Ferrohydrodynamic System for Energy Harvesting

Abstract

Energy harvesting has been of keen interest to researchers and many energy harvesting methods were reported recently. In particular, there has been growing interest in an energy harvesting method which is based on electromagnetic energy. Most of the energy harvesters have been developed in the laboratory without practical applications. A ferrohydrodynamic system which utilizes movement of air droplets in a ferrofluid is proposed as an energy harvesting platform in this study. According to Faradays law, relative motion under a magnetic field can cause a change of magnetic flux, which induces electromotive force in the surrounding coils. A ferrohydrodynamic system was prepared to investigate possibility of energy harvesting through Faradays law. Ferrohydrodynamically induced voltage and current were measured as a function of the flow rate of air, the magnetic field(H), and the magnetization(M). First, it was observed that the measured output current and voltage were in the same range regardless of the flow rate of air. Second, it was observed that as the magnetic field was increased by changing the number of magnets, output voltage and current increased. Finally, output voltage and current were measured by using two types of ferrofluid which consist of different saturation magnetization. It was observed that as saturation magnetization of a ferrofluid increased, output current and voltage were increased. Numerical simulation with the commercial code, COMSOL, demonstrated that the ferryhydrodynamic system generates output voltage and current as expected. Magnetorheological and magnetodynamic effects of the ferrofluid on energy harvesting were characterized in this study. It was found that the ferrofluid showed shear thinning behavior and magnetoviscous effect under magnetic field.