scholarly journals Resonant behaviour of an oscillating wave energy converter in a channel

2012 ◽  
Vol 701 ◽  
pp. 482-510 ◽  
Author(s):  
Emiliano Renzi ◽  
F. Dias
Keyword(s):  
Wave Energy ◽  
Velocity Potential ◽  
Wave Energy Converter ◽  
Maximum Efficiency ◽  
Hypersingular Integral Equation ◽  
Energy Converter ◽  
Theory Application ◽  
Incident Waves ◽  
Resonant Mechanism ◽  
Recent Laboratory

AbstractA mathematical model is developed to study the behaviour of an oscillating wave energy converter in a channel. During recent laboratory tests in a wave tank, peaks in the hydrodynamic actions on the converter occurred at certain frequencies of the incident waves. This resonant mechanism is known to be generated by the transverse sloshing modes of the channel. Here the influence of the channel sloshing modes on the performance of the device is further investigated. Within the framework of a linear inviscid potential-flow theory, application of Green’s theorem yields a hypersingular integral equation for the velocity potential in the fluid domain. The solution is found in terms of a fast-converging series of Chebyshev polynomials of the second kind. The physical behaviour of the system is then analysed, showing sensitivity of the resonant sloshing modes to the geometry of the device, which concurs in increasing the maximum efficiency. Analytical results are validated with available numerical and experimental data.

scholarly journals Analytical Study on an Oscillating Buoy Wave Energy Converter Integrated into a Fixed Box-Type Breakwater

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Xuanlie Zhao ◽  
Dezhi Ning ◽  
Chongwei Zhang ◽  
Yingyi Liu ◽  
Haigui Kang
Keyword(s):  
Wave Energy ◽  
Wave Energy Converter ◽  
Hydrodynamic Performance ◽  
Maximum Efficiency ◽  
Width Ratio ◽  
Geometrical Parameters ◽  
Linear Potential ◽  
Energy Converter ◽  
Transmission Coefficients ◽  
Incident Waves

An oscillating buoy wave energy converter (WEC) integrated to an existing box-type breakwater is introduced in this study. The buoy is installed on the existing breakwater and designed to be much smaller than the breakwater in scale, aiming to reduce the construction cost of the WEC. The oscillating buoy works as a heave-type WEC in front of the breakwater towards the incident waves. A power take-off (PTO) system is installed on the topside of the breakwater to harvest the kinetic energy (in heave mode) of the floating buoy. The hydrodynamic performance of this system is studied analytically based on linear potential-flow theory. Effects of the geometrical parameters on the reflection and transmission coefficients and the capture width ratio (CWR) of the system are investigated. Results show that the maximum efficiency of the energy extraction can reach 80% or even higher. Compared with the isolated box-type breakwater, the reflection coefficient can be effectively decreased by using this oscillating buoy WEC, with unchanged transmission coefficient. Thus, the possibility of capturing the wave energy with the oscillating buoy WEC integrated into breakwaters is shown.

A submerged cylinder wave energy converter

2013 ◽  
Vol 716 ◽  
pp. 566-596 ◽  
Author(s):  
S. Crowley ◽  
R. Porter ◽  
D. V. Evans
Keyword(s):  
Wave Energy ◽  
Three Dimensional ◽  
Wave Energy Converter ◽  
Wave Crest ◽  
Maximum Efficiency ◽  
Passive Component ◽  
Mooring System ◽  
Energy Converter ◽  
Rotation Rates ◽  
Sea Bed

AbstractA novel design concept for a wave energy converter (WEC) is presented and analysed. Its purpose is to balance the theoretical capacity for power absorption against engineering design issues which plague many existing WEC concepts. The WEC comprises a fully submerged buoyant circular cylinder tethered to the sea bed by a simple mooring system which permits coupled surge and roll motions of the cylinder. Inside the cylinder a mechanical system of pendulums rotate with power generated by the relative rotation rates of the pendulums and the cylinder. The attractive features of this design include: making use of the mooring system as a passive component of the power take off (PTO); using a submerged device to protect it from excessive forces associated with extreme wave conditions; locating the PTO within the device and using a PTO mechanism which does not need to be constrained; exploiting multiple resonances of the system to provide a broad-banded response. A mathematical model is developed which couples the hydrodynamic waves forces on the device with the internal pendulums under a linearized framework. For a cylinder spanning a wave tank (equivalent to a two-dimensional assumption) maximum theoretical power for this WEC device is limited to 50 % maximum efficiency. However, numerical results show that a systematically optimized system can generate theoretical efficiencies of more than 45 % over a 6 s range of wave period containing most of the energy in a typical energy spectrum. Furthermore, three-dimensional results for a cylinder of finite length provide evidence that a cylinder device twice the length of its diameter can produce more than its own length in the power of an equivalent incident wave crest.

