In the 1990s the automotive industry switched from environmentally damaging R-12 air conditioning refrigerant, typically referred to as ``Freon,'' to the more benign R134a refrigerant.
Now, under pressure from regulators, the industry is moving away from any fluorocarbon-based refrigerant toward using carbon dioxide.
How it works
Carbon dioxide is abundantly available in the atmosphere, as opposed to the need to manufacture R134a. But the principle is the same-the compression and expansion of carbon dioxide in a closed system can chill hot air.
When a heat pump is added to the system, it also can be used to provide auxiliary warmth for the passenger compartment and control of window fogging.
A carbon dioxide air conditioning system requires a smaller amount of gas compared with conventional systems, enabling up to a 20-percent reduction in packaging size. These advantages would significantly benefit smaller cars and diesel vehicles.
Where to find it
Carbon dioxide systems have been demonstrated on concept vehicles and advanced technology efforts, such as the Toyota FCHV-4 fuel cell vehicle. Also, Denso Corp. is working with DaimlerChrysler A.G. on a system for an unspecified Mercedes-Benz vehicle and with other car makers. Suppliers predict such systems will be widely used by mid-decade.
The primary challenge to using carbon dioxide would be retrofitting existing systems. The size of carbon dioxide molecules and the system's higher operating pressures rule out the adaptation of existing hydrofluorocarbon systems.
Alternative refrigerants under investigation include air, propane and a hydrofluorocarbon variant known as R152a.
Thus far, the primary suppliers of carbon dioxide systems include Denso, Visteon Corp., Delphi Corp., Behr GmbH & Co. A.G. and Modine Manufacturing Co.