According to solarcooking.org:
Solar cooking is the simplest, safest, most convenient way to cook food without consuming fuels or heating up the kitchen. Many people choose to solar cook for these reasons. But for hundreds of millions of people around the world who cook over fires fueled by wood or dung, and who walk for miles to collect wood or spend much of their meager incomes on fuel, solar cooking is more than a choice — it is a blessing. For millions of people who lack access to safe drinking water and become sick or die each year from preventable waterborne illnesses, solar water pasteurization is a life-saving skill. The World Health Organization reports that in 23 countries 10% of deaths are due to just two environmental risk factors: unsafe water, including poor sanitation and hygiene; and indoor air pollution due to solid fuel use for cooking.
My design is different than any of these and relies on the availabilty of satellite television dishes. In San Francisco, I often see Direct TV and Primestar parabolic dishes being thrown away -- not the receiver mind you -- just the metal dish. I then rubber cement aluminized mylar to the dish. These are amazing. They can get a pint of water to 160 degrees F in about 20 minutes and boil a like amount of water in about 30 minutes.
Fun last March. Could get up to about 320 degrees, but not all the way to popping corn. Grrr.
I was at the Exploratorium in April 2011, burnng wood with my giant Fresnel. I also brought this parabolic mirror which I forgot about. After a while the rope broke, having been melted by the hot spot from the mirror. Oops.