scholarly journals Evaluation of the energy extraction of a small-scale wave energy converter

RBRH ◽  
2019 ◽  
Vol 24 ◽  
Author(s):  
Carla de Abreu D’Aquino ◽  
Cesar Cataldo Scharlau ◽  
Leonardo Casagrande Dalla Vecchia
Keyword(s):  
Wave Energy ◽  
Electric Energy ◽  
Wave Theory ◽  
Small Scale ◽  
Linear Wave ◽  
Energy Extraction ◽  
Wells Turbine ◽  
Global Challenge ◽  
Integrated Devices ◽  
Main Components

ABSTRACT This work aims to focus on proposals that could stimulate the development of small scale integrated devices for the global challenge to provide electric energy from renewable alternative resources without major interventions. It presents an evaluation of a small-scale wave energy extraction system that can be installed in marine near shore structures, such as fishing piers. The system is characterized by a small oscillating-water-column (OWC) converter composed by tubes tied to the pillars of the structure. A mathematical model of the OWC device was developed. The model relies on two main components. The first uses linear wave theory to describe the water level variation inside the tube as a result of a wave passing by. The second considers the air flux converted to mechanical torque using Wells turbine equations. The simulations were carried out for different water depths and wave parameters, to evaluate the ratio between the input and output energy throughout the year. For the case study presented in this paper, the performance would be better as long as the device is placed in a position where the waves are less influenced by the bottom friction, but it still has the necessary increment of the wave height.

A Joint Numerical and Experimental Study of a Surging Point Absorbing Wave Energy Converter (WRASPA)

2009 ◽  
Author(s):  
Majid A. Bhinder ◽  
Clive G. Mingham ◽  
Derek M. Causon ◽  
Mohammad T. Rahmati ◽  
George A. Aggidis ◽  
...  
Keyword(s):  
Wave Energy ◽  
Informed Choice ◽  
Wave Energy Converter ◽  
Body Motion ◽  
Numerical Dissipation ◽  
Small Scale ◽  
Linear Wave ◽  
Energy Converter ◽  
Non Linear ◽  
Experimental Project

This paper presents the findings from using several commercial computational fluid dynamics codes in a joint numerical and experimental project to simulate WRASPA, a new wave energy converter (WEC) device. A series of fully 3D non-linear simulations of WRASPA are presented. Three commercial codes STAR-CCM, CFX and FLOW-3D are considered for simulating the WRASPA device and final results are presented based on the use of Flow-3D. Results are validated by comparison to experimental data obtained from small scale tank tests undertaken at Lancaster University (LU). The primary aim of the project is to use numerical simulation to optimize the collector geometry for power production over a range of likely wave climates. A secondary aim is to evaluate the ability of commercial codes to simulate rigid body motion in linear and non-linear wave climates in order to choose the optimal code with respect to compute speed and ease of problem setup. Issues relating to the ability of a code in terms of numerical dissipation of waves, wave absorption, wave breaking, grid generation and moving bodies will all be discussed. The findings of this paper serve as a basis for an informed choice of commercial package for such simulations. However the capability of these commercial codes is increasing with every new release.

Wave Energy Extraction From Multiple Buoys Supporting a Flexible Runway

2017 ◽  
Author(s):  
H. C. Zhang ◽  
D. L. Xu ◽  
Q. H. Li
Keyword(s):  
Wave Energy ◽  
Research Work ◽  
Algebraic Method ◽  
Wave Theory ◽  
Energy Utilization ◽  
Linear Wave ◽  
Wave Condition ◽  
Wave Energy Converters ◽  
The Cost ◽  
Wave Farm

Integrating an array of buoys type converters with a flexible runway can be a viable option for cost-sharing between wave energy capturing devices and ocean space utilization structures, and thus enhance the cost-effectiveness of wave energy utilization. In this study, a configuration of multiple buoys supporting a runway is proposed. Hydrodynamic interactions among the buoys are analyzed using an exact algebraic method based on linear wave theory in the frequency domain. A parametric governing equation of compound wave energy converter referred to as a wave farm is formulated by using Hamilton’s principle which can be discretized by using Galerkin method. The effects of wave condition and the parameters of PTO on the wave energy absorption and dynamic characteristics of a runway are analyzed. This research work is aimed to provide a theoretical guideline for wave energy converters design.

