Any suggestions would be welcome, I am trying to figure out if I can use 2 old thermal water heating panels and thermosiphon air through them to help warm my barn it may be a crazy idea but it might add a bit of heat, maybe? I also want to build a rocket mass heater in the barn as well and have Ernie and Erica's book, I just hate to see things not used if there is a way to use the panels without water it would be awesome any information I would welcome, thanks, Chas de Geofroy.
Most solar water heaters I have seen probably would not work well for circulating air due to the small inlets & outlets they use. Some of the flat panel designs could possibly be modified to allow greater unrestricted flow rates. If you have an evacuated tube design I would seriously consider salvaging those (very efficient & expensive) tubes to make another water heater. Water holds heat much better than air. If your concern is freezing water there are other liquids used that won't freeze.
Another concern is the thermosiphon phenomenon itself. Part of that requires gravity assistance & gravity won't help much with air. I feel that any heat gained could easily be lost in the process of moving the air back into the barn. Perhaps a small fan would help resolve that.
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You DEFINITELY can!!
You just use them to heat air instead of water. A random link, that may not be the best out there, about them 12 DIY solar heaters but it shows some of the different types.
Depending on exactly how your panels are made (LOVE to see a good pic, we could make better suggestions with more data) just consider the old piping to be thermal mass heat collector, vent from under the glass. So where they have cans or steel or whatever, you have old pipes.
Mine blows 165 degrees on good days for it :) I don't have a write up on it done, but it's a variant of those types in that link. I don't flow the air through closed space like a bunch of the can types do, mine uses the metal as a collector, and vents over it.
I tried the thermo siphon and it didn't work well for me. I don't think I had enough hight to get the thermo cycle going, so I use forced air to get it started. I am the local drop off your junk guy so i get lots of free things to work with. I used 2 free solar panel that were originally for a odd lots christmas light strands. I think they are about 2 watts added together. I put them in series to get 12v. I then wire them to a normally open 90 deg snap disc thermostat ($.90) that I purchased from eBay. I used a computer fan from an old processor. I mounted the snap disc inside the middle of the solar panel. When the sun shine the snap disc closes at 90 deg f and turns it on. If the sun is out the fan starts up.
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Christopher Shepherd: NICE!! I like it! I'll keep that one in mind!
Thanks for sharing that, and welcome to Permies!
Sounds like you have interesting thoughts to offer. Check out the upcycle and frugality forums, we like neat ideas :)
For those without the resources or ability I have seen these little solar fans that hang on your car window when parked for a bit of ventilation. Could probably adapt something like that to work too.
Chas de Geofroy
posted 2 weeks ago
Thanks all you have given me some great ideas, these panels look the one that Dave Burton had diagramed thanks. I will take some good pictures at some point at the moment they are buried behind a bunch of stuff next to the barn and I am trying to focus on getting my wood in for the next two Winters, thanks all, Chas.
Solar air heaters are the most diy friendly direct solar thermal tech. Mounted on a wall with the ports high and low should thermosyphon.
Usually they have opposed inlet and outlet, and flow along the length through baffles to agitate the air and scrub the collector of heat. A good pitch in either orientation should show some air movement. There is likely a chart for the size of collector and quantity amd there are rules of thumb. They want to produce a useful output temp at 10 to 20 degrees difference between inlet and outlet. That is the cfm and it changes with different configurations and could be constantly varied. A pv panel wired direct to the air mover can do just this but a thermosyphon and damper can also.
If the collectors are serpentine in air path through them (never saw this but they could be diy or an odd duckie), they will not thermosyphon on their own.
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