The overall aim of this project is to increase knowledge about how to best optimize tomorrow's
large wind farms, i.e., how to increase production and minimize loads. The result of this knowledge will therefore ensure lower cost per produced energy.

The project is divided into nine tasks. They are strongly linked and are all working towards increasing understanding of flows inside and around wind farms. Some tasks are more focused on fundamental understanding, some are more applied and some are on the edge of implementation for use by the industry in the near future. The project is also active in a number of other international projects related to these tasks.

Below a short summary the different tasks and their relations to each other can be found.

Ongoing Projects

Task 1: Farm to farm interaction

Financed by VindForsk

O. Eriksson, Uppsala University and I. Carlén, Teknikgruppen

The main focus of this work is to obtain a better understanding of the long distance wakes behind wind farms to, in a later stage, be able to better understand how wind farms interact with each other. This will lead to reduced uncertainties in production and load estimations. The project uses established numerical methods, so called Computational Fluid Dynamics (CFD). Large Eddy Simulations (LES) are used together with an Actuator Disc (ACD) approach to study the long distance wakes. The simulations are performed with the parallelized EllipSys3D code.

The first part of the task is presented in the licentiate thesis:

O. Eriksson, Numerical Computations of Wakes Behind Wind Farms. (Department of Earth Sciences Licentiate Thesis 2015, Uppsala Universitet), 2015.

Planned work:

In the second part of this task the meso- micro scale coupling will be further studied and in a later stage the possibility of extending this method to onshore farms will be examined.

Task 2: Integration of body force methods for higher precision wake modelling simulations for offshore applications

Financed by Norwegian research council

N. Simisiroglou, WindSim AS / Uppsala University

The primary objective of this project is to identify, test and implement the best method(s) for wake simulations for oshore wind farms. The secondary objective is to implement the method(s) into WindSim, a commercial available wind farm design software, taking into account the typical available computa-
tional resources of industrial users.

Task 3:

Financed by Swedish Energy Agency

Task 4:

Financed by

Task 5:

Financed by Swedish Energy Agency

Task 6: Development of Large Eddy Simulation Tools for Simulation of Atmospheric Boundary Layers in Wind Farms

Financed by The Danish research council

K. O. Dag, DTU

The general objective of the project is to develop a high-order accurate Navier-Stokes/Actuator Line technique for Large Eddy Simulations of turbulent boundary layers around and inside wind farms. The numerical approach is anticipated to combine high-order finite-difference schemes with a Fourier-decomposed spectral method where horizontal axes will be represented by Fourier modes and the vertical will be treated with a high-order finite-difference approach. To include the stability of the atmospheric boundary layer, Boussinesq approximation will be used. Various sub-grid scale turbulence models will be considered and tested, and the code will be validated against in-house EllipSys3D code and full-scale experimental data.

Planned work:

•  Development of a pseudo spectral NS solver (complete)
  
• Implementation of a SGS turbulence model (complete)
  
• Implementation of wind turbine forces (complete)
  -A simple actuator line code is implemented for a stiff blade
  
• Parallelizing the code (complete)
  - Pure MPI parallelization by using 2 level domain decomposition
  
• Validation
  -Validation of LES via. comparing against a DNS isotropic turbulence
  -Validation of wind turbine forcing by comparing circulation distributions on blades against EllipSys3D simulations

Task 7: Numerical simulations of atmospheric boundary layers

Financed by The Swedish research council (VR)

E. Boström, KTH

This task deals with large eddy simulations (LES) of atmospheric boundary layers (ABLs). For the simulations we will employ high-order numerical codes (SIMSON1 now, and maybe Nek50002 later). The simulations are to be validated for a number of stable and unstable atmospheric conditions. Furthermore, different surface-roughness conditions will be implemented and assessed, which are representative of different terrains. In addition, at a later stage, a goal is also to include real terrain level changes in the simulations. Once the atmospheric model is established it will be used for wind turbine simulations.

Planned work:

• LES wall-model implementation in SIMSON
• Simulations of a natural atmospheric boundary layer
  -Validation and comparison to known results
• Adding complexity to the LES model/numerical codes used

Task 8: Flow physics of wind farms in complex terrains

Financed by The Swedish research council (VR)

A. Hyvärinen, KTH

The goal of the project is to increase the understanding of the turbulent flow fields around wind turbines and wind farms at on-shore locations. An experimental study of wind turbine wake interactions will be performed, both regarding interactions between individual wind turbine wakes and the flow fields in larger wind farms. Additionally the effect of complex terrain on the wind turbine wake development will be studied. The experimental data acquired during the project will provide a database for validation of numerical simulations.

Task 9: Development of Noise Propagation Models for Wind Farms

Financed by The Danish research council

E. Barlas, DTU

Noise from wind turbines in wind farms plays an important role in the development of wind energy at onshore and near-shore locations. The regulations of various countries urge turbine manufacturers to reduce the noise emission of wind turbines and that the developers have better noise predictions. The goal of the project is to develop advanced noise propagation methods and tools with the aim of designing low noise wind farms.

Stages:

Development of the Propagation Tool

Coupling with Noise Source Model and WAsP Engineering

Experimental Validation

Wind Farm Extension

Planned work:

• Development of the propagation tool
• Coupling with the source model and WEng
• The coupled source-propagation model needs certain adjustment parameters
• Possible aeroelastic code coupling
• Experimental Validation
• W.F. Extension

Finished Projects

Wake instability and interaction, KTH (Energimyndigheten)

 Sasan Sarmast, PhD student

Financed by The Swedish Energy Agency

Experimental validation, KTH, Vattenfall (Energimyndigheten)

Ylva Nordmark, PhD student

Financed by The Swedish Energy Agency

Optimizing wind parks

Søren Hjul Andersen, PhD student at DTU, Denmark

Financed by The Danish Research Program.

Farm Control and Optimization

Karl Nilsson, PhD student at Gotland University/KTH

Financed by VindForsk

ICEWIND 

Kjeller VindTekknik

This project was a part of a larger project ICEWIND. 

Financed by Nordic Energy Research and Gotland University

Control of windparks

Teknikgruppen

Financed by VindForsk