A solar powered A/C would be a very neat trick
. I don't know how much energy an A/C takes, but I'd imagine they could use a very small, lightweight, inexpensive system for it, rather than trying to power the wheels. I'd imagine you could also use it for lighting, stereo, and other interior convenience options too. If they could integrate it into the body well, it would be almost no loss in aerodynamics other than slightly more frontal area.