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Thermosyphon Solar Panel

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Posted by Malc on July 17, 2007, 8:43 pm
 
Possibly a stupid question here and apologies if it has already been asked.
I did check out the first 50 or so headers and couldn't see it there.

I'm thinking of making a thermosyphon panel out of some scrap copper hot
water tanks and some glass (laminated too!) that I've managed to obtain via
Freecycle. My question is would it be better to make the panels  taller than
they are wide or wider than they are tall? I've got two sheets of copper
about 4ft by 2ft. Or should I join them together and have a 4ft square panel
(though I have got to cut the laminated glass to fit)

Thanks

--
Malc

If you're swimming in a creek
And an eel bites your cheek
That's a moray




Posted by Morris Dovey on July 17, 2007, 9:04 pm
 
Malc wrote:
| Possibly a stupid question here and apologies if it has already
| been asked. I did check out the first 50 or so headers and couldn't
| see it there.
|
| I'm thinking of making a thermosyphon panel out of some scrap
| copper hot water tanks and some glass (laminated too!) that I've
| managed to obtain via Freecycle. My question is would it be better
| to make the panels  taller than they are wide or wider than they
| are tall? I've got two sheets of copper about 4ft by 2ft. Or should
| I join them together and have a 4ft square panel (though I have got
| to cut the laminated glass to fit)

Square.

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



Posted by Malc on July 18, 2007, 6:27 pm
 Morris Dovey wrote:


Heh, the one option I didn't mention ;-) Now are you being serious or just
quite observant.

--
Malc

If you're swimming in a creek
And an eel bites your cheek
That's a moray




Posted by Morris Dovey on July 18, 2007, 8:26 pm
 Malc wrote:
| Morris Dovey wrote:
|
|| Square.
|
| Heh, the one option I didn't mention ;-) Now are you being serious
| or just quite observant.

I was paying attention and trying to give you what I considered to be
the best answer to the question you asked.

A tall narrow panel will run (sub-optimally) hot and will lose too
much of its energy back to the environment.

A short wide panel with adequate provision for removing energy from
the panel and discharging it into the structure will run much cooler
(and be more thermally efficient) but will require a (probably
unacceptable) amount of wall penetration to achieve that thermal
efficiency.

A square panel will require the least amount of sidewall (which will
affect conductive losses) and is a good middle-ground trade-off of the
factors already listed.

A better answer, but not to the question in the way you formulated it,
would be to cut the copper sheets into 1"x24" ribbons, and use them to
build absorbers for panels made up of 24"-wide sections. Hint: It's
possible to form and orient the ribbons to achieve "stealthy" all-band
absorption.

I'm not being faceteous - I've actually done the experiment. It's how
I build my panels (except that I use high-gloss aluminum ribbon). Now,
aren't you /really/ glad you asked?

It's your turn: How are you going to build your panel? :-)

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



Posted by Most Noble and Honourable the on July 19, 2007, 2:51 pm
 
I was planning on using 12mm bore pipe soldered into grooves in the
copper plate. The reason I was asking about short wide vs tall narrow
is that I'm planning on mounting them on the wall of my house and
using them to preheat the water supply to my hot water tank. I know
vertical mounting is not as efficient but as I've stuck my head over
the parapet with my local planning committee about windmills recently
I though I would lie low for a while. The reason for not necessarily
using a square collector was that there is a window at the level at
which I would put the panels and I'd have to work around it.

Still you've given me food for thought, thanks.

--
Malc


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