I designed an easy way to make compound parabolic solar cookers. One that is appropriate technology, I made a dome from mud, and fold the material around the dome to make the correct shape. I made a compound parabolic dish because compound parabolic dishes can be left in the one spot for hours cooking happily away, and they do not produce a burning point of light. Parabolics on the other hand produce a burning point and they must be repointed at the sun often.
http://www.youtube.com/watch?v=9eY0xh23Anc
I wanted software to explain the concept but instead, i ended up using a strip of mylar, some drawings, some plastic ties 2 clamps and a laser level.
(Perhaps if you have thicker mylar you can dispence with the plastic ties).
It actually worked really well.
Take a look at http://www.youtube.com/watch?v=uX9Z-nsUHiA
You can find info about compound parabolics at
http://www.fossilfreedom.com/increase-output.html
and at
http://www.appropedia.org/Understanding_Solar_Concentrators
I would very much appreciate if someone else made one  or tried the mylar idea for modeling reflective surfaces. My solar cooker is good for 3 hours of cooking before moving. You could make a 2 hr or 1 hr or 4 hr solar cooker. It is important that others do it. I have some heating results (and they are good) but the cloudy rainy season begins soon. It would be a shame if these new techniques have to wait a long time to be put in widespread use.
Brian White
Brian White