NREL Captures Waste Heat with Carbon Nanotubes

Researchers at the Energy Department's National Renewable Energy Laboratory (NREL) have demonstrated that carbon nanotubes have the potential to act as a thermoelectric power generator that captures and uses waste heat. NREL believes the research could help guide manufacturing of thermoelectric devices based on either single-walled carbon nanotube (SWCNT) films or carbon nanotube composites. "There have not been many examples where people have really looked at the intrinsic thermoelectric properties of carbon nanotubes and that's what we feel this paper does," said Andrew Ferguson, a research scientist in NREL's Chemical and Materials Science Center and co-lead author of the paper with Jeffrey Blackburn. As NREL explains, carbon nanotubes perform better than inorganic materials, which have caused problems for nanomaterial researchers in the past due to their high weight and low flexibility.  They add that metallic nanotubes actually can do harm to thermoelectric generator, whereas carbon nanotubes actually enhance its performance. With thermoelectric materials, there is a trade-off between thermopower (the voltage obtained when subjecting a material to heat) and electrical conductivity because thermopower decreases with increased conductivity. The researchers discovered, however, that with carbon nanotubes you can maintain large amount of thermopower even at very high electric levels. According to a report from Clean Technica, Blackburn did not want to “put an exact time frame on when devices will be in the market,” but did say they are “working on a number of strategies to further improve the thermoelectric figure of merit by increasing the power factor and decreasing the thermal conductivity.” For more information, read the full study "Tailored Semiconducting Carbon Nanotube Networks with Enhanced Thermoelectric Properties."