Optimal and Efficient Thermal Management and Cooling Systems

Over the last few decades, concerns over the dependence and price instability of limited fossil fuels as well as environmental pollution and global warming have encouraged researchers, scientists and engineers to conduct more proactive research on vehicles with alternative energy sources. Today, electric vehicles (EVs) are starting to replace their conventional counterparts, due to the recent improvements in battery technologies, as they offer diversification of energy resources, load equalization of power, improved sustainability as well as lower emissions and operating costs. Through this transition towards EVs, the vehicle-related problems are mainly composed of the battery and its performance. In order to achieve the most ideal performance, the discrepancy between the optimum and operating conditions of the batteries need to be reduced significantly, which requires the effective use of thermal management systems (TMSs). Since EVs have a wide range of battery characteristics, size and weight limitations, and variable loads, achieving the most optimal battery thermal management system design, configuration and operation play a crucial role in the success and wide adoption of this technology.

Indeed, the battery system for safety, performance (both power and capacity) and lifespan reasons should be stored in a controlled surrounding where the temperature is controlled and there is no risk of thermal runaway. For a single-cell it is quite simple, however for a module/battery pack, a battery management system (BTMS) is integrated.

According to foundational research, the BTMS should be equipped with four essential functions to ensure the right operation conditions of the battery pack:

• Cooling: due to inefficiency, battery cells will not only generate electricity but also heat. This heat should be moved from the battery pack when the battery temperature reaches the optimum temperature or even in advance. Thus, a cooling function is required in BTMS.
• Heating: in cold climates, battery pack temperature probably falls below the lower temperature limit. Hence, a heating function, such as a PTC heater, is required to assist the battery pack to reach the proper temperature range in a shorter time.
• Insulation: in extremely cold or hot weather, the temperature difference between the inside and outside of the battery pack is much larger than that in mild weather. Battery temperature will thus fall (cold) or rise (hot) sooner out of the proper temperature range. To prevent this, good insulation can slow down the falling or rise of battery temperature, especially when the vehicle is parked outdoors.
• Ventilation: Ventilation is required to exhaust the hazardous gases within the battery pack. In some systems, such as air systems, this function is combined with cooling and heating functions.

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