The Shanghai Institute of Ceramics has made progress in the research of thermoelectric devices.

Shenjia Hydraulics

Release time:

2020-09-21

Thermoelectric power generation devices utilize the Seebeck effect of semiconductor materials to directly convert thermal energy into electrical energy, and can be applied in fields such as specialized space power sources and industrial waste heat recovery. In practical applications, conversion efficiency and power density are crucial technical indicators for thermoelectric power generation system design. For a long time, research on thermoelectric devices has focused on maximizing device energy conversion efficiency, while another key performance parameter—power density—has been largely overlooked. Developing thermoelectric power generation devices that simultaneously boast both high conversion efficiency and high power density—the so-called “dual-high” devices—has become a critical step toward advancing the practical application of thermoelectric power generation technology.

The Shanghai Institute of Ceramics has made progress in the research of thermoelectric devices.

Thermoelectric generators utilize the Seebeck effect of semiconductor materials to directly convert thermal energy into electrical energy, and can be applied in fields such as specialized space power sources and industrial waste heat recovery. In practical applications, conversion efficiency and power density are crucial technical indicators for thermoelectric generator system design. For a long time, research on thermoelectric devices has focused on maximizing device energy conversion efficiency, while another key performance parameter—power density—has been largely overlooked. Developing thermoelectric generators that simultaneously boast both high conversion efficiency and high power density—the so-called “dual-high” thermoelectric devices—has become a critical step toward advancing the practical application of thermoelectric generation technology.

The traditional research approach for thermoelectric materials and devices involves optimizing material properties to obtain thermoelectric materials with the highest thermoelectric figure of merit, zT, and then designing device structures based on these materials in order to achieve optimal conversion efficiency. This research paradigm separates material optimization from device design into two independent stages: material research focuses on attaining a high zT value, while device research leverages materials with the highest zT value to strive for maximum conversion efficiency. Since the electrical and thermal transport properties corresponding to materials with the highest zT value are typically fixed and unchanging, and since the device structural parameters that correspond to maximum conversion efficiency differ from those that yield maximum power density, it becomes impossible to simultaneously achieve both the optimal power density and the optimal conversion efficiency within the same device. In practical applications, in order to attain high conversion efficiency, one must sacrifice some power density, which in turn limits the applicability of thermoelectric devices.

Recently, a team led by Researcher Li-Dong Chen and Senior Engineer Sheng-Qiang Bai from the Shanghai Institute of Ceramics, Chinese Academy of Sciences, in collaboration with Professor Tie-Jun Zhu from Zhejiang University, proposed a reverse design strategy guided by "device design" to "material optimization." By adopting the criteria of "power-factor priority" and "thermal conductivity matching," they achieved "dual-high" performance in their devices. Based on this strategy, finite simulation was used to determine the optimal ranges of thermal conductivity and power factor for n-type and p-type half-Heusler materials required for dual-high devices. According to these results, by adjusting the carrier concentration in the n-type material, they obtained the optimal power factor as well as thermal conductivity that matches the p-type material. Without using thermoelectric materials with the highest zT values, the device achieved a maximum conversion efficiency of 10.5% and a maximum power density of 3.1 W/cm² at a temperature difference of 680 K, simultaneously breaking the record for both conversion efficiency and power density in single-stage thermoelectric devices. This reverse design strategy has shifted the traditional research approach, which solely pursued high zT values and high conversion efficiency in thermoelectric materials and devices, providing a new pathway for the design and development of practical, high-performance thermoelectric devices that can be widely applied to other thermoelectric material systems. The relevant findings were published in Joule, 2020, doi: 10.1016/j.joule.2020.08.009.

This work was supported and funded by the National Key Research and Development Program, the National Natural Science Foundation of China, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences. Xing Yunfei, a direct doctoral student from the class of 2015, and Associate Researcher Liu Ruiheng are co-first authors.

Thermal conductivity-matched design for “dual-high” thermoelectric devices. (a) Plots showing the relationships among the estimated thermoelectric figure of merit, power factor, thermal conductivity, and carrier concentration. (b) Using the results from plot (a), calculate the maximum power density and maximum conversion efficiency of the device.

Comparison of the maximum conversion efficiency and maximum power density of dual-high-performance devices with the performance of previously reported single-stage and cascaded thermoelectric devices (excluding single-arm or single-couple elements).

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