A
floating wind turbine is a
wind turbineA wind turbine is a rotating machine which converts the kinetic energy of wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill...
mounted on a floating structure that allows the turbine to generate
electricityElectricity is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge...
in water depths where bottom-mounted towers are not feasible. The
windWind is the flow of air or other gases that compose an atmosphere . On Earth, wind consists of the bulk movement of air...
can be stronger and steadier over water due to the absence of topographic features that may disrupt wind flow. The electricity generated is sent to shore through undersea cables. The initial capital cost of floating turbines is competitive with bottom-mounted, near-shore wind turbines while the rate of energy generation is higher out in the sea as the wind flow is often more steady and unobstructed by terrain features. The relocation of wind farms into the sea can reduce
visual pollutionVisual pollution is the term given to unattractive and man-made visual elements of a vista, a landscape, or any other thing that a person does not feel comfortable to look at. Visual pollution is an aesthetic issue, referring to the impacts of pollution that impair one's ability to enjoy a vista or...
if the windmills are sited more than offshore, provide better accommodation of fishing and shipping lanes, and allow siting near heavily developed coastal cities.
Floating wind parks are wind farms that site several floating wind turbines closely together to take advantage of common infrastructure such as power transmission facilities.
History
The concept for "large-scale offshore floating wind turbines was introduced by Professor William E. Heronemus at the
University of MassachusettsThe University of Massachusetts is the five-campus public university system of the Commonwealth of Massachusetts....
in 1972. [I]t was not until the mid 1990’s, after the
commercial wind industryWind power is the conversion of wind energy into a useful form of energy, such as electricity, using wind turbines. At the end of 2008, worldwide nameplate capacity of wind-powered generators was 121.2 gigawatts . In 2008, wind power produced about 1.5% of worldwide electricity usage; and is...
was well established, that the topic was taken up again by the mainstream research community." As of 2003, existing offshore fixed-bottom wind turbine technology deployments had been limited to water depths of 30-meters. Worldwide deep-water wind resources are extremely abundant in
subseaSubsea is a general term frequently used to refer to equipment, technology, and methods employed to explore, drill, and develop oil and gas fields that exist below the ocean floors...
areas with depths up to 600 meters, which are thought to best facilitate
transmissionElectric power transmission is the bulk transfer of electrical energy, a process in the delivery of electricity to consumers. A power transmission network typically connects power plants to multiple substations near a populated area...
of the
generated electric powerSubmarine power cables are cables for electrical power running through the sea, below the surface.A DC system may use the ground and seawater as a return path for current. However, this cannot be always practiced because of disturbances to magnetic compass systems on vessels crossing the cable and...
to shore communities.
Operational deep-water platforms
, there have been only two operational floating wind turbines used to farm wind energy over deep-water.
Blue H deployed the first floating wind turbine off of the coast of Italy in December, 2007. It was then decommissioned at the end of 2008 after completing a planned test year of gathering operational data.
The first large-capacity, 2.3 megawatt floating wind turbine is
Hywind, which became operational in the
North SeaThe North Sea is a marginal, epeiric sea on the European continental shelf. The Dover Strait and the English Channel in the south and the Norwegian Sea in the north connect it to the Atlantic Ocean. It is more than long and wide, with an area of around...
off of
NorwayNorway , officially the Kingdom of Norway, is a country in Northern Europe occupying the western portion of the Scandinavian Peninsula, as well as Jan Mayen and the Arctic archipelago of Svalbard under the Spitsbergen Treaty...
in September, 2009 and is still operational .
Blue H Technologies
Blue H Technologies of the
NetherlandsThe Netherlands is a country in Northwestern Europe, constituting the major portion of the Kingdom of the Netherlands. It is a parliamentary democratic constitutional monarchy. The Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east...
operated a prototype deep-water platform with an 80-kilowatt turbine off of Puglia, southeast
ItalyItaly , officially the Italian Republic , is a country located on the Italian Peninsula in Southern Europe and on the two largest islands in the Mediterranean Sea, Sicily and Sardinia. Italy shares its northern, Alpine boundary with France, Switzerland, Austria and Slovenia...
in 2008. Installed 21 km off the coast in waters 113 meters deep in order to gather test data on wind and sea conditions, the small prototype unit was decommissioned at the end of 2008. Blue H has successfully decommissioned the unit as it embarks on plans to build a 38-unit deepwater wind farm at the same location.
