1. No category

Boost Wind Turbine Yield
& Life Expectancy through
Rotor Blade Angle Correction
BerlinWind GmbH
IWPC 2015
Bundesallee 67, 12161 Berlin
Germany
Istanbul
Tel.: +49 30 688 3337 40
Dipl.- Ing Anke Grunwald
Managing Director BerlinWind
IWPC 2015
Istanbul
Email: [email protected]
Internet: http://www.berlinwind.com
Boost Wind Turbine Yield and Life Expectancy
trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Company Background
•  Founded in 2009, part of Corporate Energy Group Holding
•  Located in Germany, Strategic partnerships with different companies worldwide
•  Independent experts with wind energy experience since mid 1990s, member of the
expert advisory board of the German Wind Energy Association, VDI 3834 work group
•  Services (worldwide):
•  Blade angle & rotor imbalance measurements:
1200+ wind turbines (WT), 80+ WT types, 20 WT+ manufacturers
•  Load measurements: 120+ sensors and 3+ years duration
•  Consulting: technical consulting, root cause analysis,
performance optimisation
•  R&D for high-precision measurements at WT
IWPC 2015
Istanbul
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© Berlinwind GmbH 2015
Content
§  Company Background
§  Impact of wind turbine (WT) blade angle deviation (BAD) on power
curve, annual energy production (AEP) & WT health
§  Definition of absolute and relative blade angle deviation
§  Blade angle limit values – where defined and why?
§  Statistical results of blade angle measurements at 277 WT
§  Blade angle measurement and adjustment
§  Power curve improvement through blade angle adjustment
§  Cost-Benefit-ratio of blade angle measurements and WT rotor
balancing
§  Conclusions
IWPC 2015
Istanbul
Boost Wind Turbine Yield and Life Expectancy
trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Negative Impact of Blade Angle Deviation
on the WT Power Curve (schematic diagram)
Power
inLkW
Elektrische eistung in MW
Design-­‐
Leistungskurve
2000
Design power curve
1500
Blade misalignment to feather
Blade misalignment to stall
1000
To feather
Wind
DesignBlade angle
To stall
500
Feathering
position
WT design defines
Fehljustiert nach blade
optimum
design
Fahne
angle to achieve
* design
power
Fehljustiert nach curve and
Stall
* design
loads
Lowered power curve
means lower AEP
Misalignment “to stall”
may slightly increase
power curve at lower
winds, but strongly
reduces power output at
higher winds &
significantly increases
vibration-related damages
for Pitch-controlled WT
0
4
6
8
10
12
14
16
18
20
22
Windgeschwindigkeit in m/s
Wind speed
IWPC 2015
Istanbul
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trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Significant AEP loss from
absolute blade angle deviation
AEP loss, production loss
30%
10% power output reduction per 1.0°
Analytical e stimation f or Pitch WT in the range below rated wind speed using wind tunnel profile data
25%
7,4% AEP loss per 1,0°
Field result for a wind farm with 10 x 1.5 MW WT.
Estimation from 2 yrs operational data and measurement of absolute blade angles. Mean yield loss compared to owner's reference WT ( including stand still losses)
20%
15%
10%
Drawn range of AEP loss AEP loss due to blade angle deviation depends on further parameters, e .g. WT type, number of misaligned
blades, site influences, e .g. wind regime, etc.
