Solar Space Heater Made From Soda Cans & An Old Window.


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Some of you may remember a post I wrote back on my birthday that offered a sneak peek of a top-secret project I have been working on in my garage, and asked you to guess what the picture might be. Well, the time has come to unveil more pictures of project timeline and all its finished glory, followed by some information as to how I made it, what its for, and what I will be doing with it now that it’s done. Let’s first take a look at a few pictures I took as I was building this solar space heater…

soda can solar heater

soda can solar heater

soda can solar heater

soda can solar heater

soda can solar heater

soda can solar heater

So, now can you guess how this thing works? As air enters the 2 holes on the sides near the bottom, the sun is heating up the soda cans all painted black to absorb the heat. The cans have holes drilled in the bottom, so the air being drawn in at the bottom works its way through all the heated cans and gets hotter and hotter as it approaches the top. With convection, more and more air is drawn in through the bottom and the heat rises. A single hole drilled in the top of the frame is where all this heat comes out, and I have to tell you – it’s friggin’ hot and it comes flying out of there at full speed. That’s the basics of how it works. But how was it made? Well, if you cannot see from the pictures, the ingredients include:

One old window frame w/glass intact
Empty soda or beer cans, spray painted black, with holes drilled in the bottom
Duct tape
A piece of insulation
Plywood for the back (I only have cardboard on it right now, so it’s not even sealed properly)
A dryer vent to hook to the top to direct the heat where you want it to go
Small screen to cover the 2 intake holes at the bottom

That’s it – it’s basically a free heater. However, now you may be asking how/where it could be used? Well, what I was initially going to use it for was to heat my garage during the winter, so I could work out there all day without freezing to death. My plan was to lean it up against the outside of the garage, right below a south-facing window, and let it collect the sun’s rays there. And then, I was going to build a custom window-shim out of a piece of wood that would let me prop open the window a bit but keep it sealed, and then cut a hole in the wood to attach the dryer vent to, which would bring the hot air into the garage. Kind of like this:

And finally, if I wanted to, I could mount a tiny fan to blow the heat further into the garage. But judging by the temperature reading coming off the air at the top, I might not even need to do that. It was up to over 105 degrees the other day around 11am. Amazing! And as I mentioned, it’s not even properly sealed yet.

But while that was my idea for it at my house, I think I might give this one away to someone who has trouble affording to heat their home during the winter, so at least they could have heat during the day. I have to do a few more tweaks, and finish the back, but other than that, it’s a solidly-built, indestructible free heat source that should go far to keep someone warm…during the day. Unfortunately, the moon just doesn’t shine bright enough to power it. 😉

So, what do you think? Did you guess correctly? Thinking of building one of your own for your workshop, garage, or even house? Let me know if I can help. It was quite a lot of work, but totally worth it in the end to know that I built a source of free heat that actually works!

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  1. This is terrific! I’ve seen a version of this on the Mother Earth webpage, but the cans make this even better. The dryer vent is an especially nice addition. Maybe if I start now I could have one ready for the first cool days of fall!

  2. Actually, it is “duct” tape – It can be called both, but the official term is, in-fact, “duct” tape, as the “duck” term, from WWII, isn’t verified. The labels on the tape call it “duct”. That being said, it is only there to hold them together for assembly anyway, so it doesn’t really matter.

    You could feed both, but that would require multiple lines/holes into the house, which I didn’t want to do. The goal was to make it as easy as possible for someone to use, especially since I am going to give it away.

  3. If you’re using standard duck (not duct) tape, it dries out. It would be useful for keeping things in place as you’re assembling the cans, but won’t work for the long term unless the frame and backing keep everything firmly in place.

    Is the air fed from outside? I can see where you could use the dryer duct to carry two lines, a feed and a return. That way the start temp is warmer than outside.

  4. exactly what i was looking for to make a solar clothes dryer (rather than a clothesline). just hook the output hose to where the heating element is on a gas dryer. you would still need to use power to run the motor and blower, unless you had a solar power set up for it. i’m gonna try it!

  5. I am curious how this will work in the winter. June 9th air is what?.. 80-90 degrees there for your heating air up 15-25 degrees. What happens when the air is 30-40 degrees? I have a feeling that it is harder to make cold air hotter then it is to make hot air hotter.

    1. Heating cold air in the winter works by the same principle as your car heating up in the winter with the windows rolled up. The concentration of heat through the use of dark tubes and window glass should heat up the air almost as quickly in winter as in summer.

  6. Great idea – I’m impressed with the low cost, simplicity, and efficiency. As far as heating goes, it takes the same solar energy to go from 10 degrees C to 20 degrees C (10 degree C rise) as it does to go from 30 degrees C to 40 degrees C (still a 10 degree C rise). However, there may be more ambient loss at lower temperatures with less than perfect insulation. You should be able to cascade 2 or 3 of these in series – each giving a 25 degree F rise and raise the outside 30 degree air to 105 degrees… Mike

  7. One other value for this device is that if you have another small space heater – elec, gas, etc, you could use this to preheat the air and the space heater would require less energy… MK

  8. I was thinking, what if you try and apply this idea to something else? My idea would be heating a pool but I’m trying to think of how to feed water through it and it insulating and carrying water to and from the pool.

