Heat Control in Wheaton ATC Solar Dehydrator.

What are your thoughts on how we can control heat inside the Wheaton ATC solar dehydrator? For instance, say I wanted to dry herbs at a temperature not over 104 fahrenheit in order to keep specific nutrients intact. Is there a way to regulate heat?

This is an example I thought of- a lever that is actuated by temperature to open or close the the air flow based on air temp: https://orbesenteknik.com/more/window-openers/

But the concern here is that once it got hot it would just close air flow entirely.

Thoughts? Thank you.