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< prev - next > Crop processing Crop storage and preservation evaporative cooling (Printable PDF)
Evaporative cooling
Practical Action
In Sudan, Practical Action and the Woman’s Association for Earthenware Manufacturing have
been experimenting with the storage design of Mohammed Bah Abba. The aim of the
experimentation was to discover how effective and economical the Zeer storage is in
conserving foods. Zeer is the Arabic name for the large pots used. The results are shown in
the following table.
Table 1: Vegetable shelf-life
Shelf-life of produce without
using the Zeer
2 days
2 days
1 day
4 days
4 days
Shelf-life of produce using
the Zeer
20 days
20 days
5 days
17 days
20 days
As a result of the tests, the Woman’s Association for
Earthenware Manufacturing started to produce and
market the pots specifically for food preservation.
A bamboo cooler
The base of the cooler is made from a large diameter
tray that contains water. Bricks are placed within
this tray and an open weave cylinder of bamboo or
similar material is placed on top of the bricks.
Hessian cloth is wrapped around the bamboo frame,
ensuring that the cloth is dipping into the water to
allow water to be drawn up the cylinder’s wall. Food
is kept in the cylinder with a lid placed on the top.
Figure 2: The Zeer pot cooling system.
Photo: Practical Action Sudan.
An Almirah cooler
The Almirah is a more sophisticated cooler that has a wooden frame covered in cloth. There is
a water tray at the base and on top of the frame into which the cloth dips, thus keeping it wet.
A hinged door and internal shelves allow easy access to the stored produce.
A charcoal cooler
The charcoal cooler is made from an open
timber frame of approximately 50mm x 25mm
(2” x 1”) in section. The door is made by
simply hinging one side of the frame. The
wooden frame is covered in mesh, inside and
out, leaving a 25mm (1”) cavity which is filled
with pieces of charcoal. The charcoal is
sprayed with water, and when wet provides
evaporative cooling. The framework is mounted
outside the house on a pole with a metal cone
to deter rats and a good coating of grease to
prevent ants getting to the food.
The top is usually solid and thatched, with an
overhang to deter flying insects (Not shown in
Figure 2).
All cooling chambers should be placed in a
shady position, and exposure to the wind will
Figure 3: A charcoal cooler.
Illustration: Practical Action / Neil Noble.
help the cooling effect. Airflows can be artificially created through the use of a chimney. For
example using a mini electric fan or an oil lamp to create airflows through the chimney - the