Solar Dryers For Agricultural Products

Grekkon Limited is the largest supplier of  low cost solar dryers for agricultural products in Kenya .  These are low cost solar dryers that work on solar strength, and are also augmented with a biomass heat unit if so desired by the client. Our agricultural solar dryers design is according to the product, location, and drying volume per session. These passive or active solar dryers for fruits and vegetables are fixed or portable as the user needs it. The fixed ones are large and impractical to move about, while the portable one are small domestic drying units

Solar dried mango slices

Types of Food Solar Dryers in Kenya

Grekkon limited designs and constructs both passive/ natural circulation, and active/ forced circulation solar dryers for agricultural products. The passive solar dryers have no additional mechanical input, while the active dryers do. Active solar dryers are also know as hybrid solar dryers. Their additional mechanical inputs are;  a biomass heating unit, or solar powered exhaust plus extraction fans, and synchronizers. A hybrid solar dryer will have one (solar system or biomass heater) of these enhancements, or both. These enhance drying time by 30% to 100% compared to passive drying. Attached biomass heating units allow for night time drying, or on cloudy/ rainy days. The amount of moisture left on the dried food varies from as low as 8.5% – 22% depending on the target food crop

Solar Dryer Materials

• Light UV treated translucent polythene paper to allow heat and light. The paper also has anti-drip treatment to prevent dew formation which causes moulding on food
• Heavy UV treated geomembrane to conserve heat
• Steel bars galvanized with food-grade aluminum or zinc for food safety
• UV treated heavy gauge netting to prevent insect pests from entering

A simple portable solar dryer under construction by the Grekkon technical team at Rusinga Island, Homa Bay county. The local community will dry bananas for processing into flour

Below are 2 videos: The first one is of a farmer in Homa-bay county, western Kenya using a community passive/ natural circulation solar dryer to add value to banana produce. The second one is of a mango processor in Taita Taveta county at the county’s coast with an active/ forced circulation dryer. Both solar dryers are by Grekkon Limited.

Video 1.

Video 2.

Our solar dryers for fruits and vegetables have shelves at different levels depending on the volume or weight of food crops to dry per session.

Solar Dryer Design

What is the working principle of a solar dryer?

1. Passive/ Natural Circulation Food Solar Dryer

Grekkon Limited solar dryers work in the following steps;

i. Capture & collect the sun’s heat

ii. Create a ‘greenhouse effect’ which causes moisture loss from the produce

iii. Air coming into the dryer exits with this moisture from the vent

2 Active/ Forced Circulation Food Solar Dryer

In addition to what takes place in the passive solar drying unit, the fans force in hot air from outside, and force out hotter air combined with moisture from inside the dryer. At night or on cloudy/ rainy days, the biomass unit supplies the drying heat.

Pros and cons of a food solar dryer in Kenya

1. Speed of drying. Food dries four to five times faster.
2. Quality. As the sun’s UV rays do not get into direct contact with the drying food, the food’s; color, taste, scent, and nutritional value is unaffected
3. Cleanliness. The food is free from dust, sand, or other external contaminants
4. No pests. Insect, bird, or mammalian pests have no access to food in the dryer, so no attack occurs
5. It is more expensive to build and maintain than open-air drying

Solar dried chilli peppers

 Solar Dryers For Agricultural Products

FAQs

III. What does a solar dryer do?

Grekkon Limited’s solar dryers reduce the moisture content to less than 12% in these products;

• Plantation crops; coffee, rice, cassava
• Vegetables; tomato, onion, garlic, brassicas, hot peppers
• Cereals; sorghum, and millet
• Herbs; moringa, mint, rosemary
• Oil crops; groundnuts, sunflower, macadamia, cashew nuts
• Others; mushrooms, fish, beef, mutton

IV. How do you dry vegetables with solar?

• Wash the vegetables to remove all dirt
• Ensure there are no insect pests present
• Remove any diseased parts or produce
• Cut or grind them into smaller pieces to increase the drying surface area

Place them in the solar dryer holding trays

Dry cassava chips

V. What is the most popular use of solar dryers?

To dry fruits, mushrooms, vegetables, herbs, spices, coffee, cassava, banana and fish. Banana and cassava are further processed into food flour. A solar dryer ensures that the food is free of any external contamination

VI. What are the main applications of a solar dryer?

Besides vegetables and fruits, commercial solar dryers in Kenya are for fish, root crops and mushroom drying. Commonly dried foods in Kenya through our solar dryers are:

i. Banana, cassava, pumpkin, millet, and sorghum to make food flour. Dried cassava is also processed for industrial starch manufacture

ii. Moringa as a medicinal herb

iii. Tomato, capsicum, traditional vegetables, kales, and spinach  as vegetable nutrients

iv.  Mango, papaya, as dried fruits for snacking

v.  Omena which is the silver cyprinid fish for both human consumption, and as additive to animal feed

vi. Coffee so that it’s suitable for milling. Coffee solar dryers are the largest, each holding over 5 tons of berries per drying session