Regenerative AC sounds like a good idea. I always think why do the auto-manuf. never bother to insulate the passenger cabin more properly, glass with lower conductivity that would allow smaller more energy efficient units in the cars. Passive cooling is an interesting idea I read about.
Vehicle cooling systems
L.E. it is appalling to think that the few cubic feet of cabin space in a passenger car which are 10's of times less than the size of 1 room require such vast amounts of Watts to keep it cool..