Using the sun’s power

During fruit season farmers have more fruits than they can ever eat, while out of season there are only very few fruits available. So we at Bio Gardens are looking for ways to preserve the fruits, and one possibility for that is drying them. The process of drying plants – or parts of them – is one of the oldest methods to store food and medicine for future usage. Dried fruits can last for about three months because all the water inside the plants is extracted which prevents bacteria and fungi from multiplying. Furthermore, by drying the fruits their fermentation is significantly slowed down.
K1600__1560016For the drying process we decided to use a renewable and sustainable source: the sun which shines in Kasese almost every day. To make the drying process gentle, i.e. ensuring the nutrients and vitamins aren’t destroyed we needed to construct an efficient solar dryer. Because an efficient dryer reduces the drying duration compared to just drying fruits and plants openly in the sun. If the drying process takes more time, more medicinal relevant molecules can be destroyed by direct sunlight.

K1600__1560109How the dryer works:
The dryer, which is 2m long and 1m wide, is divided in two parts: let’s call it the front part and the back part. Inside the front part, the surface on the bottom needs to be black (we used black plastic foil) in order to absorb the sunlight and therefore to heat the air in the dryer. In the back part we have removable grids that we load with fruits and plants before putting them in to dry. The headpiece next to the front part has a hole with a small fan run by a solar panel. This fan causes a soft airstream which blows the hot air that’s been building up above the black surface over and underneath the fruits and plants. This way, the fruits and plants are dried gently and steadily in constant temperature. At the rear end (behind the plants) the dryer is open so that the air can flow. The moisture from the plants condensates and is transported outside the dryer.  So there is a constant air circulation making the drying process gentle and efficient.
All open parts of the dryer are covered by mosquito nets so that no insects can come in. The whole dryer is covered by a transparent plastic foil that causes a so-called greenhouse effect, keeping the heat inside the dryer.

K1600__1560723Now we are ready to dry fruits like Jack Fruit but also medicines like Artimesia or other plants. The drying for Jack Fruits takes up to two to three days when the dryer is outside for ca. 6 hours per day, depending on the amount of sunshine.

At Bio Gardens, we have built a second solar dryer and are going to construct a third one now to make most of the abundance of the fruit season.

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