Journal ArticleDOI
Wave-Energy Conversion Through Relative Motion Between Two Single-Mode Oscillating Bodies
TLDR
In this article, it is shown that for an axisymmetric system utilizing heave modes, it is possible to absorb an energy amounting to the incident wave power on a crest length which equals the wavelength divided by 2π, even though the power take-off is applied to the relative motion only.Abstract:
Wave-energy converters (WECs) need a reaction source against which the wave forces can react. As with shore-based WECs, sometimes also floating WECs react against a fixed point on the seabed. Alternatively, for a floating WEC, force reaction may be obtained by utilizing the relative motion between two bodies. A load force for energy conversion is assumed to be applied only to this relative motion. It is assumed that either body oscillates in one mode only (mostly, the heave mode is considered here). The system, if assumed to be linear, is proved to be phenomenologically equivalent to a one-mode, one-body system, for which the wave excitation force equals the force which is necessary to apply between the two bodies in order to ensure that they are oscillating with zero relative motion. It is discussed how this equivalent excitation force and also the intrinsic mechanical impedance of the equivalent system depend on the mechanical impedances for the two separate bodies, including the radiation impedance matrix (which combines radiation resistances and added masses). The equivalent system is applied for discussing optimum performance for maximizing the absorbed wave energy. It is shown that, for an axisymmetric system utilizing heave modes, it is possible to absorb an energy amounting to the incident wave power on a crest length which equals the wavelength divided by 2π, even though the power take-off is applied to the relative motion only. Moreover, it is shown that it is possible to obtain an equivalent excitation force which exceeds the wave excitation force on either body.read more
Citations
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Journal ArticleDOI
Wave energy utilization: A review of the technologies
TL;DR: In this article, the development of wave energy utilization since the 1970s is discussed, with a focus on the characterization of the wave energy resource; theoretical background, with especial relevance to hydrodynamics of wave absorption and control; how a large range of devices kept being proposed and studied, and how such devices can be organized into classes; the conception, design, model-testing, construction and deployment into real sea of prototypes.
Journal ArticleDOI
Ocean waves and oscillating systems : linear interactions including wave-energy extraction
TL;DR: In this paper, the authors describe the interaction between oscillations and waves, and describe the absorption of wave energy by oscillating bodies by wave-energy absorption by oscillated bodies, as well as wave interactions with oscillating water columns.
Journal ArticleDOI
Energy-Maximizing Control of Wave-Energy Converters: The Development of Control System Technology to Optimize Their Operation
TL;DR: In this paper, a wave energy has been shown to have some favorable variability properties (a perennial issue with many renewables, especially wind), especially when combined with wind energy, and wave energy can be used to fulfill future increasing energy needs.
Journal ArticleDOI
A Comparison of Selected Strategies for Adaptive Control of Wave Energy Converters
TL;DR: In this article, the authors focus on two aspects of systems for wave energy conversion: how to model such systems, and how to control their motion, which is crucial for the primary power conversion.
Journal ArticleDOI
A Simple and Effective Real-Time Controller for Wave Energy Converters
Francesco Fusco,John V. Ringwood +1 more
TL;DR: In this paper, a real-time control of oscillating wave energy converters (WECs) is proposed based on a nonstationary, harmonic approximation of the wave excitation force.
References
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Journal ArticleDOI
Surface wave interactions with systems of oscillating bodies and pressure distributions
Johannes Falnes,P. McIver +1 more
TL;DR: In this paper, the radiation coupling between all oscillators is represented by a partitioned matrix composed of the radiation admittance matrix for the pressure distributions, the radiation impedance matrix for oscillating bodies, and a radiation coupling matrix between the bodies and the pressure distribution.
Journal ArticleDOI
On non-causal impulse response functions related to propagating water waves
TL;DR: In this paper, the authors investigated the non-causality of two impulse response functions, one of which relates the excitation force on an immersed body to the incident wave elevation at the body's reference position, while the other relates the event wave elevations at two different positions along the line of wave propagation, in spite of the fact wave propagation is a causal process.
Journal ArticleDOI
Maximum wave-power absorption under motion constraints
TL;DR: In this article, an expression for the maximum mean power that can be absorbed by a system of oscillating bodies in waves under a global constraint on their motions is derived, and the particular case of a single half-immersed sphere is used to show how the 'point absorber' result predicting capture widths in excess of unity must be modified.
Book ChapterDOI
Heaving Point Absorbers Reacting against an Internal Mass
M. J. French,R. Bracewell +1 more
TL;DR: In this paper, a design study of a wave energy converter in the form of a heaving buoy reacting against an internal moving mass was made, where phase control was obtained by modulating the stiffness of the spring governing the moving mass.
Journal ArticleDOI
Added mass and damping of a sphere section in heave
D. V. Evans,P. McIver +1 more
TL;DR: In this article, the wave-induced forces on the outer rigid surface and the outer spherical surface due to independent oscillations of either are determined semi-analytically using a simple extension of the method of Havelock, recently simplified and generalised by Hulme, 3 for the complete half-immersed sphere.