# Concentrators - Sine Law - Page 2

Posted by Morris Dovey on October 10, 2006, 5:59 am

Anthony Matonak (in _bqdnYf8ouc2qLbYnZ2dnUVZ_qWdnZ2d@comcast.com)
said:

| nicksanspam@ece.villanova.edu wrote:
||
||| Concentration ratio is the ratio of the frontal width
||| of the parabola divide by the circumference of the
||
|| Why the circumference, vs the diameter?
|
| Presumably because that is what is receiving the light,
| the surface of the receiver pipe.

Yabbut - only some fraction of that circumference will be receiving
/concentrated/ light; and the concentration is unlikely to be uniform
over that fraction...

--
Morris Dovey
DeSoto Solar
DeSoto, Iowa USA
http://www.iedu.com/DeSoto

Posted by Duane C. Johnson on October 10, 2006, 3:48 pm

Hi Morris;

> Anthony Matonak said:
> | nicksanspam@ece.villanova.edu wrote:

> ||| Concentration ratio is the ratio of the
> ||| frontal width of the parabola divide by
> ||| the circumference of the receiver pipe.

> || Why the circumference, vs the diameter?

> | Presumably because that is what is receiving
> | the light, the surface of the receiver pipe.

> Yabbut - only some fraction of that
> circumference will be receiving /concentrated/
> light;

Technically all the surface receives light from
the mirror (Given perfect optics and ignoring
the direct input from the sun).

> and the concentration is unlikely to be
> uniform over that fraction...

I think the power input varies from 0 to 2 times
the average. 0 away from the mirror to 2 closest
to the mirror.

> I hadda say that. ;-)

> --
> Morris Dovey
> DeSoto Solar
> DeSoto, Iowa USA
> http://www.iedu.com/DeSoto

Duane

--
Home of the \$5 Solar Tracker      Receiver
http://www.redrok.com/led3xassm.htm       [*]
Thermonuclear   Solar Energy from the Sun / |
Energy (the SUN)           \  \     \  /  /  |
Red Rock Energy             \  \     /   /   |
Duane C. Johnson   Designer  \  \  /  \ /    |
1825 Florence St  Heliostat,Control,& Mounts |
White Bear Lake, Minnesota    === \   / \    |
USA      55110-3364                ===   \   |
(651)426-4766        use Courier New Font \  |
redrok@redrok.com     (my email: address)  \ |
http://www.redrok.com   (Web site)          ===

Posted by altsolarthermal on October 10, 2006, 10:58 am

nicksanspam@ece.villanova.edu wrote:

I considered whether concentration referred to the diameter rather than
the
circumference when looking at this.

I eventually thought it referred to the diameter after reading a
Florida
State University tutorial pdf titled as being from Sustainable Energy
Science and Engineeering Center, page 17, -
www.sesec.fsu.edu/documents/lectures/ECS2006/ConcentratingCollector.pdf

I'd really appreciate confirmation that in scientific literature
concentration does actually refer to the the circumference rather than
the
diameter.

Cheers

Glenn Thorpe

Posted by Duane C. Johnson on October 10, 2006, 3:35 pm
Hi Nick;

nicksanspam@ece.villanova.edu wrote:

> > Concentration ratio is the ratio of the frontal
> > width of the parabola divide by the circumference
> > of the receiver pipe.

> Why the circumference, vs the diameter?

Basically because Concentration Factor is a ratio of
areas.
1. The solar capture area normal to the sun.
and convect power back out as losses.

Ok, since this is a trough these reduce down to the
linear parabolic width and the circumference of the

Of course, the lower the receiver area the better.
This has to be tempered with other practicalities
such as the use of round pipe receivers.

High tech cavity receivers could be used which
require much shallower parabola depths and can obtain
higher concentrations. But with the requirement that
the focal length be the same as the depth I suspect
the round pipe is the best solution.

> Nick

Duane

--
Home of the \$5 Solar Tracker      Receiver
http://www.redrok.com/led3xassm.htm       [*]
Thermonuclear   Solar Energy from the Sun / |
Energy (the SUN)           \  \     \  /  /  |
Red Rock Energy             \  \     /   /   |
Duane C. Johnson   Designer  \  \  /  \ /    |
1825 Florence St  Heliostat,Control,& Mounts |
White Bear Lake, Minnesota    === \   / \    |
USA      55110-3364                ===   \   |
(651)426-4766        use Courier New Font \  |
redrok@redrok.com     (my email: address)  \ |
http://www.redrok.com   (Web site)          ===

Posted by nicksanspam on October 10, 2006, 9:39 am

Which figure? I don't see that in the 2006 edition.

Nick

•
• Subject
• Author
• Date
 Re: Concentrators - Sine Law Duane C. Johnso... 10-10-2006
 Re: Concentrators - Sine Law nicksanspam 10-10-2006
 Re: Concentrators - Sine Law Anthony Matonak 10-10-2006
 Re: Concentrators - Sine Law Morris Dovey 10-10-2006
 Re: Concentrators - Sine Law Duane C. Johnso... 10-10-2006
 Re: Concentrators - Sine Law altsolarthermal 10-10-2006
 Re: Concentrators - Sine Law Duane C. Johnso... 10-10-2006
 Re: Concentrators - Sine Law nicksanspam 10-10-2006
 Re: Concentrators - Sine Law Duane C. Johnso... 10-10-2006