So, in my search for air conditioning options I've come across a couple sites selling battery-powered units for trucks: Arctic Breeze and Cruise N Comfort. They are marketed as a solution for idle-free zones to keep things cool without running an engine. They run on 12 or 24 volt DC power. They are smaller units, running 7,000-12,000 BTUs depending on what you get, but I imagine with proper insulation one or two of these would do the trick, and that being DC they would be much more efficient.
The other thing that I like is they function like the mini split systems that have been discussed here but they are specifically designed for vehicular applications, so I imagine they may be a bit more robust.
Just yesterday I noticed a Semi truck with one of these condensers mounted on the back of the cab, so I know they're out there, but I can't seem to find a lot of reviews or opinions on them. Anybody here have any knowledge, experience or opinions in this area?