Changes in wind turbine power characteristics and annual energy production due to atmospheric stability, turbulence intensity, and wind shear

Energy ◽  
2021 ◽  
Vol 214 ◽  
pp. 119051
Author(s):  
Dae-Young Kim ◽  
Yeon-Hee Kim ◽  
Bum-Suk Kim
Keyword(s):  
Wind Turbine ◽  
Turbulence Intensity ◽  
Wind Shear ◽  
Energy Production ◽  
Atmospheric Stability ◽  
Power Characteristics

scholarly journals The Influence of Tilt Angle on the Aerodynamic Performance of a Wind Turbine

2020 ◽  
Vol 10 (15) ◽  
pp. 5380
Author(s):  
Qiang Wang ◽  
Kangping Liao ◽  
Qingwei Ma
Keyword(s):  
Wind Turbine ◽  
Turbulence Intensity ◽  
Tilt Angle ◽  
Wind Shear ◽  
Cfd Simulation ◽  
Aerodynamic Performance ◽  
Tip Vortices ◽  
Sliding Mesh ◽  
Blade Section ◽  
Lift And Drag

Aerodynamic performance of a wind turbine at different tilt angles was studied based on the commercial CFD software STAR-CCM+. Tilt angles of 0, 4, 8 and 12° were investigated based on uniform wind speed and wind shear. In CFD simulation, the rotating motion of blade was based on a sliding mesh. The thrust, power, lift and drag of the blade section airfoil at different tilt angles have been widely investigated herein. Meanwhile, the tip vortices and velocity profiles at different tilt angles were physically observed. In addition, the influence of the wind shear exponents and the expected value of turbulence intensity on the aerodynamic performance of the wind turbine is also further discussed. The results indicate that the change in tilt angle changes the angle of attack of the airfoil section of the wind turbine blade, which affects the thrust and power of the wind turbine. The aerodynamic performance of the wind turbine is better when the tilt angle is about 4°. Wind shear will cause the thrust and power of the wind turbine to decrease, and the effect of the wind shear exponents on the aerodynamic performance of the wind turbine is significantly greater than the expected effect of the turbulence intensity. The main purpose of the paper was to study the effect of tilt angle on the aerodynamic performance of a fixed wind turbine.

scholarly journals Volumetric Lidar Scanning of Wind Turbine Wakes under Convective and Neutral Atmospheric Stability Regimes

2014 ◽  
Vol 31 (10) ◽  
pp. 2035-2048 ◽  
Author(s):  
Giacomo Valerio Iungo ◽  
Fernando Porté-Agel
Keyword(s):  
Thermal Stability ◽  
Wind Turbine ◽  
Wind Power ◽  
Wind Velocity ◽  
Turbulence Intensity ◽  
Atmospheric Stability ◽  
Power Harvesting ◽  
Turbine Wake ◽  
Wind Turbine Wake

Abstract Optimization of a wind farm’s layout is a strategic task to reduce wake effects on downstream turbines, thus maximizing wind power harvesting. However, downstream evolution and recovery of each wind turbine wake are strongly affected by the characteristics of the incoming atmospheric boundary layer (ABL) flow, such as the vertical profiles of the mean wind velocity and the turbulence intensity, which are in turn affected by the ABL thermal stability. Therefore, the characterization of the variability of wind turbine wakes under different ABL stability regimes becomes fundamental to better predict wind power harvesting and to improve wind farm efficiency. To this aim, wind velocity measurements of the wake produced by a 2-MW Enercon E-70 wind turbine were performed with three scanning Doppler wind lidars. One lidar was devoted to the characterization of the incoming wind—in particular, wind velocity, shear, and turbulence intensity at the height of the rotor disc. The other two lidars performed volumetric scans of the wind turbine wake under different atmospheric conditions. Through the evaluation of the minimum wake velocity deficit as a function of the downstream distance, it is shown that the ABL stability regime has a significant effect on the wake evolution; in particular, the wake recovers faster under convective conditions. This result suggests that atmospheric inflow conditions, and particularly thermal stability, should be considered for improved wake models and predictions of wind power harvesting.

