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Thread: solar hot air panel.

  1. #21
    Gunco Good ole boy twa2471's Avatar
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    I've got a small emergency light battery and small solar panel and all I'd need is a charge controller to make it a totally self contained system. As far as the stuff in the plenum Back Again, it's just some scrap metal roofing painted black to pick up a little extra heat from that area. Just bent a 90 degree flange to mount it inside of each section of the plenum. Real simple.

    If you look close you'll see that 2 tubes go into each section of plenum and the air makes one continuous loop throughout the entire system making it a run of about 35+feet not counting the plenum areas.

    The only change I'd make next time, would be the single pane instead of multi pane glazing.

    The unit is inside TRX so no issue with heated air going back outside and the thermal switch only activates the fan when it reach's 125 degrees inside the collector, and shuts it off at 85 degrees.

    Now if we'd only get some sun,,we've only had 3-4 sunny days in the last month, so it's really hard to tell just what it will do at this point. But it did keep the house at 68 with the furnace off when it was 35-40 degrees outside,, that's promising. Every little bit helps.
    Last edited by twa2471; 11-13-2014 at 11:25 AM.

  2. #22
    Gunco Good ole boy twa2471's Avatar
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    I just thought I'd do a update on the solar panel now I've used it for a bit.

    It works GREAT!!!! When the sun is on it,,it pumps out from 85-125 degree heat @ about 3 minute intervals for around a minute, minute and a half at a time.

    I have had a issue finding a quite fan that puts out about 600-700 cfm that isn't noisy and at a reasonable price. There out there,but expensive.Right now I have a thermal couple switch inside the panel attached to a bilge blower outside the case. When that frigging thing comes on ,,it will make ya jump a country mile,,

    sounds like a God Damn V-1 rocket taking off next to you!!!!!
    needs a quieter fan,,,,Big Time,,,,,

    I don't know how to figure how many BTU's it puts out, but I've got just enough fire going in the wood stove to hold coals, and the furnace is off, and it's in the single digits outside today,,,and it's staying 68 degrees inside.

    I'll have to say this has proven to be a worth while project.

    I filled the oil tank for the first time in a little over a year(14 months), and it only took 158 gallons. And used a bit less than a pallet of those Bio-Bricks I'd mentioned and a cord of wood,,,all for 14 months of heat,,,Not Bad at all !!!!!

    So if you guys need some cheap and portable heat for a shop or something,,defiantly build one,,,it's well worth it!!! I'm glad I did. And this one is very small, so I can only imagine what a larger one would do, like a 4'X8' size.

  3. #23
    Gunco Member BackAgain's Avatar
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    Do you have to have a bright sunny day for this to make heat? Unfortunately we seem to have as many or more dreary days than sunny ones in the winter months.

    I am seriously contemplating making 2 of these. I have in mind a smaller one, 4x8 perhaps for my house, and a larger one or multiple smaller units to help heat my shop. In your opinion would a larger unit, say 8x8 or 8x16, or even larger be more efficient than multiple small units for heating my shop? The shop is divided into a 32 by 36 workshop and a 24 by 36 garage area.

  4. #24
    Always sore, always tired Bradrock's Avatar
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    Uh...68 degrees? Do you ever take your snowmobile suit off? Heh..Heh
    After living in South Florida for 20 years , we keep our house at LEAST 80 ! I like to lounge in my shorts .

    Let's see some pics please.
    When we lived down there, I moved our electric water heater outside into a little pavillion thing I built. Saved a ton on electric. Never saw anyone else do it. But it made more sense to me to have it out in the blazing sun ,rather than inside where your paying for A/C to cool down the water heater.
    In other words your paying to cool it down and heat it up at the same time.
    " Save a tree...........Eat A Beaver!"

    I seldom talk to liberals.............................. But when I do, I order fries............

  5. #25
    Gunco Good ole boy twa2471's Avatar
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    Back Again, I saw a plan for a larger panel that you build against a South facing with slots through the sheathing top and bottom so it naturally siphons heat without fans. And one similar but baffled and with a fan. They both were slick as Hell for a larger building that may not be that well insulated and both were very simple to build. If you have a good clear area for it I don't think you'd go wrong building a panel. On a bigger application your main cost would be the glazing, that's the most expensive part. You can get scrap glass to save bucks if you're lucky to find some big stuff , but you'll generally need more structure. A 4X8 plexi glass panel is kinda expensive but probably the best option best as I can figure. Light weight , easy to handle, transfers UV well and requires less structure to hold it up. We get only about half the days being sunny around here too, but when it is,,,that panel is really pumping out the heat!!!

