What is energy harvesting? Energy harvesting, also known as energy scavenging, is the process of collecting small amounts of ambient energy from an outside source and repurposing it to power small electrical devices. Ambient energy is energy that is natural, non-electrical in nature, and is self-regenerating or renewable.
Sources of ambient energy can come from radio frequencies, solar, vibration, and humans. That’s right, our own bodies are natural energy generators. Why human energy? Human energy is always available, has little environmental impact, doesn’t require special fuel and it’s basically free.
Why is it important?
Energy harvesting is nothing new, think windmills and waterwheels, but as we look to find new sources of renewable energy, harvesting human energy has gained real traction. recently gotten considerable attention.
Harvesting energy helps to supplement power from energy sources like fossil fuels which are unsustainable and costly to our environment. Another benefit behind this type of technology is the ability to power small devices. According to author Wei-Hsin Liao, professor in the department of mechanical and automation engineering, “Self-powered equipment can enable users to get rid of the inconvenient daily charge. This energy harvester would promote the development of self-powered wearable devices."
How do you harvest energy from a human knee?
Researchers at the Chinese University of Hong Kong developed a device that can harvest energy from the knee to generate electricity. Researchers used a smart macro-fiber material that generates electricity from any type of bending and created a slide-cranking mechanism - kind of like a motor. The prototype weighs less than a pound and was tested on people walking between 1 and 4 mph.
The continuous back-and-forth from walking and flexing the knee will bend the device enough to generate electricity. As Liao puts it, “The energy harvester captures biomechanics energy through the natural motion of the knee. That means every time the knee flexes in a continuous back-and-forth movement, the device bends and generates electricity.”
Previous attempts at harvesting energy from the knee used energy created by vibrations, but they were never efficient; humans just don’t walk fast enough. Laio noted that, “The frequency of human walking is quite slow, which significantly decreases the energy-harvesting capability.”
After further testing and prototyping, researchers are hoping to commercialize the technology. Self-powered gps technology has a very practical use for outdoorsmen, climbers and mountaineers who need to keep electronic items charged while trekking through remote locations without electricity.
The article, "Macro fiber composite-based energy harvester for human knee," is authored by Fei Gao, Gaoyu Liu, Brendon Lik Hang Chung, Hugo H. Chan and Wei-Hsin Liao. The article appeared in Applied Physics Letters on July 16, 2019 (DOI: 10.1063/1.5098962) and can be accessed at http://aip.scitation.org/doi/full/10.1063/1.5098962.