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Technologies - Solar Stills For Water

About Solar Dryer

Solar drying is a traditional practice for the preservation of food and agriculture crops

The open sun drying method has several disadvantages

spoilage of product due to adverse climatic conditions like rain, wind, moisture, and dust
loss of material due to birds and animals
growth of insects and fungi; and so on.

Solar drying is the best alternative solution to all the drawbacks of open sun/natural drying and artificial mechanical drying.

Solar dryer is a device which absorb most of the heat energy from the sun and transmit the heat to the air, present inside the dryer. The heated air will takes away the moisture of the food product and make it to dry quickly.

Early model in MCRC

This model is a portable and low cost made of Kadapa stone and covered by glass. It has limitations like heavy weight, works only in the sunny days, high temperature developed up to 70⁰C So it not suitable for drying food products. It is used for drying some other components.

New model under DST Core

This system consists of drying chamber and 60W PV panel for converting solar radiation into electricity. This panel has been integrated with dryer for powering the 12V DC fan to circulate the air inside the dryer. In this case the drying unit is a single unit of black box which traps most of the solar radiation or heat. The incoming solar light fall on the PV module, which converts solar radiation into electricity. When the solar rays fall on the dryer its surface gets heated up, the air inside the dryer is in circulation by fan, so the air which passes over the surface of the dryer, gets heated due to convection. This hot air passes through the food product to be dried which is placed on trays absorbs the moisture present in the drying product.

Operation Process

During daytime it will heat up by direct solar radiation.
During night time heating up by firing charcoal or wood at the bottom

During rainy and winter season same as night operation.

Battery backup is needed for operation of fan to circulate the air inside the dryer.

Battery charges by PV panel.

Assembled View

Experimental result of fish before and after drying

Fish

Initial weight (gm)

Final weight (gm)

Time taken

Weight reduction %

Dried in open sunlight

2000 gm

903.24

72 hr

45.16

Dried in solar dryer

2000 gm

757.90

56 hr

37.89

If the fish need to dry 757 gm in traditional method it will took 83 hr. So time saved is 27 hr.

Solar drying of leaves

Moringa leaves were tested.

It is found that the leaves were drying at faster rate within 3.5hr of time, while traditionally it took 2 to 4 days time to dry depending upon climatic condition..

Advantages of this dryer

Both shade drying and open drying is possible.
Open direct sunlight heating is possible by removing the top cover of the dryer and providing transparent thin polyethylene film sheet. This will transmit 99% of direct solar radiation.

Reduces drying time.

Works throughout the year. It can work at night and during rainy season by burning biomass under the dryer.

Easily assembling and disassembling and light weight for transportation purpose.

Very low maintenance.