scholarly journals Dynamic Response Analysis of a Wavestar-Type Wave Energy Converter Using Augmented Formulation in Korean Nearshore Areas

Processes ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1721
Author(s):  
Sanghwan Heo ◽  
Weoncheol Koo
Keyword(s):  
Wave Energy ◽  
Environmental Conditions ◽  
Three Dimensional ◽  
Numerical Procedure ◽  
Response Analysis ◽  
Wave Forces ◽  
Wave Energy Converters ◽  
Augmented Formulation ◽  
Suitable Area ◽  
Promising Source

Interest in water wave power generation, a promising source of renewable energy, is increasing. Numerous types of wave energy converters (WECs) have been designed to transform wave energy into electricity. In this study, we focus on heaving point absorbers (HPAs) of the Wavestar type, which consist of multiple floats connected to a bottom-fixed ocean structure by structural arms and hinges. Each float moves up and down due to wave forces and produces electricity using the hydraulic power take-off (PTO) system connected directly to the float. A numerical procedure using the three-dimensional augmented formulation was developed to calculate the rotational motion of the float. The frequency-dependent coefficients were calculated using the hydrodynamic solver WAMIT. The nonlinear Froude–Krylov and hydrostatic forces were considered. For the environmental conditions, the wave data of four nearshore areas in Korea, obtained from the Korea Meteorological Administration (KMA), were used. Under the given environmental conditions, Buan was found to be the most suitable area among the locations selected for installing a Wavestar-type WEC without considering installation and maintenance costs.

Numerical Simulation of the Effect of Buoy Geometries on PTO of Wave Energy Converters

2021 ◽  
Author(s):  
Ahmed A. Hamada ◽  
Mirjam Furth
Keyword(s):  
Wave Energy ◽  
Single Point ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Energy Output ◽  
Navier Stokes ◽  
Design Parameters ◽  
Two Phase ◽  
Wave Energy Converters ◽  
Length To Diameter Ratio

Moving water has one of the highest energy densities, yet a major untapped and underutilized area of energy production is wave energy. With the recent interest in the Blue Economy, this is about to change. Point Wave Energy Converter (PWEC) absorbs the wave energy at a single point and is characterized by the buoy surface component and a longer subsurface component that is attached to the seabed. The motion of the top buoy is used to pump fluid or drive a linear generator, which in turn provides power. This paper numerically investigates different shaped surface buoys, with a focus on the power-generating ability of the system, for a single point WEC using a non-linear free surface approximation. Three-dimensional simulations of the buoys in various sea states were modeled in OpenFOAM using Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with Finite Volume Method (FVM). The dynamic mesh module was integrated with the two-phase solver, and the mechanical system of the WEC was modeled with a forced oscillator mechanism. By studying the displacements, frequency responses, and design parameters, the optimal buoy shape for maximizing energy output was determined. Further, the guidance regarding the effect of changes in the geometry, represented by the length to diameter ratio of the shape, is discussed. The results showed that the spheroid buoy shape with a low length to diameter ratio is a good candidate shape to extract wave energy since it has a large waterplane area.

Effect of Floaters’ Geometry on the Performance Characteristics of Tightly Moored Wave Energy Converters

2009 ◽  
Author(s):  
Spyros A. Mavrakos ◽  
Georgios M. Katsaounis ◽  
Michalis S. Apostolidis
Keyword(s):  
Wave Energy ◽  
Cylindrical Body ◽  
Performance Characteristics ◽  
Hydrodynamic Characteristics ◽  
Wave Forces ◽  
Diffraction Radiation ◽  
Wave Energy Converters ◽  
Internal Cone ◽  
Constant Displacement ◽  
Energy Converters

The paper deals with the investigation of the effect that floaters’ hydrodynamics has on the performance characteristics of tightly moored vertical axisymmetric wave energy converters. Several geometries of WEC’s floaters have been examined by assuming that they have constant displacement. Specifically, a cylindrical body with and without vertical and horizontal skirts at its bottom, a cone and a two–body, piston–like arrangement, which consists of an internal cone and an exterior torus, have been investigated and comparatively assessed. The WEC’s first-order hydrodynamic characteristics, i.e. their exciting wave forces and the correspondent hydrodynamic parameters, are evaluated using a linearized diffraction–radiation semi-analytical method. A dynamical model for evaluating of the floaters’ performance in time domain is developed that properly accounts for the floaters hydrodynamic behavior, the modeling of the hydraulic system and of the power take–off mechanism. The effect of the floaters geometry on the efficiency of the converter is analyzed through the results for the power absorption, under the excitation of several sea states.

