Worldwide Electrical Energy Consumption of Various HVAC Systems in BEVs and Their Thermal Management and Assessment 2018-01-1190

Battery electric vehicles (BEVs) are equipped with Mobile Air Conditioning systems (MACs) to ensure a comfortable cabin temperature in all climates and ambient conditions as well as the optional conditioning of the traction battery. An assessment of the global electrical energy consumption of various MACs has been derived, where the basis of the assessment procedure is the climate data GREEN-MAC-LCCP 2007 (Global Refrigerants Energy & Environmental - Mobile Air Condition - Life Cycle Climate Performance) and the improved LCCP2013 (Life Cycle Climate Performance. The percentage driving time during 6 AM and 24 PM is divided into six different temperature bins with the solar radiation and relative humidity for 211 cities distributed over Europe, North, Central, and South America, Asia, South West Pacific, and Africa. The energy consumption of the MACs is determined by a thermal vehicle simulation. In this work, four different MACs are simulated and compared. The MACs that are investigated are two conventional refrigeration cycles with PTC (Positive Thermal Coefficient, one with R-1234yf and the other with R-744 as the refrigerant, as well as two heat pump systems, one with R-134a and the other with R-744. Taking into account the number of vehicle registrations and the average distance traveled per city, the average energy consumption per kilometer, the annual energy consumption per car, and the necessary energy for a BEV fleet for heating and cooling is estimated at city, country, continent and world level.

This study also deals with the optimization of mobile air conditioning systems based on the Evans-Perkins process. These systems are used for cooling the passenger compartment. Additionally, a reversible system can be used as heat pump system for providing passenger and battery heating. The required electrical energy for this process depends on the temperature difference in the system. The available heat sources are discussed as well as the control strategy and the optimization potential. Finally, a generic control structure for refrigeration cycles with the refrigerants R-744 and R-1234yf is presented, where the control structure depends on independent, gain-scheduled controllers. This results in a very flexible control structure. The R-744 heat pump system is an example of a moderately complex mobile air conditioning and heating system because of the increasing degree of freedom due to the temporary transcritical process control.