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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.
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