    Bradrock, there's a few pictures of it under construction earlier in this thread, but I never did take one of it done,,what a slacker,,,,just add the solid back and a clear panel on front of those pictures and that's what it looks like. A white painted rectangular box, black on the inside, 8" deep and about 3'X5' with a 4" inlet and outlet on the back.

    I do like the down spout and baffle designs with a thermal switch controlled fan though, they seem to work the best overall from what little experimenting I've done with them. They put out heat for longer periods of time and more consistently. I'm sure if I used a smaller output fan, mine would run for longer periods of time instead of cycling quite so often. That would give me a bit more consistent heat,,at least I think it would anyways,,,I'm still experimenting with fans and learning. But my basic design seems to work pretty well. I just need to figure out just the right CFM to push through it to get the most heat output. Or find a nice quite variable speed fan at a reasonable cost.

  6. #26
    Gunco Member BackAgain's Avatar
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    Quote Originally Posted by twa2471 View Post
    Back Again, I saw a plan for a larger panel that you build against a South facing with slots through the sheathing top and bottom so it naturally siphons heat without fans. And one similar but baffled and with a fan. They both were slick as Hell for a larger building that may not be that well insulated and both were very simple to build. If you have a good clear area for it I don't think you'd go wrong building a panel. On a bigger application your main cost would be the glazing, that's the most expensive part. You can get scrap glass to save bucks if you're lucky to find some big stuff , but you'll generally need more structure. A 4X8 plexi glass panel is kinda expensive but probably the best option best as I can figure. Light weight , easy to handle, transfers UV well and requires less structure to hold it up. We get only about half the days being sunny around here too, but when it is,,,that panel is really pumping out the heat!!!
    Thanks for the response. I am serious thinking about doing this for my shop. There are 3 spaces along the wall roughly 8 feet wide by 14 feet tall. I guess the truth is the size would be contingent on what I could afford to build.

  7. #27
    Gunco Good ole boy twa2471's Avatar
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    That should give you some serious surface area and a decent amount of heat out of it, that's a big area.

    Check out the links Rochester put up before in this thread and you'll find the unit I was referring to. Those sites were where I did my initial research on panel construction. The one I was referring to is basically a 1X8 pine board box attached to the side of your building with a glass/plexi-glass cover. Remember though, A baffled design will give you more heat build up and better output. So consider that when building one. The further the air has to travel through the panel, the more heat you'll get out of it. A fan will be required then though, but in a shop a super quite fan won't be that much of an issue so fan cost won't be to bad, most anything will work. That's where the experimentation part comes in, getting the right amount of CFM and noise level from what ever fan you use.

  8. #28
    Gunco Veteran Frogman's Avatar
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    I just scanned your posts and though I might suggest for you to scavenge a heater fan and controls from a junked car. It all should be 12volts. A ( U -pull it ) junk yard should be cheap if it fits your needs.
    "The two enemies of the people are criminals and goverment, so let us tie the second down with the chains of the Constitution so that the second will not become the legal version of the first" ~ Thomas Jefferson

  9. #29
    Gunco Good ole boy twa2471's Avatar
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    The biggest issue with a automotive fan is,,physical size. You'd need the complete housing to make a complete fan assembly, the motor and blade are just half of it and won't do anything with out the housing. I'd prefer a self contained squirrel cage variable speed fan, but those are getting on the expensive side, a minimum of about 80 bucks from what I've found and that particular one would be marginal CFM wise, plus single speed, not variable speed. I've checked Grangers, and several other similar places like that but I can't seem to find just what I want for what I'm willing to pay. I don't want some 2' square ,,Afro Engineered, POS looking thing for the house.

    This projects main objective is to save money, if I have to spend a fortune on a fan to make it work well, it won't end up being all that cost effective. After all , as is now I've got at least $150 if you figure every single little thing it took to build it, ya you can use,,,some,,, scrap stuff,,,but at one point in time you had to buy it, so it may be scrap from one project, but I still paid for it at one time or the other,,so it's not free.

    Contractors or someone that works for one would do well building one sense they have access to scrap material that someone else paid for, but expect to dump a couple hundred into one otherwise by the time all is said and done. You can defiantly "Rube Goldburg" something for a shop application, where pretty don't matter much, but you don't want something for your house that looks like crap and my not be safe.

    Like I say, glazing and fans are the biggest expense in building one and thermal siphon ones aren't all that efficient. You'll double your output with a baffled one with a fan, so why consider anything else. Spend the bucks and do it right from the start and it pays off in the long run.

    Hell we'd spend $200 sending lead down range to pulverize a piece of paper without giving it a second thought,but to cheap to spend a couple hundred bucks to get "free heat" and NOT end up with something that looks like a failed second graders science experiment !!

    I guess I'm just fussy that way,,,

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