Are there proven designs for building simple solar collectors? Although I find much information on the web about building such collectors, so many builders take pride in using scrap items in their designs that it's hard to tell whether an aspect of the design (such as drawing air through tubes of aluminum cans) is there because it recycles or whether it would be a good idea even if recycling were not the goal.
I'm willing to use new materials and worry mainly about the efficiency of the collector. I'd like to put some collectors on the roof of my storage building to supply a little heat in the winter. I don't want them to be hard to maintain. I don't expect them to work well enough to make the building habitable in winter. I only want to be a little more comfortable when I have to take things in and out - and, yes, I just want to fool around with building a solar collector for the heck of it.