for National Geographic News
A backpack that generates its own electricity may soon allow rescue workers, explorers, and soldiers to power their equipment while on the go, a team of scientists reported today.
The backpack will derive its power from the motion of the person carrying it.
The invention, known as the suspended-load backpack, frees handheld computers, cell phones, and dozens of other devices from the constraints of limited battery life and the reach of the power grid.
"To have electricity is crucial in remote places," said Lawrence Rome, a biologist at the University of Pennsylvania in Philadelphia who led the device's development. Rome's research focuses on how muscles function while walking and running.
The idea for the backpack grew out of a request from the U.S. Office of Naval Research to develop a way to generate electricity from body movements.
At the time, U.S. soldiers in Afghanistan were bogged down with 80-pound (36-kilogram) packs full of GPS instruments, night-vision goggles, and other gear that required an additional 20 pounds (9 kilograms) of batteries.
"Once I started to design the pack, I realized that everyone has the same problem," Rome said. Explorers surveying the rain forest in Africa and field scientists cataloging microbes in Chile, for example, need electricity to power their equipment.
The backpack is based on the external-frame design once popular with backcountry trekkers. With loads weighing between 44 and 84 pounds (20 to 38 kilograms), the pack can generate more than seven watts of electricity from the up-and-down movement of the cargo compartment.
Seven watts is sufficient to power a handful of electronic gadgets at the same time, including a cell phone, an MP3 player, a handheld computer, night-vision goggles, and a water purifier.
Rome and his colleagues describe the backpack in tomorrow's issue of the journal Science.
How It Works
When walking, a person's hip moves up and down about two to three inches (five to seven centimeters) with each step. The movement occurs as the body vaults over each foot.
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