Innovative foundation system for repowering offshore wind turbines – InGROW

Funding: Federal Ministry for Economic Affairs and Energy (BMWi)
Funding amount: 550,067.00 EUR
Partner: Fraunhofer IWES
Duration: 03/2019 - 08/2021


  • Wind turbines at sea are designed for a service life of 20 years. After that, they must be dismantled if further operation is not technically or economically possible.
  • One alternative to this is repowering, where old wind turbines are replaced with new, more powerful ones at the same site.
  • In order to use the existing foundation structures, as part of the InGROW project, the Fraunhofer IWES is developing a foundation concept which involves the strengthening of existing monopiles to enable offshore wind turbines to be repowered.

Wind turbines on land and at sea are designed for a service life of 20 years. This is primarily due to the state price guarantee, which runs for 20 years. After this time, the parks can continue to be operated (lifetime extension) if this is technically and economically feasible. If not, they have to be dismantled. The planning of dismantling is a requisite part of the approval procedure.

The Fraunhofer IWES is currently developing a third alternative for offshore wind farms: repowering using the existing foundation structure. Repowering involves replacing old turbines with new, more powerful ones. Since known sites are used, the numerous time-consuming exploratory activities are not necessary. In addition, there is already a grid connection. The option of using an existing monopile foundation (a pile foundation driven deep into the seabed) cuts costs considerably.

However, new wind turbines are generally heavier than older ones and subject the foundation structure to entirely new loads for which it is not designed. The InGROW research project is focused on the development of a foundation concept which reinforces the existing monopiles and thus allows repowering without having to replace the foundation structure completely. In this project, physical tests on foundation models are being carried out and accompanied by numerical calculations; a design concept for the foundations will be developed on the basis of the results.

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