UD Wind Power Program | Ocean Turbines, Foundations & Projects
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 capacity). The first set listed below are limited to units already installed offshore 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 and Near-production machinesVestas V164 8MW – Capacity of 8MW, rotor diameter of 164 m. Recently installed and operational in Østerild test station, this turbine is the highest capacity turbine producing power in the world and stands 220 meters tall. Four of these turbines have recently been ordered for a project off of western Denmark. See the Vestas offshore wind brochure for more details.
Senvion (formerly Repower) 6.XM Series – Capacity of 6.2MW, rotor diameter of 126m or 152 m. The Senvion 6XM series is currently the largest turbine installed in the open sea. Currently in use at Thornton Bank wind farm in Belgium. More details may be found at their website.
Siemens SWT-6.0 154 (Turbina Sapiens) Capacity of 6MW, rotor diameter of 154 m. This turbine is a direct drive machine, resulting in 50% less moving parts. Two machines were installed in January 2014 in Gunfleet Sands III.
Alstom Halaide – Capacity of 6MW, rotor diameter of 150 m. The Halaide is being used in Phase 2 of the Belwind Wind Farm, and has over 240 turbines ordered for farms planned off the coast of France. The first turbine was installed in November 2013. GE recently agreed to acquire Alstom Power. More details may be found at their website.
REpower 5M. Capacity 5 MW, rotor diameter 126 m, hub height 90 m. 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.
Areva M5000 (formerly Multibrid) –Capacity of 5MW, rotor diameter of 116 to 135 m. These turbines were used in Alpha Ventus, Germany’s first offshore wind. More details may be found at their website.
Bard WEC 5MW Capacity of 5.2 MW, rotor diameter of 122 m. This turbine is being used at the BARD Offshore 1 in German waters.
Darwind XD115 5MW – Capacity of 5MW, rotor diameter of 115m. Darwind has prototype turbines up and running in China and the Netherlands. The Fishermen’s Energy demonstration project, which is to be located off the coast of New Jersey, also plans to use 5 XD115 turbines. More details may be found at their website.
Siemens SWT 3.6-120 - Capacity 3.6 MW, rotor diameter 120 m, hub height 90 m. The SWT 3.6-120 is one of the most prevalent offshore wind turbines in the world, with over 360 turbines in the water, including the world’s largest offshore wind farm, the London Array. More details may be found at their website.
Siemens SWT-3.6-107. Capacity 3.6 MW, diameter 107 m, hub height 83.5 m (at Burbo project). At Burbo Bank, Greater Gabbard, 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.
Vestas V90-3.0MW. Capacity 3 MW, rotor diameter 90 m, hub height 80 to 105 m. Vestas was one of the first wind turbine companies 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.
Siemens SWT-3.0-101. Capacity 3 MW, hub height 80 m, rotor diameter in brochure is 101 m, but for 9m/s average wind speeds offshore could be 113 m. The first multi-MW direct drive (no gearbox) permanent magnet, offshore machine commercially available. Specifications at LINK but no power curve.
Additional offshore machines of interestLarge wind turbines
Statkraft 8MW Capacity of 8MW, rotor diameter of 160 m. Statkraft was recently given permission to construct and test a prototype of its 8MW turbine in Norway.
Samsung S7.0 171 Capacity of 7MW, rotor diameter of 171 m. This high capacity turbine has the longest turbine blade of any wind turbine in development. The turbine will be installed at a Scottish energy park as a prototype for testing. The turbine will be available by 2015.
Sinovel SL6000 – Capacity of 6MW, rotor diameter of 128 m. The SL6000 is China’s largest offshore wind turbine, and Sinovel is the second largest turbine maker in the world. In addition, this turbine has a low voltage ride through capacity, a requirement for wind farms based in China. Seventeen SL6000s are expected to be connected to the grid in 2015.
Gamesa 5.0 MW Turbines - Capacity of 5MW, rotor diameter of 128 to 132 meters. These turbines have been ordered for a project in Finland, up to a capacity of 135 MW. In addition, there is a prototype operating on the coast of Spain. More details may be found at their website.
Siemens SWT 4.0-130. Siemens installed a prototype in Osterild, Denmark in 2013. Siemens will supply 72 4MW turbines for the Sandbank offshore wind project in Germany.
