Aforementioned Air Conditioner came in wide use in late 20th century, but they consumed significant power of the vehicle. A/C will still cool if windows are kept open, but in order to ensure efficient cooling and reduce air drag windows are kept closed. Debate over A/C’s effect over fuel efficiency of the vehicle is still going – factors like engine power, aerodynamics and wind resistance are being made use of.
By 1960, about 20 % of all cars in US had an air conditioner and now nearly every car has an A/C. Coming to the Refrigeration Cycle implied in modern day A/Cs. Simply, the heat transported from passenger’s compartment enters environment which then enters the compressor which further enters the condensing coil (located near car’s radiator) which condenses the air and the air then enters expansion valves and then through the flash evaporation temperature is lowered, air then routed to evaporator, which then through the compressor passes the cooled air back into the compartment.
Evaporative Coolers were same as the desert coolers but just they were installed in cars and were less bulky. They were primarily seen in dry desert areas like Nevada, Texas, etc.
The modern automobile systems are expected to use up to 4 horsepower of the engine’s power thereby, might increase fuel consumption of the vehicle. Technologies like TIFFE (Thermal Systems Integration For Fuel Economy) and Sustainable Automotive Air Conditioning are being considered.