It is easily one of the simplest ways to harness the power of the sun. It’s uses range from teaching school kids the basics of how reflection works to pasturizing disease infested water in Africa. The basic principals of the design are concentrating sunlight, converting that light to heat, and trapping that heat. To concentrate the light you must use a reflective materil like polished metal or foil as lining. To turn that light into heat there should be some dark material like a pan or darkly colored cooking surface. To trap the heat you have created you must have a clear cover r the light to enter this changes the light waves so that they cannot exit.
The construction is simple and can be a fun project. All you need is a card board box, aluminum foil and a clear cover for the light to enter. First you need to line the box with the aluminum foil tacking it in place with either glue or other adhesive. Next there should be a clear cover of glass, plastic, or other clear heat resistant material that can be easily removed. Then here should be a darkly colored cooking surface to absorb the heat you are creating and cook you food.
Use of the basic Box cooker is very simple. There is no need to turn or adjust the cooking food, but occasionally the box should be adjusted to maintain its full exposure to the sun. The cooking time is longer than a conventionla oven but if prepared and started before midday you should be able to eat a meal by a regular dinner time. Seperate boxes are often used for larger meals to reduce cooking time.
Though they were invented in 1767 by a Swiss Naturalist named Horace de Saussure. They weren’t widely accepted until the 1970’s. There are many other designs like the Panel Cooker which inexpensive cookers that use mirrors to reflect the suns rays at a cooking pot or pan inside of a plastic bag. The most common model of this is the Cook-It developed in 1994 by Solar Cookers International. One cooker is often enough to cook a meal to feed a 4 or 5 person family. Another design is the Parabolic Cooker which is much harder to construct and and use. They can reach high temperatures and cook far more quickly but require frequent adjustment. Many of these exist, primarily in China.
The use of these cooker can greatly reduce your dependance on your conventional oven. The energy saved may not be as substantial as you would hope, but in the larger scale it could be amazing the positive impact they have.