Invisibly small carbon nanotubes aligned as fibers and sewn into fabrics become a thermoelectric generator that can turn heat from the sun or other sources into energy.
The Rice University lab of physicist Junichiro Kono led an effort with scientists at Tokyo Metropolitan University and the Rice-based Carbon Hub to make custom nanotube fibers and test their potential for large-scale applications.
Their small-scale experiments led to a fiber-enhanced, flexible cotton fabric that turned heat into enough energy to power an LED. With further development, they say such materials could become building blocks for fiber and textile electronics and energy harvesting.
The same nanotube fibers could also be used as heat sinks to actively cool sensitive electronics with high efficiency.
A paper about the project appears in Nature Communications.
The effect seems simple: If one side of a thermoelectric material is hotter than the other, it produces energy. The heat can come from the sun or other devices like the hotplates used in the fabric experiment. Conversely, adding energy can prompt the material to cool the hotter side.
Until now, no macroscopic assemblies of nanomaterials have displayed the necessary “giant power factor,” about 14 milliwatts per meter kelvin squared, that the Rice researchers measured in carbon nanotube fibers.
"The power factor tells you how much power density you can get out of a material upon certain temperature difference and temperature gradient,” said Rice graduate student Natsumi Komatsu, lead author of the paper. She noted a material’s power factor is a combined effect from its electrical conductivity and what’s known as the Seebeck coefficient, a measure of its ability to translate thermal differences into electricity.
“The ultrahigh electrical conductivity of this fiber was one of the key attributes,” Komatsu said.
Author: MIKE WILLIAMS