Not frying but drying
Solar dryers or also called food dehydrators can be used to dry fruits, vegetables, herbs and even meat. They have many advantages compared to conventional drying in the sun including increase of productivity, more hygienic, less labor intensive. There are many different models. The choice depend on desired capacity and drying speed and to less extend climate.
Options: Indirect dryers with different capacity.
Suggested program: Theory (2h), Construction (4h): Total 6 hours
Estimated material costs: 50-100 Euro, depending on capacity