It all happened in a flash about four years ago. That is when researchers coated a short piece of yarn made of carbon nanotubes with TNT and lit one end with a laser.
It sparkled and burned like a fuse and it showed a new way to possibly generate electricity that produces phenomenal amounts of power.
At the time, no one in Michael Strano’s chemical engineering lab at MIT understood how it worked, and it was so inefficient that it was little more than a “laboratory curiosity.”
Now, Strano understands the underlying physics, which has helped his team improve efficiencies dramatically — by 10,000 times — and charted a path for continued rapid improvements. One day, generators that use this method could make portable electronics last longer, and make electric cars as convenient as conventional ones, both extending their range and allowing fast refueling in minutes.
The efficiencies of the lab devices made so far are still low when you compare them to conventional generators. Strano’s latest device is a little over 0.1 percent efficiency, whereas conventional generators are 25 to 60 percent efficient.
But Strano said the new technology could be useful in some niche applications, where someone or something needs a sudden burst of power. Further improvements in efficiency mean broader applications could soon be feasible.
The new generators exploit a phenomenon Strano calls a thermopower wave. The conventional way to generate electricity by burning a fuel is to use heat to cause expanding gases to drive a turbine or a piston. In Strano’s system, as the fuel burns along the length of his nanotubes, the wave of combustion drives electrons ahead of it, creating an electrical current. It’s a much more direct and efficient way to generate electricity, since you will not need turbines or conventional generators.
Since the nanogenerator runs on liquid fuels, which stores more energy than batteries, there’s hope they could allow electric cars to go much farther than they do now.
It’s a setup not unlike the one in an internal combustion engine, in which bursts of fuel spray into combustion chambers to drive pistons. Power electronic circuits could take the bursts of power from several nanotube generators and smooth it out, using it to drive electric motors in a car. The fuel tank could end up refilled like one in a conventional car. And because the carbon nanotubes remain intact in the process, they can end up used over and over again.
Strano just discovered switching from nanotubes to flat sheets of nanomaterials, such as single-atom-thick graphene, improves efficiency. Shaping the sheets to direct the energy of the thermopower wave also boosts performance.