Modelling the impact of wakes on power output at Nysted and Horns Rev

R.J. Barthelmie, Indiana University USA/Risoe DTU DKK. Hansen, DTU Denmark

S.T. Frandsen, O. Rathmann, RISOE DTU Denmark G. Schepers ECN, Netherlands

K. Rados, NTUA, GreeceW. Schlez, A. Neubert, GH, Germany L.E. Jensen, DONG Energy, DenmarkS. Neckelmann, Vattenfall, Denmark

Funding: NSF CBET-0828655, EU UPWIND # SES6 019945 EU POWWOW #SES6 019898 Data: DONG Energy A/S & Vattenfall AB (Horns Rev), Vattenfall and E. On Sweden

(Nysted)

Modelling wakes in the UpWind projectProblems1. Preliminary analysis of wake

power losses in large offshore wind farms larger than expected. Amended but high uncertainty

2. First v. large wind farms on land

3. Resources and wakes difficult to model in complex terrain

4. Multiple wind farms developed in same area

Solutions1. New parameters and/or next

generation of wake models able to account for ‘deep array’ effect

2. (Assess the magnitude of the issue onshore)

3. Develop, apply and evaluate CFD

4. Assess, develop and evaluate models for whole wind farm modelling

DataIn agreement with data owners some wind farm data have been made availableAccess is open and free (registration necessary)Offshore wake data from

• Vindeby• Middelgrunden• Horns Rev• Nysted (in proc)

Data processed into case studies for Horns Rev, Nysted (performance remains confidential)

Access /registration details:http://mypage.iu.edu/~rbarthel/wakeslab.html

Wake models used in this project

Name Company Type Commercial/ Research

WAsP Risø DTU Engineering CWindfarmer GH Ainslie CRisø Flow Risø DTU Under

developmentR

Wakefarm ECN Parabolised CFD

C/R

CENER Fluent CENER CFD RNS FLow CRES CFD R

NTUA NTUA CFD R

Offshore wind farmsWind farm Nysted Horns Rev

Owner DONG Energy (80%) E.On Sweden (20%)

DONG Energy (40%)Vattenfall (60%)

Turbine number 72 80

Turbine Siemens 2.3 MW Vestas 2 MW

Turbine type Active stall, 2-speed Pitch, variable speed

Rotor diam (D) 82.4 m 80 m

Hub-height 69 m 70 m

Array 8 (E-W) x 9 (N-S) 10 (E-W) x 8 (N-S)

Dist. between turbines

10.3 D (E-W) & 5.8 D (N-S)

7 D (E-W & N-S)

Rated capacity 165.6 MW 160 MW

Annual prod. 595 GWh 600 GWh

Year comm. 2003 2002

Water depth 6-10 m 6-14 m

Distance land 10 km (closest) 14-20 km

http://earthobservatory.nasa.gov/IOTD/view.php?id=3389

7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0

Longitude (° E)

54.5

55.0

55.5

56.0

56.5

57.0

57.5

Latitu

de (°

N)

Horns Rev

Nysted

Horns Rev and Nysted layouts

Horns Rev 7D x 7D Nysted 10.5D x 5.8D

Data comparisonData from 2004-2006 Nysted, 2005 Horns RevSelection on:

• wind speed ±0.5 ms-1

• direction ±2.5º • all turbines working in row• all turbines working in

neighbouring rows• two subsequent

observations for stationarity

Gives relatively few observations in each categoryData differences mainly due to spacing?

