Offshore wind power

Offshore wind power

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Offshore wind power refers to the construction of wind farms
Wind farm
A wind farm is a group of wind turbines in the same location used to produce electric power. A large wind farm may consist of several hundred individual wind turbines, and cover an extended area of hundreds of square miles, but the land between the turbines may be used for agricultural or other...

 in bodies of water to generate electricity from wind
Wind power
Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships....

. Better wind speeds are available offshore compared to on land, so offshore wind power’s contribution in terms of electricity supplied is higher.

Siemens
Siemens
Siemens may refer toSiemens, a German family name carried by generations of telecommunications industrialists, including:* Werner von Siemens , inventor, founder of Siemens AG...

, REpower
REpower
REpower is a German wind turbine company founded in 2001, purchased December 2009 by Suzlon Energy Ltd. Its product range comprises several types of turbines with rated outputs of between 1.5 and 6 megawatts. It created the 5M, in 2005....

, and Vestas
Vestas
Vestas Wind Systems A/S is a Danish manufacturer, seller, installer, and servicer of wind turbines. It is the largest in the world, but due to very rapid growth of its competitors, its market share decreased from 28% in 2007 to 12.5% in 2009...

 are the leading turbine suppliers for offshore wind power. Dong Energy
DONG Energy
-History:The Danish state company Dansk Naturgas A/S was founded in 1972 to manage resources in the Danish sector of the North Sea. After some years, the company was renamed to Dansk Olie og Naturgas A/S . At the beginning of 2000s, DONG started to extend itself into the electricity market by...

, Vattenfall
Vattenfall
Vattenfall is a Swedish power company. The name Vattenfall is Swedish for waterfall, and is an abbreviation of its original name, Royal Waterfall Board...

 and E.on
E.ON
E.ON AG, marketed with an interpunct as E•ON, is the holding company of the world's largest investor-owned energy service provider based in Düsseldorf, Germany. The name comes from the Greek word aeon which means eternity....

 are the leading offshore operators. As of October 2010, 3.16 GW of offshore wind power capacity was operational, mainly in Northern Europe. According to BTM Consult
BTM Consult
BTM Consult is an independent consultancy company specializing in services pertaining to renewable energy commercialization. The company was founded in 1986 and named after founder Birger T. Madsen. Staff at BTM Consult have been working with wind power utilization since 1979.In March 2010, BTM...

, more than 16 GW of additional capacity will be installed before the end of 2014 and the United Kingdom and Germany will become the two leading markets. Offshore wind power capacity is expected to reach a total of 75 GW worldwide by 2020, with significant contributions from China and the United States.

Definition


Offshore wind power refers to the construction of wind farms
Wind farm
A wind farm is a group of wind turbines in the same location used to produce electric power. A large wind farm may consist of several hundred individual wind turbines, and cover an extended area of hundreds of square miles, but the land between the turbines may be used for agricultural or other...

 in bodies of water to generate electricity from wind
Wind power
Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships....

. Unlike the term typical usage of the term "offshore" in the marine industry, offshore wind power includes inshore water areas such as lakes, fjords and sheltered coastal areas, utilizing traditional fixed-bottom wind turbine technologies, as well as deep-water areas utilizing floating wind turbine
Floating wind turbine
A floating wind turbine is an offshore wind turbine mounted on a floating structure that allows the turbine to generate electricity in water depths where bottom-mounted towers are not feasible...

s.

History


Europe is the world leader in offshore wind power, with the first offshore wind farm being installed in Denmark in 1991. In 2008, offshore wind power contributed 0.8 gigawatt (GW) of the total 28 GW of wind power capacity constructed that year.
By October 2009, 26 offshore wind farms had been constructed in Europe with an average rated capacity of 76 MW, and as of 2010 the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 has by far the largest capacity of offshore wind farms with 1.3 GW, more than the rest of the world combined at 1.1 GW The UK is followed by Denmark (854 MW), The Netherlands (249 MW), Belgium (195 MW), Sweden (164 MW), Germany (92 MW), Ireland (25 MW), Finland (26 MW) and Norway with 2.3 MW.

