Dave Corbus, Craig Hansen Presentation at Windpower 2005 Denver, CO May 15-18, 2005 Test Results from the Small Wind Research Turbine (SWRT) Test Project
Dave Corbus, Craig Hansen
Presentation at Windpower 2005
Denver, CO
May 15-18, 2005
Test Results from the Small Wind Research Turbine (SWRT) Test
Project
2SWRT Project
SWRT Test Background
• SWRT Test
•Supply data for model validation of small furling wind turbines
•Increase understanding of furling and small wind turbine dynamics
•Further state-of-the-art test procedures for small wind turbines
3.51"3.30"3.72"
3SWRT Project
SWRT Testing and Model Development• SWRT Test
•Three different turbine configurations tested
• Most comprehensive small turbine test
• Upgrade FAST model to include furling
•Perform model comparisons between SWRT FAST and ADAMS models and FAST and SWRT
• Models often break down more for small turbine conditions
•In and out of stall more
•More yawed flow conditions
•Dynamically active turbine
4SWRT Project
SWRT Test Description
Yaw slip rings and encoder
Furl Sensor
Sonic anemometer junction box
Shaft sensor
Flap and edge blade strain gages
Tower leg load cell “washers”
Rotor slip ring, encoder, and amplifiers
5SWRT Project
SWRT shaft sensor - first accurate small turbine thrust
measurements Measures Shaft
0/90 bending, torque, thrust on fixed frame
4 by 4 cross-talk matrix
Critical path load is the shaft bending from gyroscopic loads
6SWRT Project
Pre-testing Turbine Characterization
Data for modeling included:
– Tail assembly and main frame:
• Weight, Cg, bi-filar, moment of inertia about yaw axis
– Magnet can Cg and moment of inertia
– Tail damper properties– Exact turbine
geometries– Blade modal test
7SWRT Project
Max and Mean Furl vs. Mean Wind Speed
-20
0
20
40
60
80
5 10 15 20
Mean Wind Speed, m/s
Fu
rl, d
eg
Max Furl Furl
8SWRT Project
Yaw Rate vs. Mean Wind Speed
-150
-100
-50
0
50
100
150
5 10 15 20
Mean Wind Speed, m/s
Ya
w R
ate
, de
g/s
Max yaw rate Mean yaw rate Min yaw rate
9SWRT Project
Rotor Speed vs. Mean Wind Speed
0
100
200
300
400
500
600
5 10 15 20Mean Windspeed, m/s
RP
M
RPM mean RPM max RPM min
10SWRT Project
Furl vs. Thrust
0
10
20
30
0 500 1000 1500 2000 2500
Thrust, N
Fu
rl,
de
g
Mean Furl versus Thrust
11SWRT Project
SWRT Furling Event – Time Series Plot
320320 340340 360360 380380 400400 4204200
10
20
30
40-1000
0
1000
2000
3000
4000
150
200
250
300
350
400
450
Win
d S
pee
d &
Fu
rl A
ng
le
Time, seconds
Sh
aft
Th
rust
Ro
tor
RP
M
320 340 360 380 400 420
-60
-30
0
30
60
90Y
aw E
rro
r
12SWRT Project
Furling and Center of Thrust
0
5
10
15
20
25
30
35
40
45
50
5 7 9 11 13 15 17 19 21
Time, seconds
Fu
rl, Y
aw E
rro
r (d
egre
es)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
Cen
ter
of
Th
rust
(m
eter
s)
furl yaw error center of thrust
13SWRT Project
SWRT Test Configurations
All configurations tested with inverter load – Total of 514 10-minute
records
A few resistor load files taken for each configuration– Some scatter in rpm-
torque curve from inverter controller hysteresis
SWRT Configuration
A B C
Airfoil SH3052 SH3052 SH3055
Lateral shim
4 degree
none none
Swept Area/Rotor Diameter
26.4 m2/ 5.8
m
26.4 m2/ 5.8
m
35.3m2 /
6.7 m
Blade pitch
11.5 11.5 9.5
14SWRT Project
Furl vs. Wind Speed for Different Configurations
0
5
10
15
20
25
30
35
40
45
50
9 11 13 15 17 19 21
Mean Windspeed, m/s
Fu
rl D
eg
ree
s
Mean Config A
Mean Config B
Mean Config C
Poly. (MeanConfig C)Poly. (MeanConfig A)Poly. (MeanConfig B)
Configuration C
Configuration B
Configuration A
15SWRT Project
Thrust vs. Wind Speed for Different Configurations
0
500
1000
1500
2000
2500
3000
3500
5 9 13 17 21Mean Windspeed, m/s
Th
rus
t, N
Mean Config AMean Config BMean Config C
16SWRT Project
Ratio of Tail/Met Wind Speed vs. Wind Speed
0%
20%
40%
60%
80%
100%
5 10 15 20Wind Speed, m/s
Ra
tio
Ta
il/M
et
WS
, %
Tail/Met WS Ratio A
Tail/Met WS Ratio C
17SWRT Project
Power/Thrust Ratio for Configurations A and C
0
1
2
3
4
5
6
5 10 15 20Wind Speed, m/s
Po
we
r/T
hru
st
Ra
tio
Power/Thrust Ratio Config C
Power/Thrust Ratio Config A
18SWRT Project
