Impact of mooring lines dynamics on the fatigue and ultimate loads of three offshore floating wind turbines computed with IEC 61400-3 guideline

Abstract

The calculation of loads for floating offshore wind turbines requires time‐domain integrated simulation tools where most of the physical concepts involved in the system dynamics are considered. The loads at the different components are used for the structural calculation and influence the design noticeably. This study quantifies the influence of mooring dynamic models on the calculation of fatigue and ultimate loads with integrated tools and compares its performance with a lower computational cost quasi‐static mooring model. Three platforms representing the principal topologies (spar, semisubmersible and tension‐leg platform) were assumed to be installed at the same 200 m depth location in the Irish coast. For each platform, the fatigue and ultimate loads were computed with an integrated floating wind turbine simulation code using both, a quasi‐static and a fully dynamic moorings model. More than 3500 simulations for each platform and mooring model were launched and post‐processed according to the IEC 61400‐3 guideline in an exercise similar to what a certification entity may require to an offshore wind turbine designer. The results showed that the impact of mooring dynamics in both fatigue and ultimate loads increases as elements located closer to the platform are evaluated; the blade and the shaft loads are only slightly modified by the mooring dynamics in all the platform designs; the tower base loads can be significantly affected depending on the platform concept; and the mooring lines tensions strongly depend on the lines dynamics, both in fatigue and extreme loads for all the platform concepts evaluated. Copyright © 2016 John Wiley & Sons, Ltd.

Semi-submersible wind turbine hull shape design for a favorable system response behavior

“…For a representation of the overall FOWT response, the mooring line dynamics might be of negligible influence in the case of catenary mooring lines [16,17].…”

Multi-resolution wavelet pitch controller for spar-type floating offshore wind turbines including wave-current interactions

“…An instance of the Pierson-Moskowitz spectrum with and without an underlying current is shown in Figure 3. The parameters used are -significant wave height 10 m, peak spectral period 6 s and surface current velocity 0.609 m/s [87].…”

“…The offshore wind turbine is simulated without current and with an underlying current of uniform and linear profile. The surface current velocity is assumed to be 0.609 m/s [87] in the along wind direction, which is the same as the wave propagation direction. The above sea-states represent a violent ocean.…”

The TripleSpar Campaign: Validation of a Reduced-Order Simulation Model for Floating Wind Turbines

“…Within the project INNWIND.EU a platform design competition among the project partners resulted in three different concepts, described in [13]. For the one, whose design began at the University of Stuttgart, a detailed design was done by CE-NER and the National Technical University of Athens (NTUA) towards the end of the project, see [14]. The mooring system design was a joint work by the University of Stuttgart and DTU.…”