Soler cookers are a great way to prevent deforestation due to use of firewood. Using aluminum from chocolate tabs seems like a great way to repurpose the byproduct of this industry that has otherwise limited benefits.
What I would extend this effort with, are rocket-stoves, which minimize the use of wood, without completely eliminating the use of wood. This would take care of the need of cooking high-heat dishes, which the soler cookers are not too good at.

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