A high-fidelity wave-to-wire simulation platform for wave energy converters: Coupled numerical wave tank and power take-off models

Peñalba, Markel; Davidson, Josh; Windt, Christian; Ringwood, John V.

doi:10.1016/j.apenergy.2018.06.008

Cited by 67 publications

(49 citation statements)

References 56 publications

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“…Using fully nonlinear Reynolds Averaged Navier-Stokes (RANS) simulations with the volume of fluid (VOF) method for the air-water interface has emerged as the most common method of choice in CFD for wave energy applications [3]. Many studies of point-absorbing WECs (PAWECs) have been presented over the last few years, e.g., [4][5][6][7][8][9][10], which has already spurred some reviews of the nonlinear numerical approaches to WEC design [3,[11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Palm

Eskilsson

Bergdahl

et al. 2018

JMSE

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This paper analyses the nonlinear forces on a moored point-absorbing wave energy converter (WEC) in resonance at prototype scale (1:1) and at model scale (1:16). Three simulation types were used: Reynolds Averaged Navier-Stokes (RANS), Euler and the linear radiation-diffraction method (linear). Results show that when the wave steepness is doubled, the response reduction is: (i) 3% due to the nonlinear mooring response and the Froude-Krylov force; (ii) 1-4% due to viscous forces; and (iii) 18-19% due to induced drag and non-linear added mass and radiation forces. The effect of the induced drag is shown to be largely scale-independent. It is caused by local pressure variations due to vortex generation below the body, which reduce the total pressure force on the hull. Euler simulations are shown to be scale-independent and the scale effects of the WEC are limited by the purely viscous contribution (1-4%) for the two waves studied. We recommend that experimental model scale test campaigns of WECs should be accompanied by RANS simulations, and the analysis complemented by scale-independent Euler simulations to quantify the scale-dependent part of the nonlinear effects.

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Section: Introductionmentioning

confidence: 99%

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Palm

Eskilsson

Bergdahl

et al. 2018

JMSE

View full text Add to dashboard Cite

show abstract

“…Concurrently, due to substantial improvements in hydrodynamic modelling software, there has been a jump in the number of numerical investigations that have modelled single WECs [23][24][25][26] and small farms of WECs [27,28] with fully nonlinear hydrodynamics. However, as mentioned in Penalba et al [29], for the case of heaving cylindrical WECs and in Schmitt et al [21] for OSWECs, the errors due to a simplified PTO model can override any improvements imparted by more accurate hydrodynamic models. A particular concern with many existing PTO modelling approaches is that the most common PTO system type developed for commercial WEC prototypes, a hydraulic PTO system, is inherently nonlinear [30][31][32].…”

Section: Introductionmentioning

confidence: 97%

“…A particular concern with many existing PTO modelling approaches is that the most common PTO system type developed for commercial WEC prototypes, a hydraulic PTO system, is inherently nonlinear [30][31][32]. A few recent studies, notably [29,30,[32][33][34][35][36], have achieved realistic hydraulic PTO models with nonlinear dynamics. However, these investigations were limited in their scope to single WECs and not WEC arrays.…”

Section: Introductionmentioning

confidence: 99%

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

Balitsky

Quartier

Stratigaki

et al. 2019

Water

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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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“…Concurrently, due to step improvements in hydrodynamic modelling software, there has been a jump in the number of numerical investigations that have modelled single WECs [10][11][12][13] and small farms of WECs [14,15] with fully non-linear hydrodynamics. Yet, as pointed out in Penalba et al [16] for the case of heaving point absorbers and in [8] for OSWECs, the errors due to a simplified PTO model can override any improvements made by more accurate hydrodynamic models. A particular concern with many existing PTO modelling efforts is that the most common PTO system type developed for commercial WEC prototypes, a hydraulic PTO system, is inherently non-linear [17,18].…”

Section: Introductionmentioning

confidence: 99%

“…A particular concern with many existing PTO modelling efforts is that the most common PTO system type developed for commercial WEC prototypes, a hydraulic PTO system, is inherently non-linear [17,18]. A few recent studies, notably [16][17][18][19][20][21][22] have implemented realistic hydraulic PTO models with non-linear dynamics. However, these studies were limited in their scope to single WECs and not WEC farms, furthermore, many of the models quite complicated in their implementation.…”

Section: Introductionmentioning

confidence: 99%

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

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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.

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A high-fidelity wave-to-wire simulation platform for wave energy converters: Coupled numerical wave tank and power take-off models

Cited by 67 publications

References 56 publications

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

Assessment of Scale Effects, Viscous Forces and Induced Drag on a Point-Absorbing Wave Energy Converter by CFD Simulations

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

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