2. Commercialisation of the Solar Dryer:
There are four common drying methods/techniques, that are utilised for drying
agricultural products.
a. The Old Traditional Way, The Open Air Drying
This is the present drying techniques used by urban and rural farmers. It is the old fashion
drying techniques, spreading the crops on a carpet or direct on the soil in open air and
exposed to the sun for drying.
b. Firewood/fuel drying
This technique is using fuel source to create the required heat for drying. It is used for
tobacco drying, and is common Uganda, and is more popular in West Nile for the tobacco
business.
c. Electrical drying
This technique is similar to No. 2, apart from heat, which is created by electricity as
energy source.
d. PV1 powered or simple Solar drying
The difference of this technique from the above mentioned, is that the heat is created by
the sun radiation. The heat could be circulated by a ventilator powered by PV array.
The three first mentioned techniques can be replaced by the environmental friendly
drying techniques.
2.1. The Solar Dryer Technology and Utilisation
The description of the solar drying technologies will be limited to few types, which are
very common and well known.
A. Low Cost Solar Dryer
The low cost dryer is similar to Nebbi type, which is presented at the case study of
Uganda (Se the Annex). There is of course different types of this kinds, such as the
cabinet solar dryer, the flat solar dryer, etc.The low cost dryer is the most suitable even for the small farmer, who have a very
limited income. It will be possible for them to cover the investment cost.
This is produced form locally available materials, and by local carpenter.
B. Electrical Solar Dryer- AC powered
This type is quite different form the low cost solar dryer, because this have bigger
size and are usually made for heavy duty, such as the tobacco, timber or coffee
drying. This type is supplied by fan to circulate the hot air inside the dryer. The
heating energy is provided by the sun collector placed on the roof. The following is
a medium scale solar crop dryer, developed at the university of the West Indies
since 1973, by Prof. Oliver Headley and Prof. Williams Hinds. The technical
design for this type, is provided in the Annexes chapter.
During the utilisation of this type in rural areas, the air circulation fan can be DC
powered. This type of dryer, can also be supplied by an electrical heating element
for providing the heat. The dryer is usually equipped with steering system to
control the drying temperature, which varies according to the type of crops.
Makerere University – Kampala - Uganda developed a similar dryer for timber
drying, but without any electrical equipment or Sun collectors. This type is
functioning as a greenhouse.
C. Solar Dryer - DC Powered:
This type is similar to the above mentioned AC powered, but a small size and
developed for drying only food crops, cash crops and fruits. The dryer consist of:
1. Sun collector panel for air heating
2. Drying chamber
3. Fan for the hot air circulation
4. Moisture and temperature sensor
5. PV- panel for powering the fan
This type is also applicable in rural area, if the quality of the dried products is
required. It is a bit expensive than the low cost types.
2.2 Suitability of the Solar Drying Technology for Commercialisation
a. The Product
From the table Nr.1, there is a clear indication of the need for the adoption of the
solar drying technology in the agricultural sector. The technology gap in Africa is
due to the lack of the availability of the suitable processing techniques for the
produced agricultural products, which can be adopted to local and the export
market. The technical innovation are not limited to farm-level production, but plays
an important role in all stage of the agricultural system. The challenge for the
entrepreneurs in the area /district, is to develop the solar drying techniques, that are
cost-competitive within the prevailing environment, and affordable for the endusers
(the small scale farmers). The earlier described solar dryer types are suitable
can be used by all farmers, but limited to the level of farmer.
Solar dryer type End-user Level Product Type
Low cost solar dryer Small scale farmers All types suitable for drying
Solar dryer DC-powered Medium size farmers All types suitable for drying
Solar dryer AC-powered Enterprises & timber traders Used most for Timber drying
Table 2. Target groups of solar dryers and suitability
b. The Materials
The locally available materials are an obligation to produce a competitive and an
affordable product to all farmers having different levels/status.
c. Production and Marketing:
A locally produced solar dryer, is the most suitable to be exploited locally. This is
because, the new technique does not require:
- Sophisticated introduction to local entrepreneur
- Long time adoption period to local end-users (easy to adopt, because it is
produced of a locally well known materials and techniques)
The commercialisation and the marketing of the processing technology would
therefore, encompass widespread distribution, adoption and acceptance of the given
solar drying technology by the key actors, in the production of food agricultural
post-harvest. The commercialisation of the solar dryer should not necessary be
restricted to profit making operations. Certainly, the sustainability of the introduced
technique and its contribution to social values in producing self-sufficiency food,
should be taken in consideration.
Cost Comparison:
Solar dryer type Initial investment Maintenance and operation costs Total cost2
US$ US$/year US$
Low cost solar dryer 100 to 200 10
Solar dryer PV-powered 500 to 1200 50
Solar dryer AC-powered 6000 100 to 300
Table 3. Cost comparison of the dryers
2. 3 The Advantage and Disadvantage by Using the 4 Techniques:
The following table shows the comparison of the 4 techniques:
The applied Drying Technique Advantage Disadvantage
Old traditional way - Open air
drying
? No investment is required
? No fuel is required
- The product is exposed to various
risks, such as dust, animals, ants,
rain, etc..
- It takes time to dry
- It requires labour to survey the
crops
- The quality of the drying is not
good (exposed to dust)
Firewood/fuel drying
? Quicker than the open air
type
- Requires investment in fuel
- Requires investment in building or
dryer box
- Pollution and forest degradation
- The quality of the dried product,
can be affected with smoke
- Not easy to control the drying
- Requires labour for operation and
maintenance
Electrical drying
? The drying is quicker, than
both the above mentioned
? The drying of the crops is
well controlled
? The quality of the dried
product is excellent, depending
on the type of the dryer
- The dryer is costly
- It is expensive to run and operate
the dryer
- The dryers require energy, which is
not available in rural areas
- It is not affordable for small farmer
and even co-operatives
- The dryer has to be installed in
building - further investment
- The drying is not environmentally
friendly – if powered by a generator
- Require labour for operation and
maintenance
- Requires introduction to the
technology
Solar Drying ? Very cheap investment - Requires introduction to the techno-
2 This cost is depending of the loan and the various expenses
? Very easy to maintain and
operate
? Does not require a specialised
manpower
? Well controlled dying
? Quicker drying
? The crops are well protected
during the drying process
? Can be produced locally, and
from local available materials
? Affordable to every body
? Environmentally friendly
? Does not require fuel
logy
- The dryer should be operated
properly to reach the good quality of
the dried products
- Requires a small investment
Table 4. Advantage and disadvantage of the dryer
From table 4, there is a clear indication, that the solar drying is the most suitable for the
small scale farmers to cover their needs, during the processing of cash crops. It is also
suitable for drying the available fruits and vegetables in the region, to generate income
