Saarblitz, Wind farm in HDR,, creative commons by-nc-sa 2.0


Managed by

Data Provider: 

Kurt S. Hansen (DTU), licensed by Vattenfall

Data accesibility: 

The test case is offered to participants of the IEA Task 31 Wakebench.

Site Description: 

The measurements were carried out from January 01, 2008 to Dedember 31, 2012 at Lillgrund offshore wind farm in Öresund, the body of water between Malmö, Sweden and Copenhagen, Denmark.  The farm consists of 48 Siemens SWT-2.3-93 wind turbines (Figure 1), each producing a rated power of 2.3 MW at around 12 m/s with a rotor diameter of 93 m and a hub height of 65 m.  The turbines are arranged in a dense array with separation of 3.3 rotor diameters (D) within a row and 4.3 D between rows.

Figure 1   Layout of the Lillgrund offshore wind farm (Dahlberg, 2009).

All the wind turbines at Lillgrund offshore wind farm are SWP 92.6m, 2.3MW; which operates with variable speed and variable pitch. The operational behavior (Figure 2) of the wind turbines are characterized with:

  • Official power curve;
  • Thrust coefficient curve;
  • Rotor speed curve and
  • Pitch curve as function of wind speed

Figure 2: Operational data for SWT-2.3-93m, installed at Lillgrund WF.


The turbines are equipped with a SCADA system to record normal wind power plant information, which are stored as 10 minute statistical values. The signals comprises of electric power, rotor speed, blade pitch angle, yaw position and nacelle wind speed. Part time (2008-2010) the instrumented 65 m meteorological mast 250 m to the southwest of turbines 23 and 30 is available. The mast instrumentation consists of cup anemometers, wind vanes and one thermometer. Unfortunately there is no suitable temperature measurement that would facilitate the isolation of atmospheric stability in this data set.

Measurement Campaign: 

The measurement campaign was divided into three periods:

  • Period 2003.09-2006.01 includes only meteorological measurements before installation of WF as documented in Bergström (2009);
  • Period 2008.01-2011.03 includes both meteorological measurements (mean values only), which can be merged with WF SCADA dataset, unfortunately without any valid wind turbine yaw position signals. The preliminary analysis documented in Dahlberg (2009) is based on measurements from the period 2007.12-2009.02 where all wind turbines has been online;
  • Period 2011.04-2013.03 includes wind farm SCADA data, but without mast measurements.

Inflow conditions in terms of mean shear and mean turbulence intensities as function of wind speed are listed in Bergström (2009).


Before the data analysis is performed it is necessary to define the inflow conditions e.g. wind speed and wind direction at hub height. Due to a lack of meteorological measurements during the second period; an inflow reference can only be establish from a leading wind turbines with undisturbed inflow. The inflow wind speed can be determined from the power signal combined with the official power curve, while the inflow direction can be derived from a calibrated wind turbine yaw position.

Determination of the atmospheric stratification is difficult due to a lack of either air-air or air-water temperature difference.



Dahlberg, J.-Å., “Assessment of the Lillgrund Wind Farm: Power Performance Wake Effects,” [online report] Vattenfall Vindkraft AB, 6_1 LG Pilot Report, Sept. 2009, URL: W.pdf_16596737.pdf  [cited 27 June 2012].

Bergström, H., “Meteorological Conditions at Lillgrund,” [online report] Vattenfall Vindkraft AB, 6_2 LG Pilot Report, Mar. 2009, URL: 16614584.pdf  [cited 27 June 2012].

Jeppsson, J., Larsen, P.E., Larsson, Å.  “Technical Description of Lillgrund Wind Power Plant,” [online report] Vattenfall Vindkraft AB, 2_1 LG Pilot Report, Sept. 2008, URL:  [cited 27 June 2012].


Not applicable.