University of Wisconsin-Madison researchers have found that we can literally “run” our portable electronic devices – or at least “take steps” to recharge them. In experiments, two mechanical engineers have been able to capture the energy a person produces by jogging or walking, and convert it into the electrical power needed to operate everything from cell phones to laptops and tablets.
In a paper appearing this week in the journal Nature Communications, Tom Krupenkin and J. Ashley Taylor describe a new energy harvesting technology that can be installed in the sole of a shoe –“a revolutionary human-gait energy scavenger“– which promises to dramatically reduce our dependence on batteries and, instead, capture the energy of human motion.
Simply explained, the mechanical energy produced by humans during walking, which is normally simply lost as heat, is captured and converted into electrical power ready to be used by wireless personal electronics. “It’s like having an electrical power generator and a Wi-Fi hot spot under the heel!“ the researchers said.
“Humans, generally speaking, are very powerful energy producing machines,” explained Krupenkin, a UW-Madison professor of Mechanical Engineering. “While sprinting, a person can produce as much as one kilowatt (kW) of power.”
Even a small fraction of that energy, Krupenkin points out, would be enough to power a host of mobile electronic devices – everything from laptop computers to cell phones to flashlights. “What has been lacking is a mechanical-to-electrical-energy conversion technology that would work well for this type of application,” he said.
Solar power, the researchers said, can also be used to power portable electronics – but, unlike human motion, direct sunlight is usually not a readily available source of energy for mobile electronics users.
In their Nature Communications report, Krupenkin and Taylor describe a novel energy-harvesting technology known as “reverse electrowetting,” a phenomenon discovered by the Wisconsin researchers. The mechanical energy is converted to electrical energy by using a micro-fluidic device consisting of thousands of liquid micro-droplets interacting with a novel nano-structured substrate.
This technology could facilitate a novel footwear-embedded energy harvester that captures energy and converts it into up to 20 watts of electrical power. Unlike a traditional battery, the energy harvester never needs to be recharged, as the new energy is constantly generated during the normal walking process.
The initial development of this technology was funded by a National Science Foundation Small Business Innovation Research grant, as well as the European Research Council (ERC).
In their work, Taylor and Krupenkin were inspired by severe limitations that current battery technology imposes on mobile electronics users. As any cell phone or laptop user knows, heavy reliance on batteries greatly restricts the utility of mobile electronic devices in many situations. What's more, many types of mobile electronics are used in remote areas of the world, where electrical grids for recharging batteries are often not available. Cell phone users in developing countries often have to pay high fees to recharge.
Similar problems face military and law enforcement personnel. Modern soldiers, for example, head into the field carrying as much as 20 pounds of batteries to power communications equipment, laptop computers, and night-vision goggles.
The energy generated by the footwear-embedded harvester can be used in one of two ways:
It can be used directly to power a broad range of devices, from smartphones and laptops to radios, GPS units, night-vision goggles, and flashlights.
Alternatively, the energy harvester can be integrated with a Wi-Fi hot spot that acts as a “middleman” between mobile devices and a wireless network.
The latter type of application allows users to seamlessly utilize the energy generated by the harvester without having to physically connect their mobile devices to the footwear. This configuration dramatically reduces power consumption of wireless mobile devices and allows them to operate for a much longer time without battery recharge, the Wisconsin researchers said.
“You cut the power requirements of your cell phone dramatically by doing this,” said Krupenkin. “Your cell phone battery will last 10 times longer.”
They are currently working to produce a prototype device that can be fitted into the sole of a shoe, which they expect will be ready in two years.
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Cheryl Kaften is an accomplished communicator who has written for consumer and corporate audiences. She has worked extensively for MasterCard (News - Alert) Worldwide, Philip Morris USA (Altria), and KPMG, and has consulted for Estee Lauder and the Philadelphia Inquirer Newspapers. To read more of her articles, please visit her columnist page.Edited by
Jennifer Russell
