Tomorrow’s ranchers may be able to monitor their animals’ health from the comfort of their home—and completely off the grid. By attaching small, pendulum-based devices to the ankles of cattle, Chinese researchers believe they’re one step closer to developing self-powered “smart ranches.”
Renewable energy like solar or wind likely comes to mind sooner than kinetic energy. However, the researchers argue in a new study published Thursday in iScience that the movement of livestock and other ranch animals throughout the day produces vast quantities of energy that’s being wasted. So they designed and conducted preliminary tests of what the researchers termed a “kinetic energy harvester.”.
“There is a tremendous amount of kinetic energy that can be harvested in cattle’s daily 9movements, such as walking, running, and even neck movement,” Zutao Zhang, a co-author of the research and an energy researcher at Southwest Jiaotong University in China, said in a press release. Harnessing this untapped energy source can then power wireless sensors on cattle that can inform a rancher about their herd’s health.
Zhang and his collaborators designed shell-shaped wearables with a 3D-printed plastic case. Inside, a pendulum is able to rock side to side. Two repelling magnets stabilize it, while an array of magnets and a coil at the bottom of the device turns the energy of the pendulum’s motion into electrical energy.
After building a prototype, the researchers attached it to a motor-powered crank that mimicked a cow (or person) walking. The shell wearable produced an average power of 7 milliwatts and required a frequency of 2 Hertz—more power with a lower frequency of back-and-forth motion than previous studies’ designs for kinetic energy harvesters, meaning the new device is more efficient and better adapted to real-world conditions. The researchers showed that their device could charge a capacitor and power 140 LEDs with the energy it harvested from the crank’s motion.
Next, they strapped the device to a person’s ankle, finding that climbing the stairs produced enough energy to light up the LEDs bright enough to replace reflective stickers on clothing, like the kind that bikers or runners might wear.
Of course, the study wouldn’t be complete without hooking the device up to a bovine experimental subject. A cow wore the device on its ankle while in a feedlot and grazing in a pasture. Over the course of a day, the researchers expected that their device could harvest almost 30 Joules from a cow in a feedlot, and over 100 Joules from one roaming a pasture. This power could be stored in a battery and used to power monitoring technology, like GPS, pulse, and temperature sensors.
Being able to monitor cows’ vitals in this way wouldn’t just save energy, Zhang said. Tracking health statuses in real time can help ranchers prevent costly diseases and improve the entire ranch’s efficiency.
The researchers wrote in the study that they want to test their harvesting device on more cows and experiment with different health monitoring devices that could be powered with kinetic energy in the future. Ultimately, devising ways to recover wasted kinetic energy could go far beyond cows and help humans save energy while working out, getting around, and going about their lives.
“Kinetic energy is everywhere in the environment—leaves swaying in the wind, the movement of people and animals, the undulation of waves, the rotation of the earth,” Zhang said. “We shouldn’t let this energy go to waste.”
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