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Build it Solar Collector- General Discussion

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Posted by amdx on September 30, 2008, 4:16 pm
Hi Gary and others,

 I've been looking over the information on Gary's webpages. Thanks very much
for the side by side comparison
of the different type collectors.
 Also thanks for the detailed construction information.

 I'm throwing out a bunch of questions in an effort to learn and get the
collective knowledge to see if there is room to improve
the cost and efficiency of your collector design. I'm sure Gary has pondered
many of my questions!

I like the 33% reduction in cost for the PEX unit, but I'm in Florida and
think the heat could be a problem, so I'll stick with
a copper unit.
The bottom line is economics, cost versus performance. You have hit on a
model that does 96% of your all copper unit.
 I'm impressed!
  Are there any numbers to compare the theoretical maximum solar energy
available to what the best commercial  model can extract?
Or to rephrase, What is the best efficiency obtainable versus your
Copper-Aluminum model?
  Is there any room for efficiency improvement?
If not then cost would be the place to look for improvement.

I'm curious about how thick does the aluminum need to be to carry the heat
to the copper tubing?
How many copper tubes (of what diameter) is required to take the heat away.
 You hit on 0.018" thick aluminum and 7 runs of 1/2" copper pipe.
 I wonder, would 0.010" aluminum do as well?
Would six runs (or five) of copper pipe do as well?
Would you need the thicker aluminum if you used six runs (or five) ?
Would a better thermal compound between the copper and aluminum be worth the

Looking for everyones 2 cents.
                                         Getting excited about solar energy!

Posted by Jeff on September 30, 2008, 7:45 pm
amdx wrote:


Solar collector simulator:


Posted by fdollen on October 3, 2008, 5:24 pm
 I'm curious why a submersible pump is used.  Why not use a pump
mounted out of the tank?

Posted by Cosmopolite on October 4, 2008, 1:13 am
 fdollen@gmail.com wrote:

   Good suction ?  No seals to worry about? cost?

My opinon only.

Posted by gary on October 4, 2008, 5:40 pm
 On Oct 3, 11:24am, fdol...@gmail.com wrote:

I think either works fine.
The submersible pump is actually a little easier to install, and
requires less plumbing.

With the EPDM lined tank, its better if possible to not make
penetrations through the EPDM, and the pumps have to be mounted below
the tank waterline to retain prime after a drainback.  So, if you
mount the pump outside the tank, you have to use an inverted  U-tube
arrangement.  Where the U-tube starts inside the tank near the bottom,
then goes up over the edge, then back down the outside of the tank to
a place below the tank waterline where the pump is mounted.  Not a big
deal, but somewhat more work.

I'm going to be trying a new pump that is intended for water cooling
of PC CPU's.  Its a Swiftech made by Laing.  Supposed to be 50000 hr
MTBF with 140F working temperature capability -- runs on 8 watts with
13 ft startup head, and about 2 gpm flow rate for $5.


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