Parabolic reflective solar cookers are fairly easy to build: http://www.motherearthnews.com/diy/how-to-build-a-solar-cooker-zmaz74zhol http://www.motherearthne

Parabolic reflective solar cookers are fairly easy to build: http://www.motherearthnews.com/diy/how-to-build-a-solar-cooker-zmaz74zhol http://www.motherearthnews.com/diy/how-to-build-a-solar-cook... If you do some research, you'll find a ton more examples. When I was around 11 years old, as part of a "science project" I built a small solar cooker to cook hotdogs with. I built a linear parabolic reflector (so that the focus was a line, instead of a spot), and placed the hotdog on this line using a skewer (a straightened piece of coathanger wire). It worked rather well. The most efficient solar cookers, though, are solar ovens. As an adult, I've built ones using cardboard and tinfoil and cooked rice, beans, and made cornbread. You usually can't get them above 100 C (because of boiling and the vapor lowering the effective temperature inside), but if you can keep them properly oriented to the sun over hours, and keep the inner temp high enough, the oven can act as a very effective slow cooker for all kinds of food. The trick with either one (concentrator or oven) is making them portable (easier with a concentrator - but it is possible to do it with an oven, too - if you change the design a bit). Check out some of the DIY plans out there; you'll be surprised at what is possible.