scholarly journals Distribution of mean kinetic energy around an isolated wind turbine and a characteristic wind turbine of a very large wind farm

2016 ◽  
Vol 1 (7) ◽  
Author(s):  
Gerard Cortina ◽  
Marc Calaf ◽  
Raúl Bayoán Cal
Keyword(s):  
Kinetic Energy ◽  
Wind Turbine ◽  
Wind Farm ◽  
Large Wind ◽  
Mean Kinetic Energy

scholarly journals Wind Turbine Performance in Very Large Wind Farms: Betz Analysis Revisited

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1078 ◽  
Author(s):  
Jacob R. West ◽  
Sanjiva K. Lele
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Wind Turbine ◽  
Wind Farm ◽  
Wind Farms ◽  
Mean Flow ◽  
Thrust Coefficient ◽  
Turbine Performance ◽  
Trade Offs ◽  
Mean Kinetic Energy

The theoretical limit for wind turbine performance, the so-called Betz limit, arises from an inviscid, irrotational analysis of the streamtube around an actuator disk. In a wind farm in the atmospheric boundary layer, the physics are considerably more complex, encompassing shear, turbulent transport, and wakes from other turbines. In this study, the mean flow streamtube around a wind turbine in a wind farm is investigated with large eddy simulations of a periodic array of actuator disks in half-channel flow at a range of turbine thrust coefficients. Momentum and mean kinetic energy budgets are presented, connecting the energy budget for an individual turbine to the wind farm performance as a whole. It is noted that boundary layer turbulence plays a key role in wake recovery and energy conversion when considering the entire wind farm. The wind farm power coefficient is maximized when the work done by Reynolds stress on the periphery of the streamtube is maximized, although some mean kinetic energy is also dissipated into turbulence. This results in an optimal value of thrust coefficient lower than the traditional Betz result. The simulation results are used to evaluate Nishino’s model of infinite wind farms, and design trade-offs described by it are presented.

scholarly journals Quantification of Preferential Contribution of Reynolds Shear Stresses and Flux of Mean Kinetic Energy Via Conditional Sampling in a Wind Turbine Array

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Hawwa Falih Kadum ◽  
Devin Knowles ◽  
Raúl Bayoán Cal
Keyword(s):  
Shear Stress ◽  
Kinetic Energy ◽  
Wind Turbine ◽  
Momentum Flux ◽  
Wind Farm ◽  
Reynolds Shear Stress ◽  
Stress Component ◽  
Wake Flow ◽  
Shear Stresses ◽  
Balanced Distribution

Conditional statistics are employed in analyzing wake recovery and Reynolds shear stress (RSS) and flux directional out of plane component preference. Examination of vertical kinetic energy entrainment through describing and quantifying the aforementioned quantities has implications on wind farm spacing, design, and power production, and also on detecting loading variation due to turbulence. Stereographic particle image velocimetry measurements of incoming and wake flow fields are taken for a 3 × 4 model wind turbine array in a scaled wind tunnel experiment. Reynolds shear stress component is influenced by ⟨uv⟩ component, whereas ⟨vw⟩ is more influenced by streamwise advection of the flow; u, v, and w being streamwise, vertical, and spanwise velocity fluctuations, respectively. Relative comparison between sweep and ejection events, ΔS⟨uiuj⟩, shows the role of streamwise advection of momentum on RSS values and direction. It also shows their tendency to an overall balanced distribution. ⟨uw⟩ intensities are associated with ejection elevated regions in the inflow, yet in the wake, ⟨uw⟩ is linked with sweep dominance regions. Downward momentum flux occupies the region between hub height and top tip. Sweep events contribution to downward momentum flux is marginally greater than ejection events'. When integrated over the swept area, sweeps contribute 55% of the net downward kinetic energy flux and 45% is the ejection events contribution. Sweep dominance is related to momentum deficit as its value in near wake elevates 30% compared to inflow. Understanding these quantities can lead to improved closure models.

scholarly journals Aerodynamic Analysis of Coning Effects on the DTU 10 MW Wind Turbine Rotor

