A Fuller Oven

I attended a Bay Area Linkup picnic where the founder demonstrated solar ovens. Due to the San Francisco-ness of the weather, there was a certain amount of overcast sun but once the clouds passed the oven was dramatically efficient.

There are plenty of solar ovens available now, but I thought about it and about the classic "Aristotle Death ray" and figured a variation of the two might be useful.

The design was basic and effective -- a few mirrored flaps. But it got me thinking. While there are parabolic ovens on the market with perfect redirection of light, if you were willing to compromise and use a faceted approach you could get a near-parabola without a lot of advanced technology.

This would be a tetrahedron based oven, much like an open half-soccer ball. While not absolutely necessary, an inset pentagram mirror would increase the "roundness" of the fuller oven. Without the pentagram, the whole thing could be manufactured out of identical triangular mirrors which would be ideal for mass production.

The model above uses Max's default teapot as the focus of the oven, but any iron pot would do.

One could also replace the oven with a solar collector to turn the device into a solar generator. For this purpose, an indefinite number of panels could be pointed towards the focus to increase energy output.

Note that while my design could be mistaken for a perfect tetrahedron, I think you'd have to flatten out the facets for optimal focus (I scaled the facets vertically by 50%.)

Practice meets Theory (guess who wins?)

So I actually tried doing this with acetate and styrofoam. I found that angling the mirrors into the center was much more problematic than I had supposed; also the amount of bend you need on the sides of the tetrahedrons was much less acute than I'd figured.

I want to take another crack at this soon. I think plain square sides will be as effective as tetrahedrons, if not more so. The added complexity really adds nothing to the effect. And ultimately a larger, flatter oven will have more effect than a compact design -- the goal is to capture the maximum amount of light. The original idea is fine if you're capturing raindrops but the real effect has more to do with how much energy you are gathering and that is a two-dimensional equation.