Smart Wind Turbine Blades

1. Smart Wind Turbine Blades Cassel, Fraser, Larsen, McCrummen, Sarrazin ME 580 – Smart Structures Sensor Team

2. ME 580 – Smart Wind Turbine Blades – Sensor Team Objective: • Gather and support development for sensors in wind turbine blades. • Investigate multiple types of sensors to allow for monitoring or measuring: • Structural Loads • Tip Deflection • Damage • Environmental Aspects

3. ME 580 – Smart Wind Turbine Blades – Sensor Team • Current Data and Usage

4. ME 580 – Smart Wind Turbine Blades – Sensor Team

5. ME 580 – Smart Wind Turbine Blades – Sensor Team Piezoelectric Sensing • 4 Types • Single Crystal • Original • Ceramic • Similar to single crystal • Polymer (PVDF) • Flexible, poor for actuation • Active Fiber Composite (AFC) • Subset of Ceramic • Flexible • Compromise

6. ME 580 – Smart Wind Turbine Blades – Sensor Team Piezoelectric Sensors • Wide frequency range • High voltage output (particularly PVDF) • No power supply needed • PVDF has low acoustic impedance, good for adhesives • High compliance in PVDF • Flexible, thin, easily manipulated

7. ME 580 – Smart Wind Turbine Blades – Sensor Team Piezoelectric Sensor • Drawbacks/Considerations • Temperature range for PVDF: -40 to 80/100°C (Not as bad for PZT) • Strong pyroelectric effect • Inability to actuate large displacements • Inability to sense static load • Capacitive effect of unloaded area • Crosstalk if both driving signal and sensing

8. ME 580 – Smart Wind Turbine Blades – Sensor Team Piezoelectric AFC • Ceramic-Polymer composite • Advantages: can custom design properties • Tradeoffs • Properties determined by: • Ceramic type • Polymer Properties • Volume fraction

9. ME 580 – Smart Wind Turbine Blades – Sensor Team Impact Sensing • Weather Detection • Active control • Damage prevention • Wind Gust Detection • Active control • PVDF appropriate if surface mounted • Thin • Sensitive

10. ME 580 – Smart Wind Turbine Blades – Sensor Team Vibration Sensing • Vibration hurts performance/strength • Active control • Most sensors can detect • Primary considerations: Wide frequency range, Cost • PVDF good for surface mount

11. ME 580 – Smart Wind Turbine Blades – Sensor Team Ultrasonic/NDT • Piezoelectric typically used. • PVDF good if done during operation • 1/64th in. smallest size • Depth small for small flaw

12. ME 580 – Smart Wind Turbine Blades – Sensor Team Metal Foil Gauges • Uses wire resistance change to compute strain • Most commonly used gauge in engineering • Can use strain to compute stress, torque, and pressure

13. ME 580 – Smart Wind Turbine Blades – Sensor Team Metal Foil Gauges Advantages • Strain and Pressure gages • Widely available • Cheap • Easy to apply • Easy to use

14. ME 580 – Smart Wind Turbine Blades – Sensor Team Metal Foil Gauges Disadvantages • Must be properly bonded • Sensitive to temperature changes • Maximum strain limited to foil material used (3%) • Size limitations • Can change resistance over time (creep) • Susceptible to fatigue

15. ME 580 – Smart Wind Turbine Blades – Sensor Team Piezo-resistive Sensing – Basic Structure http://www.microsystems.metu.edu.tr/piezops/piezops.html

16. ME 580 – Smart Wind Turbine Blades – Sensor Team Piezo-resistive Sensing – Background • Types of measurement • Pressure • Force • Higher sensitivity than standard strain gage • Pressure Sensor Calibration • Able to be microfabricated http://www.ceatec.com/2007/en/visitor/ex_must_detail.html?exh_id=E070209 http://cooperinst.thomasnet.com/Asset/lpm562.pdf

