A New Kind of Military Charge
Bionic Power’s PowerWalk knee brace provides wearable electric generator for gadget-laden soldiers.
A B.C.-based company has developed a device that harnesses the marching power of soldiers to operate night vision goggles, radios, navigation gear and other battlefield equipment. The lightweight, mechanical PowerWalk brace recharges equipment batteries carried by soldiers as they walk and is designed to overcome problems using other “energy harvesting” devices now in use, such as hand-operated cranks.
“It’s very difficult for anybody to crank long enough to produce an appreciable amount of power,” says Bionic Power CEO Yad Garcha. “Our device is on the knee and as long as you’re walking, you can be producing power.”
Garcha says the “elegance” of the PowerWalk system stems from its use of the negative energy that occurs in the hamstring as the human leg decelerates or brakes. Instead of dissipating into heat, that negative energy is turned into electric power—as much as 12 watts of electricity on average, or enough to power four cell phones. He adds that military users are increasingly turning to ways of recharging a single large battery rather than forcing soldiers “to carry umpteen kinds of different batteries that are not rechargeable.”
With a targeted design weight of 800 grams, PowerWalk will also be lighter than the five to seven kilograms of Double A batteries that Canadian soldiers currently carry during a mission. To accomplish this, Bionic Power is re-engineering the brace’s gear box to reduce its width, which will also make it smaller and less cumbersome.
“For the solider, we figure we can reduce the envelope and width by half going forward,” says Garcha. “The device is especially beneficial in reducing the fatigue and injury that can occur when soldiers walk downhill. We make a material difference to the soldier’s fatigue by reducing the metabolic effort. It takes them less effort to go downhill using our device than it would if they were not using it.”
Critical to a soldier’s mission on the battlefield is silence, something PowerWalk facilitates through a combination of plastic and metal gears to make the device quieter. “Eventually, we’ll also introduce a mechanical clutch so that we can completely disengage if the soldier needs to go into quiet mode.” Much of the device’s usefulness also depends on where a soldier is fighting. In Afghanistan, 24- and 72-hour missions where Canadian soldiers walked a great deal were quite normal. In Iraq, energy harvesting devices would have been less useful because U.S. soldiers fought in urban settings and mostly traveled in personnel carriers.
Soldiers themselves have been helpful in identifying and solving real time challenges associated with the PowerWalk system. Garcha and his colleagues had not been told, for example, that soldiers often have to drop into full squat positions. This turned out to be difficult to do while wearing the brace.
“When you do a full squat, you’ll notice your thighs expand by an inch to an inch and a half,” Garcha explains. “We had rigid braces, so it didn’t work and we had to go back to square one. It took us another year to sort that out. ”
Another challenge is how to distribute the power across the soldier’s body using PowerWalk’s centralized battery system. Admits Garcha, “That is not something that has been sorted out to everyone’s satisfaction.” Wireless distribution “is just not on,” he adds, but wiring to distribute both data and power could be located inside the soldier’s uniform. Another possibility is combining Powerwalk with a backpack developed in the U.S. equipped with lightweight solar panels and sewn into a soldier’s uniform. That device moves up and down as a soldier walks and is capable of producing up to 10 watts of power.
Fewer batteries using the PowerWalk system will mean a considerable cost savings to the U.S. and Canadian armies. Another savings is to the environment. Rechargeable batteries eliminate the need to bury batteries when they run out of power. But the key remains how soldiers in the field respond to the device, notably how the brace feels and looks. “We need to make it attractive and the soldiers needs to understand we will not hinder any movement,” says Garcha. “We can’t slow them down.”
These and other issues are much closer to being resolved now that Bionic Power has secured contracts with the U.S. Army through its Natick Soldier Research, Development and Engineering Center and funding from Defence Research and Development Canada (DRDC), the Canadian Forces’ science agency. But Garcha says it’s been a slog. Small military design companies struggle to attract investment dollars and survive in Canada, especially on the west coast.
“But the end users have come around to realize they need to have this developed, so they’re supporting us.”
David Godkin is a Victoria, B.C.-based freelance writer.