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tank sizing - Page 3

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Posted by Solar Mike on March 23, 2008, 11:41 pm

44 gallon drums have a large surface area, so if painted matt black with an
air flow running past them, sitting on blocks so the bottom also allows some
air contact, I guess knowing the surface area, the conductance of air and
the drum temp you could work out the effective heat transfer per drum. If
the air is circulating via a small house fan then extra fins may be
unnecessary, there will just be more around trips.

Seems thats the way to do it, if connected just at the tops, or bottoms then
the drum contents will stratify rather all being at an even temperature.
Problem is making a long term reliable seal at each joint. I would on metal
drums weld a pipe fitting for push on rubber hose.

What about corrosion of your steel drums. Even though the same water is
circulating, some air will get dissolved in the water and cause rust. If
they come with removable clamp on lids then you could get their insides
epoxied in zinc rich paint or get them zinc dipped.

The plastic drums would need some supporting rails to keep their shape which
will be a hindrance to airflow, unless the temp is kept lower by having more
water to solar area ratio.

Mike (NZ)

Posted by gary on March 22, 2008, 1:57 pm
That sounds about right to me Jeff.

I think I am in about the same relative heat loss to collector area
situation as you are, and I sized my tank to hold the collected energy
for a full sunny day.   This turns out to be pretty close to the rule
of thumb you hear a lot of 1.5 to 2 gallons of storage per sqft of
collector.   My system is 240 sqft with about 420 gallons of storage
and it works out fine.
About the only time I've wished for more storage is during a string of
sunny days in the fall.  The ambient temps are high enough that I
can't use all the heat overnight, and the tank temperature starts
getting up toward 160F -- but this is rare, and does not really waste
much energy anyway.


Posted by Jeff on March 22, 2008, 4:44 pm
 gary@builditsolar.com wrote:

   Thanks Gary.

   I had just been reading a Nick post about storage and the tanks he
mentioned were 4'* 8' * 3' and I *think* he mentioned two! I've heard
other people talk about large tanks also.

   I've been thinking small and lately have considered 3 or 4 55 gallon
drums linked, perhaps in a double wall box made of polyiso (as it only
has to hold insulation), with the wall cavity filled with cellulose.

  I'm usually better at coming up with cheap ideas, than good ideas!


Posted by Jeff on March 26, 2008, 1:26 am
 On Sat, 22 Mar 2008 12:44:25 -0400, Jeff wrote:

hEY, d00d,  we look alike? Care to blow your Siamese bro?

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