  9. Wow! This rocks! I am manking a few of these. I wonder, how this can be used to stop water buckets from freezing in a barn?

    I hate dealing w’frozen water buckets. It is so hard on my hands. Don’t want to boil the water or burn the barn!

    Hmmm I shall ponder this! Thanks!

  10. Hi, I am really interested in trying this out. I would like to know if you have more specific, written out instructions. The pictures are great and I feel like I’ve gotten a lot from them, but I don’t feel quite comfortable actually attempting the build yet. Please let me know if you have those available as I plan on using my time this winter break to test one out in my shed.


  11. Hi Wow just reading this now wish I had read This sooner!! Can this be done now that its snowing outside??? I live in Rome Ny and need something to help heat the 14×70 foot mobile home I live in. I am currently unemployed our pellet stove,broke down we’ve been using electric heaters.I can’t afford anything right now not even to fix the stove.

  12. I’ve been looking for a way to heat my 16×16 studio. It’s a shed conversion and there’s no power so I can’t work when it’s dark or too cold. This looks like it will do the trick.

    I have a quick question. Will this work if the glass is frosted? I would imagine it won’t be as effective but I’m in the process of removing a tub with 2 sliding glass doors. That would let me create a HUGE heater. We get plenty of sun in NW Texas so that won’t be a problem.

  13. The room I’d like to heat only has west and north facing windows. If I use the west facing window, will I get similar results?

  14. Very cool. You could also use an insulated duct to preserve the temp coming out.

    Would opening up the entire top and bottom of the cans produce a stronger stream?

  15. south facing window. Since i live in New Zealand at the southern hemisphere would that mean a north facing window? Im going to the recyclers tomorow to get some can’s unfortunatly i couldnt find a used detached window. so im going to the store to buy some wood to make one.
    lets say i put it on a roof and hose the hot air down the window. would it flow?
    maybe i need to get a solar fan.

  16. Some ideas for future versions:
    Paint the glass black to create more surface area to collect the heat. The entire chamber would heat up and transfer the heat into the cans to be vented out. Also, align the cans sideways and connect them into one continuous tube like a car radiator
    This would give the air a chance to get even hotter on each return before exiting, speeding up as it creates even more convection. The downside is that it might whistle with the additional speed.:)

    1. Thanks Jason, but I probably won’t be building a new one anytime soon since I now live in an apartment in the middle of the city!

  17. Thanks so much for this! I live in a garage, and since I’m in college money is tight. I get Tons of sun from a south facing door that I can use for this.

  18. Very cool. You could also use an insulated duct to preserve the temp coming out.

    I hate dealing w”™frozen water buckets. It is so hard on my hands. Don”™t want to boil the water or burn the barn!

  19. This would give the air a chance to get even hotter on each return before exiting, speeding up as it creates even more convection

  20. One question Joe, does the insulation fit in behind the cans? Would styrofoam work for insulation, or does it have to be something else? Looking for alternatives to heating a cold room, and this is terrific. Thanks for any info.

  21. So interesting! As to alignment, would it work any better if the cans’ incoming (bottom) holes were bigger than the out/upgoing ones? But might take longer to get up to speed.

  22. Based on your initial results, do you think you could get a similar effect from half as many cans? My thought is that if you wanted this thing to run further into the evening (or between sunny times during the day), you could have every other row be cans filled with water instead of letting air through them. You’d get the same effect through the air rows (with maybe slightly less airflow overall), but you’d have some charge left over to keep it going after the sun goes down, or if it dips behind some clouds for an hour or two. Just a thought.

  23. How about feeding the heat into a thermal mass like stacked bricks or rocks and getting heat during the day as well as some residual warmth in the evening?

    1. You could, and someone else suggested water as a storage device. Unfortunately I no longer have the unit so I cannot test it out…

  24. I’m rubbish at science so wondered could you advise me.
    Could this be used to make an icebox colder….
    instead of heating it with the sun place it next to a huge block of ice.
    before electric fridges were invented people had iceboxes, they looked like a fridge with a cupboard for a block of ice. The ice only lasted a day and the inside wasnt as cold as modern day fridges.
    Meanwhile, these days campers manage to keep ice frozen for 8 days while camping. So I was thinking an improved Icebox-fridge could be made that would keep the ice frozen for a week, so would only need maintenance 1 per week instead of every day, and would also keep the inside colder.

    I was also wondering if one could make a home freezer-icebox. If you had a huge amount of ice, and filled it with already-frozen food, it should be possible to keep the food and ice frozen for a week.
    I’ve heard of people taking frozen meat in iceboxes with them when they went camping, and managing to keep it all frozen for 8 days. With massive amounts of insulation.
    Surely it would be possible to make a home version (that would look like a chest freezer)
    An old fashioned ice house in the garden could provide the ice.

    I was wondering if the popcan heater built into the icebox-fridge or icebox-freezer would help keep it cool.

  25. David, have you tried it again yet? I would really like to try this with my kids. This winter has been really cold and I could save some money. I would like to try it with my goats and chickens too.

  26. This is so incredibly creative! Having read a few of the comments it sounds as though your ingenuity is already helping people to stay warm, save money and of course, to reduce their carbon footprint as they do so. Great job! Thank so much for sharing the idea!

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