DOMESTIC SOLAR DRYER
R.Gangi Reddy
Rural Development Organisation.
173,P.K.Street,Tirupati-517501,
Chittoor,dt,A.P. India
Introduction:
The vegetables and fruits are the rich source of nutrients for human body. They are available seasonally, but we require them around the year to keep our health. The rates of fruits and vegetables are abnormal in the lean period. The poor families less use in lean period due to their low financial condition. The price hike exerts effects directly on family economy. Therefore it is advisable to preserve the fruits and vegetables, when available at cheapest for the lean period in order to save the money and health.
The fruits and vegetables can be preserved by drying. Traditionally farmers dry the chillies, tamirind, groundnut, pulses and cearle under the sun heat to preserve. The sun drying depletes the nutrient contents. The sundry products are unhygienic, infectious and tasteless and original colour. The solar drying device is appropriate to overcome these shortfalls in sun dry. The domestic solar dryer developed by RUDO is an appropriate technology for rural communities living below poverty line to save the money and health of the family. The fruits and vegetables, fish, mutton and medicinal plant products available in the nature or at cheaper rates can be preserved with help of this device. In Rural area preservation of mutton called UPPASULU (parched mutton) is famous. Once or twice in a year the rural families butcher goat or lamb reared or purchased is butchered. The entire mutton is not eaten away in one or two days. Some parts of mutton are used to eat for one or two days, the remaining mutton is dried and preserved for two to three months to use as side dish for every day meal. Similarly the vegetables and unripe fruits are cut into pieces and sun dried to preserve is called ORUGULU is a traditional practice of preservation of available vegetables and fruits in harvesting season. The pickles are also one type of preservation. It requires sundried.The sun dried product last no longer to preserve. They remain as waste to throw away.
The solar dryer helps to retain the nutrients, taste, colour, odour, prevent infection and to preserve the fruits and vegetables, fish, mutton and medicinal plant products available in nature are grown in backyards. It is a poor mans technology, cost effective eco-friendly and technically feasible. Enormous solar energy can be used for food
processing using the appropriate Technology to save the power
How to fabricate a solar dryer:
We tried first solar dryer with Computer and TV packing boxes. Let us see how it is fabricated with Computer packing box. The box is cut slant top to down leaving 10 cm from the bottom as shown in photo below.After cutting inside is painted with black enamel paint and dried for 6 hours. The top is covered with transparent plastic sheet and air tight with gum tap around the open side like this.
The holes are made on sides, bottom and back side to flow out the moisture of drying products. The legs are fixed with thermocoal.A tray is made with mosquito net and card board to place the drying products in the dryer. A door is cut at the back side to place and remove the products inside with hand.
We can dry red chillies, tomato, brinjal, ladies finger, potato, and carrot, green leafy vegetables, medicinal plants parts, fish, mutton and pickles.The dried products can be packed in plastic cover to preserve the products to avail round the year. The cost of the unit is Rs 200/-.Any layman can fabricate by seeing once.
Material required:
1. TV or Computer packing box.
2. Axa blade
3. Transparent plastic.
4. Needle& Thread.
5. Mosquito net
6. Card Board.
7. Black paint.
8. Painting brush.
9. Scissor.
Technical Specifications:
Computer 14 x 11 Inches Packed paper box.:
Box size:
Length: 17.5 Breadth: 19 Height: 14.5
Sun Light hitting area (Open mouth area): 2.7 Sft
Area: 20.5 X 19=390 Sqin = 2.7 Sft.
Drying area (Drying material placing area):2.3 Sft
Area: 17.5 x 19 = 333 Sq in=2.3 Sqft.
Heating volume inside dryer:0.96 Cft
What to do before drying.
Mango/ Banana
? Wash well in clean water.
? Peel or cut slice to dry faster.
? Dip in lemon juice and water (2:1)
for less vitamins loss.
? Spread on tray
? Cover the dryer in night and if rains
or take it inside.
? After drying, pack in plastic bags.
? Hang it inside to protect from rates.
Guavas & Papaya
? Lemon juice is mixed with two parts
of water. This is heated gently and
double amount of sugar is gently
dissolved by stirring.
? Continue stirring until it cools
? Wash the ripe fruits
? Remove seeds and threads and cut
thin slice
? Immediately after cutting dip slice in
the syrup and hold for 15 minutes.
? Remove the slice and drain the syrup.
? Keep in dryer and pack after drying.
Many green leaves are good for drying. They should be cleaned well in water
and cut in smaller pieces. To keep many vitamins and keep a fresh colour
it is good to balance them before drying.
? Water with salt is boiled
? The vegetables are put in clean cloth
or basket.
? Hard vegetables are dipped in boiling
water 3 minutes.
? immediately taking them up and dip
in cool water
? Spread on tray for drying.
Performance:
We conducted experiment with Tomato, because the Tomato is available at lowest price Rs: 1 at the time of harvesting and at Rs: 20 in the lean period. The consumer can purchase and preserve for lean period to save money. The tray capacity of Tomato is 4 Kgs. The Tomato was dried for 4 days from 9 to 15 hours. The temperature variation inside and outside of the dryer and corresponding weight loss was recorded. The drying rate is 200g/day and maximum drying period is 6 days depends on the clouds. The number of days for drying depends on moisture content and the quantity, if the moisture and quantity is less the drying period decreases. The size decreases considerably and colour and odour remains same as fresh Tomato.
Cost Estimate:
TV pacel box, 1No. Rs 10
Black paint, 250 ml: Rs 25
Brush, 1No. Rs 10
Card Board 1.5sft: Rs; 20
Thread &needle 1 No Rs; 10
Nylon Net: 1 ft Rs; 30
Plastic sheet. 1mtr Rs; 30
Axe Blade 1 No Rs; 15
Scissor 1 No Rs; 50
Total: Rs; 200
How to use the dried products:
We can directly eat dried fruits or can be used in salads, ice creams. Etc.The vegetables can be roasted in oil mixing spices for side dish. The leafy vegetables can be powdered for preservation. The fish and mutton can directly used for cooking or roast.
Conclusion:
This model was developed for training and demonstrations for rural poor women. The well versed dryer can be fabricated with GI sheet and glass instead of paper box and plastic sheet for domestic purpose and the chambers can be constructed for drying agri produce. The farmers can save labour and risk drying the farm products. The dryer is easy to build; the operation is simple and straightforward and reduces drudgery in drying. The women can undertake the drying of fruits, vegetables, fish and mutton for preservation as small scale industry for self employment.
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