Solar Thermal System for grain treatment is used to remove Amount of moisture present in grain/ Agricultural product. Amount of moisture present in grain is known as Moisture content of the grain.air and uncontrolled sun drying is still the most common method used to preserve and process Agricultural product.But uncontrolled drying suffers from serious problem of wind born dust, infestation by insect, product may be seriously degraded to the extent that sometimes become market valueless and resultant loss of and have to the food quality may have adverse economic effects on domestic and international market. Dryers have been developed and used to dry agricultural products to improve shelf life.

Advantages of Solar Drying System
1) Better Quality of Products are obtained
2) It Reduces Losses and Better market price to the products.
3) Prevent fuel dependence and Reduces the environmental impact
4) It is more efficient and cheap.

Disadvantages of Solar Drying System

1) Quality of products are not obtained in some cases.
2) Adequate solar radiation is required.
3) It is more expensive
4)Require more time for drying.

Methods of moisture content determination:

  1. oven dry method.
  2. Dielectric method.
  3. Infrared lamp method.
  4. Calcium carbide method.
  5. Pycnometer method.
  6. Sand bath method.
  7. Alcohol mehtod.
  8. Torsion balance method.

Wheat requirenment (Annual) :

wheat requirenment/day =10 kg

for 1 monthrequiment = 10 x30 = 300 kg

for 1 year Wheat requienment =300 x 12 = 3600 kg i.e 3.6 tonn.

Information about Vaccum Tube :

1.water tank : It consist a steel water tank having 200 lit capacity. in which one inner tank and one outer tank .Insulation is provided in betwwen both the tank to absorb the heat.

2.Evaculated tube : it consist a evaculated tube with glass covering is provided in betweem them. due to density difference hot water moves uupward direction.the length of evaculated tube is about 2100 mm and dimeter various from 45-53 mm.

3.Bracket tube : upper and lower bracket is provided to connect tubes.

Fig : Solar Water Heater

A Scheffler reflecter is a small lateral section of a paraboloid, which concentrates sun radiation over a fixed focus, with a automatic single axis tracking fixed focus automatically tracked eliptical dish.

some application of scheffler dish :

  1. food processing.
  2. solar cooking.
  3. laundary.
  4. drying and dying.

Fig : Scheffler

Information about Convectional dryer :

It is used to drying the grain. in which the hot air is provided from bottom of dryer. due to density diffrence the air is easily moves in uppward direction.

Fig : Convetional Dryer

Specific heat : Amount of heat required to raise the temprature of product by 1C.

Specific Heat of Water is = 1 cal/gm c

SpecificHheat of sand is =0.198 cal/gmc

Specific Heat of Mild Steel =0.10 cal/gm.c

we have to develope the temprature of system about 55c so water is best for use for thermal heating medium.

Feed rate for drying the grain during Application :

Annual Wheat Requirement is 3.6 tonn. we have to prepare machine to Dry All Wheat grains in 40 days (April-may)

So, The Feed rate for 4 toon = 4.46 gm/sec i.e 277 gm/ min.

The Feed rate for 5 tonn= 5.78 gm/sec i.e 347 gm/min.

LOD (loss on Drying) of Wheat or Moisture Content in Grain :

Fig : LOD Calculation

I was check the moisture Content of Wheat grain by oven dry method. it requires 90 min to remove all moisture at 110 C.

Initial weight = 50 gm, final weight = 46.44 gm.

Moisture content (%) = (initial weight – final weight)/initial weight x 100

Moisture content (%) = (50 – 46.44)/50 x 100

Moisture content(%) = 7.12 %

Tray dimension :

Scheffler concentration:

Area of focal surface = 0.30 x 0.45 = 0.135 sq. m

The max temp increases upto 150 0c

Fig : Scheffler Concentrator

Design of camshaft :

To provide vibration to grain tray i was prepared a cam in catia and cut with help of plasma cutting

Fig :Cam

Working on a Bending Machine :

To Bend a tray edges in 90 degree i was used the Bending machine.

Fig : Working On Bending Machine

Fabrication of Motor holding Stand :

To mount motor on a rigid unmovable surface i was prepared a one iron stand with help of welding.

Fig : Fabrication of Motor Holding Stand

Torque of Motor :

The Torque of Motor is about 5.4 kg cm

Fig : Vibrational Motor

Design of Outer frame of Grain Dryer :

1) Outer Frame :Outer Frame Is used  to mount hole Assembly.  It is made up of Iron square tube. It has high Strength. A square tube has more torsional strength if it is more massive (in the case of minimum diameter equal to the round tube) and it has those corners far out from the centre. The outward mass gives leverage in its advantage, torsionally.


 1) Height = 1100 mm

2) Length = 550 mm

3) Width = 330 mm       

Fig : Outer Frame

2) Inner Frame :Inner Frame is Mounted on a Outer Frame. It also Made up of Iron Square tube .The Square tube of 25*25*2 mm in Diamension.