scholarly journals Determining an Appropriate Parameter of Analytical Wake Models for Energy Capture and Layout Optimization on Wind Farms

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 739 ◽  
Author(s):  
Kyoungboo Yang
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Turbulence Intensity ◽  
Energy Production ◽  
Wind Farm ◽  
Wind Farms ◽  
Gaussian Models ◽  
Advantages And Disadvantages ◽  
Power Deficit ◽  
Wake Model

The wake of a wind turbine is a crucial factor that decreases the output of downstream wind turbines and causes unsteady loading. Various wake models have been developed to understand it, ranging from simple ones to elaborate models that require long calculation times. However, selecting an appropriate wake model is difficult because each model has its advantages and disadvantages as well as distinct characteristics. Furthermore, determining the parameters of a given wake model is crucial because this affects the calculation results. In this study, a method was introduced of using the turbulence intensity, which can be measured onsite, to objectively define parameters that were previously set according to the subjective judgement of a wind farm designer or general recommended values. To reflect the environmental effects around a site, the turbulence intensity in each direction of the wind farm was considered for four types of analytical wake models: the Jensen, Frandsen, Larsen, and Jensen–Gaussian models. The prediction performances of the wake models for the power deficit and energy production of the wind turbines were compared to data collected from a wind farm. The results showed that the Jensen and Jensen–Gaussian models agreed more with the power deficit distribution of the downstream wind turbines than when the same general recommended parameters were applied in all directions. When applied to energy production, the maximum difference among the wake models was approximately 3%. Every wake model clearly showed the relative wake loss tendency of each wind turbine.

Research on the Influence of Turbulence Intensity to the Power Curve and AEP of Wind Turbine

2013 ◽  
Vol 336-338 ◽  
pp. 885-889
Author(s):  
Bo Jiao ◽  
Yang Xue ◽  
De Yi Fu ◽  
Xiao Jing Ma ◽  
Wei Bian ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Turbulence Intensity ◽  
Energy Production ◽  
Wind Farm ◽  
Negative Impact ◽  
Intensity Level ◽  
Power Curve ◽  
Power Performance

It is known that turbulence intensity will affect on power performance and Annual Energy Production (AEP) of wind turbine. But it is unknown how big the influence is. The article quantifies the concrete influence by testing. After calculating the output of wind turbine in different turbulence intensity level, it has shown that the more intensive turbulence will lead more negative impact on the output of wind turbine. The investigation provides some basis for the site sitting of wind farm.

scholarly journals Monin-Obukhov Similarity Theory for Modeling of Wind Turbine Wakes under Atmospheric Stable Conditions: Breakdown and Modifications

2019 ◽  
Author(s):  
Xing Xing Han ◽  
De You Liu ◽  
Chang Xu ◽  
Wen Zhong Shen ◽  
Lin Min Li ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Turbulence Intensity ◽  
Wind Shear ◽  
Similarity Theory ◽  
Turbulence Models ◽  
Wake Effect ◽  
Similarity Functions ◽  
Stable Conditions ◽  
Flow Similarity ◽  
Ambient Turbulence

