Before I started making charcoal, I built a solar concentrator from plans (in French) that Lorin Symington supplied, and used it for all sorts of cooking and baking. It was called “Helios” and looked like this:
The design has evolved, and here is a report from Lorin on using the solar oven to make charcoal from coconuts, and for the processing of cashews.
https://gosol.solar/solar-charcoal-and-cashews?fbclid=IwAR3wu-o7bhIY_5-PEY_B2ILV3wbfzXBCZ4UqeDD6v7-npsNFMSjlTtmmDqk