Ulsan National Institute of Science and Technology (UNIST) research team has achieved significant breakthroughs in harnessing low-grade heat sources (<100° C) for efficient energy conversion.

The research team is jointly led by Professor Hyun-Wook Lee and Professor Dong-Hwa Seo from the School of Energy and Chemical Engineering at the Ulsan National Institute of Science and Technology (UNIST), in collaboration with Professor Seok Woo Lee from Nanyang Technological University in Singapore.

The study findings have been published ahead of their official publication in the online version of Advanced Materials. Their groundbreaking work focuses on developing a highly efficient Thermally Regenerative Electrochemical Cycle (TREC) system capable of converting small temperature differences into usable energy.

Conventional energy-harvesting systems face challenges when it comes to effectively utilizing low-grade heat sources. However, TREC systems offer an attractive solution as they integrate battery functionality with thermal-energy-harvesting capabilities. In this study, the research team delved into the role of structural vibration modes to enhance the efficacy of TREC systems.

Schematic showing the different mechanisms of a battery and TREC system. Whereas the battery system (left) loses some of the stored energy as unusable energy, the TREC system (right) can convert low-grade waste-heat energy into electrochemical energy during battery cycling. Image Credit: Ulsan National Institute of Science and Technology. Click either the press release link or try the study paper link as its not behind a paywall at posting.

By analyzing how changes in covalent bonding influence vibration modes – specifically affecting structural water molecules – the researchers discovered that even minute amounts of water induce strong structural vibrations within cyanide ligands’ A1g stretching mode. These vibrations substantially contribute to a larger temperature coefficient (ɑ) within a TREC system. Based on these insights, the team designed and implemented a highly efficient TREC system using a sodium-ion-based aqueous electrolyte.

Professor Hyun-Wook Lee explained, “This study provides valuable insights into how structural vibration modes can enhance the energy-harvesting capabilities of TREC systems. Our findings deepen our understanding of Prussian Blue analogs’ intrinsic properties regulated by these vibration modes – opening up new possibilities for improved energy conversion.”

The potential applications for TREC systems are vast, particularly in wearable technologies and other devices where small temperature differentials exist. By effectively capturing and converting low-grade heat into usable energy, TREC systems offer a promising pathway towards the development of next-generation secondary batteries.

This research has received support from the 2023 Research Fund of UNIST, Individual Basic Science & Engineering Research Program, and the National Center for Materials Research Data through the National Research Foundation (NRF) of Korea, funded by the Ministry of Science and ICT (MSIT).


Its true that the energy lost to fuel and energy use in the low temperature range is huge. Its a vast resource in need of ever more research, The catch is the recovery of the energy needs to be done at very low cost and in a simple fashion.

This team may have just cracked open the pot of gold in low temp energy with a inclusion of a battery in the apparatus.

This looks like a new perspective on the harvesting in the lower temperatures. There looks to be quite an opportunity here, and the technology has just been born.


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