scholarly journals Comparison of Numerical Methods for Modeling the Wave Field Effects Generated by Individual Wave Energy Converters and Multiple Converter Wave Farms

2020 ◽  
Vol 8 (3) ◽  
pp. 168 ◽  
Author(s):  
J. Cameron McNatt ◽  
Aaron Porter ◽  
Kelley Ruehl
Keyword(s):  
Wave Field ◽  
Wave Energy ◽  
Numerical Study ◽  
Near Field ◽  
Linear Wave ◽  
Power Curve ◽  
Field Effects ◽  
Wave Energy Converters ◽  
Individual Wave ◽  
Energy Converters

This numerical study compares the wave field generated by the spectral wave action balance code, SNL-SWAN, to the linear-wave boundary-element method (BEM) code, WAMIT. The objective of this study is to assess the performance of SNL-SWAN for modeling wave field effects produced by individual wave energy converters (WECs) and wave farms comprising multiple WECs by comparing results from SNL-SWAN with those produced by the BEM code WAMIT. BEM codes better model the physics of wave-body interactions and thus simulate a more accurate near-field wave field than spectral codes. In SNL-SWAN, the wave field’s energy extraction is modeled parametrically based on the WEC’s power curve. The comparison between SNL-SWAN and WAMIT is made over a range of incident wave conditions, including short-, medium-, and long-wavelength waves with various amounts of directional spreading, and for three WEC archetypes: a point absorber (PA), a pitching flap (PF) terminator, and a hinged raft (HR) attenuator. Individual WECs and wave farms of five WECs in various configuration were studied with qualitative comparisons made of wave height and spectra at specific locations, and quantitative comparisons of the wave fields over circular arcs around the WECs as a function of radial distance. Results from this numerical study demonstrate that in the near-field, the difference between SNL-SWAN and WAMIT is relatively large (between 20% and 50%), but in the far-field from the array the differences are minimal (between 1% and 5%). The resultant wave field generated by the two different numerical approaches is highly dependent on parameters such as: directional wave spreading, wave reflection or scattering, and the WEC’s power curve.

scholarly journals Excitation Forces Estimation for Non-linear Wave Energy Converters: A Neural Network Approach

2020 ◽  
Vol 53 (2) ◽  
pp. 12334-12339
Author(s):  
M. Bonfanti ◽  
F. Carapellese ◽  
S.A. Sirigu ◽  
G. Bracco ◽  
G. Mattiazzo
Keyword(s):  
Neural Network ◽  
Wave Energy ◽  
Linear Wave ◽  
Network Approach ◽  
Neural Network Approach ◽  
Wave Energy Converters ◽  
Non Linear ◽  
Energy Converters

The cylindrical wave field of wave energy converters

2013 ◽  
Vol 3-4 ◽  
pp. e26-e39 ◽  
Author(s):  
J. Cameron McNatt ◽  
Vengatesan Venugopal ◽  
David Forehand
Keyword(s):  
Wave Field ◽  
Wave Energy ◽  
Cylindrical Wave ◽  
Wave Energy Converters ◽  
Energy Converters

Emulation and Control Methods for Direct Drive Linear Wave Energy Converters

2013 ◽  
Vol 9 (2) ◽  
pp. 790-798 ◽  
Author(s):  
Zanxiang Nie ◽  
Xi Xiao ◽  
Richard McMahon ◽  
Peter Clifton ◽  
Yunxiang Wu ◽  
...  
Keyword(s):  
Wave Energy ◽  
Linear Wave ◽  
Control Methods ◽  
Direct Drive ◽  
Wave Energy Converters ◽  
And Control ◽  
Energy Converters

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

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.

scholarly journals Irregular Wave Validation of a Coupling Methodology for Numerical Modelling of Near and Far Field Effects of Wave Energy Converter Arrays

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 538 ◽  
Author(s):  
Gael Fernández ◽  
Vasiliki Stratigaki ◽  
Peter Troch
Keyword(s):  
Experimental Data ◽  
Wave Field ◽  
Wave Energy ◽  
Near Field ◽  
Coupled Model ◽  
Propagation Model ◽  
Irregular Waves ◽  
Far Field ◽  
Engineering Research ◽  
Field Effects

Between the Wave Energy Converters (WECs) of a farm, hydrodynamic interactions occur and have an impact on the surrounding wave field, both close to the WECs (“near field” effects) and at large distances from their location (“far field” effects). To simulate this “far field” impact in a fast and accurate way, a generic coupling methodology between hydrodynamic models has been developed by the Coastal Engineering Research Group of Ghent University in Belgium. This coupling methodology has been widely used for regular waves. However, it has not been developed yet for realistic irregular sea states. The objective of this paper is to present a validation of the novel coupling methodology for the test case of irregular waves, which is demonstrated here for coupling between the mild slope wave propagation model, MILDwave, and the ‘Boundary Element Method’-based wave–structure interaction solver, NEMOH. MILDwave is used to model WEC farm “far field” effects, while NEMOH is used to model “near field” effects. The results of the MILDwave-NEMOH coupled model are validated against numerical results from NEMOH, and against the WECwakes experimental data for a single WEC, and for WEC arrays of five and nine WECs. Root Mean Square Error (RMSE) between disturbance coefficient (Kd) values in the entire numerical domain ( R M S E K d , D ) are used for evaluating the performed validation. The R M S E K d , D between results from the MILDwave-NEMOH coupled model and NEMOH is lower than 2.0% for the performed test cases, and between the MILDwave-NEMOH coupled model and the WECwakes experimental data R M S E K d , D remains below 10%. Consequently, the efficiency is demonstrated of the coupling methodology validated here which is used to simulate WEC farm impact on the wave field under the action of irregular waves.

