Troops could look to their soles for power.

• Author: Parsons, Dan

As American combat gear becomes ever more sophisticated, the problem of how to power weapon sights and communication equipment has become acute.

The tactical advantages electronics provide evaporate when batteries run dry in the field. High-tech equipment, without power, becomes dead weight.

"More and more electronics give U.S. troops a distinct advantage over enemies," said Michel Barton, CEO of STC Footwear which has helped devise energy harvesting combat footwear "But when he is fighting the Taliban without it, it is a one-to-one man equation."

Advanced soldier gear and the batteries to power them add weight that can slow down and potentially injure troops in the field. The Holy Grail solution is a power source that needs no recharging, adds little weight to a soldier's load and is virtually invisible to the wearer.

STC Footwear and Lockheed Martin Corp. have come closer than many companies looking for that elusive combination of attributes by fitting a kinetic charger into the standard-issue boots soldiers and Marines wear.

Kinetic Boot, as it is called, adds only ounces and converts energy from the wearer's gait to energy that powers all of his or her electronic equipment.

"By design, we decided to find out how we could harvest the energy of a man walking," Barton said. "For the end user at the end of the day, the only difference is the two or three ounces. For the wearer, there is exactly no other effort added or required."

Every ounce of battery weight removed from the load troops carry lightens the burden on their muscles and can be replaced with water and ammunition. Kinetic Boot fits within the existing structure of a combat boot, harnessing the otherwise wasted energy generated by ordinary walking or running.

As a human walks, the foot is lifted then the sole pressed to the ground, energy is exerted through muscle contraction and expelled as heat, the way a runner burns calories while rounding the track. That heat energy is lost to the sole or the knee joint, Rebecca Schwartz, nanotechnology lead at Lockheed Martin, told National Defense. Simply walking with the Kinetic Boot captures much of the wasted heat and transforms it into energy to power wearable electronics.

"There is no change in the gait," Schwartz said. "You create energy when you walk, but it is wasted. It's not going to have a huge impact to the feel of the walk. In that natural step, there is energy that your leg loses when it makes contact with the ground. It is...