As of October 2010, Danish
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

 wind turbine manufacturers Siemens Wind Power
Siemens Wind Power
Siemens Wind Power, or SWP, is a wind turbine manufacturer with headquarters and main production facilities established in 1980 in Brande, Denmark. SWP is wholly owned by Siemens of Germany since 2004 through the Renewable Energy division in the Siemens Energy sector...

 and Vestas
Vestas
Vestas Wind Systems A/S is a Danish manufacturer, seller, installer, and servicer of wind turbines. It is the largest in the world, but due to very rapid growth of its competitors, its market share decreased from 28% in 2007 to 12.5% in 2009...

 have installed 91.8% of the world's 3.16 GW offshore wind power capacity, although REpower
REpower
REpower is a German wind turbine company founded in 2001, purchased December 2009 by Suzlon Energy Ltd. Its product range comprises several types of turbines with rated outputs of between 1.5 and 6 megawatts. It created the 5M, in 2005....

 is now starting to become a major player. Based on current orders, BTM
BTM Consult
BTM Consult is an independent consultancy company specializing in services pertaining to renewable energy commercialization. The company was founded in 1986 and named after founder Birger T. Madsen. Staff at BTM Consult have been working with wind power utilization since 1979.In March 2010, BTM...

 expects 15 GW more between 2010 and 2014.

Offshore wind farms


As of 2010, there are 39 European offshore wind farms in waters off Belgium, Denmark, Finland, Germany, Ireland, the Netherlands, Norway, Sweden and the United Kingdom, with an operating capacity of 2,396 MW. More than 100 GW (or 100, 000 MW) of offshore projects are proposed or under development in Europe. The European Wind Energy Association
European Wind Energy Association
The European Wind Energy Association is an association based in Brussels, promoting the use of wind power in Europe. It has over 600 members from nearly 60 countries including manufacturers with a 90% share of the world wind power market, component suppliers, research institutes, national wind and...

 has set a target of 40 GW installed by 2020 and 150 GW by 2030.

As of November 2010, the Thanet Offshore Wind Project
Thanet Offshore Wind Project
The Thanet Wind Farm is an offshore wind farm off the coast of Thanet district in Kent, England. As of September 2010, it is the world's biggest offshore windfarm. It has a nameplate capacity of 300 MW and it cost £780-900 million...

 in United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 is the largest offshore wind farm in the world at 300 MW, followed by Horns Rev II (209 MW) in Denmark.
World's largest offshore wind farms
Wind farm
Wind farm
A wind farm is a group of wind turbines in the same location used to produce electric power. A large wind farm may consist of several hundred individual wind turbines, and cover an extended area of hundreds of square miles, but the land between the turbines may be used for agricultural or other...

 
Capacity
Nameplate capacity
Nameplate capacity, also known as the rated capacity, nominal capacity, installed capacity or maximum effect, refers to the intended technical full–load sustained output of a facility such as a power plant, a chemical plant, fuel plant, metal refinery, mine, and many others.For dispatchable power,...

 (MW)
Country Turbines
Wind turbine
A wind turbine is a device that converts kinetic energy from the wind into mechanical energy. If the mechanical energy is used to produce electricity, the device may be called a wind generator or wind charger. If the mechanical energy is used to drive machinery, such as for grinding grain or...

 and model
Commissioned References
Thanet
Thanet Offshore Wind Project
The Thanet Wind Farm is an offshore wind farm off the coast of Thanet district in Kent, England. As of September 2010, it is the world's biggest offshore windfarm. It has a nameplate capacity of 300 MW and it cost £780-900 million...

 
300  United Kingdom 100 × Vestas V90-3MW
Vestas V90-3MW
The Vestas V90-3MW is a three bladed upwind wind turbine generator that uses pitch control and a doubly fed induction generator...

