Increasing Electric Vehicle Driving Range by Incorporating an Innovative Thermoelectric Heat Pump Subsystem into R1234yf and CO2 HVAC Systems
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Abstract
Under cold operating conditions (ambient temperature of 20oF), the electric energy consumed to provide occupant comfort and system thermal management in battery electric vehicles (BEVs) can reduce driving range up to 40% compared to the baseline operation in a 75oF ambient temperature. In hot environments (ambient temperature of 95oF), BEVs can suffer a 15-20% driving range penalty from HVAC energy consumption compared to the baseline. Effective integration of newly designed thermoelectric (TE) systems that use available TE materials provide performance enhancement in both R1234yf and CO2 HVAC systems. This presentation discusses subsystem designs, design tradeoffs and performance gains. The TE subsystems utilize an integrated design with cycle and material fabrication advancements to improve the coefficient of performance (COP) and reduce the size of HVAC systems that operate with low global warming potential (GWP) refrigerants. In R1234yf systems, the TE subsystem can provide 20% improvement in COP over today�s system in hot environments as well as a 20% increase in system capacity. In heating, the TE subsystem provides 20 � 35% improvement in COP over the baseline system and 50 � 80% improvement in COP over positive temperature coefficient (PTC) electric resistance heating systems. In CO2 systems, COP in hot environments can be improved up to 50% while increasing capacity of the baseline system by 30 � 40% and reducing operating pressure by 10%. Employing a larger TE subsystem can increase COP and capacity further and provide a greater reduction in operating pressure. Increasing system COP in hot environments makes CO2 HVAC more competitive with R1234yf in cooling while providing at least 3 times higher COP in heating than R1234yf systems that employ PTC heaters.