Furling and Inflow
Use sonic anemometer and meteorological data
Correlate inflow parameters and furling
Shows significance of vertical wind component and coherent turbulent kinetic energy
19SWRT Project
Furling and Richardson Number
SWRT Configuration "A" Mean Furling Angle & Mean Coherent Turbulent Kinetic Energy (Coh TKE)
vs Vertical Stability (Ri)
2-50m layer Richardson number stability parameter, Ri
-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15
Meanfurling angle (deg)
0.001
0.01
0.1
1
10
100
Hub mean Coh TKE
(m2/s2)
0
10
20
30
40
50
60
Mean Furling AngleMean Coh TKE
Max ART Response
20SWRT Project
- CoTKE and vertical gust variance for two files with same wind
speed and different furl
Cycles/min0.1 1 10 100
RM
S C
oh
TK
E (
m2/s
2)
0
2
4
6
8
10
12
Coherent TKE
Frequency (Hz)0.001 0.01 0.1 1 10
RM
S C
oh
TK
E (
m2/s
2)
0
2
4
6
8
10
12
FurlNo Furl
Wavelength in Rotor Diameters
1 10 100 1000
RM
S C
oh
TK
E (
m2/s
2)
0
2
4
6
8
10
12
Vertical Gust Velocity Variance
Frequency (Hz)
0.001 0.01 0.1 1 10
w' V
aria
nce
Sp
ectr
a (m
2/s
2)
0.0
0.1
0.2
0.3
0.4
0.5
Wavelength in Rotor Diameters
1 10 100 1000
w' V
aria
nce
Sp
ectr
a (m
2/s
2)
0.0
0.1
0.2
0.3
0.4
0.5
Cycles/min0.1 1 10 100
w' V
aria
nce
Sp
ectr
a (m
2/s
2)
0.0
0.1
0.2
0.3
0.4
0.5
21SWRT Project
SWRT Test & Simulation ModelsSWRT FAST Model
Extensive turbine properties provided by NREL
12 degrees-of-freedom (DOFs) used– Blade flexibility 2 flap and 1 edge mode DOF per blade– Drivetrain 1 variable generator speed DOF with
torque-speed look-up table– Nacelle yaw 1 yaw DOF– Tail-furl 1 tail-furl DOF with nonlinear
damper
Aerodynamics– Used dynamic stall and dynamic inflow options in AeroDyn– Original airfoil data based upon Selig wind tunnel tests
• Tapered tip section airfoil data based upon XFoil predictions by Tod Hanley
– Airfoil data “tuned” after comparing with measured Cp-TSR data (very limited range)
Dynamics verified via comparisons with ADAMS
22SWRT Project
Model & Test Comparisons Configuration A Statistics (Inverter Load)
0
100
200
300
400
500
600
700
6 8 10 12 14 16 18Mean Windspeed, m/s
Ro
tor
Sp
eed
, RP
M
Test mean Test max
FASTMean FASTMax
23SWRT Project
Model & Test Comparisons Configuration A Statistics (Cont’d.)
0
15
30
45
60
75
6 8 10 12 14 16 18Mean Windspeed, m/s
Fu
rl A
ng
le, d
eg
Test mean
Test max
FASTMean
FAstMax
24SWRT Project
Model & Test Comparisons Configuration A Statistics (Cont’d.)
0
1
2
3
4
5
6
6 8 10 12 14 16 18Mean Windspeed, m/s
Ro
tor
Th
rust
, kN
Test mean Test maxFASTSNWind Mean FAST SNWindMaxFASTTurbmean FASTTurbMax
25SWRT Project
Model & Test Comparisons Configuration A Statistics (Cont’d.)
0
5
10
15
20
25
6 10 14 18Mean Windspeed, m/s
Yaw
Err
or,
deg
Test mean
FAST Mean
26SWRT Project
Model & Test Comparisons - Configuration B with Resistor Load - Mean wind speed 17.2 m/s
0 100 200 300 400 500 600200
300
400
500
600
700
R
oto
r S
pe
ed
, R
PM
Time, s
Test FAST
27SWRT Project
Model & Test Comparisons - Configuration B with Resistor Load - Mean wind speed 17.2 m/s
0 100 200 300 400 500 600
0
10
20
30
40
50
F
url
An
gle
, d
eg
Time, s
Test FAST
28SWRT Project
Model & Test Comparisons - Configuration B with Resistor Load - Mean wind speed 17.2 m/s
0 100 200 300 400 500 6000
1
2
3
4
5
6
7
Ro
tor
Th
rus
t, k
N
Time, s
Test FAST
29SWRT Project
Model & Test Comparisons - Configuration B with Resistor Load - Mean wind speed 17.2 m/s
0 100 200 300 400 500 600
-50
-40
-30
-20
-10
0
10
20
Y
aw
An
gle
, d
eg
Time, s
Test FAST
30SWRT Project
SWRT Summary
Most comprehensive small turbine test data set
Better understanding of small wind turbine dynamic behavior, including thrust and furling
SWRT test data and modeling effort will help make furling design efforts for small wind turbines easier, but furling remains a challenge!
Better test procedures for small turbine testing
Inflow analysis shows effects of turbulence
Fundamental shortcomings in aerodynamic modeling are the main reason for test data and model disagreements– 3-D stall effects (i.e., rotational augmentation)– Uncertainties in skewed wake correction for yawed
flow