Ink-based thermoelectric technology could be solution for replacing problematic refrigerants

Today’s refrigerants, which are specialized working fluids used in air conditioners, refrigerators and heat pumps, come with a host of issues including leakage, emissions concerns, flammability and limited reclamation of used refrigerants. However, a recent study by University of Notre Dame researchers describes a promising alternative for next-generation cooling using thermoelectric technology, which has no moving parts ad no gaseous refrigerants, allowing for zero leaks.

“By making thermoelectric devices a competitive and commercially viable technology, it can transform the way we cool things,” said Yanliang Zhang, Advanced Materials and Manufacturing Collegiate Professor of Aerospace and Mechanical Engineering at Notre Dame. “We can make the cooling process become very environmentally friendly.”

In the past, widespread adoption of thermoelectrics has been challenging due to the high costs associated with traditional manufacturing processes. However, the research team led by Zhang has developed an innovative ink-based printing strategy that enables a scalable manufacture of low-cost and high-performance thermoelectric materials and devices.

According to the new study, these materials “are very advantageous in energy-efficient and localized cooling of electronics, medical devices, automobiles, data centers and buildings.”

This research was primarily supported by the U.S. National Science Foundation (NSF) Environmentally Applied Refrigerant Technology Hub (EARTH), whose mission is to create the first sustainable refrigerant life cycle-engineered system. These advances pave the way for producing high-efficiency, compact cooling systems without the need for environmentally harmful refrigerants.

“These devices are highly effective in cooling and very conducive to large-scale industry manufacturing,” Zhang said. “We can make the devices faster and with less cost. I think the biggest advantage of our process is its simplicity.”

He continued, “We use blade coating or screen printing to directly convert the initial inks into the final device pattern, the same process as screen printers use for artwork on T-shirts. But our ink contains silver and selenium, which become the thermoelectric material after printing and post-print processing. We invented an ink that is highly compatible with the printing process, which allows for easy scalability.”

The results of the process create components for non-refrigerant thermoelectric coolers.

During the development process when the research team initially combined the silver and selenium elemental powders to make the ink, they discovered that the silver and selenium reacted very quickly to form the silver selenide alloy. “This fast chemical reaction speeds the manufacturing process, which can be more cost-effective,” Zhang said. The alloy ink composition was then further optimized between the two elements to achieve the maximum thermoelectric performances.

Upon testing and comparing with current state-of-the-art bulk materials available today, the optimized printed materials achieved competitive room-temperature performances for both P-type and N-type components. The team’s earlier research focused on the printed P-type thermoelectric alloy, whereas the newer silver-selenium alloy material is for N-type thermoelectric materials. Both P-type and N-type components are needed to make a thermoelectric cooling device.

“We are continuing to investigate how to transform high-performance material into high-performance devices. We want to discover how we can combine the P-type and N-type semiconductors, the metal electrodes, and then connect all the components into a final, complete system,” Zhang said. “We want to improve the material to the point that the heating, ventilation, air-conditioning and refrigeration industry will feel very confident to adopt it. Our goal is to bring our technology to the market to benefit all of society.”

In addition to the support from NSF EARTH, this study was also funded by the U.S. Department of Energy and another NSF program. Md Omarsany Bappy, a recent Ph.D. graduate from Zhang’s lab and assistant professor at Bangladesh University of Engineering and Technology, served as the first author on the paper, with contributions from other Notre Dame graduate students and postdoctoral scholars who led the machine learning and characterization aspects of the study. Tengfei Luo, the Dorini Family Professor for Energy Studies in the Department of Aerospace and Mechanical Engineering at Notre Dame; Mercouri Kanatzidis, professor of chemistry at Northwestern University; Berardo Matalucci; and Allen Gray at MIMiC Systems also contributed to this research. To learn more about NSF EARTH, please visit https://erc-earth.ku.edu.

Contact: Brandi Wampler, associate director of media relations, 574-631-2632, brandiwampler@nd.edu.