scholarly journals Hydrodynamic Modelling of An Oscillating Wave Surge Converter Including Power Take-Off

2020 ◽  
Vol 8 (10) ◽  
pp. 771
Author(s):  
Daniela Benites-Munoz ◽  
Luofeng Huang ◽  
Enrico Anderlini ◽  
José R. Marín-Lopez ◽  
Giles Thomas
Keyword(s):  
Wave Energy ◽  
Stokes Equations ◽  
Three Dimensional ◽  
High Amplitude ◽  
Realistic Model ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Wave Energy Converters ◽  
Fluid Field ◽  
Incident Waves

To estimate the response of wave energy converters to different sea environments accurately is an ongoing challenge for researchers and industry, considering that there has to be a balance between guaranteeing their integrity whilst extracting the wave energy efficiently. For oscillating wave surge converters, the incident wave field is changed due to the pitching motion of the flap structure. A key component influencing this motion response is the Power Take-Off system used. Based on OpenFOAM, this paper includes the Power Take-off to establish a realistic model to simulate the operation of a three-dimensional oscillating wave surge converter by solving Reynolds Averaged Navier-Stokes equations. It examines the relationship between incident waves and the perturbed fluid field near the flap, which is of great importance when performing in arrays as neighbouring devices may influence each other. Furthermore, it investigates the influence of different control strategy systems (active and passive) in the energy extracted from regular waves related to the performance of the device. This system is estimated for each wave frequency considered and the results show the efficiency of the energy extracted from the waves is related to high amplitude pitching motions of the device in short periods of time.

Parametric Evaluation of the Performance Characteristics of Tight Moored Wave Energy Converters

2005 ◽  
Author(s):  
Spyridon A. Mavrakos ◽  
Georgios M. Katsaounis
Keyword(s):  
Wave Energy ◽  
Wave Climate ◽  
The Body ◽  
Performance Characteristics ◽  
Hydrodynamic Characteristics ◽  
Wave Forces ◽  
Diffraction Radiation ◽  
Climate Conditions ◽  
Wave Energy Converters ◽  
Energy Converters

The paper aims at presenting a numerical model to predict performance characteristics of tight moored vertical axisymmetric wave energy converters that are allowed to move in heave, pitch and sway modes of motion. The hydrodynamic characteristics (exciting wave forces, hydrodynamic parameters) of the floats are evaluated using a linearized diffraction–radiation method of analysis that is suited for the type of bodies under consideration. According to this method matched axisymmetric eigenfunction expansions of the velocity potentials in properly defined fluid regions around the body are introduced to solve the respective diffraction and radiation problems and to calculate the floats’ hydrodynamic characteristics in the frequency domain. Based on these characteristics, the retardation forcing terms are calculated, which account for the memory effects of the motion. In this procedure, the coupling terms between the different modes of motion are properly formulated and taken into account. The floating WEC is connected to an underwater piston that feeds a hydraulic system with pressurized fluid. Numerical results showing parametrically the performance characteristics in terms of the expected power production for several types of floats that are exposed to the wave climate conditions commonly encountered in the Mediterranean area are presented and discussed.

scholarly journals Effect of Flap Type Wave Energy Converters on the Response of a Semi-Submersible Wind Turbine in Operational Conditions

2014 ◽  
Author(s):  
Constantine Michailides ◽  
Chenyu Luan ◽  
Zhen Gao ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Wave Energy ◽  
Environmental Conditions ◽  
Operational Conditions ◽  
Critical Response ◽  
Type Wave ◽  
Wave Energy Converters ◽  
Combined Operation ◽  
Energy Converters

In the present paper the effect of flap type wave energy converters on the response of a floating semi-submersible wind turbine is investigated and reported. Two different layouts with regard to the number of rotating flaps that are utilized are considered and compared with the case of a pure floating semi-submersible wind turbine. Comparisons of response in terms of stability, motions and internal loads are made for selected environmental conditions. The combined operation of the rotating flaps results in an increase of the produced power without affecting significantly selected critical response quantities of the semi-submersible platform.

