Lithium battery technology has seen significant advancement in recent years, but a competing portable power source is already well on its way to commercialization.
Researchers at MIT were able to generate electrical current by heating a wire made from carbon nanotubes from one end to the other. When the tubes were coated with a combustible material, such as TNT, heating one end made them burn like fuses.
Although this discovery revealed a previously unknown phenomenon, the current produced from initial experiments was insignificant. More recent research has increased process efficiency by several orders of magnitude.
Creating A Thermopower Wave
This fuse-like effect arises when a pulse of heat pushes electrons through the bundle of carbon nanotubes, carrying the electrons along like a surfer on a wave. The wave of heat produces either a single voltage or two different voltage regions simultaneously.
According to the research team’s mathematical models, this is because the thermopower wave divides into two different components which sometimes reinforce one another and sometimes counter each other.
Initial experiments used a TNT coating to generate the heat but recent developments have used sucrose. The latest version of this device is more than 1 percent efficient in converting heat energy to electrical energy, which is 10,000 times greater than the original experiments. Other combustible materials could provide even higher efficiencies.
More Applications for Carbon Nanotubes
“It took lithium-ion technology 25 years to get where it is now, in terms of efficiency,” said Michael Strano, a professor in chemical engineering at MIT who led the research.
In contrast, this new technology has had only a fifth of that development time.
Unlike batteries that can gradually lose power if they are stored for long periods, these nanotube fuses have a virtually indefinite shelf life. The thermopower system is also scalable for use in even the smallest electronic devices, which is a characteristic batteries and fuel cells do not possess.
Moreover, the fuel used in the new device is a renewable resource and much safer to use compared to toxic and flammable lithium.
“We can obtain phenomenal bursts of power, which is not possible from batteries. For instance, powering long-distance transmission units in micro- and nano-telecommunication hubs,” said Kourosh Kalantar-Zadeh, professor of electrical and computer engineering at RMIT University in Australia, who was not involved in the research.
The thermopower wave system could also be used in deep-space probe applications, where the probe remains dormant for years while travelling through space and then sends data when it finally reaches its destination.
“I believe that we are still far from the upper limit that the thermopower wave devices can potentially reach,” Kalantar-Zadeh added. “However, this step makes the technology more attractive for real applications.”
The research was published in the journal Energy & Environmental Science.