20151202 optiwind design validation-optimization-wp5-foundation-monitoring-wp7-vub
TRANSCRIPT
Design valida,on & op,miza,on of offshore founda,ons
Founda,on monitoring on offshore wind farms for O&M op,miza,on and life ,me extension
&
Wout Weijtjens Vrije Universiteit Brussel / OWI-‐lab
Work packages
Our Op-wind Team
Prof. dr. ir. Christof Devriendt [email protected]
ir. Nymfa Noppe [email protected]
ir. Tim Verbelen ,[email protected]
MEng. Alexandros Iliopoulos [email protected]
dr. Rasoul Shirzadeh Has leT the department
dr.ir. Wout Weijtjens [email protected]
Problem descrip,on
Offshore wind turbines are pushing boundaries -‐ Monopile design remains dominant ( > 90% ) -‐ Growing mismatch between lab and real-‐life -‐ Diameters of 7-‐8 m -‐ 6-‐7 MW machine on Monopile -‐ 1200 ton weight
Meanwhile the designs remain fa-gue driven
Problem descrip,on
There is a known mismatch between design assump,ons and real life condi,ons which directly affect fa-gue life!
-‐ Uncertain,es in the soil models
Problem descrip,on
There is a known mismatch between design assump,ons and real life condi,ons which directly affect fa-gue life!
-‐ Uncertain,es in the soil models
E.g. PISA project in UK (led by DONG energy)
Problem descrip,on
There is a known mismatch between design assump,ons and real life condi,ons which directly affect fa-gue life!
-‐ Uncertain,es in the soil models -‐ Unknown damping behavior
Problem descrip,on
There is a known mismatch between design assump,ons and real life condi,ons which directly affect fa-gue life!
-‐ Uncertain,es in the soil models -‐ Unknown damping behavior
-‐ Hydrodynamic loads on very large cylinders
E.g. WiFi JIP project in NL
Problem descrip,on
There is a known mismatch between design assump,ons and real life condi,ons which directly affect fa-gue life!
-‐ Uncertain,es in the soil models -‐ Unknown damping behavior
-‐ Hydrodynamic loads on very large cylinders
E.g. WiFi JIP project in NL
Problem descrip,on
What with already built farms? ! uncertain,es have led to overdesign
Poten,al room for life ,me extension or repowering
Resonance frequency shiT Operator / Developer driven ques-on:
Were the as designed frequency values correct?
WP5
Resonance frequency shiT Operator / Developer driven ques-on:
Design valida-on : Were the as designed frequency values correct?
WP5
Resonance frequency shiT Operator / Developer driven ques-on:
Were the as designed frequency values correct?
As designed frequencies for first mode differ with about 5-10%!
WP5
Resonance frequency shiT Operator / Developer driven
Stiffer than designed is not Necessarily a good thing
Direct impact on design of Northwind and Nobelwind -> New O&O
Most likely cause > Soil!
WP5
O&M : Scour assessment
Use design valida,on set-‐up To check if the resonance Frequencies are s,ll within an Acceptable range
! Currently overcompensated by the s-ffer soil
WP7
Blue: May 2012 Green: November 2013 Red: model
500 1000 1500 2000 25001.38
1.4
1.42
1.44
1.46
1.48
1.5
1.52
Res
onan
ce F
requ
ency
(SS
2) (H
z)
Time 500 1000 1500 2000 2500−0.04
−0.02
0
0.02
0.04
0.06
0.08
Pred
ictio
n Er
ror (
Hz)
Time
Training Use relative error as a damage feature
Residual error leaves 3σ boundary
Prediction
O&M Monitoring Resonance Frequencies
SOIL STIFFENING?
