Opportunities for wind resource assessment using numerical and observational wind atlases: modelling, verification and a

1. Opportunities for wind resource assessment using numerical and observational wind atlases: modelling, verification and application J.C. Hansen, N.G. Mortensen, J. Badger, N.E. Clausen and P. Hummelshøj Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

2. Outline • Introduction • Observational wind atlas • Numerical wind atlas • Verification • Application • Conclusions Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

3. Introduction ◄ the observationalwind atlas method and the micro-scale flow model, WAsP, were conceived in the 80’s for the European Wind Atlas. ► the numerical wind atlas andmesoscale model techniques for larger domains, mesoscale effects and long-term wind climates came in the 90’s. State-of-the-art for wind resource assessment and planning is a combination of micro- and mesoscale modelling with verification against measurements. Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

4. Observational wind atlas Inputs • measured time-series of wind speed and direction – observed wind climate • terrain topography – elevation, roughness and obstacles – from digitised maps, SRTM data, Google Earth Outputs • generalised regional wind climate for the specific location Applications • energy production estimates for wind farms in the region near the meteorological station Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

5. Observational wind atlas – limited coverage In flat, uniform terrain the density of meteorological station should be high – spacing less than ~50 km for planning purposes. In complex terrain and for project development, on-site measurements are necessary. Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

6. WAsP – wind resources, production estimation and siting • The industry-standard Wind Atlas Analysis and Application Program • More than 2000 users in over 100 countries use WAsP for: • Wind data analysis • Map digitisation & editing • Wind atlas generation • Wind climate estimation • Power production of WTG’s • Micro-siting of wind turbines • Wind farm production • Wind farm efficiency • Wind resource mapping Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

7. Numerical wind atlas – mesoscale Inputs • NCEP/NCAR reanalysis data-set • terrain topography – elevation and roughness – from satellite and SRTM data Outputs • generalised regional wind climatefor large domains Applications • planning • assessment of mesoscale effects at wind farm projects Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

8. Numerical wind atlas Wind Atlas for Egypt Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

9. Verification • verification of mesoscale modelling by comparing to measurements requires application of the wind atlas methodology to account for • the spatial representation of the terrain • roughness conditions varying on a scale smaller than the grid scale • sharp or steep surface elevation features that will tend to be smoothed and rounded by the grid scale • high-quality and well-distributed wind measurement stations are needed Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

10. Verification • Comparison of wind climates in Egypt – numerical wind atlas against observational wind atlas at measurement sites • heights over flat terrain: 10 m, 25 m, 50 m, 100 m and 200 m • uniform surface roughness of z0 = 0.03 m Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

11. Verification – observed wind climate / wind measurements • The wind data must be • accurate • representative • reliable Proven sensors and new technology Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

12. Wind in natural terrain – uncertainties Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

13. Application • the combined numerical and observational wind atlas methods verified against measurements offer opportunities for • planning and feasibility studies • project development • wind farm siting, layout design and micro-siting • tests and sensitivity analyses of uncertainties of microscale and mesoscale modelling are needed, e.g. • model parameters • adaptation of models to local conditions • site calibration and verification against measurements • wind climate variability, inter-annual variations, long-term averages • climate change • man-made large-scale effects, especially of new large wind farms Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

14. Application mesoscale modelling may be used to identify locations with large gradients and thus locations where an extended measurement programme will be advisable in order to avoid gross errors in wind resource assessment. Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

15. KAMM wind resource map only Grid cell size 5120 m Wind farm of five 2 MW turbines Estimated AEP = 39 GWh KAMM/WAsP wind resource map Grid cell size 20 m Wind farm of five 2 MW turbines Estimated AEP = 55 GWh Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

16. Modelling, verification and uncertainty summary Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

17. State-of-the-art wind atlas method Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark

18. Conclusions The wind atlas method • resolves different features of the terrain by employing both mesoscale and microscale models • provides new opportunities for planning on a large scale with limited availability of wind data • is useful in the different phases of planning and project preparation, providing readily applicable, standardised information for all parties of the projects • ensures a consistent basis for verification at wind farm sites • improves uncertainty assessment • reduces risk of gross errors Techniques of the wind atlas method should be improved through continued research efforts, making use of the ever-increasing computing power of new computers and of new measurement technologies, mapping techniques and satellite imagery. Wind Power Shanghai 2007 Risø National Laboratory • Technical University of Denmark