A solar cooker is a device which uses sunlight as its energy source. They use no fuel and they cost nothing to run and their use is helping to slow deforestation and desertification, caused by using wood as fuel for cooking. Solar cookers are also sometimes used in outdoor cooking, especially in situations where minimum fuel consumption or fire risk are considered important.
Solar box cookers can be made of locally available materials or be manufactured in a factory for sale. They range from small cardboard devices, suitable for cooking a single meal when the sun is shining, to wood and glass boxes built into the sunny side of a house. Although invented by Horace de Saussure, a Swiss naturalist, as early as 1767, solar box cookers have only gained popularity since the 1970s. These surprisingly simple and useful appliances are seen in growing numbers in almost every country of the world.
Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)
For More Information: Build Your Own Solar Cooker