Numerical Analysis of the Oscillating Water Column (OWC) Wave Energy Converter (WEC) Considering Different Incident Wave Height

2017 ◽  
Vol 370 ◽  
pp. 120-129
Author(s):  
Mateus das Neves Gomes ◽  
Eduardo Alves Amado ◽  
Elizaldo Domingues dos Santos ◽  
Liércio André Isoldi ◽  
Luiz Alberto Oliveira Rocha
Keyword(s):  
Water Column ◽  
Wave Height ◽  
Incident Wave ◽  
Wave Energy ◽  
Amplification Factor ◽  
Wave Energy Converter ◽  
Geometric Shape ◽  
Oscillating Water Column ◽  
Energy Converter ◽  
Incident Waves

The ocean wave energy conversion into electricity has been increasingly researched in the last years. There are several proposed converters, among them the Oscillating Water Column (OWC) device has been widely studied. The present paper presents a two-dimensional numerical investigation about the fluid dynamics behavior of an OWC Wave Energy Converter (WEC) into electrical energy. The main goal of this work was to numerically analyze the optimized geometric shape obtained in previous work under incident waves with different heights. To do so, the OWC geometric shape was kept constant while the incident wave height was varied. For the numerical solution it was used the Computational Fluid Dynamic (CFD) commercial code FLUENT®, based on the Finite Volume Method (FVM). The multiphasic Volume of Fluid (VOF) model was applied to tackle with the water-air interaction. The computational domain is represented by the OWC device coupled with the wave tank. This work allowed to check the influence of the incident wave height on the hydropneumatic power and the amplification factor of the OWC converter. It was possible to identify that the amplification factor increases as the wave period increases, thereby improving the OWC performance. It is worth to highlight that in the real phenomenon the incident waves on the OWC device have periods, lengths and height variables.

Experimental Assessment of the Performance of CECO Wave Energy Converter in Irregular Waves

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Claudio A. Rodríguez ◽  
Paulo Rosa-Santos ◽  
Francisco Taveira-Pinto
Keyword(s):  
Wave Energy ◽  
Transfer Functions ◽  
Wave Energy Converter ◽  
Irregular Waves ◽  
Energy Converter ◽  
Energy Harvesters ◽  
Point Absorber ◽  
Model Scale ◽  
Absorbed Power ◽  
Incident Waves

The performance assessment of a wave energy converter (WEC) is a key task. Depending on the layout of the WEC system and type of power take-off (PTO) mechanism, the determination of the absorbed power at model scale involves several challenges, particularly when the measurement of PTO forces is not available. In irregular waves, the task is even more difficult due to the random character of forces and motions. Recent studies carried out with kinetic energy harvesters (KEH) have proposed expressions for the estimation of the power based only on the measured motions. Assuming that the WEC behaves as a KEH at model scale, the expressions for power estimation of KEHs have been heuristically adapted to WECs. CECO, a floating-point absorber, has been used as case study. Experimental data from model tests in irregular waves are presented and analyzed. Spectral analyses have been applied to investigate the WEC responses in the frequency domain and to derive expressions to estimate the absorbed power in irregular waves. The experimental transfer functions of the WEC motions demonstrated that the PTO damping is significantly affected by the incident waves. Based on KEH approach's results, absorbed power and PTO damping coefficients have been estimated. A linear numerical potential model to compute transfer functions has been also implemented and calibrated based on the experimental results. The numerical results allowed the estimation of combined viscous and losses effects and showed that although the KEH approach underestimated the absorbed power, qualitatively reproduced the WEC performance in waves.

scholarly journals Hydrodynamic Investigation of a Dual-Cylindrical OWC Wave Energy Converter Integrated into a Fixed Caisson Breakwater

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 896 ◽  
Author(s):  
Chang Wan ◽  
Can Yang ◽  
Qinghe Fang ◽  
Zaijin You ◽  
Jing Geng ◽  
...  
Keyword(s):  
Energy Conversion ◽  
Analytical Model ◽  
Wave Energy ◽  
Velocity Potential ◽  
Wave Energy Converter ◽  
Published Data ◽  
Geometrical Parameters ◽  
Linear Potential ◽  
Energy Converter ◽  
Cylindrical Column

