Standards and Practices - Structural Integrity of Offshore Wind Turbines - page 51

have to identify applicable standards from other industries and adapt
them to cover these activities. Qualification testing will be treated as
an overarching activity that may be applied to any project phase.
Group 3, Operation, Maintenance, and Decommissioning, is developing
recommended practices for operation and inspection. The recom-
mendations are not likely to include extensive turbine component
inspection; owner-investor wind farm maintenance systems are
generally more comprehensive than periodic inspections that could
be carried out by BOEMRE or other federal agencies, and the con-
sequences of failure in a secondary component are generally limited
to economic risk to the wind farm itself. However, in-service struc-
tural inspection of the tower and the substructure or below the
waterline will be necessary over the field service life. Conservatively,
the design life of the substructure is 20 years, but designs could allow
repowering scenarios where foundations could be reused. In any
case, foundation and substructure design should consider removal
and disposition of the system when it is no longer serviceable.
IEC Floating Wind Turbine Initiative
There is strong interest worldwide in the development of new technol-
ogy for deeper water. Such technology may include floating support
structures for wind turbines. Only one floating wind turbine has been
deployed to date, by Statoil in Norway in 2009, but technology develop-
ment is accelerating, and permits for prototypes in U.S. waters will soon
be sought (Maine Public Utilities Commission 2010). In May 2011, IEC
TC 88 approved a project to develop an IEC technical specification for
the design of floating wind turbines. The forecast publication date is
January 2013 (IEC 2011).
Bureau Veritas Guidance for Floating Offshore Wind Turbines
In January 2011, Bureau Veritas issued guidelines for the “Classification
and Certification of Floating Offshore Wind Turbines.” The guidelines
specify the environmental conditions under which floating offshore
wind turbines may serve, the principles of structural design, load cases
for the platform and mooring system, stability and structural division,