GIGAWIND alpha ventus

Holistic design concept for offshore wind turbine support structures

(Cooperative project of Leibniz Universität Hannover and Fraunhofer-Gesellschaft)

Homepage: www.gigawind.de

Main research questions

  • How can offshore WT support structures be improved in order to become an economic mass product?
  • What are the real and individual loadings of an offshore WT and how can they be measured and observed?
  • How can the life time of offshore structures be extended?
  • Which changes in the sea bed are expected by driven piles?

When planning an offshore wind turbine (WT), one of the biggest cost factors compared with onshore WTs is the support structure. In particular this aspect becomes more important since thousands of offshore WTs are planned in the North and Baltic Sea.

Project objective and project description

Priority objective of this project is the reduction of the cost for offshore WT support structures, which means towers, different types of substructures and foundations. This can be divided in designing lighter support structures on the one hand (material cost) and in optimising the design process on the other hand (personnel cost). Because of the interdisciplinary orientation of the project the coverage of all civil engineering problems is intended.

This is reflected in several work packages of the project:

  1. Load modelling for wind and waves and its correlation effects,
  2. Influence of manufacturing aspects on service life analysis,
  3. Corrosion protection for offshore steel structures,
  4. Reliable load monitoring at global and local parts of the structure,
  5. Development of new scour protection systems and local scour monitoring,
  6. Modelling of the load-carrying behaviour for driven offshore piles and
  7. Automated validation of general structural models.

Algorithms, new methods and software-tools will be developed and validated by measurement data from the test field. With a more efficient design process and by utilisation of design reserves the support structures can be provided more economically.

With the integration of separate computational tools into an easy operable simulation und design package with common interfaces the effort of the design process will be minimised. The holistic design concept for offshore WT support structures is build up in a modular way, so further extensions can easily be implemented.

Dimensioning an offshore WT support structure is a very complex engineering problem due to a very high number of influence parameters. While optimising the design structural the dimensioning has to comply with two demands:

  • safety
  • cost-effectiveness

Usually this is an iterative process and requires a very efficient simulation und design package as shown above.

 

Example for interfaces of software tools

In different parts of the GIGAWIND project tools for different design aspects are or will be made available, e. g. load models and validated general structural models. The software package provides interfaces between these tools saving time in the design process.

In this case an offshore WT shall be designed for the load case “sea state”. After modelling the general structural system with FEM or MKS the geometric information of the system as well as node coordinates will be given automatically to another tool, called WaveLoads. Within an internal routine WaveLoads calculates node loads from a design wave or specific sea state and gives the results back to the structural model. Then the structural analysis can be made using dynamical loading from WaveLoads.

Literature

  • Woltering, S.; Daemrich, K.-F.: Nonlinearity in irregular waves from linear LAGRANGEian superposition. Proceedings of 29th International Conference on Coastal Engineering, Lisbon, Portugal, ASCE, 2004.
  • Momber A.W.; Stenzel V.; Plagemann P.; Schneider M.: Combined Field - Laboratory Studies on Corrosion protection Conceptions for Offshore Windenergy Towers. 4th Intern. Symp. On Protective Coatings, Bombay, Nov. 2006.
  • Rolfes, R.; Lynch, J.; Gerasch, W.-J.; Haake, G.; Reetz, J.; Zerbst, S.: Integral SHM-System for Offshore Wind Turbines Using Smart Wireless Sensors. Proceedings of the 6th International Workshop on Struktural Health Monitoring, Stanford, 11.-13. September 2007, DEStech Publications, Inc., 2007.

Contacts and partners

Leibniz Universität Hannover

Institute of Structural Analysis
Prof. Raimund Rolfes
Appelstr. 9A, D-30167 Hannover
Tel.: +49 511 - 762 3867
www.isd.uni-hannover.de

Institute of Steel Construction
www.stahlbau.uni-hannover.de

Franzius-Institute
www.fi.uni-hannover.de

Institute for building materials

Institute for Geotechnical Engineering 
www.igbe.uni-hannover.de

Fraunhofer-Gesellschaft

Fraunhofer IWES
Dr. Holger Huhn
Am Seedeich 45
27572 Bremerhaven
+49 471 - 14290310
www.iwes.fraunhofer.de

Cooperation partner

Senvion SE 

Adwen GmbH