The Principle of a Three-DOF Mechanism for Wave Energy Absorption

2016 ◽  
Author(s):  
Weixing Chen ◽  
Xiangdun Meng ◽  
Feng Gao
Keyword(s):  
Wave Energy ◽  
Power Output ◽  
Wave Power ◽  
Spherical Joint ◽  
Hydraulic Power ◽  
Wave Energy Converters ◽  
Major Class ◽  
Absorption Performance ◽  
Heave Motion ◽  
Four Bar Linkage

As we all know, oceans have great wave power, and many types of wave energy converters (WECs) have been invented so far. Oscillating body systems are a major class of WECs which almost only have one degree of freedom (DOF). This paper presents a three-DOF mechanism which can extract the wave power from any wave directions. The three-DOF mechanism mainly consists of a four-bar linkage and a spherical joint, which are used to capture the heave motion and the pitch and roll motions of the oscillating body respectively. The power conversion principle of the WEC is proposed and the kinematics of the mechanism is derived. Hydraulic power take-off (PTO) systems are used, which are simplified as constant torques in this study. In the end, the power absorption performance of the WEC is presented based on the system dynamics. The results show that the rated power output of the WEC is 4.3MW, and the power output of the WEC is dependent on the wave directions.

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.

scholarly journals Revisiting Theoretical Limits for One-Degree-of-Freedom Wave Energy Converters

2020 ◽  
pp. 1-11
Author(s):  
Nathan Tom
Keyword(s):  
Power Generation ◽  
Wave Energy ◽  
Degree Of Freedom ◽  
Upper And Lower Bounds ◽  
Complex Conjugate ◽  
Hydrodynamic Coefficients ◽  
Damping Coefficients ◽  
Wave Energy Converters ◽  
Heave Motion ◽  
Energy Converters

Abstract This work revisits the theoretical limits of one-degree-of-freedom wave energy converters (WECs). This paper considers the floating sphere used in the OES Task 10 WEC modeling and verification effort for analysis. Analytical equations are derived to determine bounds on displacement amplitude, time-averaged power (TAP), and power-take-off (PTO) force. A unique result found shows that the TAP absorbed by a WEC can be defined solely by the inertial properties and radiation hydrodynamic coefficients. In addition, a unique expression for the PTO force was derived that provides upper and lower bounds when resistive control is used to maximize power generation. For complex conjugate control, this same expression only provides a lower bound, as there is theoretically no upper bound. These bounds assist in comparing the performance of the floating sphere if it were to extract energy using surge or heave motion. The analysis shows because of differences in hydrodynamic coefficients for each oscillating mode, there are different frequency ranges that provide better power capture efficiency. The influence of a motion constraint on TAP while utilizing a nonideal power take-off is examined and found to reduce the losses associated with bidirectional energy flow. The expression to calculate TAP with a nonideal PTO is modified by the mechanical-to-electrical efficiency and the ratio of the PTO spring and damping coefficients. The PTO spring and damping coefficients were separated in the expression, allowing for limits to be set on the PTO coefficients to ensure net power generation.

scholarly journals Wave Power Assessment in the Middle Part of the Southern Coast of Java Island

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2633
Author(s):  
Addy Wahyudie ◽  
Tri Bagus Susilo ◽  
Fatima Alaryani ◽  
Cuk Supriyadi Ali Nandar ◽  
Mohammed Abdi Jama ◽  
...  
Keyword(s):  
Spatial Analysis ◽  
Wave Energy ◽  
Significant Wave Height ◽  
Middle Part ◽  
Wave Power ◽  
Southern Coast ◽  
Power Intensity ◽  
Wave Energy Converters ◽  
Potential Area ◽  
Suitable Location

An assessment of the wave power at the southern coast of the middle part of Java Island (Indonesia) was conducted based on a 15-year hindcast spectral wave model using the MIKE 21 Spectral Wave software. The model was forced with wind data with a 0.125° spatial interval and hourly time resolution. The obtained model was validated with field data collected from a buoy station that provided a set of significant wave height data with an hourly data interval for the whole month of June 2014. The validation showed that the obtained model matched the observed data with a minor average error. A spatial analysis was conducted in order to find the most suitable location for installing wave energy converters while taking into consideration the potential area demand, the wave power intensity, and the distance from the shore. Moreover, spatial analysis is conducted in order to find a suitable location to install wave energy converters, with consideration to potential area demand, wave power intensity, and distance from the shore. The best prospective location reached 30 kW/m of mean wave power intensity, 2.04 m of mean significant wave height, 8.9 s of mean wave period, 150 m of distance from the shoreline.

