A "standard reference thermoelectric module (SRTEM)*" for objectively measuring thermoelectric module performance has been developed in Korea for the first time. A research team led by Dr. Sang Hyun Park at the Korea Institute of Energy Research (KIER; President Yi, Chang-Keun) developed the world's second standard reference thermoelectric module, following Japan, and improved its performance by more than 20% compared with existing modules, demonstrating the excellence of Korea's homegrown technology.
* SRTEM (Standard Reference Thermoelectric Module): A reference standard used to check the status of output‑measurement instruments and calibrate their measurement errors prior to thermoelectric module measurements.
A thermoelectric module is a device that generates electricity by creating a flow of electrons driven by a temperature difference, with one side becoming cold and the other becoming hot. Conversely, when an electric current is applied to a thermoelectric module, one side cools down while the other side heats up. Thanks to these characteristics, thermoelectric modules are widely used in applications such as compact camping refrigerators and electronic equipment including computers. In addition, because they are environmentally friendly and well suited to miniaturization, they can be broadly applied to emerging fields such as carbon-free power generation and the space industry, which have recently drawn significant attention.
However, technological progress was slow due to the lack of methods to objectively and accurately measure the performance of thermoelectrical modules. In particular, the only standard reference thermoelectrical module for correcting measurement-equipment errors was the one developed in Japan.
To address this issue, researchers at KIER improved upon the limitations of the existing standard reference thermoelectrical module and developed a thermoelectrical module that is more suitable for calibration. The standard reference thermoelectrical module developed by the team achieved more than a 20% improvement in key performance indicators such as output voltage compared to the existing module, and it demonstrated excellent reproducibility by maintaining its output without degradation even after more than 300 operating cycles.
The research team used a metallic material instead of the commonly used semiconductor powder–based material. Semiconductor powder can produce a large output voltage even with a small temperature difference, resulting in high thermoelectric performance (Seebeck coefficient)*. However, during powder-based fabrication, the particle size and performance vary from batch to batch, making it unsuitable as a standard for calibration. In contrast, metallic materials offer relatively uniform and stable performance, making them well suited for a standard thermoelectrical module. The challenge, however, is that their thermoelectric performance is much lower about one-tenth that of semiconductor powder–based materials (BiTe based materials).
* Thermoelectric performance (Seebeck): An indicator of a thermoelectrical module's performance, defined as the amount of voltage generated when a temperature difference of 1°C is applied.
To enhance the performance of the metallic thermoelectric material, the research team developed a new thermoelectric leg* structure in a "hollow hourglass" shape. The narrowed waist and the hollow region increase thermal resistance, thereby enlarging the temperature difference between top and bottom sides of the leg and boosting the output voltage. When the newly developed thermoelectric legs were applied, the output voltage was found to be more than about three times higher than that of conventional rectangular-prism–shaped thermoelectric legs.
* Thermoelectric leg: A single small pillar that makes up a thermoelectrical module. It is located between the hot side and the cold side of the module and is responsible for converting heat to electricity (and vice versa).
In addition, the team investigated optimal combinations of metallic materials and fabricated two types of thermoelectric legs: Chromel–Constantan and Chromel–Alumel. Among them, the Chromel–Constantan thermoelectric leg achieved an output voltage 23.6% higher than that of previous standard calibration thermoelectrical module, and it maintained the same output even after more than 300 operating cycles.
Dr. Sang Hyun Park, who led the study, stated, "This work establishes an important technical foundation that could enable Korea to secure an advantage when international standardization of the standard calibration thermoelectrical module moves forward." He added, "In 2026, we plan to expand the scope of the research and further enhance its completeness by conducting cross-performance evaluations with leading research teams in Germany and Japan."
Meanwhile, this study was conducted with support from Korea's Ministry of Trade, Industry and Energy (MOTIE), and it was selected as the cover article for the September issue of the internationally renowned journal ACS Applied Materials & Interfaces (IF 8.2).
