Solar Pop Can Heater Question...

I'm new here...

A couple days ago I discovered solar pop can heaters. Its fascinating! I thought solar heaters were huge things that you could only buy if you were going to spend $5,000-$10,000 or more.

I am definitely going to make some of these things. Some passive and a few large ones for active. I do have a few questions. I will post in different threads once I find the time.

For now, whats on my mind is... why is the entire collector black? As the air is moving through the pop cans (which are supposed to be sealed off completely). What we want is for this air that travels through the pop cans to heat up fast and efficiently. That said, I would think by having everything else black... you're heating up the walls of the collector as well as the insulation. Wouldn't it be better to have double glazing, 1-2" of insulation, and a high temp durable reflective film such as mirror film or mylar?? I know that can get expensive, but wouldn't the extra money be worth it?

Basically, what I'm thinking about doing is to paint the cans black before they are installed in the collector, and then have the entire inside of the collector lined with reflective foil. Therefore light shines in the box and is reflected onto the black pop cans. 

Please let me know if this will work, or why it won't.

Thanks!

Shawn

I honestly don't know if your idea will work better or not, but builder's foil would be cheaper and better able to stand the heat than aluminized mylar.  Before you start building though, do some more research.  There are a lot of other types of cheap solar heaters that, if nothing else, will look better than the can ones.

homesteadpaul wrote:
I honestly don't know if your idea will work better or not, but builder's foil would be cheaper and better able to stand the heat than aluminized mylar.   Before you start building though, do some more research.  There are a lot of other types of cheap solar heaters that, if nothing else, will look better than the can ones.

Interesting... I thought builders foil was not rated for high heat.

Anyhow, good point about other types of heaters. I've been thinking about that myself.

It seems to me like pop can heaters are not as great as people say they are. True, aluminium conducts heat very well. But it takes a lot of time to put hundreds of cans together. And it can take a long time to get a big enough collector to heat such a large house as we have.

I have (and am) doing my research. One thing I like about the pop can heater, is that pop cans are usually free. As soon as you start gluing fabrics together or buying lots and lots of down spouts, etc. etc... you start spending a lot of money. I need a system that is both efficient and not too costly.

Any help would be greatly appreciated.

There is a thread on here for pop can heaters.

You want everything inside the heater (that the light hits)  to be flat black. Reflective surfaces reflect light back out black surfaces turn photons into heat.

Passive is best if you are building or renovating a place and it can be done fairly easily. Active systems have a lot more problems that must be dealt with.

https://permies.com/bb/index.php?topic=6580.0

pop can solar thread

I remember doing some research on 'beer can' solar collector racing about 30 years ago at a university.  It was a great excuse to get a 'beer budget'      The end result was that beer cans cut in half were no more effective than putting long metal screws (painted black) on the collector (thin pin fin theory)...

so unless you've got some other reason besides trying to extract more heat out of collector... i'd forget trying cans.

Surface area and orientation, even reflectors... would be better.