[Big Dave]

Thermoelectric cooling is very inefficient. COP of 0.4 or so.Your Rankine cycle AC is very efficient. COP of 3.0 routinely.

I have batted around the idea of using an adsoption machine for car AC. It would run off the exhaust and/or jacket water heat. Adsorption is also very inefficient (COP of 0.8 vs COP of 3.0 for Rankine cooling) but it has the virtue of being able to work OK with a very low temp heat input. Solar adsorption machines work A-OK with only 200 degree input heat. My thermstat is 203 degrees and my EGT (post turbo is in the 300 degree range.

Problem is that it is worthless until the vehicle gets warmed up enough to put out the requisite temps. So you have to retain the Rankine cycle unit. Also we now need ANOTHER condenser and it needs to be four times the size of the Rankine cycle condenser.

Doable, but a engineering problem.