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

1. Modelling the impact of wakes on power output at Nysted and Horns Rev • R.J. Barthelmie, Indiana University USA/Risoe DTU DK • K. Hansen, DTU Denmark • S.T. Frandsen, O. Rathmann, RISOE DTU Denmark • G. Schepers ECN, Netherlands • K. Rados, NTUA, Greece • W. Schlez, A. Neubert, GH, Germany • L.E. Jensen, DONG Energy, Denmark • S. 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)

2. Modelling wakes in the UpWind project Problems • Preliminary analysis of wake power losses in large offshore wind farms larger than expected. Amended but high uncertainty • First v. large wind farms on land • Resources and wakes difficult to model in complex terrain • Multiple wind farms developed in same area Solutions • New parameters and/or next generation of wake models able to account for ‘deep array’ effect • (Assess the magnitude of the issue onshore) • Develop, apply and evaluate CFD • Assess, develop and evaluate models for whole wind farm modelling

3. Data • In agreement with data owners some wind farm data have been made available • Access 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

4. Wake models used in this project

5. 57.5 57.0 ) N 56.5 ° ( e d u t 56.0 i t a L 55.5 Horns Rev 55.0 Nysted 54.5 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) Offshore wind farms http://earthobservatory.nasa.gov/IOTD/view.php?id=3389

6. Horns Rev and Nysted layouts Nysted 10.5D x 5.8D Horns Rev 7D x 7D

7. Data comparison • Data from 2004-2006 Nysted, 2005 Horns Rev • Selection 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 category • Data differences mainly due to spacing?

8. Model comparison at Horns Rev and Nysted

9. Model comparison at Horns Rev and Nysted • Exact 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

10. Model comparison at Horns Rev and Nysted • Consistency 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

11. Stability at Nysted Results from Barthelmie et al. European Offshore Wind 2007

12. Summary and future work • Objective • Reducing uncertainty in predicting power losses from wakes • UpWind project • Provides platform for undertaking model evaluation & data sharing • Progress made • Data analysis and modelling • Wakes can be modelled with appropriate parameters • Future • Physical understanding of wake processes within and downwind wind farms

13. Other UpWind wake presentations and posters