I had an idea similar to this that I don't think anyone has tried
yet.  Here's my previous old post on the subject:
Edward

 > I'd also like to have AC when I visit a campground in the
 > summer. I've seen the rigs to mount the window AC unit in the
 > passenger window or in the luggage rack. They seem to require more
 > setup/take down time than I'd ideally like. I do like the fact that
 > you just leave the whole thing at home in the cooler months.
 >
 > So here's my idea. Use one of those freestanding rolling AC units
 > that has air exchange hoses to connect to a window. Strap it in
 > place somewhere like behind the passenger seat. hook hoses to handy
 > window with DIY adapter plate. While camping it uses shore power--
 > easy. For driving it runs off an inverter connected to aux
 > battery. Here's my concept breakthrough: replace the AC compressor
 > on the engine with another alternator. They're cheap, even for an 80
 > or 100 amp model. 100 amps = 1200 watts. Should be pretty easy to
 > fabricate a bracket to mount the additional alternator. It will not
 > put much load on the engine when there is no load on it, or it's belt
 > could be removed in the off season.
 >
 > Questions/Ideas: Is 1200 watts enough to power an AC unit big enough
 > to cool a vanagon going down the road on a hot day? Or one parked in
 > the sun with the top up? I'm thinking some adjustable air deflectors
 > inside the van to direct the cool air toward the drivers when driving
 > or elsewhere when not. Maybe big flexible hose for that? Perhaps
 > the outside air heat exchanger could take advantage of ram air when
 > moving to improve efficiency?
 >