Efficient Low-Grade Heat Harvesting: An Innovative Approach for Energy Generation

Scientists from UNIST and Nanyang Technological University have built a Thermally Regenerative Electrochemical Cycle (TREC) procedure, offering a new systematic approach to transform low-grade thermal energy into practical energy. By understanding the relevance of structural vibration modes, especially in water molecules, this system demonstrates potential in enhancing energy conversion from slight temperature variances. Such developments in TREC systems could potentially transform the application of low-grade heat in wearable gadgets and secondary batteries.

Researchers have developed an innovative TREC system that effectively transforms low-grade thermal energy into practical energy, capitalizing on structural vibration modes. This innovation could potentially change energy conversion in wearable gadgets and secondary batteries.

The investigation team, co-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 conjunction with Professor Seok Woo Lee from Nanyang Technological University in Singapore, have made substantial progress in exploiting low-grade heat sources (<100 °C) for productive energy conversion. Their seminal work centers on developing a highly efficient Thermally Regenerative Electrochemical Cycle (TREC) system that can convert minor temperature differences into usable energy.

The traditional energy-harvesting systems encounter challenges when it comes to efficiently using low-grade thermal energy sources. However, TREC systems serve as an appealing solution as they incorporate battery functionality with thermal-energy-harvesting abilities. In this research, the team probed the role of structural vibration modes to augment the efficiency of TREC systems.

Through analysis, the researchers discovered how slight changes in covalent bonding impact vibration modes, specifically influencing structural water molecules, and found that even minimal amounts of water trigger intense structural vibrations within cyanide ligands’ A1g stretching mode. These vibrations contribute significantly to a larger temperature coefficient (ɑ) within a TREC system. Based on these revelations, the team devised and executed a highly efficient TREC system using a sodium-ion-based aqueous electrolyte.

Professor Hyun-Wook Lee explained, "This research offers valuable insights into how structural vibration modes can augment the energy-harvesting capabilities of TREC systems. It provides a deeper understanding of Prussian Blue analogs’ intrinsic properties influenced by these vibration modes, paving the way for enhanced energy conversion.”

TREC systems have vast potential applications, particularly in wearable technologies and other devices where minor temperature differentials are present. By efficiently capturing and converting low-grade thermal energy into usable energy, TREC systems present a promising avenue for the evolution of future-generation secondary batteries.

The research was supported by 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).