Enhancing power generation of floating wave power generators by utilization of nonlinear roll-pitch coupling

Abstract

We propose utilization of the nonlinear coupling between the roll and pitch motions of wave energy harvesting vessels to increase their power generation by orders of magnitude. Unlike linear vessels that exhibit unidirectional motion, our vessel undergoes both pitch and roll motions in response to frontal waves. This significantly magnifies the motion of the vessel and thus improves the power production by several orders of magnitude. The ocean waves result in roll and pitch motions of the vessel, which in turn causes rotation of an onboard pendulum. The pendulum is connected to an electric generator to produce power. The coupled electro-mechanical system is modeled using energy methods. This paper investigates the power generation of the vessel when the ratio between pitch and roll natural frequencies is about 2 to 1. In that case, a nonlinear energy transfer occurs between the roll and pitch motions, causing the vessel to perform coupled pitch and roll motion even though it is only excited in the pitch direction. It is shown that co-existence of pitch and roll motions significantly enhances the pendulum rotation and power generation. A method for tuning the natural frequencies of the vessel is proposed to make the energy generator robust to variations of the frequency of the incident waves. It is shown that the proposed method enhances the power output of the floating wave power generators by multiple orders of magnitude. A small-scale prototype is developed for the proof of concept. The nonlinear energy transfer and the full rotation of the pendulum in the prototype are observed in the experimental tests.

A Real-Time Detection System for the Onset of Parametric Resonance in Wave Energy Converters

“…This type of nonlinear Froude-Kylov force model has subsequently been used in [29][30][31][32][33][34] to investigate parametric resonance in WECs. Other nonlinear hydrodynamic modelling approaches include only modelling the restoring force nonlinearly, rather than the entire Froude-Krylov force [35][36][37][38][39][40]. Modelling parametric resonance has also been explored through high-fidelity CFD simulations [41].…”

Revelatory Case Study for the Emergence of Powerships: The Floating Power Plant Innovation for Rural Electrification

“…Literature Review (Yerrapragada et al, 2017;Platzer and Sarigul-Klijn, 2018;Reis and Gallo, 2018;Goswami et al, 2019;Ranjbaran et al, 2019;Stiubiener et al, 2020;Hu et al, 2020;Li et al, 2020;Konur et al, 2020).…”

“…In this study, a small-scale autonomous hydrofoil boat construction is demonstrated for proposed technology testing. In an effort to increase efficiency in power generation by utilisation of nonlinear roll-pitch coupling on a ship, Yerrapragada et al (2017), used a small-scale ship to describe the advantages of this system in detail. Reis and Gallo (2018), described power production from waste heat by an organic Rankine cycle, aimed at increasing the thermal efficiency and minimising greenhouse gas emissions.…”

Post-grazing dynamics of a vibro-impacting energy generator

“…The idea behind parametrically excited systems is the use of large system responses near instabilities, e.g. see [6][7][8][9][10][11][12][13][14][15], among others. Within the huge range of nonlinear EH systems, there are some particular themes of note; natural single-potential nonlinearities (classical continuous nonlinear systems like the Van-der-Pol or Duffing oscillator, a pendulum, etc.…”