Solar collectors from soda cans - how to cut the cans?

[Stephen Tashiro]

I've been looking at passive solar collector designs on the web that use columns of soda cans as the collectors. Most videos show the cans have a large hole cut on each end. A few show a large hole cut at one end of the can. At the other end, a small hole is cut and then slits are cut radiating outward from the hole. The fins formed by these slits are bent to direct the air in a swirling pattern.

Are there empirical or engineering guidelines about which way of cutting the cans is best?

[Todd Carpenter]

Steven,

do you have picture of what the "cut" can looks like? We might be able to better help if we could see what you're trying to acheive...

Todd

[Stephen Tashiro]

How to build a soda can solar collector:
http://www.youtube.com/watch?v=QLNViUsRCVU

Unsuccessful experiment trying to see which can cutting pattern works best:
http://www.youtube.com/watch?v=JbcLLwtJu8s

(My question is what pattern to use. I think I can figure out the way to cut it.)

[phil harold]

Unsuccessful experiment trying to see which can cutting pattern works best:
http://www.youtube.com/watch?v=JbcLLwtJu8s

does this really work? that video showed that a plain cardboard box heated up just the same
make a classic TAP with an asorber plate

[Stephen Tashiro]

I've seen the video. The failed experiment was using lamps instead of the sun. He's also using a very small number of cans. As he said, the experiment is not conclusive.

Solar collector designs using stacks of aluminum cans are a very popular item for web articles. However, I have not found any engineering analysis of the collector. That leaves many design variations to consider.

Besides the question of how much airflow and how to direct the air, there are other questions. For example, I saw another video (by the author of the first link) that said he built a unit using aluminum downspouts with the cans stacked inside. I don't know why having the cans helped that design except to make the air flow more turbulent.

[M Toupin]

If you're serious about building one, you might look at this design.

http://www.green-trust.org/2000/solar/Homebuilt%20Collector%20Instructions.pdf

Mike
(http://www.green-trust.org/2000/solar/Homebuilt%20Collector%20Instructions.pdf)

[Todd Carpenter]

Hi Steven,

The idea is to get the air to slow down so it can be heated up, instead of cooling the aluminum, and or turbulate the air, so more of it is heated up. I doubt you'll find much about turbulating the air unless you want to get into aerodynamics - but most of that will probably be centered around getting a body to move as effortlessly as possible through the air. Having said that, there are some instances where turbulating the air has some aerodynamic advantages. You'll probably find more information from modellers than the full size guys so might try:

http://www.rcgroups.com/modeling-science-136/

and or

http://www.eng-tips.com/threadminder.cfm?pid=16

Good luck and let us know how you make out!