Development of a comprehensive database of scattering environmental conditions and simulation constraints for offshore wind turbines

Abstract

Abstract.For the design and optimisation of offshore wind turbines, the knowledge of realistic environmental conditions and utilisation of well-founded simulation constraints is very important, as both influence the structural behaviour and power output in numerical simulations. However, real high-quality data, especially for research purposes, are scarcely available. This is why, in this work, a comprehensive database of 13 environmental conditions at wind turbine locations in the North and Baltic Sea is derived using data of the FINO research platforms. For simulation constraints, like the simulation length and the time of initial simulation transients, wellfounded recommendations in the literature are also rare. Nevertheless, it is known that the choice of simulation lengths and times of initial transients fundamentally affects the quality and computing time of simulations. For this reason, studies of convergence for both parameters are conducted to determine adequate values depending on the type of substructure, the wind speed, and the considered loading (fatigue or ultimate). As the main purpose of both the database and the simulation constraints is to compromise realistic data for probabilistic design approaches and to serve as a guidance for further studies in order to enable more realistic and accurate simulations, all results are freely available and easy to apply.

Methodologies for fatigue assessment of offshore wind turbines considering scattering environmental conditions and the uncertainty due to finite sampling

“…As these states significantly affect the fatigue damage of offshore wind energy plants, precise data of the specific turbine location are valuable. However, real site data are scarce, which is the reason for the formerly mentioned approaches of reference data bases . Although these data bases define conditional, statistical distributions for some environmental conditions, others are considered to be constant in each wind speed bin or even in all of them.…”

“…In this study, an adopted version of the data basis of Hübler et al is used. For 13 environmental parameters and 3 sites, conditional distributions, derived from offshore measurement data from FINO platforms, are available.…”

“…In this work, the focus is on the 7 conditions in Table that were measured at the FINO3 site, which is located 80 km west of the island Sylt near to the wind farm DanTysk and measures since 2009. For further details concerning the platform and the data, it is referred to the original source …”

“…According to Hübler et al, distributions for all 7 environmental conditions are fitted to the data. The best fitting distributions—evaluated with Kolmogorov‐Smirnov and χ 2 tests—are chosen, while keeping distributions as simple as possible (eg, multimodal distributions are only used, if the distribution of the raw data clearly exhibits several peaks).…”

“…This is why several research projects characterized environmental conditions at specific sites or entire areas and published statistical distributions as a reference. Examples for data bases of main conditions (wind speeds, wave height, wave period, and wind and wave directions) are the UPWIND design basis, the work of Stewart et al, the PSA‐OWT project, Häfele et al, or Hübler et al In this work, the data basis of Hübler et al is utilized, as it is—beside other advantages—the only one where additional environmental conditions, like the turbulence intensity or the wind shear, are considered in a statistical manner (see Table 2 for considered environmental conditions).…”