Borgen (Sway) Copy_Outsourcing_book_temp.qxd 24/02/2010 10:50 Page 51
Floating Wind Power in Deep Water – Competitive with Shallow-water Wind Farms?
Table 1: Comparison of Approximate Weights and Costs of Tower/Foundation/Anchor for Jacket at 30m Water Depth and
Floating Systems at 120m Water Depth
1
Jacket at 30m Depth Sway Single-tension-leg Sway Upwind without Multiple-tension-leg Tri-floater
3 4
Floating Monopile Bracings, Slack Moorings at 120m Depth at 120m Depth
at 120m Depth at 120m Depth
Steel €/kg Cost Steel €/kg Cost Steel €/kg Cost Steel €/kg Cost Steel €/kg Cost
Weight (M€) Weight (M€) Weight (M€) Weight (M€) Weight (M€)
(te) (te) (te) (te) (te)
Turbine size 5MW 5MW 5MW 5MW 5MW
Tower 210 2.5 0.53 1,050 2.5 2.63 1,800 2.5 4.5 300 2.5 0.75 300 2.5 0.75
Foundation 500 5.8 2.9 N/A
2
N/A
2
650 5.8 3.77 2,000 5 10
Anchor wires/ N/A 50 5 0.25 40 5 0.2 150 5 0.75 N/A
wire bracings
Anchor chains/ N/A N/A 180 2 0.36 N/A 260 2 0.52
clump weights
Anchors/piles 315 2 0.63 90 2 0.18 150 2 0.3 600 2 1.2 200 2 0.4
Misc. anchor system N/A 50 0.5 0.4 0.8 0.4
Foundation and tower
installation costs 0.40 0.40 0.60 0.70 0.30
Total 1,025 4.46 1,240 3.96 2,170 6.36 1,700 7.97 2,760 12.37
Relative to jacket
at 30m 1 0.89 1.43 1.79 2.78
1.
www.alpha-ventus.de/index.php?id=80
2. Foundation integrated and included in tower weight.
3.
www.bluehusa.com/pressrelease3.aspx
4.
www.principlepowerinc.com/images/PrinciplePowerWindFloatBrochure.pdf
of these concepts and the safe dimensioning of the structures. This is
Figure 3: Side View of the Sway System
not an easy task that can be carried out in a few months; rather, it has
proved to require years of development and engineering effort.
A major factor to include when simulating the behaviour of a floating
wind turbine is the coupled motions of the system as a result of the
relative wind interacting with the wind turbine rotor and,
simultaneously, the waves interacting with the floating foundation.
Commercial simulation programs that can handle such coupled motion
of a floating wind turbine have not been readily available. This
necessitated the development of partly in-house computer codes during
the development of the first floating concepts over the last decade.
There are many good ideas ‘floating’ around regarding floating wind
turbine concepts, and it is not an easy task for future developers and
energy producers to evaluate which of the concepts will suit their
projects the best. Full-scale prototypes will have to be constructed,
most likely with participation from energy companies, prior to large-
scale commercial deployment. By participating in the operation of the
prototypes, energy companies may benefit from early market operation
experience and controlling the risk prior to constructing large
commercial windfarms in deep water.
Last year the first full-scale floating wind turbine was installed by Statoil
off the west coast of Norway. This concept, partly licensed to Statoil by
Sway, is similar to the Sway system in that it uses a monopile spar buoy
tower where the wind turbine tower is extended approximately 100m
below the surface. Heavy ballast is installed at the bottom of the tower,
bringing the centre of gravity below the centre of floatation; this gives
the tower sufficient stability to carry a 2.3MW wind turbine on top. This
very important full-scale prototype project will demonstrate that this
concept is safe and viable.
Several other floating wind turbine concepts such as the multiple-
tension-leg platform of Blue-H and the tri-floaters of Principal Power
and WindSea have been proposed. These initiatives are being funded
MODERN ENERGY REVIEW VOLUME 2 ISSUE 1
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