Session: 17-01-01: Research Posters

Paper Number: 149159

149159 - Performance Enhancement of Thermoelectric Generators Integrated With Advanced Metamaterials Design for Waste Heat Recovery 

Introduction
Thermoelectric generation, particularly through solid-state thermoelectric generators (TEGs), is a viable clean energy solution that can convert low-grade heat directly into electricity using a temperature gradient. The advantages of TEGs include zero emissions producing electricity, no mechanical moving parts, easy miniaturization, fast response, and high reliability. These advantages make TEGs especially effective in harvesting dispersed and low-grade heat sources.
Typical TEGs are composed of multiple N-type and P-type semiconductor materials, which are connected electrically in series but thermally in parallel. This design enables voltage generation under a thermal gradient. In optimal operating conditions, the thermal gradient should be maintained as high as possible. However, in most application scenarios, the thermal gradient may decrease over time due to thermal conduction, resulting in a 70-80% drop in output voltage/power after stabilization. While active cooling is an effective method to maintain a high thermal gradient, it requires efficient cooling systems. Nonetheless, the energy cost of cooling is typically higher than the power gain.
Contributions
Integration of metamaterial in a heat sink can significantly improve the performance of TEGs. Compared with traditional designs with a plate-fin heat sink, TEGs equipped with a honeycomb metamaterial heat sink can maintain a higher thermal gradient without the need for active cooling, thereby contributing to higher output power.
In this study, the performance of thermoelectric generators is significantly enhanced through the use of a heat sink embedded with honeycomb metamaterials for waste heat recovery. The TEG equipped with a honeycomb metamaterial heat sink is able to maintain a high thermal gradient without the need for active cooling, thereby contributing to higher output power. This substantial enhancement paves the pathway for the widespread application of TEGs.
Methods
In this work, an experimentally validated finite element model is developed to predict the output power of TEGs with systematically varied metamaterial designs, named square, triangular, re-entrant, hexagonal honeycomb, and irregular design, each having total dimensions of 40mm(L)×40mm(W)×40mm(H). Key design factor of unit cell number is examined to quantify their effects.  
Results
It is found that introducing the honeycomb metamaterial design concept into the heat sink can effectively prevent thermal gradient loss in TEGs. Specifically, compared to TEGs with a conventional heat sink, the output power can be increased by 9.25-18.28%. Additionally, increasing the unit cell number of triangular and re-entrant metamaterial from 4×4×4 to 7×7×7 can further enhance the output power by 10.07-11.82%.
Conclusion
This research marks a pioneering effort in applying metamaterial design concepts to enhance passive heat sink performance within TEG systems. In this work, metastructure heat sink designs, including square, triangular, re-entrant, and hexagonal honeycomb, as well as irregular designs are considered. Their performance is evaluated through an experimentally validated finite element model.  The results indicate that honeycomb metamaterial heat sinks are more effective than traditional heat sink in mitigating the thermal gradient loss of TEGs. Specifically, a TEG with a triangular honeycomb design can increase the open-circuit voltage and output power by 8.15% and 18.28%, respectively, compared to the TEG with a conventional heat sink. Increasing the unit cell number from initial 4×4×4 to 7×7×7 can lead to an additional 10.07-11.82% enhancement in power output. Conclusions from this study can serve as useful design guidelines for future TEGs, providing valuable insights into optimizing efficiency, durability, and overall performance.
 

Presenting Author: Ya Tang Dartmouth College

Presenting Author Biography: Ya Tang is a Ph.D. student at Thayer School, Dartmouth College. He holds an M.S. degree in Chemical Engineering from Sun-yat Sen University. His research focuses on 3D printing, multifunctional materials design, high thermoelectric and piezoelectric materials/devices design, modeling, and fabrication.

Authors:

Ya Tang Dartmouth College
Bowen Huang Dartmouth College
Yan Li Dartmouth College