Solar dryers are devices that use solar energy to dry substances, especially the food. Drying is one of the methods used to preserve food products for longer periods. Different types of solar dryers have been designed, developed and tested in the different regions.

1. ASSIGNMENT WORK ON
SOLAR DRYER
SUBJECT TEACHER ASSIGNMENT GROUP MEMBERS
Prof. Dr. S.K. SAMDARSHI VISHAL KUMAR
NILESH KR SINGH

2. INTRODUCTION
• Solar dryers are devices that use solar energy to dry substances,
especially the food.
• Drying is one of the methods used to preserve food products for
longer periods.
• The heat from the sun coupled with the wind has been used to dry
food for preservation for several years.
• Different types of solar dryers have been designed, developed and
tested in the different regions.
• Solar air heaters are simple devices to heat air by utilizing solar
energy and is employed in many applications requiring low to
moderate temperature below 80°C, such as crop drying and space
heating.

3. TYPES OF SOLAR DRYER
1. Direct (integral) type solar dryers
2. Indirect (distributed) type solar dryers
3. Mixed mode type solar dryers

4. a) Direct (integral) type solar dryers: Direct solar dryers expose the
substance to be dehydrated to direct sunlight with a transparent cover on
it. Heat is generated by absorption of solar radiation on the product itself.
In this two ways of heating is done that is:
• Active Direct type solar dryer
• Passive Direct type solar dryer
Active Direct type solar dryer:
In this work, a direct type active
solar dryer is fabricated which is
commonly used in areas that
receive direct sunlight for long
periods during the day. In this active
Exhaust fan is installed at the bottom
to remove the air.

5. • Passive Direct type solar dryer:
In this passive type direct solar
dryer natural circulation of solar
energy is employed in the
cabinet with chimney. The
horizontally aligned dryer has
black-coated internal walls for
improved absorption of solar
radiation.
Advantage: It can dry the
harvested field paddy of 20kg
within 9 hours and reduce
moisture up to 31%.

6. Indirect (distributed) type solar dryers: In this type the system is not
directly exposed to solar radiation in order to minimize discolorations and
cracking. The drying chamber is used for keeping in wire mesh tray. A
downward facing absorber is fixed below the drying chamber at a sufficient
distance from the bottom of the drying chamber.
In this two ways of heating is done that is:
• Active Indirect type solar dryer
• Passive Indirect type solar dryer

7. In this active Indirect solar dryer,
the forced convection solar energy
is employed. The fan or pump is
employed at the base. Then this
forced circulation of air is brought
to the drying chamber where it
dries the food. After that forced
air is allowed to move out through
the exit door.
Advantage: This type of design
used for the application by rural
farmers.
• Active Indirect type solar dryer

8. Passive Indirect type solar dryer
operate by using entirely
renewable sources of energy, such
as solar and wind. In this fan or
pumps are not used instead wind
and solar energy are used to dry
the food items.
Advantage: Have a high capacity
of trays accommodation which are
stacked inside the dryers and it is
having low cost.
• Passive Indirect type solar dryer:

9. 3. Mixed mode type Solar Dryers:
In these dryers, the combined
action of the solar radiation
incident on the material is dried
and the air is preheated in solar
collector provides the heat required
for the drying operation.
Advantage: The temperature rise
inside the drying cabinet is up to
74% for about three hours and the
system efficiency ranges to about
60 %.

10. Hybrid type solar dryer
• There is also other type of dryer that is Hybrid style solar dryer. It
consists of a solar collector, PV cell, heat storage with auxiliary
heating unit, and drying unit.

11. BENEFITS
1. Much less time is required for drying.
2. Protection of the drying products from insects but also
from birds, dogs, etc.
3. Especially for drying crops like paddy, wheat and also in
non-veg materials like meat and fish.
4. The products is hygienic because microorganisms, insects
and flies are killed.
5. Protection from rain.
6. Protection from pollution by dust etc.
7. Protection from the wind which can blow away the food.

12. DRAWBACK
1. Limited time we get to dry.
2. Quality of products are not obtained in
some cases.
3. High initial cost.
4. Skilled person required.
5. Sometimes maintenance is also required.
APPLICATION OF SOLAR DRYER
1. Agricultural crop drying
2. Food processing Industries
3. Fish and Meat drying
4. Dairy Industries
5. Textile Industries

13. CONCLUSION
1. Solar dryer is the best alternative option to avoid disadvantages of conventional drying
methods.
2. It is the best source of renewable energy system which increases the application renewable
sources as an income generating option during the shortage of non-renewable sources.
3. Solar dryer is designed particularly for drying agricultural products. In this paper direct,
indirect natural, indirect forced convection drying.
4. Time required for drying in mixed mode solar dryer is less than other type of dryer.
5. Force circulation drying gives better result than natural circulation solar dryer.
6. Hybrid dryer system is also found as better dryer due to increased circulation of air due to
auxillary heater and also the recycling of radiant air is done efficiently.

14. REFRENCES
“Data based on solar dryer” from textbook ‘Principles of Solar Engineering’ by D.Yogi Goswami, University
Professor and Director of Clean Energy Dept. ‘University of South Florida’, Published by Taylor & Francis group on 2015.
2. “Data based on solar dryer Introduction”
Website-‘https://www.slideshare.net/AnugrahSoy1/project-report-on-solar- dryer?from_action=save’ published 2015,
accessed on 09/04/2020 10:15.
3. “Data based on Active Direct type solar dryer”
Website- ‘https://www.sciencedirect.com/science/article/pii/S0196890498000934’ published 1999, accessed on 09/04/2020
12:24
4. “Data based on Passive Solar Energy dryers”
Website‘http://energyprofessionalsymposium.com/?cat=62&paged=16S0196890498000934’ published 2018, accessed on
09/04/2020 01:04.
5. “Data based on Mixed mode type solar dryers” from Journal “Performance Evaluation of a Mixed-Mode Solar Dryer”
by ‘Bukola O. Bolaji and Ayoola P. Olalusi’ Department of Mechanical Engineering, ‘University of Agriculture Abeokuta,
Ogun State, Nigeria’ published 1999, accessed on 10/04/2020 10:14.
6. “Data based on Hybrid type solar dryer”
Website- ‘https://www.researchgate.net/figure/Schematic-diagram-of-photovoltaic-air-heater-assisted-heat-pump-drier-
24_fig4_319647846’ published 2017, accessed on 10/04/2020 03:05.