The large wind turbine was designed by Norwegian-based company Sway. Its buoyancy is due to the internally hollow tower support, and it will be anchored to the seabed to depths of several hundred metres with a single pipe and a suction anchor
State company Enova has allocated 17 million euros for the construction of the largest floating wind turbine designed for offshore wind farms.
This prototype, developed by Sway, has a capacity of 10 MW and is equipped with a rotor having a diameter of 145 metres. The wind turbine will have to be tested onshore for two years before being installed in the North Sea.
Unlike most wind farms which are based directly on the seabed (up to a maximum depth of 60-70 meters) the Sway turbine floats and can therefore be installed offshore at depths of several hundred meters.
This implies a substantial difference in terms of generated energy, since in Norway, for example, winds blowing about 50 km off the coast (where depths typically range from 100 up to 300 meters) are approximately 25% stronger and more constant than in areas up to 15 km off the coast, where the largest power plants were built up to now.
The buoyancy of the new wind turbine is based on the large internally hollow supporting tower, which extends below the water surface and is filled with ballast, thus having sufficient stability to resist wind loads. The structure is anchored to the seabed also by means of lateral suction anchors, allowing the tower to tilt a few degrees and to turn around, so as to harness more energy from winds, while reducing excessive structural tensions.
According to Sway designers, the wind turbine’s features allow it to be more efficient in terms of wind power production and less costly in terms of operational management.
The system was designed to withstand extreme conditions at sea. Sway guarantees a minimum life span of 20 years and the ability to withstand the impact of a tidal wave of over 30 meters.
Sway AS is renewable energy company on course to revolutionize wind energy design, in particular for offshore installations. This is based on two extraordinary inventions and their synergy, namely a game-changing 10MW ultra light-weight gearless wind turbine, under development by Sway since 2004, combined with a unique, down-wind floating tower for deep water deployment developed since 2002. In addition to carrying the 10MW turbine under development by Sway the floating tower is also capable of carrying commercially available offshore wind turbines in the 5MW class. Sway has therefore entered into a partnership with Areva-Multibrid for the adaptation of their 5MW turbine to the floating Sway tower. In this manner the future customers of the floating Sway towers will have several options with regards to choice of turbine.
The patented SWAY® system enables low cost access to deepwater locations far offshore where the average wind speed is higher and where the location of turbines will be less controversial.
SWAY’s floater technology allows economical extraction of wind power in nations with good wind resources and access to water depths of 80-400m within 50-60km from the coast. The
10MW turbine may be deployed on conventional fixed foundations as well as on the Sway floating towers. The outcome is improved cost efficiency for both fixed and floating wind parks due to reduced consumption of materials, fewer turbines for the same output of extracted energy, and fewer electric interconnections, indicating substantially increased annual energy yield for the same total amount of investment in addition to reduced O&M costs.
The market potential worldwide is huge and SWAY aims to transform its technological edge to commercial success as the demand for renewable energy rises.
The SWAY technology will open up large new areas worldwide for harvesting wind energy. The medium to long term market potential is significant, comprising both electrification of offshore oil & gas installations and export to the onshore electricity market.
Wind power production can be more efficient in deep water locations due to the presence of consistently higher average wind speeds. At 50 km off the coast of Norway, where the water depth is typically between 100-300m, the power production from each wind turbine would be 20-30% higher than the same wind turbine located at the Horn’s Reef installation situated some 15 km off the west coast of Denmark. This improvement is simply due to the greater and more consistent winds further offshore.
Electrification of oil & gas installations
The SWAY® system is a viable solution for the electrification of oil & gas platforms with electricity production costs, including capital costs, well below the operational costs alone for the gas and diesel turbines used currently in the offshore industry. A detailed case study for the integration of wind power to an oil platform off the coast of Norway was successfully completed in 2004. The study concludes that it is both technically and economically feasible to integrate wind power with the existing gas and diesel generators on the offshore oil & gas platforms. The benefits of this integration would be savingsin the form of lower electricity costs and reduced emissions.
Export to onshore electricity market
SWAY’s technology has the potential of providing Norway and several other countries (including USA, Japan, Ireland, Spain, Portugal and Italy) economical access to an unlimited energy source with no pollution and minimal environmental controversy.
8 years of intensive advanced dynamic simulations and engineering has enabled us to discover nature’s own secrets of how to make our two technologies feasible both technically and economically.
The Sway Floater:
The patented SWAY system is based on a floating tower which extends far below the water surface. The tower consists of a floating pole with ballast in the lower end, similar to a floating bottle. The tower, which is filled with ballast, has its center of gravity located far below the center of buoyancy of the tower. This gives the tower sufficient stability to resist the large loads produced by the wind turbine mounted on top of it.
The floating tower is anchored to the seabed with a single pipe and a suction anchor. When the wind hits the rotor the tower is tilting some 5-8 degrees. By tilting the rotor the opposite way which is made possible by placing the rotor downwind of the tower the rotor is kept perfectly aligned with the wind. When the wind changes direction, the entire tower turns around a subsea swivel. This, in turn, makes it possible to reinforce the tower with a tension rod system similar to wire stays on a sailboat mast. Due to the resulting reduction of stresses in the tower, the tower is capable of carrying a much larger turbine, which greatly enhances the total economy.
The SWAY® systems will be operating in some of the worlds roughest offshore locations, and has been designed to satisfy the strictest regulations for offshore wind turbines and installations. For example, our floater has been designed to withstand impact with a once in a 100-year wave of over 30 m and have a fatigue lifespan of over 20 years. SWAY A/S has, together with its engineering partners, developed advanced calculation software to simulate the loads and dynamics of the entire floating system and our 10MW turbine under development. In addition, Garrad Hassan & Partners Ltd in Bristol (UK) has carried out independent dynamic analyses of the SWAY system. Sway is using DnV for the certification of the Sway system.
The Sway Turbine:
The 10 MW turbine may be deployed on conventional fixed foundations as well as on the Sway floating towers. The outcome is improved cost efficiency for both fixed and floating wind farms due to reduced consumption of materials, fewer turbines for the same output of extracted energy, and fewer electric interconnections, indicating substantially increased annual energy yield for the same total amount of investment in addition to reduced O&M costs.
