[Big Dave]

Low delta-T Rankine cycle machinery is A-OK in stationary applications where huge collectors and heat rejecters are possible. That doesn't sound like something usable on a car, particularly a small car. At a low delta-T, these equipment gets very large (and heavy and expensive) for the amount of power (air conditioning) produced. Just that pesky Second Law ofThermodynamics in action.

What might work on a bigger vehicle, like my F-350, is to get the smallest 12volt RV frig you can find and use it as a water chiller to provide cool water for a driver cooling vest/chaps. Fighter planes, particularly ground attack planes use these to efficiently cool the pilots.