ac - the big challenge

What is the most efficient way of storing energy to cool the car?

with iced water?
http://www.swampy.net/iceuse.html#anchor107358

this suggests that vehicle ac is innefficient

http://www.glacierbay.com/Darphtm.asp

I think that direct drive may be the way to go with the AC setting defining the speed of the compressor motor.

maybe a motor like this?

http://www.cloudelectric.com/inc/sdetail/214

or if this is big enough -- controller is only $25
http://www.cloudelectric.com/inc/sdetail/215

I really need it at 72V though - initially I should probably try to run an accessory bel