Offshore Wind Power | Ocean Turbines

Information in this section allows using real wind turbines in calculations. We list here only machines that are designed for offshore use, that are large enough to satisfy offshore economics (at least 3 MW), and that have units installed offshsore and producing power. With hub height and a power curve (included for both 3.6 and 5M below), meteorological data, and a "modern" velocity-at-height extrapolation method, you can calculate how much power a turbine will produce at a given site. With that, the machine's max water depth, site bathymetry, inter-turbine spacing, a little shelf geology, and exclusion zone assumptions, you can calculate resource size in your favorite state's EEZ. Simple! (Just be sure your calculator can handle a lot of digits!) Our numbers below are our best estimates, see brochures for official specifications from the turbine vendors. No endorsement of these products is implied. Investment decisions should not be made without verification of these numbers and assertions. We will attempt to list all products meeting our above criteria and having published specs; please inform us of any not listed here.

Vestas V90. Capacity 3 MW, rotor diameter 90 m, hub height 80 to 105 m. Vestas has by far the most experience with multi-megawatt machines offshore. Many V90s are currently operating offshore: 30 at Kentish Flats since August 2005, 30 at Barrow since May 2006 and 36 at Egmond aan Zee off Egmond, Netherlands since Nov 2006. The V90-3 brochure includes power curve and technical specs.

REpower 5M. Capacity 5 MW, rotor diameter 126 m, hub height 90 m. Two units offshore producing electricity at Beatice site since August 2007. See product brochure for REpower 5M. An older and a much longer product brochure is interesting because it profiles the 32 major subcontractors, giving a flavor of all that goes into a large turbine -- older 5M brochure.

Siemans SWT-3.6-107. Capacity 3.6 MW, diameter 107 m, hub height 83.5 m (at Burbo project). At Burbo Bank, Liverpool Bay, operating offshore since October 2007. Current target for offshore would be their 3.6MW Siemens SWT-3.6-107 (no power curve). Siemens entered the wind business by buying Bonus and got considerable offshore experience in the process.

General Electric 3.6sl (discontinued). Capacity 3.6 MW, rotor diameter 111 m. Hub height 75 m (from Cape Wind design specs). Seven 3.6s units producing power offshore at Arklow Bank since June 2004. See product brochure for GE 3.6sl. Based on experience at Arklow, GE had a set of engineering modifications to make for serial production of an offshore machine, but the company has to date decided not to compete in this market.

For resource estimates, water depth is also very important; this is really dependent on the tower design not the wind turbine and nacelle, although the turbine manufacturer would have to approve the tower. Monopile support towers are now limited to 30 m max water depth. The new OWEC Jacket Quattropod, installed at the Beatrice Demonstrator site off Scotland in 2007, is in 45 m of water. This design is said to be viable down to about 90 m water depth.