The Largest-Capacity Offshore Wind Farms
1. London Array, 630 MW, Britain, completed in 2012. Located 20 kilometers off England�s east coast in the Thames Estuary, the London Array is the world�s largest offshore wind farm in terms of its power-producing capacity. The original lease was issued in 2003 to London Array Ltd., a consortium of E.ON UK Renewables, Shell WindEnergy and CORE Ltd. Shell pulled out in 2008, and subsequent investors were DONG Energy, Masdar and Canadian public pension-plan manager La Caisse. The wind farm consists of 175 Siemens 3.6-MW turbines and two offshore substations spread across an area of about 100 sq km. The monopile foundations were built by a joint venture of Per Aarsleff and Bilfinger Berger Ingenieurbau GmbH in water up to 25 meters deep. The piles are up to 68 m long, 5.7 m in dia and weigh 480 tonnes. The turbines were shipped from Denmark to the U.K. by barge. Construction began in March 2011, and it was fully operational by April 2013. The turbines were installed by MPI and A2SEA using two specialized vessels and a jack-up barge, Sea Worker. The turbine hubs are 80 m to 90 m tall, with the windmill blades reaching a height of 175 m. Two offshore substations, which boost the electricity voltage before it is exported, were designed, fabricated and installed by Future Energy, a joint venture made up of Fabricom, Iemants and Geosea. Two hundred and 10 kilometers of 33-kV subsea array cables and 220 km of 150-kV electrical export cables were installed by VSMC using underwater robotic vehicles.
London Array Ltd.
The workforce peaked at 1,000. The construction cost was $2.8 billion. A second phase consisting of 166 additional turbines was cancelled in 2014, after objections raised by the Royal Society for the Protection of Birds about the effect on red-throated divers.
London Array Ltd.
2. Gwynt y Mor,�576 MW, Britain, completed in�2015. Gwynt y Mor is Welsh for Sea Wind, and this wind farm is located off the northern coast of Wales. It is owned by a consortium of RWE Npower, Stadtwerke Munchen and Siemens. It consists of 160 Siemens 3.6-MW turbines. Construction started in January 2012 and final commissioning was completed in June 2015. A consortium made up of Bladt Industries A/S and EEW Special Pipe Construction Gmbh constructed the turbine foundations, which were installed by Seaway Heavy Lifting's vessel Stanislav Yudin. The turbine foundations consist of steel monopiles 6 meters in dia and between 45 m and 64 m long. Burntisland Fabrications Ltd. designed and manufactured foundation jacket structures for the wind farm�s two offshore substations. Siemens selected the Harland Wolff shipyard to fabricate the substations. Blue Water Shipping A/S transported the turbines from Denmark to the project site. A2Sea AS, a marine contractor, installed the turbines, towers and blades using two vessels, the Sea Jack and Sea Worker, in water ranging from 12 m to 33 m deep, at a site 18 kilometers offshore. The hub height is 98 m, and the rotor dia is 107 m. The construction cost was $3 billion.
RWE Innogy
3. Greater Gabbard, 504 MW, completed in 2012. Located 23 kilometers off England�s east coast, Greater Gabbard consists of 140 Siemens turbines and two offshore substations. It is currently owned by Scottish and Southern Energy and RWE Npower. Fluor performed design, supply, installation and commissioning. Fluor used Seajacks Ltd.�s vessel Leviathan, a 7,000-tonne jack-up lift boat, to install the turbines. Fluor contracted Seajacks and A2Sea to install the turbines in water between 20 meters and 32 m deep. Heerema Hartlepool Ltd. was the engineer-procure-construct contractor for the offshore substation platform. Seaway Heavy Lifting Ltd. transported and installed the substations. The hub height is 77 m, and the rotor dia is 107 m. The construction cost was $2.6 billion. There were two deaths of workers involved in the construction: A worker aboard a tugboat was killed after a chain broke, and a Siemens engineer died while a turbine blade was being loaded on the vessel Sea Jack.
Fluor Corp.
