The tremendous amount of heat that can be generated by bringing the light of the sun to a focal point through a lens is pretty amazing. Did you ever use a magnifying glass to burn ants when you were a kid? I can’t say that I ever did…but I did get to use one to burn leaves for a science class experiment. This same concept can be applied on a larger scale for a variety of practical purposes, including cooking food.
You can make your own Fresnel lens solar cooker with a lens from a rear-projection television. You can often find these TV’s for free or cheap on Craigslist or at garage sales. The television does not have to work, but the screen has to be intact to be able to use the lens. The lens will need to be mounted to some sort of frame with the rough side of the lens facing out. This is the side that collects and focuses the light to create heat.
As you can see in the videos below, the focal point of the light is pretty intense and the temperature gets very hot. By setting up your cooking surface near this focal point, you can easily generate enough heat to cook food.