Assessment of the Power Output of a Two-Array Clustered WEC Farm Using a BEM Solver Coupling and a Wave-Propagation Model

One of the key challenges in designing a Wave Energy Converter (WEC) farm is geometrical layout, as WECs hydrodynamically interact with one another. WEC positioning impacts both the power output of a given wave-energy project and any potential effects on the surrounding areas. The WEC farm developer must seek to optimize WEC positioning to maximize power output while minimizing capital cost and any potential deleterious effects on the surrounding area. A number of recent studies have shown that a potential solution is placing WECs in dense arrays of several WECs with space between individual arrays for navigation. This innovative arrangement can also be used to reduce mooring and cabling costs. In this paper, we apply a novel one-way coupling method between the NEMOH BEM model and the MILDwave wave-propagation model to investigate the influence of WEC array separation distance on the power output and the surrounding wave field between two densely packed WEC arrays in a farm. An iterative method of applying the presented one-way coupling to interacting WEC arrays is used to compute the wave field in a complete WEC farm and to calculate its power output. The notion of WEC array ‘independence’ in a farm from a hydrodynamic point of view is discussed. The farm is modeled for regular and irregular waves for a number of wave periods, wave incidence angles, and various WEC array separation distances. We found strong dependency of the power output on the wave period and the wave incidence angle for regular waves at short WEC array–array separation distances. For irregular wave operational conditions, a large majority of WEC array configurations within a WEC farm were found to be hydrodynamically ‘independent’.

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Introducing Wave Regeneration by Wind in a Mild-Slope Wave Propagation Model MILDwave to Investigate the Wake Effects in the Lee of a Farm of Wave Energy Converters

Volume 5: Ocean Space Utilization; Ocean Renewable Energy ◽

10.1115/omae2011-49347 ◽

2011 ◽

Cited By ~ 2

Author(s):

Vasiliki Stratigaki ◽

Peter Troch ◽

Leen Baelus ◽

Yannick Keppens

Keyword(s):

Wave Propagation ◽

Wave Energy ◽

Propagation Model ◽

Wave Power ◽

Single Wave ◽

Wave Energy Converters ◽

Wake Effects ◽

Wave Regeneration ◽

Wave Propagation Model ◽

Energy Converters

The increasing energy demand, the need to reduce greenhouse gas emissions and the shrinking reserves of fossil fuels have all enhanced the interest in sustainable and renewable energy sources, including wave energy. Many concepts for wave power conversion have been invented. In order to extract a considerable amount of wave power, single Wave Energy Converters (abbreviated as WECs) will have to be arranged in arrays or ‘farms’ using a particular geometrical layout, comprising large numbers of devices. As a result of the interaction between the WECs within a farm, the overall power absorption is affected. In general, the incident waves are partly reflected, transmitted and absorbed by a single WEC. Also, the wave height behind a large farm of WECs is reduced and this reduction may influence neighbouring farms, other users in the sea or even the coastline (wake effects of a WEC farm). The numerical wave propagation model MILDwave has been recently used to study wake effects and energy absorption of farms of WECs, though without taking into account wave regeneration by wind in the lee of the WEC-farm which can be significant in large distances downwave the WECs. In this paper, the implementation of wave growth due to wind in the hyperbolic mild-slope equations of the wave propagation model, MILDwave is described. Several formulations for the energy input from wind found in literature are considered and implemented. The performance of these formulations in MILDwave is investigated and validated. The modified model MILDwave is then applied for the investigation of the influence of the wind on the wakes in the lee of a farm of wave energy converters.

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Irregular Wave Validation of a Coupling Methodology for Numerical Modelling of Near and Far Field Effects of Wave Energy Converter Arrays

Energies ◽

10.3390/en12030538 ◽

2019 ◽

Vol 12 (3) ◽

pp. 538 ◽

Cited By ~ 7

Author(s):

Gael Fernández ◽

Vasiliki Stratigaki ◽

Peter Troch

Keyword(s):

