I found this really cool how-to on a home heater made from cans and an old window. It could also be a solar dehydrator. I haven't done it yet, I just found it today, but it looks like a pretty good little project. I pasted the directions below or click the link for pictures
http://ecotechdaily.com/2009/07/01/free-heat-from-an-old-window-and-some-soda-cans/Free Heat From An Old Window And Some Soda Cans.
By David Quilty • Published July 1st, 2009 • Further Reading
Departments: Energy • Featured
Explore related topics: Energy • heat • reuse • Solar
This article was originally posted at my site The Good Human, but because it is “EcoTech” oriented, I figured it should probably be here as well. Enjoy!
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. Here is the picture that I posted on that day:
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…
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.

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!