When you take a walk, you normally wouldn’t think about the amount of energy that is generated and dissipated with each step. That is, unless you’re a researcher. Scientists from three universities have joined forces to create an energy-catching knee brace that gives new meaning to the phrase “power walking”.
Researchers from the University of Pittsburgh, University of Michigan and the Simon Fraser University in Burnaby, British Columbia, helped to author a report on the device, published in the February 8th issue of the journal Science. The wearable brace works in a manner similar to the braking system of a hybrid electric car. In a hybrid car, kinetic energy is collected each time a person hits the brake pedal. With this new brace, energy is collected each time the tendons in a person’s knee swing the leg forward.
Though energy is generated and dissipated throughout the body as a person moves, the knee’s movements in particular are ideal for this type of device. In initial studies on the 3.5-pound prototype, a person walking at the leisurely pace of 2.2 miles per hour can generate approximately 5 watts of electricity with a brace affixed to each leg. That’s enough to power 10 cell phones!
But the brace is still in the prototype phase, and researchers hope to make it more lightweight and user-friendly. Part of the challenge lies in making a device light enough for practical application but powerful enough to produce enough juice. Other types of human-powered generators haven’t been very successful. Scientists created a small generator that slips into a shoe, but the plan was scrapped after they discovered it wasn’t collecting enough power.
Hand-crank power generators are also making their way onto the scene, likely due to the world’s newfound focus on green energy. But, one disadvantage of hand-powered generators is that they require more input from the user. The brace, conversely, doesn’t require any additional action outside of walking. In fact, the brace is so efficient that users expend less than one watt of energy wearing the brace although it harvests one full watt of power.
In terms of real-world use, researchers envision a lighter version of the brace making its way onto the battlefield. Currently, military members carry pounds of disposable batteries for their electronic devices. When space for necessarily items is limited, that can create a major problem. Scientists say similar mechanisms could aid those with prosthetic knees and other implantable devices such as pacemakers or neurotransmitters that today require a battery. Eventually, the market could be expanded to long-distance joggers, hikers and adventurers who may not have immediate access to a power source.
