Offshore wind Offshore Wind Requirements Large projects improve economics Avg. winds stronger than 16 mph (7 m s-1) (Class 4+) “Shallow” water depths, for now Avoid areas with excessive waves Avoid environmentally sensitive areas, shipping lanes, etc. Near transmission & port facilities. Why Wind Offshore is better? Lower Surface Roughness, Reduced Turbulence Intensity More Persistent (hence dependable and predictable) Higher Capacity Factor. Offshore Wind Benefits Better wind resources Reduced turbulence –steadier wind Higher wind = better energy production Higher capacity factors –load matching Minimize visual impacts with greater distances. Proximity to load centers Lower transmission constraints Serve high cost regions Exploits indigenous energy Avoids size limits Shipping–Land-based roadway limits Erection–crane limits Larger machines are more economical. Resource Information Gaps Measurements near hub height, Unreliability of extrapolated wind speeds from buoys or satellites. Structure of wind profiles due to boundary layer stability (shear!). Incidence of low-level jets Dissipation rate of turbine wakes Magnitudes & probabilities of extreme gusts and coincident waves