Wind energy II. Lesson 2. Wind speed measurement
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This document discusses different technologies for measuring wind speed and characterizing wind fields that are important for wind energy applications. It covers pressure sensors, cup anemometers, ultrasonic anemometers, LiDAR, and developing technologies like sphere anemometers. For each technology, it provides details on the measurement principles, capabilities, limitations, and considerations. The focus is on evaluating different wind speed sensor designs and understanding how measurements from these sensors can be used to characterize wind resources and model wind fields.
![Wind Energy I Cup anemometry
Calibration
5
4
u [m/s]
3
U [V]
U[V]
2
1
0
0 1000 2000 3000 4000 5000 f [Hz]
t t[s]
[s]
optoelectronic detection
inductive detection
Michael Hölling, WS 2010/2011 slide 9](https://image.slidesharecdn.com/12ndlesson-111024033400-phpapp02/85/Wind-energy-II-Lesson-2-Wind-speed-measurement-9-320.jpg)
![Wind Energy I Cup anemometry
Over-speeding
gusts at 2/3 Hz, 9 m/s
v [m/s]
u [m/s]
t [s]
measured turbulence intensity
33% 8%
hot-wire anemometer cup anemometer
Michael Hölling, WS 2010/2011 slide 10](https://image.slidesharecdn.com/12ndlesson-111024033400-phpapp02/85/Wind-energy-II-Lesson-2-Wind-speed-measurement-10-320.jpg)
![Wind Energy I Sphere anemometer
Calibration
270° v [m/s]
0.3
20
0.2
17
0.1 14
Ux [V]
0.0 0° 180° 11
9
–0.1
7
–0.2
! 5
3
2
–0.3 1
90°
0
–0.3 –0.2 –0.1 0.0 0.1 0.2 0.3
Uy [V]
Michael Hölling, WS 2010/2011 slide 20](https://image.slidesharecdn.com/12ndlesson-111024033400-phpapp02/85/Wind-energy-II-Lesson-2-Wind-speed-measurement-21-320.jpg)
![Wind Energy I Sphere anemometer
Comparison of time series
u [m/s]
t [s]
measured turbulence intensities
33% 32% 8%
hot-wire anemometer sphere cup anemometer
Michael Hölling, WS 2010/2011 slide 22](https://image.slidesharecdn.com/12ndlesson-111024033400-phpapp02/85/Wind-energy-II-Lesson-2-Wind-speed-measurement-23-320.jpg)
Wind energy II. Lesson 2. Wind speed measurement
- 1. Wind Energy I Wind speed measurements Michael Hölling, WS 2010/2011 slide 1
- 2. Wind Energy I Class content 5 Wind turbines in 6 Wind - blades general 2 Wind measurements interaction 7 Π-theorem 8 Wind turbine characterization 3 Wind field 9 Control strategies characterization 10 Generator 4 Wind power 11 Electrics / grid Michael Hölling, 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 anemometer Michael Hölling, WS 2010/2011 slide 3
- 4. Wind Energy I Sensor resolution Temporal and spatial resolution Taylor’s hypothesis - picture of frozen turbulence: “Eddies have much longer life-time than they need to travel past a sensor” σu << 1 u temporal resolution limits spatial resolution AND spatial resolution limits temporal resolution Michael Hölling, WS 2010/2011 slide 4
- 5. Wind Energy I Pressure measurements Why should we measure the pressure ? Bernoulli equation: ptotal = pdyn + pstatic with: pdyn = 1/2 · ρair · u 2 Prandtl tube Michael Hölling, WS 2010/2011 slide 5
- 6. Wind Energy I Pressure measurements Therefore the velocity is Measure the pressure e.g. with given by: an “inclined tube manometer” 2 · (ptotal − pstatic ) u= ρair Michael Hölling, WS 2010/2011 slide 6
- 7. Wind Energy I Cup anemometry Why this basic design ? u urot Michael Hölling, WS 2010/2011 slide 7
- 8. Wind Energy I Cup anemometry Different models Michael Hölling, WS 2010/2011 slide 8
