Design of monopiles for offshore wind turbines in 10 steps

Arany, László; Bhattacharya, Subhamoy; Macdonald, John H G; Hogan, S. J.

doi:10.1016/j.soildyn.2016.09.024

Cited by 288 publications

(176 citation statements)

References 43 publications

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“…There is also uncertainty about the magnitude of responses. This affects not only the estimation of fatigue life but also the estimation of servicebility capacities which are defined in terms of deflections and rotations (tilt) at the pile head and nacelle level . The fatigue and serviceability requirements usually lead to conservative ultimate capacities .…”

Section: Introductionmentioning

confidence: 99%

Post‐installation adaptation of offshore wind turbine controls

et al. 2020

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The cost of offshore wind energy can be reduced by incorporating control strategies to reduce the support structures' load effects into the structural design process. While effective in reducing the cost of support structures, load‐reducing controls produce potentially costly side effects in other wind turbine components and subsystems. This paper proposes a methodology to mitigate these side effects at the wind farm level. The interaction between the foundation and the surrounding soil is a major source of uncertainty in estimating the safety margins of support structures. The safety margins are generally closely correlated with the modal properties (natural frequencies, damping ratios). This admits the possibility of using modal identification techniques to reassess the structural safety after installing and commissioning the wind farm. Since design standards require conservative design margins, the post‐installation safety assessment is likely to reveal better than expected structural safety performance. Thus, if load‐reducing controls have been adopted in the structural design process, it is likely permissible to reduce the use of these during actual operation. Here, the probabilistic outcome of such a two‐stage controls adaptation is analyzed. The analysis considers the structural design of a 10 MW monopile offshore wind turbine under uncertainty in the site‐specific soil conditions. Two control strategies are considered in separate analyses: (a) tower feedback control to increase the support structure's fatigue life and (b) peak shaving to increase the support structure's serviceability capacity. The results show that a post‐installation adaptation can reduce the farm‐level side‐effects of load‐reducing controls by up to an order of magnitude.

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Section: Introductionmentioning

confidence: 99%

Post‐installation adaptation of offshore wind turbine controls

et al. 2020

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“…However, it is still computationally demanding and requires special simulation software. Conceptual or parameter studies during the design process (Arany et al, 2017) or for research purpose (Cheng et al, 2012) usually necessitate to perform numerous simulations, thereby leading to a time-consuming task. These simulations are, therefore, often carried out with different analysis methods, such as frequency-domain calculations (van der Tempel and de Vries, 2005;Ziegler et al, 2015), substructuring techniques (van der Valk and Rixen, 2012), and/or simplified or reduced models .…”

Section: Introductionmentioning

confidence: 99%

Decoupled simulations of offshore wind turbines with reduced rotor loads and aerodynamic damping

Schafhirt

Muskulus

2018

Wind Energ. Sci.

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Abstract. Decoupled load simulations are a computationally efficient method to perform a dynamic analysis of an offshore wind turbine. Modelling the dynamic interactions between rotor and support structure, especially the damping caused by the rotating rotor, is of importance, since it influences the structural response significantly and has a major impact on estimating fatigue lifetime. Linear damping is usually used for this purpose, but experimentally and analytically derived formulas to calculate an aerodynamic damping ratio often show discrepancies to measurement and simulation data. In this study decoupled simulation methods with reduced and full rotor loads are compared to an integrated simulation. The accuracy of decoupled methods is evaluated and an optimization is performed to obtain aerodynamic damping ratios for different wind speeds that provide the best results with respect to variance and equivalent fatigue loads at distinct output locations. Results show that aerodynamic damping is not linear, but it is possible to match desired output using decoupled models. Moreover, damping ratios obtained from the empirical study suggest that aerodynamic damping increases for higher wind speeds.

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“…During a dynamic analysis, the natural frequency of the support structure must be within an allowable turbine operating range. Arany et al [3] proposed a simple procedure for the basic conceptual design of a monopile: they assessed foundation stiffness and determined the initial size of a monopile through calculation of pile deformation. However, scour is not considered in the design conditions.…”

Section: Introductionmentioning

confidence: 99%

“…The ultimate soil resistance p u can be determined by Equation (2) or (3), and the smaller of both values is to be considered: …”

Section: Introductionmentioning

confidence: 99%

An Investigation into the Effect of Scour on the Loading and Deformation Responses of Monopile Foundations

2017

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Severe foundation scour may occur around monopile foundations of offshore wind turbines due to currents and waves. The so-called p-y curves method is suggested in the existing design recommendations to determine the behavior of monopiles unprotected against scour and the reduction of effective soil stress is accounted for by the extreme scour depth. This conservative design approach does not consider the geometry of the scour hole and the effect of pile diameter on the soil resistance. An underestimated foundation stiffness would be obtained, thereby influencing the predicted overall response of the support structure of an offshore wind turbine. In this study, we calculated the load-deformation response and foundation stiffness of a monopile when scour occurred. The influence of pile diameter on the initial modulus of subgrade reaction, and the modification of the ultimate soil resistance of a monopile subject to scour are evaluated. The commercial software BLADED was used to simulate the dynamic response of the reference offshore wind turbine with monopile unprotected against scour at Chang-Bin offshore wind farm in Taiwan Strait. The results showed that when the p-y curve suggested by existing design regulation was used to calculate the load-deformation response, the foundation stiffness was underestimated where the scour depth was greater than the pile diameter, but the foundation stiffness was overestimated when the scour depth was less than the pile diameter.

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Design of monopiles for offshore wind turbines in 10 steps

Cited by 288 publications

References 43 publications

Post‐installation adaptation of offshore wind turbine controls

Post‐installation adaptation of offshore wind turbine controls

Decoupled simulations of offshore wind turbines with reduced rotor loads and aerodynamic damping

An Investigation into the Effect of Scour on the Loading and Deformation Responses of Monopile Foundations

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