- Imagine using a computer that runs on energy generated
from your building's wall and window vibrations. Masayuki Miyazaki, a senior
researcher at Hitachi Co. Ltd.'s central lab in Tokyo, is trying to do
just that.
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- He recently made a tiny generator that converts building
movements into electricity, creating enough energy to run a temperature
or light sensor once an hour. Though the output is small right now, only
about 10 microwatts, scientists predict the generator's potential could
be huge in coming decades - possibly used in battery-free computing systems.
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- Dr. Miyazaki's work is part of a growing movement by
scientists to find, create, or capture alternative sources of energy -
even in small amounts much less than one watt. Researchers hope to harvest
power from anything from the vibrations of walls and windows to the movements
of air and the human body.
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- While alternative energy sources alone might not produce
much electricity, they could help power small devices such as computer
chips, wireless sensor networks, or cellphones. The idea is simple. Just
as some wristwatches power themselves from the random movements of a person's
arm, these devices would capture energy from random movements of other
things.
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- In another approach, Larry Kostiuk at the University
of Alberta in Canada, is working on a water-powered battery. Its special
trait: creating electricity directly from water on the tiniest scales.
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- Most people are familiar with hydroelectricity, which
uses water falling from a height to drive turbines and generate electricity.
Professor Kostiuk's method differs in that water is put under pressure
as it moves through microscopic channels within a glass or ceramic-filter
tube, allowing electricity to be converted directly from water. The experimental
tube, about 2 centimeters in diameter, has about half a million tiny channels
or holes through which the water is inserted by a hand-operated syringe.
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- As water travels over the surface of the channels, it
becomes electrically charged when its ions rub up against the solid surface.
Scientists placed electrodes at the ends of each channel and then extracted
electrical energy as current flows between the electrodes. Right now currents
are very low, around 4 microwatts, but millions of channels could be added
together to increase the power output enough to create a water-powered
battery.
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- Drawing on energy around us
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- Miyazaki's approach generates electricity from the ambient
energy all around us. A building's walls and windows vibrate constantly
because of wind, air conditioners, or passing trucks. Since the power is
still very small, Miyazaki says he aims to use the power source as an "on-chip
battery" for circuits such as those used in computers and other electronic
products.
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- "The application is a field called 'ubiquitous computing.'
For example, wireless sensor networks of small chips can be distributed
everywhere," he says.
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- Miyazaki says commercial applications will emerge in
several years, although the approach requires more research to make it
economically feasible.
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- Eventually, he plans to put a sensor, wireless transceiver,
processor, and power source into one small package that can be used in
wireless sensor networks. Such networks are expected to become part of
our everyday environment and will be placed in buildings, on roads, and
on bridges.
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- Miyazaki isn't the only one tapping vibrations to create
electricity. Shad Roundy, professor of engineering at the Australian National
University in Canberra, is pursuing techniques to capture energy from low-level
vibrations caused by factors such as building movement. One of his methods
is similar to Hitachi's, but he now is leaning toward using a piezoelectric
approach, electricity caused by mechanical pressure or strain, which he
says can work better.
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- A two-layer diving board
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- Professor Roundy's piezoelectric generator is similar
to a two-layer diving board with a boulder on the end of it. When the device
is shaken, the beam resembling the double diving board bends, creating
tension in the top layer and compression in the bottom. The opposite happens
if the beam is bent the other way, so power can be drawn in either direction.
Roundy says he designed several devices that can be placed on vibrating
structures to generate power. The best output so far is about 300 microwatts
per cubic centimeter.
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- Power from the factory floor
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- This method is "attractive in providing power for
very low-power wireless sensors and transmitters, but are not useful for
large-scale electrical power generation," he says. Roundy says commercial
applications could emerge within a year and may include harnessing energy
from a manufacturing floor.
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- Kostiuk remains cautiously optimistic about the future
for such new approaches. "I don't know if it will ever work at an
efficiency that makes it relevant for widespread use," he says of
his water battery. "But it can take multiple decades for something
to see commercial applications."
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- © 2003 The Christian Science Monitor. All rights
reserved.
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- http://www.csmonitor.com/2003/1113/p14s02-stct.html?sciTechNav
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