There was an old lady who swallowed a fly …
(… or, how did we end up here anyway)
There was an old lady who swallowed a fly …
Limited measurement opportunities
There was an old lady who swallowed a spider …
2
∝
𝒛𝒉𝒖𝒃
Approximations to compensate
for lack of knowledge, e.g.
• Wind shear exponent,
• Turbulence intensity
1.5
Height / hub height
𝑽 𝒛 = 𝑽𝒉𝒖𝒃
𝒛
1
0.5
0
0
0.5
1
1.5
Wind speed / hub height wind speed
There was an old lady who swallowed a horse …
… she’s dead, of course.
Solutions that are over-constrained by
the original problem can lead to
bigger problems
There was an old lady who didn’t swallow a fly …
(… or, what would we do if we started from scratch)
Eolics: equally sophisticated
• Measurements
• Models of atmospheric conditions and wind turbine response
Scientific rigour and predictive power is possible
Epistemology and the eolicist
•
My knowledge is incomplete
•
The incompleteness of my knowledge extends to my
knowledge of its incompleteness
•
I don’t know what I don’t know
•
Do you know what I don’t know I don’t know?
•
We cannot predict what we can learn from each other
•
Measure, discuss, disagree … learn
Compression zone
Compression zone
© Gerrit Wolken-Möhlmann, Fraunhofer IWES
Galion G4000 Offshore
on transition piece
2 x Galion G4000 Offshore on nacelle, one facing
forward to survey inflow, one facing back for wakes
© Gerrit Wolken-Möhlmann, Fraunhofer IWES
Unit
G24
Compression
zone
Compression zone
Compression zone at 5m/s
Compression zone
105%
Normalised wind Speed (% of wind speed at 2.5D upwind)
104%
Free stream
Nacelle lidar
103%
102%
101%
5 m/s bin
6 m/s bin
100%
7 m/s bin
8 m/s bin
99%
9 m/s bin
98%
2.5D = 100%
97%
10 m/s bin
11 m/s bin
12 m/s bin
96%
95%
94%
Upwind distance from rotor (m)
Convergent scan geometries
Convergent scan geometries
Mast
TB1
Mast
TB2
Convergent scan geometries
Convergent scan geometries
Lidar Turbulence Intensity
0.4
0.35
0.3
y = 0.996x + 0.003
R² = 0.990
0.25
0.2
0.15
0.1
0.05
0
0
0.05
0.1
0.15
0.2
0.25
Mast Turbulence Intensity
0.3
0.35
0.4
The problem with turbulence intensity
Linear ramp
Random Gaussian
Transience versus Variance
m2/s2
2.2
2.1
2
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0

2
m
1 n
2
  xi  xi m 
n i 1

2
Variance
Transience, m=1
0
0.1
0.2
0.3
0.4
0.5
0.6
1

n
n
 xi
 x
2
i 1
Degree of "scatter"
0.7
0.8
0.9
1