close
bell shape. I want to test it before making to see that it will still
concentrate fairly well. Is there a program where you can make a shape on
computer, and then shine a line of light on it and see where it bounces to?
No more than 5 bounces are necessary. And it would be nice to be able to
move the first "ray" to simulate the sun moving.
My compound parabolic concentrator is to be good for 3 hours of solar
cooking at the bottom of the upturned bell. (It will be about 6 ft high and
collect about 1m2 of light and concentrate it to about a ft square area. I
think 34 cm by 34 cm to be more exact.
Thanks in advance.
Brian White

Posted by Morris Dovey on August 18, 2008, 2:08 am
brian wrote:

I'd like to have that same piece of software, and finally decided that
it was easier to just build the trough (you can see some photos of the
construction method I used at:


I'd still like to be able to model other reflecting surfaces but while
modeling isn't really difficult, it does get a bit "messy".

I've heard that this might be possible in some CAD programs - and if
anyone in alt.solar.thermal is aware of a package that does this, I'd be
interested, too.

Morris Dovey
DeSoto Solar
DeSoto, Iowa USA

Posted by ohara5.0 on August 18, 2008, 4:16 am
 On Aug 17, 11:37 pm, david.willi...@bayman.org (David Williams) wrote:

google "Ray Tracing".  There are some free programs available and some
that cost a lot.  The one i am most familiar with "OptiCad" is costly
but easily does CPC type optics and allows you to introduce things
like poor shapes.

Posted by renewable_sources on August 18, 2008, 1:54 pm
To bond your tube to the flat plate try a mix of Epoxy resin with
powdered aluminum and carbon for color ( or grind up some graphite or
aquarium filter charcoal) use enough to make a filet on both sides of
the tube.  Gel type epoxy resin is best to prevent run off. It should
be a thick paste in consistency. Heat transfer is provided by the
powdered aluminum.


Posted by Solar Mike on August 21, 2008, 9:00 am
I have already tried this and after a while the bond always breaks, caused
by the different expansion rates of the two metals. The break then becomes a
thermal barrier. Best to use a filler that never sets or sets to a flexible

Silicon grout is a suitable choice as it contains a ceramic filler that
helps conduct the heat, or use a thermal heatsink compound, or high a temp

Mike (NZ)

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