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.

scholarly journals Influence of Time and Frequency Domain Wave Forcing on the Power Estimation of a Wave Energy Converter Array

2020 ◽  
Vol 8 (3) ◽  
pp. 171
Author(s):  
Fadia Ticona Rollano ◽  
Thanh Toan Tran ◽  
Yi-Hsiang Yu ◽  
Gabriel García-Medina ◽  
Zhaoqing Yang
Keyword(s):  
Power Systems ◽  
Wave Energy ◽  
Time Domain ◽  
Power Output ◽  
Wave Model ◽  
Phase Information ◽  
Wave Forcing ◽  
Marine Renewable Energy ◽  
Wave Energy Converters ◽  
Averaged Model

Industry-specific tools for analyzing and optimizing the design of wave energy converters (WECs) and associated power systems are essential to advancing marine renewable energy. This study aims to quantify the influence of phase information on the device power output of a virtual WEC array. We run the phase-resolving wave model FUNWAVE-TVD (Total Variation Diminishing) to generate directional waves at the PacWave South site offshore from Newport, Oregon, where future WECs are expected to be installed for testing. The two broad cases presented correspond to mean wave climates during warm months (March–August) and cold months (September–February). FUNWAVE-TVD time series of sea-surface elevation are then used in WEC-Sim, a time domain numerical model, to simulate the hydrodynamic response of each device in the array and estimate their power output. For comparison, WEC-Sim is also run with wave energy spectra calculated from the FUNWAVE-TVD simulations, which do not retain phase information, and with wave spectra computed using the phase-averaged model Simulating WAves Nearshore (SWAN). The use of spectral data in WEC-Sim requires a conversion from frequency to time domain by means of random superposition of wave components, which are not necessarily consistent because of the linear assumption implicit in this method. Thus, power response is characterized by multiple realizations of the wave climates.

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.

Basic Characteristics of the Primary Conversion of an OWC Type WEC Installed on a Wave Dissipating Double-Caisson

2018 ◽  
Author(s):  
Tomoki Ikoma ◽  
Koichi Masuda ◽  
Hiroaki Eto ◽  
Shogo Shibuya
Keyword(s):  
Wave Height ◽  
Basic Property ◽  
Wave Energy ◽  
Wave Power ◽  
Oscillating Water Column ◽  
Type Wave ◽  
Wave Energy Converters ◽  
The World ◽  
Fixed Type ◽  
Basic Characteristics

Several types of oscillating water column (OWC) type wave energy converters (WECs) are researched and developed in the world. They are floating types and fixed types. In case of a fixed type, wave dissipating caissons could be replaced to WECs of an OWC type. On OWC types, installation of the projecting-walls (PWs) is useful in order to improve PTO performance. In this study, it was considered that a double dissipating caisson was used as an OWC type WEC with PWs. A front caisson of the double caisson seems the area surrounded by PWs and a back caisson can be seen as an OWC. The paper studied basic property of the primary conversion from wave power to power of air from model tests in a wave tank. As a result, wave height strongly effects on behaviours of OWC motion as well as air pressure. Finally, the primary conversion was affected by wave height. Besides, the concept of use of a double caisson was useful from the primary conversion over 80 % evaluated using test data.

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.

Study on the Layout of Water-Filled Raft WEC in Wave Farm

2012 ◽  
Vol 253-255 ◽  
pp. 670-673
Author(s):  
Zhi Gang Bai ◽  
Lian Bo Shi
Keyword(s):  
Wave Energy ◽  
Power Output ◽  
Electricity Generation ◽  
Design Environment ◽  
Engineering Software ◽  
Wave Energy Converters ◽  
The World ◽  
New Type ◽  
Type Water ◽  
Wave Farm

Wave energy is recognized as an important pollution-free source of power generation in the world. So in last decades wide variety of wave energy converters (WEC) has been developed, meanwhile, more economical and reliable technologies were also under process. It is very vital to decide about the location of the WECs in a wave farm, which can increase the electricity generation [1]. To get the optimum power output, it is necessary to evaluate the layout of WECs by computer simulations, such as SWAN, MIKE21, SWASH, etc [2]. Among them, MIKE21 is a professional modeling and simulation engineering software, and is well known as a tool that provides a design environment for engineering, coastal management and planning applications. So, in this paper, MIKE21 BW was introduced briefly and applied to simulate and calculate the wave parameters of the Chengshantou wave farm, then, the layout of a new-type (Water-filled raft) WECs in the Chengshantou wave farm which can generate higher possible power output was investigated and the optimum scheme was achieved finally.

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