Point Absorber Design for a Combined Wind and Wave Energy Converter on a Tension-Leg Support Structure

2013 ◽  
Author(s):  
Erin E. Bachynski ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Wave Energy ◽  
Environmental Conditions ◽  
Energy Extraction ◽  
Energy Converter ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Single Column ◽  
Extraction Device ◽  
Heave Motion

A combined wind and wave energy extraction device is studied, consisting of a single column tension leg platform (TLP) which supports a 5MW wind turbine (WT) and 3 point absorber wave energy converters (WECs). Two variations of the WECs are considered: one that is constrained to purely heave motion relative to the TLP hull, and a hinged device which moves in coupled surge and pitch as well as heave. The effects of both types of WECs on the WT power takeoff; on structural loads in the turbine tower and blades, WEC supporting structure, and tendons; and on the platform motions are examined for operational and 50-year extreme environmental conditions.

Hydrodynamic Response Analysis and Wave Energy Absorption of Wave Energy Converters in Regular Waves

2017 ◽  
Vol 51 (1) ◽  
pp. 64-74
Author(s):  
Hong Gao ◽  
Zhiheng Wang
Keyword(s):  
Wave Energy ◽  
Absorption Efficiency ◽  
Center Of Gravity ◽  
Total Power ◽  
Response Analysis ◽  
Optimum Frequency ◽  
Power Absorption ◽  
Wave Energy Converters ◽  
Hydrodynamic Response ◽  
Energy Converters

AbstractThe hydrodynamic response and the energy capture analysis of wave energy converters (WECs) with three degrees of freedom are conducted using a frequency domain approach. Considering the coupled hydrodynamic coefficients between surge and pitch, motion responses in surge, heave, and pitch are solved for the WECs. The power take-off (PTO) damping is taken as a linear function of the velocity. The power absorption and the absorption efficiency in surge, heave, and pitch are analyzed and compared. The effects of the geometry, diameter, draft, center of gravity position, and PTO damping on the hydrodynamic response, the power absorption, and the absorption efficiency of WECs are investigated. A cylinder, a halfsphere cylinder, and a cone cylinder are examined. From the total power absorption and the efficiency, the cone is the optimum geometry. For the cylinder, the power absorption in heave increases obviously with the increase of the diameter or the draft in a certain range. For the cone, the effect of diameter and draft on the power absorption in heave is relatively small. The cone has a better ability to absorb power in surge and pitch with an intermediate draft and diameter, and the power absorption peak in pitch decreases as Zg increases. The center of gravity position has no effect on the hydrodynamic response and the power absorption in heave. For a cylinder, the optimal PTO damping in heave is higher than that in pitch and surge. The optimum frequency in heave is lower than that in pitch and surge.

3D Efficiency Analysis of Cycloidal Wave Energy Converters in Oblique Wave Fields

2013 ◽  
Author(s):  
Casey Fagley ◽  
Stefan G. Siegel ◽  
Jürgen Seidel ◽  
Christian Schmittner
Keyword(s):  
Wave Energy ◽  
Wave Length ◽  
Three Dimensional ◽  
Energy Converter ◽  
Offshore Technology ◽  
Wave Energy Converters ◽  
Diffraction Model ◽  
Wave Basin ◽  
Wave Patterns ◽  
Diffraction Effects

Numerical results from a 3D diffraction model are presented where a Cycloidal Wave Energy Converter (CycWEC) is interacting with an incoming straight crested Airy Wave. The diffraction model was developed in response to experimental observations from 1:10 scale experiments which were conducted in the Texas A&M Offshore Technology Research center wave basin. These experiments were the first investigations involving a CycWEC where three dimensional wave diffraction effects were present due to the fact that the span of the CycWEC was much smaller than the width of the basin. The diffraction model predicted the observed surface wave patterns in the experiment well, and showed that diffraction induced wave focusing increased the recoverable wave power beyond the 2D predictions for small CycWEC spans, while approaching the 2D limit for very large spans. The numerical model was subsequently used to estimate the sensitivity of the CycWEC to misalignment between the incoming waves and the WEC shaft. The loss in efficiency was found to be strongly dependent on the ratio between WEC span and incoming wavelength, where short spans (on the order of one wave length or less) which are realistic for actual ocean deployment showed only minor reductions in efficiency, while very long spans were found to be more sensitive to misalignment.

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