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Wind resources and wind farm wake effects offshore observed from satellite

Charlotte Bay Hasager

Poul Astrup

Merete Bruun Christiansen

Morten Nielsen

Rebecca Barthelmie

Risø National Laboratory, Wind Energy Department

EWEC 2006, Athens 27 February to 2 March 2006

Motivation

Satellite data are complementary to:

offshore in-situ data……….that are costly

offshore model results…….that are not fully verified

EWEC 2006, Athens 27 February to 2 March 2006

1800 km

400 km

100 km

EWEC 2006, Athens 27 February to 2 March 2006

),( ionwinddirectwindspeedfSectionRadarCrossNormalized

PhysicsOcean surface is roughened

by wind interaction such that

capillary and short gravity

waves are generated.

More wind causes

more steep waves that

causes higher backscatter.

EWEC 2006, Athens 27 February to 2 March 2006Courtesy: NOAA

Horns Rev, Elsam A/S

EWEC 2006, Athens 27 February to 2 March 2006

EWEC 2006, Athens 27 February to 2 March 2006

QuikScat Mean wind speed 5 years

Number of observations: 3650 (twice per day for 5 years)

Grid cell:

ca. 25 km

EWEC 2006, Athens 27 February to 2 March 2006

QuikScat North

EWEC 2006, Athens 27 February to 2 March 2006

QuikScat East

EWEC 2006, Athens 27 February to 2 March 2006

QuikScat South

EWEC 2006, Athens 27 February to 2 March 2006

QuikScat West

Weibull A and k per sector in WASP tab-file format available

EWEC 2006, Athens 27 February to 2 March 2006

Wind field from Envisat ASAR WSM (Courtesy: JHU/APL)

Horns Rev, Elsam A/S

EWEC 2006, Athens 27 February to 2 March 2006

EWEC 2006, Athens 27 February to 2 March 2006

EWEC 2006, Athens 27 February to 2 March 2006

Envisat processed at JHU/APL

EWEC 2006, Athens 27 February to 2 March 2006

7

8

9

10

0 50 100 150 200 250

North Distance (km) South

Mea

n w

ind

spee

d (m

/s)

Near coast11 km west

EWEC 2006, Athens 27 February to 2 March 2006From Nielsen et al. 2004, Risø-R-1479(EN)

Horns Rev (Denmark)

5 km

ERS

Mean wind speed for 30 days

Grid cell: 400 m

EWEC 2006, Athens 27 February to 2 March 2006

91 SAR wind maps

Directions from image, LG supervised

U = 7.8 m/s

E = 496 W/m2

Directions from met. mast

U = 7.3 m/s

E = 421 W/m2

Directions from image, LG automatic

U = 7.7 m/s

E = 510 W/m2

In situ measurements (Sommer, 2003):

U = 7.6 m/s

E = 422 W/m2

EWEC 2006, Athens 27 February to 2 March 2006

EWEC 2006, Athens 27 February to 2 March 2006

Wind farm sites

ERS (no wind)

Horns Rev

Offshore Wind Farm

BlaavandshukMet. mast

N

EWEC 2006, Athens 27 February to 2 March 2006

Wind farm

ERS

Horns Rev

Wind farm wake effects

Reduced mean wind speed

Enhanced turbulence

EWEC 2006, Athens 27 February to 2 March 2006

x

y

Y

X

EWEC 2006, Athens 27 February to 2 March 2006

Airborne SAR (E-SAR)

12 October 2003

Wind

Met. mast

5 flight tracks in C-band VV

EWEC 2006, Athens 27 February to 2 March 2006

Winds from E-SAR in CVV

Wind farm Wind farm

Wind Wind

Wind speed Velocity deficit

EWEC 2006, Athens 27 February to 2 March 2006

Christiansen & Hasager (2006), Using airborne SAR for wake mapping offshore. Wind Energy (in press).

EWEC 2006, Athens 27 February to 2 March 2006

Acknowledgements:Danish Research Agency SAT-WIND and SAR-WAKE projects; ESA EO-windfarm and EO-1356 projects;Elsam A/S Meteorological data.

Wind resources can be estimated from satellite wind maps as a supplement to in-situ data.

Wake velocity deficit can be quantified from satellite wind maps.

Conclusions