The Blue H technology utilizes a
tension-leg platformA Tension-leg platform or Extended Tension Leg Platform is a vertically moored floating structure normally used for the offshore production of oil or gas, and is particularly suited for water depths greater than 300 metres and less than 1500 meters...
design and a two-bladed turbine. The two-bladed design can have a "much larger
chordIn aeronautics, chord refers to the imaginary straight line joining the trailing edge and the center of curvature of the leading edge of the cross-section of an airfoil...
, which allows a higher tip speed than those of three-bladers. The resulting increased background
noiseNoise pollution is displeasing human-, animal- or machine-created sound that disrupts the activity or balance of human or animal life. The word noise comes from the Latin word nausea meaning seasickness....
of the two-blade rotor is not a limiting factor for offshore sites."
, Blue H is building the first full-scale commercial 2.4 MW
e unit in Brindisi, Italy which it expects to deploy at the same site of the prototype in the southern
Adriatic SeaThe Adriatic Sea is a body of water separating the Italian Peninsula from the Balkan peninsula, and the system of the Apennine Mountains from that of the Dinaric Alps and adjacent ranges. The Adriatic Sea is a part of the Mediterranean Sea...
in 2010. This is the first unit in the planned 90 MW
Tricase offshore wind farm, located more than 20 km off the Puglia coast line.
Hywind
The world's first operational deep-water floating
large-capacity wind turbine is the Hywind, in the
North SeaThe North Sea is a marginal, epeiric sea on the European continental shelf. The Dover Strait and the English Channel in the south and the Norwegian Sea in the north connect it to the Atlantic Ocean. It is more than long and wide, with an area of around...
off of
NorwayNorway , officially the Kingdom of Norway, is a country in Northern Europe occupying the western portion of the Scandinavian Peninsula, as well as Jan Mayen and the Arctic archipelago of Svalbard under the Spitsbergen Treaty...
. The Hywind, constructed by
SiemensSiemens AG is a German electrical and telecommunications companysiemens may refer to*siemens , the SI unit of electrical conductance, equivalent to 1 ampere/voltSiemens may also refer to:...
, was towed out to sea in early June 2009. The turbine is owned by
StatoilHydroStatoilHydro ASA is a Norwegian energy company, formed by the 2007 merger of Statoil with the oil and gas division of Norsk Hydro. StatoilHydro is the biggest offshore oil and gas company in the world and the largest company by revenue in the Nordic Region...
. This 2.3 megawatt turbine has a 100 metre deep draft and will be tested there for two years. After assembly in the calmer waters of Amoy Fjord near
Stavanger, Norwayis a city and municipality in the county of Rogaland, Norway. Stavanger was established as a municipality 1 January 1838...
, the 120-meter-tall tower with a 2.3 MW turbine was towed 10 km offshore into 220-meter-deep water, 10 km southwest of
KarmøyKarmøy is a municipality in Rogaland county, Norway. It is located southwest of the city of Haugesund. Karmøy was created as a new municipality on 1 January 1965 after the merger of Kopervik , Skudeneshavn , Skudenes, Stangaland, Torvastad, Åkra, and most of Avaldsnes.-Name:The Old Norse form of...
, on for a two year test deployment." Alexandra Beck Gjorv of StatoilHydro said, "[The experiment] should help move offshore wind farms out of sight ... The global market for such turbines is potentially enormous, depending on how low we can press costs." The unit became operational in the summer of 2009. Hywind was inaugurated on 8 September 2009.
