In 1764, French inventor Horace de Saussure produced temperatures of 225 degrees Fahrenheit in glass-covered boxes lined with black cork. Another Frenchman, Augustin Muchot, designed a solar oven in the 1870s that was used for many years by the French Foreign Legion. These solar ovens operated on the same principles as solar cookers of today. An insulated box is covered with a clear window allowing access to light. The light rays are absorbed by the oven's inside surface and are transformed into heat energy.
Heat radiates out from the surface and collects inside the cooker.
These simple cookers also encompass a collector, storage and controls. The collector is a glass or heat-resistant plastic cover that lets sunlight inside. Storage occurs because insulation prevents heat from escaping. Storage is also provided by the food itself, which absorbs heat. Controls for a solar oven are the reflectors.