In response to global warming and energy shortages, governments around the world, considering the low noise and zero emissions of electric vehicles, are incentivizing automakers to scale up investment in EV research and development, offering subsidies and tax breaks for the purchase of EVs in order to promote environmental sustainability and pursue low-carbon and energy-saving goals. Some countries, such as Norway and the Netherlands, have even taken the lead by amending their laws to ban the sale of gas and diesel engines by 2025. In Taiwan, the Executive Yuan has set a target of banning the sale of fuel vehicles by 2035, thus directly accelerating the development of EVs. Since 2015, when the number of EVs passed the million mark worldwide, the traditional transport market has been impacted by an annual sales growth rate of over 50%. However, despite the continued growth in the number of EVs worldwide over the past few years, the market for EVs is still quite limited compared to traditional fossil-fuel powered vehicles, with EVs currently constituting only 0.2% of the whole private transport market. In general, there are two major drawbacks to EVs: range and charging time. Comparing the Toyota Altis (2019 model), the best-selling car in Taiwan, with the Tesla Model 3, the world's highest-selling EV, the former has a range of around 750km while the latter 450km, a huge gap of 67% in range. The fuel vehicle takes less than 10 minutes to fill up the tank, compared to 30 minutes for the Tesla Model 3 to go from 20% to 80% even with the Tesla Supercharger developed in-house, showing the difference in time costs. The development of EVs will therefore focus on reducing charging times and boosting range, but both range and charging times are closely dependent on operating temperatures.


Tesla Electric Cars with up to 7,000 Batteries
In the case of the Tesla Supercharger, if the battery temperature exceeds 113.1°F (45°C) during charging, the protection mechanism is activated to reduce the input power by 25%, which directly leads to a significant increase in charging time; meanwhile, the temperature difference between the maximum and minimum temperature of the more than 7,000 18650 lithium-ion batteries in the car needs to be kept within 5°C to ensure the chemical stability of the li-ion batteries, all of which is associated with thermal engineering.

Author

Professor Wei-Keng Lin

Education｜Ph.D., University of Maryland

Occupation｜Professor, National Tsing Hua University 

Specialty｜Electronic package heat dissipation, Heat pipe, Loop heat pipes(CPL，LHP，PHP), Energy-saving design, Solar heat storage and cooling, Heat flow system, Cooling of electronic components, Two-phase flow, Heat transfer elements of artificial satellite and high-altitude flying object