Electric vehicles are increasingly gaining prominence and popularity worldwide owing to their benefits like convenience, low operation costs and safety. Most importantly, this new concept in the world of the automotive industry is perceived as one of the most effective strategies for improving air quality and reducing carbon footprint because pure electric cars produce no emissions and promote the use of renewable energy sources. In particular, research on the application of lithium-ion batteries (LIBs) in electric cars is at the advanced stage. Although LIBs have several advantages like long service life and high energy density, they are sensitive to high temperatures. High operating temperatures like that experienced during hot weather and extreme driving conditions attenuate the battery life leading to thermal runaway. Maintaining the battery operating temperature within the specified limits during charging and discharging is a big research challenge but of great significance in improving battery efficiency, safety and service life.
Effective battery thermal management systems (BTMSs) could improve the overall performance of batteries used in electric cars. Current BTMS are mainly based on active and passive cooling strategies that fail to meet the thermal requirements of electric vehicles under extreme operating conditions due to their inadequacies and practical limitations. Hybrid thermal management schemes are a promising approach for overcoming these challenges as they combine the advantages of various active and passive thermal management strategies. However, hybrid BMTS is influenced by many complex parameters making its design and optimization a difficult problem. Therefore, analyzing and optimizing the sensitivity of these influencing parameters is crucial for improving the thermal management performance of the systems. This is quite challenging considering that the suppression of both battery heat dissipation and the propagation of thermal runways is not fully clarified.
Herein, Professor Weixiong Wu and Mr. Ruixin Ma from Jinan University together with Professor. Wencan Zhang, Mr. Zhicheng Liang and Mr. Guozhi Ling from Foshan University proposed a new hybrid thermal management system for LIBs used in electric vehicles based on liquid cooling, phase change material (PCM) and heat pipe. A reliable and more accurate numerical heat transfer model was developed and validated through experiments involving the analysis of the battery temperature distribution. Also, the authors constructed a surrogate model of the system using the Adaptive Kriging-High dimensional model representation (HDMR) to analyze the global sensitivity of the influencing factors and optimize the hybrid system design. Their work is currently published in the International Journal of Heat and Mass Transfer.
The authors findings revealed that the temperature difference and maximum temperature of the battery system were significantly influenced by four parameters: heat pipe length, PCM thickness, the velocity of the inlet water and the thermal conductivity of the PCM. Compared to the original design, the optimized thermal management system exhibited the best heat dissipation performance owing to its ability to maintain a uniform working temperature within the required limits. The charging-discharging profile recorded the lowest temperature difference and a maximum battery temperature of 30 °C. Also, the optimized system could prevent thermal runaway propagation under extreme operating conditions. Furthermore, the contradiction between the heat insulation and heat dissipation of the hybrid thermal system was clarified
In summary, the authors successfully reported the design and sensitivity optimization of a hybrid BTMS for electric cars based on a surrogate model. Overall, the optimized system demonstrated superior performance to the original designs in terms of its efficient heat dissipation capabilities, which significantly reduce the potential risk of thermal runaway propagation. Concerning the prominent performances of the optimized BTMS, Professor Weixiong Wu, in a statement to Advances in Engineering, stated that their findings will advance the engineering design and optimization of BTMSs for application in future electric vehicles.
Zhang, W., Liang, Z., Wu, W., Ling, G., & Ma, R. (2021). Design and optimization of a hybrid battery thermal management system for electric vehicle based on surrogate model. International Journal of Heat and Mass Transfer, 174, 121318.