In an electric vehicle, a maximum cruising range is adversely affected by electric power consumption of auxiliary electric components for heating and cooling. Therefore, it is important for the air-conditioning to consume energy as efficiently as possible. This study describes how a proposed Occupied-Zone(OZ) HVAC system has attained a significant increase in the cruising range of an electric vehicle by air-conditioning occupied seats only.
The idea of OZ HVAC is to confine air-conditioning to occupied-zones only. The OZ HVAC has an option of selectively air-conditioning three zones corresponding to driver, passenger and rear seating positions, while a conventional HVAC system air-conditions a whole cabin regardless of occupancy in each zone, which results in more power consumption compared to the proposed idea. For example, when a cabin is occupied by a driver only, it is clear that the proposed OZ HVAC limits air-conditioning to the driver zone only and hence less energy consumption for unoccupied zones.
The OZ HVAC system has been developed in two steps. The first is modifying existing HVAC hardware so that each zone temperature and air flow rate can be controlled independently with a few additional control doors and the corresponding actuators.
The second is to develop a zone temperature control algorithm for the OZ HVAC. Thermal load for a zone, not a whole cabin, was estimated and verified by CFD and vehicle testing. And a new parameter for zonal control was defined as Zonal Energy Efficiency Ratio (ZEER) that represents zonal energy ratio to corresponding steady-state cabin energy consumption.
The new energy-saving OZ HVAC system was implemented in BlueOn, the Hyundai electric vehicle. It achieved improvement of 4 to 9 % in a cruising range while maintaining the same level of thermal comfort and reducing the HVAC blower noise compared to the conventional HVAC system. The prototype HVAC is currently under development and testing for further improvement. After its completion of development, the system will be applied to electric vehicles.