Page 1
© ForWind
On the impact of non-Gaussian wind statistics on wind turbines - an experimental approach
Jannik Schottler, N. Reinke, A. Hölling, J. Peinke, M. Hölling
ForWind, Center for Wind Energy ResearchUniversity of Oldenburg, Germany
[email protected]
1
Page 2
© ForWind
Motivation
2
source: youtube.com
Page 3
© ForWind
Motivation
2
source: youtube.com
• wind turbines are subjected to atmospheric turbulence!
• potential impact on...
• ...power output: grid fluctuations
• ...torque: drive train failure
• ...loads: lifetime
[Carrasco et al., 2006; Sørensen et al., 2007]
[Musial et al., 2007; Feng et al., 2013]
[ Burton et al., 2001]
Page 4
© ForWind
Motivation
2
$€ - cost of energy
source: youtube.com
• wind turbines are subjected to atmospheric turbulence!
• potential impact on...
• ...power output: grid fluctuations
• ...torque: drive train failure
• ...loads: lifetime
[Carrasco et al., 2006; Sørensen et al., 2007]
[Musial et al., 2007; Feng et al., 2013]
[ Burton et al., 2001]
Page 5
© ForWind
Motivation
3
Field measurements
• expensive• limited availability• uncontrolled boundary conditions
Page 6
© ForWind
Motivation
3
Field measurements
• expensive• limited availability• uncontrolled boundary conditions
Numerics
• turbulence models• computational costs• validation?
Page 7
© ForWind
Motivation
3
Field measurements
• expensive• limited availability• uncontrolled boundary conditions
• inexpensive• controlled environment• tunable boundary conditions• upscaling?
ExperimentsNumerics
• turbulence models• computational costs• validation?
Page 8
© ForWind
Motivation
3
Field measurements
• expensive• limited availability• uncontrolled boundary conditions
• inexpensive• controlled environment• tunable boundary conditions• upscaling?
ExperimentsNumerics
• turbulence models• computational costs• validation?
validation
Page 9
© ForWind
Motivation
3
Field measurements
• expensive• limited availability• uncontrolled boundary conditions
• inexpensive• controlled environment• tunable boundary conditions• upscaling?
ExperimentsNumerics
• turbulence models• computational costs• validation?
validation
Page 10
© ForWind
Describing turbulence
4
• industry standard for wind field description:
10 min mean values, turbulence intensity TI =�u/hui
Page 11
© ForWind
Describing turbulence
4
0 2 4 6 8 104
6
8
10
12
14
time [min]
velo
city
[m/s
]
T i = 19.7%
• industry standard for wind field description:
10 min mean values, turbulence intensity TI =�u/hui
Page 12
© ForWind
Describing turbulence
4
0 2 4 6 8 104
6
8
10
12
14
time [min]
velo
city
[m/s
]
T i = 19.7%
• industry standard for wind field description:
10 min mean values, turbulence intensity TI =�u/hui
0 2 4 6 8 104
6
8
10
12
14
time [min]
velo
city
[m/s
]
T i = 19.7%
Page 13
© ForWind
Increment statistics
5
time series
Page 14
© ForWind
Increment statistics
5
⌧
time series
Page 15
© ForWind
Increment statistics
5
u⌧ := u(t+ ⌧)� u(t)velocity increment
⌧
time series
Page 16
© ForWind
Increment statistics
5
t [s]0 0.5 1 1.5 2
uτ[m
s−1]
-0.3
-0.2
-0.1
0
0.1
0.2
time series of increments
u⌧ := u(t+ ⌧)� u(t)velocity increment
⌧
time series
Page 17
© ForWind
increment PDF
uτ/στ
-5 -2.5 0 2.5 5
P(u
τ)(a.u.)
10-4
10-2
100
Increment statistics
5
t [s]0 0.5 1 1.5 2
uτ[m
s−1]
-0.3
-0.2
-0.1
0
0.1
0.2
time series of increments
u⌧ := u(t+ ⌧)� u(t)velocity increment
⌧
time series
Page 18
© ForWind
Industry standards
turbulence: Mann model (1998) / Kaimal model (1972)
6
IEC 61400-1-ED3, 2005 wind turbines, design requirements
Page 19
© ForWind
Industry standards
turbulence: Mann model (1998) / Kaimal model (1972)
6
IEC 61400-1-ED3, 2005 wind turbines, design requirements
uτ/στ
-5 -2.5 0 2.5 5
P(u
τ)(a.u.)
10-4
10-2
100
τ = 3 s
Gauss
Increment PDF according to IEC-Norm (TurbSim, Kaimal model)
Page 20
© ForWind
Industry standards
turbulence: Mann model (1998) / Kaimal model (1972)
7
IEC 61400-1-ED3, 2005 wind turbines, design requirements
[Wächter et al. 2012]
⌧ = 3 s • offshore wind data
• non-Gaussian, intermittent increments
• underestimation of extreme events
Page 21
© ForWind
Industry standards
turbulence: Mann model (1998) / Kaimal model (1972)
7
IEC 61400-1-ED3, 2005 wind turbines, design requirements
[Wächter et al. 2012]
⌧ = 3 s • offshore wind data
• non-Gaussian, intermittent increments
• underestimation of extreme events
once a year every 5 minutes!
Page 22
© ForWind
Field data vs model
8
• datasets nearly equal acc. to mean + TI
Page 23
© ForWind
uτ/στ
-15 -10 -5 0 5 10 15
p(uτ)(a.u.)
