Wave-to-wire modeling and design of an electromagnetic energy harvester for autonomous monitoring buoys

Embedded electromagnetic wave energy harvesters represent an attractive solution for enabling long-term autonomous operation of marine monitoring buoys. This paper presents a comprehensive analytical modeling and design framework for a track-cylinder electromagnetic wave energy harvester based on a rolling magnetic cylinder moving along a track equipped with distributed coil pairs. The proposed framework integrates buoy dynamics, rolling cylinder mechanics, position-dependent electromagnetic transduction, and power-conditioning electronics to predict harvested energy and average output power under realistic sea conditions. A closed-form condition enforcing full-travel operation, which maximizes cylinder velocity and activates all coil pairs, is combined with a closed-form energy estimate to derive normalized power maps for track sizing as a function of wave period and pitch angle. Unlike commonly adopted wave-slope approximations, buoy pitch motion is obtained from a frequency-domain hydrodynamic model, enabling more accurate prediction of the electromechanical energy conversion process. An electronic interface based on independent rectification of each coil pair and a common boost converter with regulated input voltage is introduced to efficiently manage pulsed source waveforms. Experiments performed on a prototype featuring a 200-mm track and six coil pairs, driven by actuator-generated pitch motions corresponding to sea states with periods from 1 to 4 s and wave heights from 0.3 to 0.9 m, show close agreement between analytical predictions and measured extracted energy and mean power, validating the proposed electromechanical model and design methodology.