Principles
General Principles-Customized solar dryer
Because drying removes moisture, the food shrinks and decreases in size and weight. Drying also preserves the food without need for refrigeration. Therefore it is ideal to do when the food is fresh and plentiful, to allow for consumption or sale later when it is less available or too expensive.So we can make Customized solar dryer.
How quickly the food dries is affected by many variables, especially the amount of sunlight and relative humidity. Drying time is also affected by type of food (water content), and thickness of slices. Generally speaking very wet foods like mango, pineapple and tomato will take two full days of solar heated drying. Some like apple, coconut, potato, onion etc. can be done in one day. Leafy products like herbs take only part of a day.
Yields of dried products are directly related to how much water is in the original product. 80 – 90 % of the moisture must be removed. 10 kg of sliced apples will yield about 1.6 kg of dried apples. 10 kg of onions will yield about 1.25 kg of dried onions. Very wet fruit like mango and tomato will yield about 1kg from 10 kg. When water is added to the dried product, it returns to its original size. This is done with many vegetables, but most fruits are good to consume in their dried form.
The Small-Farm model has three main features which enhance drying speed and efficiency. This compact configuration provides for:
How is Airflow working？
1• Horizontal airflow across the food is proven superior versus vertical airflow.
2• Solar air collector tilts to accommodate any latitude or season.
3• Entire dryer can swivel on a fixed table so operator can rotate unit to track the sun.
Large commercial dryers, or their solar air collectors, are unable to be rotated during the day to track the sun. This limitation also favors multiple small Millionsun units.
Drying rack total surface area is 5.1 sq. M, which is suitable for approximately 15 kg. of “wet” food, depending on water content, thickness of product, etc. Included 40-watt photovoltaic panel drives 4 DC circulation fans. The addition of an automobile battery in the circuit will allow airflow to continue while clouds pass or for some time after sunset.
Solar dryer,Workers with St. Lucia Ministry of Agriculture during FAO-sponsored Millionsun trials in early 2011. As a result of these trials, they requested 5 additional units.
