Fraunhofer Institute for Wind Energy SystemsAt a glance
- Floating offshore wind turbines offer great potential for the energy transition, but the foundation structures currently in use, made of steel and concrete, have disadvantages.
- The PREPARE project MoGeSa is therefore developing a mass-production-ready and economically viable manufacturing technology for the use of fiber-reinforced plastics, the fundamental feasibility of which will be demonstrated on a prototype.
- In this project, Fraunhofer IWES is responsible, among other things, for defining requirements and specifications for the floating structures, as well as for the design, load simulation, and optimization of the floater and testing of the demonstrator.
The challenge
Floating offshore wind turbines (FOWTs) are needed to ensure a climate-friendly energy supply: 60 to 80 percent of the world’s oceans are unsuitable for bottom-fixed wind turbines due to water depth. According to expert estimates, more than 250 gigawatts of capacity from floating wind farms will be needed worldwide by 2050 to securea climate-friendly energy supply.
Current designs for floating structures rely on steel or concrete. However, both materials show disadvantages for this application: Because steel is susceptible to corrosion, it must be coated before being used at sea. Concrete limits design flexibility and may be prone to fatigue, particularly under dynamic loads. In addition, the saltwater resistance of reinforced concrete structures poses a problem. Without special precautions, salt penetrates the concrete structure and attacks the tensile-load-bearing steel reinforcement.
The solution
Fiber-reinforced composites (FRC) offer significant advantages such as corrosion resistance, low weight, durability, and low maintenance costs. In the PREPARE project MoGeSa, the three participating Fraunhofer Institutes are developing a novel manufacturing technology - the MoGeSa technology - to produce FRP components that are optimally adapted to offshore conditions and the technical requirements of wind turbines.
Fraunhofer IGCV is developing a new inline foam pultrusion process for the continuous production of large-area FRP sandwich panels with an integrated foam core. Fraunhofer IFAM is developing corresponding adhesive joining processes that allow many such panels to be securely and permanently joined - and, if necessary, separated again (“debonding on demand”) - to form large modular structures. Accompanying life cycle assessments and cost analyses will demonstrate how the new technology compares to steel and concrete designs and where further savings potential lies.
Fraunhofer IWES first creates a set of specifications to document typical wind, wave, and environmental conditions for floating wind turbines. The floater geometry is optimized using the institute’s own simulation tools, MoWiT and PyWiT: shape, dimensions, and material composition are selected to ensure the structure is buoyantly stable and loads are minimized. Based on this, Fraunhofer IWES then calculates the loads and service life of the FRP structure. Subsequently, a scaled floating demonstrator is designed, constructed from the new FRP sandwich panels, and tested under realistic loads at the Test Center for Support Structures in Hannover. The measurement data obtained is used to verify and refine the calculation models.
The added value
The manufacturing process developed in the PREPARE project MoGeSa enables the use of FRP in floating wind turbines. This lowers manufacturing costs, reduces the ecological footprint, and minimizes maintenance requirements. The end result is a significant increase in the efficiency, durability, and sustainability of floating wind turbines and, consequently, offshore wind energy.
However, the technology is not limited to use in wind turbines but can be applied wherever lightweight, stable, cost-effective, and environmentally friendly large-scale structures are required: including in the infrastructure, construction, boatbuilding, and recreational vehicle sectors.
