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Old 08-17-09, 02:10 PM   #11
Daox
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Gary, have you come across any ways of using the hot air panels (inexpensive) combined with a method of increasing thermal mass? Something like using solar powered DC fans to duct air to blow over water barrels comes to my mind. What do you guys think?

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Old 08-18-09, 08:26 PM   #12
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Hi,
I have a thermosyhon air heating collector on my barn/shop. I like it a lot -- no fans or controls. The air exits vents near the top of the collector on the wall up close to the ceiling. This area runs quite hot when the collector is running -- the vent exit temperature runs up toward 120F with good flow. I have thought about placing some thermal mass in this area. Just as a test, I've put a gallon can up there filled with water, and it heats up well over the collection period. The challenge would be getting enough mass in place to be effective.
Perhaps a plastic lined trough filled with water and hung from the ceiling? (you did ask for all sorts of ideas
Or, maybe even pick up heat from this area with a car radiator as Nathan does in this scheme:
http://www.builditsolar.com/Projects...rageNathan.pdf
The radiator could transfer the heat to a water tank -- if the tank was centrally located in the garage, and not insulated, it could act like a big radiator?

This is the thermosyphon heater:
$350 Solar Heating Thermosyphon Collector
Its only about $3 per sqat -- less if you could use your free glazing.

I guess another approach would be to 1) insulate well, 2) add something like the large area thermosyphon collector (lots of collection area), 3) add distributed thermal mass throughout the garage -- water barrels, or anything with lots of mass, and 5) keep the air well mixed (maybe a slow, efficient ceiling fan or two). This would allow the excess of heat collected during the day to be absorbed by thermal mass (which should help prevent overheating), and the good insulation should allow the mass to carry over the heat to the next morning.

I'm sure you already know about the Solar Site Survey -- avoids those "how can I be such an idiot" moments that we all have
Solar Site Survey

Gary
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Old 01-21-10, 01:33 PM   #13
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Hello all
This is my first post


one idea i had for heating my own garage was to simply have abs pipe on the roof and circulate antifreeze through that and have it cycle into the garage and for thermal mass i was thinking of removing the rubble from my "illegal but all ready present garage pit" snaking piping throughout and filling it with sand. i dont know if this is practical or not but i look forward to any input

Mike
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Old 01-21-10, 02:08 PM   #14
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Hi Mike,
I think that in your climate, you would need glazing over the tubes to get worthwhile heat out of it in the winter.

Collectors normally have fins on the pipes so that the sun that falls between the pipes gets transferred over to the pipes by the fins -- otherwise, you don't get much benefit from the sun that falls between the pipes.

Once you glaze the collector, the ABS is not likely to stand up to the temperatures inside the collector. It might be OK when fluid is being circulated, but if the fluid circulation stops for any reason and the collector stagnates, the temperatures inside the collector will go very high -- to high for ABS.

Half inch copper tubing is probably the best choice. Here is one way to do the tubes, fins, and manifold:
Experimental Solar Collector Using Hybrid Copper/Aluminum Construction

I think the storage in the pit would be OK if you insulate the walls and floor of the pit. That is, you want the stored heat to go into the shop and not be lost down into the earth.

Not trying to discourage you -- its a very workable idea with the right materials and construction.

Gary
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Old 01-22-10, 11:02 PM   #15
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Quote:
Originally Posted by GaryGary View Post
Hi Mike,
I think that in your climate, you would need glazing over the tubes to get worthwhile heat out of it in the winter.

Collectors normally have fins on the pipes so that the sun that falls between the pipes gets transferred over to the pipes by the fins -- otherwise, you don't get much benefit from the sun that falls between the pipes.

Once you glaze the collector, the ABS is not likely to stand up to the temperatures inside the collector. It might be OK when fluid is being circulated, but if the fluid circulation stops for any reason and the collector stagnates, the temperatures inside the collector will go very high -- to high for ABS.

Half inch copper tubing is probably the best choice. Here is one way to do the tubes, fins, and manifold:
Experimental Solar Collector Using Hybrid Copper/Aluminum Construction

I think the storage in the pit would be OK if you insulate the walls and floor of the pit. That is, you want the stored heat to go into the shop and not be lost down into the earth.

Not trying to discourage you -- its a very workable idea with the right materials and construction.

Gary
Simple marine plywood painted black? (As opposed to ABS).

I was trying to think of a way to use some tempered glass I have acquired... I'm considering making a few small thermo siphon air-exchange heaters to show my Father how they work... Build a box over top of a box with a duct inside, then put the glass over the top box, and lay it at an angle. As the air in the top box heats up, it draws in cooler air through the bottom box, and creates a small solar oven effect.
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Old 01-31-10, 09:57 PM   #16
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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.

Cheers

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