Comparison of Wake Model Simulations with Offshore Wind Turbine Wake Profiles Measured by Sodar

Abstract This paper gives an evaluation of most of the commonly used models for predicting wind speed decrease (wake) downstream of a wind turbine. The evaluation is based on six experiments where free-stream and wake wind speed profiles were measured using a ship-mounted sodar at a small offshore wind farm. The experiments were conducted at varying distances between 1.7 and 7.4 rotor diameters downstream of the wind turbine. Evaluation of the models compares the predicted and observed velocity deficits at hub height. A new method of evaluation based on determining the cumulative momentum deficit over the profiles is described. Despite the apparent simplicity of the experiments, the models give a wide range of predictions. Overall, it is not possible to establish any of the models as having individually superior performance with respect to the measurements.

[1]  H. Charnock.  Wind stress on a water surface , 1955 .

[2]  P. Vermeulen.  An experimental analysis of wind turbine wakes , 1980 .

[3]  A.M.O. Smith,et al.  Turbulence models and their application in hydraulics: W. Rodi, University of Karlsruhe, International Association for Hydraulic Research, Rotterdamseweg 185, 2600 MH Delft, The Netherlands , 1981 .

[4]  D. Etling,et al.  Application of the E-ε turbulence model to the atmospheric boundary layer , 1985 .

[5]  J. Højstrup,et al.  A Simple Model for Cluster Efficiency , 1987 .

[6]  R. Stull.  An Introduction to Boundary Layer Meteorology , 1988 .

[7]  Julio Hernández,et al.  Experimental validation of the UPM computer code to calculate wind turbine wakes and comparison with other models , 1988 .

[8]  J. F. Ainslie,et al.  CALCULATING THE FLOWFIELD IN THE WAKE OF WIND TURBINES , 1988 .

[9]  Spyros G. Voutsinas,et al.  A Study of the Flow Downstream of a Wind Turbine Using Measurements and Simulations , 1996 .

[10]  Fatigue life consumption in wake operation , 1997 .

[11]  Rebecca J. Barthelmie.  Monitoring offshore wind and turbulence characteristics in Denmark , 1999 .

[12]  Gunner Chr. Larsen,et al.  Comparison of Wake Models with Data for Offshore Windfarms , 2001 .

[13]  Gunner Chr. Larsen,et al.  ENDOW: Improvement of Wake Models within Offshore Wind Farms , 2001 .

[14]  Rebecca J. Barthelmie,et al.  Offshore windpower: a major new source of energy for Europe , 2002 .

[15]  N. M. Nielsen,et al.  Offshore Wind Turbine Wakes Measured by Sodar , 2003 .

[16]  Rebecca J. Barthelmie,et al.  Modelling of Offshore Wind Turbine Wakes with the Wind Farm Program FLaP , 2003 .

[17]  Commission,et al.  Efficient Development of Offshore Windfarms (ENDOW) , 2003 .

[18]  J. Schepers.  ENDOW: Validation and improvement of ECN's wake model , 2003 .

[19]  Gunner Chr. Larsen,et al.  Mean wake deficit in the near field , 2003 .

[20]  Gunner Chr. Larsen,et al.  ENDOW (efficient development of offshore wind farms): modelling wake and boundary layer interactions , 2004 .

[21]  Rebecca J. Barthelmie,et al.  Analytical modelling of wind speed deficit in large offshore wind farms , 2006 .