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solar cooker
A type of solar collector that
concentrates solar radiation
with the help of a reflecting surface on the back, top, and bottom sides
of a container. There are three main types: the box-style cooker, the panel
cooker, and the parabolic cooker. Each type has pros and cons when compared
on its heating ability, ease of construction, and ease and safety of use.
Box cookers
These are the most common for personal use. Despite the name "box" cooker,
they are made in both circular and rectangular shapes. They consist of an
enclosed inner box covered with clear glass or plastic, a reflector, and
insulation. The pot is placed inside and the open cover points the sun's
rays at the pot.
Many different patterns and plans are available that can be adapted to work
with whatever materials are to hand. While box cookers don't heat quickly,
they provide slow, even cooking. They are also very easy and safe to use,
and fairly easy to construct. Panel cookers
These are flat reflective panels that focus the sunlight onto a cooking
vessel without the inner box common in box cookers. Panel cookers are the
easiest and least costly to make, requiring just four reflective panels
and a cooking vessel; however, they are unstable in high winds and don't
retain as much heat when the sun is hidden behind clouds.
Parabolic cookers
These reach higher temperatures and cook more quickly than box or panel
cookers, but are harder to make and use. Most commercial solar ovens are
of the parabolic variety. Parabolic cookers require more precision to focus
the sunlight on the cooking vessel. If the sunlight isn't focused exactly,
the food will not cook. More expensive versions have a built-in tracking
device which automatically follows the sun; other the tracking has to be
done by hand.
When the parabolic oven is used, the temperature must be watched so the
vessel doesn't overheat, burning the food. With a diameter of 140 cm, corresponding
to an output of 600 W, they need about 25 minutes to bring 3 litres of water
to a boil; with half that diameter, a 150 W output, it would take about
40 minutes to boil just 1 litre of water. The risk of burns and eye injury
is greater with homemade parabolic designs. While they provide excellent
results when used correctly, they are not easy to build at home and require
great care to use. Related category
• SOLAR
ENERGY AND POWER
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