Comparative Study of Buoy-Actuated Energy-Harvesting Devices for Submersible Sensors

Continuous electrical power supplies are crucial for the success of deep-sea missions given the need for power to energize sensors, actuators, or light sources to monitor activities in deep murky waters. Therefore, viable renewable energy sources installed at seabed could be the solution for the success of these types of missions. In this work, three types of energy harvesters tethered to a buoy through a long inflexible cable for operation at seabed are presented. The first harvester uses an alternator to produce electricity to charge a battery pack whereas the second one is based on a mass-magnet-spring translational system. In addition, the third harvester (base-excitation type) uses periodic waves to linearly move the magnet via a inflexible rod. The harvesters are actuated by the motion of the buoy resulting from the waves at the surfaces of the sea/ocean. The simulation results show that the alternator-based harvester was capable of producing 3,650 W, which is enough to power a small monitoring station. Furthermore, this power level is based on 1.0-m-high waves. Effect of the wave amplitude ($Yo$) on the induced electrical power (PW) for charging the batteries and the actual mean wave height in the test location will be more indicative of the power available for recharging the batteries. However, the mass-spring harvester and the base-excitation type harvester produced only 0.000135 W and 0.537 W, respectively.