5%
0%
0,0
IWPC 2015
Istanbul
0,3
0,6
0,9
1,2
1,5
1,8
2,1
2,4
2,7
Mean absolute blade angle deviation w.r.t design blade angle in degree
Boost Wind Turbine Yield and Life Expectancy
trough Rotor Blade Angle Correction
3,0
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© Berlinwind GmbH 2015
Negative Impact of Blade Angle Deviation
on WT Health
Increase of
§  Vibration amplitudes
§  Fatique loads
§  Life time consumption
§  OPEX (from damages and
downtime)
Picture 4
Picture 1
Picture 2 Picture 3
Picture 2
IWPC 2015
Istanbul
(1) Cracks in trailing edge
(2) Cracked blades due to Rotor Imbalance and
Stall-induced vibrations
(3) Extensive wear of yaw brakes
(4) Cracked main frame
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trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Consequences of blade angle deviation:
Foundation damages at a Multi-MW WT
Normalized vibration amplitude @ rotor frequency (normalized per direction with final values)
65 60 55 50 45 40 35 30 25 20 15 10 5 -­‐
65,1 53,0 30,6 5,2 1,3 1,0 1,5 2,0 1,0 Initial state: intolerable BAD 5.8° (= 12* rel. BAD limit = 19 * abs . BAD limit); intolerable mass imbalance 1.7 * limit
Step1 -­‐ 1st blade angle correction: one blade at 0.5° (rel. BAD limit) one blade at 0.2°; intolerable mass imbalance 1.7 * limit
Step 2 -­‐ 2nd blade angle correction: all blades below abs .BAD limit; intolerable mass imbalance 1.7 * limit
Step 3 balancing to final state: Below abs. BAD limit, below mass imbalance limit
1,5 2,8 1,0 axial
lateral
torsional
Masuring direction of tower-­‐nacelle vibration
IWPC 2015
Istanbul
Many of these foundation cracks after 1 yr Boost Wind Turbine Yield and Life Expectancy
trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Definition Blade Angle Deviation (BAD) &
Limit Values
Absolute Blade Angle Deviation (BAD):
Difference to design blade angle, mainly responsible for AEP loss
Relative Blade Angle Deviation:
Difference between individual blades of a rotor, mainly
responsible for increased vibrations
Absolute BAD
Physical facts: Blade angle deviation (BAD) increases
asymmetric rotor forces and thus increases operational loads
and the related lifetime consumption of all WT components
Consequence: WT design standards and guidelines
require for SAFETY REASONS definition of the tolerable
absolute BAD and its inclusion in the operational load simulation
for fatigue load analysis for the design service life (IEC 61400-1,
DNV GL, DIBt - German type approval code)
Tolerable absolute blade angle deviation (absolute BAD)
with respect to the (OEM) design reference design angle:
* DNV-GL guideline: +/- 0,3°,
* OEM: sometimes tighter limits, e.g. +/-0,25°
* Limit value for relative BAD typically derived from absolute BAD
limit: 0,5 - 0,6°
IWPC 2015
Istanbul
Relative BAD
“Design”
Design Blade
angle
Boost Wind Turbine Yield and Life Expectancy
trough Rotor Blade Angle Correction
“Field”
Lift coefficient,
lift force
BAD to stall
cL.opt ≈ 1,0
ΔcL
Causes lift
force
difference
Lift curve
Δα Blade angle
deviation
αA.opt
Blade angle, αA
angle of attack
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© Berlinwind GmbH 2015
Absolute Blade Angle Deviation (BAD)
of 831 individual Blades of 277 WT
(with and without known BAD issues)
79% of measured blades exceed limit for absolute BAD
…to feather
Design
Blade angle
… to stall
Method:
Feathering
position
•  Independent, statistically
safe photometric blade angle
measurement
•  Mean absolute BAD: -0.34°, Standard deviation 1.9°
•  Worst cases: -8.8° und + 11.8°
•  on average two or more affected blades per rotor
IWPC 2015
Istanbul
•  BAD of 277 WT measured
(average 2 MW, with and
without without known BAD
issues, i.e. several
completely checked wind
farms included)
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trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Absolute Blade Angle Deviation (BAD)
of 277 WT Rotors
(with and without known BAD issues)
IWPC 2015
Istanbul
Max. absolute BAD per rotor
Share
Within limits, < |0.3°|
7%
> 2.0 * limit = |0.6°|
76%
> 3.5 * limit = |1.1°|
50%
> 6.0 * limit = |1.8°|
25%
> 18.0 * limit = |5.4°|
5%
Boost Wind Turbine Yield and Life Expectancy
trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Shares of WT affected by Blade Angle
Deviation (BAD) and/ or Mass Imbalance
(without known BAD or Imbalance issues)
73% of all WT are affected by intolerable BAD
and/or Mass Imbalance
Method:
•  Relative blade angle and
mass imbalance
measurements of 239 WT
(without known BAD or
imbalance issues)
•  Combination with statistics of
absolute BAD measurements
IWPC 2015
Istanbul
Boost Wind Turbine Yield and Life Expectancy
trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Was sind die Folgen?
