Environmental Engineering Reference
In-Depth Information
CHAPTER 13
and structural design
Bent F. Sørensen , John W. Holmes , Povl Brøndsted & Kim Branner
Risø National Laboratory for Sustainable Energy
The Technical University of Denmark.
A major trend in wind energy is the development of larger wind turbines for
offshore wind farms. Since access to offshore wind turbines is diffi cult and costly,
it is of great importance that they operate safely and reliable. The wind turbine
rotor blades, which are the largest rotating component of a wind turbine, are
designed for an expected lifetime of 20 years. During this period of time, the
blades will be subjected to varying loads. Large wind turbine blades are made of
composite materials and can develop a number of interacting failure modes. High
structural reliability can be achieved by designing the blades against the develop-
ment of these failure modes. This chapter provides an overview of experimental
and modeling tools for the design of wind turbine blades, with particular emphasis
on evolution and interaction of various failure modes. This involves knowledge of
materials, testing methods and structural design.
1 Introduction
Structural design of wind turbine blades for horizontal axis wind turbines is a
complicated process that requires know-how of materials, modeling and testing
methods. A wind turbine blade must be designed against undesired aero-elastic
phenomena and failures for a great variety of aerodynamic load cases and environ-
mental conditions. Thus, the design process involves a number of different areas,
such as knowledge of the external loads originating from wind and gravity and
knowledge of the performance, the strength and the endurance of the full structure
and of the basic materials used. The goal of the design process is to ensure that
the wind turbine blade will function safely for its design life. The design lifetime of
modern wind turbines is normally thought to be 20 years, and the corresponding
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