4. Anholt, 400 MW, completed in 2013. Located 21 kilometers off Denmark�s east coast, the Anholt Offshore Wind Farm is situated in the Kattegat, the body of water between Denmark and Sweden. It is owned by DONG Energy, Denmark�s largest energy firm, which performed the design and chose the specific layout, based on site investigations, wind measurement and sea-bed analysis. It consists of 111 Siemens 3.6-MW turbines, sited in water ranging from 14 meters to 17 m deep. A2SEA erected the turbines using the heavy-lift vessel Svanen to install the foundation monopiles. Each turbine weighs 460 tonnes: 18 tonnes for each of the three blades, 200 tonnes for the tower and 205 tonnes for the nacelle. Visser & Smit Marine Contracting installed the array cables using the vessel Stemat Spirit. Energinet.dk financed and built the offshore substation and connected the wind farm to the grid. The hub height is 81 m, the rotor dia is 120 m, and the total turbine height is 141 m. It cost $1.65 billion to build.
Dong Energy
5. BARD Offshore, 400 MW, completed in 2013. Germany's largest wind farm, BARD Offshore 1 is located in the North Sea 100 kilometers offshore, near the Netherlands border. BARD Engineering GmbH is the developer, and Ocean Breeze Energy GmbH & Co. KG, a subsidiary of Hypo Vereinsbank, is the owner. It is made up of 80 BARD 5-MW turbines situated in water 40 meters deep. The 470-tonne turbine foundations were placed on the sea bed by the vessel Wind Lift 1. Construction began in 2009 with cable laying. DeepOcean Subsea Services Ltd. handled the installation, trenching and connection of the array cables. BARD Building GmbH installed the triple-pile turbine foundations using 3.5-m-dia, 85-m-long piles. Hochtief Construction AG handled the installation of some turbines. Fred. Olsen Windcarrier AS installed the remaining turbines using its self-elevating jack-up vessel Brave Tern to install the nacelles and hubs with the blades attached. The hub height is 90 m, the rotor dia is 122 m, and total turbine height is 151 m. It cost $3.2 billion to construct. The farm was expected to go on line in August 2013, but problems, including a fire at a transmission station in March 2014, delayed its activation. Two workers, one of them a diver, died during construction.
BARD Engineering GmbH
6. Global Tech 1, 400 MW, completed September 2015. Located 115 kilometers off the German coast in the North Sea, the Global Tech 1 Wind Farm comprises 80 5-MW Areva turbines. Global Tech 1 Offshore Wind GmbH, whose shareholders include Stadtwerke Munchen GmbH, HSE AG, Axpo International S.A. and Exportes Offshore Beteiligungs GmbH, is the developer. Keppel Verolme BV installed the offshore substation. The 9,000-tonne substation was towed into position by two tugs. Hochtief Construction AG was the contractor for the turbines, and Fred. Olsen Renewables Ltd. carried out the transport and installation. The hub height is 90 meters, the rotor dia is 116 m, and the total turbine height is 148 m. The construction cost was $2 billion.
Global Tech 1 Offshore Wind GmbH
7. West of Duddon Sands, 389 MW, completed in 2014. Located 14 kilometers off England�s northwest coast, West of Duddon Sands Wind Farm comprises 108 Siemens 3.6-MW turbines. The wind farm is jointly owned by Scottish Power Renewables and DONG Energy, a Danish firm. The transmission assets�onshore and offshore substations and export cables�are owned by WoDS Transmission plc, a consortium composed of Macquarie Corporate Holdings Pty Ltd. and 3i Infrastructure plc. It is named after a large sand bank at the mouth of the River Duddon. CT Offshore installed the array cabling using the CLV Sia and Maersk Responder vessels. VBMS BV installed the two export cables using the Stemat Spirit vessel. GeoSea NV installed the substation. Scaldis Salvage & Marine Contractors� heavy-lift vessel Rambiz lifted and installed the 1,200-tonne substation jacket foundation. VolkerStevin Offshore installed some of the monopiles. Royal Boskalis Offshore BV installed scour protection before and after foundation installation. A2Sea�s jack-up vessel Sea Installer installed the turbines. Rotor dia is 120 m. It cost $2.4 billion to construct.
