Standards and Practices - Structural Integrity of Offshore Wind Turbines - page 54

is mainly concerned with preventing plastic collapse, while design of
offshore wind turbines is more concerned with preventing failure due
to resonance and fatigue.

• Offshore wind turbines are expected to increase in size from about

3 MW per turbine today to possibly 10 MW over the next decade. The
scaling up of turbine size may introduce effects not anticipated or cov-
ered by any of the current standards.

• Significant experience has been gained since the current IEC offshore

wind standards were written. The experience has improved the knowl-
edge base with respect to design requirements for turbine support struc-
tures and has led to refinements in design methodologies. Much of this
experience has not yet been incorporated into the standards. Moreover,
the causes of recent technical failures in foundations and grouted con-
nections and the design requirements to avoid such failures are still
being analyzed, so they are likewise not reflected in current standards.

• Floating wind turbine systems are not addressed adequately in any of

the current standards. IEC is considering a proposal to write a techni-
cal specification on floating wind turbine systems (IEC 2010a). (Bureau
Veritas has just released guidelines for the “Classification and Certifica-
tion of Floating Offshore Wind Turbines,” but the committee was not
able to review them for this project.)

FINDINGS FOR TASK I: CHAPTER 3

Findings for Chapter 3 appear below. They address Task I of the statement
of task. Chapter 4 also addresses Task I. A full set of recommendations for
Task I appears at the end of Chapter 4.

1. Regulations in most countries—notably in continental Europe—take a
prescriptive approach, regulating in detail the design, construction, and
operation of offshore wind turbines to achieve acceptable levels of
safety, environmental performance, and reliability.
2. The starting points for most of the offshore wind energy regulations and
guidelines (for example, those of DNV, GL, ABS, BSH, AWEA, and
the Danish Energy Agency) are IEC 61400-1 ( Wind Turbines—Part 1:
Design Requirements ) and IEC 61400-3 ( Wind Turbines—Part 3: Design
Requirements for Offshore Wind Turbines ). The IEC standards do not