Room:
Diesel Hall
Topic:
B. Wind, wakes, turbulence and wind farms
Form of presentation:
Oral
Duration:
120 Minutes
Chaired by: J. Meyers, J. Peinke
13:30
Polynomial chaos for the computation of annual energy production in wind farm layout optimization
A. Santiago Padron | Stanford University | United States
Show details
Authors:
A. Santiago Padron | Stanford University | United States
Andrew Stanley | United States
Jared Thomas | United States
Juan Alonso | United States
Andrew Ning | United States
Careful management of wake interference is essential to further improve Annual Energy Production (AEP) of wind farms. Wake effects can be minimized through optimization of turbine layout. Realistic wind farm optimization is challenging because it has numerous design degrees of freedom and must account for the stochastic nature of wind. In this paper we provide a framework for calculating AEP for any relevant stochastic variable of interest. We use Polynomial Chaos (PC) to efficiently quantify the effect of the stochastic variables - wind direction and wind speed - on the AEP for wind farm layout optimization. When the stochastic variable includes the wind direction, polynomial chaos is one order of magnitude more accurate in computing the AEP when compared to commonly used simplistic integration techniques (rectangle rule), especially for non grid-like wind farm layouts. This allows for more efficient optimization and uncertainty quantification of wind farm energy production.
13:50
Mapping Wind Farm Load and Power Production – A Case Study on Horns Rev 1
Dr. Nikolay Dimitrov | Technical University of Denmark | Denmark
Show details
Authors:
Dr. Nikolay Dimitrov | Technical University of Denmark | Denmark
Christos Galinos | Denmark
Torben J. Larsen | Denmark
Anand Natarajan | Denmark
Kurt S. Hansen | Denmark
This paper describes the development of a wind turbine (WT) component lifetime fatigue load variation map within an offshore wind farm. A case study on the offshore wind farm Horns Rev I is conducted with this purpose, by quantifying wake effects using the Dynamic Wake Meandering (DWM) method. Based on the mean wind speed and direction distribution, the representative 20-year lifetime fatigue loads are calculated. It is found that the heaviest loaded WT is not the same when looking at different load components. The blade loads are mainly dominated by the wake situations above rated wind speed and the highest loaded blades are in the easternmost row as the dominating wind direction is from West. The results of this paper are expected to have significance for operation and maintenance planning, where the schedules for inspection and service activities can be adjusted to the requirements arising from the varying fatigue levels.
14:10
Statistics of LES Simulations of Large Wind Farms.
Dr. Søren Andersen | Technical University of Denmark | Denmark
Show details
Authors:
Dr. Søren Andersen | Technical University of Denmark | Denmark
Jens Nørkær Sørensen | Denmark
Robert Flemming Mikkelsen | Denmark
Stefan Ivanell | Denmark
Numerous large eddy simulations are performed of large wind farms using the actuator line method, which has been fully coupled to the aero-elastic code, Flex5. The higher order moments of the flow field inside large wind farms is examined in order to determine a representative reference velocity. The stastical moments appear to collapse and hence the turbulence inside large wind farms can potentially be scaled accordingly. The thrust coefficient is estimated by two different reference velocities and the generic C_T expression by Frandsen. A reference velocity derived from the power production is shown to give very good agreement and furthermore enables the very good estimation of the thrust force using only the steady C_T-curve, even for very short time samples. Finally, the effective turbulence inside large wind farms and the equivalent loads are examined.
14:30
A Simple Model for the Turbulence Intensity Distribution in Atmospheric Boundary Layers
Dr. Lawrence Cheung | GE Global Research | United States
Show details
Authors:
Dr. Lawrence Cheung | GE Global Research | United States
Sachin Premasuthan | United States
Samuel Davoust | United States
Dominic von Terzi | United States
In the current work, we examine the distribution of turbulence intensity (TI) in simulations of atmospheric boundary layers (ABL) for wind turbine applications. We relate the turbulent fluctuations to the mean wind shear profile for neutrally stable ABL based on turbulent boundary layer theory. The results are then compared to corresponding LES data for various shear conditions. From this, a model for the TI distribution across a rotor disc is devised and calibrated. In addition, a second simpler version of the model is derived by assuming a power law for the velocity profile. The models are related to the Mann model and shown to have a similar scaling, however they are simpler and based on assumptions for turbulent boundary layers rather than homogeneous turbulence. The models are then tested for a range of stability conditions and shear values of the ABL including waked conditions from upstream wind turbines that stretch the assumptions made.
14:50
In search for a canonical design ABL stability class for wind farm turbines
Gunner Chr. Larsen | DTU | Denmark
Show details
Authors:
Gunner Chr. Larsen | DTU | Denmark
Franck Bertagnolio | Denmark
David Verelst
Abhijit Chougule | Denmark
Production as well as loading of wake exposed wind turbines is known to depend significantly on stability of the Atmospheric Boundary Layer (ABL), which adds a new dimension to design of wind farm turbines. Adding this new aspect in wind turbine design makes the number of design cycle computations to blow up with a factor equal to the number of representative stability bin classes. The research question to be answered in this paper is: Can an ABL stability probability distribution in a meaningful way be collapsed into a representative design stability class as based on a (predefined) confidence level.
15:10
A wind energy benchmark for ABL modelling of a diurnal cycle with a nocturnal low-level jet
Dr. Javier Sanz Rodrigo | CENER | Spain
Show details
Authors:
Dr. Javier Sanz Rodrigo | CENER | Spain
Matthew Churchfield | Spain
Branko KosovicÌ | Spain
The third GEWEX Atmospheric Boundary Layer Studies (GABLS3) model intercomparison study, around the Cabauw met tower in the Netherlands, is revisited as a benchmark for wind energy atmospheric boundary layer (ABL) models. The case was originally developed by the boundary layer meteorology community, interested in analysing the performance of single-column and large-eddy simulation atmospheric models dealing with a diurnal cycle leading to the development of a nocturnal low-level jet. The case addresses fundamental questions related to the definition of the large-scale forcing, the interaction of the ABL with the surface and the evaluation of model results with observations. The characterization of mesoscale forcing for asynchronous microscale modelling of the ABL is discussed based on momentum budget analysis of WRF simulations. Then a single-column model is used to demonstrate the added value of incorporating different forcing mechanisms in microscale models. The simulations are evaluated in terms of wind energy quantities of interest.