Offshore wind energy for the European energy transition

The European Commission unveiled its European Green Deal at the end of 2019 to make Europe the first climate-neutral continent by 2050. The success of this ambitious goal depends on the expansion of offshore wind energy in the North Sea. The plan is for offshore wind energy to account for the largest share of electricity production in Europe, at over 20%, by 2050.

Over the past three decades, wind turbine (WTG) size growth has been nearly unabated, as larger turbines are associated with more efficient power generation and more continuous power feeds, as well as a smaller footprint. In terms of output, large-scale plants have shorter installation times and logistics and grid connection are less expensive and time-consuming. In addition, the maintenance of a few large plants is more efficient and economical than for a large number of smaller plants. These advantages make large-scale plants particularly valuable for the success of the energy transition and also for investors.

ForWind is involved in several projects and research initiatives focusing on offshore wind energy.

Collaborative Research Center 1463 “Integrated Design and Operational Methodology for Offshore Megastructures”.

For the operation of future wind farms, precise information on the condition and dynamic behavior of the support structure and rotor blades as well as knowledge of the effects of changing environmental and operating conditions is required for each individual turbine throughout its entire service life. Classical simulation models are usually identical for all turbines in a wind farm and focus mainly on load capacity. Aspects such as manufacturing, installation, and operation and dismantling, on the other hand, are given lower priority.

As part of the Collaborative Research Center, the researchers are therefore developing the digital twin, a method that integrates all these details. The digital twin is a coupled overall model of a concrete wind turbine, which is adapted to the current state of the real structure (the real twin) with the help of measurement data. This results in simulation models that describe individual, real plants over their entire service life and can always be adapted to the current state.

Four research institutions have joined forces under the leadership of Leibniz Universität Hannover (LUH) for SFB 1463 “Integrated Design and Operation Methodology for Offshore Megastructures”: In addition to LUH, the Carl von Ossietzky University of Oldenburg, the German Aerospace Center and the Technical University of Dresden are involved. At Leibniz University, a total of ten institutes from the Faculties of Civil Engineering and Geodesy, Mechanical Engineering, Mathematics and Physics, and Electrical Engineering and Computer Science are involved. A large number of the participating institutes at Leibniz Universität Hannover and Carl von Ossietzky Universität Oldenburg are already networked in the ForWind research association.

Subproject: Calculation models for the deployment planning of workboats

Offshore work operations (installation, maintenance, etc.) should be planned to maintain high standards of technician safety and minimize installation and maintenance costs. This requires accurate knowledge of weather conditions (wind speed and direction, wave height, period and direction) and the resulting movements of the working vessels.

Typically, these schedules are performed using linear transfer functions and simple limits on weather conditions. On the one hand, this results in very conservative deployment plans, and on the other hand, possible non-linear effects (e.g. frequency coupling of crane load and floating crane ship) in the motion response of the ships are neglected, the consideration of which could further increase the safety of the technicians during the deployment.

Within the framework of several research projects in SFB 1463, numerical and experimental studies are being conducted to investigate the operational limits of offshore workboats during the installation and maintenance of offshore wind turbines. Both floating crane vessels as a forward-looking installation method and crew transfer vessels (CTVs) will be investigated with regard to the technicians’ ability to work after the transfer from the port to the wind farm.

In another research project, the two-dimensional interpolation methods for the determination of weather data between different measurement sites (e.g. FINO platforms) will be developed, the results of which can in turn be used to optimize the deployment planning of the working vessels.

RAVE: Research at alpha ventus

The RAVE research initiative carries out research and development work at the alpha ventus offshore test field. Research and development at Germany’s first offshore wind farm generate experience and knowledge that drive the establishment and further development of offshore wind energy. RAVE is funded by the German Federal Ministry of Economics and Climate Protection (BMWK) and coordinated by the Fraunhofer Institute for Wind Energy Systems (IWES).

In a total of over 35 research projects, more than 60 partners from science and industry have worked on a wide range of research questions since 2008. The topics range from ecological issues to the further development of plants and foundations to the optimization of operations.