We’re finally cooling off after a brutal Summer here in St. Louis. While I’m thoroughly enjoying the temperatures in the 60s and 70s, they’re a good reminder that Winter will be here soon, and that we’ll be paying to heat the home.
That got me thinking about a concept I first encountered a couple of years ago: the soda can solar heater. Very similar in design to Gary Reysa’s thermosiphon air collector, this concept uses aluminum cans to build columns that collect and transfer heat from the sun. While I’ve come across a number of variations on the concept, most tinkerers who’ve tried this project point to Rich Allen’s video walk-through of building one of these heaters as their starting point.
Rich has played with his own approach; a later video shares his “final thoughts” on building one of these solar air heaters after making a number of them. Some other directions (or partial directions) I’ve found:
- Dan Strohl’s plans; his updates of his approach were featured on MAKE and lifehacker.
- Instructable’s member falling_stone shared his plans on the DIY site – this is the best step-by-step instructions I’ve seen.
- Blogging buddy David Quilty made one of these a few years ago, and took lots of pictures.
- Permies member Jocelyn Campbell points to this video of a Canandian man who may have first invented this concept:
I probably won’t try this myself; I can’t imagine trying to install this on my brick home. But I’d love to hear from those of you who have tried projects like these. I’m guessing it would function much like a solar water heater in the sense that it doesn’t necessarily provide all the hot air you need/want, but keeps the main furnace system from working nearly as hard as normal.
Image credit: westbywest via photo pin cc
I’m looking into the idea of biulding one of these pop can solar air heaters but I have a few issues to address. Firstly, as i live in the UK we don’t always get clear, sun filled winter days. On the days where we do it is usually warm enough not to need something like this. So now comes my main question.
I have 2 night storage heater in my house (the ones that take in cheaper night time electricity and heat is stored in heat bricks inside the heater). I was wondering if anyone has any views on whether this solar air heater could be used to heat these heat bricks during the daytime (i.e. the hot air passing over these bricks) so the heat could be stored and used during the evening and night time the same as a convential night storage heater. I have dimplex CXL 18N heaters.
Naturally, you can heat these bricks with the solar air collector but there are some issues worth considering:
– The internal structure of the storage heaters may not give themselves for tunneling the air through them.
– Solar-air collectors need fairly strong fans to operate at peak efficiency (you should minimize the air temperature increase in the collector to 10 degrees). Strong fans may introduce unwanted noise into your house so you need to carefully design the piping to kill the noise before it reaches the living area. This is doable if the air collector is on the roof and appropriate piping can be used to dampen/kill the noise. This is not really doable with wall-mounted solar air collectors (the piping is way to short).
– Solar air collectors are most efficient if they can heat the rooms directly (this way their input air can stay around 22-25C (the temp of your room). For heating the bricks, you would need to use much higher temps which will reduce efficiency.
All in all, I advise against the storage system. I recommend a direct room heating design.
Thanks guys for all your tips and comments. Lots of things to think about. At the moment i’m thinking about making a simple soda can heater which i plan to mount in my kitchen window which gets the sun first thing in the morning (but that side of the house is generally the coldest). Hopefully learn how to do it on a smaller scale before maybe tackling something a bit bigger next year.
The problem with putting the thermal mass inside the collector is that once the sun goes off the collector, a good deal of the heat stored in the collector mass is just lost out the collector glazing. I think its better to keep the thermal mass of the collector low so that it heats up to temperature quickly, and starts delivering heat to the house as soon as the sun comes onto it.
I think you might be better off to route the hot air from the collector exit vent over the thermal mass inside the building. The more of the brick surface are you can expose to the collector hot air, the more of the heat that will be transferred to the bricks — that is, you might want to stack the bricks in such a way that the air can get to more of each brick’s surface.
Two of us did some testing on several types of DIY solar air heating collectors and found that a collector that used two layers of ordinary metal window insect screen as the absorber preformed the best of all the designs we tested. The designs included a traditional backpass collector, a ventilated soffit absorber collector, an empty black box, and a collector made with aluminium downspouts (somewhat similar to a pop can collector).
The nice thing about the screen absorber collector is that its just a breeze to build — it can be built in an afternoon.
These are the tests and results: http://www.builditsolar.com/Experimental/AirColTesting/Index.htm
This testing was done independently by two of us, and we got results that agreed quite well.
Thanks so much for coming by and chiming in, Gary! I’m off to check that one out…
Hey Jeff — you are most welcome. I’d like to heat what you think after taking a look.
Would a solar heater work in the winter? Wouldn’t the freezing air/snow/ice cool the cans down, despite any heat from the sun?
I’m sure it would, Mike, but there’s still heat there. The black paint helps collection of that heat, and the system (as I understand it) is designed to move it so it doesn’t get lost. With all of that said, I’m not a physicist… I’d love to hear a better explanation.
I am presently building a pop can heater out of Heinekin beer keg cans I spray painted black, 6 in a row caulked together. There would be 6 rows. I want to also put a small electrical heater ( one that uses lower voltage) that would operate at night off of an off grid system at the bottom of the solar heater. This would heat the cans at night after sunset.. I want to see the difference between smaller cans and bigger heinekin cans for air flow and quality and if the small heater can keep the solar heater warm at night. I am just curious about this. It would be interesting to have a pop can heater that could operate all day and night.
Keep us posted on what you find out, craig…
I would like to ask that i am doing some innovation to make solar heater box for killing the store grain pests specially rice in Malaysia. When i read your blogs i am really happy that some ideas and hints i got from you, kindly guide me further that it could be ideal for store grain pests in small, medium and at large level.
is it posible to neutralise heat from the soda can solar heaters in the summer if they are instaled permanantly because they will be on a South wall and getting very hot in summer if you have coments please give me your anser im sure im not the only one asking this question tank you jack
Hmmm… I suppose some kind of covering (probably light colored) would work.