Power Absorption by Arrays of Interacting Vertical Axisymmetric Wave-Energy Devices

1997 ◽  
Vol 119 (4) ◽  
pp. 244-251 ◽  
Author(s):  
S. A. Mavrakos ◽  
A. Kalofonos
Keyword(s):  
Multiple Scattering ◽  
Wave Energy ◽  
Numerical Results ◽  
Hydrodynamic Characteristics ◽  
Wave Power ◽  
Interference Effects ◽  
Power Absorption ◽  
Energy Devices ◽  
Single Body ◽  
Absorption Characteristics

The paper deals with the evaluation of the optimum wave-power absorption characteristics of arrays of interacting wave-energy devices. The hydrodynamic interference effects among the devices are exactly accounted for using a method that can solve the problem to any desired accuracy. The method is based on single-body hydrodynamic characteristics that are properly combined through the physical idea of multiple scattering to account for interaction effects. Extensive numerical results for a variety of different array arrangements and individual device geometries are presented and comparisons are made to predictions based on approximate theories, the accuracy of which is critically assessed.

Characteristics of Hydrodynamics and Generating Output of the Offshore Floating Wave Energy Device “Mighty Whale”

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
Hiroyuki Osawa ◽  
Tsuyoshi Miyazaki ◽  
Shogo Miyajima
Keyword(s):  
Energy Absorption ◽  
Output Power ◽  
Wave Energy ◽  
Power Device ◽  
Hydrodynamic Characteristics ◽  
Wave Power ◽  
Water Tank ◽  
Power Devices ◽  
Turbine Generator ◽  
Generator System

In this paper, a new numerical calculation method is presented; it was developed for the analysis of the hydrodynamic characteristics of a floating, oscillating water column (OWC) type wave power device. The method is examined by comparing results calculated with the method with results of water tank experiments. The examination was concerned with the determination of hydrodynamic coefficients, characteristics of air pressure and water level in an air chamber, and characteristics of hull motion and wave energy absorption. The calculated results agreed with the results of water tank tests; the method presented adequately estimated the hydrodynamic characteristics of the floating OWC type wave power device, including the wave energy absorption effects. An estimation method is presented for the output power of a turbine-generator system. The method was developed for the design of the “Mighty Whale” turbine-generator system. Moreover, the method was assessed by comparing predictions with open sea test results. The mean value of the output power was estimated reasonably well. In conclusion, the estimation methods presented are useful for the design of floating OWC wave power devices. Such tools are useful for the designer interested in developing optimal wave power devices.

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.

Wave Energy Assessments in the Coastal Environment of Portugal Continental

2008 ◽  
Author(s):  
Eugen Rusu ◽  
C. Guedes Soares
Keyword(s):  
Wave Energy ◽  
Numerical Models ◽  
Specific Area ◽  
Wave Climate ◽  
Coastal Environment ◽  
Wave Power ◽  
Relevant Parameter ◽  
Density Spectrum ◽  
Energy Devices ◽  
Power Resources

The potential for wave energy extraction can be obtained from the analysis of the wave climate which can be determined with numerical models. The wave energy devices can be deployed in offshore, nearshore and shoreline. From this reason, it is important to be able to assess properly the spatial distribution of the wave energy in various locations from the offshore to the coastline in a specific area. The methodology proposed here considers a SWAN based wave model system focusing in the Portuguese continental coastal environment from deep water towards the nearshore. An analysis of the average and high energetic conditions was first performed for a ten-year period, between 1994 and 2003, considering the most relevant in situ measurements available in the Portuguese nearshore. In this way both the average and high energetic conditions corresponding to the Portuguese continental costal environment have been properly defined. For the most relevant average wave conditions, SWAN simulations were performed in some medium resolution areas covering the northern and central parts of Portugal continental, which are traditionally considered richer in wave power resources. The present work allows the identification of some locations in the continental coastal environment of Portugal with greater potential from the point of view of wave power resources. An important observation is related to the fact that the wave power depends on the product between the energy density spectrum and the group velocity of waves. This means that, although the significant wave height is a relevant parameter when assessing the wave power in a specific site, a location having in general higher wave heights is not necessarily also the richest in wave power.

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.

