How Solar Cookers Work
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 cooker in the 1870’s that was used for many years by the French Foreign Legion.These solar cookers operated on the same principles as cookers of today. An insulated box is covered with a clear window allowing access to light. The light rays are absorbed by the cooker’s inside surface and are transformed into heat energy. Heat radiates out from the surface and collects inside the cooker. Some of it escapes back through the window or “cracks” in the cooker, but not as quickly as additional light enters.
This process is similar to the greenhouse effect heard about so often in the news today. On a global scale, sunlight is absorbed by the earth and is transformed to heat. The heat radiates into the atmosphere. It either escapes or is reflected back toward earth by carbon dioxide and water vapor in the air. More carbon dioxide in the air means that heat is more likely to build-up around the planet.
Unlike the earth, solar cookers are deliberately designed to keep hot air inside. The cooking area is well insulated and the opening is often surrounded by rubber to seal it when the window is closed.
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 cooker are the reflectors. Reflectors help control the temperature by concentrating the sun’s rays onto the cooking area. Temperatures can also be adjusted by repositioning a solar cooker in relation to the sun. If lower temperatures are needed, the cooker can merely be pointed a bit away from the sun’s direct rays.
