Forget the toxic material lithium as researchers from the Massachusetts Institute of Technology (MIT) have come up with an alternative system for generating electricity which harnesses heat and uses no metals or toxic materials for powering smartphones or cars, even deep space missions.
The new approach is based on a discovery announced in 2010 by Michael Strano, the Carbon P. Dubbs professor in chemical engineering at the MIT, and his co-workers.
A wire made from tiny cylinders of carbon known as carbon nanotubes can produce an electrical current when it is progressively heated from one end to the other, for example, by coating it with a combustible material and then lighting one end to let it burn like a fuse.
Now, Strano and his team have increased the efficiency of the process more than a thousandfold and have produced devices that can put out power that can be produced by today’s best batteries.
The researchers, however, caution that it could take some years to develop the concept into a commercialisable product.
“It’s actually remarkable that this [phenomenon] hasn’t been studied before. The latest experiments show good agreement between theory and experimental results, providing strong confirmation of the underlying mechanism,” said Strano in a paper published in the journal Energy & Environmental Science.
Already, the device is powerful enough to show that it can power simple electronic devices such as an LED light.
Unlike batteries that can gradually lose power if they are stored for long periods, the new system should have a virtually indefinite shelf life.
That could make it suitable for uses such as a deep-space probe that remains dormant for many years as it travels to a distant planet and then needs a quick burst of power to send back data when it reaches its destination.
Basically, the effect arises as a pulse of heat pushes electrons through the bundle of carbon nanotubes, carrying the electrons with it like a bunch of surfers riding a wave.
The improvements in efficiency, Strano says, "brings [the technology] from a laboratory curiosity to being within striking distance of other portable energy technologies," such as lithium-ion batteries or fuel cells.
In their latest version, the device is more than one percent efficient in converting heat energy to electrical energy, the team reports, which is "orders of magnitude more efficient than what’s been reported before."
In fact, the energy efficiency is about 10,000 times greater than that reported in the original discovery paper.
“It took lithium-ion technology 25 years to get where they are” in terms of efficiency, Strano pointed out, whereas this technology has had only about a fifth of that development time.