numerical site calibration on a complex terrain and its application for wind turbine performance...

Numerical Site Calibration on a Complex Terrain and Numerical Site Calibration on a Complex Terrain and its Application for Wind Turbine Performance Measurementsits Application for Wind Turbine Performance Measurements

Toshiyuki SANADA Toshiyuki SANADA (Mechanical Engineering Science, Kyushu University, Japan) (Mechanical Engineering Science, Kyushu University, Japan)

EWEC06 (2006.2.28, Athens)

Masatoshi FUJINOMasatoshi FUJINO

Daisuke MATSUSHITADaisuke MATSUSHITA

Takanori UCHIDATakanori UCHIDA

Hikaru MATSUMIYAHikaru MATSUMIYA

Masao WATANABEMasao WATANABE

Yoshinori HARAYoshinori HARA

Minori SHIROTAMinori SHIROTA

Supported by NEDO (New Energy Development Organization)Standardization research of wind turbine in Japan

Fluid Dynamics Lab, Kyushu University

Outline 1Outline 1

Numerical Site CalibrationNumerical Site Calibration

Reference meteorological mast

Wind Speed at a wind turbine

Wind speed Meteorological mast

CFD (Computational Fluid Dynamics)

EWEC06 (2006.2.28, Athens)

A pair of masts

Outline 2Outline 2

Flow Correction Factor due to Complex TerrainFlow Correction Factor due to Complex Terrain

LES

GIS

Prediction of wind speedPrediction of wind speed

Wind Turbine Performance Wind Turbine Performance MeasurementsMeasurements

EWEC06 (2006.2.28, Athens)

0 1000 2000 3000

4

6

8

10

time [s]

win

d sp

eed

[m/s

]

measured prediction

0

100

200

300

400

500

600

700

0 5 10 15 20

measured designed

P (

kW)

UWT

(m/s)

Meteorological mast

IntroductionIntroduction

~ Wind Turbine in Japan ~~ Wind Turbine in Japan ~

Ratification of Kyoto Protocol

Renewable Portfolio Standard (RPS) Law 　

Renewable energy

1.35% of total electricity supply(2010)

Wind powerWind power

March, 2004 926 MW

2010 3,000 MW (the official government target)

2030 11,800 MW (the new target of JWPA)

Complex terrainComplex terrain, Typhoon, Turbulence, Gust, Thunder storm …

almost 1/10 of Germany’s !!almost 1/10 of Germany’s !!

Challenges for Japanese wind turbine developmentChallenges for Japanese wind turbine development

Prediction of wind power generation

Wind Turbines in JapanWind Turbines in Japan

Complex TerrainComplex Terrain

mountain area 73% planes 14%

50% of the people live in plains.

Wind Turbine Performance Wind Turbine Performance MeasurementsMeasurements at Complex Terrain at Complex Terrain

for Japanese wind turbine developmentfor Japanese wind turbine development

for next step…for next step…


~ Wind Turbine in Japan ~~ Wind Turbine in Japan ~

Performance MeasurementsPerformance Measurements

たかしま D

H2 H1

H1=H2

V1V2

L=2~4D (with in the measurement sector)

V1=V2

wind speed at reference

mast 　　 = wind speed at wind turbine

wind speed not influenced by wind turbine

Example

requirement of high accuracy in measuring wind speed

IEC61400-12-1


Site Calibration Complex Terrain

Flow correction factor Flow correction factor (=the wind speed at the wind turbine location divided by the wind speed at the meteorology mast)

H2

H1H1=H2

V1V2


たかしま

V1= f (V2)

the posi tion where WTGS i s scheduled to be set up.

Test site requirementsTest site requirements (topographical variations)

・Maximum slope <5%　（ between 2L and 4L）

・ Eliminate the direction > 0.02 in between neighboring sector

・ Each wind direction bin, no larger than 10°IEC61400-12-1


V1=V2

Wind Turbine Performance MeasurementsWind Turbine Performance Measurements

Imamura et al. (EWEC01)

• Complex terrain that fails to satisfy the IEC standard

• Two points correlation analysis (before WT is constructed)

• Correlation equation using 10miniuts average.

• Direction with high correlation

(eliminate the direction with high turbulent intensity)

After measurements….,After measurements….,

If there is no direction with high correlation?If there is no direction with high correlation?

COSTCOST

RISKRISK


Site Calibration Japan

ObjectiveObjective

• To propose a numerical site numerical site calibrationcalibration, which employs CFD for wind field simulation over a complex terrain to evaluate flow flow correction factorcorrection factor.