Scottish Power Renewables
8. Walney, 367.2 MW, completed in 2012. Located 14 kilometers off Walney Island near England�s northwest coast, Walney Wind Farm briefly was, in 2012, the highest-capacity offshore wind farm, before being surpassed by Greater Gabbard. It was developed in two phases, each one comprising 51 turbines. For phase one, VBMS BV used the Stemat 82 and Normand Mermaid vessels to lay the array cabling. Bladt Industries A/S fabricated and installed the offshore substation. Powerstream Electrical Services built the onshore substation at Heysham. GeoSea NV installed the monopile foundations using jack-up vessels Vagant and Goliath. Seajacks International Ltd. installed most of the turbines, using the Seajacks Kraken and Seajacks Leviathan vessels. The hub height is 83 km, the rotor dia is 107 meters, and the total turbine height is 137 m. The hub height of the phase-two turbines is 90 m, rotor dia is 120 m, and total turbine height is 150 m. The construction cost was $1.6 billion. DONG Energy is planning to install 207 additional turbines in two phases, bringing the generating capacity up to 750 MW. Construction of the extension is expected to begin in 2017.�
DONG Energy
9. Thorntonbank, 325 MW, completed in 2013. Located in the North Sea 30 kilometers off the Belgian coast, the Thorntonbank Wind Farm was built in three phases. In phase one, six REpower 5-MW turbines were installed on concrete gravity foundations and commissioned in 2009. In the second and third phases, 48 Senvion turbines, each 6.15 MW, were installed on steel jacket foundations. Phase two involved the installation of 30 turbines. In phase three, 18 turbines were installed. Thorntonbank was developed by C-Power, whose shareholders include two large energy companies, EDF Ernegies Nouvelles and RWE Innogy, as well as DEME, a maritime engineering firm and four investment funds: SRIW Environnement, Socofe, Z-Kracht and Marguerite Wind. The wind farm is sited in water between 12 meters and 27 m deep. The turbines� hubs are 157 m tall, and rotor dia is 126 m; they were installed by GeoSea, a subsidiary of DEME. The construction cost was $1.5 billion.
Wikimedia Commons/Hans Hillewaert
10. Sheringham Shoal, 317 MW, completed in 2012. Located 17 kilometers off England�s east coast in the North Sea, Sheringham Shoal Wind Farm was jointly developed by Statoil and Statkraft. It consists of 88 Siemens 3.6-MW turbines and two offshore substations. It is sited in water ranging from 12 meters to 24 m deep. The turbine foundations are 5-m-dia monopiles, 40 m to 60 m long and weighing between 375 tonnes and 531 tonnes each. MTH�jgaard was hired to install the foundations, but due to delays by its two transport vessels, the firm was terminated after installing 17 foundations. The remaining foundations were installed by Seaway Heavy Lifting using its heavy-lift vessel Oleg Strashnov. The construction cost was $1.8 billion.�
Wikimedia Commons/Havvindparken Sheringham Shoal/Harald Pettersen/Statoil
Offshore wind projects have faced tremendous resistance in the U.S. For example, a project called Cape Wind, a planned 127-turbine project off the Massachusetts coast, has faced permitting hurdles, political obstacles and lawsuits. What’s more, the five-turbine Fishermen’s Energy wind farm in offshore New Jersey has been hampered by state regulatory rejections over power-cost issues.
The first and only offshore wind farm to start construction in the U.S. is the Block Island Wind Farm, being built by Deepwater Wind off the coast of Rhode Island. A joint venture of Weeks Marine and Manson Construction last summer installed turbine-jacket foundations for the five-turbine, 30-MW first phase. The project is expected to begin generating power by late 2016.
All existing wind farms are located in waters less than 40 meters deep. To take advantage of the stronger winds in locations farther offshore, at least three firms are developing floating wind turbines that can be moored in deeper water.
Norway’s Statoil is planning to develop a 30-MW wind farm consisting of five floating turbines off the coast of Scotland. Seattle-based Principle Power, which has been operating a 2-MW pilot floating turbine off the coast of Portugal since 2011, is planning a 30-MW array off Oregon’s coast. And a consortium of Japanese universities, engineers and contractors is assembling a floating offshore wind-farm demonstration project off the coast of Fukushima.
View the above slide show for a look at the largest-capacity offshore wind farms across the globe.
This article was updated on Oct. 12, 2015.
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