Effects of inflow turbulence intensity and turbine arrangements on the power generation efficiency of large wind farms

Wu, Yu Ting; Lin, Chuan-Yao; Chang, Tsang‐Jung

doi:10.1002/we.2507

Cited by 28 publications

(14 citation statements)

References 39 publications

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“…For turbulent inflow cases, the velocity deficit recovers faster than the uniform case due to the inflow turbulence, which is in agreement with previous studies [16,47]. In our test cases, the time-averaged streamwise velocity, TKE, and primary Reynold's stresses computed by the AD model reasonably agree with the AS model starting from x = 7D.…”

Section: Discussionsupporting

confidence: 91%

“…To better take into account the geometrical effects of wind turbine blades, the Actuator Surface (AS) method has been proposed, which models a blade as a two dimensional surface with zero thickness [11,12]. Because of its simplicity and computational efficiency, the AD has been widely used in turbine wake simulations especially in farm-scale simulations [13][14][15][16]. The capability of the actuator disk model in predicting turbine wakes, especially in the far wake region, has been widely validated in the literature [14,17,18].…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Actuator Disk Model Relative to Actuator Surface Model for Predicting Utility-Scale Wind Turbine Wakes

Yang

2020

Energies

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The Actuator Disk (AD) model is widely used in Large-Eddy Simulations (LES) to simulate wind turbine wakes because of its computing efficiency. The capability of the AD model in predicting time-average quantities of wind tunnel-scale turbines has been assessed extensively in the literature. However, its capability in predicting wakes of utility-scale wind turbines especially for the coherent flow structures is not clear yet. In this work, we take the time-averaged statistics and Dynamic Mode Decomposition (DMD) modes computed from a well-validated Actuator Surface (AS) model as references to evaluate the capability of the AD model in predicting the wake of a 2.5 MW utility-scale wind turbine for uniform inflow and fully developed turbulent inflow conditions. For the uniform inflow cases, the predictions from the AD model are significantly different from those from the AS model for the time-averaged velocity, and the turbulence kinetic energy until nine rotor diameters (D) downstream of the turbine. For the turbulent inflow cases, on the other hand, the differences in the time-averaged quantities predicted by the AS and AD models are not significant especially at far wake locations. As for DMD modes, significant differences are observed in terms of dominant frequencies and DMD patterns for both inflows. Moreover, the effects of incoming large eddies, bluff body shear layer instability, and hub vortexes on the coherent flow structures are discussed in this paper.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Evaluation of Actuator Disk Model Relative to Actuator Surface Model for Predicting Utility-Scale Wind Turbine Wakes

Yang

2020

Energies

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“…The smaller interturbine spacing allows less room for the turbulent kinetic energy from the wakes to dissipate. Consequently, the turbulence intensity is higher in aligned wind farms than in staggered wind farms (Wu, Lin, & Chang, 2020; Wu & Porté-Agel, 2013, 2017). Figures 6( c ) and 6( f ) show that the vertical velocity averaged over the wind farm width at hub height is zero in front of the induction zone of the upstream wind farm, which starts at , before the flow is deflected over the wind farm (Wu & Porté-Agel, 2017).…”

Section: Resultsmentioning

confidence: 98%

Impact of wind farm wakes on flow structures in and around downstream wind farms

Stieren

Stevens

2022

Flow

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We performed large-eddy simulations in a neutral atmospheric boundary layer to study the interaction between two identical wind farms with 72 turbines each. We demonstrate that the wind farm wake created by the upstream farm affects the entire flow in and around the downstream farm. The vertical entrainment fluxes above the downstream wind farm are strengthened, resulting in a faster wind farm wake recovery behind the downstream farm. These findings illustrate that interaction between extended wind farms affects flow structures beyond the wind farm scale. Furthermore, we demonstrate that wind farm wakes can reduce the power production of turbines throughout the downstream wind farms. We additionally observe that a staggered wind farm extracts more energy from the flow and thus creates a stronger wind farm wake than an aligned wind farm.

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“…This result comparison between C3 and C5 demonstrates that a turbine operating at a faster blade rotating speed can generate a larger power output and extract less momentum from the inflow to produce a slightly weaker wake. This kind of control strategy can be applied to raise the power generation of the downstream turbines as well as the overall power productivity in large wind farms with different inflow conditions and placement configurations [26,27]. Acknowledgments: Computing resources were provided by the Taiwan National Center for High-performance Computing (NCHC).…”

Section: Discussionmentioning

confidence: 99%

An Experimental Investigation of Wake Characteristics and Power Generation Efficiency of a Small Wind Turbine under Different Tip Speed Ratios

Lin

Hsu

2020

Energies

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We carried out a wind tunnel experiment to examine the power generation efficiency of a stand-alone miniature wind turbine and its wake characteristics at different tip speed ratios (TSRs) under the same mean inflow velocity. Resistors in the electrical circuit were adjusted to control the TSRs to 0.9, 1.5, 3.0, 4.1, 5.2, and 5.9. The currents were measured to estimate the turbine power outputs versus the TSRs and then establish the actual power generation coefficient Cp distribution. To calculate the mechanical power coefficient, a new estimation method of the mechanical torque constant is proposed. A reverse calibration on the blade rotation speed was performed with given electrical voltages and currents that are used to estimate the mechanical power coefficient Cp, mech. In the experiment, the maximum Cp,mech was approximately 0.358 (corresponding to the maximum Cp of 0.212) at the TSR of 4.1. Significant findings indicate that the turbine at the TSR of 5.2 produces a smaller torque but a larger power output compared with that at the TSR of 3.0. This comparison further displays that the turbine at the TSR of 5.2, even with larger power output, still produces a turbine wake that has smaller velocity deficits and smaller turbulence intensity than that at the TSR of 3.0. This behavior demonstrates the significance of the blade-rotation control (i.e., pitch regulation) system to the turbine operation in a large wind farm for raising the overall farm power productivity.

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Effects of inflow turbulence intensity and turbine arrangements on the power generation efficiency of large wind farms

Cited by 28 publications

References 39 publications

Evaluation of Actuator Disk Model Relative to Actuator Surface Model for Predicting Utility-Scale Wind Turbine Wakes

Evaluation of Actuator Disk Model Relative to Actuator Surface Model for Predicting Utility-Scale Wind Turbine Wakes

Impact of wind farm wakes on flow structures in and around downstream wind farms

An Experimental Investigation of Wake Characteristics and Power Generation Efficiency of a Small Wind Turbine under Different Tip Speed Ratios

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