Investigations on 3D effects and correlation between wave height and lip submergence of an offshore stationary OWC wave energy converter

2017 ◽  
Vol 64 ◽  
pp. 203-216 ◽  
Author(s):  
Ahmed Elhanafi ◽  
Gregor Macfarlane ◽  
Alan Fleming ◽  
Zhi Leong
2021 ◽  
Vol 9 (3) ◽  
pp. 309
Author(s):  
James Allen ◽  
Gregorio Iglesias ◽  
Deborah Greaves ◽  
Jon Miles

The WaveCat is a moored Wave Energy Converter design which uses wave overtopping discharge into a variable v-shaped hull, to generate electricity through low head turbines. Physical model tests of WaveCat WEC were carried out to determine the device reflection, transmission, absorption and capture coefficients based on selected wave conditions. The model scale was 1:30, with hulls of 3 m in length, 0.4 m in height and a freeboard of 0.2 m. Wave gauges monitored the surface elevation at discrete points around the experimental area, and level sensors and flowmeters recorded the amount of water captured and released by the model. Random waves of significant wave height between 0.03 m and 0.12 m and peak wave periods of 0.91 s to 2.37 s at model scale were tested. The wedge angle of the device was set to 60°. A reflection analysis was carried out using a revised three probe method and spectral analysis of the surface elevation to determine the incident, reflected and transmitted energy. The results show that the reflection coefficient is highest (0.79) at low significant wave height and low peak wave period, the transmission coefficient is highest (0.98) at low significant wave height and high peak wave period, and absorption coefficient is highest (0.78) when significant wave height is high and peak wave period is low. The model also shows the highest Capture Width Ratio (0.015) at wavelengths on the order of model length. The results have particular implications for wave energy conversion prediction potential using this design of device.


2020 ◽  
Author(s):  
Iain Fairley ◽  
Matthew Lewis ◽  
Bryson Robertson ◽  
Mark Hemer ◽  
Ian Masters ◽  
...  

<p>Understanding and classification of the global wave energy resource is vital to facilitate wave energy converter technology development and global roll-out of this promising renewable energy technology. To date, many wave energy converters have been developed based on Northern European wave climates; these are not representative of wave climates worldwide and may not be the best for large scale energy extraction. Classification of resources will highlight alternative wave resource types that may prove fruitful for deployment of future technologies; equally it will enable existing technology to define regions worthy of site exploration. Therefore k-means clustering is used here to classify the global resource from a data-driven, device agnostic perspective.</p><p>Parameters relevant to energy extraction (significant wave height, peak wave period, extreme wave height, spectral and directional properties) were extracted from the ECMWF ERA5 reanalysis dataset and used to split the global resource into 6 classes. Only areas within 3 degrees of land (feasible energy transport to user) were considered. The 6 classes returned by the analysis consisted of: 1) low energy high variability areas in enclosed seas; 2) low energy moderate variability areas in semi-enclosed seas and sheltered ocean coasts; 3) moderate energy areas, largely on eastern oceanic coastlines and influenced by local storm activity; 4) moderate energy areas primarily influenced by long period swell and largely on western oceanic coastlines; 5) higher energy areas, with variable conditions, primarily in the northern hemisphere; 6) highest energy areas, primarily on the tips of continents in the southern hemisphere. Consideration of device power matrices show that existing devices only perform well in classes 5 and 6, despite these areas having limited global coverage, which suggests devices should be developed for lower energy classes.</p><p>To refine global roll-out planning for existing devices, based on a request from a wave energy converter developer, a second classification is currently being developed with two additional constraints on the areas tested. These constraints are excluding any areas with a mean wave power of less than 15 kW/m (an often-used value for the lower power limit for commercial viability) and a maintenance constraint whereby wave heights must drop below 3m for a minimum of 48hrs per month. These newer results will be presented at the annual assembly and contrasted with our more device agnostic classification.</p>


Author(s):  
D. Clabby ◽  
A. Henry ◽  
M. Folley ◽  
T. Whittaker

The power output from a wave energy converter is typically predicted using experimental and/or numerical modelling techniques. In order to yield meaningful results the relevant characteristics of the device, together with those of the wave climate must be modelled with sufficient accuracy. The wave climate is commonly described using a scatter table of sea states defined according to parameters related to wave height and period. These sea states are traditionally modelled with the spectral distribution of energy defined according to some empirical formulation. Since the response of most wave energy converters vary at different frequencies of excitation, their performance in a particular sea state may be expected to depend on the choice of spectral shape employed rather than simply the spectral parameters. Estimates of energy production may therefore be affected if the spectral distribution of wave energy at the deployment site is not well modelled. Furthermore, validation of the model may be affected by differences between the observed full scale spectral energy distribution and the spectrum used to model it. This paper investigates the sensitivity of the performance of a bottom hinged flap type wave energy converter to the spectral energy distribution of the incident waves. This is investigated experimentally using a 1:20 scale model of Aquamarine Power’s Oyster wave energy converter, a bottom hinged flap type device situated at the European Marine Energy Centre (EMEC) in approximately 13m water depth. The performance of the model is tested in sea states defined according to the same wave height and period parameters but adhering to different spectral energy distributions. The results of these tests show that power capture is reduced with increasing spectral bandwidth. This result is explored with consideration of the spectral response of the device in irregular wave conditions. The implications of this result are discussed in the context of validation of the model against particular prototype data sets and estimation of annual energy production.


2014 ◽  
Vol 507 ◽  
pp. 480-485
Author(s):  
Javier Aparisi ◽  
Jose González ◽  
Bernabé Hernandis

The development and exploitation of new sources of clean energy that do not depend on traditional sources based on the use of fossil fuels, is the focus of this research, which starts with the optimization of an invention capable of transforming a reciprocating rectilinear motion into continuous circular motion in a very efficient way, to be used in the development of a Wave Energy Converter (WEC), capable of operating with low wave height and taking advantage of the oscillating movement of the waves both when rising, and when lowering, unlike other similar devices that harness it only in one way.


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

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.


2020 ◽  
Vol 26 (3) ◽  
pp. 97-106
Author(s):  
OLAKUNLE KAYODE ◽  
TITUS OLUWASUJI AJEWOLE ◽  
OLUFEMI ADEBOLA KOYA

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.


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