DIY Solar Air Heating Panel w/pics!

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Blackthorn-USA
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DIY Solar Air Heating Panel w/pics!

Post by Blackthorn-USA » Thu Mar 21, 2013 3:35 pm

Shamelessly reposted from the original post on another forum in 2010.

Need some free heat? A break from your expensive utility bills? Here's my suggestion.

A Solar Air Heating Panel

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This panel is 2’x5’6’’ It is 5.5” deep tapering to 3.5” on the sides. The polycarbonate sheet salvaged from an old tanning bed is the only reason a flat sheet wasn’t used. You could use glass, plexi or polycarbonate. The fan is from a computer power supply. The rest of the materials are new.

I bought some guttering downspout, two 1x4x6, one 1x6x8, one 4x8 sheet luan, 2 – 4” duct taps and some black caulking at Home Depot. I got 3 cans of high heat black paint, a quart of roll on primer and a cooking thermometer at WallyWorld. Got the 12v 7ah battery, the 12v solar panel and the fan thermostat online. I had various screws an such on hand.

Gather your material and find a nice place to work. Like this gravel parking lot

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I routered the edges, it is not required.

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Using a skill saw and guide I cut a channel for the polycarbonate to slide into down what would become the sides of the panel.

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I then cut my sides and end to length and assembled the panel frame around the poly sheet.

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Once I had the inside dimensions of the panel I cut my spacers for the collector tubes. I used a jigsaw to cut the openings and sanded them to the same dimensions. Also drilled 2, ½ holes on each side to allow enough air flow to eliminate any possible condensation in the panel.

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I cut my downspouts into 52” long pieces. I then used two pieces to test fit the spacers into the panel to make sure everything would be square.

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It looked good so I cut and added the luan back to the panel frame. I also cut in the intake and exhaust holes for the panel and installed the 4” duct taps.

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Then using a step bit I put a 1” hole in the bottom of 55 pepsi cans. You have to make sure your cans are completely dry and shake out all the aluminum shavings after drilling. Easy to do, and it won’t rattle during use.

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And then stuff the cans into the pieces of downspout. This is to create a heat exchanger of sorts. The aluminum downspout and cans collect the solar energy and transfer it to the air passing through and around the cans.

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I then assembled the collector tubes and spacers and caulked them into place.

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I drilled the hole for the thermostat at the top of the center tube and everything got a coat of primer and a couple coats of black high heat paint.

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Once the paint was dry I added an adjustable fan thermostat. This is a close on rise stat. It turns the fan on at 110 degrees and off at 90 degrees. The fan is brushless, very quiet and rated at 106 cfm, this goes in front of the upper hole blowing out of the panel. I installed the battery in the bottom and connected it to the stat and fan. I also drilled a hole and installed a probe thermometer in the top side of the panel.

I intend to add a 12v PV panel to charge the battery as soon as Fed Ex brings it to me. This will allow the battery to be charged anytime the panel is in operation and the panel will be completely self contained.

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I touched up the painted surfaces and once it was dry I put the poly panel on and set the solar air heating panel in the sun.

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Today, Nov 3, 2010 here in KS it is mostly sunny, windy, and the ambient air temp was 57 degrees. This is the thermometer behind the bottom of the panel where the intake air would be drawn from.

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It took just over five minutes for the panel temperature to rise enough to activate the thermostat at 111 degrees and turn the fan on. At 30 minutes the temperature had been stable for a few minutes and I didn’t think it was going to rise any more. It stabilized at 148!

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The panel was creating a 91 degree temperature rise and blowing 148 degree air out at 106 cfm. This would allow a complete cycle of the air in a 12’ x 12’ room in less than 10 minutes.

A solar air heating panel will definitely supplement your daytime heating and reduce your utility bills. Further testing is needed, but I suspect it would heat a small shed or hunting cabin by itself. If you have a south facing wall, you can use these.

My total cost with this panel was about $130.00

Easy project!



Panel Addition Update

Mother Earth News articles have talked bout passive thermosyphon style systems, the same as commonly seen zig-zag air heaters on Youtube would be. They will allow heated air to rise into your structure as it is warmed. My panel forces the air with a fan so the output is considerably greater.

As far as nighttime usage goes... it doesn’t. This panel is designed for supplementary daytime heating only. Any heat it produces in the daytime is heat your furnace doesn’t have to create. There is very little heat retention in the unit itself once the sun is gone.

