SOLAR DRYER

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 Direct (integral) type solar dryers Indirect (distributed) type solar dryers Mixed mode type solar dryers

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

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

13. CONCLUSION Solar dryer is the best alternative option to avoid disadvantages of conventional drying methods. 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. Solar dryer is designed particularly for drying agricultural products. In this paper direct, indirect natural, indirect forced convection drying. Time required for drying in mixed mode solar dryer is less than other type of dryer. Force circulation drying gives better result than natural circulation solar dryer. 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.