MethodsMethodsMeasurements

Numerical Analysis

H2

H1H1 = H2

V1

V2


たかしま

V1= f (V2)

1

3

• To measure the wind speed at reference mast

• To calculate the flow correction factor using CFD

• To correct the wind speed using • To evaluate the wind turbine performance

V1=V2V2

たかしま

(x2, y2, z2)

(x1, y1, z1)V1

CFD(Computational Fluid Mechanics)

2

V1=V2

Numerical AnalysisNumerical Analysis

RIAM-COMPACT (Uchida & Ohya, 1999, 2003)

LES (Large Eddy Simulation)Grid scale vortex : Navier-Stokes Eq.

Sub-grid scale vortex : model

Nonlinear, Unsteady simulation ! Nonlinear, Unsteady simulation !

time series analysistime series analysis

• correlation

• turbulent intensity

etc…

coordinate system generalized curvilinear coordinate

variable arrangement collocated arrangement

discretization method finite-difference method

coupling algorithm fractional step method

time advancement method Euler explicit method

poisson equation for pressure

SOR method

convective terms3rd-order upwind scheme based on an interpolation

method (=0.5)

other spatial derivative term 2nd-order central scheme

SGS model Smagorinsky model + wall damping function

boundary condition

inflow 1/7 power low

top and side free-slip

outflow convective outflow

ground no-slip

Numerical AnalysisNumerical Analysis

Digital MapDigital Map

GIS (Geographic Information System) techniqueGIS (Geographic Information System) technique

aero-photograph

aero-photograph

Wind turbine performance measurements

Numerical simulation of wind turbine scale

Digital map of wind turbine scalec.f. GSI map (50m, most commonly used)

Printed atlas

CAD data

Computational GridComputational Grid 160 x 160 x 60

Test Site Test Site ~takashima~~takashima~

Point DistanceHeight

differenceMean slope

O-A 50m 25m 50%

O-B 75m 25m 33%

O-C 62.5m 25m 40%

Distance Maximum slope

<2L <3%

≥2L and <4L <5%

≥4L and <8L <10%

N

fails to satisfy the IEC standard : fails to satisfy the IEC standard : test site requirement site calibrationtest site requirement site calibration

topographical variations

Measurements Measurements

mast1: reference mast

mast2: for validity check

N

L=5.13D

Spatial configuration of WT & mast

Wind Characteristics Wind Characteristics

0

0.05

0.1

0.15N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

0

2

4

6

8

10N

NNE

NE

ENE

E

ESE

SE

SSES

SSW

SW

WSW

W

WNW

NW

NNW

0

0.1

0.2

0.3

0.4N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

mast1 mast2

Wind RoseWind Rose Average Wind Speed Average Turbulent Intensity Average Wind Speed Average Turbulent Intensity

[%] [m/s] [%]

NW, N, SNW, N, S

N

1st, April, 05 ~ 30th, November, 2005

How to define the flow correction factor ?

• time series of wind speed of each points

ExampleExample, North windWTM1

N

mast 1

WT

z=M1

Condition: 5m/s, 10m/s, 15m/s, 10minuts

Correction FactorCorrection Factor

• 10 minutes averaged value (corresponding to 10 minute data set)

Uncertainly analysis

1 β MWT UU

22.1

22.1 1

MWT UU

regression line (minimum mean square method) 　

0

5

10

15

20

0 5 10 15 20

N

UWT(m

/s)

UM1

(m/s)

correlation coefficient : high

However …



2 4 6 8 10 12 14 16 180

0.2

0.4

0.6

0.8

UM1

(m/s)

PDF

(a)

2 4 6 8 10 12 14 16 180

2

4

6

UWT

(m/s)

PDF

(b)

uU

U

M

WT βi,1

i,

mast 1 WT

u=N(0, 2): component of variation from average wind speed

0

5

10

15

20

0 5 10 15 20

N

UWT(m

/s)

UM1

(m/s)

Uncertainly analysis

Assumption: bivariate normal distribution Assumption: bivariate normal distribution


• confidence interval 95% (±1.97)

evaluation of correction factor

β2α

error of UWT

0

5

10

15

20

0 5 10 15 20

N

UWT(m

/s)

UM1

(m/s)

=1.2241=0.1585

In this case,

=21%

High accuracy in measuring wind speed is required.



The power is approximately proportional to wind speed to the third power.

Results ~Results ~ NNORTHORTH W WESTEST ~~ N

NWFlow FieldFlow Field

y=WT

y=M2

M1 WTM2

mast2: large Uz components

Mast1 & WT: flow smooth

y z

N

NW

regression analysis

=0.6%

Good direction for WT performance measurements

0

5

10

15

20

0 5 10 15 20

NW

UWT(m

/s)

UM1

(m/s)

=1.0590=0.0032

Results ~Results ~ NNORTHORTH W WESTEST ~~

Flow Correction FactorFlow Correction Factor

=1.059

N

NW

validity check : mast 1 & mast 2

Measurements (10min data-set) Calculation

12 078.1 mastmast UU

cup vs. cup

over estimation?