The Spring-Like Air Compressibility Effect in OWC Wave Energy Converters: Hydro-, Thermo- and Aerodynamic Analyses

2018 ◽  
Author(s):  
António F. O. Falcão ◽  
João C. C. Henriques
Keyword(s):  
Wave Energy ◽  
Process Model ◽  
Wave Theory ◽  
Theoretical Models ◽  
Irregular Waves ◽  
Power Performance ◽  
Floating Structure ◽  
Wells Turbine ◽  
Compressibility Effect ◽  
Linear Water Wave Theory

The oscillating-water-column (OWC) wave energy converter consists of a hollow (fixed or floating) structure, open to the sea below the water surface. Wave action alternately compresses and decompresses the air trapped above the inner water free-surface, which forces air to flow through a turbine coupled to a generator. The spring-like effect of air compressibility in the chamber is related to the density-pressure relationship. It is known to significantly affect the power performance of the full-sized converter, and is normally not accounted for in model testing at reduced scale. Three theoretical models of increasing complexity are analysed and compared: (i) the incompressible air model; (ii) the isentropic process model; (iii) and the (more difficult and rarely adopted) adiabatic non-isentropic process model in which losses due to the imperfectly efficient turbine are accounted for. The air is assumed as a perfect gas. The hydrodynamic modelling of wave energy absorption is based on linear water wave theory. The validity of the various simplifying assumptions, especially in the aero-thermodynamic domain, is examined and discussed. The validity of the three models is illustrated by a case study with numerical results for a fixed-structure OWC equipped with a Wells turbine subject to irregular waves.

scholarly journals A Coupled Methodology for Wave-Body Interactions at the Scale of a Farm of Wave Energy Converters Including Irregular Bathymetry

2014 ◽  
Author(s):  
François Charrayre ◽  
Christophe Peyrard ◽  
Michel Benoit ◽  
Aurélien Babarit
Keyword(s):  
Wave Energy ◽  
Diffraction Problem ◽  
Wave Theory ◽  
Field Approximation ◽  
Coupling Scheme ◽  
Linear Wave ◽  
Wave Energy Converters ◽  
Mild Slope Equation ◽  
Wave Farm ◽  
Energy Converters

Knowledge of the wave perturbation caused by an array of Wave Energy Converters (WEC) is of great concern, in particular for estimating the interaction effects between the various WECs and determining the modification of the wave field at the scale of the array, as well as possible influence on the hydrodynamic conditions in the surroundings. A better knowledge of these interactions will also allow a more efficient layout for future WEC farms. The present work focuses on the interactions of waves with several WECs in an array. Within linear wave theory and in frequency domain, we propose a methodology based on the use of a BEM (Boundary Element Method) model (namely Aquaplus) to solve the radiation-diffraction problem locally around each WEC, and to combine it with a model based on the mild slope equation at the scale of the array. The latter model (ARTEMIS software) solves the Berkhoff’s equation in 2DH domains (2 dimensional code with a z-dependence), considering irregular bathymetries. In fact, the Kochin function (a far field approximation) is used to propagate the perturbations computed by Aquaplus into Artemis, which is well adapted for a circular wave representing the perturbation of an oscillating body. This approximation implies that the method is only suitable for well separated devices. A main advantage of this coupling technique is that Artemis can deal with variable bathymetry. It is important when the wave farm is in shallow water or in nearshore areas. The methodology used for coupling the two models, with the underlying assumptions is detailed first. Validations test-cases are then carried out with simple bodies (namely heaving vertical cylinders) to assess the accuracy and efficiency of the coupling scheme. These tests also allow to analyze and to quantify the magnitude of the interactions between the WECs inside the array.

Validation of a Quasi-Linear Numerical Model of a Pitching Wave Energy Converter in Close Proximity to a Fixed Structure

2017 ◽  
Author(s):  
Pilar Heras ◽  
Sarah Thomas ◽  
Morten Kramer
Keyword(s):  
Numerical Model ◽  
Linear Theory ◽  
Wave Energy ◽  
Wave Theory ◽  
Domain Model ◽  
Linear Wave ◽  
Energy Devices ◽  
Wave Energy Converters ◽  
Close Proximity ◽  
Fixed Structure

Although linear theory is often used to analyse wave energy devices, it is in many cases too simplistic. Many wave energy converters (WECs) exceed the key linear theory assumption of small amplitudes of motion, and require the inclusion of non-linear forces. A common approach is to use a hybrid frequency-time domain model based on the Cummins equation with hydro-dynamic inputs coming from linear wave theory (Ref. [1]). Published experimental data is sparse (Ref. [2]) and the suitability for the broad variety of WEC technologies has yet to be proven. This paper focuses on the challenges faced when attempting to validate a numerical model of a WEC using a variety of scaled physical tests in a waveflume. The technology used as a case study in this paper is a pitching WEC in close proximity to a fixed structure. Challenges are presented relating to waveflume effects and obtaining accurate physical input parameters to the numerical model.

