Session: 09-02-07 Wind Energy: Fatigue Analysis

Submission Number: 177061

Impact of Wind-Wave Misalignment and Wave Directionality on Fatigue Damage of Floating Wind Turbines 

The ongoing climate change and the worldwide policies implemented to tackle it are driving a shift towards low-carbon electricity generation. Within this context, offshore wind energy plays a pivotal role. The marine environment offers higher capacity factors compared to inland installations and is enabling an unprecedented growth in turbine size, allowing significant cost reductions due to economies of scale. To extend the use of wind turbines in deep waters, floating systems have recently been proposed and tested in pre-commercial installations. However, the harsh marine environment pose significant structural challenges to floating systems, especially in terms of long-term reliability. An appropriate fatigue design is therefore crucial to ensure safety and to avoid costly emergency maintenance operations, which could undermine the economic viability of future offshore floating wind projects.

Although numerous studies on fatigue damage have been carried out, a high degree of uncertainty still persists in the representation of the wind and wave climate and its impact on the fatigue life of a floating wind turbine. One example concerns the lack of systematic studies addressing the effects of directional spreading of waves and wind–wave misalignment.

The focus of this work is to evaluate the influence of JONSWAP spectrum parameters, wave directionality and wind–wave misalignment on the fatigue damage at the interface between tower and transition piece for the IEA 15 MW reference turbine coupled with the VolturnUS semisubmersible platform.

Results show that the JONSWAP peak shape factor has potentially a minimal impact on fatigue damage, whereas the peak wave period appears to have a larger influence due to its correlation with the resonant nacelle fore-aft (and/or side-side) displacement(s) which is (are) responsible for a large part of the tower-base fatigue damage. Moreover, when considering wave directional spreading, preliminary results indicate that the fatigue damage associated to the mean wave direction decreases, while increasing across the full range of investigated directions. Finally, under wind–wave misalignment, fatigue damage seems mostly associated to wave-induced motions rather than to wind-induced motions. Results from this work are expected to benefit technology developers in the floating wind space.

Presenting Author: Gabriele Mangia Politecnico di Torino

Presenting Author Biography: Gabriele Mangia is a second-year PhD student in Mechanical Engineering at Politecnico di Torino, Italy. He completed both his Bachelor’s and Master’s degrees in Energy Engineering at the same university and is currently pursuing his PhD within the Marine Offshore Energy Lab. His research focuses on the fatigue behavior of floating wind turbines, with particular attention to the influence of environmental and climate load modelling.

Authors:

Gabriele Mangia Politecnico di Torino
Giuseppe Giorgi Politecnico di Torino
Giovanni Bracco Politecnico di Torino