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Climate change and energy

Harnessing Kinetic Energy

A microgenerator could power portable devices for troops.
November 29, 2007

Soldiers who are packing multiple portable technologies could soon have less heavy lifting to do. M2E Power, a biomechanics startup based in Boise, ID, has developed a microgenerator that is designed to replace the 10 to 30 pounds (4.5 to 13.6 kilograms) of batteries that the company says troops carry to power devices such as radios, night-vision goggles, and mine detectors.

Power to go: Walking and other movements jostle the magnets, infusing the wire coils with energy in M2E’s microgenerator.

The battery-size product, the M2E, harnesses kinetic energy, or normal physical movement, to generate power. Clipped onto a belt or carried in a knapsack, the entire generator is contained within a regular battery casing. The wearer’s walking or shaking moves magnets in the device. Those magnets infuse the wire coils with energy that can be used to power mobile devices. It isn’t a new technology: the device uses the same technical principle that operates a self-winding watch or a “shake and shine” battery-free flashlight. But those watches and flashlights aren’t highly efficient at generating power. A battery-free flashlight, for example, harnesses enough kinetic energy to power an LED bulb for 45 minutes after 30 seconds of shaking, but not all kinds of shaking will work.

“A shaker flashlight charges only if you move it in one direction, so motions in other directions do nothing,” says Donald Moorcroft, professor emeritus of physics at the University of Western Ontario, in Canada.

According to M2E Power’s website, its system is five to seven times more powerful than existing applications of the technology. So soldiers using the M2E microgenerator should have an easily renewable source of power.

“With the flashlight and other applications of this technology, the magnet has to pass all the way through the coil before it can generate electricity,” says Regan Rowe, director of business development for M2E Power. “Our core innovation is that the magnet starts to generate electricity after it passes the width of just one wire.”

Development of the microgenerator comes at a time when the military’s reliance on portable devices is intense, and conventional batteries are problematic in the field. Soldiers are advised not to go out on missions with a half-charged battery, for example. As a consequence, batteries are often discarded before they are fully used. To address the military’s mobile-power issues, the Department of Defense recently launched a wearable-power prize worth $1 million.

It’s a cause that the private sector is keen to support. M2E Power recently received $8 million in venture-capital funding to develop the microgenerator for the military market. Rowe says that the company expects to have M2Es to soldiers in as little as 12 to 14 months. A consumer charger, for mobile devices ranging from cell phones to portable gaming stations, is expected to reach the market in 18 to 24 months.

M2E Power is not the only company working on a device of this kind or using this technology. Steve Vetorino, inventor of the NightStar battery-free flashlight, is working on a very similar device. “One thing that I find suspicious is that the developer of this technology never mentions how long it will take to recharge a standard battery,” he says. “We’re currently working on a proprietary charging technology that will be able to recharge a C-size battery in only 10 minutes. Our device fits in the palm of your hand and weighs only a few ounces.”

Whatever the device, storing movement itself may be a problem. While it is easy to see how soldiers who cover several miles on foot patrol would constantly keep these kinetic battery replacements powered, what levels of power output will more sedentary civilian consumers see? According to Rowe, even the movements of inactive people should “trickle-charge” the microgenerator throughout the day.

“If you’re a low-activity human, as most Americans are, you spend about two hours a day moving around,” Rowe says. “That is enough to charge up one half- to one hour of talk time on your cellular phone. Right now, users average 24 minutes of talk time per day.”

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