This document describes a fiber optic sensor system called FIBRADAPT that is embedded in wind turbine rotor blades to monitor real-time loads. The goals of the system are to reduce structural loads, increase component lifetimes, and improve reliability. FIBRADAPT measures flapwise and edgewise loads and frequencies during operation. This load data can be used for residual lifetime estimation, structural health monitoring, and active control of individual blade pitch. Test installations of FIBRADAPT have shown it is capable of measuring bending moments and frequencies during turbine operation.

1. Advanced Wind Turbine Controls Input Based on
RealTime Loads Measured with Fiber Optical Sensors
Embedded in Rotor Blades
ewec 2006, Athens
28 February
S. Kuhnt, J. Wernicke, R. Byars, J. Shadden (WindForce GmbH)

2. Main Issues on Wind Power
Plants
• High Operational and Maintenance Costs
• Reliability below Customer Expectation
– MTBF, MTTR
• Competitiveness of COE
• Low Insurability
• Rapid Market Development

3. FIBRADAPT™
Advanced Wind Turbine Control System
Goal
• Reduction of Structural
and Dynamic Loads
(extreme and fatigue)
• Increasing the Lifetime of
Wind Turbine Components
• Component Reliability
Improvements (MTBF,
MTTR)
• Project Controlling and
Management Parameter
• Fast Return on Investment
(ROI)
Investments in Innovation ensure Future Business Opportunities
Operational Conditions of a wind turbine

4. • Measuring of Rotor flapwise and edgewise Loads and
Frequencies during Operation
• Traceability of single Events (extreme Loads, emergency
Stop etc.)
• Traceability of fatigue Loads for residual Lifetime
Estimation
• Monitoring of Design Parameter
• Monitoring of the Component Structure for early Detection
of Damages and for determining predictive Maintenance
Targets

5. Installed Measurement System

6. Fibre Bragg Grating (FBG)
-Benefits
• Multiple sensors in a single Fibre
– Simple Connectivity, low Sensor Mass
• No EMI with other operational Systems
• Higher Measurement Quality and Stability
– Solid state Electronics
– Lifetime Operation
• High Reliability of Sensors
No EMI, no Corrosion, high Reliability

7. Control Interface Electronics
Specification Value
Range +/- 4000 microstrain range
Resolution 0.8 microstrain
Repeatability (short term) +/- 5 microstrain
Repeatability (long term) +/- 10 microstrain
No of Sensors 100 per channel
Maximum sensor distance > 2 km
Scan Frequency 25 Hz for 20 Sensors
Power Requirement 12 V @ 0.25 A Typical (3W-12Wl)
Interface Ethernet, CANBus, RS422 etc.

8. FIBRADAPT:
Advanced wind turbine controls

9. Residual Lifetime Estimation
Residual Lifetime
Estimation is based on
Load Cycle Counting
during the Operation of
the Wind Turbine used
for predictive
Maintenance.

10. Structural Monitoring
The Occurrence of Cracks and
Defects can be detected at an
early Stage to prevent
catastrophic Failures and
lengthy Downtimes. Data can
be also used for Ice Load
Monitoring.

11. Active Control
Real time Loads act as
in Input for Individual
Blade Pitch Control
especially for large
Wind Turbines where
the Wind is very
turbulent over the
Rotor spam.

12. Integration of FIBRADAPT

13. FIBRADAPT™
System Additional Applications
• Integration into the SCADA System
• Standard Application for Design Verifications
• Development of a Wind Park Management System
based on Load Data
• Black Box Functionality

14. Test Installation –
Application of FIBRADAPT

15. Sensor Layout in Test
Blade 1

16. Installation of FIBRADAPT during
the Production of the Blade

17. Bending Moment flapwise
50 100 150 200 250 300 350 400 450 500 550 600
Time [s]
4E+05
6E+05
8E+05
1E+06
1.2E+06
1.4E+06
BendingMoment[kNm]
Mbf_1_fos
Copyright©2005 WindForce GmbH
0 2 4 6 8 10 12 14 16 18 20
Time [s]
4E+05
6E+05
8E+05
1E+06
1.2E+06
1.4E+06
BendingMoment[kNm]

18. Flap- and edgewise Loads
during Operation
450
500
550
600
650
343 345 347 349 351 Time [s]
strain(16)[mikrostrain]
-600
-400
-200
0
200
strain(12)[mikrostrain]
Sensor16 Sensor12

19. Frequency Analysis (Turbine
Operation)
0 0.2 0.4 0.6 0.8 1 1.2
Frequenz [Hz]
3
4
FFT-Mbf
FFT_Mbf_1
FFT_Mbf_1_fos
Copyright©2005 WindForce GmbH 2004-08-12 18-40-00_fft

20. Project planning - Outlook
• Integration of FIBRADAPT into a Serie
• Development and testing of active Control Algorithms for
FIBRADAPT
• Development of Methods for controlling and operating,
based on Variables
• Development of Methods for assuring the Application
Process in Serial Production in Offshore Installations
• Development of Software for Load Monitoring and
Residual Lifetime Estimation

21. www.wind-force.com
sabrina.kuhnt@wind-force.com
Die Entwicklung wird teilweise finanziert durch Mittel aus dem PFAU Programm
der BIS Bremerhaven
WindForce GmbH wird unterstützt durch Mittel des GRW Programms des Landes Bremen
Thank you for your attention!