Thermoelectric materials have been a tantalizingly promising technology for producing electricity from heat that would otherwise just be wasted. The basic premise of thermoelectric materials is that an electrical current is generated as a result of a difference in temperature between one side of the material and the other.
This would seem to be an obvious way to generate an electrical current from your computer or your car just based on the heat they produce. But heretofore, the available materials had poor thermoelectric conversion efficiency or were prohibitively expensive for commercial uses—they just didn’t produce that much current for the buck.
But when traditional materials fail, in come the nanomaterials. We’ve covered multi-walled carbon nanotubes for this use, along with nanowires and nanopillars.
Now, researchers at the University of Manchester in the U.K.,in collaboration with the company European Thermodynamics Ltd., have called upon graphene to make thermoelectric materials more useful.
In research published in the journal Applied Materials and Interfaces, the joint academic-industrial team added a small amount of graphene to strontium titanium dioxide (STO), a thermoelectric material that, by itself, generates a current only at extremely high temperatures. The graphene made a big difference: STO’s operating temperature was expanded to room temperature.
“Current oxide thermoelectric materials are limited by their operating temperatures which can be around 700 degrees Celsius,” said Robert Freer, one of the lead University of Manchester researchers, in a press release. “This has been a problem which has hampered efforts to improve efficiency by utilizing heat energy waste for some time.
Another handicap limiting the usefulness of thermoelectric materials is that their energy conversion efficiencies hover around 1 percent. But the Manchester team reports that their new hybrid material will convert 3 to 5 percent of heat into electricity. They reason that because a vehicle loses 70 percent of the energy in fuel via waste heat and friction, applying this material for improved thermal energy recovery will lead to a substantial boost in energy efficiency.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.