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electric backpack Lightning Packs
electric backpack Lightning Packs

Wrap Your Brain Around A Backpack That Creates Electricity

The US Army is testing an “electric backpack” that uses a spring-based frame to harvest kinetic energy from the motion of your hips as you walk.

If you are among those of us who attribute your lingering back problems to the many years you spent schlepping a heavy backpack to school, this one is a little hard to get a handle on but it’s for realz: a backpack that generates electricity while you walk. The “electric backpack” concept has been getting a workout from that master of schleppers, the US Army, and they’ve just come out with an optimistic assessment of the technology.

The brains behind the electric backpack is the aptly named company Lightning Packs, LLC. The company calls its electric backpack the Electricity Generating Backpack but the Army prefers the more prosaic moniker the Rucksack Harvester.

Electric backpack aka rucksack harvester US Army

Electric backpack aka “Rucksack Harvester” worn with solar panel and kinetic knee energy harvesters (photo by David Kamm, courtesy of US Army).

The Electric Backpack Then…

Lightning Packs generated a lot of wattage in terms of media coverage when it first introduced the electric backpack in the journal Science back in 2005. Here’s a representative example from Associated Press in USA Today as enthusiastically reported by Randolph E. Schmid. He cites electric backpack inventor Lawrence E. Rome of the University of Pennsylvania:

Metabolically speaking, we’ve found this to be much cheaper than we anticipated. The energy you exert could be offset by carrying an extra snack, which is nothing compared to weight of extra batteries. Pound for pound, food contains about 100-fold more energy than batteries.

As originally conceived, the backpack could produce a little more than 7 watts basically by jostling up and down on your hips as you walk. The heavier the load, the more power you can produce.

That doesn’t seem like much, but if you really need to power up those night vision goggles on an extended walkabout, it could be a lifesaver.

Here’s a snippet from the 2005 abstract in Science, describing what was then called the “suspended-load backpack:”

…[it] converts mechanical energy from the vertical movement of carried loads (weighing 20 to 38 kilograms) to electricity during normal walking [generating up to 7.4 watts, or a 300-fold increase over previous shoe devices (20 milliwatts)].

Unexpectedly, little extra metabolic energy (as compared to that expended carrying a rigid backpack) is required during electricity generation…

Schmid and his research team posited that the relatively low need for extra metabolic expenditure could be due to a change in gait naturally adopted by the backpack wearer, in response to the ergonomic design of the mechanism. The load is held by springs instead of being tied rigidly to the frame, enabling it to move up and down.

As Schmid recounts, the backpack was developed on request of the Office of Naval Research (think Marine Corps if you can’t figure out why the Navy would need an electric backpack).

Initially, the frame containing the generating mechanism weighed about 10 pounds, so one challenge for Rome and his team was to get the weight down. Another requirement for military use was to reduce the noise made by the frame as it moves up and down.

The Electric Backpack Now…

So, whatever happened to that electric backpack? Rome and his colleagues formed Lightning Packs, which in addition to the electricity-generating model also markets an ergonomic backpack that enables the wearer to carry more weight without a consequent increase in strain.

electric backpack Lightning Packs

“Electric backpack” courtesy of Lightning Packs.

In terms of media coverage, though, it looks like the electric backpack dropped off the map until just last week, when the US Army reported on a test run that included a total of three mobile energy devices.

The exercise took place during the Maneuver Fires Integration Experiment (MFIX) joint training exercise at Fort Benning in Georgia, following a successful test last April at Fort Devens in Massachusetts.

According to Army writer Jeff Sisto, the improved electric backpack mechanism can generate 16 to 22 watts while walking, and up to 40 watts while running.

Aside from the electric backpack, wearable energy harvesting gear for MFIX included the aptly named Knee Harvester, a kinetic device designed to harvest energy from the motion of your knee, courtesy of the company Bionic Power.

kinetic knee energy harvester bionic power

Kinetic knee energy harvester courtesy of Bionic Power

If that name rings a bell, CleanTechnica covered Bionic Power back in 2008, so it’s nice to see the company’s knee-harvesting generator in action. Research on various body motion-to-electricity devices is also under way elsewhere and for all you Walking Dead fans out there, yes you could harvest a lot of electricity from walkers because that’s what they do.

The Knee Harvester is software-controlled to pull excess energy from the descending part of the stride so as not to interfere with the metabolic energy needed for walking.

solar backpack and helmet MC-10

Solar backpack and helmet courtesy of MC-10.

The third device in the trial consisted of flexible gallium arsenide solar panels designed to cover the helmet and backpack, from the company MC-10.

As for why all this emphasis on non-conventional power, think of all the battery-powered electronic gear modern Soldiers pack around, how much those batteries weigh, and what happens when you’re out on patrol with a dead battery. The US military is applying lessons learned in Afghanistan and similar venues to force mobility, as well as to stationary facilities.

Our troops are using non-conventional, renewable energy to adapt to a changing world (climate change, much?), sure would be nice if certain professed troop-supporting members of Congress were in support of those efforts.

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Written By

Tina specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.

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