Diamensions :

   1) Height : 1000 mm

   2) Length : 300 mm

   3) Width :  300 mm

Fig : Inner Frame

3) Shallow Tray :It is used to Store the Wheat Grain during Drying Process. The vibrational  motion is provided to that trays with the help of inner frame. There are 5 shallow trays used in machine each of 7 kg capacity. The material used for tray is Stainless steel because it not Affect on food grain.Stainless steel can withstand high heat and is better at retaining temperature than plastic, keeping cold foods cold and warm foods warm for longer! BPA free, phthalate free and lead free, Klee stainless steel food containers won’t fall apart or leach chemicals into your food like plastic containers. Stainless steel won’t absorb stains or odors and is easy to clean and sanitize, staying shiny for many years without showing wear and tear.

Properties of Stainless Steel :

1)    High and low temperature resistance.

   2)    Ease of fabrication.

   3)    High Strength.

   4)    Aesthetic appeal.

   5)    Hygiene and ease of cleaning.

   6)    Long life cycle.

   7)   Recyclable.

   8)   Low magnetic permeability.

Diamensions of Shallow Tray :

   1) Height  : 62 mm

   2) Length : 900 mm

3)Width    : 300 mm

Fig : Shallow Tray

4) Vibrational Motor : It is a Single Phase motor having 180 watt Capacity. The Revolution  of Motor is 1425 rpm. It is a Crompton Graves  motor. The Eccentric weight is mounted on its Shaft.An electric motor is an electrical machine that converts elecrical energy  into mechanical energy.

Most electric motors operate through the interaction between the motor’s magnetic field and electric current in a wire winding to generate force in the form of torque applied on the motor’s shaft. Electric motors can be powered by direc current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by  (AC) sources, such as a power grid,  electrical generators. An electric generator is mechanically identical to an electric motor, but operates with a reversed flow of power, converting mechanical energy into electrical energy.

Fig : Vibrational Motor

Connection Between Torque And Speed

For any rotatory motion, to derive the relation between torque and Power, compare the linear equivalent. The linear displacement is the distance covered at the circumference of the rotation and is given by the product of angle covered and radius. And linear distance is given by the product of linear velocity and time.

=> Linear distance = radius × angular velocity × time

Torque makes object undergo rotational motion. It is expressed as-

Torque = Force × Radius

=> Force=Torque/ Radius


Power=Force×LineardistanceTime Power=(Torque/RadiusRadius×Angularvelocity×TimeTime Power=Torque×Angularvelocity Torque=PowerAngularvelocity


Motor torque Calculation :

The rotational speed in motors is measured using rotations per minute. Thus on one rotation distance and linear speed is increases proportionally by 2??.

Torque=Power×Rotationalspeed Torque=Power×Rotationalspeed×ft.lbfmin×hp33000(ft.lbfmin) torque×RPM5252

Where, 330002π5252.113122

Hope you understood the relation and conversion between the Power and the Speed of a rotating object.


Solar Dryers for Wheat Treatment

Introduction :

All India Women’s Conference (AIWC) is one of the oldest and pioneering Women’s not for profit organization. AIWC was established in 1927 in India by an Irish Lady, Margaret Cousins, for the education & emancipation of women, along with eminent Indian women like Sarojini Naidu, RajkumariAmrit Kaur, and others. It has more than 150,000 members and 500-plus branches across the country working for the empowerment of women. Amongst many projects AIWC has undertaken one of the important programs is implementing application of renewable energy technologies with the objective of making them a tool of women’s self-reliance, through various low-carbon technologies for over four decades. India is the only country which has a separate Ministry of New and Renewable Energy, Govt. (MNRE) at the centre for promotion of renewable-energy technology. AIWC has collaborated with the Ministry for the successful implementation of the projects, being identified as one of the Nodal Agencies.

Objectives of the Project:

 • The solar energy application as a value addition device for the fruit- and vegetable-processing industry at a micro level, especially fruit bars/rolls.

 • Assurance that SHG members (mostly women) can operate this modern equipment with zero energy cost & maintain the equipment themselves with minimum help.

 • Saving enormous quantity of fruits and vegetables which perish all over the rural areas due to lack of preserving, processing & marketing facilities.

 • Helping all the Asian countries who are already preserving their produce into value-added & hygienic products

Solar Dryer For Food Processing ana Dehydration :

 Solar dryers

• The construction of the solar dryer involves a metal cabinet made of aluminum alloy with a glass window on top. The stainless-steel trays are provided in the cabinet to hold the material to be dried in the solar cabinet dryer.

 • Thermostat control sets temperature in mixed solar and electrical mode.

 • Closed trays are provided for easy loading and unloading of product.

 • Solar photovoltaic (PV) fan circulates air in the cabinet.

