Researchers from the Korea Electrotechnology Research Institute (KERI)-Drs. SuDong Park, Byungki Ryu, and Jaywan Chung-have formulated a new approach to thermoelectric efficiency and engineered a high-efficiency, multistage thermoelectric power generator module. This development has implications for the performance of Radioisotope Thermoelectric Generators (RTGs), key power sources for space probes, and has caught the eye of the German Aerospace Research Institute.
RTGs have long served as reliable power generators in various space applications, including space probes and rovers. Using radioactive isotopes like plutonium-238 and americium-241, RTGs generate substantial heat, usually ranging between 400-700 degrees Celsius, inside a sealed vessel. The critical innovation lies in the capability to directly convert this thermal energy into electrical energy, particularly valuable in the unforgiving thermal conditions of space.
Two core components define RTG technology: the Radioisotope Heat Unit (RHU), which uses radioactive isotopes for heating, and the thermoelectric power generator module, responsible for transforming this heat into electrical energy. While the international community closely regulates RHU development, South Korea's proficiency in crafting thermoelectric modules has achieved international competitive standing.
The typical RTG employs thermoelectric modules featuring a layered arrangement of thermoelectric materials. Each layer is optimized for maximal efficiency within specific temperature ranges, transitioning from the hot side to the cold side. This multistage design is paramount due to the varying efficiency of thermoelectric materials at different temperatures. KERI's research has effectively designed, synthesized, and analyzed such a multistage thermoelectric module.
The KERI team first scrutinized the limitations of the 'dimensionless thermoelectric figure of merit (ZT)', a conventional academic metric for assessing thermoelectric performance. Armed with a newly formulated efficiency model and a vast set of thermoelectric data, the researchers can accurately predict the performance of over 100 million thermoelectric semiconductor stack configurations. This design and evaluation process has been expedited several hundred times by utilizing the thermoelectric device design program, pykeri.
The fabricated multistage modules displayed a heightened efficiency exceeding traditional single-stage modules by over 3% for temperatures above 500 degrees Celsius. These modules can consist of two to four layers, fitting within a minimal height of just a few millimeters, making them both more efficient and compact compared to existing solutions. This advancement has significant implications for the space auxiliary power market, notably for small satellites and exploration rovers, and has garnered attention in the commercial sector as well.
SuDong Park from KERI commented, "We are the first institute in Korea to conduct thermoelectric power generation research and have a long history and abundant source technology and practical data. This achievement is the culmination of convergence research that incorporates mathematics and physics into materials science."
Pawel Ziolkowski, Deputy Head of a group of Thermoelectric Functional Materials and Systems at the German Aerospace Center, noted, "The module technology developed at KERI is excellent when compared internationally. The achieved level of technological maturity provides the best conditions for the development of new RTG-based energy systems for space exploration."
The KERI team sees potential for their breakthrough beyond the realms of aerospace and defense, in areas such as industrial waste heat recovery, communication equipment cooling, and electric vehicle battery temperature regulation. To that end, they are actively seeking to bolster collaborations with relevant organizations and companies.
KERI operates as a government-funded entity under the National Research Council of Science and Technology of the Ministry of Science and ICT.