Observing and Simulating the Summertime Low-Level Jet in Central Iowa

Vanderwende, Brian Joseph; Lundquist, Julie K.; Rhodes, Michael E.; Takle, Eugene S.; Irvin, S.

doi:10.1175/mwr-d-14-00325.1

Cited by 70 publications

(101 citation statements)

References 72 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…While summer nocturnal lowlevel jets increase boundary-layer wind speeds (Vanderwende et al 2015;Bonin et al 2015), providing ample wind resources during the summer in the Great Plains, the power deficit, the reduction in power production of downwind turbines located within the wakes, increases with atmospheric stability (Hansen et al 2012). New approaches to yawing upwind turbines in order to improve the power production of downwind turbines (Fleming et al 2015(Fleming et al , 2016 require accurate wake prediction.…”

Section: The Evening Boundary Layer and Turbine Wakesmentioning

confidence: 99%

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Lee

Lundquist

2017

Boundary-Layer Meteorol

Self Cite

View full text Add to dashboard Cite

Wind-turbine-wake evolution during the evening transition introduces variability to wind-farm power production at a time of day typically characterized by high electricity demand. During the evening transition, the atmosphere evolves from an unstable to a stable regime, and vertical stratification of the wind profile develops as the residual planetary boundary layer decouples from the surface layer. The evolution of wind-turbine wakes during the evening transition is examined from two perspectives: wake observations from single turbines, and simulations of multiple turbine wakes using the mesoscale Weather Research and Forecasting (WRF) model. Throughout the evening transition, the wake's wind-speed deficit and turbulence enhancement are confined within the rotor layer when the atmospheric stability changes from unstable to stable. The height variations of maximum upwind-downwind differences of wind speed and turbulence intensity gradually decrease during the evening transition. After verifying the WRF-model-simulated upwind wind speed, wind direction and turbulent kinetic energy profiles with observations, the wind-farm-scale wake evolution during the evening transition is investigated using the WRF-model wind-farm parametrization scheme. As the evening progresses, due to the presence of the wind farm, the modelled hub-height wind-speed deficit monotonically increases, the relative turbulence enhancement at hub height grows by 50%, and the downwind surface sensible heat flux increases, reducing surface cooling. Overall, the intensifying wakes from upwind turbines respond to the evolving atmospheric boundary layer during the evening transition, and undermine the power production of downwind turbines in the evening.

show abstract

Section: The Evening Boundary Layer and Turbine Wakesmentioning

confidence: 99%

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Lee

Lundquist

2017

Boundary-Layer Meteorol

Self Cite

View full text Add to dashboard Cite

show abstract

“…Results demonstrated that WRF can provide a better approximation; however, the applicability to accurate projects was uncertain, as other factors such as terrain and canopy were not considered. More recently, Vanderwende et al (2015) noticed that WRF simulations tended to underestimate the jet intensity. It can thus be concluded that NWP models based on WRF are promising at present state, but more progress is needed to consider these models as reasonable options for the detailed analysis of mechanical impacts on turbines.…”

Section: Previous Experiences On Data Collectionmentioning

confidence: 99%

Impacts of the low-level jet's negative wind shear on the wind turbine

et al. 2017

View full text Add to dashboard Cite

Abstract.Nocturnal low-level jets (LLJs) are defined as relative maxima in the vertical profile of the horizontal wind speed at the top of the stable boundary layer. Such peaks constitute major power resources for wind turbines. However, a wind speed maximum implies a transition from positive wind shears below the peak to negative ones above. The effect that such a transition has on wind turbines has not been thoroughly studied.This research study employed a methodical approach to the study of negative wind shear's impacts on wind turbines. Up to now, the presence of negative shears inside the turbine's rotor in relation to the presence of positive shears has been largely ignored. A parameter has been proposed to quantify that presence in future studies of LLJ-wind-turbine interactions. Simulations were performed using the NREL aeroelastic simulator FAST code. Rather than using synthetic profiles to generate the wind data, all simulations were based on real data captured at the high frequency of 50 Hz, which allowed us to perform the analysis of a turbine's impacts with real-life, small scales of wind motions.It was found that the presence of negative wind shears at the height of the turbine's rotor appeared to exert a positive impact on reducing the motions of the nacelle and the tower in every direction, with oscillations reaching a minimum when negative shears covered the turbine swept area completely. Only the tower wobbling in the spanwise direction was amplified by the negative shears; however, this occurred at the tower's slower velocities and accelerations. The forces and moments were also reduced by the negative shears. The aforementioned impacts were less beneficial in the rotating parts, such as the blades and the shafts. Finally, the variance in power production was also reduced. These findings can be very important for the next generation of wind turbines as they reach deeper into LLJ's typical heights.The study demonstrated that the presence of negative shears is significant in reducing the loading on wind turbines. A major conclusion of this study is that the wind turbines of the future should probably be designed with the aim of reaching the top of the nightly boundary layer more often and therefore the altitudes where negative shears are more frequent. Doing so will help to reduce the positive shear's associated damage and to capture the significant LLJ energy.

show abstract

“…The calculation of the equivalent wind speed is discussed in Appendix. Note that the equivalent wind speed does not account for rotor-layer wind veer, which can be significant in certain weather regimes (Walton et al 2014;Vanderwende et al 2015).…”

Section: Estimating the Resulting Power Output And Economic Benefitmentioning

confidence: 99%

“…ERA-interim boundary and initial condition data are used to drive the weather in the outer domain. These choices for physics options and boundary conditions have been selected based on the simulations of Vanderwende et al (2015). The coarsest domain spans the entire continental USA while the finest domain roughly encompasses the State of Iowa (Fig.…”

Section: Model Configuration and Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Could Crop Height Affect the Wind Resource at Agriculturally Productive Wind Farm Sites?

Vanderwende

Lundquist

2015

Boundary-Layer Meteorol

Self Cite

View full text Add to dashboard Cite

The collocation of cropland and wind turbines in the US Midwest region introduces complex meteorological interactions that could influence both agriculture and wind-power production. Crop management practices may affect the wind resource through alterations of land-surface properties. We use the weather research and forecasting (WRF) model to estimate the impact of crop height variations on the wind resource in the presence of a large turbine array. A hypothetical wind farm consisting of 121 1.8-MW turbines is represented using the WRF model wind-farm parametrization. We represent the impact of selecting soybeans rather than maize by altering the aerodynamic roughness length in a region approximately 65 times larger than that occupied by the turbine array. Roughness lengths of 0.1 and 0.25 m represent the mature soy crop and a mature maize crop, respectively. In all but the most stable atmospheric conditions, statistically significant hub-height wind-speed increases and rotor-layer wind-shear reductions result from switching from maize to soybeans. Based on simulations for the entire month of August 2013, wind-farm energy output increases by 14 %, which would yield a significant monetary gain. Further investigation is required to determine the optimal size, shape, and crop height of the roughness modification to maximize the economic benefit and minimize the cost of such crop-management practices. These considerations must be balanced by other influences on crop choice such as soil requirements and commodity prices.

show abstract

Observing and Simulating the Summertime Low-Level Jet in Central Iowa

Cited by 70 publications

References 72 publications

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Observing and Simulating Wind-Turbine Wakes During the Evening Transition

Impacts of the low-level jet's negative wind shear on the wind turbine

Could Crop Height Affect the Wind Resource at Agriculturally Productive Wind Farm Sites?

Contact Info

Product

Resources

About