The principle of the solar dehydrator is very simple: a box at the bottom heats up the air which then rises and flows through the second box.
We bought some wood (having nothing suitable lying around) and some black paint, and a friend donated a sheet of perspex. Two boxes of similar size were then made.
Making the Heat Box
Holes were drilled in opposite ends of the first box, the inside of which was painted black (to absorb more heat) and the perspex was attached on top – although anything clear would do for the job, from glass to thin plastic, as long as it is attached well.
Making the Drying Box
Holes were drilled in one end of the second box, with runners put around the inside to rest trays on, and a removable lid made to allow air to pass through.
Joining the Two Boxes
The two boxes are joined with the heat box angled and the drying box flat, with a airflow conduit between them to ensure airflow goes where it is meant to.
The great thing about this design is that it works on fairly dull days – and if it's showery, a cover over the drying box should stop the contents getting wet. (It probably won't work well if it's overcast and humid as the water from the fruit will have nowhere to go and so may go mouldy.)
This design can be made to what ever dimension you require. My one is about 45cm2 (18in2) and has enough room for two tier drying trays.
And best of all it only cost £15 to make, although if you have some materials handy it could cost less or nothing.