Power-Hungry Devices Challenge Army Researchers

By Stew Magnuson
A soldier tests radio communication during an air assault operation.

Photo: Army

Dismounted troops know that they will always have an adequate supply of food and water in any operation. The Army spends billions of dollars to ensure that’s the case.

“The assumption now by soldiers is that they are always going to have power,” said John P. Howell, project director of soldier systems integration at the Army’s project manager soldier warrior. “We are trying to fix that assumption and make it a fact.”

Soldiers on foot need to have enough portable energy with them to make it through a 72-hour mission without resupply. The plethora of devices they carry with them is growing and making that harder — unless the Army wants to simply burden them with more batteries.

“It necessitates some fairly creative operational processes to make sure that a soldier stays powered up during an entire 72-hour operation,” Howell said.
The power challenge continues to grow as soldiers are asked to carry more electronics with them on missions. Those might include GPS, gun sights, night vision goggles and radios. The latter is using up the most energy, Howell said. 

“Radios are now not only just voice communication devices. They are constantly on, providing input and output of data and position location,” Howell said. “They are very power hungry.”

At the beginning of the Gulf War in 1991, a typical Army platoon required 1.74 kilowatts per hour to run their devices. Ten years later at the outset of operations in Afghanistan, it was 2.07 kilowatts per hour. Today, it has swelled to 31.35 kilowatts per hour, Howell said.

To get at the problem, the Army has developed a power management system that moves energy around a soldier as needed, rather than each different device being energized by its own battery or batteries.

The single power source is a lithium-ion battery that conforms to the body and is worn inside a breastplate. Currently, that system is only supplying about half of the energy needed on a 72-hour mission. The soldier must carry a charged-up spare in his or her rucksack, which adds to the weight burden.

“Despite the technology — and as good as it is right now, … we’ve still got a long way to go,” Howell said.

To make matters more complicated, project manager soldier warrior wants to make the power management system pull double duty and move data around the soldier.

Basically, it is a router for power, Howell said.

There are seven inputs and outputs to distribute power across all devices and a small processor to assist it. It’s light, but rather bulky due to hardening and ruggedization, he added. It allows power and data to be intelligently distributed around a soldier so he or she doesn’t have to think about it, he said.

“We’re hoping to make it smaller, more compact and more powerful,” Howell added. 

Not all the devices can currently connect to the power management system. The program is trying to minimize independent power sources, he noted.
Data is another story and the program is looking for solutions on how to do that efficiently — and potentially wirelessly — around the soldier, Howell said.

“Our biggest challenge is the ability to effectively move power and data around the soldier platform,” he said. The power management system must be compact and containerized so the soldier doesn’t have to think about it and it doesn’t get in the way, he said.

To help the program manager understand the typical needs of a platoon on a 72-hour mission, it is holding an exercise at Fort Benning, Georgia, this summer called the initial power expeditionary survey.

It will test concepts of operations on how an infantry platoon can survive with power sources they bring with them and their ability to recharge batteries over 72 hours.

“You’re probably thinking: ‘Hasn’t somebody already done this?’” he said. The answer is no.

“Soldier power technology and the requirements have moved so quickly over the past few years that the con-ops have not kept up,” he said.

The exercise will help the Army come up with standard operating procedures for a small dismounted unit, plus modeling to provide a baseline requirement for all soldier equipment in the field over the 72-hour mission.

It will also help industry understand what the Army needs for power sources or how to better use what it has on hand, he said. 

Can power-hungry radios be used in ways that that can reduce energy needs? he asked. For example, they can be put in listen-only mode, Howell noted.
One way to get at the problem is to recharge batteries on the go.

The Army is looking at two methods to use kinetic energy created by the soldier’s body movements to keep batteries powered up.

Julianne Douglas, energy harvesting technology lead at the Army Communications-Electronics Research, Development and Engineering Center, said one method is to use the movements of a rucksack as a soldier walks.

If the program is successful, it would reduce the number of batteries required, lessen the logistical burden and possibly increase a mission duration longer than 72 hours.

“The goal there would obviously be austere locations, so you can go out and not be resupplied as long as you’ve got food and water,” she said. 

The ultimate goal of the effort is a net-zero energy burden, so all batteries are charged as the platoon moves, she said.

The rucksack would have a suspended spring system inside that would move up and down and use the kinetic energy to generate power. That would in turn recharge the conformal battery worn under the breastplate. The power management system would distribute the power as needed. 

There are similar energy harvesting programs in the works with knee braces, ankle braces and boot heels.

A typical person walks at about three miles per hour. However, a fully loaded soldier walks slower.

“When you’re carrying upwards of 100 pounds on your back, you really don’t walk that fast,” she said. The cadence will vary during a mission. Dealing with these variables and “tuning” the system to provide a steady stream of power is one of the program’s big challenges, she said.

The program initially hopes to generate 10 watts of power with a 10-pound system, then later 15 watts at five pounds. Another goal is to make sure the soldier is not bothered by the system, she said. They shouldn’t be conscious that it is working.

Howell said, as far as energy harvesting technologies go, they just haven’t caught up to requirements yet. Still, he was confident that they will.
Energy harvesting backpacks were expected to be delivered for testing to Aberdeen Proving Ground, Maryland, in May, Douglas said.

“If we can maximize the power output and prove the art of the possible with harvesting and still have it be pretty ergonomic, then we’ll know that the juice was worth the squeeze,” Douglas said.


Topics: Energy, Science and Engineering Technology

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