Environmental Engineering Reference
In-Depth Information
The offshore electrical service platform also provides a central service facility for the
wind power station and may include the following facilities:
-
helicopter landing pad
-
wind plant control room, staff and service facilities, and temporary living quarters
-
supervisory control and data acquisition monitoring systems
-
crane, rescue boat, and ireighting equipment
-
communication station
-
emergency diesel backup generators
Power is transmitted from the electrical service platform to shore through a number of buried
high-voltage sub-sea cables, where a shore-based interconnection point sends the power to
the grid. The voltage may need to be increased again onshore to (nominally) 345 kV for
offshore power plants larger than 500 MW [Green
et al.
2007].
Cost Trade-Offs
Currently, the
installed capital cost
(ICC) of an offshore wind power project is signii-
cantly higher than that of one with land-based wind turbines. Factors that contribute to this
additional cost are the costs of
marinizing
turbine components for service at sea, additional
costs for higher reliability components, and higher balance of station costs. In addition, opera-
tion and maintenance (O&M) costs are two to three times higher than for land-based systems.
This is partly because accessibility to turbines is more dificult, external conditions are more
severe and more dificult to measure and characterize, and extreme wind and wave loads add
substantial uncertainty to the design methods used on the turbines and substructures.
Higher offshore costs can be offset by higher offshore wind speeds, higher pricing for
electric energy near offshore wind plants, proximity to existing transmission grids, and avoid-
ed costs of building new transmission lines into heavily congested areas. Because offshore
wind technology is less mature than land-based wind energy, it has a greater potential for
cost reduction through technology development and innovation, and through learning-curve
reductions that take advantage of more eficient manufacturing and deployment processes.
Technology Development Pathways
The irst generation of offshore wind turbines was deployed using extrapolations of prov-
en land-based technology. However, a departure from land-based systems seems inevitable
as the technology evolves. Offshore systems must be more reliable, accessible from marine
vessels, designed to withstand a load regime consisting of dual dominate wind/wave spectra,
and larger in rated power and size to take advantage of the available offshore infrastructure.
In addition, as water depths increase with increasing distances from shore, loating wind
turbine foundations may need to be developed. These foundations will demand far-reaching
wind turbine innovations that incorporate lighter components and the ability to tolerate in-
creased tower delections and nacelle motions.
Figure 3-49 illustrates the pathway for offshore wind energy technology development,
beginning on land and progressing into shallow water (less than 30 m deep), where most of
the projects are located as of 2008. The one exception to this is a single demonstration proj-
ect deployed by
Talisman Energy
in 2006 in 45 m water depth near Aberdeen, Scotland. As
the industry gains experience through deployment of wind turbines in the shallower and more
sheltered sites, more projects will be sited farther from shore in deeper and deeper waters to
allow full exploitation of the wind resource. This progression to deeper water, possibly as
deep as 900 m, will require increasing levels of technical complexity and risk. The potential
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