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Measurement and model requirements for offshore wind energy. Larry Atkinson Jose Blanco Virginia Coastal Energy Research Consortium Old Dominion University. Offshore wind farms have a good chance of being built. They will be large and there will be many of them.
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Measurement and model requirements for offshore wind energy Larry Atkinson Jose Blanco Virginia Coastal Energy Research Consortium Old Dominion University
Offshore wind farms have a good chance of being built • They will be large and there will be many of them. • The Minerals Management Service has set interim rules for planning, installation, operation, safety and removal. Photo from NREL
Pathways for offshore technology (Musial, 2007)
Outline • Status of wind farm development off the NE United States • Information requirements for • Engineering • Power management • Safety • Environmental related needs • What assets do we now have for observing • Conclusions
Status for Northeast US • There are no wind turbines in either state or federal waters in the US. • Pre-lease activities starting – state by state ‘task forces’ being formed • Met towers will be proposed soon for locations off VA, DE, NJ, and RI. • Note met towers must be to hub height and make direct measurements. • Proprietary data issues being addressed • MMS funding literature reviews and synthesis. Cape Winds Met Tower
For example - off Virginia the state is identifying possible locations From VCERC presentations
Required Data For Offshore Sitting & Design • Wind - Waves – Currents • Avg. Speeds – annual, monthly, diurnal (at hub height) • Speed Frequency Distribution • Wind Shear • Turbulence Intensity • Wind Direction Rose • Extreme Gusts & return periods • Coincident Sea-State Conditions • Water and air temperatures • Aerosol production - corrosion • Waves spectra and return period • Extreme wave and wind events - hurricanes, northeasters, thunderstorms From NREL report
More detail needed on wind classes – example off Virginia How real are the details in these wind maps? From NREL report and website
Boundary Layer Data Neededrecommendations from NREL Report • Wind characteristics at coastal and marine locations need to be evaluated on a case-by-case basis. • Variations in the structure of marine boundary layers are significant and require further detailed study. • A key component of future studies is additional measurement data from 70 to 100 m above the surface. • Tall-tower measurements and remote sensing instrumentation will be crucial to increase the knowledge of marine boundary layer structure and its effect on the viability of wind energy projects in coastal and marine areas. NREL 2007 “Coastal and Marine Tall-Tower Data Analysis: Preprint”, Schwartz, Elliott and Scott
Information requirementsPower management • Local gust and turbulence detection and prediction • Larger scale wind field prediction for power management. • Predicting shut down conditions
From AWEA ReportOffshore Wind Working Group 3 April 2009 • Predict dynamic forces and motions acting on turbines • Predict loads and dynamic responses of the coupled wind turbine and support structure when subjected to combined stochastic wave and wind loading. • Impact of floating debris and ice and from marine growth buildup on the substructure. From http://www.iopara.ca
Information RequirementsSafety and Operations • Wind, wave and current observations and predictions • Icing • Visibility From Siemans/StatoilHydro
Information requirementsEnvironmental • Bird migration (NEXRAD used for bird mapping) • Factors related to bird/bat turbine interaction • Fish aggregation • Effect on wave and current patterns “Avian collision risk at an offshore wind farm” Desholm and Kahiert, Biol. Lett., doi: 10.1098/rsbl.2005.0336.
Current observing assets in the water Most wind farms will be around 12 miles offshore. Observing stations are typically coastal or mid to outer shelf. Thus wind farms are going into areas not well sampled. Sea breeze is an issue.
Buoys and a few towers • Towers provide data approaching hub height but there are few of them • The are more buoys (less than 10 in the area).
Remote Sensing of ocean winds • Remote sensing winds ‘speculative’ for offshore wind farms. (Pryor et al 2004) • Must be improved as spatial coverage needed and in situ cannot cover.
Integrating wind farms to even out power production • Visualize wind farms from Cape Hatteras to Cape Cod • How to manage the power output of the system as a whole with the multiple power companies in the region. • Predictions needed to manage power market.
Final Thoughts • We will need better nowcasts and forecasts of offshore wind and waves at finer time and space scales. • Our understanding of the marine boundary layer and sea breeze in coastal waters must improve. • AMS and AWEA might (if they are not already) collaborate on offshore renewable energy issues. • There will be an opportunity for industry to develop new business.