Model comparison at Horns Rev and Nysted

1 2 3 4 5 6 7 80.2

0.4

0.6

0.8

1

Nor

mal

ised

pow

er

1 2 3 4 5 6 7 80.2

0.4

0.6

0.8

1

Nor

mal

ised

pow

er

263±2.5o

2732.5o

1 2 3 4 5 6 7 80.2

0.4

0.6

0.8

1

Nor

mal

ised

pow

er2832.5o

1 2 3 4 5 6 7 80.2

0 .4

0 .6

0 .8

1

ObservationsW A sPW indfarm erECN

268±2.5o

1 2 3 4 5 6 7 80.2

0.4

0.6

0.8

1

278±2.5o

1 2 3 4 5 6 7 80.2

0 .4

0 .6

0 .8

1

288±2.5o

1 2 3 4 5 6 7 8Turbine

0.2

0.4

0.6

0.8

1

Nor

mal

ised

pow

er

293±2.5o

1 2 3 4 5 6 7 8 9 100.2

0.4

0.6

0.8

1

1.2

Nor

mal

ised

pow

er

1 2 3 4 5 6 7 8 9 100.2

0.4

0.6

0.8

1

Nor

mal

ised

pow

er

255±2.5o

2652 5o

1 2 3 4 5 6 7 8 9 100.2

0.4

0.6

0.8

1

Nor

mal

ised

pow

er

2752 5o

1 2 3 4 5 6 7 8 9 100.2

0.4

0.6

0.8

1

O bservationsW AsPW indfarm erEC NNTUA

260±2.5o

1 2 3 4 5 6 7 8 9 100.2

0.4

0.6

0.8

1

270±2.5o

1 2 3 4 5 6 7 8 9 100.2

0.4

0.6

0.8

1

280±2.5o

1 2 3 4 5 6 7 8 9 10Turb ine

0.2

0.4

0.6

0.8

1

Nor

mal

ised

pow

er

285±2.5o

Model comparison at Horns Rev and NystedExact row, narrow directions

• Seems to be a special case • Agreement on wake

behaviour at Horns Rev and Nysted

• Model agreement within ±10%

Cross row angles• Asymmetry in obs. and

models• Larger uncertainty

ER ER+10º

Model comparison at Horns Rev and NystedConsistency improved in model results High degree of uncertainty• Differences between models• Data issues• Lower wind speeds

Ongoing issues• Asymmetry around central

row• Developing quantitative

methods of evaluation e.g. efficiency

• Stability

Stability at Nysted

0 2 4 6 8Turb ine num ber

0.2

0.4

0.6

0.8

1

1.2

Nor

mal

ised

pow

er o

utpu

t (kW

)

A llS tableU nstableN eutra l

8<U<10 m /s Turbines in row 5 operating0.5 s.d.

.

.Results from Barthelmie et al. European Offshore Wind 2007

-9 -6 -3 0 3 6 9D ista n ce fro m w a ke ce n tre in de g

0.5

0.6

0.7

0.8

0.9

1

Nor

mal

ised

pow

er a

t 2nd

turb

ine

N eutra lS tableU nstab le

Summary and future work• Objective

Reducing uncertainty in predicting power losses from wakes• UpWind project

Provides platform for undertaking model evaluation & data sharing

• Progress madeData analysis and modellingWakes can be modelled with appropriate parameters

• FuturePhysical understanding of wake processes within and downwind wind farms

Other UpWind wake presentations and posters

WIND TURBINE WAKE VIRTUAL LABORATORY: PROPOSAL FOR A NEW COLLABORATION

PO.155 Rebecca Barthelmie, Indiana University, United States & Risø DTU, Denmark

APPLYING FLOW MODELS OF DIFFERENT COMPLEXITY FOR ESTIMATION OF WIND TURBINE WAKES

PO.156 Søren Ott, Risø DTU, Denmark  

A FAST PARAMETERIZED WAKE-MODEL FOR LARGE WIND FARMS

PO.161 Ole Steen Rathmann, Risø DTU, Denmark  

CFD MODELING ISSUES OF WIND TURBINE WAKES UNDER STABLE ATMOSPHERIC CONDITIONS

PO.163 Evangelos Politis, Centre for Renewable Energy Sources (CRES), Greece  

NEW DEVELOPMENTS IN LARGE WIND FARM MODELLING

PO.167 Wolfgang Schlez, Garrad Hassan Deutschland GmbH, Germany  

CFD MODELLING OF THE INTERACTION BETWEEN THE SURFACE BOUNDARY LAYER AND ROTOR WAKE

Daniel Cabezón, CENER, Spain