(NanoRealm) - Could you imagine a laptop battery that lasted for 500 hours? How about an electric car that boasts a range many times that of a gasoline vehicle? For that matter, think about environmental sensors that could be scattered into the air like dust and collect data. While the last thing might not exactly be what you want for Christmas, a breakthrough in energy production made by MIT researchers could make such technology a reality during the next few years.

The process, dubbed “thermopower waves” by its discoverer, MIT’s Dr. Michael Strano, does nothing less than open up “a new area of energy research, which is rare,” says the scientist. MSNBC’s Michelle Bryner describes the phenomenon and its applications in brief, writing:

Researchers have found a way to produce large amounts of electricity from tiny cylinders made from carbon atoms.

The achievement could replace decades-old methods of generating electricity, such as combustion engines and turbines, the researchers say.

The cylinders are known as “carbon nanotubes,” which are, writes The Energy Collective, “submicroscopic hollow tubes made of a ‘chicken-wire-like’ lattice of carbon atoms.”

To describe the process in more detail, the MIT researchers took the nanotubes, applied a layer of fuel, and then ignited them at one end, creating a “fast-moving thermal [heat] wave traveling along the length of the carbon nanotube like a flame speeding along the length of a lit fuse,” explains the Environment News Service (ENS). This process is facilitated by the fact that nanotubes conduct heat far better than metals — up to 100 times faster. Then, getting more technical still, ENS writes, “As the heat feeds back to the fuel coating, a thermal wave is created that is guided along the nanotube. With a temperature of 3,000 kelvins [sic] (2,726 degrees Celsius or 4,940 degrees Fahrenheit) this ring of heat speads [sic] along the tube 10,000 times faster than the normal spread of this chemical reaction.”

This is where Dr. Strano and his team experienced their Ivory Soap moment. While Strano claims to be the first scientist to predict that thermal waves coursing through a nanotube could create electric current, the great amount of it yielded was not predicted by thermoelectric calculations. “Lo and behold,” said the scientist, “we were really surprised by the size of the resulting voltage peak.” Strano and his team have called this unexpected phenomenon “electron entrainment,” “since part of the current appears to scale with wave velocity,” said Strano.

Because this energy source is so new, it’s hard to predict what the practical applications will be. However, the thermopower-wave process produces 100 times the energy per unit of weight of the average lithium-ion battery. Additionally, Strano says that such a power source would be composed of non-toxic substances, eliminating the disposal problems posed by current-generation energy cells.

The technology could also be used to help create sensors the size of a grain of rice that could be injected into the body and used to monitor health (e.g., heart function), administer medical treatment or, well, use your imagination. There are some ominous implications as well.

One obvious use of the technology, however, would be to create practical electric fuel cells for automobiles. One common drawback of electric cars is that they typically have a very limited range relative to combustion engine vehicles, owing to the fact that gasoline contains far more energy per unit of weight than today’s electric fuel cells. But thermopower-wave generation could change that, providing light, long-range batteries and relatively inexpensive electricity. This could finally allow us to break our dependence on foreign oil.

Whatever the particulars, Dr. Strano’s discovery is just the latest frontier in the staggering field of nanotechnology. The science of manipulating matter on the molecular and even atomic levels, it is quickly making science fiction, science fact.

For more on the subject, see Selwyn Duke's “The New Nanotech World” in the March 31, 2008 issue of The New American.

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Provided by MIT
Source: http://www.thenewamerican.com/index.php/tech-mainmenu-30/energy/3133-nanotech-energy-source-discovered

(NanoRealm) - A team of scientists at MIT have discovered a previously unknown phenomenon that can cause powerful waves of energy to shoot through minuscule wires known as carbon nanotubes. The discovery could lead to a new way of producing electricity, the researchers say.

The phenomenon, described as thermopower waves, “opens up a new area of energy research, which is rare,” says Michael Strano, MIT’s Charles and Hilda Roddey Associate Professor of Chemical Engineering, who was the senior author of a paper describing the new findings that appeared in Nature Materials on March 7. The lead author was Wonjoon Choi, a doctoral student in mechanical engineering.

Like a collection of flotsam propelled along the surface by waves traveling across the ocean, it turns out that a thermal wave — a moving pulse of heat — traveling along a microscopic wire can drive electrons along, creating an electrical current.

The key ingredient in the recipe is carbon nanotubes — submicroscopic hollow tubes made of a chicken-wire-like lattice of carbon atoms. These tubes, just a few billionths of a meter (nanometers) in diameter, are part of a family of novel carbon molecules, including buckyballs and graphene sheets, that have been the subject of intensive worldwide research over the last two decades.

A previously unknown phenomenon

In the new experiments, each of these electrically and thermally conductive nanotubes was coated with a layer of a reactive fuel that can produce heat by decomposing. This fuel was then ignited at one end of the nanotube using either a laser beam or a high-voltage spark, and the result was a fast-moving thermal wave traveling along the length of the carbon nanotube like a flame speeding along the length of a lit fuse. Heat from the fuel goes into the nanotube, where it travels thousands of times faster than in the fuel itself. As the heat feeds back to the fuel coating, a thermal wave is created that is guided along the nanotube. With a temperature of 3,000 kelvins, this ring of heat speeds along the tube 10,000 times faster than the normal spread of this chemical reaction. The heating produced by that combustion, it turns out, also pushes electrons along the tube, creating a substantial electrical current.

Combustion waves — like this pulse of heat hurtling along a wire — “have been studied mathematically for more than 100 years,” Strano says, but he was the first to predict that such waves could be guided by a nanotube or nanowire and that this wave of heat could push an electrical current along that wire.

In the group’s initial experiments, Strano says, when they wired up the carbon nanotubes with their fuel coating in order to study the reaction, “lo and behold, we were really surprised by the size of the resulting voltage peak” that propagated along the wire.

After further development, the system now puts out energy, in proportion to its weight, about 100 times greater than an equivalent weight of lithium-ion battery.

The amount of power released, he says, is much greater than that predicted by thermoelectric calculations. While many semiconductor materials can produce an electric potential when heated, through something called the Seebeck effect, that effect is very weak in carbon. “There’s something else happening here,” he says. “We call it electron entrainment, since part of the current appears to scale with wave velocity.”
The thermal wave, he explains, appears to be entraining the electrical charge carriers (either electrons or electron holes) just as an ocean wave can pick up and carry a collection of debris along the surface. This important property is responsible for the high power produced by the system, Strano says.

Exploring possible applications

Because this is such a new discovery, he says, it’s hard to predict exactly what the practical applications will be. But he suggests that one possible application would be in enabling new kinds of ultra-small electronic devices — for example, devices the size of grains of rice, perhaps with sensors or treatment devices that could be injected into the body. Or it could lead to “environmental sensors that could be scattered like dust in the air,” he says.

In theory, he says, such devices could maintain their power indefinitely until used, unlike batteries whose charges leak away gradually as they sit unused. And while the individual nanowires are tiny, Strano suggests that they could be made in large arrays to supply significant amounts of power for larger devices.

The researchers also plan to pursue another aspect of their theory: that by using different kinds of reactive materials for the coating, the wave front could oscillate, thus producing an alternating current. That would open up a variety of possibilities, Strano says, because alternating current is the basis for radio waves such as cell phone transmissions, but present energy-storage systems all produce direct current. “Our theory predicted these oscillations before we began to observe them in our data,” he says.

Also, the present versions of the system have low efficiency, because a great deal of power is being given off as heat and light. The team plans to work on improving that.

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Provided by Massachusetts Institute of Technology (http://web.mit.edu/)
Source: http://www.physorg.com/news187186888.html