Environmental Engineering Reference
In-Depth Information
6.3.6 Cooking with the Sun
In many countries cooking is still often done on an open wood fi re. About 2.5 billion
people around the world use this traditional method to prepare their meals. From
the energy point of view, however, an open fi re is anything but effi cient. Firewood
does not last long. In many countries wood is cut down at a faster rate than trees
can grow back. Furthermore, the smoke produced by open fi res is responsible for
many illnesses. In sunny countries solar cookers offer an alternative to traditional
hearths.
A solar cooking box is a very simple cooking system: a wooden box painted black
inside that is covered with a sheet of glass angled in the direction of the sun. This
very simple solar collector is actually capable of heating water and food. However,
it is not very effi cient and the glass cover makes it diffi cult to prepare food. An
effi cient solar cooker is a neater solution. With a solar cooker, the cooking pot
is situated in the middle of a convex mirror (Figure 6.18). The mirror is moved
approximately every quarter-hour so that it is directed optimally towards the sun.
With a mirror diameter of 140cm and good sun radiation, it is possible to bring
three litres of water to the boil in about half an hour.
Figure 6.18
Solar cooker in Ethiopia.
Photo: EG Solar e.V., www.eg-solar.de.
6.4 Planning and Design
Of all the solar thermal systems described, the systems that use solar heat to heat
up domestic water and to supplement other heating systems are the most widely
used. The planning tips are therefore limited to these two variants.
