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Clean Power Lithium purple-bronze (LiPB) is a thermoelectric material comprised of aligned conducting, zig-zag chains of molybdenum and oxygen (left image, pink and white circles with green bonds). When an electric current was applied in a direction slightly misaligned with the chains (depicted as gray lines, right image), heat flowed perpendicular to the current, a phenomenon known as the transverse Peltier effect. The efficiency of this effect in LiPB was among the largest known for a single compound.
Image Credit: Dr Joshua Cohn, University of Miami

Published on May 21st, 2014 | by James Ayre

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Thermoelectric Materials For Power Generation — New Insights Boost ‘Green’ Potential

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May 21st, 2014 by
 
The field of thermoelectrics might have just taken a notable step forward, especially with regard to “green energy” applications, thanks to new work from the University of Miami.

Researchers there recently discovered the “surprising” properties of a metal named lithium purple-bronze (LiPB) — properties that make the metal very well-suited to use in thermoelectric applications, such as waste-heat recovery, lower-cost refrigeration, and energy detection.

Lithium purple-bronze (LiPB) is a thermoelectric material comprised of aligned conducting, zig-zag chains of molybdenum and oxygen (left image, pink and white circles with green bonds). When an electric current was applied in a direction slightly misaligned with the chains (depicted as gray lines, right image), heat flowed perpendicular to the current, a phenomenon known as the transverse Peltier effect. The efficiency of this effect in LiPB was among the largest known for a single compound. Image Credit: Dr Joshua Cohn, University of Miami

Lithium purple-bronze (LiPB) is a thermoelectric material comprised of aligned conducting, zig-zag chains of molybdenum and oxygen (left image, pink and white circles with green bonds). When an electric current was applied in a direction slightly misaligned with the chains (depicted as gray lines, right image), heat flowed perpendicular to the current, a phenomenon known as the transverse Peltier effect. The efficiency of this effect in LiPB was among the largest known for a single compound. Image Credit: Dr Joshua Cohn, University of Miami

“If current efficiencies of thermoelectric materials were doubled, thermoelectric coolers might replace the conventional gas refrigerators in your home,” stated Joshua Cohn, professor and chairman of the UM Department of Physics in the College of Arts and Sciences and lead author of the study. “Converting waste heat into electric power, for example, using vehicle exhaust, is a near-term ‘green’ application of such materials.”

The press release from the University of Miami explained the new findings:

Useful thermoelectric materials produce a large voltage for a given temperature difference, with the ratio known as “thermopower.” LiPB is composed of aligned conducting chains. The researchers found that this material has very different thermopowers when the temperature difference is applied parallel or perpendicular to the conducting chains. When an electric current was applied in a direction slightly misaligned with the chains, heat flowed perpendicular to the current, a phenomenon known as the “transverse Peltier effect.” The efficiency of this effect in LiPB was among the largest known for a single compound.

“That such a large directional difference in thermopower exists in a single compound is exceedingly rare and makes applications possible,” explained Cohn. “This is significant because transverse Peltier devices typically employ a sandwich of different compounds that is more complicated and costly to fabricate.”


Part of the reason that LiPB was chosen as the researchers’ subject of investigation was the fact that it had never been studied in detail before — metals with similar electronic structures generally exhibit “interesting” physics and the thermoelectric properties.

“The present material,” he continued, “might be useful as it is, but the larger implication of our work is that the ingredients underlying its special properties may serve as a guide to finding or engineering new and improved materials.”

The new findings are detailed in a new paper published in the journal Physical Review Letters.

On the subject of thermoelectrics — a rather big “breakthrough” was recently made by researchers working at the University of Colorado Boulder. That breakthrough was the creation of an entirely new approach to one of the limitations that have been present in the field of thermoelectrics since it’s birth. Through the use of very small “nanoscale pillars,” it’s possible to radically improve the performance of a thermoelectric material — through a reduction of the heat flow through the material.

As for the new research, they are interesting findings for sure, but hard to say if any of it is economically practical. As it stands, most thermoelectric applications rely on relatively expensive-to-manufacture materials — creating a situation where it’s often cheaper just to go with more established means of energy generation or recovery than it is to utilize said materials.

Still, a very interesting field — one worth keeping a eye on.

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About the Author

's background is predominantly in geopolitics and history, but he has an obsessive interest in pretty much everything. After an early life spent in the Imperial Free City of Dortmund, James followed the river Ruhr to Cofbuokheim, where he attended the University of Astnide. And where he also briefly considered entering the coal mining business. He currently writes for a living, on a broad variety of subjects, ranging from science, to politics, to military history, to renewable energy. You can follow his work on Google+.



  • Steve Grinwis

    Even at double the efficiency of typical Peltier units, it would still be half as efficient as an A/C compressor setup.

    They claim great thermopower for a single substrate… But it would need to be 4 times the thermopower of a multiple substrate to even compete with modern A/C units.

    They *may* replace existing peltier applications one day, but your A/C in your car is going to remain a traditional pump.

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