scholarly journals Wave Power Absorption by Arrays of Wave Energy Converters in Front of a Vertical Breakwater: A Theoretical Study

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1985 ◽  
Author(s):  
Dimitrios N. Konispoliatis ◽  
Spyridon A. Mavrakos
Keyword(s):  
Wave Energy ◽  
Cylindrical Wave ◽  
Hydrodynamic Characteristics ◽  
Linear Potential ◽  
Theoretical Evaluation ◽  
Power Absorption ◽  
Array Configuration ◽  
Wave Energy Converters ◽  
Vertical Breakwater ◽  
Energy Converters

The present paper deals with the theoretical evaluation of the efficiency of an array of cylindrical Wave Energy Converters (WECs) having a vertical symmetry axis and placed in front of a reflecting vertical breakwater. Linear potential theory is assumed, and the associated diffraction and motion radiation problems are solved in the frequency domain. Axisymmetric eigenfunction expansions of the velocity potential are introduced into properly defined ring-shaped fluid regions surrounding each body of the array. The potential solutions are matched at the boundaries of adjacent fluid regions by enforcing continuity of the hydrodynamic pressures and redial velocities. A theoretical model for the evaluation of the WECs’ performance is developed. The model properly accounts for the effect of the breakwater on each body’s hydrodynamic characteristics and the coupling between the bodies’ motions and the power take-off mechanism. Numerical results are presented and discussed in terms of the expected power absorption. The results show how the efficiency of the array is affected by (a) the distance between the devices and the wall, (b) the shape of the WEC array configuration, as well as (c) the angle of the incoming incident wave.

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

Scale and Configuration Effects of an Airchamber on PTO of Oscillating Water Column Type Wave Energy Converters

2021 ◽  
Author(s):  
Tomoki Ikoma ◽  
Shota Hirai ◽  
Yasuhiro Aida ◽  
Koichi Masuda
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Water Surface ◽  
Air Pressure ◽  
Scale Model ◽  
Linear Potential ◽  
Oscillating Water Column ◽  
Wave Energy Converters ◽  
Air Chamber ◽  
Energy Converters

Abstract Wave energy converters (WECs) have been extensively researched. The behaviour of the oscillating water column (OWC) in OWC WECs is extremely complex due to the interaction of waves, air, and turbines. Several problems must be overcome before such WECs can be put to practical use. One problem is that the effect of the difference in scale between a small-scale experimental model and a full-scale model is unclear. In this study, several OWC models with different scales and geometries were used in forced oscillation tests. The wave tank was 7.0 m wide, 24.0 m long, and 1.0 m deep. In the static water experiment, we measured the air pressure and water surface fluctuations in an air chamber. For the experiments, models with a box shape with an open bottom, a manifold shape with an open bottom, and a box shape with a front opening, respectively, were fabricated. Furthermore, 1/1, 1/2, and 1/4 scale models were fabricated for each shape to investigate the effects of scale and shape on the air chamber characteristics. Numerical calculations were carried out by applying linear potential theory and the results were compared with the experimental values. The results confirmed that the air chamber shape and scale affect the air pressure fluctuation and water surface fluctuation inside the OWC system.

scholarly journals Performance of an Array of Oblate Spheroidal Heaving Wave Energy Converters in Front of a Wall

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 188 ◽  
Author(s):  
Eva Loukogeorgaki ◽  
Ifigeneia Boufidi ◽  
Ioannis K. Chatjigeorgiou
Keyword(s):  
Wave Energy ◽  
Vertical Wall ◽  
Integral Equation Method ◽  
Boundary Integral ◽  
Power Absorption ◽  
Enhanced Absorption ◽  
Wave Energy Converters ◽  
Oblate Spheroidal ◽  
Specific Frequency ◽  
Energy Converters

