Key Contributors to Lifetime Accumulated Fatigue Damage in an Offshore Wind Turbine Support Structure

Smilden, Emil; Bachynski, Erin Elizabeth; Sørensen, Asgeir J.

doi:10.1115/omae2017-61708

Cited by 6 publications

(9 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This section presents the results of load calculations in operational conditions across the design space. First, selected signal statistics will be compared, weighted with the probability of occurrence of each environmental condition over a lifetime of 20 years in the same way as [58]. Thereafter, the frequency-domain response will be analyzed and the results will be verified through a comparison against the reference model FAST.…”

Section: Load Calculationmentioning

confidence: 99%

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

Lemmer

Müller

et al. 2020

Marine Structures

View full text Add to dashboard Cite

Floating offshore wind turbines are a novel technology, which has reached, with the first wind farm in operation, an advanced state of development. The question of how floating wind systems can be optimized to operate smoothly in harsh wind and wave conditions is the subject of the present work. An integrated optimization was conducted, where the hull shape of a semi-submersible, as well as the wind turbine controller were varied with the goal of finding a cost-efficient design, which does not respond to wind and wave excitations, resulting in small structural fatigue and extreme loads.The optimum design was found to have a remarkably low tower-base fatigue load response and small rotor fore-aft amplitudes. Further investigations showed that the reason for the good dynamic behavior is a particularly favorable response to first-order wave loads: The floating wind turbine rotates in pitchdirection about a point close to the rotor hub and the rotor fore-aft motion is almost unaffected by the wave excitation. As a result, the power production and the blade loads are not influenced by the waves. A comparable effect was so far known for Tension Leg Platforms but not for semi-submersible wind turbines. The methodology builds on a low-order simulation model, coupled to a parametric panel code model, a detailed viscous drag model and an individually tuned blade pitch controller. The results are confirmed by the higher-fidelity model FAST. A new indicator to express the optimal behavior through a single design criterion has been developed.

show abstract

Section: Load Calculationmentioning

confidence: 99%

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

Lemmer

Müller

et al. 2020

Marine Structures

View full text Add to dashboard Cite

show abstract

“…Details regarding the hindcast, which covers the North Sea, the Norwegian Sea, and the Barents Sea, are found in [33]. Furthermore, a detailed statistical description of the metocean data for the design location is given in [17], and some important features with regard to assessment of the lifetime fatigue strength are presented in [6]. The metocean data contains information about significant wave height H s , peak period T p , wave direction, mean wind speed V, and wind direction.…”

Section: Environmental Conditionsmentioning

confidence: 99%

“…. , 180 • [6]. Following [3], the number of bins are halved by merging the sectors mirrored about the vertical axis.…”

Section: Environmental Conditionsmentioning

confidence: 99%

“…The magnitude of the hydrodynamic loads increases due to the larger diameter of the monopile. Furthermore, the increased mass of the rotor-nacelle assembly (RNA) and height of the wind turbine, together with a reduction of the rotor speed and the corresponding frequency constraint imposed by the blade passing frequency (3P), pushes the first modal frequencies of the support structure closer to typical wave frequencies [6,7].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Site-specific controller design for monopile offshore wind turbines

et al. 2018

Self Cite

View full text Add to dashboard Cite

The fatigue life of offshore wind turbine (OWT) support structures is sensitive to variations in site-specific conditions such as the water depth and soil properties. Site condtions may vary significantly within a wind farm, and they may change throughout the lifetime of the OWT. This paper analyses how control strategies for fatigue life extension can compensate for differing fatigue loads due to varying site conditions. Control strategies applicable for both power production and idling situations are analysed, and methodology to reduce undesirable side-effects is proposed. The design case is a 10MW monopile OWT located in 30 meter water depth at the Dogger Bank in the North Sea, and results are based on time-domain simulations performed using an aero-hydro-servo-elastic simulation tool. The results show that, when all the investigated control strategies are utilized, a fatigue damage reduction over the 20-year lifetime of approximately 50% is possible. Furthermore, it is shown that adverse side-effects such as wear of pitch actuators and fluctuations in the power output can be significantly reduced by limiting the use of control strategies to some predefined situations. With only moderate cost to other system components, the control system is able to compensate for 20% variation in soil stiffness, and 5% (1.5 meter) variation in water depth.

show abstract

“…Monopile dimensions are mainly governed by fatigue considerations. With the introduction of even larger offshore wind turbines (OWTs), the first‐order wave loads become dominating in terms of fatigue utilization . Besides increased wave loads due to larger dimensions, the modal frequencies of the OWTs are shifted closer to typical wave frequencies, thereby increasing the dynamic amplification of the wave‐induced response …”

Section: Introductionmentioning

confidence: 99%

Wave disturbance rejection for monopile offshore wind turbines

et al. 2018

Self Cite

View full text Add to dashboard Cite

The dimensions of offshore wind turbine (OWT) support structures are governed by fatigue considerations. For 6‐ to 10‐MW OWTs, wave loads are often dominating in terms of fatigue utilization. The present work proposes a control scheme to reduce the wave‐induced fatigue loads in OWT support structures. The control scheme applies collective pitch control to increase both the damping and stiffness of the fore‐aft vibration modes. With conventional active tower damping, efficient wave disturbance rejection is restricted to a narrow frequency range around the first fore‐aft modal frequency. The proposed control scheme achieves efficient wave disturbance rejection across a broader frequency range. Here, tower feedback control is implemented via an auxiliary control loop. Based on a low‐fidelity model, the effect of the tower feedback loop on the stability margins of the basic controller is analysed. The results show that, within certain boundaries, the stability margins are improved by the stiffness term in the tower feedback loop. Consequently, the need to reduce the bandwidth of the basic controller to accommodate tower feedback control is relaxed. Based on time‐domain simulations carried out in an aero‐hydro‐servo‐elastic simulation tool, the lifetime effects of the proposed control scheme are analysed. Compared with conventional active tower damping, a more favourable trade‐off between adverse side effects and the support structure's fatigue damage is achieved with the proposed control scheme.

show abstract

Key Contributors to Lifetime Accumulated Fatigue Damage in an Offshore Wind Turbine Support Structure

Cited by 6 publications

References 0 publications

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

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

Site-specific controller design for monopile offshore wind turbines

Wave disturbance rejection for monopile offshore wind turbines

Contact Info

Product

Resources

About