Cows on farms could soon have their health, reproductive readiness and location monitored by smart technology powered by the kinetic energy of the animal’s movements. Devices that monitor the health of each cow or keep them within invisible fences are already used on farms but these smart tools are often powered by chemical batteries, which add to energy used by an emissions-intensive industry. Alternatives such as solar-powered monitors – deployed in Britain to create fenceless grazing for cows – may depend on the weather. But researchers from China writing in the journal iScience have designed a wearable smart device for cows that captures the kinetic energy created by their smallest movements. “There is a tremendous amount of kinetic energy that can be harvested in cattle’s daily movements, such as walking, running, and even neck movement,” said Zutao Zhang, an energy researcher at Southwest Jiaotong University and co-author of the paper. His team’s design uses a motion-enhancement mechanism made up of magnets and a pendulum to amplify small movements made by cows. “Our kinetic energy harvester specially harvests the kinetic energy of weak motion,” said Zhang. The technology is housed in a scallop-shaped shell, which is attached to a cow’s ankle or neck. An electromagnetic generator converts kinetic into electrical energy. This is stored in a lithium battery which powers the wireless monitors. Information can then be gathered, including the amount of exercise the animal gets, reproductive cycles, disease, oxygen concentration, air temperature, humidity and milk production, helping ensure good health and improving breeding productivity. Researchers tested the devices on humans and found that a light jog was enough to power temperature measurement in the device. They see future applications in sports monitoring, healthcare and smart home systems. “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 –these phenomena all contain a lot of kinetic energy,” said Zhang. “We shouldn’t let this energy go to waste.”