Laboratory characterization of a liquid metal MHD generator for ocean wave energy conversion

Harnessing ocean wave energy is an old challenge that has gained momentum in recent years. In this paper, we present the flow and electrical characterization of a prototype of an alternate liquid metal magnetohydrodynamic (MHD) generator at a laboratory scale which has the potential to make use of the energy of marine waves for its conversion into electrical energy. The eutectic alloy Galinstan, used as a working fluid, was driven in oscillatory motion in a duct of a rectangular cross-section exposed to a transverse magnetic field generated by permanent neodymium magnets. The electric current induced by the motion of the liquid metal in the magnetic field was collected through copper electrodes and delivered to the load. The oscillatory axial velocity component along the duct was measured using ultrasonic Doppler velocimetry for different oscillation frequencies. In turn, the output currents and voltages were measured for different operation conditions and the electric power and efficiency were estimated from experimental measurements. The coupling of this generator to a wave energy converter (WEC) is discussed.