This document discusses solar dryers, which use solar energy to dry substances like food. It describes the two main types - direct and indirect dryers - and explains their construction and working principles. Solar dryers are needed to prevent spoilage of foods in rainy seasons and address other issues like spreading harvests. Key advantages are less drying time than sun drying, protection from pests and weather, and hygienic drying. The document also reviews improvements possible in solar dryers and their limitations, concluding that India should make more use of this renewable energy source to address food waste problems.

1. CONTENT
 WHAT IS SOLAR DRYER
 WHAT IS THE NEED OF SOLAR DRYER
 WHAT IS THE CONSTRUCTION OF SOLAR DRYER
 PRINCIPLE OF SOLAR DRYER
 ADVANTAGES OF SOLAR DRYER
 WORKING OF SOLAR DRYER
 IMPROVEMENT/ADVANCEMENT IN SOLAR DRYER
 LIMITATIONS OF SOLAR DRYER
 CONCLUSION

2. WHAT IS SOLAR DRYER ?
Solar dryers are devices that use solar energy to dry substances, especially
food. There are two general types of solar dryers: Direct and indirect.
 DIRECT
Direct solar dryers expose the substance to be dehydrated to direct sunlight.
They have a black absorbing surface which collects the light and converts it to
heat; the substance to be dried is placed directly on this surface. These driers
may have enclosures, glass covers and/or vents to in order to increase
efficiency.
 INDIRECT
In indirect solar dryers, the black surface heats incoming air, rather than directly
heating the substance to be dried. This heated air is then passed over the substance
and exits through a chimney, taking moisture from the substance with it.

3. WHAT IS THE NEED OF SOLAR DRYER ?
 In rainy season and winters due to presence of moisture a
foul smell develops in food grains and there is full
possibility of development of pests .
 It can also be used as filter .
 It make us rid of spreading food grains which was
required earlier at regular period of time .
 Drying in the direct sun has the risk of damaging the
complete harvest by rainfall
 Dehydration of fruits, potatoes, onions and other
vegetables
 Seasoning of wood and timber

4. CONSTRUCTION OF SOLAR DRYER
1) Solar panel : 12 volt and 10 watt
2) Electric motor : 150 rpm
3) Black absorbing wooden chamber
4) Glass cover : traps the heat generated and act as
insulator
5) Electric bulb (denoting sun) : 200 watt
6) Plastic container : To collect sand , pebbles , impurities

6. PRINCIPLE OF SOLAR DRYER
Our solar dryer is based on two principles .
 Conservation of energy in which one form of energy is
converted into other form of energy .
 Black body which absorbs the heat of the incident
sunlight and makes the temperature of chamber more
than the surrounding temperature .

7. Advantages of solar dryer
 Much less time is required for drying as compared to
direct drying because of black body .
 Protection of the drying products from insects but also
from birds, dogs, especially for drying meat and fish.
 The product is hygienic because microorganisms, insects
and flies are killed
 Protection of rain
 Protection of pollution by dust etc.
 Protection of the wind which can blow away the food

8. Working of solar dryer
Sunlight falls on the whole apparatus . Solar energy is converted into electric energy by solar
panel and this electrical energy is converted into mechanical energy by electric motor
which rotates the rod (CONSERVATION OF ENERGY)
Wooden chamber absorbs the sunlight and generates the heat and after some time inner
temperature becomes much larger than the outer temperature . Covering glass restrict the
flow of heat outside ( BLACK BODY )
It can also be used as filter by which dirt , sand , mustard seeds can be removed and can be
collected in a plastic box below .

9. IMPROVEMENT / ADVANCEMENT IN
SOLAR DRYER
In our project there are four advancements in our
knowledge :
 Solar panel can be censored to the movement of sun as
sunflower so that.
 The electrical energy produced by solar panel can be
stored in a battery which can be used when sunlight is
not available .
 Temperature censor can be used which can control over
heating of food grains .
 Automatic refilling of container .

10. Limitations of solar dryer
 Not workable at night .
 Efficiency decreases to a large extent on cloudy days .
 Over heating may occur if regular attention is not paid .
 Due to over heating it can decrease the quality of food .
 Change in taste and flavor of food may occur if regular
monitoring is not done .
 We cannot get the accurate amount of sun rays and heat .

11. conclusion
In a country like India where 300 days out of 365 days are sunny have a huge asset
of solar energy . Government is also promoting the use of renewable sources of
energy like solar energy by providing subsidies on solar pumps , solar water
heater , solar panels , solar lights etc. son we should take advantage of these
schemes .
Use of solar energy costs us nothing just only solar panel , sunlight is free of cost
and sun is a non finishing source of energy .
Almost every year there are news of rotten food grains in newspaper which causes
a huge loss to farmers but if we design those godowns on the concept of black
body then such condition will not occurs .

12. THANK YOU ……