Oceans of energy? The non-linear trajectory of the emerging wave energy technology

This paper presents the findings from using several commercial computational fluid dynamics codes in a joint numerical and experimental project to simulate WRASPA, a new wave energy converter (WEC) device. A series of fully 3D non-linear simulations of WRASPA are presented. Three commercial codes STAR-CCM, CFX and FLOW-3D are considered for simulating the WRASPA device and final results are presented based on the use of Flow-3D. Results are validated by comparison to experimental data obtained from small scale tank tests undertaken at Lancaster University (LU). The primary aim of the project is to use numerical simulation to optimize the collector geometry for power production over a range of likely wave climates. A secondary aim is to evaluate the ability of commercial codes to simulate rigid body motion in linear and non-linear wave climates in order to choose the optimal code with respect to compute speed and ease of problem setup. Issues relating to the ability of a code in terms of numerical dissipation of waves, wave absorption, wave breaking, grid generation and moving bodies will all be discussed. The findings of this paper serve as a basis for an informed choice of commercial package for such simulations. However the capability of these commercial codes is increasing with every new release.

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Genetic Optimization of Shape and Control of Non-Linear Wave Energy Converters

Volume 9: Ocean Renewable Energy ◽

10.1115/omae2020-19156 ◽

2020 ◽

Author(s):

Jiajun Song ◽

Ossama Abdelkhalik ◽

Shangyan Zou

Keyword(s):

Wave Energy ◽

Time Domain ◽

Optimization Approach ◽

Linear Wave ◽

Variable Size ◽

Wave Energy Converters ◽

Hydrostatic Force ◽

Non Linear ◽

The Time Domain ◽

Energy Converters

Abstract This paper presents an optimization approach to design ax-isymmetric wave energy converters (WECs) based on a nonlinear hydrodynamic model. This paper shows optimal nonlinear shapes of buoy can be generated by combing basic shapes in an optimal sense. The time domain non-linear Froude-Krylov force can be computed for a complex buoy shape, by adopting analytical formulas of its basic shape components. The time domain Forude-Krylov force is decomposed into its dynamic and static components, and then contribute to the calculation of the excitation force and the hydrostatic force. A non-linear control is assumed in the form of the combination of linear and nonlinear damping terms. A variable size genetic algorithm (GA) optimization tool is developed to search for the optimal buoy shape along with the optimal control coefficients simultaneously. Chromosome of the GA tool is designed to improve computational efficiency and to leverage variable size genes to search for the optimal non-linear buoy shape. Different criteria of wave energy conversion can be implemented by the variable size GA tool. Simulation results presented in this paper show that it is possible to find non-linear buoy shapes and non-linear controllers that take advantage of non-linear hydrodynamics to improve energy harvesting efficiency with out adding reactive terms to the system.

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Atmospheric oscillations in late-type stars - I. Non-linear response to excitation by acoustic wave energy spectra

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2011.20285.x ◽

2012 ◽

pp. no-no ◽

Cited By ~ 6

Author(s):

Diaa E. Fawzy ◽

Z. E. Musielak

Keyword(s):

Acoustic Wave ◽

Wave Energy ◽

Linear Response ◽

Energy Spectra ◽

Late Type ◽

Non Linear

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Non-linear numerical modeling and experimental testing of a point absorber wave energy converter

Ocean Engineering ◽

10.1016/j.oceaneng.2013.12.009 ◽

2014 ◽

Vol 78 ◽

pp. 11-21 ◽

Cited By ~ 63

Author(s):

A.S. Zurkinden ◽

F. Ferri ◽

S. Beatty ◽

J.P. Kofoed ◽

M.M. Kramer

Keyword(s):

Numerical Modeling ◽

Wave Energy ◽

Experimental Testing ◽

Wave Energy Converter ◽

Energy Converter ◽

Point Absorber ◽

Non Linear

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Control of a Permanent Magnet Synchronous Motor Using a Second-Order Non-Linear Trajectory Smoother

Proceedings of the Institution of Mechanical Engineers Part I Journal of Systems and Control Engineering ◽

10.1243/095965105x33626 ◽

2005 ◽

Vol 219 (8) ◽

pp. 565-575 ◽

Cited By ~ 4

Author(s):

K M Tsang ◽

J Wang

Keyword(s):

Permanent Magnet ◽

Permanent Magnet Synchronous Motor ◽

Experimental Studies ◽

Variable Structure ◽

Second Order ◽

Linear Trajectory ◽

System Parameters ◽

Variable Structure System ◽

Non Linear ◽

Load Conditions

A second-order non-linear discrete trajectory smoother is coupled with conventional control law for servo-control of permanent magnet synchronous motors (PMSMs). Conventional control relies on three closed loops with linear proportional-integral-derivative (PID) controllers and gives an undesirable performance under the mismatch. of system parameters and load conditions. To overcome this drawback, a discrete-time second-order non-linear trajectory smoother is applied for the control of a PMSM. The second-order non-linear trajectory smoother is a non-linear variable structure system (VSS) catering for smooth trajectory generation for a motion control system. The trajectory smoother guarantees robustness against a change of system parameters and load conditions. Simulation and experimental studies are included to demonstrate the effectiveness of the proposed control scheme.

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