[Greenbuilding] solar heat collection

[Corwyn]

On 7/4/2012 2:02 PM, Clarke Olsen wrote:
>     I am putting together a system with tilt-adjustable panels and a 1000 gal storage tank, in the hope of collecting
> and storing heat year round. The 1400sqft house has radiant tubing in a 3" concrete floor sitting on 1/2" foam over
> a crawl space. The boost from the tank temp to hot shower is handled by Eemax 6.5kw point-of-use instant water
> heaters. The floor circuit also has an Eemax booster. My plan is to run both the domestic hot water and the floor
> circuit through heat exchangers in the 1000 gal storage tank.
>     My question is: should the storage water run through the collectors directly in a drain-back configuration, or is a
> closed-loop, heat exchanger be preferable? This would make 3 sets of loops in the tank, with the collector circuit
> on the bottom.

Drain back is more reliable (fewer things to go wrong) but it requires a 
larger pump to handle the head.  If your collectors aren't much higher 
than your tank, I would consider a drain back system, otherwise a closed 
loop.  Or, if you are prone to power outages, go closed loop on a solar 
panel controlled pump.

Other notes:
1. I think 1000 gallons is probably too large (or not large enough) 
depending on your goals.
2. The heat exchanger loops should be side-by-side.  With the collector 
loop flowing top to bottom, and the other two flowing bottom to top.
3. I recommend that you work out the math for the energy flow, if you 
haven't (if you have, post it here to give us a better idea).
4. Adjusting tilt on water collectors is going to be a royal pain.  And 
probably not needed.
5. I would forget the booster on the floor circuit, too high a current 
needed, and the control circuit would need to be pretty sophisticated. 
If you need supplemental heat just get a cheap heater (again, depending 
on a number of details).

Thank You Kindly,

Corwyn


-- 
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
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topher at greenfret.com
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