Balitsky, P.

Stratigaki, V.

Troch, P.

Verao Fernandez, G.

Open Marine Archive

 9 
Analysis of the power output and the far-field effects of a 50-WEC 
farm using a novel coupling technique 
Balitsky Philip, Verao Fernandez Gael, Stratigaki Vasiliki and Troch Peter 
Department of Civil Engineering, Ghent University, Technologiepark 904, 9052 Zwijnaarde (Ghent), 
Belgium 
E-mail: Philip.Balitsky@UGent.be  
 
To reduce the likelihood of catastrophic effects of climate change, there is an urgent need to 
decarbonize of the world electricity supply. Consequently, all viable renewable energy sources need 
to be investigated for their potential to contribute to the electrical power mix.  Ocean waves provide 
an exciting potential for clean, reliable energy, yet this source is still too costly to be commercially 
exploited at present.  
 
As has recently occurred with offshore wind, a significant cost reduction of electricity from waves will 
come from aggregating large numbers of wave energy converters (WECs) in farms.  Given the practical 
constraints on the size of individual WECs derived from first principles, it is likely that an electrical 
node comparable to the size of a large offshore wind turbine will be provided by an array or cluster 
of closely spaced WECs. Therefore, the most likely scenario for commercial WEC farms will be one of 
multi-array farms consisting of sparsely spaced WEC arrays of densely packed WECs.  However, unlike 
single WEC turbines, the power output of the arrays and the WEC farms will change depending on the 
layout of both the WECs and the WEC arrays because of hydrodynamic interactions in these arrays. 
 
One of the problems in studying the impact of large WEC farms is choosing an appropriate level of 
granularity in the numerical simulation of the hydrodynamic effects.  Resolving too many equations 
leads to a loss in computational efficiency while fast approaches such as spectral models do not 
provide a sufficient level of detail and do not resolve the phase relationships that lead to large 
fluctuations in power output. 
 
Our novel solution is to couple a BEM code in the areas immediately surrounding the WECs and 
propagate the perturbed waves to the surrounding farm area and beyond a wave propagation 
model [1].  The BEM solver utilized in this study is NEMOH [2], while the wave propagation model is 
the mild-slope equation package MILDwave [3].  A novel 2
nd
 order precision iterative technique is used 
to calculate the wave field for a wave farm composed of several arrays [4]. 
 
In this presentation, we demonstrate the results of a numerical study which traces the effect of various 
layouts to the power output of a wave farm composed of several clustered arrays.  The study utilizes 
a staggered configuration of shallow draft heaving buoys to mimic a realistic clustered WEC array.  The 
effect of varying array separation distances and wave incidence angles are demonstrated for many 
regular and irregular wave conditions. 
 
The effects of changing the incident wave conditions and the layout on the WEC farm are explained 
in a qualitative and quantitative way.  The former via demonstrating the perturbed wave field in the 
WEC farm and the latter via a table and plot of the power output for the various configurations 
considered.  
 
Acknowledgement 
 
This research is being supported by the Research Foundation Flanders (FWO), Belgium - Contract 
Number of research project: 3G029114. 
 
References 
 
[1] P. Balitsky, G. Verao Fernandez, V. Stratigaki y P. Troch, «Coupling methodology for modelling 
the near-field and far-field effects of a Wave Energy Converter,» de Proceedings of the ASME 36th 
International Conference on Ocean, Offshore and Arctic Engineering (OMAE2017), Trondheim, 
Norway, 2017. 
[2] A. Babarit y G. Delhommeau, «Theoretical and numerical aspects of the open source BEM solver 
NEMOH,» Proceedings of the 11th European Wave and Tidal Energy Conference. Nantes, France, 
pp. 1-12, 2015. 
 10 
[3] P. Troch y V. Stratigaki, «Phase-Resolving Wave Propagation Array Model,» de Numerical 
Modelling of Wave Energy Converters, 2016, pp. 191-216. 
[4] P. Balitsky, G. Verao Fernandez, V. Stratigaki y P. Troch, «Assessing the Impact on Power 
Production of WEC array separation distance in a wave farm using one-way coupling of a BEM 
solver and a wave propagation model,» de Proceeding of the 10th European Wave and Tidal 
Energy Conference (EWTEC 2017), Cork, Ireland, 2017. 
 
Keywords: WEC array; WEC farm; wave farm; power output; farm effects; array effects; hydrodynamic 
interaction; wave propagation model; coupling; mild-slope equations; Boundary Element Method; 
numerical modelling  


Analysis of the power output and the far-field effects of a 50-WEC farm using a novel coupling technique

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Analysis of the power output and the far-field effects of a 50-WEC farm using a novel coupling technique

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