Energy harvesting from a cylinder undergoing vortex-induced vibrations

Vortex-Induced vibrations (VIVs) occur throughout industry and nature, and are typically seen as a problem as they can lead to fatigue damage. However, VIV also represents a source of renewable energy if the kinetic energy of the structure can be harvested. This approach has many benefits over conventional wind turbine technologies, including low space requirements, potentially simpler design, leading to lower installation costs, and most notably, the oscillation frequency can be tuned such that the aerodynamic noise generated occurs outside of the range of human hearing, preventing noise pollution and allowing this technology to be employed in urban environments. We design a device that harvests energy from a cylinder free to move in the lift direction. Power extraction is achieved through induction, with magnets attached to a leaf spring. Our design allows us to control the magnetic damping and the natural frequency of the system in order to optimise the efficiency. We vary the reduced velocity throughout the VIV regime and measure both the amplitude response and the power extraction, exploring the influence of temporal variations in the amplitude of VIV and the magnitude of damping on the efficiency and the potential of this technology for large-scale power generation.