Offshore Wind Power   |   Ocean Turbines

Photo of Vestas turbine cutaway model
Vestas cutaway model.   Photo by Willett Kempton, © 2005 University of Delaware (see below)

Here we list only ocean turbines that are designed for offshore use, and that are large enough to satisfy offshore economics (at least 3 MW). The first set listed below are limited to units already installed offshsore and producing power.

Information in this section allows using real wind turbines in resource calculations. With hub height and a power curve, 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.

Production machines, operating in the ocean

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 5M's 32 major subcontractors, giving a flavor of all that goes into a large turbine -- older 5M brochure.

Siemens 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, several more since 2007. For offshore use, see specifications on their 3.6 MW Siemens SWT-3.6-107 (no power curve). Siemens entered the wind business by buying Bonus, which had considerable offshore experience.

Multibrid M5000. Capacity 5 MW, diameter 116 m. Six units are in 30 m of water at Alpha Ventus, operating since July 2009. Technical spec sheet, including power curve, and less technical product brochure. This company is specializing in offshore turbines only, no land-based business planned. Multibrid is now a subsidiary of Ariva.

Additional offshore machines of interest

Gamesa 4.5 This is a 4.5 MW machine, with two prototypes operating on land in CENER, Spain. In-water test being planned jointly with Gamesa and University of Delaware.

Clipper Britianna, or MBE, 10 MW This is designed for offshore use only. Fully designed and prototype under construction, none in operation yet.

HyWind The only full-scale floating platform built and operating is StatoilHydro's HyWind. A full-scale prototype using a Siemens 2 MW turbine has been operating off Norway since summer 2009.

General Electric 3.6sl (discontinued; only of comparative interest). 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 prepare for serial production of an offshore machine, but the company has discontinued this product and purchased a company with a direct drive turbine for their future offshore product line.

Foundation and tower

For resource estimates, water depth and hub height are also very important; these are really dependent on the foundation and tower design not the wind turbine and nacelle, although the turbine manufacturer would have to approve the supporting structures. Monopile supports are the only design in widespread, serial production, now limited to 40 m max water depth. The 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 100 m water depth, and, at higher cost, possibly as deep as 200 m.