Monin-Obukhov similarity theory (MOST) overestimates wind shear in some atmospheric stable conditions, i.e. Richardson number $R_f<0.25$. The overestimated wind shear that leads to an under-predicted friction wind speed and a lower ambient turbulence intensity for a given hub-height reference wind speed and a given roughness length, could influence wake modeling of a wind turbine. This work investigates the side effects of the breakdown of MOST on wake modeling under stable conditions and makes some modifications to the flow similarity functions to eliminate these side effects. Based on a field measurement in a wind farm, we firstly show that MOST predicts a larger wind shear for the atmospheric stability parameter $\zeta>0.1$ and proposes new flow similarity functions without constraining $R_f$ to limit the overestimated wind shear by MOST. Next, different turbulence models based on MOST and a modified one based on the new similarity functions are investigated through numerical simulations. These turbulence models are combined with the actuator disk model (AD) and Reynolds-averaged Navier–Stokes equations (RANS) to model wind turbine wakes under stable conditions. As compared to measurements, numerical results show that turbulence models based on MOST result in larger wake deficits and slower wake recovery rate with a square root of the mean-squared-error (RSME) of wake deficit in the range of 0.07-0.18. This overestimated wake effect is improved by applying the new similarity functions and the RSME of wake deficit is averagely reduced by 0.05. Finally, we check the role of the under-predicted turbulence intensity playing in the larger wake deficit predicted by models based MOST. Additional numerical simulations using the modified turbulence model are carried out, in which the roughness length is reduced to impose a hub-height ambient turbulence intensity equivalent to the MOST case. Simulation results show that reducing turbulence intensity enhances wake effects, however, it cannot reproduce the large wake deficit predicted by models based on MOST, which suggests that the overestimated wake effect by MOST could be also related to the overestimated wind shear.

scholarly journals The impact of turbulence intensity and atmospheric stability on power deficits due to wind turbine wakes at Horns Rev wind farm

Wind Energy ◽  
2011 ◽  
Vol 15 (1) ◽  
pp. 183-196 ◽  
Author(s):  
Kurt S. Hansen ◽  
Rebecca J. Barthelmie ◽  
Leo E. Jensen ◽  
Anders Sommer
Keyword(s):  
Wind Turbine ◽  
Turbulence Intensity ◽  
Wind Farm ◽  
Atmospheric Stability ◽  
The Impact

scholarly journals More accurate aeroelastic wind-turbine load simulations using detailed inflow information

2019 ◽  
Vol 4 (2) ◽  
pp. 303-323
Author(s):  
Mads Mølgaard Pedersen ◽  
Torben Juul Larsen ◽  
Helge Aagaard Madsen ◽  
Gunner Christian Larsen
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Turbulence Intensity ◽  
Atmospheric Stability ◽  
Pitot Tube ◽  
Wind Speeds ◽  
Inflow Turbulence ◽  
Mean Wind Speed ◽  
Fatigue Loads ◽  
Aeroelastic Simulations

Abstract. In this paper, inflow information is extracted from a measurement database and used for aeroelastic simulations to investigate if using more accurate inflow descriptions improves the accuracy of the simulated wind-turbine fatigue loads. The inflow information is extracted from nearby meteorological masts (met masts) and a blade-mounted five-hole pitot tube. The met masts provide measurements of the inflow at fixed positions some distance away from the turbine, whereas the pitot tube measures the inflow while rotating with the rotor. The met mast measures the free-inflow velocity; however the measured turbulence may evolve on its way to the turbine, pass beside the turbine or the mast may be in the wake of the turbine. The inflow measured by the pitot tube, in comparison, is very representative of the wind that acts on the turbine, as it is measured close to the blades and also includes variations within the rotor plane. Nevertheless, this inflow is affected by the presence of the turbine; therefore, an aerodynamic model is used to estimate the free-inflow velocities that would have occurred at the same time and position without the presence of the turbine. The inflow information used for the simulations includes the mean wind speed field and trend, the turbulence intensity, the wind-speed shear profile, atmospheric stability-dependent turbulence parameters, and the azimuthal variations within the rotor plane. In addition, instantaneously measured wind speeds are used to constrain the turbulence. It is concluded that the period-specific turbulence intensity must be used in the aeroelastic simulations to make the range of the simulated fatigue loads representative for the range of the measured fatigue loads. Furthermore, it is found that the one-to-one correspondence between the measured and simulated fatigue loads is improved considerably by using inflow characteristics extracted from the pitot tube instead of using the met-mast-based sensors as input for the simulations. Finally, the use of pitot-tube-recorded wind speeds to constrain the inflow turbulence is found to significantly decrease the variation of the simulated loads due to different turbulence realizations (seeds), whereby the need for multiple simulations is reduced.

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