Solar Dryers
Solar Dryers by Instefast, The Best Farmer`s Choice
As a farmer, drying is one of the most crucial post- harvest exercise that if not handled well, can have harsh economic consequences to a farmer. A lot of food is wasted or spoilt during this exercise. Solar dryers’ technology offers the best solution. It is efficient, economical, easy to build and maintain and can handle different types of products. They can also be installed in any environmental condition.
WHY OUR SOLAR DRYERS?
We offer the best solution to value addition and increased shelf life of agricultural produce. Our solar dryers use the ever available and renewable solar energy to dry (remove moisture from) your produce.
It is affordable, safe, and efficient, adds value, hygienic, increases shelf life, and reduces food spoilage, wastage and loss due to spillage.
We are also constantly updating our solar dryers with the latest technology and designs to ensure maximum drying and benefits
What is solar drying?
Solar drying can be defined as the method of removing water/moisture from products like agricultural produce e.g. grains by spreading them under the sun.
Solar drying can, basically, be classified into:
1. Open Sun Drying
This is the traditional way of drying agricultural produce. Drying is achieved by spreading the produce like grains or cereals under the sun where the direct heat radiation/ high temperatures from the sun extract/reduce moisture of the produce to achieve drying. The method is the simplest, cheapest and applies in all areas that have a good exposure of the sun.
This method however is faced with challenges/drawbacks that includes;
- Takes time to dry compared to indirect sun drying methods
- Hard to maintain hygiene and quality of produce
- The produce is exposed to so many external factors like pests, animals, wind, bacteria, and other airborne
- The method is tedious as the produce has to be spread out only when there is sun and restored when the sun sets or on bad
- Increases postharvest losses due to unlimited movements of produce during the process of
2. Direct Sun Drying
Solar radiation incidents on the transparent glass cover are easily transmitted into the cabinet of the dryer. Most of the radiation is transmitted into the cabinet of the dryer, and the remaining part of the radiation is reflected back. The crop surface reflects part of the radiation, and the remaining part is absorbed by the crop surface, which thus increases the temperature of the crop. The heated crop starts emitting long-wavelength radiation, but the long wavelength radiation cannot escape into the atmosphere due to the presence of the glass walls and cover; thus, the presence of both the incidental and reflected radiation within the chamber further increases the temperature to be higher than that of the crop.
3. Indirect Sun Drying
This is the method of drying where heat radiations from the sun pass through a medium before getting to the products to be dried. The heat through the medium then heats up the air in or below the medium raising its temperature. The dry hot air then is passed through the produce which takes up moisture after which the moist air is directed out of the drying unit. The products to be dried are not exposed to direct sun radiations
What is a solar dryer?
A Solar dryer is a device/structure that is made/built/assembled and engineered to use/harness the sun’s energy (heat from the sun) to dry food and other products that require drying. Solar dryers are a sustainable alternative to traditional methods of food drying, such as open-air drying, which can waste energy and pollute the environment.
How does a solar dryer work?
Solar dryers use a simple yet ingenious principle. Air from the surrounding (ambient air) gets into the dryer through a directional opening/ventilation window or through solar powered inlet fans to a collector. In hybrid options, ambient air gets into an artificial heat pump first before getting into the dryer collector. Air is then heated by heat from the sun as it moves towards the drying chamber. Hot dry air in the drying chamber moves through the products (placed in perforated drying racks) taking up moisture from the products. Moist air then moves out of the dryer through another directional ventilation window/vent or a solar powered exhaust fan.
What are the components/parts of a basic solar dryer?
1. Solar air collector
This is a component of the solar dryer that collects/receives sun radiation and concentrates it ready for utilization. The heart of a solar dryer is the solar air collector, usually a curved or flat, angled surface covered with a transparent material like glass or plastic. The transparent cover allows solar radiation to enter while minimizing heat loss. It also has a dark/black lining that attracts more heat (heat absorber).
2. Drying chamber
This is the component of the dryer that actually holds the items to be dried. It is made such that it minimizes heat loss and concentrates the heated air from the collector to the items to be dried. It has layered drying racks or multiple trays that support the products to be dried.
3. Exhaust windows/Chimney/Exhaust system
This is the component of the dryer that expels the moist air out of the dryer. It creates a negative pressure in the dryer, allowing more hot air in the dryer thus increasing air flow in the dryer. This in-turn increases drying rate in the dryers.
In natural dryers it is just a chimney opening windows but in improved and hybrid versions it incorporates fan systems that accelerates the flow of air in the dryer.
