H2SEA, in collaboration with Delft University of Technology, has conducted a structural assessment of monopile-based support structures for offshore hydrogen Wind Turbine Generators (WTGs). The primary focus of the assessment was to determine the structural feasibility of decentralized hydrogen production on a monopile-based support structure of an offshore wind turbine.The research aimed to identify variances in support structure geometry and evaluate changes in the design methodology of an offshore wind turbine support structure, incorporating a decentralized hydrogen production platform. Looking towards future advancements, a 15 MW reference turbine was chosen for a water depth of 45 m in the F3 sector of the North Sea.
To determine platform mass, dimensions, and rotational inertia, all necessary systems were carefully selected, listed, and an optimised platform layout and mass estimation were developed. The design of the platform support beams considered gravitational loads and extreme wind gust loads. The selection of the support structure concept was made through a multi-criteria analysis.
For fatigue assessment, an analytical fully dynamical model was created in Maple. The structure was simulated using equations of motion, incorporating airy wave force, rotor damping, topside and platform mass and rotational inertia, embedded length, and homogeneous soil stiffness. The Maple model was utilised to simulate the dynamic behaviour of both structures, ascertain the first and second natural frequency, and illustrate displacements and overturning moments in these two mode shapes. Lastly, a fatigue damage calculation involving 500 combinations of wave height and period was carried out for a 25-year lifetime.
