I like the ideas to use an electric AC compressor / system.
Here are some crazy ideas how to power this, dreamt up when driving my
Westy across the Idaho desert 3 weeks ago;
- it was 109F outside and at least that inside
- I could not run my (fully functional) Westy AC as it pushed the engine
temperatures too high
(stressful!! - regulating your speed based on keeping one eye on the engine
temperature gauge...)

In the resulting heat induced craziness I cooked up the following
- Electric AC unit driven from a lithium battery pack
Nissan Leaf battery packs are available from electric car conversion
suppliers
- A 500Wh 4 cell battery costs just $129 (weight 7lbs)
- that's enough juice for ~1 hour of AC operation
6 - 10 of these might be enough for a day's driving
Install them under the floor, they are thin & that's not much weight
(A). Recharge them with shore power at night
(B). Recharge them from 3 full size Solar Panels on the Roof
- 180 - 200W each makes enough Power for the AC

Thankfully my Westy, my wife and I survived that impossible heat & once my
brain had returned to normal temperatures I decided my lower cost solution
for the future is to avoid places that hot....

Mike Hart
'87 2WD Westy "T3WESTY" (stock 2.1l engine with 195k miles)
Palo Alto, CA