Annual Energy Consumption of Indirect Air Conditioning Systems for Electric Vehicles Using Alternative Refrigerants

Extended Abstract R134a refrigerant has been applied to air conditioning systems for automobiles. However, R134a with a global warming potential (GWP) of 1430 should be phased out based on the Kyoto Protocol. Furthermore, in 2017, the European Parliament passed a law banning sale and operation of all automobiles that use refrigerants with a GWP of 150 or higher. Thus, R1234yf with a GWP of 4 is being applied to the air conditioning system for electric vehicles. However, R1234yf is more expensive than R134a [1]. Furthermore, when the outside temperature is below -10 ℃, the evaporator decreases to the vacuum pressure and the heating performance of an air source heat pump is significantly degraded [2]. Therefore, R152a, R290, and R600a are considered as alternative refrigerants [3] that have a low GWP and excellent thermodynamic properties with a relatively low price. However, these refrigerants have not been considered as alternatives to R134a owing to safety concerns with high flammability. The stability of the flammable refrigerants can be ensured by applying an indirect air conditioning system. The indirect system avoids the driver's exposure to flammable refrigerants and the coolant circulates the vehicle cabin for cooling and heating. The objective of this study is to quantitatively analyze the annual energy consumption of an indirect air conditioning system using R134a, R152a, and R290. Based on cycle