Sensor fusion for a blade surface-mount icing detector for wind turbines Michael J. Moser, Markus Brandner and Hubert Zangl, Graz University of Technology

Institute of Electrical Measurement and Measurement Si gnal Processing, Graz University of Technology, Aus tria

Professor Horst Cerjak, 19.12.20051

Sensor fusion for a blade surface-mount icing detec tor for wind turbines – Winterwind 2012, Skellefteå, Sweden – 7./8.2.2012

Sensor fusion for a blade surface-mount icing detector

for wind turbines

Michael J. Moser, Markus Brandner and Hubert Zangl

Institute of Electrical Measurement and Measurement Signal Processing

Graz University of Technology, Graz, Austria




Motivation• Why fusion ?





- Both capacitive and optical icing detectors have shown to work butmight have drawbacks.






• Why blade-mount ?






• Why blade-mount ?- Detect icing where it is relevant.







• Why measure , not estimate from weather conditions?







• Why measure , not estimate from weather conditions?- Get reliable information e.g. to trigger heating.




State of the Art• Weather monitoring and estimation

- Detection of icing e.g. by means of standard ice detectors






• Ultrasonic and microwave ice thickness measurement- Deterioration due to pollution is possible, power demand is high






• Ultrasonic and microwave thickness measurement- Deterioration due to pollution is possible, power demand is high

• Indirect Detection of aerodynamical changes- Loss of power generation is an indicator, detection of vibrations






• Ultrasonic and microwave thickness measurement- Deterioration due to pollution is possible, power demand is high

• Indirect Detection of aerodynamical changes- Loss of power generation is an indicator, detection of vibrations

• Measurement of rotor blade weight- Averages over entire blade surface




New Approach

• Aim #1: „Direct“ measurement




New Approach

• Aim #1: „Direct“ measurement– Measurement of icing on multiple points on the rotor blade surface




New Approach


• Aim #2: Scalability




New Approach


• Aim #2: Scalability– In principle, applicable to any surface




New Approach



• Aim #3: Low power consumption




New Approach



• Aim #3: Low power consumption– In particular: energy harvesting is feasible -> no wires




New Approach




• Aim #4: No change in aerodynamics




New Approach




• Aim #4: No change in aerodynamics – Mounted e.g. within heating foil / on or under shell coat




EMT‘s Key Competences

Which measurement principles are suitable?














Capacitive SensingEvaluation of the variable capacitance of a

measurement capacitor, modification of






- capacitor‘s geometry






- capacitor‘s geometry- permittivity of the dielectric medium






- capacitor‘s geometry- permittivity of the dielectric medium

Planar capacitor

Dielectric medium

Parallel plate

capacitor




Capacitive: Pros and Cons

+ -





�High accuracy�High resolution�Temp. Range -40°C

+ -





�High accuracy�High resolution�Temp. Range -40°C�Wireless�Low Power�Thickness measurement

+ -





x Small signal changesx Large offsets


+ -





x Small signal changesx Large offsetsx Disturbers / EMCx Ambiguitiesx Model needed


+ -




Method: Capacitance Tomography (ECT)




Capacitive Icing Detection on OHTL

Capacitive Icing Sensor forOHTL






Field Test since 2009-2011






Field Test since 2009-2011

Commercial Product since2011




Optical Icing Detection

- Make use of optical properties of ice, water and air














Optical Icing Detection: Pros and Cons

+ -





�High accuracy�High resolution

+ -





�High accuracy�High resolution�Robustness against disturbers�Selectivity

+ -






+ -x more power neededx pollution effectsx lifetime of optical components






+ -x more power neededx pollution effectsx lifetime of optical componentsx mechanical issuesx no thickness measurement




Lab Measurement Setup












Icing Experiment Results

0 500 1000 1500

3.5

4

4.5

5

5.5

6

6.5

x 104 Icing Expe rime nt

Icin

g In

dic

ato

r (a

.u.)




Summary• A capacitive measurement principle for the detection of rotor blade icing

is feasible.





is feasible.

• Capacitance Tomography methods can be applied to estimate ice layerthickness and quality.





is feasible.


• Water (melting ice layers, rain and drying) can be clearly distinguishedfrom any other state.





is feasible.



• Ice layers can be watched while growing, thickness can be determined.





is feasible.



• Ice layers can be watched while growing, thickness can be determined.

• Sensor Fusion approach: Optical icing detection can eliminateambiguities in capacitive measurement (improved ice/water discrimination)

Business

Sensor fusion for a blade surface-mount icing detector for wind turbines Michael J. Moser, Markus Brandner and Hubert Zangl, Graz University of Technology