Heat pipe/phase change material coupled thermal management in Li-ion battery packs: Optimization and energy-saving assessment

To lower the energy consumption of Li-ion power battery packs thermal management, this paper investigates an improved heat pipe/phase change material coupled thermal management in a 55-Ah Li-ion battery pack, in which fans can be utilized to strengthen the air condensing effect of the heat pipe. The purpose of this paper is to optimize heat pipe/phase change material coupled thermal management and assess its energy-saving potential for long-time running. Based on the numerical calculation with a 2-dimension coupled resistance-capacity model, the role of phase change material is defined comprehensively, and a multi-cycle process is investigated for long-time temperature control stability. Further multi-objective optimization is conducted to minimize both thickness of phase change material and power of fans under the worst working condition. Finally, the energy-saving effects of optimized coupled thermal management under different discharge-charge conditions are assessed. Results demonstrate that phase change material is used to "shift load" during discharging and "fill valley" during charging, and the intensity of "load shifting" has been discussed. For long-time running, battery surface tem-perature fluctuates upward and then steadily when heat accumulated during discharging equals to heat-releasing during charging. Furthermore, it also shows that the maximum energy-saving rate reach up to 81.80% by active-passive thermal management. In conclusion, heat pipe/phase change material coupled thermal man-agement possesses considerable energy-saving potential after optimization and is promising to utilize in battery temperature control field with lower carbon emissions.