The way the panel is designed it only needs two 4 ½ holes cut into the structure. All other wall insulation remains in place. I want to keep it simple for the average homeowner with common tools to be able to install the panels easily. This is also the reason it doesn’t have oil or piping or other external components. The liquid systems could be made pretty easily too though.

The intake air will have a louvered vent on it to keep cool night air from back-flowing into the structure. I haven’t tested the unit in a structure yet, but for $4, I’m gonna add the louvers. The output air won’t need one as the air at that elevation will always be warmer.

I hadn’t thought about the density of the cool air versus warm air. I may experiment with that later. The fan is rated for temps well above the panel operating temperature so that shouldn’t be a concern.


Ok, here’s everything together except the battery cover and intake louver. The test conditions today were almost identical to above. 60 in and 148ish out. I let it run for about 4 hours. The PV panel produces 22v in direct sun, will run the fan by itself, but stops immediately if shaded. I am going to keep the battery in the system to allow usage on partly cloudy days. The PV panel will charge the battery.


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Updated Performance Testing

Weekend before last, 01.01.11, I got the panel out to do some cold(er) weather testing. Air temp was 22 degrees. The panel took about 8 minutes to warm up to 110 degrees and kick on. After 15 minutes it had stabilized at 128 degrees and ran there for 45 minutes or so until I removed it from the sun. It cooled and shut off after about 12 minutes in the shade.

So, it took about 3 minutes longer to reach cut on temp, maintained 128 degree operating temp and cooled about 5 minutes faster once removed from the sun.
The panel actually heats the cold (dryer) air better than warmer air. At air temp 57 degrees it was increasing the temp 91 degrees. At air temp 22 degrees it was increasing the temp 106 degrees. I’m not sure when you would reach the point of diminishing return and see no further panel temperature increase in relation to the air temperature decrease.

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Nice and easy panels to make. These will definitely help to reduce my heating costs in a few structures. Just imagine, a warm outhouse at hunting camp :D
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Blaik
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Re: DIY Solar Air Heating Panel w/pics!

Post by Blaik » Wed Apr 03, 2013 11:31 pm

This is VERY very cool. Thanks for putting it up!

williaty
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Re: DIY Solar Air Heating Panel w/pics!

Post by williaty » Sun Apr 21, 2013 2:18 am

Why are the soda cans necessary? The downspout tubing would conduct the heat to the air. What do the cans add? I feel like I have to be missing something obvious because otherwise they're just restricting airflow.

Definitely an idea I'm interested in.

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Re: DIY Solar Air Heating Panel w/pics!

Post by Blackthorn-USA » Sun Apr 21, 2013 2:30 am

The soda cans do restrict the airflow, allowing the air to be heated longer. They also add a small degree of thermal mass, but mostly to keep the air from just blowing through without being warmed.

Most pop can heaters actually use the cans as the collector tubes. My design adds the downspout material for extra thermal mass, to reduce the time and materials required to glue the cans together and I think they just look nicer. They're pretty easy to put together, and work very well. Give it a go.
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Re: DIY Solar Air Heating Panel w/pics!

Post by williaty » Sun Apr 21, 2013 3:17 am

Aaaah... cool. Or hot, I guess. :lol:

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Re: DIY Solar Air Heating Panel w/pics!

Post by HaroldBell » Wed Nov 06, 2013 3:50 am

Blackthorn-USA wrote:The soda cans do restrict the airflow, allowing the air to be heated longer. They also add a small degree of thermal mass, but mostly to keep the air from just blowing through without being warmed.

Most pop can heaters actually use the cans as the collector tubes. My design adds the downspout material for extra
solar panels, to reduce the time and materials required to glue the cans together and I think they just look nicer. They're pretty easy to put together, and work very well. Give it a go.
Just awesome thread..Everything is mentioned in detail so now I can built one following the instructions.. Glad to find such useful thread
Last edited by HaroldBell on Thu Nov 07, 2013 11:49 am, edited 1 time in total.

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Re: DIY Solar Air Heating Panel w/pics!

Post by Trekker Outdoors » Wed Nov 06, 2013 2:58 pm

This is a neat idea! I may use this for my shed.

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Re: DIY Solar Air Heating Panel w/pics!

Post by Blackthorn-USA » Wed Nov 06, 2013 3:47 pm

Harold, I'm fixing to build a couple more this fall. Good luck with yours and if you have any questions post 'em up and I'll try an answer them for ya!

