Performance analyses of a novel free-cooling assisted air conditioning system applied to electrical vehicles

Air conditioning system of electrical vehicles7 consumes much electricity for cooling. Using natural cooling source could effectively reduce energy consumption and extend mileage. In this paper, cooling load characteristics of electric vehicles were analyzed considering influences of climate conditions, and energy saving potential of using natural cooling sources were investigated to provide guidelines for the design of efficient air conditioning systems. First, a typical electrical vehicle was designed as the studying object, and a numerical model was established to calculate vehicle's cooling load. Utilization ratio of natural cooling in severe cold regions, cold regions, and mild regions ranged from 36.7 % to 47.8 %, while the value was only 2.5 % in hot summer and warm winter areas. Then, a novel natural cooling assisted air conditioning system was proposed, and parametric studies were carried out to study energy-saving ratio and improvement of traveling hours. Average coefficient of performance of the novel system ranged from 4.47 to 6.08 with the air flow rate being 700 m3/h, and ranged from 5.78 to 7.71 with the air flow rate being 2000 m3/h. The values are 7.3 % to 65.8 % higher than the traditional air conditioning system. The electric consumption during cooling period could be reduced by up to 83.7 % in mild regions and by 24.9 % to 57.4 % in severe cold regions, cold regions, and hot summer and cold winter regions. Increasing setting temperature and enlarging air flow rate of the air conditioning system could effectively improve the energy-saving ratio. Traveling hours could be extended by 2.0 % to 15.8 %.