R.O.L.E. Foundation has been diligently doing seeds saving since the development of the permaculture garden in the beginning of this year. Saving seeds allows us to continue growing various types of plants in a self-sufficient way. When saving seeds, it’s important to dry them first to avoid rotting and make them last longer. This is why we build our own solar dryer at the end of July 2020.
What is a solar dryer?
Solar radiation used for drying is one of the oldest applications of solar energy. It was used since the dawn of mankind mainly for food preservation but also for drying other useful materials like cloths, construction materials, etc.
In contrast to sun drying, where the material is exposed directly to the sun, the solar drying method uses indirect solar radiation. The principle of the solar drying technique is to collect solar energy by heating-up the air volume in solar collectors and conduct the hot air from the collector to an attached enclosure, the drying surface. Here the products to be dried are laid out.
The solar dryer uses a relatively simple concept with basic principles such as:
- Converting light to heat.
- Trapping heat: Isolating the air inside the dryer from the air outside the dryer makes an important difference. Using a clear solid, like a plastic bag or a glass cover, will allow light to enter, but once the light is absorbed and converted to heat, a plastic bag or glass cover will trap the heat inside. This makes it possible to reach similar temperatures on cold and windy days as on hot days.
- Moving the heat to the materials (in our case, seeds).
To build the solar dryer, a broken playground climber was used. Some modifications were done such as adding wooden boards as drying surfaces and unused glass to cover the back part of the solar dryer. Thick plastic was put on the top of the climber. Finally, velcro was used to create “curtains” to open and close the plastic and easily place or take out the seeds. And voila! The solar dryer is ready!
So far, the solar dryer has been working well to dry various types of seeds such as chili, tomato, eggplant, sorghum, different kinds of beans, etc. It speeds up the process of drying, compared to the sun-drying technique. Like us, you also can easily make a sun dryer in your garden by reusing objects in our surroundings, just be creative!