Steel materials for wind turbines

Electricity from wind is the strongest pillar for the transformation into a sustainable electrical energy generation system in Germany. For the construction of wind turbines, steel is an in- dispensable material that has a significant weight share in the overall system. In offshore wind energy, the portion is over 85%, with one turbine having a total weight of about 1500 tons. It is therefore understandable that the steel producing and steel processing industries have a vital interest in research and development in this comparatively young technical field. This applies to steel support structures, components of the machine, various types of con- necting devices and other components.

The overall objective of research and development is the effective and efficient production, construction and operation of wind energy parks.

The special challenges in wind energy lie in the highly dynamic load on the components and in the ever-increasing plant height and size, which is currently approaching the 10 MW limit per turbine. In offshore wind turbines, the extremely adverse environmental conditions must also be considered. The design has to ensure the highest demands on load bearing and fatigue resistance, functionality and robustness. Here, the fluctuating stresses from wind and operation must be taken into account; offshore is a mixture of demands from waves, current and in the Baltic Sea; ice drift. These special requirements define the current research topics in the field of steel application research for wind energy.

It is obvious that when it comes to the construction material steel, structure-mechanical problems dominate. A special challenge is the fatigue behaviour. For bolted, welded and hybrid connections, reliable and economical solutions have to be developed which are able to cope with the high cyclic stress and load cycles with increasing component thicknesses. In order to meet the peculiarity of series production, automated production processes are to be striven for, which exploit the possibilities of digitalisation. For the offshore sector, corrosion protection and installation technology are among the special topics. Furthermore, the choice of materials is relevant. For the operating time of the systems, monitoring systems are to be devel- oped which ensure safe plant operation and enable early damage detection in order to minimise the expense for repairs.

Precompetitive steel application research has recently produced new developments in the field of wind energy in particular in the field of welding processes, post weld after treatment and bolting technology, thus making valuable contributions to the change in the energy supply system.

Peter Schaumann, Natalie Stranghöner, Wilko Flügge

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