Solar ovens are a great way to cook; they are efficient, clean and easy to use. In the hot summer the heat stays outside. They work well in the winter as long as the sun is shining. The ambient air temperature doesn’t seem to matter much, as long as the ovens are well insulated from the cold ground or snow and in bright sunlight.
The one in the picture on the right is an old metal box I found and lined with 2 inch foil covered styrofoam insulation and a sheet of plexiglass for a top cover. It works quite well. You will notice that in the picture the inside is lined with foil. Since then I have conducted temperature tests on various ovens and have discovered that painting only the inside black raises the cooking temperature by about 25 degrees. This only works on the box type and not on the reflector or parabolic types of ovens
Solar Cookers International has performed research to determine the most efficient cooking pots for use in solar ovens. The type they sell and recommend is shown in the picture to the right. It is the black porcelain covered pots with the white polka dots your grandmother used to use. Cast iron Dutch ovens can work well in solar ovens on cloudy days because of their mass; they maintain a more even heat, as the sun goes in and out behind the clouds.
As a rule of thumb double all your cooking times when using a solar oven. In the next few days there will be more posts on solar ovens showing different types of construction and recipes.