Project areas and subprojects
B - Design principles
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B01 Integrated design process for offshore structures
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B02 Adaptive rotor concepts for on-demand feeding
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B03 Material-appropriate design of ultra-slim rotor blades
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B04 Load-bearing behavior of cyclically stressed foundations of megastructures
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B05 Efficient simulation and model reduction for offshore wind turbines
C - Regulation and structure monitoring
Z - central projects
Motivation
At the end of 2019, the European Commission presented its European Green Deal 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 to account for the largest share of electricity production in Europe, over 20%, by 2050.
During the past three decades, wind turbine (OWT) size growth has been almost unabated, as larger turbines are associated with a smaller footprint in addition to more efficient power generation and more continuous power feed-in. In terms of output, large turbines have shorter installation times, and logistics and grid connection are less expensive and time-consuming. In addition, 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.
Research area
Central research questions for offshore megastructures result from new and changing impact and utilization scenarios over the lifetime, for example as a result of new blade types and control concepts. Other causes of changing impacts over the lifetime are subsequent repowering or retrofitting measures as well as changing environmental impacts (increasingly extreme weather events and resulting, previously unconsidered impacts on support structures). A strong and so far insufficiently researched influence on the dynamic behavior of the structure is exerted by discontinuous degradation of the structure, changes in the soil, new control concepts (e.g., performance- or lifetime-optimized plant control), and adaptive components of the structure (e.g., (semi-) active damping systems). Compared to conventional structures, installation, operation and deconstruction concepts have a higher importance for megastructures and significantly influence the economic feasibility.
Scientific issues
- Future very large OWTs will be exposed to hitherto poorly known actions and combinations of actions. Examples are wind conditions in the Ekman layer and in the transition from the Prandtl to the Ekman layer, aeroelasticity on increasingly flexible very large rotor blades and hydrodynamic effects as well as scour effects on novel foundation structures.
- The rapidly growing support structures and system components exhibit extremely complex load-bearing and deformation behavior, which requires new holistic modeling approaches to describe them as an interacting system. For this purpose, on the one hand, nonlinear coupled overall models are indispensable, which, for example, can also precisely represent geometric nonlinearities, which become relevant in the case of the expected large deformations of ultra-slim rotor blades. On the other hand, these overall models should be capable of near real-time operation to enable predictive capability during operation as well as model-based control and structural monitoring, and to be able to test a large number of design variants in an economical time frame.
- The exposed location and the large dimensions and masses of structural and plant components lead to an increasing importance of coordinated installation, operation and maintenance concepts, which are ideally already considered in the design. This requires a mathematically describable methodology for an integrated design process that takes into account relevant life phases such as manufacturing, installation, operation and dismantling in the initial structural design in relevant detail.
- Due to the high planning and economic risk as well as the high investment and maintenance costs of offshore megastructures, special requirements are placed on the predictive capability of the models. Prognostic models for changing environmental conditions and control concepts as well as predictive maintenance concepts become existential for safe and economic operation. For this purpose, both physically motivated models for realistic description of changing design boundary conditions and a coupled overall model for virtual planning, testing and verification of new operational concepts and loading scenarios need to be explored.
- New structural concepts in offshore megastructures require the use of new materials. Furthermore, discontinuous degradation effects of the structure and, for certain materials (e.g., fiber composites), also continuous degradation effects play an increased role with respect to the dynamic behavior of OWTs, so that new material models may be required. As explained before, these shall deliberately not be addressed in the first funding period of the planned Collaborative Research Center, since corresponding new structural concepts shall only be a result of the first funding period. Thus, the focus will initially be on the development of design and operating methods.