10-6
10-4
10-2
100
102
104
106
108
1010
1012
FINOKaimalGauss
1s
5s
10s
30s
60s
Field data vs model
8
• strongly different regarding increment PDF
• intermittency not reflected correctly by Kaimal model
• datasets nearly equal acc. to mean + TI
Page 24
© ForWind
uτ/στ
-15 -10 -5 0 5 10 15
p(uτ)(a.u.)
10-6
10-4
10-2
100
102
104
106
108
1010
1012
FINOKaimalGauss
1s
5s
10s
30s
60s
Field data vs model
8
• strongly different regarding increment PDF
• intermittency not reflected correctly by Kaimal model
Impact on wind turbines?
• datasets nearly equal acc. to mean + TI
Page 25
© ForWind
Setup
9
[Schottler et al., 2017]
Page 26
© ForWind
Turbulence generation
10
Page 27
© ForWind
Turbulence generation
10
0.8m
1 m
Page 28
© ForWind
Turbulence generation
10
0.8m
1 m• 16 axes w/ stepper motors
• individually tunable
• defined, turbulent flows
• reproducible:
• time series
• statistics
Page 29
© ForWind
Turbulence generation
10
0.8m
1 m• 16 axes w/ stepper motors
• individually tunable
• defined, turbulent flows
• reproducible:
• time series
• statistics
Page 30
© ForWind
Setup
11
• model wind turbine
• D=58cm
• active load control
• hot wire measurements upstream of rotor
• TSR = 7
• turbine data:
• thrust (load cell)
• torque (generator current)
• power (electric)
Page 31
© ForWind
Setup
11
0.8m
1 m• model wind turbine
• D=58cm
• active load control
• hot wire measurements upstream of rotor
• TSR = 7
• turbine data:
• thrust (load cell)
• torque (generator current)
• power (electric)
Page 32
© ForWind
Main idea
12
Inflow A) Inflow B)
Page 33
© ForWind
Main idea
12
Inflow A) Inflow B)
equal according to mean+ TI
Page 34
© ForWind
Main idea
12
Inflow A) Inflow B)
equal according to mean+ TI
Gaussian increments
Page 35
© ForWind
Main idea
12
Inflow A) Inflow B)
equal according to mean+ TI
intermittent flowGaussian increments
Page 36
© ForWind
Main idea
12
Inflow A) Inflow B)
equal according to mean+ TI
intermittent flowGaussian increments
Does the turbine ,see‘ the difference?
Page 37
© ForWind
Inflow
13
A B
[Schottler et al. 2017]
• hot wire data
• measured at rotor plane
• no turbine installed
Page 38
© ForWind
Inflow
13
A B
[Schottler et al. 2017]
• hot wire data
• measured at rotor plane
• no turbine installed
Page 39
© ForWind
Inflow
13
A B
[Schottler et al. 2017]
• hot wire data
• measured at rotor plane
• no turbine installed
Page 40
© ForWind
Inflow
14
uτ/στ
-10 -5 0 5 10
p(uτ)(a.u.)
10-10
10-5
100 Gauss
A (Gaussian)B (intermittent)
25ms
67ms
80ms (~rotor diameter)
2s
Page 41
© ForWind
Inflow
14
uτ/στ
-10 -5 0 5 10
p(uτ)(a.u.)
10-10
10-5
100 Gauss
A (Gaussian)B (intermittent)
25ms
67ms
80ms (~rotor diameter)
2s
• discrepancy between Gaussian assumption and intermittency reproduced in the lab!
• effect of properties beyond mean + TI (intermittency) isolated
Page 42
© ForWind
Turbine reaction - thrust
15
25ms (~blade length)
67ms
80ms (~rotor diameter)
2s
Page 43
© ForWind
Turbine reaction - thrust
15
25ms (~blade length)
67ms
80ms (~rotor diameter)
2s
!Gaussian inflow
Gaussian thrust
Page 44
© ForWind
Turbine reaction - thrust
15
25ms (~blade length)
67ms
80ms (~rotor diameter)
2s
!Gaussian inflow
Gaussian thrust
!intermittent inflow
intermittent thrust
Page 45
© ForWind
Turbine reaction - thrust
15
25ms (~blade length)
67ms
80ms (~rotor diameter)
2s
!Gaussian inflow
Gaussian thrust
!intermittent inflow
intermittent thrust
no ‘filtering’ of intermittency by the turbine
Page 46
© ForWind
Turbine reaction - all quantities
16
xτ / στ
-15 -10 -5 0 5 10 15
p(x
τ)/[a.u.]
100
105
1010
Gaussinflowthrustpowertorque
25ms
67ms
80ms (~rotor diameter)
2s
Page 47
© ForWind
Turbine reaction - all quantities
16
Intermittent characteristics remain present in turbine data !
xτ / στ
-15 -10 -5 0 5 10 15
p(x
τ)/[a.u.]
100
105
1010
Gaussinflowthrustpowertorque
25ms
67ms
80ms (~rotor diameter)
2s
Page 48
© ForWind
Impact on wind turbine
One second data, multi MW nearshore turbine
17
[Milan et al. 2013] [P. Milan]
Page 49
© ForWind
Impact on wind turbine
One second data, multi MW nearshore turbine
17
[Milan et al. 2013] [P. Milan]
Page 50
© ForWind
Impact on wind turbine
One second data, multi MW nearshore turbine
17
[Milan et al. 2013] [P. Milan]
Page 51
© ForWind
Thank you for your attention!
18
Funded by the Reiner Lemoine Stiftung
Further information:
Page 52
© ForWind
Load Control
19
P [W
]w
[Hz]
u [m
/s]
TSR
[-]
cp [%
]
Page 53
© ForWind
Load Control
19
P [W
]w
[Hz]
u [m
/s]
TSR
[-]
cp [%
]