The advantage that I see with starting with a pre-built rack like you have is that it's already on wheels and so it would be easy to move around. So raising it, or radically altering it in any way that makes it less mobile would be losing the best thing you've got going for you. Keep it mobile.
What if you were to simply make a hole somewhere at the bottom of the cabinet for your air intake, and add a vent at the top where the warm moist air would escape. Get an 8' length of 6 inch black plastic pipe (ABS) or a metal stove pipe (also black). The black color would be a heat sink/solar collector. Find an inexpensive solar powered fan that would fit into intake end of your 6" black pipe, and it would push air through the pipe and up into your dehydrator.
https://www.arrow.com/en/products/3254j2h3p/ebm-papst?utm_medium=cpc&utm_source=google&utm_term=&utm_campaign=US%20-%20Shopping
The vent on the top could be a rotating barn vent:
http://www.midlandhardware.com/113373.html?gclid=CKaRosujh9ECFUtNfgodP-8DkQ
As the wind blows, it would turn the vent and pull air through your
dryer. I'd buy a good one with ball bearings -- something that turns easily and moves a lot of air.
That's all it would take.
Because the fan is solar, when the sun is out, it would be pushing air through the pipe and past your drying food. And the vent would turn on its own with just a little bit of breeze.
The whole thing would disassemble in about 2 minutes, if that, and you could roll it into storage. Basically, it would be two pieces --- the drying rack and the black
feed pipe. You could easily glue the little solar powered fan right into the end of your pipe.