scholarly journals Designing and Testing Composite Energy Storage Systems for Regulating the Outputs of Linear Wave Energy Converters

Energies ◽  
2017 ◽  
Vol 10 (1) ◽  
pp. 114 ◽  
Author(s):  
Zanxiang Nie ◽  
Xi Xiao ◽  
Pritesh Hiralal ◽  
Xuanrui Huang ◽  
Richard McMahon ◽  
...  
Keyword(s):  
Energy Storage ◽  
Wave Energy ◽  
Storage Systems ◽  
Linear Wave ◽  
Energy Storage Systems ◽  
Wave Energy Converters ◽  
Composite Energy ◽  
Energy Converters

scholarly journals Extending Complex Conjugate Control to Nonlinear Wave Energy Converters

2020 ◽  
Vol 8 (2) ◽  
pp. 84
Author(s):  
David G. Wilson ◽  
Rush D. Robinett ◽  
Giorgio Bacelli ◽  
Ossama Abdelkhalik ◽  
Ryan G. Coe
Keyword(s):  
Energy Harvesting ◽  
Limit Cycle ◽  
Wave Energy ◽  
Limit Cycles ◽  
Reactive Power ◽  
Complex Conjugate ◽  
Linear Wave ◽  
Wave Energy Converters ◽  
Linear Limit ◽  
Energy Converters

This paper extends the concept of Complex Conjugate Control (CCC) of linear wave energy converters (WECs) to nonlinear WECs by designing optimal limit cycles with Hamiltonian Surface Shaping and Power Flow Control (HSSPFC). It will be shown that CCC for a regular wave is equivalent to a power factor of one in electrical power networks, equivalent to mechanical resonance in a mass-spring-damper (MSD) system, and equivalent to a linear limit cycle constrained to a Hamiltonian surface defined in HSSPFC. Specifically, the optimal linear limit cycle is defined as a second-order center in the phase plane projection of the constant energy orbit across the Hamiltonian surface. This concept of CCC described by a linear limit cycle constrained to a Hamiltonian surface will be extended to nonlinear limit cycles constrained to a Hamiltonian surface for maximum energy harvesting by the nonlinear WEC. The case studies presented confirm increased energy harvesting which utilizes nonlinear geometry realization for reactive power generation.

scholarly journals A Coupled Methodology for Wave-Body Interactions at the Scale of a Farm of Wave Energy Converters Including Irregular Bathymetry

2014 ◽  
Author(s):  
François Charrayre ◽  
Christophe Peyrard ◽  
Michel Benoit ◽  
Aurélien Babarit
Keyword(s):  
Wave Energy ◽  
Diffraction Problem ◽  
Wave Theory ◽  
Field Approximation ◽  
Coupling Scheme ◽  
Linear Wave ◽  
Wave Energy Converters ◽  
Mild Slope Equation ◽  
Wave Farm ◽  
Energy Converters

Knowledge of the wave perturbation caused by an array of Wave Energy Converters (WEC) is of great concern, in particular for estimating the interaction effects between the various WECs and determining the modification of the wave field at the scale of the array, as well as possible influence on the hydrodynamic conditions in the surroundings. A better knowledge of these interactions will also allow a more efficient layout for future WEC farms. The present work focuses on the interactions of waves with several WECs in an array. Within linear wave theory and in frequency domain, we propose a methodology based on the use of a BEM (Boundary Element Method) model (namely Aquaplus) to solve the radiation-diffraction problem locally around each WEC, and to combine it with a model based on the mild slope equation at the scale of the array. The latter model (ARTEMIS software) solves the Berkhoff’s equation in 2DH domains (2 dimensional code with a z-dependence), considering irregular bathymetries. In fact, the Kochin function (a far field approximation) is used to propagate the perturbations computed by Aquaplus into Artemis, which is well adapted for a circular wave representing the perturbation of an oscillating body. This approximation implies that the method is only suitable for well separated devices. A main advantage of this coupling technique is that Artemis can deal with variable bathymetry. It is important when the wave farm is in shallow water or in nearshore areas. The methodology used for coupling the two models, with the underlying assumptions is detailed first. Validations test-cases are then carried out with simple bodies (namely heaving vertical cylinders) to assess the accuracy and efficiency of the coupling scheme. These tests also allow to analyze and to quantify the magnitude of the interactions between the WECs inside the array.

Sign in / Sign up

Export Citation Format

Share Document