A fixed dual cylindrical oscillating water column (OWC) acting as a breakwater-type wave energy converter (WEC) is proposed to harvest the wave energy effectively for shallow offshore sites. An analytical model is developed to investigate the hydrodynamic characteristics and the energy capture capacity of the cylindrical OWC device in severe waves. Based on the linear potential flow theory, the analytical solutions of the velocity potential in diffraction mode are solved by matching the Eigen-function expansion technique, and the continuous conditions of the velocity potential and fluid velocity between the computational sub-domains are involved in solving the problem for determining a solution. The proposed model is verified against the published data. The effects of the wave height, the angle of chamber clapboard and the radius of the inner and outer cylindrical column on the energy conversion efficiency are investigated in this paper. To improve the energy conversion performance and obtain a faster prediction for structural optimization of the cylindrical OWC, the geometrical parameters are further discussed in the analytical model. The results indicate that the geometrical parameters of the chamber have significant effects on the wave energy absorption efficiency. It is found that the effective frequency bandwidth of the dual cylindrical column can be broadened by improving the angle of the chamber clapboard and the inner–outer cylinder diameter ratio.

scholarly journals Wave-to-Wire Power Maximization Control for All-Electric Wave Energy Converters with Non-Ideal Power Take-Off

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2948
Author(s):  
Sousounis ◽  
Shek
Keyword(s):  
Wave Energy ◽  
Reactive Power ◽  
Energy Resource ◽  
Wave Energy Converter ◽  
Floating Body ◽  
Maximum Efficiency ◽  
Energy Converter ◽  
Electric Wave ◽  
Wave Energy Converters ◽  
Energy Converters

The research presented in this paper investigates novel ways of optimizing all-electric wave energy converters for maximum wave-to-wire efficiency. In addition, a novel velocity-based controller is presented which was designed specifically for wave-to-wire efficiency maximization. In an ideal wave energy converter system, maximum efficiency in power conversion is achieved by maximizing the hydrodynamic efficiency of the floating body. However, in a real system, that involves losses at different stages from wave to grid, and the global wave-to-wire optimum differs from the hydrodynamic one. For that purpose, a full wave-to-wire wave energy converter that uses a direct-drive permanent magnet linear generator was modelled in detail. The modelling aspect included complex hydrodynamic simulations using Edinburgh Wave Systems Simulation Toolbox and the electrical modelling of the generator, controllers, power converters and the power transmission side with grid connection in MATLAB/Simulink. Three reference controllers were developed based on the previous literature: a real damping, a reactive spring damping and a velocity-based controller. All three literature-based controllers were optimized for maximum wave-to-wire efficiency for a specific wave energy resource profile. The results showed the advantage of using reactive power to bring the velocity of the point absorber and the wave excitation force in phase, which was done directly using the velocity-based controller, achieving higher efficiencies. Furthermore, it was demonstrated that maximizing hydrodynamic energy capture may not lead to maximum wave-to-wire efficiency. Finally, the controllers were also tested in random sea states, and their performance was evaluated.

scholarly journals EXPERIMENTAL INVESTIGATION OF A CONCEPT WAVE ENERGY CONVERTER FOR HARNESSING LOW AMPLITUDE SEA WAVES

2020 ◽  
Vol 26 (3) ◽  
pp. 97-106
Author(s):  
OLAKUNLE KAYODE ◽  
TITUS OLUWASUJI AJEWOLE ◽  
OLUFEMI ADEBOLA KOYA
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Experimental Validation ◽  
Wave Energy Converter ◽  
Electricity Production ◽  
Sea Waves ◽  
Energy Converter ◽  
Point Absorber ◽  
Low Amplitude ◽  
Incident Waves

This paper presents the results from experimental validation of numerical simulation of a concept wave energy converter for low amplitude sea waves. The device was conceived to contain a wave amplifying device (WAD) to magnify the wave height of incident waves while point absorber buoy(s) efficiently harness the wave energy for electricity production. The validation results show that the optimum aperture angle for the WAD is 45±2 degree, and wave height magnification of 170% is possible. The optimal buoy shape for the device was confirmed as concave wedge buoy. The combination of the two in a single device shall make economical the harnessing of low amplitude waves.

scholarly journals WAVE ENERGY CONVERTER WITH WAVE ABSORBING CONTROL

2018 ◽  
pp. 61
Author(s):  
Takashi Kawaguchi ◽  
Kunio Nakano ◽  
Shogo Miyajima ◽  
Taro Arikawa
Keyword(s):  
Electric Power ◽  
Wave Energy ◽  
Wave Energy Converter ◽  
Tank Wall ◽  
Energy Converter ◽  
Reflected Waves ◽  
Wave Sensors ◽  
Incident Waves ◽  
The Waves

The wave absorbing control using wave sensors was theorized and developed by the authors, about 30 years ago. It was originally for absorbing wavemakers for tank tests in laboratories. This control enables wavemakers to generate the desired incident waves while absorbing undesirable reflected waves from the tank wall. When waves are absorbed by the wavemaker, the energy of the waves are also absorbed, that is, the energy is regenerated to electric power with the wavemaker drivemotor. According to this theory, in case that certain waves are generated by an oscillating body, these waves can be absorbed by the same body. Therefore, we can design a wave energy converter as a kind of absorbing wavemaker.

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