Multiple scattering in arrays of axisymmetric wave-energy devices. Part 1. A matrix method using a plane-wave approximation

1982 ◽  
Vol 120 ◽  
pp. 1-25 ◽  
Author(s):  
M. J. Simon
Keyword(s):  
Multiple Scattering ◽  
Wave Energy ◽  
Matrix Method ◽  
Finite Size ◽  
Finite Size Effects ◽  
Energy Devices ◽  
Axisymmetric Wave ◽  
Mass Matrices ◽  
The Matrix ◽  
Exciting Forces

A technique is developed to model the multiple scattering of surface waves in an array of axisymmetric wave-energy devices. The matrix equation which results is inverted to yield the exciting forces, the added-damping and added-mass matrices, the optimal power absorption and the optimal device responses. The matrix method is also used on the previously unstudied problem of an unconstrained array. Finite-size effects of devices are shown to be important in producing phase-shifts, which shift the uncon- strained frequency response, but leave the opt,imal energy absorption virtually unchanged.

A Design for the Wave Power Generation Conversion Device

2014 ◽  
Vol 1030-1032 ◽  
pp. 472-475
Author(s):  
Shi Ming Wang ◽  
Yao Li ◽  
Hao Zhan ◽  
Ka Tian
Keyword(s):  
Power Generation ◽  
Wave Energy ◽  
Control Device ◽  
Wave Power ◽  
Good Prospect ◽  
Energy Devices ◽  
New Energy ◽  
Power Generation Equipment ◽  
Torque Capacity ◽  
Wave Power Generation

In recent years, the concept of renewable energy has been deepening and popularization, all kinds of new energy technology is developed by leaps and bounds, a growing number of wave energy devices has been put into use and has a very good prospect. In wave power generation equipment, the conversion transmission device is a very important unit, which involving energy transfer, adjustment, stable output and buffer storage, so it need to be well designed to satisfy the operational requirement by taking advantage of different parts. By analyzing the commonly used conversion transmission devices, the characteristics of transmission devices and wave power generation equipments, we proposing a design of a flexible transmission device which can change its torque capacity with clutch automatic control device, in the form of its layout to drive a train of thought for the design wave energy conversion.

Floating Wave Energy Device With Two Oscillating Water Columns

2007 ◽  
Author(s):  
D. C. Hong ◽  
S. Y. Hong
Keyword(s):  
Green Function ◽  
Wave Energy ◽  
Numerical Results ◽  
The Body ◽  
Energy Device ◽  
Energy Devices ◽  
Damping Parameter ◽  
Absorbed Power ◽  
Linear Damping ◽  
Drift Force

The absorbed power, motion and drift force of a floating wave energy device with two oscillating water column (OWC) chambers are studied taking account of the interaction between two chambers within the scope of the linear wave theory. The oscillating surface-pressure in the OWC chamber is represented by a product of the air-flow velocity and an equivalent linear damping parameter. The two-dimensional potential problem is formulated as a hybrid Green integral equation using the Rankine Green function inside the chamber and the finite-depth free-surface Green function outside respectively. The present numerical method makes it possible to tune the OWC and the floating body motions to the incident waves that is essential to maximize the absorbed power. The absorbed powers are calculated by both the near-field and far-field methods for various values of the linear damping parameter in two chambers. The reflection and transmission coefficients of the body are also presented. The numerical results for one OWC devices where the OWC is placed in a backward and forward bent duct buoys (BBDB and FBDB) are also presented for comparison of the performance. The present floating wave energy devices can also be served as a good floating breakwater having small drift force. The present numerical results show that the existence of reverse time-mean horizontal wave drift force is not contradictory to the principle of wave energy conservation.

scholarly journals On Power-Absorption Degrees of Freedom for Point Absorber Wave Energy Converters

2020 ◽  
Vol 8 (9) ◽  
pp. 711
Author(s):  
Jinming Wu
Keyword(s):  
Wave Energy ◽  
Degrees Of Freedom ◽  
Center Of Mass ◽  
Width Ratio ◽  
Rotational Inertia ◽  
Wave Power ◽  
Cylindrical Shape ◽  
Internal Mass ◽  
Power Absorption ◽  
Point Absorber

Point absorbers are extensively employed in wave energy conversion. In this work, we studied the point absorber with the buoy of a vertical cylindrical shape. Wave power absorption is obtained through the relative motion between the buoy and an internal mass. Three power-absorption degrees of freedom are investigated, i.e., surge, heave, and pitch, together with the influence of wave compliance of the buoy. Results show that, to absorb more power, the internal mass should be as large as possible for power absorption in translational degrees of freedom, i.e., surge and heave. The total rotational inertia should be as large as possible and the center of mass should be as low as possible for power absorption in pitch. Wave compliance of the buoy slightly enhances the power absorption in surge, but significantly weakens the power absorption in pitch. Surge is the best degree of freedom for power absorption owing to the highest efficiency, indicated by the largest capture width ratio. The simple resistive control is found to be adequate for wave power absorption of the self-reacting point absorber.

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