Design and test of a novel two-body direct-drive wave energy converter

2020 ◽  
pp. 1-18
Author(s):  
Chuan Liu ◽  
Renwen Chen ◽  
Yuxiang Zhang ◽  
Wen Liu ◽  
Liping Wang ◽  
...  
Keyword(s):  
Permanent Magnet ◽  
Wave Energy ◽  
Fem Simulation ◽  
Wave Theory ◽  
Wave Energy Converter ◽  
Linear Wave ◽  
Direct Drive ◽  
Energy Converter ◽  
Motion Equations ◽  
Linear Generator

As a renewable energy, ocean wave energy is exploited with infinite potential to solve the energy crisis. In this study, we develop a novel two-body direct-drive wave energy converter (DD-WEC) to surmount the problems associated with low power density, low direct-drive speed of the buoys, seawater corrosion and maintenance in the existing two-body WEC. Its prototype consists of two cylindrical buoys are utilized that float horizontally at sea level and the Halbach permanent magnet linear generator (HPMLG) that is employed in the power take-off (PTO) system. The energy is extracted from the relative motion between two buoys oscillating. Compared with the existing WEC, the proposed WEC has more vigorous motion between buoys, higher conversion efficiency and little extra underwater structure, due to the utilization of the horizontal buoys and the HPMLG. First, the motion equations of buoys are derived on the basis of linear wave theory. And depending on the motion equations, the structure of buoys and the HPMLG is designed. And we found that compared with the existing WEC, the proposed WEC has more vigorous motion between buoys in the seawater waves oscillation. Then, based on finite-element method (FEM), the performance of the HPMLG is evaluated, and it can generate 19% more power than the traditional permanent magnet linear generator (TPMLG) based on the same wave motion. Finally, the DD-WEC prototype is manufactured based on the designed parameter. The manufactured prototype is tested in the test platform and the wave tank. The measured output voltage is highly consistent with the observed variation trends in FEM simulation data. The results show that the proposed DD-WEC is well suited for wave energy conversion.

scholarly journals Wave Energy Potential and Simulation on the Andaman Sea Coast of Thailand

2020 ◽  
Vol 12 (9) ◽  
pp. 3657 ◽  
Author(s):  
Chutipat Foyhirun ◽  
Duangrudee Kositgittiwong ◽  
Chaiwat Ekkawatpanit
Keyword(s):  
Wave Height ◽  
Wave Energy ◽  
Measurement Data ◽  
Wave Theory ◽  
Andaman Sea ◽  
Linear Wave ◽  
Energy Potential ◽  
Significant Wave ◽  
Linear Wave Theory ◽  
Swan Model

Ocean wave energy is an interesting renewable energy because it will never run out and can be available all the time. If the wave energy is to be used, then the feasibility study of localized wave potential has to be studied. This goal is to study the potential of waves in the Andaman Sea. The Simulating WAves Nearshore (SWAN) model was used to calculate the significant wave heights, which were validated with the measurement data of the Jason-2 satellite. The coastal area of Phuket and Phang Nga provinces are suitable locations for studying wave energy converters because they have high significant wave height. Moreover, this study used computational fluid dynamics (CFD) for the simulation of wave behavior in accordance with wave parameters from the SWAN model. The wave height simulated from CFD was validated with linear wave theory. The results found that it was in good agreement with linear wave theory. It can be applied for a simulation of the wave energy converter.

Wave generation by an oscillating surface-pressure and its application in wave-energy extraction

1985 ◽  
Vol 150 ◽  
pp. 467-485 ◽  
Author(s):  
A. J. N. A. Sarmento ◽  
A. F. de O. Falcão
Keyword(s):  
Wave Energy ◽  
Wave Theory ◽  
Maximum Efficiency ◽  
Energy Extraction ◽  
Oscillating Water Column ◽  
Regular Waves ◽  
Constant Depth ◽  
Energy Device ◽  
Chamber Length ◽  
Strongly Nonlinear

A two-dimensional analysis, based on linear surface-wave theory, is developed for an oscillating-water-column wave-energy device in water of arbitrary constant depth. The immersed part of the structure is assumed of shallow draught except for a submerged vertical reflecting wall. Both the cases of linear and nonlinear power take-off are considered. The results show that air compressibility can be important in practice, and its effects may in general be satisfactorily represented by linearization. The analysis indicates that using a turbine whose characteristic exhibits a phase difference between pressure and flow rate may be a method of strongly reducing the chamber length and turbine size with little change in the capability of energy extraction from regular waves. It was found in two examples of devices with strongly nonlinear power take-off that the maximum efficiency is only marginally inferior to what can be achieved in the linear case.

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