Solar cooking
Cooking needs temperatures of about 100--200 degree celsius. The radiation of the sun alone is not dense enough to produce such high temperatures, but if you concentrate the sun with a hollow mirror you can reach even higher temperatures. An alternative is a well insulated box with a double glazing cap and a flat mirror which reflects further light into the box - the light is trapped in the box and its energy increases the temperature inside it.
To prepare warm food a parabolic mirror is mounted on a rack and can be adjusted to collect the sun most efficiently. A cooking pot is fixed in the center of the focal area of the hollow mirror. A dull black coating on the outer side of the cooking pot absorbs the radiation with good performance and heats up the pot itself. The diameter of a typical solar cooker is about 1.3 metres and hence is able to concentrate about 800 Watts onto the cooking pot. The power can be compared to a small hotplate of a electrical hearth.
What is needed for solar cooking?
- The sun of a cloudless sky is necessary for efficient cooking
- A parabolic mirror of medium quality - polished aluminium is absolutely sufficient
- A simple mechanics to direct the parabolic mirror to the sun
- Independancy from wood - if wood from trees is no longer needed, desertification can be stopped in many regions.
- Independancy from fossile fuels - after the solar cooking device is payd no further costs will burden the users over several years.
- The devices are cheap, robust and can be maintained by the users itself.