 • A special glass filter is provided to block Ultra Violet (UV) radiation and to reduce the solar intensity for special applications.

 • The product is clean and hygienically prepared, meeting cleanliness specifications of ASTA of USA.

 • The temperature achieved in the cabinet is in the range or 40-65°C on clear sunny days.

 • The temperature difference between the ambient and inside cabinet is 15-30°C on sunny days.

 • The dryer is rain-proof, dust-proof, rodent-proof and insect-proof due to fixation of an EPDM gasket, which can be replaced easily as needed and  moisture control in the product can be achieved by the regulation of drying time based on the intensity of solar radiation.

  • The critical size of the micro-enterprise is 4 solar dryers (SDM 50 Model) with a minimum capacity of 4,000 kg (4 tons) per annum of fruit bars/rolls. It is modular and scales well to any amount of demand

Advantages of the Technology :

 We can dry, prepare and preserve the following food items:

  • Many kinds of cereals like wheat, barley, etc. and their associated products- flour, maida, rice wafers, tapioca wafers, sevia, noodles, legmes; (green leaves like kasturimethi, pudina, drumstick leaves); root vegetables – potatoes, etc., other vegetables; fruits and their pulp; sweets, Mango bars; kadi masala powder/kadi leaf powder, ginger powder, masala & condiments, black pepper, dry tomato slices/powder, dry basil leafs, dry drumstick leaves, cured green chillies, cured bitter gourd, herbal plants, papad, forest products; fish, meat; coconut and many other products could be processed in less time. Though this dryer is expensive (about 11/2 lakhs), if 4 dryers are bought and run by SHG’s, there is big scope for earning very good income through supplying to local and foreign markets.

 • Most of all, when we are talking of food security, we could not only save tones of produce going to waste but provide good income for the women. In addition we could distribute nutritious food to our children and mothers. We could also help in mitigating global warming through the use low-carbon technologies.

 • If the food-processing technology is introduced at the micro-level, it will help to preserve perishable food products as well as create opportunities for increased rural employment. SHG members will be able to operate with zero energy cost and maintain the equipment themselves with minimal
Product preparation and Marketing.

The products were identified on the basis of season, fruits and vegetables available in the local market and market survey.

The branch in Tamil Nadu experimented with tomato powder, curry leaf powder, kasurimethi and bitter gourd powder. Delhi pilot dried tomato slices, kasurimethi, mango bars, kadi masala powder, tomato powder, amla powder and ginger powder. The members at Delhi dried basil, pudina and drumstick leaves apart from mango bars. Simple dry kadi leafs having medicinal values were also produced. The kadi leaves dissolved in water provide cure for BP problem in human beings. Kerala branch performed very well and experimented with curd green chilies, curd bitter gourd, black pepper, rice wafers and tapioca wafers. With their own efforts they have purchased one more dryer for their branch.

The details of each product were recorded systematically in a cost analysis report prepared specially for the project.

 Marketing Details: The prepared products were sold at the calculated prices based on the production and depreciation cost. A percentage of packed products were supplied as samples to retailers and canteens for testing. All of the solar dryer units have been promoting marketing through known linkages. At Delhi, packs of tomato slices were distributed as samples to specialty outlets and restaurants. Other products were sold through the AIWC counter at the main branch. Mango bars, methi leaves and ginger powders sold extremely well.

 The market study at Chennai and related experiences reveal that mango bar toffee can be marketed through school canteens and can fetch a good profit. At Chennai, marketing was done through school canteens, Red Cross Society, other NGOs, and local contacts. The Kerala unit tried to market the products through linkage and local sources. At each of these places, only one solar dryer was used, which helped us with the cost analysis

Learning :

This two-year research project brought out both technical and non-technical problems which created the base for upgrading the program and the solar dryer for further extension. :

• Chennai unit faced the problem of insect penetration. The reason was found to be a crack in a rubber tube.

• Thermocol packing used for fixing thermometer got damaged in Delhi unit, which increases the risk of mixing of the small pieces with the material being dried as well as risk of breakage of thermometer.

• Fans used were not of good quality. Now AIWC Hyderabad branch has managed to change them

Conclusion :

It is concluded that the pilot may be replicated in A- and B-grade cities of India and other Asian countries, as market is available for hygienic products. Self-Help Groups (SHGs) and individual women should be encouraged to take up the enterprise after proper training. The greatest positive factor of the enterprise is that it doesn’t involve full-time engagement and thus could be taken up by daily laborers, housewives, or other women engaged with some other active source, for SHGs or individuals. Apart from this, it saves an enormous amount of rural produce from perishing. Finally, it is concluded that the solar dryer use is suitable for wealth creation among poor women and plays a great role in reducing global warming. This could be easily replicated in all countries growing large amount of fruits and vegetables along with medicinal plants and with fish, which could be turned into value-added and hygienic products by solar