HyWind The only full-scale spar buoy floating platform built, and first floating wind turbine operating is StatoilHydro's HyWind. A full-scale prototype using a Siemens 2 MW turbine has been operating off Norway since summer 2009. In addition, this model will be used in an upcoming 6 turbine, 30 MW demonstration project off the coast of Scotland.
Windfloat The second floating turbine, and the first semi-submersible floating platform was produced by Principle Power and has been operating off the coast of Portugal since 2011. The WindFloat is of interest because it can be constructed in port and then towed out to location of installation. In addition, Principle Power has a plan to install six more floating turbines off the coast of Oregon as part of a Department of Energy Demonstration Project.
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 have been 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
The foundation of the installed wind turbines greatly depends on the type of sediment and the water depth of the proposed wind farm. Depending on these factors, there are six different foundation types that can be utilized; monopile, gravity, suction, jacket, twisted jacket, and finally floating foundations.
First, a monopile foundation is a relatively simple foundation type that has been used at many offshore wind projects. The monopile foundation is installed by pile driving a cylindrical tube into the seabed. These types of foundations work best in shallower waters, up to around 30 meters in depth.
(Image Credit: DNV GL)
Next, a gravity based foundation is a foundation that is a very large support structure, normally concrete based, which relies on the heavier foundation to forego pile driving. In addition, other benefits including using less steel, reducing costs, less requirements for specialized offshore vessels, less construction noise, and applications to increased water depths. Gravity foundations can be used in deeper waters and larger turbines than monopile foundations, with maximum water depths of up to 60 meters.
(Image Credit: DNV GL)
Suction caisson foundations, also known as buckets, skirted foundations, or suction anchors, have been commonly used by the offshore oil and gas industry, and proposed for offshore wind use. A suction caisson works by embedding essentially an upside down “bucket” into the marine sediment. When the water is pumped out of the bucket, this creates significant amounts of negative pressure on the foundation. Thus, this method has easier installation and generates less sound in the marine environment in comparison to other structures that require pile driving.
The next foundation is called a jacket (or lattice) structure. This foundation has three or four legs, each leg with its own smaller leg pile. The wind turbine is then placed on top of the support structure, known as the jacket. A primary benefit of a jacket foundation is there are significantly less wave loads. Jackets have been widely used in the oil and gas industry. In addition, there is a new type of jacket foundations, called the “twisted jacket.” This technology, developed by a U.S. company for meteorological towers and wind turbines, may greatly reduce the capital cost of foundations, and will be utilized by two Department of Energy demonstration projects (see below) in Virginia and New Jersey. These structures are well suited for waters between 20 and 50 meters, but could potentially be used in depths up to 70 meters.
(Image Credit: DNV GL)
Lastly, in waters too deep for fixed foundations like the ones above, floating turbines would be used. The three main types of floating include spar buoy, tension leg platform (TLP) and semi-submersible platforms. First, spar buoys are floating foundations with significant amounts of ballasts, which are then moored to the ocean floor to prevent the turbine from moving. One example of the spar buoy is the Hywind, a demonstration wind turbine located off the coast in Norway. Tension leg platforms are fixed to the ocean floor with cables pulled to tension. While these have been used for several decades in the offshore oil and gas industry, there are no current offshore wind projects utilizing tension leg platforms. Next, semi-submersible platforms are larger platforms stabilized by buoyancy and mooring cables. An example of this technology is the WindFloat turbine off the coast of Portugal. In addition the Windfloat turbine is planned to be used in a Department of Energy demonstration project off the coast of Oregon.
Notable Current Offshore Wind Farms:
Wind Farm Location Turbine Model Total MW Capacity Date of Operation
United Kingdom Siemens 3.6-120 630 2012
United Kingdom Siemens 3.6-107 504 2012
Denmark Siemens 3.6-120 400 2013
Germany Bard 5.0 400 2013
Belgium Repower 5MW, Repower 6.15MW 325 2009
Horns Rev 2
Denmark Siemens 2.3-93 209.3 2009
Sweden Siemens 2.3-93 110 2007
Egmond aan Zee
Netherlands V90-3MW 108 2006
Department of Energy Demonstration Projects
The Department of Energy recently selected seven offshore wind demonstration projects. These seven projects received $4 million dollars each to complete the first phase of the projects (e.g. engineering, site evaluation, planning, etc.). Of these seven projects, three were selected for further funding, eligible for $46.7 million over four years. The three projects are Dominion Virginia Power, Fishermen’s Energy Atlantic City, and Principle Power Windfloat in Oregon.