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"Designer" for solar reflectors - Page 4

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Posted by dow on November 21, 2009, 8:37 pm

Actually, the Holmdel Horn Antenna has precious little to do with what
you want. It is designed to bring radiation (radio waves) that is
arriving from one particular direction to a focus near the narrow end
of the horn. The wide end of the horn is closed by a wall that is
paraboloidal in shape. The radiation enters through the opening in the
side of the horn, is reflected off the paraboloid, and is focused as
it travels down the length of the horn. It is *not* reflected off the
side-walls of the horn, which are there only to give mechanical
support. Similar antennas have used open lattice-work in place of the
solid walls. Many similar horns were used in the early years of
satellite communications, to send signals to the satellites and
receive signals from them.


Posted by Frogwatch on November 25, 2009, 7:05 am

Am happy to see that people have advanced far beyond parabolic
surfaces and into optimum concentrators and illumination optics.
For fabrication of such optics, you might consider "optical
replication" to make them cheaply (at least for reasonably small
optics).  You start with a "mandrel" that is a male version of the
shape you want and then the optic is molded on the outside.  The
mandrel can be re-used many times making the technique kinda cheap.
The mandrel can even be coated with any desired coating that ends up
being on the inside of the reflector surface.
For example, you can start with mandrels made by computer controlled
diamond turning.  These mandrels can be coated with plastic to make
really cheap optics (quantities of dozens)or electroformed with
various metals to make nice metal shells anywhere from .002" up to .
040" thick.  We make optics this way anywhere from 3" diameter
(maximum) and 6" long down to nearly microscopic ones.  These are fun
to make and I am happy to make some for very little for Infra-red and
visible light.
Our money comes from making such optics for x-rays, not exactly common
and very expensive.

Morris:  If you are getting into designing non-imaging optics, you
might consider investing in "Opticad" which is a great ray tracing
program that already has compound elliptical concentrators and
compound elliptical concentrators coded as examples.  It costs a few
thou but is really powerful.

BTW, I see that the new Edmund catalogue has some glass CPC optics.

Posted by dow on November 21, 2009, 1:48 am
Being easy to make is less important than being easy to maintain. The
device might be stamped out in a factory, but the end user will have
to keep the reflective surface clean. Cleaning the inside of the
narrow tube that carries the light toward the target from each "horn"
would be a serious challenge in a third-world environment. Grease from
the food being cooked will get into these tubes, and will ruin their
optical performance.

Human-powered tracking systems, using simple parabolic mirrors, are
quite practical. There are always plenty of children around in third-
world villages. They could easily keep the mirrors aligned properly.
This was done in ancient Egypt, and could be done again today. (There
are a few places in Egypt where it is still done, for the benefit of
tourists.) No motors, computers or electronics are needed.


Posted by Josepi on November 20, 2009, 1:53 am
 So what if a reflector only allows for a single point of heat or solar

You have created a very expensive tracking system. Can't you point it?

Was this whole post only spam to promote your product?

Trough solar system with one very simple tracking mechanism will beat this
hands down for cost and probably output.

Posted by brian white on November 20, 2009, 3:23 am
 It is not my video. I only used it to show the horn flower concept.
It might be possible to apply the horn flower for solar cooking
And I am not selling anything.  I have made a simple method for
designing the horn flowers. (Different flowers for different acceptance
And if you want to sell solar cookers, who wants to have a trough in the
Wouldn't people prefer the pretty flowers?

Josepi wrote:

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