Jeff wrote:
snip wall insulation stuff
I'm working my way through all the info.
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Got my new collectors up and running, and storage tank in, which now
has about
450 gallons of water at 170F in it -- now I just need to finish the
inside of
the house part to make use of it 
I updated the Solar Shed description to show the new stuff:
http://www.builditsolar.com/Projects.../solarshed.htm
First, I'd like to say that's a fabulous picture of the solar shed with
the mountains in the background!
Its nice to see the snow back on the mountains
Thanks for all the info on the water tank (and the rest of course!).
Oddly I was thinking along the same dimensions. It seems like lower
heights give more storeage capacity for the same amount of EPDM liner.
The 3' height seems like a good compromise between volume and footprint.
One more comment on the tank. It turns out to be important to seal the lid down
well. I had some left over bat insulation over the top of the foamboard cover,
and it picked up a lot of moisture from the escaping vapor. I sealed all the
places I could, and then lag screwed down the cover. This is probably a good
idea from a safety point of view anyway -- I don't think a fall into 170F water
would be fun.
How long did it take to get the tank up to temp? 170F is great! I'm
curious about how many therms you think the collector is yielding on a
typical day.
My differential controller has not arrived yet, so I was just turning the pump
on when the sun got on the collector and off in late afternoon -- I'm sure the
controller will be better. I was also fooling around with things all day, and
had the tank cover off part of the time. But, it went from about 80F up to 143F
the first sunny day. It lost about 5F overnight (something I need to improve a
lot). The next day was also sunny, and it went up to 175F by the end of that
day. The slope of the tank temperature plot looks like it would have kept going
over 175F had the sun not gone away -- i.e. the max temperature appears to be
somewhat greater than 175F. I plan to limit it to around 170F for the sake of
the EPDM liner.
I guess the first days gain implies:
Gain = (143F-80F)(441 gal)(8.3 lb/gal)(1 BTU/lb-F) = 230,600 BTU
For an 80% efficient furnace that would be 231/(100*0.8) = 2.9 therms
This is about (230600 BTU)/(240 sqft) = 960 BTU/sqft of collector
The books says we should be getting about 1850 BTU/sqft-day of sun now, so this
implies a very rough day long efficiency of 960/1850 = 52%
Not so bad, but I would hope to do better with the controller, better tank
insulation, and not fooling around with things all the time.
My initial collector array here (6 - 2' x 10') will be
about a half the size of yours with plans to go half again larger (18 -
2' x 10'). I'm in a milder climate, but will have similar 1" polyiso
insulation, solkote coated home made (I doubt whether I've saved much)
instead of the superior commercial, and suntuf instead of twinwall.
I would think that with that much collector area, and your insulation upgrade
your heating bill would about disappear.
I would really like to hear how the Solkote works out, and how difficult it is
to apply.
I'm plugging away at the boxes and will put up some pics later...
Good!
Cheers,
Jeff
Gary
--
Gary
www.BuildItSolar.com
"Build It Yourself" Solar Projects
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