We will employ a mixed mode dryer in which air, heated by the sun through the glass, flows up to dry the products. This method is slower than direct drying but ensures homogeneous color of the product. It is also passive, therefore requiring no extra energy input. The solar collector heats the air through the glass by using the black metal to absorb the solar radiation. The heated air is lighter and flows by itself into the wood cabin, drying the products in the metal trays. One cabinet can host up to five piled trays of variable sizes (on average 1x1m). The damp air exits the system at the top of the wood cabinet. Fruits with low water content (banana, mango) and vegetables remain around 72h to dry. Fruits high in water content such as tomato or papaja, take longer to dry.
The solar collector must be well insulated; storage material may be used to maintain the heat. In the construction of our dryers, we aim to include a cheap and available storage material, such as sand. The system must be able to move from one place to another to find the optimum position for the solar radiation, throughout the day and year-round. Therefore small wheels are included. These type of solar driers can still be scaled up to larger capacity.
The system starts when one group of users or one user has available dried products or require dry products. A simple SMS is sent to require or offer a product. This message goes through a computer that uses internet to access satellite-transferred data and it is stored on a database. The database allows to gather information about the consumption and production of dried products. The message sent is received (either in its initial state, translated, or otherwise manipulated) by another group of users/another user, who can answer back. This procedure allows to generate and efficient long-distance, off-grid market.
We were inspired by the work of already existing organizations, offering such information/ connection services through SMS to farmers and inhabitants of remote areas already for many years, such as Text To Change, Frontline Technologies, and WeFarm.
In order to ensure preservation of the drying products, both in terms of humidity content and hygene, we would like to provide the farmers or cooperatives with the following:
a) re-usable, sealable boxes with lid; for stock keeping and exchanging/ selling in large quantities
b) hand-operated sealing machines to seal airtight plastic bags (with heat). The hand-operated sealing machine requires electric supply (250 - 750 Watt depending on the model and size), therefore the driers combined with solar panels would provide the required energy. That way, farmers can package their products easily and safely also for medium-scale distribution.