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DIY Solar collector question

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Posted by Keith Youngblood on August 25, 2004, 4:27 pm
 
Hi All,

I am building my first solar hot water collector. It is going to be
24"x48" in size (roughly). I am using 1/2" copper pipes and 22 Ga.
copper sheeting. I have three concerns.

Can I use silver solder to braze it all together? Will this work? I want
to make this panel lead free.

Will 'liver of sulfur' work to make the absorber plate sufficiently
black?  Is this the "poor man's selective coating". Would I be better
off having the absorber plated. Costs? Yikes.

Glass. I read somewhere that the best glass only comes in certain sizes
(made for large collectors). Will it be possible to use regular glass
and have reasonable efficiency?

I don't want to spend way too much for this panel. I have already
shelled out some cash for materials already. Looking to minimize further
expenditures.

Any information you can supply will help me a great deal.

Thank you,
Keith Youngblood


For every complex problem, there is a solution that is simple, neat,
and wrong.
                 -- H. L. Mencken

Posted by WMFisher40 on August 25, 2004, 5:04 pm
 
Keith wrote:


 I'm curious - do you have a good local source for this,
such as Lowe's?  (I'm thinking of using curved reflectors behind the
tubes, made out of cardboard with aluminum foil glued on, mainly for
cheapness and easy availability.)


 Silver solder is relatively expensive, hard to use, but very strong and
high-temperature-tolerant.  I think you can get by with the type of
ordinary low-melting-point lead-free solder they sell now in hardware
stores for general so-called plumbing.  And if you're worried about
toxicity, watch out for cadmium in the solder.

 - Bill F.

 The avoidance of taxes is the only intellectual pursuit that carries any
reward.
   - John Maynard Keynes


Posted by Keith Youngblood on August 26, 2004, 12:13 am
 WMFisher40 wrote:

I got the copper in the form of scraps from a junk yard. It was left
over scraps from a copper roof installation. The scraps were trapazoidal
in shape, curved at one end but pretty clean and straight. They also had
larger pieces that looked green and wrinkled (like they had been run
over). Got 20lbs for 60$. pretty good deal. Nothing corporate though. ;-)

Keith

Posted by JWDoyleJr on August 26, 2004, 1:59 am
 
COMEX price for copper is $.24 per pound.  Your $ per pound at a scrap yard
doesn't look such a pretty good deal here.

I just sold 72 sq ft of RollBond (Trade Mark) collector plate with pump and
controller for $00.  The plates weigh 120 pounds.



Posted by Keith Youngblood on August 26, 2004, 5:30 pm
 JWDoyleJr wrote:


Well, it was cheaper than buying a large piece of 22 Ga. from
onlinemetals.com. I guess that is what I meant by a deal.

Is that the regular price for this stuff?


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