Thermoelectric Materials Advance Could Drop the Cost of Waste-Heat Harvesting

by Zachary Rybarczyk

New research could lead to more cost-effective materials for using waste heat for electricity and cooling — opening up innovation in a new class of waste heat conversion technologies.

High-efficiency thermoelectric materials — technologies that allow excess heat to be converted to electricity, and electricity to be converted into refrigeration — have been improved by researchers in New York, who say they have developed a process to increase conversion efficiencies and reduce material costs.

Thermoelectrics are used in portable, lightweight refrigerators and coolers, as well as in automotive exhausts, where excess heat converted by thermoelectric converters has been found to increase fuel economy by three percent.

These conversions occur because of a difference in electric potential between the protons and electrons of the materials. When connected to a circuit and insulated properly, these technologies can contribute to enormous efficiencies in energy use.

Materials scientists and engineers at Rensselaer Polytechnic Institute have developed new processes that allow manufacturers to break down and microwave bismuth telluride, a popular thermoelectric material, into “hexagonal nanoplates” — tiny thermoelectric particles that, when pressed together, form extra-efficient heat (and energy) transferring materials.

Past advances in the field have been stymied by the lack of ability to produce both electron (“n-type”), and proton-heavy (“p-type”), nanoparticles, both necessary for electricity conversion, and a problem that RPI researchers have overcome:

The technique, presented in a Nature Materials paper posted online last week, makes p-type materials that are as efficient as the best ones on the market, while the n-type materials are at least 25 percent more efficient. One of the biggest commercial thermoelectric device manufacturers is now interested in adopting the new materials and process.

The key breakthrough of the RPI work, according to Badding, is that the researchers are building the nanostructured materials from the bottom up using chemistry. This means they can fine-tune the properties of the building blocks and their assembly to improve the material’s properties. “The way they’re making the material is a big deal,” he says. “The hope is that in the future, this type of approach could lead to better [efficiency].”

The Institute’s advancements in production and process are already being picked up by thermoelectric device manufacturers in the market. These new materials could be used to help cool electronics, large buildings and power vehicles.