If someone told you he could generate energy from a phenomenon called wake galloping, what would your face change into? Well, two researchers from South Korea invented a device that does that and that uses a specific type of unstable airflow, wake galloping, which usually forms around bridge cables and other cylindrically-structured buildings.
Wake galloping is a vibration that affects all of the forementioned types of buildings exposed to airflow. When the wind passes a horizontal cylinder, eddy currents called wake vortices are created on the lee side. These induce a lifting force on a cylinder in the path of these eddies – but only if the two have the same diameter and the second cylinder is three to six diameters away from the first. The lift is counteracted by the leeward cylinder’s weight, which pulls it back down again, creating an up-down movement for as long as the wind continues to blow.
To harness the energy that bounces the cylinder, Hyung-Jo Jung and Seung-Woo Lee at the Korea Advanced Institute of Science and Technology in Daejeon, South Korea built a device that contains two perspex rods, both 85 centimeters long and 5 centimeters in diameter. The space between them respects the condition to form wake galloping, and they attached the second rod (the leeward one) to a magnet which moves with the rod, up and down, inside a copper coil, generating electricity.
Where classic wind turbines fail, the wake galloping device succeeds. In winds having the speed of 2.5 to 4.5 meters per second, they got 0.5 watts of electricity, and the researchers think that by improving the coil and magnets, the output could also improve.
The first immediate applications that came to their minds were powering the bridges’ street lighting, or monitoring a structure’s health using wireless sensors powered by this kind of devices. The scientists are now thinking how they could better commercialize their device and in which markets. A similar approach had been used in the 1940s, but had subsequently failed.