SODAR: Uses and Acceptance

Laura Tabor

Wind Engineering Intern

EAPC Wind Energy Services

August 7, 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?