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5753 ◽  
Author(s):  
Zhenye Sun ◽  
Wei Jun Zhu ◽  
Wen Zhong Shen ◽  
Wei Zhong ◽  
Jiufa Cao ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Wind Farm ◽  
Cone Angle ◽  
Turbine Rotor ◽  
Tip Vortex ◽  
Bending Moments ◽  
Wind Farm Design ◽  
Blade Section ◽  
Large Wind ◽  
Wind Turbine Rotor

The size of wind turbine rotors is still rapidly increasing, though many technical challenges emerge. Novel rotor designs emerge to satisfy this up-scale trend, such as downwind load-aligned concepts, which orients the loads along the blade spanwise to greatly decrease the bending moments at the root. As the studies on the aerodynamics of these rotor concepts using 3D body-fitted mesh are very limited, this paper establishes different cone configurations based on the DTU 10 MW reference rotor and conducts a series of simulations. It is found that the cone angle and the distance from the blade section to the tip vortex are two deterministic factors on conning. Upwind rotors have larger power output, less thrust, smaller wake deficit, and smaller influencing area than downwind rotors of the same size, which provides superior aerodynamic priority and benefits wind farm design. The largest upwind cone angle of 14.03°, among the cases studied, leads to the highest torque to thrust ratio which is 3.63% higher than the baseline rotor. The downwind load-aligned rotor, designed to reduce the blade root bending moments at large wind speed, performs worse at the present simulation conditions than an upwind rotor of the same size.

Load Measurement Method of the MW Class Wind Turbine

2013 ◽  
Vol 333-335 ◽  
pp. 146-151 ◽  
Author(s):  
De Yi Fu ◽  
Bo Jiao ◽  
Yang Xue ◽  
Shi Yao Qin
Keyword(s):  
Fatigue Strength ◽  
Life Span ◽  
Wind Turbine ◽  
Measurement Method ◽  
Wind Farm ◽  
Structural Response ◽  
Load Measurement ◽  
Wind Turbine Tower ◽  
Measurement Results ◽  
Large Wind

In recent years, wind turbine tower buckling and blade broken often happened. Large wind turbine load and insufficient fatigue strength should be the main reasons. To prevent this case, load measurement of the wind turbine is necessary. The wind turbine load measurement is one of the type tests of wind turbine. The load of the wind turbine structure components will strongly affect the safety and life span of the wind turbine. The wind turbine load measurement can help the wind turbine manufacturer and wind farm operator to know the structural response of the wind turbine components with different load cases. According to the IEC 61400-13 standard, a method of the wind turbine load measurement is introduced in this article. Meanwhile, the measurement results are given in this article. The results indicate that the accuracy of this measurement method can fulfill the requirements of the related standards.

scholarly journals Quantifying the Impact of Wind Turbine Wakes on Power Output at Offshore Wind Farms

2010 ◽  
Vol 27 (8) ◽  
pp. 1302-1317 ◽  
Author(s):  
R. J. Barthelmie ◽  
S. C. Pryor ◽  
S. T. Frandsen ◽  
K. S. Hansen ◽  
J. G. Schepers ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Power Output ◽  
Wind Farm ◽  
Wind Farms ◽  
Offshore Wind ◽  
Power Losses ◽  
Offshore Wind Farms ◽  
The Impact ◽  
Mean Square Errors ◽  
Large Wind

Abstract There is an urgent need to develop and optimize tools for designing large wind farm arrays for deployment offshore. This research is focused on improving the understanding of, and modeling of, wind turbine wakes in order to make more accurate power output predictions for large offshore wind farms. Detailed data ensembles of power losses due to wakes at the large wind farms at Nysted and Horns Rev are presented and analyzed. Differences in turbine spacing (10.5 versus 7 rotor diameters) are not differentiable in wake-related power losses from the two wind farms. This is partly due to the high variability in the data despite careful data screening. A number of ensemble averages are simulated with a range of wind farm and computational fluid dynamics models and compared to observed wake losses. All models were able to capture wake width to some degree, and some models also captured the decrease of power output moving through the wind farm. Root-mean-square errors indicate a generally better model performance for higher wind speeds (10 rather than 6 m s−1) and for direct down the row flow than for oblique angles. Despite this progress, wake modeling of large wind farms is still subject to an unacceptably high degree of uncertainty.

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