Coupling Methodology for Modelling the Near-Field and Far-Field Effects of a Wave Energy Converter

Balitsky, Philip; Fernandez, Gael Verao; Stratigaki, Vicky; Troch, Peter

doi:10.1115/omae2017-61892

Cited by 9 publications

(26 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The WEC-WEC separation distances d x and d y are set to 40 m, which is the 2× the diameter of the heaving buoy WEC and the width of the OSWEC. The array configurations of both WEC types are staggered, an arrangement that was clearly shown to be power-maximizing in several numerical and experimental studies such as in [4,23,26,28,[39][40][41]. In this investigation the water depth is set at 30 m for the heaving buoy and 10.0 m for the OSWEC.…”

Section: Wec Array Layoutmentioning

confidence: 99%

“…B PTO,l represents an M × M diagonal matrix with the B PTO coefficients for each WEC on the diagonal. For the hydraulic PTO system, the equations equivalent to (23) and (26) are given in Equation 39:…”

Section: Power Output Calculation For An Array Of 5 Wecsmentioning

confidence: 99%

“…where P is the power output of the linear or hydraulic PTO WEC given by equations (Equations (10), (14), (23) and (26)) for the heaving cylindrical WEC or the OSWEC, respectively. The q value is a commonly used metric in wave energy literature to assess the strength of array effects, we find it used in [30,39,40,43], for example.…”

Section: Power Output Calculation For An Array Of 5 Wecsmentioning

confidence: 99%

“…The PTO model is coupled to the open-source wave-structure interaction solver NEMOH [24] using the perturbed wave field imparted by the motion of the WECs in WEC-Sim. Previously, a similar approach was presented in [25][26][27] for the case of a wave-structure interaction solver coupled to a wave propagation model using a basic linear PTO model. WEC-Sim has been used in modelling hydraulic PTOs in several recent studies [20,22].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Analyzing the Near-Field Effects and the Power Production of an Array of Heaving Cylindrical WECs and OSWECs Using a Coupled Hydrodynamic-PTO Model

et al. 2018

Self Cite

View full text Add to dashboard Cite

The Power Take-Off (PTO) system is the key component of a Wave Energy Converter (WEC) that distinguishes it from a simple floating body because the uptake of the energy by the PTO system modifies the wave field surrounding the WEC. Consequently, the choice of a proper PTO model of a WEC is a key factor in the accuracy of a numerical model that serves to validate the economic impact of a wave energy project. Simultaneously, the given numerical model needs to simulate many WEC units operating in close proximity in a WEC farm, as such conglomerations are seen by the wave energy industry as the path to economic viability. A balance must therefore be struck between an accurate PTO model and the numerical cost of running it for various WEC farm configurations to test the viability of any given WEC farm project. Because hydrodynamic interaction between the WECs in a farm modifies the incoming wave field, both the power output of a WEC farm and the surface elevations in the ‘near field’ area will be affected. For certain types of WECs, namely heaving cylindrical WECs, the PTO system strongly modifies the motion of the WECs. Consequently, the choice of a PTO system affects both the power production and the surface elevations in the ‘near field’ of a WEC farm. In this paper, we investigate the effect of a PTO system for a small wave farm that we term ‘WEC array’ of 5 WECs of two types: a heaving cylindrical WEC and an Oscillating Surge Wave Energy Converter (OSWEC). These WECs are positioned in a staggered array configuration designed to extract the maximum power from the incident waves. The PTO system is modelled in WEC-Sim, a purpose-built WEC dynamics simulator. The PTO system is coupled to the open-source wave structure interaction solver NEMOH to calculate the average wave field η in the ‘near-field’. Using a WEC-specific novel PTO system model, the effect of a hydraulic PTO system on the WEC array power production and the near-field is compared to that of a linear PTO system. Results are given for a series of regular wave conditions for a single WEC and subsequently extended to a 5-WEC array. We demonstrate the quantitative and qualitative differences in the power and the ‘near-field’ effects between a 5-heaving cylindrical WEC array and a 5-OSWEC array. Furthermore, we show that modeling a hydraulic PTO system as a linear PTO system in the case of a heaving cylindrical WEC leads to considerable inaccuracies in the calculation of average absorbed power, but not in the near-field surface elevations. Yet, in the case of an OSWEC, a hydraulic PTO system cannot be reduced to a linear PTO coefficient without introducing substantial inaccuracies into both the array power output and the near-field effects. We discuss the implications of our results compared to previous research on WEC arrays which used simplified linear coefficients as a proxy for PTO systems.

show abstract

Section: Wec Array Layoutmentioning

confidence: 99%

Section: Power Output Calculation For An Array Of 5 Wecsmentioning

confidence: 99%

Section: Power Output Calculation For An Array Of 5 Wecsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Analyzing the Near-Field Effects and the Power Production of an Array of Heaving Cylindrical WECs and OSWECs Using a Coupled Hydrodynamic-PTO Model

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…The superposition of the reflected, diffracted and radiated wave fields results in a perturbed wave field. The perturbed wave field close to the WECs of the farm caused both by WEC-WEC and wave-WEC interactions is often referred to in literature as the "'near field" effects while the propagation of this perturbed wave field at a larger distance from the WEC farm e.g., in the coastal zone, is referred to as the "far field" effects [9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

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

2019

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Wake effect assessment of a flap type wave energy converter farm under realistic environmental conditions by using a numerical coupling methodology

Tomey-Bozo

Babarit

Murphy

et al. 2019

Coastal Engineering

Self Cite

View full text Add to dashboard Cite

show abstract

Coupling Methodology for Modelling the Near-Field and Far-Field Effects of a Wave Energy Converter

Cited by 9 publications

References 0 publications

Analyzing the Near-Field Effects and the Power Production of an Array of Heaving Cylindrical WECs and OSWECs Using a Coupled Hydrodynamic-PTO Model

Analyzing the Near-Field Effects and the Power Production of an Array of Heaving Cylindrical WECs and OSWECs Using a Coupled Hydrodynamic-PTO Model

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

Wake effect assessment of a flap type wave energy converter farm under realistic environmental conditions by using a numerical coupling methodology

Contact Info

Product

Resources

About