The automotive industry has taken an important step when the vehicle air-conditioning systems marketed in many countries are passing a refrigerant fluid has cluorofluorocarbones (CFC-12) to hydrofluorocarbons (HFC-134a) less harmful to the ozone layer .
However, in terms of fixed targets in the Kyoto Protocol and the marginalization of air conditioning systems Embedded, replacement of HFC-134a may represent a major challenge to reduce the gas emissions greenhouse effect: Indeed, HFC-134a a 1300 times greater impact on the global warming that has CO2 amount equal weight.
The operation of an air conditioner plays on the compression of a gas and its relaxation. A compressor compresses the hot gas at very high pressure which passes through a capacitor and an internal heat exchanger (which allows heat exchanges with the low pressure area) to be cooled and then passes into the pressure regulator. He leaves a liquid which allows the cooling of the passenger compartment by passing through the evaporator. The gas is then low pressure is accumulated in a capacitor before circulating in the heat exchanger and start the compressor for a new cycle.
The CO2 is a possible gas as a refrigerant for air conditioning systems as a replacement for HFC-134a in the near future. The use of CO2 notes several related difficulties in the pressure which must be employed to be used as refrigerant fluid. Indeed, the critical temperature of CO2 is lower than that of HFC-134 and its critical pressure is higher which forces the cooling system to operate in the most difficult conditions achieve. This involves more resistant materials, therefore heavier and more expensive, hindering the marketing of this type of system at present.
However, Denso, a Japanese equipment supplier, has 2002 team in the experimental vehicle from Toyota fuel cell with an air conditioning system has CO2.
The air conditioner can work to warm the passenger compartment, which is a non-negligible factor if we consider the development in the future of a fuel cell vehicles that do not have heat source (engine) as a heating.
Editor: Etienne Joly, Office for Science and Technology
Embassy of France in Japan