A simple solar dryer
Practical Action
the wall of the dryer are placed as outlets for hot air. Clay mixed with cow-dung and finely
chopped hay or rice husk or sawdust is used as mortar and plaster. This mixture is used to
avoid cracks.
Blackboard paint, which is non-toxic, can be used to paint the inside of the dryer, including
the trays.
Wooden or bamboo trays with wire or
bamboo mesh are used to hold the
food materials to be dried. If mesh is
not available, ‘Nanglo’ (traditional
bamboo sieve) can be used for this
purpose after making holes in it.
Transparent polypropylene plastic with a
wood/bamboo frame is used to cover the
dryer.
The cover is made tight to prevent
insects and pests getting in, and to
minimise the heat loss from inside the
dryer.
The size and capacity of the dryer can
be varied depending on need; the
bigger the volume to be dried, the
bigger the size of the dryer. Normally, a
0.9m x 1.8m or 3’x 6’ dryer is
sufficient for one household with 4 to
6 family members. The trays are made
to fit the size of the dryer and the
depth should be limited to 7 to 10 cm
or 3 to 4 inches.
Precautions
Care should be taken while handling
the plastic cover of the dryer as it can
be easily damaged. It may also be
necessary to keep children away from
the dryer to prevent damage. The
plastic should be replaced every two
months or when it is no longer
transparent.
Cost
The cost is between US$5 and US$8 d
in Nepal epending on the size of the
dryer and the availability of local skills
and materials as mentioned above.
Figure 3: The layout of the dryer. Illustration:
Practical Action.
Figure 4: Laying the bricks. Photo: E. Judge /
Practical Action.
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