 
2010
Horns Rev II
Horns Rev 2
Horns Rev 2 is an offshore wind farm located on Horns Rev in a shallow area in the eastern North Sea, about off the westernmost point of Denmark, Blåvands Huk...

 
209  Denmark 91 × Siemens
Siemens Wind Power
Siemens Wind Power, or SWP, is a wind turbine manufacturer with headquarters and main production facilities established in 1980 in Brande, Denmark. SWP is wholly owned by Siemens of Germany since 2004 through the Renewable Energy division in the Siemens Energy sector...

 2.3-93
2009
Rødsand II  207  Denmark 90 × Siemens
Siemens Wind Power
Siemens Wind Power, or SWP, is a wind turbine manufacturer with headquarters and main production facilities established in 1980 in Brande, Denmark. SWP is wholly owned by Siemens of Germany since 2004 through the Renewable Energy division in the Siemens Energy sector...

 2.3-93
2010
Lynn and Inner Dowsing  194  United Kingdom 54 × Siemens
Siemens Wind Power
Siemens Wind Power, or SWP, is a wind turbine manufacturer with headquarters and main production facilities established in 1980 in Brande, Denmark. SWP is wholly owned by Siemens of Germany since 2004 through the Renewable Energy division in the Siemens Energy sector...

 3.6-107
2008
Walney 1
Walney Wind Farm
Walney Wind Farm is an offshore wind farm currently under construction 14km west of Walney Island off the coast of Cumbria, in the Irish Sea, England. It is being developed by Walney Offshore Windfarms Limited, a partnership between Dong Energy and Scottish and Southern Energy. The farm is...

 
184  United Kingdom 51 × Siemens
Siemens Wind Power
Siemens Wind Power, or SWP, is a wind turbine manufacturer with headquarters and main production facilities established in 1980 in Brande, Denmark. SWP is wholly owned by Siemens of Germany since 2004 through the Renewable Energy division in the Siemens Energy sector...

 SWT-3.6-107
2011
Robin Rigg (Solway Firth)
Robin Rigg Wind Farm
Robin Rigg Wind Farm, Scotland's first offshore wind farm, has been constructed by E.ON at Robin Rigg in the Solway Firth, a sandbank midway between the Galloway and Cumbrian coasts. The windfarm first generated power for test purposes on 9 September 2009...

 
180  United Kingdom 60 × Vestas V90-3MW
Vestas V90-3MW
The Vestas V90-3MW is a three bladed upwind wind turbine generator that uses pitch control and a doubly fed induction generator...

 
2010
Gunfleet Sands
Gunfleet Sands Offshore Wind Farm
Gunfleet Sands Offshore Wind Farm 172MW wind farm 7 km off the Clacton-on-Sea and Holland Essex coast in the Northern Thames Estuary, commissioned on 15 June 2010. It has 48 Siemens Wind Power‎ wind turbines of 3.6 MW capacity each. Construction began in March 2008 and the first two turbines...

 
172  United Kingdom 48 × Siemens
Siemens Wind Power
Siemens Wind Power, or SWP, is a wind turbine manufacturer with headquarters and main production facilities established in 1980 in Brande, Denmark. SWP is wholly owned by Siemens of Germany since 2004 through the Renewable Energy division in the Siemens Energy sector...

 3.6-107
2010
Ormonde
Ormonde Wind Farm
The Ormonde Wind Farm is a wind farm west of Barrow-in-Furness in the Irish Sea. The wind farm covers an area of . It has a total capacity of 150 MW and is expected to produce around 500 GWh of electricity per year....

 
150  United Kingdom 30 × REpower 5M 2011


In Europe, as of June 2011, there were 1,247 grid-connected offshore wind turbines with a total capacity of 3,294 MW in 49 wind farms spread over nine countries. Offshore wind farms worth some €8.5 billion ($11.4 billion) are currently under construction in European waters. Once completed, they will represent an additional installed capacity of 2844 MW.

