Solar powered cookers have been with us for a great number of years, the first recorded on being made by a Swiss scientist in 1767, but they have only recently been manufactured in numbers. There are essentially three types of solar cooker, all of which work on the same basic principle - the concentration of the Sun's energy by reflecting it from a large to a small area. The solar cooker is probably the most basic way of harnessing the Sun's power for our own use.
The first kind of cooker I will talk about is the box cooker. This can be made very easily from two or three cardboard boxes, some aluminum foil and a little ingenuity. A smaller of two boxes is painted black on the inside and placed inside a larger box, the space between the two boxes being filled with insulation material - this can be pieces of another box cut up and placed between the two. Attached to the open end of the inner box are three or four trapezium shaped pieces of cardboard covered on the inside with aluminum foil - these are glued together in the shape of a funnel. Finally you need to place a piece of glass over the open end of the inner box. Point the whole box directly at the Sun and place whatever you need to be cooked inside jars in the inner box, which can soon reach temperatures of 200º or more.
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The second cooker is called a panel cooker. This is similar in construction to the box cooker except that there is no box. Heat from the Sun is reflected directly on to whatever is to be cooked, which is in a separate container made out of glass or plastic. The third kind of solar cooker is the parabolic cooker - rather than having flat reflective walls this has a parabolic mirror, which directs the Sun's rays directly onto the bottom of the cooking vessel. A small pot of water can be brought up to boiling point in about ten to fifteen minutes using one of these cookers.
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The solar cooker is becoming more and more popular in rural Africa where there is plenty of sunshine and where, previously, the now much depleted indigenous wood was used. Solar ovens behave in a much similar way to the slow cook and take a much longer time to cook food than a normal oven.
