Thermal cooking is not a new idea. In fact, “Gone With the Wind” author Margaret Mitchell wrote an entire book about the topic about a 100 years ago called “The Fireless Cook Book.” This is because the South was very poor after the Civil War and needed cheap and economical ways to survive.
In essence, thermal cooking involves heating up something that will stay hot a very long time, like a big soap stone or cement disk. These objects could be heated in a stove or a fire and then used for cooking other things. This could be a way of saving energy if you are using a generator or if power is scarce or if you are in a position where you do not want anyone to see that you have a fire burning furlong. The disk is heated up and topped with an insulated box. The box is then placed on the disk so that baking can be done.
One type of thermal cooker is called a haybox. This method of retained-heat cooking refers to a kind of insulated container that fits snugly around a pot. Hayboxes are made of anything that insulates the cooking process and that includes hay, straw, wool, cotton, feathers, rice hulls, aluminum foil, fur, fiberglass, rigid foam and rice hulls. You can actually buy commercial hayboxes but some people have created them by wrapping the pot on a heated stone with pillows, blankets or a sleeping bag. These slow down the movement of air that can cool down food.
Mylar hayboxes are a good idea because they are safer and actually reflect the heat radiating out of the pot back towards the pot.
It is also important to note that water is not lost from cooking foods the same way it is with normal cooking. Often the water normally added to the pot is reduced by a cup or a half cup.
This way of cooking is also handing because it is less dependent on timing. The food will stay hot for hours. Food does not tend to burn because food does not tend to boil and burn on the bottom of the pot.
Hayboxes can help you conserve a lot of water and energy in general and they are easy to build and easy to use. They are ideal for serving large groups of people because they keep food warm for a long time.