The province of Ontario in Canada
Wind power in Canada
As a means of pumping water and generating electricity in remote locations, wind power has a history in Canada dating back many decades, particularly on prairie farms. The amount of electricity generated by wind in Canada remains, however, small compared to other sources such as hydroelectricity...

 is pursuing several proposed locations in the Great Lakes
Great Lakes
The Great Lakes are a collection of freshwater lakes located in northeastern North America, on the Canada – United States border. Consisting of Lakes Superior, Michigan, Huron, Erie, and Ontario, they form the largest group of freshwater lakes on Earth by total surface, coming in second by volume...

, including the suspended Trillium Power Wind 1
Trillium Power Wind 1
Trillium Power Wind 1 is a proposed 414 megawatt offshore wind farm in Canadian waters of northeastern Lake Ontario developed by , a privately owned company headquartered in Toronto...

 approximately 20 km from shore and over 400 MW in size. Other Canadian projects include one on the Pacific west coast.

As of 2010, there are no offshore wind farms in the United States. However, projects are under development in wind-rich areas of the East Coast, Great Lakes, and Pacific coast.

Economics and benefits


Most entities and individuals active in offshore wind power believe that prices of electricity will grow significantly from 2009, as global efforts to reduce carbon emissions come into effect. BTM
BTM Consult
BTM Consult is an independent consultancy company specializing in services pertaining to renewable energy commercialization. The company was founded in 1986 and named after founder Birger T. Madsen. Staff at BTM Consult have been working with wind power utilization since 1979.In March 2010, BTM...

 expects cost per kWh to fall from 2014, and that the resource will always be more than adequate in the three areas Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 and China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

.

Offshore wind power can help to reduce energy imports, reduce air pollution and greenhouse gases (by displacing fossil-fuel power generation), meet renewable electricity standards, and create jobs and local business opportunities.

The current state of offshore wind power presents economic challenges significantly greater than onshore systems - prices can be in the range of 2.5-3.0 million Euro/MW. The turbine represents just one third to one half of costs in offshore projects today, the rest comes from infrastructure, maintenance, and oversight. Larger turbines with increased energy capture make more economic sense due to the extra infrastructure in offshore systems. Additionally, there are currently no rigorous simulation models of external effects on offshore wind farms, such as boundary layer stability effects and wake effects. This causes difficulties in predicting performance accurately, a critical shortcoming in financing billion-dollar offshore facilities. A report from a coalition of researchers from universities, industry, and government, lays out several things needed in order to bring the costs down and make offshore wind more economically viable:
  • Improving wind performance models, including how design conditions and the wind resource are influenced by the presence of other wind farms.
  • Reducing the weight of turbine materials
  • Eliminating problematic gearboxes
  • Turbine load-mitigation controls and strategies
  • Turbine and rotor designs to minimize hurricane and typhoon damage
  • Economic modeling and optimization of costs of the overall wind farm system, including installation, operations, and maintenance
  • Service methodologies, remote monitoring, and diagnostics.

Technical details


In 2009, the average nameplate capacity of an offshore wind turbine in Europe was about 3 MW, and the capacity of future turbines is expected to increase to 5 MW.

Offshore turbines require different types of bases for stability, according to the depth of water. To date a number of different solutions exist:
  • A monopile (single column) base, six meters in diameter, is used in waters up to 30 meters deep.
  • Gravity Base Structures, for use at exposed sites in water 20- 80 m deep.
  • Tripod piled structures, in water 20-80 metres deep.
  • Tripod suction caisson structures, in water 20-80m deep.
  • Conventional steel jacket structures, as used in the oil and gas industry, in water 20-80m deep.
  • Floating wind turbine
    Floating wind turbine
    A floating wind turbine is an offshore wind turbine mounted on a floating structure that allows the turbine to generate electricity in water depths where bottom-mounted towers are not feasible...

    s are being developed for deeper water.


