You believe a 20 mph wind blowing against a stationary pinwheel would have a different effect than still air and a pinwheel held out the window of the car traveling 20 mph?
“20 mph wind ... pinwheel”
Forget my last post which was wrong.
Either way - pinwheel moving, air stationary or air moving, pinwheel stationary, the air is cooled because energy is taken from the air and converted to electricity (assuming the pinwheel is driving a generator).