Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Design of a Direct-acting Electromagnetic Wave Energy Capture Device with Boosted Capturable
Vibration Frequency
Hao Tian, Boyang Zhou, Yongjun Gong
Department of Mechanical Engineering, Dalian Maritime University
Liaoning Key Laboratory of Rescue and Salvage Engineering, Dalian Maritime University
Dalian, Liaoning, China

based counterparts, supplying electric power through transmission lines
to the ocean deployed data buoy are usually impractical due to its far
distance away from the centralized power generators on the mainland(Albaladejo, Sánchez, Iborra, Soto, López and Torres, 2010). The current
sensor buoy power systems usually employ photovoltaic panels andbatteries, yet their power output is becoming more of a threshold against
the ever-increasing complexity of onboard metrology instruments,
especially at long term service (Zhou and Yi, 2013). Moreover, whensome battery equipped data buoys are lost or sunk in the ocean due tosevere weather or poor maintenance, the environmental concerns of suchdevices may rise (Nolte, Ertekin and Davis, 2013).

ABSTRACT
Harvesting ocean wave’s kinetic energy is a promising way to supply
electricity to the smart ocean network. Also, since the smart ocean
network is distributed sparsely in the scale of hundreds of kilometers,
supplying electricity onsite would be most efficient. It is well studied
that the ocean is abundant in wave kinetic energy, however, the low
frequency of the wave is often out of many traditional energy conversion
devices’ optimal performance region. To tackle this issue, traditional
wave capture devices are often of large scale, or semi-permanently
anchored, which have almost no constraints on the size of the devices.
Hence, the size of the traditional device is advantageous in the capture
efficiency as the kinetic energy absorber can be much larger, andadvanced energy storage schemes can be easily employed. Yet, mobilityof the traditional devices may still be the limiting factor. To generate
electricity onsite, small form factor wave energy capture devices must
work with constrained size of the kinetic energy absorbed, and theenergy storage means is very limited. As a result, small form factor wave
capture device has to boost the frequency of capturable motion, to drive
the electrical generation device in its most efficient region. In this paper,a direct-acting electromagnetic wave energy capture device is proposed,designed, and simulated, with key performance indicators optimized.
The proposed device architecture is similar to a linear motor, but has thecapability of boosting vibration frequency of the captured motion withthe help of a designed fluid power transmission circuit to boost thecapturable motion frequency. Initial design analysis has shown thedevice is capable of boosting the capturable motion frequency over theincident wave frequency by a factor of 10.

One way to solve this problem is to integrate the energy acquisition
systems onto the data buoys (Joe, Kim, Wi, Kwon and Yu, 2014). Wave
as an abundant and widely available kinetic energy source, it is wellstudied since the last century, mainly for large stations or near shore
applications (Vezzoli, Ceschin and Diehl, 2015). Although the existingstationary power generation device has the characteristics of high-power
generation efficiency and stability, it mainly provides daily life power
for nearby islands or sites, but cannot offer deep sea serviceability.
Additionally, due to high cost and large form factors, the existing PTO(power take-off) devices employed in such stations cannot be directly
applied to the data buoy (Duckers, 2004). Therefore, the challenges forthe application of PTO device to the data buoy are the miniaturization,
obtaining high electric energy in the smallest possible, while maintaining
reasonable costs (Joe, Kim, Wi, Kwon and Yu, 2017). Currently, forsmall form factor PTO researches, there are many approaches, throughmechanical power transmission systems (Lai, 2020), through new power
generation effects such as nano tribology (Wang, 2013), or via the mosttraditional hydraulic energy storage (Falcã, 2007). Through mechanicalfrequency up-conversion, the effective power generation frequency canbe improved. Li et al. proposed a wave conversion system with ballscrew mechanism as PTO driving mechanism (Li, Chen, Liang andNgo, 2020). Tan et al. developed a two degree of freedom (2-DOF)
string driven rotor to convert the ultra-low frequency vibration into thehigh-speed rotating motion of the rotor, so as to make effective use of
the ultra-low frequency mechanical energy (Tan, Fan, Guo and Wen,

KEY WORDS: Power take-off; maximum power point tracking;system modeling and simulation; hydrodynamic modeling.

INTRODUCTION
As an important part of the marine sensor data network, data buoys arewidely used in ocean monitoring applications. Compared with the land-527