Turbines are much less accessible when offshore (requiring the use of a service vessel for routine access, and a jackup rig
Jackup rig
A jack-up rig is a type of mobile platform that is able to stand still on the sea floor, resting on a number of supporting legs. The most popular designs use 3 independent legs, although some jackups have 4 legs or more...

 for heavy service such as gearbox replacement), and thus reliability
Reliability
In general, reliability is the ability of a person or system to perform and maintain its functions in routine circumstances, as well as hostile or unexpected circumstances.Reliability may refer to:...

 is more important than for an onshore turbine. A maintenance organization performs maintenance and repairs of the components, spending almost all its resources on the turbines. Access to turbines is by helicopter or service access vessel. Some wind farms located far from possible onshore bases have service teams living on site in offshore accommodation units.

Because of their remote nature, prognosis and health-monitoring systems on offshore wind turbines will be come much more necessary. They would enable better planning just-in-time maintenance, thereby reducing the operations and maintenance costs. According to a report from a coalition of researchers from universities, industry, and government, supported by the Atkinson Center for a Sustainable Future
Atkinson Center for a Sustainable Future
The David R. Atkinson Center for a Sustainable Future is a research organization created in Fall 2007 at Cornell University. ACSF advances multidisciplinary research in Energy, the Environment and Economic Development, and cultivates collaborations within and beyond Cornell.- History :ACSF,...

, making field data from these turbines available would be invaluable in validating complex analysis codes used for turbine design. Reducing this barrier would contribute to the education of engineers specializing in wind energy.

The planning and permitting phase can cost more than $10 million, take 5–7 years and have an uncertain outcome. The industry puts pressure on the governments to improve the processes. In Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...

, many of these phases have been deliberately streamlined by authorities in order to minimize hurdles.

Some of the guidelines for designing offshore wind farms are IEC 61400
IEC 61400
IEC 61400 is a class of IEC international standards regarding wind turbines.-Purpose and function:The 61400 is a set of design requirements made to ensure that wind turbines are appropriately engineered against damage from hazards within the planned lifetime...

-3.

Design Environment


Offshore wind resource characteristics span a range of spatial and temporal scales and field data on external conditions. Necessary data includes water depth, currents, seabed, migration, and wave action, all of which drive mechanical and structural loading on potential turbine configurations. Other factors include marine growth, salinity, icing, and the geotechnical characteristics of the sea or lake bed. A number of things are necessary in order to attain the necessary information on these subjects. Existing hardware fore these measurements includes Light Detection and Ranging (LIDAR), Sonic Detection and Ranging (SODAR), radar, autonomous underwater vehicles (AUV), and remote satellite sensing, although these technologies should be assessed and refined, according to a report from a coalition of researchers from universities, industry, and government, supported by the Atkinson Center for a Sustainable Future
Atkinson Center for a Sustainable Future
The David R. Atkinson Center for a Sustainable Future is a research organization created in Fall 2007 at Cornell University. ACSF advances multidisciplinary research in Energy, the Environment and Economic Development, and cultivates collaborations within and beyond Cornell.- History :ACSF,...

.

Because of the previous factors, one of the biggest difficulties with offshore wind farms is the ability to predict loads. Analysis must account for the dynamic coupling between translational (surge, sway, and heave) and rotational (roll, pitch, and yaw) platform motions and turbine motions, as well as the dynamic characterization of mooring lines for floating systems. Foundations and substructures make up a large fraction of offshore wind systems, and must take into account every single one of these factors.

Aesthetics


Offshore wind turbines are less obtrusive than turbines on land, as their apparent size and noise is mitigated by distance. A 2006 Survey by the University of Delaware near the proposed Cape Wind
Cape Wind
The Cape Wind Project is an approved offshore wind farm, on Horseshoe Shoal in Nantucket Sound off Cape Cod in the U.S. state of Massachusetts, proposed by a private developer, Cape Wind Associates, the brainchild of Jim Gordon and a Limited Liability Company set up as a joint business venture...

development found that residents most frequently based their decisions to support or oppose the wind farm on perceived impacts to marine life, the environment, electricity rates, aesthetics, fishing and boating.