Hybrid Car – More Fun with Less Gas

Air Collector - Black Heat Paint vs Selective Paint? - Page 4

register ::  Login Password  :: Lost Password?
Posted by Morris Dovey on January 14, 2006, 7:16 pm
 
daestrom (in Z39yf.64079$XJ5.58076@twister.nyroc.rr.com) said:

|| The one normal one will collect more heat as it has
|| less surface to reradiate heat away.

My server missed SolarFlaire's post - I'm glad you quoted to I know to
go to Google groups...

Re-radiation wasn't wasn't my primary concern when I asked; but it
certainly is part of the picture. This prompts me to inquire into the
manner in which energy is re-radiated. Should it be considered as
being emitted normal to the hot surface; or is it more correctly
thought of as omnidirectional?

| An interesting point.
|
| Also, just about any surface reflects a different amount depending
| on the angle of incoming sunlight.  More reflection, less
| absorption.

This comes closer to my original question. Remember that the surface
is smooth and the metal opaque - are you saying that there is a
surface effect analogous to critical angle behavior of glass?

I'm having difficulty wrapping my head around this...

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



Posted by SolarFlaire on January 14, 2006, 8:45 pm
 
May not get this post but, there may be totally
different reflective amounts of energy at the different
spectrums. In other words if you are collecting heat it
may a totally different picture than collecting PV
electricity.

I have not obtained information on this as yet. It may
be needed at specific times, for specific interests so
I haven't bothered.


Z39yf.64079$XJ5.58076@twister.nyroc.rr.com) said:
message

quoted to I know to

asked; but it

inquire into the

considered as

more correctly

amount depending

reflection, less

that the surface

there is a

of glass?


Posted by Morris Dovey on January 14, 2006, 9:14 pm
 On Jan 14, 2:45 pm SolarFlaire wrote (captured from Google groups):

<< May not get this post but, there may be totally
different reflective amounts of energy at the different
spectrums. In other words if you are collecting heat it
may a totally different picture than collecting PV
electricity.


I have not obtained information on this as yet. It may
be needed at specific times, for specific interests so
I haven't bothered. >>

Thanks for responding - even though news.qwest.net doesn't seem to
like you :-)

I'm collecting heat and my absorber consists of very thin black
horizontal aluminum ribbons that have been curved so that any sunlight
reflected from one ribbon is "focused" on the back of the ribbon
directly above it. At present the ribbons are spaced such that (if all
surfaces were mirrored) there would be no (reflective) return path to
the glazing. [If you have difficulty visualizing from this
description, one of the photos at the link below might clarify
somewhat.]

The heat is transfered to air circulating (bottom to top, as you'd
expect) over both surfaces of these ribbons and this heated air is
delivered into the space being heated.

I've experimented with this approach until I've satisfied myself that
it's working well, now I'm trying to zero in on an optimal spacing for
the ribbons...

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



Posted by SJC on January 16, 2006, 8:49 pm
 

  It looks like you have a good idea to me. I have thought that
the radiation is more omnidirectional and longer wave and is
related to the temperature. In other words, the hotter it gets the
more radiation given off. I think that is why selective coatings
are used on trough concentrators that get well above 300f.

Posted by Morris Dovey on January 16, 2006, 11:25 pm
 SJC (in MFTyf.22828$MG1.8271@trnddc05) said:

<snip>

| I have thought that
| the radiation is more omnidirectional and longer wave and is
| related to the temperature.

Shucks - and thanks. That means that efficiency should go up if the
ribbons are more closely spaced - which means it'll take more
aluminum. Not good since one of my objectives was to minimize the
materials energy requirement.

I think I try halving the spacing between ribbons and see how
performance changes. I'm pretty sure there's a point of diminishing
returns here somewhere; but haven't a clue where it might be.

This business of building/measuring/discarding is beginning to seem
frustratingly expensive. How come I can never find a physicist when I
really need one?

[I _still_ haven't figured out if photons are more like boogers or
BBs.] :-/

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



This Thread
Bookmark this thread:
 
 
 
 
 
 
  •  
  • Subject
  • Author
  • Date
please rate this thread