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Title Verification of simulated fatigue loads on wind turbines operating in wakes
Author Johansen, Nicholas Alan
Supervisor Hansen, Kurt Schaldemose (Fluid Mechanics, Department of Mechanical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Larsen, Torben J. (Wind Energy Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Aagaard Madsen, Helge (Wind Energy Division, Risø National Laboratory for Sustainable Energy, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
Institution Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
Thesis level Master's thesis
Year 2009
Abstract The Dynamic Wake Meandering (DWM) model is a new wake model designed to model both increased fatigue loading and decreased energy production of the wake effected turbines. The model has been adopted by the TOPFARM project geared towards developing new methods of designing wind farms and wind farm control considering both energy production and wind turbine fatigue loading. The DWM model implementation in the HAWC2 aeroelastic simulation has been verified with operational measurements although this new verification project was developed to compare simulated fatigue loads against actual measured fatigue loads for turbines operating in single wake conditions. The previous work done in [4] has shown that fatigue loads can increase with separation distance and this has been attributed to the meandering of the wake deficit as it translates downstream. This project aims to determine the simulated general trends of wind turbine component fatigue as a function of turbine separation distance, atmospheric boundary layer stability, inflow hub height wind speed, and ambient turbulence intensity. Fatigue load measurements from operational single wake cases are analyzed and compared to the general trends found from the model. Structural loads measurements from three fully instrumented Vestas wind turbines are available from two large offshore wind farms, Horns Rev, Denmark and Egmond Aan Zee, Netherlands. ln ad- dition, the SCADA measurements and meteorological mast measurements are available from the wind farms as well. After a thorough assessment of the quality of the data, the measurements were filtered and queried to identify time periods of wake conditions on the instrumented turbines. Aeroelastic models in HAWC2 are made and the structural dynamics and the operational parameters are tested to ensure a close match to the measurements. Detailed queries into the large volume of data are post processed and the results are compared to the general trends found in the simulation results. For free inflow conditions, the fatigue loading in the simulation and the measurements are in close agreement for two wind speed conditions, 6 m/sec and 8 m/ sec. For single wake conditions observed in the Egmond Aan Zee and Horns Rev wind farms, the turbine tower base fatigue loading was found to decrease with separation distance between wake generating and the wake effected turbine. This is contrary to the results from the simulation when the meandering component is enabled. When the meandering component is disabled, the general trend in fatigue loading from the simulation is in close agreement with the measurements. The model was not tested in multiple wake situations, although detailed analysis of the measurements have shown that the peak fatigue loading occurs on the turbine at the end of the row. The simulation tends to over predict the wake affected turbine power deficit for low wind speeds and accurately predict the power deficit for the 12 m/sec case. The details of the methods used, key findings from the measurements and simulation, and the thorough discussions of these conclusions are the subjects of this paper.
Pages 119
Keywords wind turbine, wind farms, fatigue loads, wake
Fulltext
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Admin Creation date: 2009-10-27    Update date: 2010-01-21    Source: dtu    ID: 251636    Original MXD