In 2012, Joseph Heremans and his team at The Ohio State University (OSU) successfully proved that magnetic fields could be used to boost the voltage of a thermoelectric device, so long as that device was a thin film of exotic and expensive nanomaterials. After four years of work, Heremans and his team have now replicated that same effect in a much more affordable nickel-platinum alloy.
According to the second law of thermodynamics, no matter how clever you might be, you’ll never be able to prevent some energy being lost from your device, whether it’s a smartphone or a jet engine. That lost energy typically manifests as waste heat. However, the OSU researchers were able to use a quantum mechanical effect called the Seebeck effect, which generates electricity from the flow of electrons across temperature gradients, to recapture that waste heat. As a result, the voltage output of thin films of nano-structured materials increased from a few microvolts to a few millivolts.
Unfortunately, this required materials that can both conduct electricity and hold a temperature gradient, which thus far has required either nanoscale construction or the use of elements so rare that the last time you heard of them was when you memorized the periodic table for high school.
In their new paper in Nature Communications, Heremans and his team explain how they had to completely rethink the physics of thermoelectricity using modern knowledge of quantum mechanics. Heremans specializes in the study of ‘magnons’, the elementary quasiparticles of magnetic force, and compares their role in his team’s work to that of steam in steam engines, air in car and jet engines or electrons in classical thermoelectrics.
The team’s experiments in 2012 laid a thin film of platinum over magnetic material, then bombarded the platinum’s electrons with magnons, boosting the film’s voltage by a factor of a thousand
Their new experiments use a more practical medium - a piece of nickel sprinkled with a small amount of platinum nanoparticles. When this alloy is heated and magnetic force is applied, it can produce anywhere from tens to hundreds of times its ordinary voltage.
While platinum is still pretty expensive, Heremans believes that with further research, the same principle can be easily replicated using more affordable materials.
For more research from the world of solid-state thermoelectrics, find out how a new paintable thermoelectric material recycles energy from waste heat.