Waste heat is everywhere. Factories, power plants, engines, electronic devices, and even natural environments release large amounts of heat that often goes unused. If this wasted energy could be efficiently converted into electricity, it could provide an important source of clean and sustainable power.
A recent study by Choo and colleagues explores a promising way to achieve this goal. The researchers developed a new design strategy for thermoelectric power generation using copper selenide (Cu₂Se) and advanced 3D-printing technology. Their approach combines computer modelling with precise control over the material's shape and internal structure. The results show that changing the shape of thermoelectric materials can significantly improve their ability to produce electricity from heat.
The Untapped Potential of Waste Heat
Waste heat is one of the largest sources of unused energy in modern society. Industrial facilities, vehicles and power-generation systems can release substantial amounts of heat into the surrounding environment.
Instead of allowing this heat to escape, thermoelectric technology can convert a temperature difference directly into electrical energy. This process is known as the thermoelectric effect.
A thermoelectric generator normally has two sides: a hot side and a cold side. When there is a temperature difference between them, charge carriers inside the thermoelectric material move and generate an electrical voltage. The larger and better-controlled the temperature difference, the greater the potential for power generation.
However, achieving high performance is not simply a matter of finding a good thermoelectric material. The physical design of the device also plays a major role.
Why Shape Matters
Most thermoelectric modules are built using relatively simple cuboid-shaped legs. These conventional designs are practical, but they may not make the best use of available heat.
For thermoelectric materials to perform well, heat needs to be carefully managed as it passes through the material. The shape of the material can influence heat flow, temperature distribution and the temperature difference across different sections of the device.
Until recently, researchers have focused heavily on improving the intrinsic properties of thermoelectric materials. These include electrical conductivity, thermal conductivity and the ability to generate voltage from a temperature difference.
However, designing the material at a larger, macroscopic scale has been more difficult. Producing complex shapes from bulk thermoelectric materials can be challenging, especially when the materials need to operate at high temperatures.
This is where 3D printing offers a new opportunity.
Cu₂Se: A Promising High-Temperature Material
The researchers selected Cu₂Se, or copper selenide, as the thermoelectric material for their study. Cu₂Se has attracted attention because of its useful thermoelectric properties and potential for high-temperature applications.
But the researchers did not simply print Cu₂Se into a conventional shape. Instead, they investigated how its geometry could be redesigned to improve thermoelectric performance.
They used finite element modelling, a computer-based engineering technique, to study how different shapes would influence heat transfer and electrical output. This allowed them to test and optimize designs before producing physical samples.
The modelling helped the researchers understand how heat moved through the material and how different geometries affected the temperature difference across the thermoelectric legs.
The Power of 3D Printing
One of the most important aspects of the research is the use of 3D printing to create complex thermoelectric structures.
Traditional manufacturing methods can make it difficult to produce unusual shapes from bulk thermoelectric materials. 3D printing, however, allows researchers to build structures with carefully controlled geometries.
The team optimized both the 3D-printing process and post-treatment conditions. This was important because the manufacturing process does more than determine the external shape of the material. It can also influence the microscopic structure inside the material.
By carefully controlling these processes, the researchers were able to engineer both the macroscopic geometry and microscopic defects of Cu₂Se.
These microscopic features can affect how electricity and heat move through the material. Therefore, controlling them provides another way to improve thermoelectric performance.
The Hourglass Design Stands Out
Among the different structures investigated, the hourglass-shaped geometry produced particularly impressive results.
The narrow and wider sections of the hourglass structure help control the way heat moves through the thermoelectric leg. This design can create a larger and more useful temperature difference across the material.
According to the researchers, the hourglass geometry achieved the highest output power and thermoelectric efficiency among the designs studied.
This finding is significant because it demonstrates that improving thermoelectric devices is not only about discovering new materials. Changing the shape of an existing material can also unlock better performance.
The result suggests that future thermoelectric generators could be designed specifically around the heat source instead of relying on standard rectangular components.
A New Direction for Energy Recovery
The study offers an important lesson for the future of waste-heat recovery: materials and geometry should be designed together.
A highly efficient thermoelectric material may not reach its full potential if it is placed in an inefficient structure. Similarly, an innovative geometry will have limited value if the material cannot withstand the required operating conditions.
The combination of computer modelling, 3D printing and material engineering provides a way to address both challenges at the same time.
This approach could eventually help engineers create thermoelectric generators tailored to specific applications, including industrial waste-heat recovery, high-temperature energy systems and other environments where conventional energy-recovery technologies are difficult to use.
Towards More Efficient Energy Systems
The ability to convert waste heat into electricity has major environmental and economic benefits. Instead of releasing heat into the atmosphere, industries could potentially recover part of that energy and use it to generate additional electricity.
Although further research and development will be needed before such designs can be widely deployed, the work by Choo and colleagues represents a promising step forward.
The study shows how 3D printing can move thermoelectric technology beyond simple shapes and conventional manufacturing limits. By carefully engineering both the overall structure and the microscopic features of Cu₂Se, researchers can improve the temperature difference, output power and efficiency of thermoelectric devices.
Ultimately, the research points toward a future in which thermoelectric generators are not merely made from efficient materials—they are intelligently designed from the inside out.
As industries search for cleaner and more efficient ways to use energy, technologies that turn waste heat into useful electricity could become increasingly valuable. With advanced materials, computer modelling and 3D printing working together, yesterday's wasted heat could become tomorrow's source of power.
Reference: Choo, S., Lee, J., Şişik, B. et al. Geometric design of Cu2Se-based thermoelectric materials for enhancing power generation. Nat Energy 9, 1105–1116 (2024). https://doi.org/10.1038/s41560-024-01589-5
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