Renewable energy technology
STUDY OF VARIOUS TYPE OF SOLAR DRYER
Abstract: The unpredictable increase and frequent scarcity of fossil fuels has accelerated the ongoing search
for an alternative source of energy. Solar energy is one of the renewable and sustainable energy sources that
has attracted a large community of researchers from around the world. This is largely due to its abundance in
direct and indirect form. As such, the development of efficient and inexpensive equipment for drying
agricultural and marine products has led to a change in their usability, thus improving the quality of products
and the quality of life. The use of solar dryers for drying agricultural products can greatly reduce or eliminate
product waste, food poisoning and, in some cases, improve farmers' productivity for better incomes. A solar
crop drying system does not depend solely on solar energy to function; It combines the combustion of fuel
with the energy of the sun, thus reducing the consumption of fossil fuel. In this article, an analysis of the solar
dryer is presented. The different designs of the solar dryer are described in the literature so far.
I. INTRODUCTION
Drying in the sun and in the open air is still the most commonly used method of preserving and
processing agricultural products. But uncontrolled drying suffers from severe dust problems caused by
wind, insect infestation, The product may be seriously degraded to the point of sometimes becoming a
loss of value and the loss of food quality may have adverse economic effects on the domestic and
international markets. Dryers have been developed and used to dry agricultural products to improve
shelf life (Esper and Muhlbauer, 1996). Most of them use a costly source of energy such as electricity
(El-Shiatry et al., 1991) or a combination of solar energy and another form of energy (Sesay and
Stenning, 1996). . Most projects of this nature have not been adopted by small farmers, either because
the final design and data collection procedures are often inappropriate or the cost has remained
inaccessible and the subsequent transfer of researcher technology to the end user has been anything but
effective (Berinyuy, 2004). The purpose of this study is to present some basic types of solar dryers in
order to provide a best idea of their effectiveness in drying agricultural products.
Renewable energy technology
Advantages of the solar drying system
1) Better product quality is obtained.
2) It reduces losses and offers a better market price to products.
3) The products are protected against flies, rain and dust; the product
can be left in the dryer overnight
despite the rain, since the driers are impervious.
4) Prevent fuel dependence and reduce the impact on the environment.
5) It is more efficient and less expensive.
Disadvantages of the solar drying system
1) The quality of the products is not obtained in some cases
.2) Adequate solar radiation is required.
3) It is more expensive. It takes more time for drying.
CLASSIFICATION OF SOLAR DRYER
Solar Dryer is available in a range of used for drying various agricultural products. Different types of
dryers are available on the market as needed. Mainly, all drying systems are classified according to their
operating temperature: high temperature solar dryer and low temperature solar dryer.
The following criteria are required for the classification of the solar dryer: -
6) Air circulation mode
7) Insulation exposure
8) Air flow direction
9) Dryer layout
10) Solar contribution
Renewable energy technology
2.1) Direct solar dryer
Figure 2.1. A schematic diagram of Direct solar dryer
It is a type of dryer in which solar radiation is directly absorbed by the product to be dried. This type of
dryer includes a drying chamber covered with a transparent glass or plastic cover. The drying chamber
is usually a shallow, insulated box with air holes to allow air to enter and exit the drying chamber.
2.2) Indirect solar
dryer
Figure 2.2. A schematic diagram of an Indirect solar dryer
The solar radiation obtained by the system is used to heat the air passing through the product to be dried
in this dryer. With regard to drying, the quality of the product has improved, but the drying rate has
increased. The heated air is blown into the drying chamber. At the top of the drying chamber, vents pass
through the humidity. Indirect type solar drying systems provide better control of drying. Figure 2.2
Describes another principle of indirect solar drying, usually called conventional dryer.
Renewable energy technology
2.3) Forced convection and natural convection solar dryer
2.3.1) Forced convection - In this type of dryer, air is forced through a solar collector and the product
bed by a fan or
blower, usually called an active dryer.
Figure 2.3 A schematic diagram of Forced convection solar dryer
2.3.2) Natural convection - In this dryer, a natural movement of the air takes place, called passive
dryer. The heated air
flow is induced by the thermal gradient.
Figure 2.4 A schematic diagram of Natural convection solar dryer
Renewable energy technology
2.4) Solar drying in mixed mode
Figure 2.4 A schematic diagram of Solar drying in mixed mode
It's a combination of direct and indirect solar drying method. The product can dry with direct exposure
to solar radiation and hot air supplier on it. Air can be heated in the solar energy collector first, then go
to the room where the products are stored. In this treatment product can dry according to loss of
moisture by convection. The same room . The system is divided into three main components: an air
heater, drying room and a fireplace. Air heater through which the drying air is heated as flows on and
under an absorbing plate which is heated in turn by direct absorption of incident radiation. The crop to
be dried is placed in the drying chamber. Moist air flows through the chimney and escapes into the
entourage is partially or totally covered with transparent material for exposure of products to solar
radiation.