The turbine cost US$62 million to build. The 13-kilometer (8-mile) long
submarine power transmission cableSubmarine power cables are cables for electrical power running through the sea, below the surface.A DC system may use the ground and seawater as a return path for current. However, this cannot be always practiced because of disturbances to magnetic compass systems on vessels crossing the cable and...
was installed in July, and system test including rotor blades and initial power transmission was conducted shortly thereafter.
Topologies
Platform topologies can be classified into:
- single-turbine-floater (one wind turbine mounted on a floating structure)
- multiple turbine floaters (multiple wind turbines mounted on a floating structure)
Economics
"Technically, the [theoretical] feasibility of deepwater [floating] wind turbines is not questioned as long-term survivability of floating structures has already been successfully demonstrated by the marine and offshore oil industries over many decades. However, the economics that allowed the deployment of thousands of offshore oil rigs have yet to be demonstrated for floating wind turbine platforms. For deepwater wind turbines, a floating structure will replace pile-driven monopoles or conventional concrete bases that are commonly used as foundations for shallow water and land-based turbines. The floating structure must provide enough buoyancy to support the weight of the turbine and to restrain pitch, roll and heave motions within acceptable limits. The capital costs for the wind turbine itself will not be significantly higher than current marinized turbine costs in shallow water. Therefore, the economics of deepwater wind turbines will be determined primarily by the additional costs of the floating structure and power distribution system, which are offset by higher
offshore windsWind resource assessment is the process by which wind power developers estimate the future energy production of a wind farm. Accurate wind resource assessments are crucial to the successful development of wind farms.- History :...
and close proximity to large load centers (e.g. shorter transmission runs)."
however, the economic feasibility of shallow-water offshore wind technologies is more completely understood. With empirical data obtained from fixed-bottom installations off many countries for over a decade now, representative costs are well understood. Shallow-water turbines cost between 2.4 and 3 million
United States dollarThe United States dollar is the unit of currency of the United States. The U.S. dollar is normally abbreviated as the dollar sign, $, or as USD or US$ to distinguish it from other dollar-denominated currencies and from others that use the $ symbol. It is divided into 100 cents .The U.S...
s per megawatt to install, according to the
World Energy CouncilThe World Energy Council is a multi-energy international organization covering all types of energy, including coal, oil, natural gas, nuclear, and renewables. Established in 1923, the WEC has now Member Committees established in 94 countries....
.
The practical feasibility and per-unit economics of deep-water, floating-turbine offshore wind is yet to be seen. Initial deployment of single full-capacity turbines in deep-water locations is only just beginning in the summer of 2009.
WindFloat
WindFloat is a patent pending floating foundation for offshore
wind turbineA wind turbine is a rotating machine which converts the kinetic energy of wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill...
s aimed at improving dynamic stability. The WindFloat design is intended to dampen wave and turbine induced motion utilizing a tri-column triangular platform with the wind turbine positioned on only one of the three columns. The triangular platform is then "moored with 6 lines, 4 of which are connected to the column stabilizing the turbine, thus creating an asymmetric" mooring to increase stability and reduce motion. This technology could allow wind turbines to be sited in offshore areas that were previously considered inaccessible, areas having water depth exceeding 50 meters and more powerful wind resources than shallow-water offshore wind farms typically encounter.
As of February 2009, there are preliminary plans for the phased development of a deep-water offshore
wind farmA wind farm is a group of wind turbines in the same location used for production of electric power. Individual turbines are interconnected with a medium voltage power collection system and communications network...
off the coast of
PortugalPortugal , officially the Portuguese Republic , is a country located in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of mainland Europe and is bordered by the Atlantic Ocean to the west and south and by Spain to the north and east...
using WindFloat technology.
Nautica Windpower
Nautica Windpower’s floating wind turbine concept is currently undergoing scale model tests and design optimization. The patent pending technology features an asymmetric tower with a single mooring line and a downwind articulated rotor configuration that passively aligns with the wind. In contrast to the offshore-oil-platform-based technology, Nautica follows a design philosophy of lower weight, deflection tolerance, and dynamic load alleviation.
External links