Experimental Data ◽

Wave Field ◽

Wave Energy ◽

Near Field ◽

Coupled Model ◽

Propagation Model ◽

Irregular Waves ◽

Far Field ◽

Engineering Research ◽

Field Effects

Between the Wave Energy Converters (WECs) of a farm, hydrodynamic interactions occur and have an impact on the surrounding wave field, both close to the WECs (“near field” effects) and at large distances from their location (“far field” effects). To simulate this “far field” impact in a fast and accurate way, a generic coupling methodology between hydrodynamic models has been developed by the Coastal Engineering Research Group of Ghent University in Belgium. This coupling methodology has been widely used for regular waves. However, it has not been developed yet for realistic irregular sea states. The objective of this paper is to present a validation of the novel coupling methodology for the test case of irregular waves, which is demonstrated here for coupling between the mild slope wave propagation model, MILDwave, and the ‘Boundary Element Method’-based wave–structure interaction solver, NEMOH. MILDwave is used to model WEC farm “far field” effects, while NEMOH is used to model “near field” effects. The results of the MILDwave-NEMOH coupled model are validated against numerical results from NEMOH, and against the WECwakes experimental data for a single WEC, and for WEC arrays of five and nine WECs. Root Mean Square Error (RMSE) between disturbance coefficient (Kd) values in the entire numerical domain ( R M S E K d , D ) are used for evaluating the performed validation. The R M S E K d , D between results from the MILDwave-NEMOH coupled model and NEMOH is lower than 2.0% for the performed test cases, and between the MILDwave-NEMOH coupled model and the WECwakes experimental data R M S E K d , D remains below 10%. Consequently, the efficiency is demonstrated of the coupling methodology validated here which is used to simulate WEC farm impact on the wave field under the action of irregular waves.

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Analysing the Near-Field Effects and the Power Production of Near-Shore WEC Array Using a New Wave-to-Wire Model

Water ◽

10.3390/w11061137 ◽

2019 ◽

Vol 11 (6) ◽

pp. 1137

Author(s):

Philip Balitsky ◽

Nicolas Quartier ◽

Vasiliki Stratigaki ◽

Gael Verao Fernandez ◽

Panagiotis Vasarmidis ◽

...

Keyword(s):

Wave Energy ◽

Near Field ◽

Wave Structure ◽

Wave Climate ◽

Separation Distance ◽

Propagation Model ◽

Irregular Waves ◽

Field Effects ◽

Wave Energy Converters ◽

Near Shore

In this study, a series of modules is integrated into a wave-to-wire (W2W) model that links a Boundary Element Method (BEM) solver to a Wave Energy Converter (WEC) motion solver which are in turn coupled to a wave propagation model. The hydrodynamics of the WECs are resolved in the wave structure interaction solver NEMOH, the Power Take-off (PTO) is simulated in the WEC simulation tool WEC-Sim, and the resulting perturbed wave field is coupled to the mild-slope propagation model MILDwave. The W2W model is run for verified for a realistic wave energy project consisting of a WEC farm composed of 10 5-WEC arrays of Oscillating Surging Wave Energy Converters (OSWECs). The investigated WEC farm is modelled for a real wave climate and a sloping bathymetry based on a proposed OSWEC array project off the coast of Bretagne, France. Each WEC array is arranged in a power-maximizing 2-row configuration that also minimizes the inter-array separation distance d x and d y and the arrays are located in a staggered energy maximizing configuration that also decreases the along-shore WEC farm extent. The WEC farm power output and the near and far-field effects are simulated for irregular waves with various significant wave heights wave peak periods and mean wave incidence directions β based on the modelled site wave climatology. The PTO system of each WEC in each farm is modelled as a closed-circuit hydraulic PTO system optimized for each set of incident wave conditions, mimicking the proposed site technology, namely the WaveRoller® OSWEC developed by AW Energy Ltd. The investigation in this study provides a proof of concept of the proposed W2W model in investigating potential commercial WEC projects.

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The coastal refraction-diffraction wave propagation model

Vietnam Journal of Mechanics ◽

10.15625/0866-7136/10140 ◽

1995 ◽

Vol 17 (4) ◽

pp. 6-12

Author(s):

Nguyen Tien Dat ◽

Dinh Van Manh ◽

Nguyen Minh Son

Keyword(s):

Wave Propagation ◽

Field Data ◽

Surf Zone ◽

Propagation Model ◽

Wave Transformation ◽

Diffraction Effect ◽

Linear Wave ◽

Diffraction Wave ◽

Linear Wave Propagation ◽

Wave Propagation Model

A mathematical model on linear wave propagation toward shore is chosen and corresponding software is built. The wave transformation outside and inside the surf zone is considered including the diffraction effect. The model is tested by laboratory and field data and gave reasonables results.

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