Many challenges are encountered in the development of an automotive exhaust thermoelectric generator (AETEG), and its performance degradation under prolonged, fluctuating operating conditions is one of them. In this study, bismuth telluride based thermoelectric (TE) modules assembled to an AETEG were tested for their performance under cyclic heat input. Three thermal cycling profiles with the maximum heat source temperature up to 350 °C were used. The open-circuit voltage (V_oc), voltage–current (V–I) characteristics, and power output at the matched load (P_max) were determined at regular intervals. TE modules delivering different V_oc and P_max depending on their location on the AETEG predominantly showed marginal variations in both the parameters after testing for 150 cycles. Under prolonged testing for up to 300 cycles, a couple modules showed decreased P_max due to their increased internal resistance (R_int). The average specific contact resistance measured in the TE leg–electrode joints of unicouples in the degraded module indicated that cold-side joints substantially contributed to the increase in R_int. The results of microstructural and compositional analyses revealed that the increase in cold-side joint contact resistance resulted from the thermochemical degradation of the interface between TE legs–Sn-Cu solder alloy. The poor streamlined flow in some parts of the segmented cooler plate resulting in high temperature at the cold side of the module appeared to be responsible for such degradation. The present study demonstrates the importance of thermal management on the cold side for the reliable performance of modules in the AETEG system.

在汽车排气式热电发电机（AETEG）的开发中遇到了许多挑战，并且在长期变化的运行条件下其性能下降是其中之一。在这项研究中，测试了组装到AEEEG的基于碲化铋的热电（TE）模块在循环热输入下的性能。使用了三个热循环曲线，最大热源温度高达350°C。定期确定开路电压（V _oc），电压-电流（V-I）特性和匹配负载下的功率输出（P _max）。TE模块提供不同的V _oc和P _max取决于它们在AEEEG上的位置，在测试150个循环后，两个参数的边际变化主要。在长达300个周期的长时间测试下，由于其内部电阻（R _int）增大，一对模块的P _max降低。在退化模块中，单对的TE腿-电极接头中测得的平均比接触电阻表明，冷侧接头实质上有助于R _int的增加。显微组织和成分分析的结果表明，冷侧接头接触电阻的增加是由于TE支脚-Sn-Cu焊料合金之间的界面发生热化学降解而引起的。在分段式冷却器板的某些部分中流线型流动不良，导致模块冷端处的高温似乎是造成这种降解的原因。本研究证明了冷侧热管理对于AETEG系统中模块的可靠性能的重要性。