Design and Testing of a Mechanical Power Take-off System for Rolling-type Wave Energy Converter

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Design and Testing of a Mechanical Power Take‑off System for Rolling‑type Wave Energy Converter Yichen Jiang1 · Yuhao Peng1 · Yuan Sun2 · Zhi Zong1 · Lei Sun1  Received: 26 November 2019 / Revised: 26 June 2020 / Accepted: 6 August 2020 © Korean Society for Precision Engineering 2020

Abstract Salter’s Duck can convert wave energy to mechanical energy with high efficiency up to 90%. The limitations and challenges in the usage of Salter’s Duck for energy production include preventing hydraulic system from the risk of leaking hydraulic oil and removing complex huge fixed bracket. This paper presents the conceptual design and an experimental investigation of a mechanical power-take-off (PTO) system for the floating Salter’s Duck. The PTO system is fully installed inside of the Salter’s Duck. It consists of double counter-rotating flywheels converting the bi-directional rotation of the wave energy converter into a stable unidirectional rotation that drives a rotary generator to produce electricity. The bi-to-unidirectional function is achieved through inertial wheels, thus the novel PTO system is free of large supporting structures and hydraulic cylinders. In this paper, a detailed conceptual PTO design is proposed firstly. Further, the influence of the swing amplitude and rotation period of the wave energy converter on the power extraction efficiency is investigated. Then, the influence of the electrical load on the power-extraction efficiency is researched. In the end, the effect of the speed increasing ratio on the mechanical efficiency is examined. The experimental results show that the new type of generator mechanism can produce electricity stably. Keywords  Wave energy converter · Inertial generation device · Power extraction efficiency · Mechanical efficiency · Load characteristics

1 Introduction 1.1 Research Background The ocean is rich in clean energy, such as wave energy, tidal energy, salt water difference energy, and temperature difference energy [1], that should be developed and utilized. In particular, ocean wave energy has the greatest potential for development. According to the forecast report published by the International Energy Organization, the amount of Electronic supplementary material  The online version of this article (https​://doi.org/10.1007/s4068​4-020-00253​-z) contains supplementary material, which is available to authorized users. * Lei Sun [email protected] 1



School of Naval Architecture Engineering, Dalian University of Technology, Dalian 116024, Liaoning, China



State Key Laboratory of Robotics, Shenyang Institute of Automation, Chinese Academy of Sciences, Shenyang 110016, Liaoning, China

2

available wave energy on Earth can reach 2–2.5 billion kilowatts [2–4], which far exceeds the present total global power generation. Wave energy, which is the sum of kinetic energy and potential energy of ocean waves, is the most widely distributed renewable energy source in the ocean [5, 6]. It is clean and non-polluting, and i