17. ME 580 – Smart Wind Turbine Blades – Sensor Team Piezo-resistive Sensing – Pros and Cons • Pros • Low fabrication cost • Varying pressure levels can be achieved • High sensitivity (>10mV/V) • Good data linearity at constant temp. • Cons • Requires significant amount of power • Low output signal • Strong drift of offset with temperature

18. ME 580 – Smart Wind Turbine Blades – Sensor Team Piezo-resistive Sensing – Conclusion • Not Recommended • Ideal placement is blade exterior • Temperature change affects data collection • Possible weather damage to sensor • Required, potentially bulky equipment • Power source • Data collection device / Wireless emitter • Uses • Only designed for pressure and force data collection • Recommendation • Use a sensor that is more versatile

19. ME 580 – Smart Wind Turbine Blades – Sensor Team Fiber Optic Sensors

20. ME 580 – Smart Wind Turbine Blades – Sensor Team Fiber Optics

21. Glass Cores Plastic Cores ME 580 – Smart Wind Turbine Blades – Sensor Team Types of Cores

22. Cladding material less dense than core material. The critical angle is less than the angle of incidence for the core and cladding combination. ME 580 – Smart Wind Turbine Blades – Sensor Team Total Internal Reflection

23. Essentially passive Immune to Electrical Interference Low Weight Flexibility Long Transmission Distances Low Material Reactivity Electrical Insulation Electromagnetic Immunity Multiple Sensor Multiplexing Multi-Functionality Good in Harsh Environments Capable of Fitting in Small Areas ME 580 – Smart Wind Turbine Blades – Sensor Team Fiber Optic Sensor Pros

24. ME 580 – Smart Wind Turbine Blades – Sensor Team Fiber Optic Sensor Cons • Expensive • Need: • Fiber optic cable • Polarized light emitter • Interrogator Unit/Receiver • Newer Technology • Not time tested • Limited Availability • Few suppliers

25. Strain Displacement Vibration Temperature Leak Detection Pressure ME 580 – Smart Wind Turbine Blades – Sensor Team Sensing Capabilities

26. ME 580 – Smart Wind Turbine Blades – Sensor Team Sensing Capabilities

27. ME 580 – Smart Wind Turbine Blades – Sensor Team FBG Working Principle • Sensors created by Fiber Bragg Grating • An intense UV source “inscribes” a periodic variation of refractive index into the core of an optical fiber. A special germanium-doped silica fiber is used due to its photosensitivity. • Variations in the fiber change the reflected and transmitted response within the optical fiber. The fiber responds to strain and temperature initially, and different orientations allow for multiple sensing options.

28. ME 580 – Smart Wind Turbine Blades – Sensor Team Fiber Bragg Grating

29. ME 580 – Smart Wind Turbine Blades – Sensor Team Strain Measurement

30. ME 580 – Smart Wind Turbine Blades – Sensor Team Bragg Grating Configurations

31. ME 580 – Smart Wind Turbine Blades – Sensor Team Types of Configurations

32. ME 580 – Smart Wind Turbine Blades – Sensor Team Sensor Multiplexing Multiple Functions

33. ME 580 – Smart Wind Turbine Blades – Sensor Team Data Collection and Utilization • Data Collection Options • Slip Ring • Brushless Slip Ring • Rolling Ring • Liquid Filled Slip Ring • Wireless

34. ME 580 – Smart Wind Turbine Blades – Sensor Team Data Collection • Brushless Slip Ring • Continuous Data Collection Ability • Improved lifespan • Rolling Contacts reduce friction, reduce wear • Minimizes wire tanglage • HoneyBee Robotics

35. ME 580 – Smart Wind Turbine Blades – Sensor Team Recommendations • Test sleeve made from combination of PVDF film and fiber optic sensors. • PVDF film senses wind loading. • Fiber Optic Sensors acquire resulting strains/stresses on blade.

36. ME 580 – Smart Wind Turbine Blades – Sensor Team Recommendations • Lab testing • Cantilever beam distributed load • Include tension and compression • Consider bank of hydraulic actuators applying load conditions, and perhaps even a cam system to apply concurrent vibration

37. ME 580 – Smart Wind Turbine Blades – Sensor Team Questions?