Methodology to monitor scour by tracking the resonance frequencies
WP7
Damping values
2012 Damping Es-ma-on of an Offshore Wind Turbine on a Monopile Founda-on
-‐ Determined the damping ra,o of the turbine’s first modes aTer an overspeed stop
-‐ Use of ambient vibra,ons to determine the damping ra,o
FA : 1.04%* SS : 1.25%*
FA : 1.05%*
* With Tuned Mass Damper turned off
WP5
Damping values
2013 Monitoring of Resonant Frequencies and Damping Values of a Parked Offshore Wind Turbine on a Monopile Founda-on
A fully automated method to track the first five resonance frequencies and damping ra,os con,nuously
Resonance frequencies and damping ra-os depend on the ambient condi-ons (e.g. Wind speed, Tidal level)
WP5
Damping values
2013 Monitoring of Resonant Frequencies and Damping Values of a Parked Offshore Wind Turbine on a Monopile Founda-on
A fully automated method to track the first five resonance frequencies and damping ra,os con,nuously
Resonance frequencies and damping ra-os depend on the ambient condi-ons (e.g. Wind speed, Tidal level)
WP5
Damping values
2014 Classifying Resonant Frequencies and Damping Values of a Fully Opera-onal Offshore Wind Turbine
Resonance frequencies and Damping ra-os can shiM significantly between opera-onal condi-ons
! An es-mate for each opera-onal condi-on
WP5
Damping values
2015 Automated monitoring of five offshore wind turbines in the Belgian North Sea
Mul, algorithm technique : FDD, SSI-‐COV, polymax
Consistent behavior between turbines and over -me
WP5
Classifying the data Use par,al SCADA-‐data to classify each ten-‐minute data set into different opera-onal cases
Get results case-‐by-‐case
Case defini,ons can be updated for different applica,ons
WP5
Cau,on with Harmonics
The original algorithm will falsely iden-fy harmonics as if they are structural
! Track harmonics and reject unreliable results
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Damping Analysis of FA1 and SS1
SS1
FA1
>
WP5
Damping Analysis of FA1 (e.g. Using the SCADA-‐Windspeed)
( considering only produc6on cases)
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Damping Analysis of SS1 (e.g. Using the SCADA-‐Windspeed)
( considering only produc6on cases)
WP5
Modeling Damping Greatest disadvantage of damping determined with OMA :
Only total damping es-mated
-‐> Has almost no value for current design code!
Accounted for in ,me domain simula,on (Aero-‐ and Hydro-‐dynamic loads)
Accounted for in Structural model
Best Es,mate -‐> Need for full scale measurements!
OMA Design
WP5
Methodology to decompose in different damping contribu-ons
Mixed method that combines Simula,ons and Measurements
Modeling damping
• Loads are modeled correctly? • Soil model already ques,oned
• How to update your damping correctly • Based on solely accelera,ons might be insufficient • Impact on induced strain of different damping distribu,ons? -‐> Fa-gue
WP5
Fa,gue monitoring
• Issues revealed in modeling fa,gue loads • Mo,va,on for direct measurements and monitoring of fa,gue life!
WP7
Fa,gue monitoring Hot spot Monitoring
Stress Monitoring
Fa,gue Life Es,ma,on
Farm wide Fa,gue Life
Con,nuous measurements of the strains -‐ Bending moments at measurement loca-on
-‐ Comparison with design loads -‐ Local stress cycles
WP7
mudline
waterlevel
hotspot
sensing Virtual
Robust maintainable
sensors
WP7
Fa,gue monitoring Hot spot Monitoring
Stress Monitoring
Fa,gue Life Es,ma,on
Farm wide Fa,gue Life
Virtual sensing -‐ Stress cycles at Fa-gue cri-cal loca-on
-‐ e.g. as defined by design
-‐ Stress cycles at any loca-on -‐ Determine the actual cri-cal loca-on
WP7
Fa,gue monitoring Hot spot Monitoring
Stress Monitoring
Fa,gue Life Es,ma,on
Farm wide Fa,gue Life
Rainflow coun,ng on Virtual stress cycles
Assess damage with -‐ Appropriate S/N-‐Curves -‐ Stress concentra9on factors
Assess impact of Corrosion regime > O&M Support
The closer you get,! the faster you fatigue!
WP7
Fa,gue monitoring Hot spot Monitoring
Stress Monitoring
Fa,gue Life Es,ma,on
Farm wide Fa,gue Life
But rainflow coun,ng only gives accumulated damage in the past!
To extrapolate in 9me we need to know the link between Damage and :
-‐ Opera9onal condi9ons -‐ Environmental condi9ons -‐ Excep9onal load cases
WP7
Fa,gue monitoring Hot spot Monitoring
Stress Monitoring
Fa,gue Life Es,ma,on
Farm wide Fa,gue Life
Farm wide fa,gue assessment -‐ Extrapolate the results from the FLEET LEADERS to the en-re farm
-‐ Turbulence and Turbine interac-ons -‐ Site specific correc-on factors
-‐ Different resonance frequencies -‐ Damping values
WP7
What is next? Fleet leader concept
Instrumented Fleet leaders To predict fa,gue life in the farm
Preliminary work and IWT project proposal Nymfa Noppe
WP7
What is next? O&O Nobelwind Verifying the lessons learned from Northwind & Belwind
-‐ New design approaches were applied at Nobelwind
e.g. advanced soil modeling
( Construc,on starts Q1 2016 ) -‐ Monitoring campaign on three wind turbines
-‐ Unique setup with strain gauges on the monopile