A solar oven is an appliance that enables a cook to heat food using only the power of the sun. Developed in the 18th century, it has, since the 1950s, become a high-functioning modern appliance.
History
Though people have always warmed food on rocks made hot by the sun, Horase de Saussure, a Swiss naturalist, is credited with building the first known solar oven in 1767. The 19th century saw a few primitive solar cookers, but modern solar cookers did not come on the scene until the 1950s. According to "Heaven's Flame: A Guide to Solar Cookers" by Joe Radabaugh, among the things that spurred the growth of solar cooking were ecological concerns emerging in the 1950s. Solar cooking also gained recognition on the coattails of solar power. In 1954, Bell Labs developed silicon-based semiconductors, and the solar power industry was born. Since then, solar energy of all kinds has been part of sustainable technology.
Function
All solar ovens operate in similar ways. Depending on the type, a solar oven might collect sunlight from a wide area and concentrate the resulting heat into a small area. For example, if you place a piece of food on rock in the sun, it may get warm, but it won't cook. But if you take a large magnifying glass and use it to focus the light of the sun to a point on the surface of the food, that point will cook or maybe even burn. The second method involves trapping the heat, creating a greenhouse effect much like that created in car on a hot day.
Types
Solar ovens fall into four main categories: Box cookers, parabolic cookers, lens cooker and indirect cookers. The box cooker is based on the greenhouse effect. Light is channeled into a cooking box using reflectors and is kept there by insulation and a glass or plastic lid. Parabolic cookers, which look like satellite dishes, use light collection to generate heat. Because they collect using a large dish and focus to a small pot, parabolic cookers heat rapidly. Lens cookers use lenses to gather light and put it on a cooking pot. The most commonly used lens is the frenel lens, which can be easily mounted on a frame for quick adjustment to account for the sun's position. Indirect cookers collect the sunlight and use it to heat water, oil or some other liquid. This liquid then heats the cooking box.
Efficiency
With good insulation and reflectors channeling additional sunlight into the box, temperatures inside a solar oven can reach levels comparable to those of a standard gas or electric oven. Bill Becker, on his "Making A Solar Oven" website, records temperatures in his solar box oven as high as 462 degrees Fahrenheit.
Significance
One of the most important uses of solar ovens is in regions affected by deforestation and desert expansion. According to the United Nations Food and Agriculture Organization, at least 2.4 billion of the world's people do not have adequate cooking fuels. Solar ovens can cut the time that people, usually women and children, spend searching for firewood. They can cook meals and pasteurize water without having to contribute to further deforestation. Solar ovens also reduce the amount of smoke from wood fires in homes.
Benefits
Solar cooking gives off no greenhouse gas emissions and uses no fuel. Cooking is done outside, so it does not heat the house in the summer. Basic solar ovens can cost as little as a dollar or less when made from recycled materials. In addition, the slow, lower-temperature cooking they generally involve can help preserve the nutrients in food.
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