In this paper, we investigate the performance of a linear array of five semi-immersed, oblate spheroidal heaving Wave Energy Converters (WECs) in front of a bottom-mounted, finite-length, vertical wall under perpendicular to the wall regular waves. The diffraction and radiation problems are solved in the frequency domain by utilizing the conventional boundary integral equation method. Initially, to demonstrate the enhanced absorption ability of this array, we compare results with the ones corresponding to arrays of cylindrical and hemisphere-shaped WECs. Next, we investigate the effect of the array’s distance from the wall and of the length of the wall on the physical quantities describing the array’s performance. The results illustrate that the array’s placement at successively larger distances from the wall, up to three times the WECs’ radius, induces hydrodynamic interactions that improve the array’s hydrodynamic behavior, and thus its power absorption ability. An increase in the length of the wall does not lead to any significant power absorption improvement. Compared to the isolated array, the presence of the wall affects positively the array’s power absorption ability at specific frequency ranges, depending mainly on the array’s distance from the wall. Finally, characteristic diffracted wave field patterns are presented to interpret physically the occurrence of the local minima of the heave exciting forces.

The Economics of Multi-Axis Point Absorber Wave Energy Converters

2013 ◽  
Author(s):  
Daniel S. Richardson ◽  
George A. Aggidis
Keyword(s):  
Wave Energy ◽  
Performance Comparison ◽  
Linear Potential ◽  
Advantages And Disadvantages ◽  
Point Absorber ◽  
Wave Energy Converters ◽  
Point Absorbers ◽  
Linear Potential Theory ◽  
Economic Comparison ◽  
Energy Converters

This paper examines the economic advantages and disadvantages of multi-axis point absorber wave energy converters in comparison to conventional heave-only point absorbers. A multi-axis point absorber wave energy converter (MA-PAWEC) is classified as a point absorber device that has a power take off (PTO) system extracting energy from more than one mode of motion (e.g. heave and surge). The majority of existing point absorber devices operate in heave mode alone. Therefore the forces exerted along other axes must be resisted by the mooring system, any reciprocal component of which constitutes a wasted opportunity to extract energy. The economics of PAWECs are governed by the available resource, energy generated by the device, capital cost and operational cost. These factors are examined for MA-PAWECs and compared to a generic heave-PAWEC. For a performance comparison, a simple generic body PAWEC is examined under heave mode operation and multi-axis operation in a representative spectrum. The modelling is based on linear potential theory. The potential advantages of MA-PAWECS are identified as greater energy absorption, fewer installed devices for a given capacity, and greater array control. Disadvantages include higher capex, higher maintenance costs and sensitivity to PTO costs. The performance and costs are assigned an estimated economic scaling factor and are applied to a generic heave-PAWEC for an economic comparison of the two devices. This indicates that a multi-axis approach to point absorbers could offer a 21% lower cost of electricity than the incumbent heave-response devices.

Numerical Modeling and Evaluation of Wave Energy Converters

2009 ◽  
Author(s):  
Heather Peng ◽  
Wei Qiu ◽  
Don Spencer
Keyword(s):  
Numerical Modeling ◽  
Frequency Domain ◽  
Wave Energy ◽  
Energy Production ◽  
Wave Power ◽  
Power Absorption ◽  
Wave Energy Converters ◽  
Numerical Studies ◽  
The Waves ◽  
Energy Converters

Wave energy converters use the motion of floating or submerged bodies to extract energy from the waves. Power absorption can be simulated using a simple linear damper with a resistance to motion which is proportional to velocity. Because of the interaction between energy production and motion, there will be an optimum rate of energy production for each wave frequency. Too much damping or too little damping can cause little energy produced. The wave absorption range also depends on the tuned frequency. In this paper, the maximum rates of energy absorption for submerged and floating wave energy converters are evaluated by employing the panel-free method for the motions of the converters in the frequency domain. A general expression for the wave power absorption is described. Numerical studies show that the optimal energy efficiencies of wave energy converters can be well predicted by employing the panel-free method for motion computations.

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 Wave energy resource variation off the west coast of Ireland and its impact on realistic wave energy converters’ power absorption

2018 ◽  
Vol 224 ◽  
pp. 205-219 ◽  
Author(s):  
Markel Penalba ◽  
Alain Ulazia ◽  
Gabriel Ibarra-Berastegui ◽  
John Ringwood ◽  
Jon Sáenz
Keyword(s):  
Wave Energy ◽  
West Coast ◽  
Energy Resource ◽  
The West ◽  
Power Absorption ◽  
Wave Energy Converters ◽  
Energy Converters ◽  
Resource Variation
Sign in / Sign up

Export Citation Format

Share Document