Commercial Solar Dehydrators?

Hello to all.
I have been researching options for dehydrating...What I keep finding is some sort of electrical input, whether for a fan or some heating unit for commercial scale dehydrators.
We plan to be dehydrating about 9000 kg of fresh herb material every year and are searching for the most eco-friendly and economical options.

We were originally thinking to implement a down draft solar dehydrator (Mark Vander Meer), but are starting to decide against it, because of chances of mold or bugs/dust entering into the drying chamber.

After all the research i've done i find myself leaning towards a greenhouse type dehydrator, but am not so fond of using fans on each end.

If anyone has any ideas we would so greatly appreciate it

We are in Zone 9, Portugal. Summers are dry and hot, Fall and Winter can be humid and rainy

Thank you in advance for any input

What time of year do you need to dry stuff? Maybe in the dry season, you could just have a well screened rack with good airflow, and that would be enough. It would be enough here, where the weather is almost always dry. Or you could aim to have natural ventilation during the dry season and add fans only during the humid season.

Stephanie, have you looked at "hohenheim solar tunnel dryer" in your research? I am looking at something similar in scale to you and this is the best I have found so far.

I built a Appalachian state design , very disappointed with it.

Here is a link to a PDF file for building a hohenheim solar tunnel dryer:
http://www.ats.uni-hohenheim.de/_deutsche_site/projekte/_pdf/Guidance.pdf

I was thinking of building the Appalachian State design myself, for home-scale dehydrating. Could you elaborate on what you don't like about it, Ray? Thanks.

At night with the Appalacian State the dehydrator everything cools off in rehydrates because of the dEw. Additionally even during the day in my Michigan climate it never gets hot enough in there to properly dehydrate tomatoes certain products it works fine and others it doesn't and you have to monitor it during the day if it gets too hot it will burn some items so there are vents that you have to continuously open and close all in all I should've spent the money on a good electrical Excalibar dehydrator, because I spent way more money building it that I could've bought one for . And I basically have to use heat lamps to properly dehydrate anything especially at nighttime .