Trekker, We want to put a small one on the side of the Little House up at the school too. Keep your butt from freezing :mrgreen:
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Re: DIY Solar Air Heating Panel w/pics!

Post by OrvilleMartin » Wed Jan 22, 2014 1:39 am

Awesome stuff.. Such detailed informative post.. You have mentioned each step with pics which will make it easy for me to get these panels very soon.

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Re: DIY Solar Air Heating Panel w/pics!

Post by makings06 » Wed Feb 05, 2014 7:32 pm

Awesome post! I shared this with a guy at work that is building a deer blind out of wood and was looking for a way to heat it. I would be interested to see if lining your box with mylar behind the down spots would help or hurt? I may have to try this.

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Re: DIY Solar Air Heating Panel w/pics!

Post by Blackthorn-USA » Wed Feb 05, 2014 9:40 pm

Orville, hope it works out for ya! Post up some pics of your efforts!

makings06, would work well on a blind, particulrly if mounted on a sloping roof where deer weren't likely to see their reflections. No smell in operation to scare them away. Not sure if lining the box with mylar would work. The back soaks up alot of heat, mylar of course would reflect it. I don't know if that would help or not. I'm leaning towards not, but give it a shot and let us know.
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Re: DIY Solar Air Heating Panel w/pics!

Post by williaty » Wed Feb 05, 2014 10:18 pm

I don't have time to find the link right now (I'm in between bouts of working on the snow in the driveway), but getting the notification email for this thread reminded me to post that there's a forum/group hosted on Yahoo Groups that's all about just building these types of solar heaters. They have a design using window screen that supposedly dramatically outperforms the pop-can/downspout style shown here. If you're thinking of building one, it's worth a googling.

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Re: DIY Solar Air Heating Panel w/pics!

Post by SouthernGentleman » Sun Nov 02, 2014 8:14 pm

If you want an easier way to build the box with the glass door, it just turns out Lowes, Home Depot and all those guys sells a simple prehung exterior full view double pained exit door. More space for more collectors, the box is already in tack except for a bottom and some insulation around the incise. Get one with NO holes in the door or plug it.

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Re: DIY Solar Air Heating Panel w/pics!

Post by Blackthorn-USA » Sun Nov 02, 2014 11:47 pm

Thanks for the tip! I'll look into that on my next build.
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Fan location on Solar Furnace

Post by Trumpetman1 » Wed Nov 19, 2014 10:28 pm

Wouldn't it be better to "push" cool air in, rather than "pulling" hot air out over the fan? Wouldn't the heat promote premature fan failure?

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Re: Fan location on Solar Furnace

Post by Blackthorn-USA » Thu Nov 20, 2014 5:41 pm

Trumpetman1 wrote:Wouldn't it be better to "push" cool air in, rather than "pulling" hot air out over the fan? Wouldn't the heat promote premature fan failure?
You may have a good point but I have no experience with bottom mounting the fans. The fans themselves are designed to be used in computers and seem to stand up to heat well in the ones I've used. I can't think of a reason not to push the air into the heater though so give it a shot and let us know how it works out for you. We're all here to learn!
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Re: DIY Solar Air Heating Panel w/pics!

Post by Trumpetman1 » Thu Dec 18, 2014 12:13 am

Just as an FYI on my question about fan position.. intake or outflow..I talked with a small fan rep for Mechatronics. We were working on a solar furnace design, trying to match cfm power to the amount of heat chambers we had. Anyway, he suggested that pushing return air in or actually pulling it in through the intake port would tend to give the fan longevity because it would be running in a cooler environment. We've been able to see as much as 170 degrees on the output side, enough heat to start to degrade ordinary styrofoam. Having said that, we've decided on a "pusher" design, rather than a "puller." Also we determine that your 100 cfm +- fan was probably just about right for your system. We tested fans from about 60cfm to 180cfm. The former doesn't push quite enough air, and the latter creates so much airflow that the air in the chambers doesn't get quite enough heating time. of course adding more pipe with a larger collection surface would compensate. Good work though, and thanks for posting. Finding that tanning bed polycarbonate for your furnace was a bonus.

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Re: DIY Solar Air Heating Panel w/pics!

Post by Blackthorn-USA » Sat Dec 27, 2014 4:01 pm

Appreciate the update. Sounds like you guys are making progress. Also sounds like you're putting more R&D into yours, lol. I just guessed on the cfm but it's good to hear that it was about right. Keep us posted on your efforts!
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