0

5

10

15

20

0 5 10 15 20

NW

UM2(m

/s)

UM1

(m/s)

=1.0477=0.0030

Results ~Results ~ NNORTHORTH W WESTEST ~~

Validity CheckValidity Check

y=M2

NNResults ~Results ~ NNORTHORTH ~~

Flow Field

z=mast1 z=mast1

Flow FieldFlow Field

M1 WTM1 WT

NN

regression analysis

0

5

10

15

20

0 5 10 15 20

N

UWT(m

/s)

UM1

(m/s)

=1.2241=0.1585

=21%

Poor direction for WT performance measurements

=1.2241

Results ~Results ~ NNORTHORTH ~~


Results ~Results ~ SSOUTHOUTH ~~ N

SFlow Field

M1

WT

z=WT y=WT

Flow FieldFlow Field

WT

N

S

regression analysis

0

5

10

15

20

0 5 10 15 20

S

UWT(m

/s)

UM1

(m/s)

=1.0844=0.0053 =1.0%

Good direction for WT performance measurements

Results ~Results ~ SSOUTHOUTH ~~


=1.0844

0

5

10

15

20

0 5 10 15 20

S

UM2(m

/s)

UM1

(m/s)

=0.4056=0.1070

What happen at the Mast 2 ?

M2WT

Siting of Meteorological mast

0

0.1

0.2

0.3

0.4N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNWResults ~Results ~ SSOUTHOUTH ~~


Turbulent Intensity

=53.0% !!

Power PerformancePower Performance ~ NORTH WEST ~~ NORTH WEST ~

N

NW

0

5

10

15

20

0 5 10 15 20

NW

UWT(m

/s)

UM1

(m/s)

=1.0590=0.0032

0

100

200

300

400

500

600

700

0 5 10 15 20

North West

design

UM1

UWT

Pow

er [k

W]

Wind Speed [m/s]

Power PerformancePower Performance ~ NORTH ~~ NORTH ~

0

5

10

15

20

0 5 10 15 20

N

UWT(m

/s)

UM1

(m/s)

=1.2241=0.1585

NN

0

100

200

300

400

500

600

700

0 5 10 15 20

North

design

UM1

UWT

Pow

er [k

W]

Wind Speed [m/s]

Power PerformancePower Performance ~ SOUTH ~~ SOUTH ~

N

S

0

5

10

15

20

0 5 10 15 20

S

UWT(m

/s)

UM1

(m/s)

=1.0844=0.0053

0

100

200

300

400

500

600

700

0 5 10 15 20

South

design

UM1

UWT

Pow

er [k

W]

Wind Speed [m/s]

ConclusionConclusion

• A site calibration by employing CFD (LES and detail digital map obtaineA site calibration by employing CFD (LES and detail digital map obtained from GIS) is proposed.d from GIS) is proposed.

• A numerical site calibration can evaluate A numerical site calibration can evaluate directionaldirectional flow correction flow correction factor.factor.

• A numerical site calibration can be applied to the wind turbine performA numerical site calibration can be applied to the wind turbine performance measurements if terrain condition and flow direction are carefully chance measurements if terrain condition and flow direction are carefully chosen.osen.

• Using numerical simulation, the appropriate direction and position of mUsing numerical simulation, the appropriate direction and position of meteorological mast for site calibration where fluctuation of wind speed is eteorological mast for site calibration where fluctuation of wind speed is small, can be chosen.small, can be chosen.

• Numerical site calibration at other sites. Numerical site calibration at other sites. (validity check) (validity check)

• Measurements of wind turbine performance at Measurements of wind turbine performance at complex terraincomplex terrain (effects of flow distortion, turbulent intensity) (effects of flow distortion, turbulent intensity)

(For Japanese wind turbine development, a performance testing of WT at complex terrain is required for prediction of electric power generation)

For FutureFor Future

NN


Calculation

0

5

10

15

20

0 5 10 15 20

N

UM2(m

/s)

UM1

(m/s)

=1.1120=0.1498

Measurements: north wind at mast1 = Calculation : north wind into island

Results ~Results ~ NNORTHORTH ~~


Measurements (10min data-set)

N

S


0

5

10

15

20

0 5 10 15 20

S

UM2(m

/s)

UM1

(m/s)

=0.4056=0.1070

Calculation

Qualitatively good agreement

Results ~Results ~ SSOUTHOUTH ~~


Measurements (10min data-set)

numerical site calibration on a complex terrain and its application for wind turbine performance...

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