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< prev - next > Energy Stoves and Ovens KnO 100167_Solar cooking (Printable PDF)
Solar Cooking and Health
Practical Action
What are the problems associated with solar cooking?
With some cookers, even though tough, tempered glass is usually used, there is the possibility of
breakage. This danger must be compared to the risks presented by open fires. There is a
possibility of a burn if the black cooking pot used for solar cooking is touched while hot; but this
is true of any cooking pot. There is no danger of burns from the other components of solar
cookers. There are undoubtedly places where it is inadvisable to leave a solar cooker unattended
because of animals or children or thieves or, as has been suggested to us, poison. The same
problems confront those who cook outdoors over three stone fires. We know of no solution but to
keep an eye on the cooker from a shady place nearby.
Are solar ovens affordable in the developing world?
Not by the people who need them the most virtually nothing is. However, there are now durable,
efficient modern designs which can retail for $50 or less. There are continuing efforts to reduce
that cost further. Creative financing will always be necessary to achieve the widest possible
distribution. This includes micro banking, lay away plans, barter arrangements and subsidies. And
since solar energy is free, people eventually pay for their ovens with the money they have saved by
reducing their need for traditional fuels.
The basics of solar oven design
There are three practical models of
solar cookers.
Figure 2: Box oven, Bolivia. Photo; David Whitfield.
The box oven was introduced in the
1950s by Dr. Maria Telkes. A popular
model has a hinged, transparent top of
glass or plastic and the inside of the
box is black. Sunlight passes through
the glass, strikes the blackpainted
inside of the box and the light is
converted into heat, which cooks
whatever is in the box. Box cookers can
be of any size and can contain several
pots. They can be hand made, even out
of cardboard, and work well. The way
they work is very similar to ovens.
(Figure 2)
The most powerful solar cooker is composed of a
paraboloid reflector and a bracket to hold a pot. The
reflector bends the rays of light so that they are
concentrated at a focal point under the pot, making it very
hot indeed. The focal point is so hot that this kind of solar
cooker can fry food, unlike the other types of solar cooker.
These cookers work like the burner on an LPG stove. Dr.
Dieter Seifert developed a series of very efficient cookers
of this type that are now in use around the world.
Wolfgang Scheffler designed an 11-square meter reflector
that concentrates intense solar energy onto an area about
30 centimeters in diameter. It is used for solar cooking on
an institutional scale. (Figure 3)
Figure 3: Scheffler cooker. Photo:
Heike Hoedt.