Computers and Technology
Harvesting Energy From Motion: New Fiber Technology Unlocks The Power Of Piezos
Imagine a cell phone that recharges its battery as it rides on your hip. Or a wireless sensor that gets its electrical power from the motions the device is sensing.
How about vibration damping technologies powered by the very movements they?re suppressing?
Such developments may be the tip of an iceberg. Advanced Cerametrics of Lambertville, N.J., has developed a new technology that generates 10 time the power of previous energy-harvesting materials while eliminating their application- limiting factors.
The technology is a radical new variation on an old and respected means of harvesting energy: piezoelectricity.
From electricity to motion, and vice versa
In 1880, Pierre and Jacques Curie discovered that certain crystals generate a charge when pressed. They deemed them piezo crystals, from the Greek for ?press.?
Piezoelectric crystals are transducers. They turn mechanical energy into electricity. Conversely, they respond to electrical charges by expanding or contracting.
But traditional piezoelectric compounds are bulky, brittle and inefficient. They convert no more than 40 percent of mechanical energy to electricity. When subjected to an electrical field or current, they expand or contract, but only by tiny amounts.
Advanced Cerametrics piezoelectric fibers, on the other hand, are flexible. They weigh as little as two grams for a transducer that can generate 40 volts. They pick up a wider range of vibration frequencies, and generate 75 percent more power from those vibrations.
Advanced Cerametrics piezoelectric fibers in an electric guitar pickup, for example, capture more sound from vibrating strings and relay that sound without pre- amplification!
And Advanced Cerametrics piezoelectric fibers outperform bulk piezos as electricity-to-motion transducers. They exert a stronger mechanical force over a larger range of motion at just 35 percent the weight. A two-gram active fiber composite strip can produce a blocking authority of 60 pounds!
Far-ranging applications
Advanced Cerametrics manufactures is piezoelectric fibers of lead zirconate titanate, or PZT. Applications for PZT fibers fall into the two broad categories, energy harvesting or actuation. Specifically, a few opportunities stand out.
Wireless sensing
Wireless sensing sounds like a great idea until someone asks, ?Who?s going to
change the batteries?? But if batteries don?t have to be replaced because they?re
recharged in place ? or they?re even eliminated ? the game turns on its head, and
the promise of wireless sensing can be fulfilled.
Most sensors are in environments were ambient waste mechanical energy is abundant, whether it?s inside an air duct or mounted on a motorized system. Advanced Cerametrics PZT fibers harvest that mechanical energy to recharge the batteries or power the sensors directly, without batteries.
Applications for auto-powered monitoring range from aerospace to automotive to home appliances to biomedicine.
Lighting
The higher output power of Advanced Cerametrics piezoelectric fibers opens many
opportunities to power electroluminescent lighting on bridge decks, signage and
buoys, among other applications.
Vibration damping
Advanced Cerametrics PZT composites turn motion into power and power into
motion. Vibration damping uses both characteristics. When vibrations generate
power, built-in circuitry relays the charge to a microprocessor, which measures the
magnitude of the vibration and returns an amplified signal that either stiffens or
relaxes the fiber actuators. They qualify as ?smart systems? for their self-adjusting
nature.
In one of the best-known applications of vibration damping is by Head Sport AG of Kennelbach, Austria. Head uses Advanced Cerametrics PZT fiber composites to reduce tennis racket vibration and ski chatter.
General actuation
Advanced Cerametrics PZT fiber composites have a range of motion that opens
entirely new vistas for energy-to-motion actuation. For example, piezoelectric
fibers have been used to bend small aircraft wing flaps as much as 22 degrees
without hydraulics.
Conventional bulk piezos move such tiny amounts that, when used as actuators, they typically require intermediating mechanisms that amplify movement. The greater range of motion of fiber piezos may allow engineers to skip these intermediating devices.
Performance metrics
The metrics are impressive, and the technology is advancing fast.
Multilayer laminate composites with PZT fiber:
? Voltage output up to 400 Vpp
? PZT fiber diameter 10 ?m to 250 ?m
? Frequency is 10 kHz to 20 MHz
? No lateral wave interference
? Remarkable part-to-part repeatability
? 10x the charge output of other piezo forms
? User-defined shapes open more possibilities for applications
? No significant degradation of composite properties in tests of up to 200 million
cycles
Summary and next steps
In our energy-hungry, battery-powered world, 19th-century piezoelectric materials have had little to contribute. But flexible piezoelectric fibers from Advanced Cerametrics offer 10 times the power output of older forms. They can be shaped in ways the user defines. They?re lighter, more sensitive and have greater actuation potential.
With these new fibers in the picture, we?re sure to see a rush of technologies that capitalize on their properties.
Where do interested engineers go from here?
? Visit advancedcerametrics.com and click ?ACI in the News? for articles and
technical specifications.
? Call Advanced Cerametrics at (609) 397-2900.
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Advanced Cerametrics of Lambertville, New Jersey, USA, won inclusion in R & D Magazine?s R&D 100 in 2003. Fortune Small Business magazine named Advanced Cerametrics one of its 14 Hot Startups for 2003. The company has won 24 Small Business Innovation Research grants, six Small Business Technology Transfer Research grants and DARPA?s Outstanding Contractor award (twice).
Since the mid-80s the company has been issued 16 patents on ceramic materials and processes. Several patents are pending.
The author, Patrick Gillam, writes for a variety of technical clients. To see copywriting by Patrick Gillam, visit itellyousell.com. |
Patrick Gillam
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