scholarly journals Wave power extraction by multiple wave energy converters arrayed in a water channel resonator

2021 ◽  
Vol 13 ◽  
pp. 178-186
Author(s):  
Jeongrok Kim ◽  
Il-Hyoung Cho
Keyword(s):  
Wave Energy ◽  
Water Channel ◽  
Wave Power ◽  
Multiple Wave ◽  
Power Extraction ◽  
Wave Energy Converters ◽  
Energy Converters

scholarly journals Hardware-in-the-Loop Validation of Model Predictive Control of a Discrete Fluid Power Power Take-Off System for Wave Energy Converters

Energies ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3668
Author(s):  
Anders H. Hansen ◽  
Magnus F. Asmussen ◽  
Michael M. Bech
Keyword(s):  
Model Predictive Control ◽  
Predictive Control ◽  
Wave Energy ◽  
Fluid Power ◽  
Wave Power ◽  
Reactive Control ◽  
Power Extraction ◽  
Wave Energy Converters ◽  
Extraction Algorithm ◽  
Energy Converters

Model predictive control based wave power extraction algorithms have been developed and found promising for wave energy converters. Although mostly proven by simulation studies, model predictive control based algorithms have shown to outperform classical wave power extraction algorithms such as linear damping and reactive control. Prediction models and objective functions have, however, often been simplified a lot by for example, excluding power take-off system losses. Furthermore, discrete fluid power forces systems has never been validated experimentally in published research. In this paper a model predictive control based wave power extraction algorithm is designed for a discrete fluid power power take-off system. The loss models included in the objective function are based on physical models of the losses associated with discrete force shifts and throttling. The developed wave power extraction algorithm directly includes the quantized force output and the losses models of the discrete fluid power system. The experimental validation of the wave power extraction algorithm developed in the paper shown an increase of 14.6% in yearly harvested energy when compared to a reactive control algorithm.

Heave Motion Performance of Multiple Wave Energy Converters Arrayed in a Water Channel Resonator

2020 ◽  
Author(s):  
Jeongrok Kim ◽  
Il-Hyoung Cho
Keyword(s):  
Wave Energy ◽  
Water Channel ◽  
Standing Waves ◽  
Low Density ◽  
Energy Extraction ◽  
Multiple Wave ◽  
Wave Energy Converters ◽  
Internal Fluid ◽  
Heave Motion ◽  
Energy Converters

Abstract The performance of multiple wave energy converters (WECs) arranged in a Y-shaped water channel resonator (WCR) for amplifying the wave energy with low density was investigated. The WCR consists of a long channel and waveguide installed at the entrance. If the period of the incident wave coincides with the natural period of the fluid in the WCR, then resonance occurs, and the internal fluid is greatly amplified in the form of standing waves. The WECs were positioned at the anti-nodes of standing waves formed in the WCR to maximize energy extraction. We dealt with the heave motion, time-averaged power, and capture width ratio (CWR) of WECs, which are composed of a heaving cylinder and a linear generator. For this purpose, we used the boundary element method and WAMIT commercial code. In parallel, systematic model tests were conducted at the 2D wave tank in Jeju National University to validate the numerical solution. Both results were in good agreement. WECs with a short draft are efficient in energy extraction compared with WECs with a long draft. Numerical and experimental results reveal that the WECs arranged in a WCR have higher efficiency over a wide band of periods than a single WEC without a WCR. Therefore, the wave energy with low density can be amplified by the resonance of the internal fluid in the WCR.

scholarly journals Near Trapping Effect on Wave-Power Extraction by Linear Periodic Arrays

2019 ◽  
Vol 12 (1) ◽  
pp. 29
Author(s):  
Dezhi Ning ◽  
Zechen He ◽  
Ying Gou ◽  
Malin Göteman
Keyword(s):  
Incident Wave ◽  
Wave Energy ◽  
Hydrodynamic Interaction ◽  
Wave Power ◽  
Wave Direction ◽  
Power Extraction ◽  
Periodic Arrays ◽  
Wave Energy Converters ◽  
Incident Wave Direction ◽  
Energy Converters

Near trapping is a kind of strong hydrodynamic interaction phenomenon in a regular array under specific incident wave conditions, which causes the excitation force on the structures in the array to change suddenly. In this paper, based on linear potential flow theory, the effects of near trapping on the hydrodynamic interaction and wave-power extraction characteristics of linear periodic arrays composed of the oscillating float type wave energy converters are studied by using the higher-order boundary element method in a frequency domain. The parameters considered include the separation spacing, number of devices, and incident wave direction. It is found that the near trapping significantly reduces the overall wave-power extraction, especially for the cases with a large number of devices, and changes the trend of the power distribution. The occurrence of the near trapping phenomenon depends on the ratio of the separation spacing to the wavelength and the incident wave direction. The results highlight the effective layout of linear arrays under the influence of near trapping, which not only ensures the total production power, but also reduces the power difference among wave energy converters.

