A Study of the Effects of the External Environment and Driving Modes on Electric Automotive Air-Conditioning Load

Abstract

After driving power, the air-conditioning system is the main item of power load for electric vehicles. The air-conditioning load is not only affected by the external environment, but also by the driving modes. Moreover, the cooling load calculation is very different to that for buildings. This study develops an Excel-VBA-based air conditioning load calculation tool. Air-conditioning load calculation is based on inputs of ambient air temperature, wind speed, solar radiation, driving mode, and other parameters. The calculation also considers the vehicle’s shell structure and materials, glass radiation angle, low-e glass, occupancy, outdoor air, etc. Heat conduction, convection, and radiation are all considered in the calculation of the surface temperature of the vehicle’s shell structure. The calculated results agree well with the measured data and thus verify the developed calculation tool. In addition, the dynamic cooling load can be calculated when incorporating driving speed, GPS location, etc. An energy control strategy for different driving modes can be applied for dynamic cooling load. A variable speed compressor was studied for regulating the energy need of electric automotive air conditioning. It was found that occupant comfort can still be satisfied while reducing air-conditioning energy consumption, and hence prolong the driving range and battery life. It was found that when a five-passenger car has only a driver in the car, the control strategy can reduce the air-conditioning load by 11.2%. With further optimization of the compressor operation matching the cooling capacity, the compressor power consumption can save up to 52.8%.