- 9. Wind Energy I Cup anemometry Calibration 5 4 u [m/s] 3 U [V] U[V] 2 1 0 0 1000 2000 3000 4000 5000 f [Hz] t t[s] [s] optoelectronic detection inductive detection Michael Hölling, WS 2010/2011 slide 9
- 10. Wind Energy I Cup anemometry Over-speeding gusts at 2/3 Hz, 9 m/s v [m/s] u [m/s] t [s] measured turbulence intensity 33% 8% hot-wire anemometer cup anemometer Michael Hölling, WS 2010/2011 slide 10
- 11. Wind Energy I Cup anemometry Inclined flow tilt response anemometer Type 3.3351.00.000 , serial 0807011 at ca. 10 m/s dataset 1796_09 0,1 nozzle 0,08 0,06 -20° 0,04 nozzle rel. deviation of anemoemter frequency 0,02 0 +20° -0,02 -0,04 -0,06 -0,08 -0,1 -0,12 -0,14 -0,16 -0,18 -0,2 -34 -32 -30 -28 -26 -24 -22 -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 tilt angle /° dev. V anemo at 1Hz dev. V anemo bin average Michael Hölling, WS 2010/2011 slide 11
- 12. Wind Energy I Cup anemometry Summary low temporal resolution (about 1Hz) effected by inertia not sensitive to wind direction moving parts result in wear of bearings sensitive to icing www.thiesclima.com Michael Hölling, WS 2010/2011 slide 12
- 13. Wind Energy I Ultrasonic anemometry Measurement principle Michael Hölling, WS 2010/2011 slide 13
- 14. Wind Energy I Ultrasonic anemometry Different models - 2D and 3D Michael Hölling, WS 2010/2011 slide 14
- 15. Wind Energy I Ultrasonic anemometry Drawbacks Deviation from horizontal velocity u supports create wakes system is expensive Michael Hölling, WS 2010/2011 slide 15
- 16. Wind Energy I LiDAR Measurement principle Michael Hölling, WS 2010/2011 slide 16
- 17. Wind Energy I LiDAR Possibilities with LiDAR Michael Hölling, WS 2010/2011 slide 17
- 18. Wind Energy I Sphere anemometer Motivation alternative to cup anemometry --> 1D, 1Hz, wear of bearings, over-speeding ultrasonic anemometry --> expensive, wake effects of transducer supports Properties wind velocity and direction measurements temporal resolution up to resonance frequency Michael Hölling, WS 2010/2011 slide 18
- 19. Wind Energy I Sphere anemometer Measurement principle deflection of a flexible tube due to drag forces acting l3 Fs Ft s= · + E·J 3 8 with general expression for drag force 1 F = · · A · cD · v 2 2 drag coefficient cD considered constant for Re ≈ 103 . . . 2 · 105 leads to √ s∝v ⇒v =m· 2 s Easy calibration function! Michael Hölling, WS 2010/2011 slide 19
- 20. Wind Energy I Sphere anemometer Measurement principle deflection of a flexible tube due to drag forces acting l3 Fs Ft s= · + Kugel sphere E·J 3 8 with general expression for drag force laser Laser 1 F = · · A · cD · v 2 Rohr l 2 drag coefficient cD considered constant for tube Re ≈ 103 . . . 2 · 105 leads to Gewinde √ s∝v ⇒v =m· 2 s 2D-PSD Easy calibration function! Michael Hölling, WS 2010/2011 slide 19
- 21. Wind Energy I Sphere anemometer Calibration 270° v [m/s] 0.3 20 0.2 17 0.1 14 Ux [V] 0.0 0° 180° 11 9 –0.1 7 –0.2 ! 5 3 2 –0.3 1 90° 0 –0.3 –0.2 –0.1 0.0 0.1 0.2 0.3 Uy [V] Michael Hölling, WS 2010/2011 slide 20
- 22. Wind Energy I Sphere anemometer Gusts measurements Michael Hölling, WS 2010/2011 slide 21
- 23. Wind Energy I Sphere anemometer Comparison of time series u [m/s] t [s] measured turbulence intensities 33% 32% 8% hot-wire anemometer sphere cup anemometer Michael Hölling, WS 2010/2011 slide 22
- 24. Wind Energy I Sphere anemometer Comparison of power spectra Michael Hölling, WS 2010/2011 slide 23
- 25. Wind Energy I Sphere anemometer “Evolution” of sphere anemometer 2007 2008 2009 2010 Michael Hölling, WS 2010/2011 slide 24