The function of a dehydrator is to dry food (fruits, nuts, seeds, vegetables, …) for conservation or food preparation purpose. It is a very sustainable solution since using sun energy and having a very low footprint with recycled materials.
The principle is relatively simple; a wooden box (drying chamber with trays) connected to a sun heating chimney.
Once again check the relative location of your dehydrator with the context. Here the summer and winter sun courses and the vegetation around which could cause shade are the main elements to take into consideration. Check as well the windy rains sector to avoid humidity on the drying chamber. This can be avoided having a vegetation wall (here giant bamboo in the back).
The sun heat the interior of the chimney through the glass. The hot air circulate then up into the drying chamber to dry food.
If you want your system to be efficient you need 2 additions to this design.
A wavy corrugated metal sheet to increase the heat exchange with the circulating air inside the chimney:
This will make a huge difference since the increased area of heat exchange will boost the temperature of the air flow.
The second feature to incorporate is 12 volts ventilators to speed up the airflow. You can get this into a computer hardware shop. The one in the photos cost 2 US$ each since they are second hand. It comes with a small transformer to 12 volts.
These 2 easy to add features will make the difference between a poorly design solution and a very efficient drying system. If you want to slow down the capacity of the system and monitor either the temperature or the air flow speed you can switch off the ventilators and/or remove the corrugated sheet (therefore they should be easily removable) and/or add a sun filter on the chimney.
Some precision on the air flow : the bottom of the chimney has a trap to manage the quantity of airflow going in and the chamber has a trap to manage the quantity of airflow going out.
You may put a kind of mosquito net inside the chimney to prevent insects like ants climbing to the chamber and protect the basis of the structure as well with ants traps. The airflow going up, there is usually no food smell attracting insects on the basis of the structure.