nikolaos stefanatos laboratory for wt testing (lwtt) ewec 2006- athens verification of power...

EWEC 2006- Athens Nikolaos StefanatosLaboratory for WT Testing (LWTT)

VERIFICATION OF POWER PERFORMANCE OF ACTIVE POWER CONTROL

WIND TURBINES IN COMPLEX TERRAIN

N. Stefanatos, F. Mouzakis, E. Binopoulos, F. Kokkalidis, P. Papadopoulos

Centre for Renewable Energy Sources (CRES) Wind Energy Department

Laboratory for Wind Turbine Testing (LWTT)


Share the experience – respect confidentiality

Verification of power performance in complex terrain

•The Laboratory for Wind Turbine Testing (LWTT) of CRES is a Testing Laboratory accredited by DAP GmbH according to ISO/IEC 17025 for wind turbine power performance measurements (and others).

•Numerous verifications of power curve in complex terrain sites have been successfully completed by CRES-LWTT

•Valuable experience gathered, but is commercially confidential

•Lets talk Confidential:

No site names

No wind turbine types

Non-dimensional results


Method-Standards applied

•IEC 61400-12:1998

•MEASNET Power Performance Procedure Ver. 3/2000

•IEC 61400-12-1:2005 requirements regarding instrumentation properties and positioning fulfilled

•Additional features

Shear profiles measured at reference mast and at wind turbine position



CASE P1

-Pitch controlled

-Fairly complex (terrain inclination typical 10%)

-Only site calibration and shear results available

CASE P2 •Pitch controlled •Semi-flat terrain (terrain inclination typical 4%)•Power curve measurement campaign complete

Overview of Cases studied (no photos, sorry..)



Overview of Cases studied (no photos, sorry..)


- CASE P3 •Pitch controlled •Very complex terrain (terrain inclination typical 20% and higher)•Power curve measurement campaign complete

CASE S6 •Stall controlled •Extreme complex terrain (terrain inclination typical 40%)•Velocity ratios direction and velocity sensitive•Power curve measurement campaign complete

•5 STALL CONTROL CASES Summary results from 5 older stall controlled cases also included


-10 0 10 20 30W in d d ire ctio n (d e g ) - re f.

0 .95

1

1.05

1.1

1.15

1.2

1.25

Vw

t/Vre

f

4 -16 m /s

4 to 8 m /sec

8 to 16 m /sec


Know your site (1) : Velocity ratios

CASE P1Fairly complex terrain case

(10% inclination)

Limited dependence of velocity ratios to mean wind speed

CASE S6Extreme complex terrain case

(40% inclination)

Strong dependence of velocity ratios to mean wind speed

320 330 340 350 360D ire ctio n (d e g )

0.95

1.00

1.05

1.10

1.15

1.20

1.25

Vw

t/Ure

f

4 to 8 m /s

8 to 16 m /s

4 to 16 m /s


Know your site (2) : Turbulence

0 4 8 12 16 20V (m /se c)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Tu

rbu

len

ce in

ten

sity

P 1, fa irly com plex

P2, sem i-fla t

S6, extrem e com plex


Mean Turbulence levels in complex

terrain sites may vary significantly

(eg. from 7% to 20%)


0.7 0.8 0.9 1 1.1V /V o

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Z/Z

o

C ase P1

C ase P2

C ase P3

C ase S6

R EF-m ast (4-16 m /s)

0.7 0.8 0.9 1 1.1V /V o

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Z/Z

o

C ase P3

C ase S6

W T-m ast (4-16 m /s)


Know your site (3) : Shear

Shear ratio from 0.80 to 0.92

Inverse shear at w/t position for one case



Case P2 – Semi flat

Terrain inclination: 4%Velocity ratio :1.01

ΔΑΕP=-0.45%

Case P3 – Very complex

Terrain inclination: 20%Velocity ratio: 1.17

ΔΑΕP=1.78 %

Results (1) : The good, the perfect and…

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2

V /Vnom

P /P

no

m

Measured

Warranted

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2

V/Vnom

P /P

no

m

Measured

Warranted



Case S6 – Stall, extreme complex

Deviations

Velocity dependent site calibration factors

Working sector extended to NON-MEASNET complete direction bins to gain high wind speed bins

Warranted power curve not measured (optimised for site specific air density and wind speed annual distribution)

Terrain inclination: up to 40%Velocity ratio:1.03

ΔΑΕP= - 10.9%

Results (2) : … and the stall controlled

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2

V /Vnom

P /P

no

m

Measured

Warranted


Verification of site calibration – Case S6 -ExtremeConventional site calibration Velocity-dependent s.c


0.0 0.4 0.8 1.2 1.6 2.0V/Vn o m

0.0

0.4

0.8

1.2

P/P

no

m

Com bined power curve

North sector (345-15deg)

South sector (155-177deg)

0.0 0.4 0.8 1.2 1.6 2.0V/Vn o m

0.0

0.4

0.8

1.2

P/P

nom

Com bined power curve

North sector (345-15deg)

South sector (155-177deg)

Direction sensitive power curve

Verification failed

No direction effect on power curve

Verification successful



Effect of mast base altitude height difference on velocity

ratio

Small AEP deviation regardless of the Velocity ratio

(for 5 stall cases also)

y = 6.0011x - 3.0298

R2 = 0.0113

-30

-20

-10

0

10

20

30

40

0.95 1 1.05 1.1 1.15 1.2

VR mean

AB

S (

ΔA

EP

), %

Results 3 – Sensitivity analysis (or “stall control can be OK too…)

y = 0.1772x + 1.0002

R2 = 0.5971

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2

-0.20 0.00 0.20 0.40 0.60 0.80

Altitude difference/Diameter

VR

mea

n



Turbulence intensity : Limited effect

Mast distance : No effect (within the IEC limits)

y = -1.5443x + 7.6198

R2 = 0.0537

-30

-20

-10

0

10

20

30

40

1.50 2.00 2.50 3.00 3.50 4.00

Mast distance/DiameterA

BS

(Δ

AE

P),

%

y = 67.798x - 4.1857

R2 = 0.1784

-30

-20

-10

0

10

20

30

40

0.05 0.07 0.09 0.11 0.13 0.15

TI

AB

S (

ΔA

EP

), %

Results 4 – Sensitivity analysis (or “stall control can be OK too…)


Lets get dimensional again

Assume

10 MW wind farm

8 m/s Annual mean wind speed

kWh price : 0.075 EUROs

10% less AEP

Income lost per year: 200 kEUROs

(many times the cost of a power curve verification campaign…)


Terrain inclination: up to 40%Velocity ratio:1.03

ΔΑΕP= - 10.9%

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2

V /Vnom

P /P

no

m

Measured

Warranted


Wide variety of flow conditions in complex terrain – not always bad

Current methods adequate to give reliable results even in difficult

cases

Extreme cases do exist and require additional attention

Verification and cross-check procedures very important

“A power curve verification campaign may prove to be

a very good investment”


Conclusions

nikolaos stefanatos laboratory for wt testing (lwtt) ewec 2006- athens verification of power...

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