Peakedness of Wave Systems Observed on the French Wave Energy Test Site (SEM-REV) Using a Spectral Partitioning Algorithm

2013 ◽  
Author(s):  
Jean-Baptiste Saulnier ◽  
Izan Le Crom
Keyword(s):  
Wave Energy ◽  
Test Site ◽  
Extreme Conditions ◽  
Multiple Wave ◽  
Wave Energy Converters ◽  
Marine Energy ◽  
Partitioning Algorithm ◽  
Spectral Partitioning ◽  
The Individual ◽  
Energy Converters

Located off the Guérande peninsula, SEM-REV is the French maritime facility dedicated to the testing of wave energy converters and related components. Lead by Ecole Centrale de Nantes through the LHEEA laboratory, its aim is to promote research alongside the development of new offshore technologies. To this end, the 1km2, grid-connected zone is equipped with a comprehensive instruments network sensing met-ocean processes and especially waves, with two identical directional Waverider buoys deployed on the site since 2009. For the design of moored floating structures and, a fortiori, floating marine energy converters, the knowledge of the main wave resource — for regular operation — but also extreme conditions — for moorings and device survivability — has to be as precise as possible. Also, the consideration of the multiple wave systems (swell, wind sea) making up the sea state is a key asset for the support of developers before and during the testing phase. To this end, a spectral partitioning algorithm has been implemented which enables the individual characterisation of wave systems, in particular that of their spectral peakedness which is especially addressed in this work. Peakedness has been shown to be strongly related to the groupiness of large waves and is defined here as the standard JONSWAP’s peak enhancement factor γ. Statistics related to this quantity are derived from the measurement network, with a particular focus on the extreme conditions reported on SEM-REV (Joachim storm).

Performance assessments of the fully submerged sphere and cylinder point absorber wave energy converters

2019 ◽  
Vol 33 (13) ◽  
pp. 1950168 ◽  
Author(s):  
Qianlong Xu ◽  
Ye Li ◽  
Yingkai Xia ◽  
Weixing Chen ◽  
Feng Gao
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Interaction Analysis ◽  
Wave Power ◽  
Viscous Damping ◽  
Power Performance ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Submerged Sphere ◽  
Energy Converters

Fully submerged sphere and cylinder point absorber (PA), wave energy converters (WECs) are analyzed numerically based on linearized potential flow theory. A boundary element method (BEM) (a radiation–diffraction panel program for wave-body interactions) is used for the basic wave-structure interaction analysis. In the present numerical model, the viscous damping is modeled by an equivalent linearized damping which extracts the same amount of wave energy over one cycle as the conventional quadratic damping term. The wave power capture width in each case is predicted. Comparisons are also made between the sphere and cylinder PAs which have identical geometrical scales and submerged depths. The results show that: (i) viscous damping has a greater influence on wave power performance of the cylinder PA than that of the sphere PA; (ii) the increasing wave height reduces wave power performance of PAs; (iii) the cylinder PA has a better wave power performance compared to the sphere PA in larger wave height scenarios, which indicates that fully submerged cylinder PA is a preferable prototype of WEC.

Introducing Wave Regeneration by Wind in a Mild-Slope Wave Propagation Model MILDwave to Investigate the Wake Effects in the Lee of a Farm of Wave Energy Converters

2011 ◽  
Author(s):  
Vasiliki Stratigaki ◽  
Peter Troch ◽  
Leen Baelus ◽  
Yannick Keppens
Keyword(s):  
Wave Propagation ◽  
Wave Energy ◽  
Propagation Model ◽  
Wave Power ◽  
Single Wave ◽  
Wave Energy Converters ◽  
Wake Effects ◽  
Wave Regeneration ◽  
Wave Propagation Model ◽  
Energy Converters

The increasing energy demand, the need to reduce greenhouse gas emissions and the shrinking reserves of fossil fuels have all enhanced the interest in sustainable and renewable energy sources, including wave energy. Many concepts for wave power conversion have been invented. In order to extract a considerable amount of wave power, single Wave Energy Converters (abbreviated as WECs) will have to be arranged in arrays or ‘farms’ using a particular geometrical layout, comprising large numbers of devices. As a result of the interaction between the WECs within a farm, the overall power absorption is affected. In general, the incident waves are partly reflected, transmitted and absorbed by a single WEC. Also, the wave height behind a large farm of WECs is reduced and this reduction may influence neighbouring farms, other users in the sea or even the coastline (wake effects of a WEC farm). The numerical wave propagation model MILDwave has been recently used to study wake effects and energy absorption of farms of WECs, though without taking into account wave regeneration by wind in the lee of the WEC-farm which can be significant in large distances downwave the WECs. In this paper, the implementation of wave growth due to wind in the hyperbolic mild-slope equations of the wave propagation model, MILDwave is described. Several formulations for the energy input from wind found in literature are considered and implemented. The performance of these formulations in MILDwave is investigated and validated. The modified model MILDwave is then applied for the investigation of the influence of the wind on the wakes in the lee of a farm of wave energy converters.

scholarly journals Grid Connection of Wave Power Farm Using an N-Level Cascaded H-Bridge Multilevel Inverter

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Rickard Ekström ◽  
Mats Leijon
Keyword(s):  
Wave Energy ◽  
Power Sharing ◽  
Multilevel Inverter ◽  
Wave Power ◽  
Good Correspondence ◽  
Large Wave ◽  
N Level ◽  
Wave Energy Converters ◽  
Grid Connection ◽  
Energy Converters

An N-level cascaded H-bridge multilevel inverter is proposed for grid connection of large wave power farms. The point-absorber wave energy converters are individually rectified and used as isolated DC-sources. The variable power characteristics of the wave energy converters are discussed, and a method of mitigating this issue is demonstrated. The complete power control system is given in detail and has been experimentally verified for a single-phase setup of the 9-level inverter. Theoretical expressions of the power sharing between multilevel cells are derived and show good correspondence with the experimental results.

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