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US Army's Boot-Based Energy Harvester Lightens Soldier's Load

The SPaRK biomechanical energy harvester produces 6 to 9 watts of continuous electricity from walking.  (Credit: SpringActive Inc.)
The SPaRK biomechanical energy harvester produces 6 to 9 watts of continuous electricity from walking.
(Credit: SpringActive Inc.)

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re: boot-based energy harvester
davidwheath   11/22/2011 9:51:41 AM
A few issues with this one. Article states a charge rate of 6-9watts/85minutes walking 3mph - enough to charge 2 AA cells. That sounds good enough, but in reality will take much longer because the average soldier will not be walking 85 minutes straight. He may be on his feet for hours, but not necessarily moving. Those charge times are best scenerio and I think misleading. Also, as someone who has been in Iraq pounding the pavement, I don't like the bulk and snag hazard of the unit. Open street walking is one thing, but climbing over obstacles, in and out of vehicles is another. I hope it works well in the field, but I would rather have a few spare AAs in my pocket rather than rely on this to "eventually" charge my cells.

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18 AA Duracell weighs the same as this device
ScotCan   11/22/2011 9:53:16 AM
This concept doesn't appear to make much sense. The target weight is stated as 430 grams and a Duracell AA weighs in at 23 grams, so essentially the soldier could carry at least 18 Duracell AA's instead of the complex arrangement described.Canadian built Duracell AA's were 1.5Wh units produced for the RCMP, so, high performance alkaline are available with their consistency and reliability. Moreover they can be carried bandolier style which foot soldiers will tolerate more so than some device clinging to their ankles.

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boot based energy harvester (EH)
azny   11/22/2011 10:15:21 AM
a couple of comments: (1) this is not for the HumVee based soldiers, this is intended for Special Op's or Covert Actions where the only transport is by foot (2) you still have to carry a number of different size batteries to fit into the EH to capture the generated energy ( i.e. a couple of AA, C, D, 9V, etc) so you haven't gained all that much (3) the key to the success of this device is not how well it works but rather its ready acceptance and adoptability by those that use it-- the soldiers; just looking at the photo of the device its clear that those soldiers that were consulted in the design phase (and i'm being generous here) clearly never served in the field--I'd give the most tolerant and forward thinking soldier, who is wearing a 70LB pack and carrying a 50 caliber machine gun about 100yds before he tore this off and threw it away--and they are already finishing a Phase II for $750K and looking for investment for Phase III??

Don't get me wrong-- the concept is worthwhile, DARPA and DoD have been pursuing this for years, but this incarnation has got a real ways to go. Sorry :(

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Re: For Military Dismounted Solders, minimizing SWAP is KING. – Size, Weight And Power
oldpete   11/22/2011 10:25:40 AM
Why such a Rub-Goldberg contraption? Put a closed loop air cushion ( piston ) in the heal of the boot to both soften the walking shock load and apply the downward walking pressure (kinetic energy) to drive the generator through hydraulic principles. All contained inside the heal of the boat for a sealed unit...

Criteria Dependent
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Re: For Military Dismounted Solders, minimizing SWAP is KING. – Size, Weight And Power
Criteria Dependent   11/22/2011 10:42:37 AM
Agreed, As a former infantryman, I can see this unit seriously hampering forward progress. Especially walking in mountainous and rocky terrain. I agree with the previous post, a sealed unit in the sole of the boot might be a better approach.

Alexander Wolfe
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Re: boot based energy harvester (EH)
Alexander Wolfe   11/22/2011 11:39:58 AM
Azny and Criteria Dependent, I'd like to thank you both for your experienced-based perspective. Re Azny's comment about the variety of batteries and HumVees, that's exactly what I was trying to get at in my earlier comment, though I missed the mark. What is the solution for HumVees? What do HumVee-based troops do when, say, their IR vision equipment runs down?

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Boot-based energy harvester
MYRONB   11/22/2011 11:46:07 AM
In all of these energy harvesting schemes, consideration must be given to:  The cost /benefit of a device including weight, ease of use, reliability and other factors versus the actual energy recouped.  For the few watts recouped, the user (the dog-face hauling it around) has a bulky gizmo that may affect agility when climbing terrain and urban rubble, and increase the effort to walk. Remember, that harvested energy has to come from somewhere.

This deal reminds me of a project I consulted on: the client wanted to attach wind turbines to an electric automobile to recoup energy to help charge the car's batteries.  A simple paper analysis showing the fallacy of his idea wouldn't do, so he bought an electric vehicle and paid me to prototype and test wind turbine generators that, as predicted, didn't cut the mustard.

Myron Boyajian, PE

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Poor Choice of Location
bja55   11/22/2011 12:14:40 PM
Get the device off the foot and put it in a kneepad that most of the soldiers wear anyway.  Make it a hybrid knee "orthotic" & workmans kneepad that can be worn externally on the leg.  It'll be much easier to access in situations where you can't reach all the way down to your ankle to locate a new battery.

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Re: Useful solution
Tool_maker   11/22/2011 12:50:33 PM
@George Kaye. You are so right. Does this not sound so typically bureaucratically government? If the problem is batteries then find a way to get the troops batteries. Not some fancy doodad that is going to add wieght and effort to his job.

The article says 20 pounds of batteries, "about 1/5" of his equipment weight. That means each soldier is carrying 100 pounds. It was another war and a whole different army, but when went on an operation with rations for 3 days, our own ammo, 200 rounds for our M-60, claymore mine, flares/smoke, and a LAW my rucksack wieghed in at 70 pounds and kicked my tail. By the end of the day very few of us were in a combat ready state. I question the extra 30 pounds in this article. If there is indeed 30 more pounds today, then that should be the first order of business: get some of that weight out of there.

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100# pack is bottom-line
Mexjewel   11/22/2011 12:53:00 PM
Take heavy packs off backs. Then put wheels on them. Each axle could drive a small generator while making combat postures possible. Drop the pack handle and grab the rifle. Much simpler than untangling from two pack-straps to fight. Save energy by pulling the pack while charging cells.

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