What are the types/categories of Greenhouse solar dryers in Kenya?
Greenhouse solar dryers can further be divided into 3 categories:
i.) Natural Convection Solar Dryers
These are simple greenhouse solar dryers that use the direct sun radiation to heat up the naturally and freely moving air and the crop in the drying chamber through the canopy of the drying unit. The canopy/roof can be rectangular like the roof of a house or curved into a tunnel. Ventilation in natural solar dryers are provided at the bottom and top or either side of the dryer. The buoyant effect of moving air (in and out) help in the circulation of heated dry air through the products.
ii.) Forced Convection Solar Dryers / Improved Greenhouse Solar Dryers
These are Greenhouse solar dryers designed with an optimal controlled air flow. The movement of hot dry air in the system is controlled by an improvised ventilation system like exhaust fans, inlet fans and roof ventilators. The controlled movement in turn helps in regulating humidity or moisture evaporation and temperature. Exhaust fans eliminate hot humid/moist air and inlet/axial fans force in hot dry air in the drying chamber while the roof ventilators act to balance the air difference in the drying unit.
An improved greenhouse solar dryer is a sustainable and energy-efficient solution for drying agricultural products especially high moisture content products, such as tomatoes, papaya, grapes, chilis, kiwis, bitter- gourds, cabbages, brinjal, and cauliflower.
This improved greenhouse solar dryer combines’ solar energy utilization, precise humidity measurements, and effective ventilation to create an energy-efficient and environmentally friendly solution for drying agricultural products. It allows for faster and more controlled drying, reducing the risk of spoilage and ensuring higher product quality.
What are the basic components of a forced/improved convection greenhouse solar dryer?
- Solar Panels: These panels are installed on the roof of the greenhouse to harness solar energy. The energy generated is used to power various components of the system.
- Inlet and Outlet Fans: These fans are strategically placed to ensure proper ventilation within the greenhouse. Inlet fans bring fresh air into the greenhouse, while outlet fans expel moist air. This ventilation helps maintain a consistent and controlled drying environment.
- Humidity Monitoring Device: A humidity monitoring device, such as a hygrometer continuously measures the relative humidity inside the greenhouse. This data is crucial for controlling the drying process.
- Cyclone/Roof Turbo Ventilator: The cyclone or roof turbo ventilator is an exhaust system that enhances natural convection within the greenhouse. It helps in removing hot and moist air, contributing to effective drying.
iii.) Hybrid Greenhouse Solar dryers
Hybrid solar dryers combine solar energy with another heat source, such as electricity or biomass. This design ensures a consistent heat supply even during cloudy days or at night. Hybrid dryers are suitable for regions with less predictable weather patterns or for applications that require precise temperature control.
Advantages:
- Reliability in various weather
- Flexible heat sources for optimal
- Better control over drying
How much does it cost to construct a solar dryer in Kenya?
TO NOTE: ……
What are the available sizes of solar dryers in Kenya?
What are the factor that affect/determine the size of a solar dryer in Kenya?
- Quantity (kgs or tones) to be dried
- Type of product to be
- Space
- Available storage after drying or market
- Available
What are the advantages of solar dryers in Kenya?
Solar dryers offer several significant benefits over traditional drying methods:
- Energy Efficiency: Solar dryers utilize renewable solar energy, reducing the need for electricity or fossil fuels, thereby lowering energy consumption and
- Environmental Friendliness: By relying on the sun’s energy, solar dryers have a minimal carbon footprint, contributing to a more sustainable and eco-friendly
- Preservation of Nutrients and Quality: The gentle drying process at lower temperatures helps preserve the nutritional content, flavors, and overall quality of dried
- Income Generation: Solar dryers can be used to produce dried goods for sale, offering income opportunities, especially in rural and agricultural
- Reduced Post-Harvest Losses: In agriculture, solar dryers can help reduce post-harvest losses by enabling farmers to preserve surplus produce and extend its shelf
What products can you dry in a solar dryer in Kenya?
Solar dryer can be used to dry a vast number of agricultural products like:
- Berries like coffee berries, straw berries
- Fish, fingerings (omena)
- Cereals or grains like
- Herbs like rosemary, parsley, sage, thyme, mint
- Vegetables like kales, cabbages, onions, chilies, peppers
- Fruits like Tomatoes, mangoes, pineapples, grapes,
- Flowers like pyrethrum
- Meat and dairy products.