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The Science of Making Torque from Wind (TORQUE 2018)

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Room: BL.27.0.1
Chaired by: Jakob Mann | DTU
Topic: MET. Measurement and Experimental Techniques
Form of presentation: Oral
Duration: 90 minutes

Authors:
Laura Valldecabres Sanmartin, Nicolai Gayle Nygaard, Lueder von Bremen, Martin Kühn

Abstract:
Probabilistic extremely short-term forecasts of wind farm power are  valuable information for electricity market participants, especially in power systems with high penetration of wind energy. Recently, the first fully resolved dual-Doppler radar measurements of an offshore wind farm have become available. A probabilistic nowcast model of wind power is proposed using wind speed and direction observations and a power curve. The forecasting horizon is set to five minutes. Probabilistic wind speed ensembles are constructed using three-dimensional dual-Doppler observations covering the wind farm and its vicinity. Preliminary results show an improved performance of the probabilistic forecast versus the benchmark persistence.

Authors:
Christoph Dollinger, Nicholas Balaresque, Nicholas Gaudern, Michael Sorg, Andreas Fischer

Abstract:
Due to operation under harsh conditions, rotor blades suffer from soiling and erosion of the leading edge, which causes a premature laminar-turbulent transition of the boundary layer flow. A quantification of both the extent of the contamination and the impact on wind turbine performance is difficult and calculations are based on estimates. A new method for assessing the power output loss due to leading edge contamination is presented. The method is based on thermographic flow measurements along the rotor blade and the automated determination of the laminar-turbulent transition location. A comparison with the expected natural transition of the clean rotor blade position enables the extent of the leading edge contamination to be quantified. Measurements on a multi-MW rotor blade indicate a contamination level of up to 90.4 % in the given highly contaminated example. This information is then used in a blade element method (BEM) model to calculate the annual energy production (AEP) for both a clean and a contaminated case. Results indicate that for this particular case, the measured contamination level leads to a decrease in annual energy production of 4.7 % to 2.7 % for the investigated average wind speeds of 6 m/s to 9 m/s.

Authors:
Stefan Kock, Georg Jacobs, Andreas Hirt, Sergej Oberdörfer, Stephan Neumann, Dennis Bosse

Abstract:
This paper introduces the innovative approach for the creation of the robustness test against specific failures of the planetary and HSS bearings (e.g. smearing, micro-pitting, classical fatigue and lip fractures) in the wind turbine gearboxes. The introduced bearing robustness test (BRT) considers the system-depended characteristics (e.g. drive train design, interaction between components, assembly process, lubricant aging) and real dynamic load conditions, frequencies and sequence. The creation of the BRT is based on the field and simulation data. The core element is the simulative approach for the determination of the path of the external wind and grid load to the local loads of the bearing. BRT aims the mapping of the most critical, but real, field load situations in the bearing test rig. By means of the BRT it is possible to evaluate the robustness of bearing against specific field conditions in early product cycle and consequently to enhance the quality and to reduce the failure rate of the bearing.

Authors:
Hongkun Zhang, Mohsen Neshati

Abstract:
Efficiency measurement under various load conditions is an important prerequisite for the validation of wind turbine drive train systems. Current measurement methods rely highly on the accuracy of the mechanical torque measurement, which is substantially limited by the high level of torque as well as the available calibration capacity. This paper proposes a new method of test and measurement procedures, aiming to substantially reduce the dependency of the efficiency accuracy on the torque and electrical power measurement. Instead of measuring the efficiency directly, the new method focuses on measuring the power loss and in this way reduces the uncertainty of the determined efficiency. The efficiency uncertainty is analysed in detail in the paper with considerations of different sources of measurement uncertainty and their contributions. An example of uncertainty calculation with typical parameters is presented for the demonstration. The study shows that the new method can effectively reduce the affect of the torque (as well as the electrical power) uncertainty on the overall uncertainty of the determined efficiency, and therefore achieve a good accuracy despite of the unfavourable accuracy of the torque measurement. Finally, experimental tests have been performed on a scaled dynamometer test bench, where the efficiencies at different operation points are determined with the new method. The result are presented in the paper together with the uncertainty.

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