# Wind energy II. Lesson 2. Wind speed measurement

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### Text of Wind energy II. Lesson 2. Wind speed measurement

• 1. Wind Energy IWind speed measurementsMichael Hlling, WS 2010/2011 slide 1

2. Wind Energy IClass content5 Wind turbines in 6 Wind - bladesgeneral2 Wind measurementsinteraction7 -theorem 8 Wind turbine characterization3 Wind field9 Control strategiescharacterization 10 Generator4 Wind power 11 Electrics / gridMichael Hlling, WS 2010/2011 slide 2 3. Wind Energy I Wind speed measurements 1. Pressure sensors - e.g. Prandtl tube with manometer 2. Cup anemometer 3. Ultrasonic anemometer (USA) 4. Light detection and ranging (LiDAR) 5. New developments - e.g. sphere anemometerMichael Hlling, WS 2010/2011slide 3 4. Wind Energy I Sensor resolutionTemporal and spatial resolution Taylors hypothesis - picture of frozen turbulence: Eddies have much longer life-time than they need to travel past a sensor u 1D, 1Hz, wear of bearings,over-speedingultrasonic anemometry --> expensive, wakeeffects of transducer supportsPropertieswind velocity and direction measurementstemporal resolution up to resonance frequencyMichael Hlling, WS 2010/2011slide 18 19. Wind Energy I Sphere anemometer Measurement principledeection of a exible tube due to drag forces actingl3 Fs Fts= + EJ 38with general expression for drag force 1 F = A cD v 2 2drag coefcient cD considered constant forRe 103 . . . 2 105 leads to sv v =m2sEasy calibration function!Michael Hlling, WS 2010/2011slide 19 20. Wind Energy I Sphere anemometer Measurement principledeection of a exible tube due to drag forces actingl3 Fs Fts= +Kugelsphere EJ 38with general expression for drag forcelaserLaser 1 F = A cD v 2 Rohr l 2drag coefcient cD considered constant fortubeRe 103 . . . 2 105 leads to Gewinde sv v =m2s 2D-PSDEasy calibration function!Michael Hlling, WS 2010/2011slide 19 21. Wind Energy I Sphere anemometerCalibration 270v [m/s]0.3200.2170.1 14Ux [V]0.0 0180119 0.17 0.2! 532 0.3 1 9000.3 0.2 0.10.0 0.1 0.2 0.3 Uy [V]Michael Hlling, WS 2010/2011slide 20 22. Wind Energy ISphere anemometerGusts measurementsMichael Hlling, WS 2010/2011slide 21 23. Wind Energy ISphere anemometerComparison of time seriesu [m/s] t [s] measured turbulence intensities 33%32% 8% hot-wire anemometer spherecup anemometerMichael Hlling, WS 2010/2011 slide 22 24. Wind Energy ISphere anemometerComparison of power spectraMichael Hlling, WS 2010/2011slide 23 25. Wind Energy ISphere anemometer Evolution of sphere anemometer2007 2008 20092010Michael Hlling, WS 2010/2011slide 24

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