II. APPLICATIONS OF DIFFERENT SOLAR DRYERS
It is suitable for small farmers in rural areas, where the electric current is not available. This kind
dryer is more effective in drying small quantities of crops, fruits and vegetables. A natural
product of indirect type manufactured locally the convection dryer is useful for drying fruits and
vegetables in rural areas.
A solar Tunnel dryer can be used for drying jackfruit bulb sand leather.
Solar forced convection the dryer is used in small Companies with limited financial support from
large industrial sectors. the dryer requires some time to dry the products and is built to last.
The natural convection dryer is more advantageous and applicable than other types.
In the meantime, the low cost solar indirect convection type dryers are used to dry cassava,
bananas, and raw rice, among others some products.
Renewable energy technology
III. LITERATURE REVIEW
[1]Diemuodeke E. OGHENERUONA *, MomohO.L. YUSUF: - Direct and natural convection solar
dryer designed and manufactured to dry tapioca in rural areas. A minimum solar collector area of 7.56
m2 is required to dry a batch of 100 kg of tapioca in 20 hours (two day drying period). The initial and
final moisture contents considered were 79% and 10% respectively in humid conditions. The average
ambient conditions are air temperatures of 32 ° C and 74% relative humidity, with daily global solar
radiation incident on a horizontal surface of 13 MJ / m2 / day. The weather conditions are as follows:
Warri (5 ° 30 'long, 5 ° 41' long), Nigeria. A prototype dryer was manufactured with a minimum
collector area of 1.08 m2.
[2]M. MOHANRAJ, P. CHANDRASEKAR: - The performance of an indirect forced convective
floorboard, integrated with a heat storage material, was designed, manufactured and studied for cold
drying. The dryer with heat storage material maintains a constant air temperature inside the dryer. The
inclusion of heat storage material also increases the drying time by about 4 hours per day. Thechili was
dried from the initial moisture content of 72.8% to the final moisture content of about 9.2% and 9.7%
(wet basis) in the lower and upper trays, respectively. . The thermal efficiency of the solardrier was
estimated at about 21% with a specific moisture extraction rate of 0.87 kg / kWh
Bukola O. Bolaji.et.al:- Designed, built and tested the solar wind ventilated cabinet dryer in Nigeria at a
latitude of 7,5oN. During the test period, the average air speed in the solar dryer was 1.62 m / s and the
average efficiency of the system in daylight was 46.7%. The maximum temperature of the drying air was set
at 64 ° C inside the dryer. The average air temperature in the drying oven was above room temperature in
the range of 5 ° C to the early hours of the day at 31 ° C in the middle of the day. in the dryer.
Renewable energy technology
CONCLUSION
After studying different types of dryers, a solar dryer with indirect focus having recirculation of hot air
is more appropriate so others of the food preservation like as well as the conservation of time and energy
conservation also because there is no risk of appropriate sunlight as that in direct solar desiccators and
air losses in this type of indirect solar dryer where there is no recirculation air and takes longer drying
process compared to air Re-circulating solar dryer. Direct dryers are mostly best for areas where the
adequate resources (such as electricity and other manufacturing material used indirect and mixed mode
manufacturing tumble dryers) are not available.
REFERENCES
[1] Diemuodeke E. OGHENERUONA, Momoh O.L. YUSUF.Design and manufacture of a direct
natural convection dryer for tapioca; Department of Mechanical Engineering, University of
PortHarcourt, Department of Civil and Environmental Engineering, University of Port Harcourt, P.M.B.
5323, Choba, Rivers State, Nigeria; Leonardo Electronic Journal of Practices and Technologies ISSN
1583-1078; Number 18, January-June 2011 p. 95-104.
[2] Mr. Mohanraj, P.CHANDRASEKAR. Performance of a forced convection solar dryer integrated
with gravel as heat accumulator for chili drying School of Mechanical Sciences, Karunya University,
Coimbatore-641114. India, School of Engineering and Sciences, Swinburne University of Technology
(Sarawak Campus), Kuching Sarawak - 93576 Malaysia; Journal of Engineering Science and
Technology Vol. 4, No. 3 (2009) 305-314.
[3] Bukola O. Bolaji and Ayoola P.Olalusi. Performance Evaluation of a Mixed-Mode Solar Dryer;
Department of
Mechanical Engineering, University of Agriculture Abeokuta, Ogun State, Nigeria;AU J.T. 11(4): 225-231
(Apr.2008).
[4] Bukola O. Bolaji , Tajudeen M.A. Olayanju and Taiwo O. Falade. Performance Evaluation of a Solar
Wind-Ventilated Cabinet Dryer;Department of Mechanical Engineering, The Federal University of
Agriculture, P.M.B. 2240, Abeokuta, Nigeria; The West Indian Journal of Engineering Vol.33, Nos.1/2,
January 2011, pp.12-18; (Received 11 August 2005; Accepted January 2011).
[5]Ahmed Abed Gatea. Design, construction and performance evaluation of solar maize dryer;
Department of Agricultural mechanization, College of Agriculture, University of Baghdad, Iraq;Journal
of Agricultural Biotechnology and Sustainable Development Vol. 2(3), pp.039-046, March 2010;
Accepted 29 October, 2009
