The water pasteurization unit can be used for cooking as well. Cooking however requires higher temperatures and as a result the smaller units may have degraded performance. Also for water a vertical tube works well but for cooking a horizontal tube design works much better.
Food can be baked in a closed tube or fried in an open half tube. Frying again requires even higher temperatures. Food can also be placed on a stick and mounted at the focal line. This method however works better with darker food as more sunlight is absorbed. When cooking using this method burning the food is very easy because it will cook slowly unit it begins to darken and then will burn very quickly.
Using the vertical test unit I was able to bake a long baguette. A 2.36 inch outside diameter fence post tube was painted black and used as the oven. Cans were mounted on both ends to trap the hot air. The bread was placed on some aluminium foil and slide in the pipe when the pipe reached 165c. The bread was fully baked in less the 30 minutes in the sun.
Please have a look at the link below for the bread baking video.
Using the smaller cardboard unit (see Tutorial here) I was also able to cook noodles. The noodles require less heat to cook. They were cooked inside a large pop can. This is not recommended as I do not know if pop cans are food safe when heated. Please find the noodle cooking video at Cooking noodles Using Sunlight