SODAR: Uses and Acceptance
Gary Winslow
Senior Project Engineer
EAPC Wind Energy Services
14 September, 2009
What is SODAR?
• A form of remote sensing (LIDAR also)• SOnic Detection And Ranging• Emits sound (pings) and measures Doppler
shift and intensity of reflected signal• Measures vertical and horizontal wind speed,
direction, and turbulence• Remote sensing devices are used increasingly
in monitoring campaigns
Triton SODAR
Advantages of Remote Sensing
• Measure wind data above standard met tower heights (through hub and tip height)
• Measures the vertical component of the wind• Avoids issues of tower shading• Easy installation and portability• Powered with two solar panels (7 W continuous
power draw)• Low visual impact• May not require permits (remote or secluded
sites)
Limitations of SODAR
• Measurements affected by precipitation
• Analysis of data from sites with complex terrain requires additional effort
• May underestimate wind resource, requiring calibration with anemometer data
• Remote sensing is not yet accepted by industry as stand alone solution for monitoring for large commercial projects
EAPC and SODAR
• Currently offering SODAR services• Installed SODAR profiler on a site near the
Adirondacks in July • Now have two data monitoring devices at site:
60 m met tower and SODAR• Have 18 months of met tower data• Working to expand remote sensing services,
possibly including LIDAR
Data Analysis: Goals
• Determine correlations between wind speeds and directions
• Compare predicted wind shear from met tower to measured SODAR values
• Compare turbulence measurements• Bear in mind limitations of current site
• Low wind speed• Complex terrain: forest and topography• Only a little over a month of data
Early Results: Wind Speed
Note: Raw SODAR data is from 60.0m, not 57.6m
40.0m 50.0m 57.6m0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Mean Validated SodarMean Raw SodarMean Validated MetmastMean Raw Metmast
Height Above Ground (m)
Mean W
ind S
peed (
m/s
)
Early Results: Wind Direction
57.6 m, 60.0 m 50.0 m 40.0 m
SODAR
Top: SODAR, Bottom: Met tower
Early Results: Wind Speed Correlation
Sector with most wind data shows good correlation
Early Results: Shear
Measured Data Points
0
20
40
60
80
100
120
140
160
180
200
0 1 2 3 4 5 6 7Wind Speed (m/s)
Hei
gh
t Ab
ove
Gro
un
d (m
)
Measured Met mast
Measured SODAR
3 3.5 4 4.5 5 5.5 6 6.5
0
20
40
60
80
100
120
140
160
180
200Measured Data Points
Measured Met mastMeasured SODAR
Wind Speed (m/s)
He
igh
t A
bo
ve
Gro
un
d (
m)
Early Results: Shear
Shear Curves
0
20
40
60
80
100
120
140
160
180
200
0 1 2 3 4 5 6 7
Wind Speed (m/s)
He
igh
t A
bo
ve
Gro
un
d (
m)
Met Mast Wind speed (Log law)
Met Mast Wind speed (Power law)
SODAR Wind speed (Log law)
SODAR Wind speed (Power law)
Measured Met mast
Measured SODAR
0 1 2 3 4 5 6 7 8
0
20
40
60
80
100
120
140
160
180
200
Shear Curves
Met Mast Wind speed (Log law)Met Mast Wind speed (Power law)SODAR Wind speed (Log law)SODAR Wind speed (Power law)Measured Met mastMeasured SODAR
Wind Speed (m/s)
He
igh
t A
bo
ve
Gro
un
d (
m)
Expanded Clearing: Turbulence Turbulence by Sector
0
0.05
0.1
0.15
0.2
0.25
Mean N NNE ENE E ESE SSE S SSW WSW W WNW NNW
Direction Sector
Mean
Tu
rbu
len
ce I
nte
nsit
y
Pre-ClearingPost-Clearing
• Site has shown low wind resource• Does expanded clearing around site improve
quality? • Compare data: 1 month before, 1 month after• Decreased turbulence observed in some sectors
Conclusions and Next StepsCurrent Site:• Correlations and shear data encouraging• Plan to use correlation to predict 80m wind
speeds more accurately• Additional data should improve accuracy of
wind resource assessment
General:• All indications are that remote sensing will
see increased use and value.• Improved uncertainty figures (P75, P90) and
financial terms in future?