Costly consequences of blade angle
deviation
including
impact on MI
Turmund Gondelschwingungen
einer WEA
Mass
imbalance
Massenunwucht
Damages
Schäden
Stillstandszeiten
Stand still
Blade angle deviation
Aerodynamische
Unwucht
Loss of AEP
Effizienzverluste
Noise issues
Schallemission
aerodynamisc
Beide verursa
die wirtschaftli
dauerverkürzu
nach sich zieh
Weiterhin min
den Ertrag und
Falsification of mass imbalance
measurements (wrong results + action)
Logic consequence: Always measure and correct blade angles before
performing any mass balancing of WT rotor
IWPC 2015
Istanbul
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trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Blade Angle Measurement & Adjustment
Recording a series of photos
Statistical Evaluation
Blade angle
deviation?
Yes
Blade angle limit,
Design blade angle
Vibration measurement
for quality control and
mass imbalance check
No
Blade
Adjustment
Vibration measurement
of WT’s initial state
Independent optical measurements at blade contour
Examples (1) camera-based photometric or (2) distance laser-based
optical blade angle measurement with expert software
+ Statistical evaluation reveals random errors
+ Absolute, relative blade angle and twist measurement possible
+ Verification of BA correction by vibration measurement for QC
IWPC 2015
Istanbul
Boost Wind Turbine Yield and Life Expectancy
trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Zero-degree marks? -Trust only
measurements at the blade contour
Zero degree marks
•  May be misplaced, difficult to use
or even missing
•  no blade twist control
IWPC 2015
Istanbul
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trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Power curve improvement through
absolute blade angle adjustment
1500
1500
7%
NACH BW-­‐Justage After blade
adjustment
Before
adjustVOR BW-­‐Justage 1200
6%
ment: 2years
5%
1050
Leistung n kW
Power
in ikW
900
4%
Power Leistungszunahme output increase
BW-­‐Justage after NACH BA adjustment
750
3%
600
450
2%
300
Comparison
of three power curves from
Vergleich der Leistungskurven operational
data of identical
seasonal
im gleichen jahreszeitlichen Abschnitt
section for the adjusted WT
150
Leistungszunahme je Klasse in %
Mean
absolute
BAD
ofdes Rotors: rotor: -0,7°
Mittlerer
abs. BW-­‐
Fehler -­‐0,7°
Relative power output increase
per wind class in %
1350
1%
0
0%
4
5
6
7
8
9
10
11
Mittl. Windgeschwindigkeit in m/s
12
13
14
15
Classified mean wind speed m/s
IWPC 2015
Istanbul
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trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Case study: overall Cost-benefit ratio of
blade angle correction and balancing
IWPC 2015
Istanbul
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trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Conclusions
§  Only a minority of WT have correctly adjusted blade angles
§  Large share of faulty adjustments prove that
typical production and commissioning
procedures are not sufficient
§  Neglect will result in huge yield losses and
damage costs
§  Blade angles can be re-adjusted to the
optimum design angle
§  Effective measurements and corrective
measures cost much less than prevented
yield loss and damages
Blade Angle correction is an essential tool
to boost AEP and life expectency and
lower OPEX!
IWPC 2015
Istanbul
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trough Rotor Blade Angle Correction
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© Berlinwind GmbH 2015
Thank you for your attention!
BerlinWind GmbH
Bundesallee 67, 12161 Berlin,
Germany
Tel.: +49 30 688 3337 40
Email: [email protected]
Internet: http://www.berlinwind.com
IWPC 2015
Istanbul
Boost Wind Turbine Yield and Life Expectancy
trough Rotor Blade Angle Correction
18 / 18
© Berlinwind GmbH 2015