Drying in a solar dryer

Solar energy is collected by a special structure: a cabinet, tunnel or collector. The product can be protected from direct light and external contamination.

How it works

In a direct dryer, the sun heats the chamber containing the product. An indirect collector first heats the air, which passes through a separate chamber. The air moves naturally or with the help of a fan.

History

Development of open solar drying

The FAO sees solar dryers as an evolution of the traditional method: the design helps harness heat and organize air flow around the raw materials.

Several engineering options

The FAO guidance for small scale production describes direct and indirect devices. Therefore, the same solar dried inscription does not mean the same equipment or mode.

What changes in the product

More protection for the process

The chamber can reduce the contact of raw materials with the external environment. Actual results depend on design, cleanliness, load and ventilation operation.

The texture is not specified by the name

It is not the energy source itself that determines the softness of a slice or its crunch. When choosing, ask for a description of the finished shape and purpose, not just the name of the dryer.

The sun does not guarantee low temperatures

The temperature in the chamber may be higher than the ambient temperature. One cannot automatically consider such drying “raw” or promise the preservation of all vitamins.

Pros

• The solar collector provides some or all of the heat needed.
• The closed chamber allows for better organization of processing.
• A fan and additional heat can improve handling.

Limitations

• The result depends on the weather and the specific design.
• Systems with a fan or backup heat may require either electricity or fuel.
• The “solar” label does not reveal the pre-treatment.

Where is it used?

• Slices of mango, banana, pineapple and other fruits.
• Vegetable raw materials according to the manufacturer’s technological scheme.

When to choose

• The way to use the heat of the sun is interesting, and the taste and shape of the sample suits your purpose.
• The manufacturer describes the type of dryer and batch control.

When to choose another option

• The purchase is based only on the promise of "100% vitamins."
• A guaranteed unprocessed form is needed, but the composition and mode are unknown.

What to know before buying

• Direct, indirect or combined dryer?
• Was there additional drying, heating and pre-impregnation?
• How is the product protected from moisture after packaging?
• What texture to expect and is it suitable for soaking?