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Old 01-31-10, 10:57 PM   #16
Lurking Renovator
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I haven't even been lurking here, and I nearly forgot this forum existed (I'm a semi-frequent poster on ecomodder)

I've been thinking about making a thermosiphon collector (they are also called Barra systems or Trombe walls) for the back of my house, which pretty much faces due south. I've looked at a number of designs for these (including the one posted by Gary - $350 solar heating thermsiphon collector) including this one on instructables. The corrugated clear plastic glazing, flap valves, and the ~10cm deep seems to be common design aspect. What changes between them are the thermal mass. I personally don't like the idea of using copper purely based on cost unless you can somehow find it for free, but I've considered both the metal screen painted with black BBQ paint, and/or aluminum cans with the bottoms cut out and painted with black BBQ paint. This seems to be like a pretty solid cost/thermal conductivity ratio to me.... that plus some concrete board attached to the surface of the building behind whatever thermal conductor is used to add some thermal mass.

Intuitively, I would think that in a climate like mine (Binghamton NY) where we receive 50 something sunny days a year, the most important aspect of a system like this would be its thermal "agility" and not its thermal mass. In other words, it would be more important for this system to pump as much warm hot air as quickly as possible when it IS sunny out during the cold months. I am not expert though, and when I try this out I will give feedback, just as I'd expect from anyone here who experiments with something like this.

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