When you walk with a backpack, do you know how the things inside move from side to side? Now scientists have figured out how to tap into that movement to produce electricity.
Picture a pendulum(摆锤) fixed to a backpack frame and stabilized with springs on either side. The pack's weight is attached to the pendulum, so the pendulum swings side to side as you walk. Then a machine is driven by that swinging movement, and produces electrical current to charge a battery.
Volunteers carried the pack while walking on a running machine and wore masks to measure the flow of O2, and CO2. When the volunteers were walking with the slightly swinging 20-pound load, the device did not significantly affect their metabolic(新陈代谢的) rate compared to when they carried the same weight fixed in place. In fact, the energy-harvesting pack reduced the forces of acceleration they'd feel in a regular pack, which might mean greater comfort for a long hike. And the device did produce a steady trickle(涓流) of electricity. If you up the load to 45 pounds, it could fully charge a smartphone only after 12 hours. The details are in the journal Royal Society Open Science.
The device produces electricity from human movement and has been identified as a workable solution to providing a renewable energy source for portable electronic devices. It is particularly useful to those who work in remote areas, as these people often carry a lot of weight in a backpack for their exploration.
But here's a real conundrum: the energy-harvesting device currently weighs five pounds. The researchers say that's about four pounds too many to be a smart alternative to batteries. So they hope that more research lets them lighten the load so that they can ensure the pack charges your phone up without weighing you down.
