Wind power
Repowering for offshore wind turbines

Wind turbines at sea are usually designed for a lifetime of 20 to 25 years. Before continuing operation, it is checked whether this is technically and economically feasible. Scientists now want to expand offshore repowering.

Offshore wind turbines must either be dismantled after around 20 years or they have to be made fit for safe continued operation. Wind turbines can only be operated for longer if the most intensively used components are checked and replaced in case of defects or weaknesses. This is particularly difficult or even impossible for components that are under water. The Fraunhofer Institute for Wind Energy Systems IWES has now highlighted a third alternative for offshore wind farms: repowering that uses the existing foundations. In repowering, operators replace old turbines with new, more powerful ones. As the locations are already known, a lot of time-consuming exploration work can be dispensed with. In addition, the grid connection is already in place. Repowering already plays an important role in the expansion strategy in onshore wind power. For offshore wind farms, there is as yet no comprehensive solution that covers all components, including those located under water.

Reinforcing and reusing existing foundations for new plants

In the InGrow research project, the project team has now developed a concept that upgrades and reuses existing foundations. The scientists are using the existing monopile foundation - a pile driven deep into the seabed that supports the wind turbine - for this purpose. Monopiles are the most commonly used support structures for offshore wind turbines today, with a market share of around 80 per cent. If they can continue to be used for repowering, this saves considerable costs.

Innovative foundation system applied for as international patent

The project team has now combined monopiles and multi-buckets. This enabled the scientists to design a foundation structure that, on the one hand, allows the lifetime of the monopiles to be extended and, on the other hand, is so robust that new, more powerful wind turbines can be placed on top of an existing foundation. Fraunhofer IWES has registered this innovative start-up system as an international patent.(se)