Optimal Design of Galvanic Corrosion Protection Systems for Offshore Wind Turbine Support Structures

CORROSION ◽  
10.5006/2688 ◽  
2018 ◽  
Vol 74 (7) ◽  
pp. 829-841
Author(s):  
Ali Sarhadi ◽  
Asger Bech Abrahamsen ◽  
Mathias Stolpe
Keyword(s):  
Cathodic Protection ◽  
Galvanic Corrosion ◽  
Cost Optimization ◽  
Optimization Procedure ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Fe Model ◽  
Dogger Bank ◽  
Protective Potential ◽  
Protection Systems

The current work addresses a mass/cost-optimization procedure for galvanic anode cathodic protection systems based on both cathodic protection (CP) standards and numerical simulation. An approach is developed for optimizing the number and dimensions of the galvanic anodes, distributing the optimized anodes on the support structure, and finally evaluating the protective potential on the structure during the lifetime by using finite element (FE) software. An algorithm based on sequential quadratic programming is used for optimizing the number and dimensions of the anodes. Both simplified and detailed models are suggested for calculating the protective potential on the structure. The simplified model is selected based on its advantages in terms of calculation time and compatibility with DNV standard data. A time-dependent FE model is used to take into account the electrical isolation degradation of the structure coating as well as the mass reduction of the anodes during the CP lifetime. The performance of the proposed optimization process is examined on a mono bucket inspired (with some simplifications) by the Dogger Bank metrological mast in England. The optimized designs for different coating and anode types are compared and the best designs in terms of both cost and protective potential during the lifetime are suggested. The achieved results show that the proposed optimization procedure can reduce the cost of the CP system around 70% compared to the original non-optimized CP design of the Dogger Bank metrological mast. Furthermore, evaluating the time-evolution performance of the CP systems can reduce their lifetime uncertainty.

scholarly journals Reliability analysis of offshore wind turbine foundations under lateral cyclic loading

2020 ◽  
Vol 5 (4) ◽  
pp. 1521-1535
Author(s):  
Gianluca Zorzi ◽  
Amol Mankar ◽  
Joey Velarde ◽  
John D. Sørensen ◽  
Patrick Arnold ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Wind Turbine ◽  
Limit State ◽  
Large Diameter ◽  
Probabilistic Approach ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Fe Model ◽  
Foundation Design

Abstract. The design of foundations for offshore wind turbines (OWTs) requires the assessment of long-term performance of the soil–structure interaction (SSI), which is subjected to many cyclic loadings. In terms of serviceability limit state (SLS), it has to be ensured that the load on the foundation does not exceed the operational tolerance prescribed by the wind turbine manufacturer throughout its lifetime. This work aims at developing a probabilistic approach along with a reliability framework with emphasis on verifying the SLS criterion in terms of maximum allowable rotation during an extreme cyclic loading event. This reliability framework allows the quantification of uncertainties in soil properties and the constitutive soil model for cyclic loadings and extreme environmental conditions and verifies that the foundation design meets a specific target reliability level. A 3D finite-element (FE) model is used to predict the long-term response of the SSI, accounting for the accumulation of permanent cyclic strain experienced by the soil. The proposed framework was employed for the design of a large-diameter monopile supporting a 10 MW offshore wind turbine.

scholarly journals Analysis of Tightening Sequence Effects on Preload Behaviour of Offshore Wind Turbine M72 Bolted Connections

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4406 ◽  
Author(s):  
Braithwaite ◽  
Mehmanparast
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Fe Model ◽  
Bolted Connections ◽  
Minimum Requirement ◽  
Offshore Wind Turbines ◽  
Sequence Effects ◽  
Transition Piece

Offshore wind turbines in shallow waters are predominantly installed using a monopile foundation, onto which a transition piece and wind turbine are attached. Previously, the monopile to transition piece (MP-TP) connection was made using a grouted connection, however, cases of grout failure causing turbine slippage, among other issues, were reported. One solution is to use bolted ring flange connections, which involve using a large number of M72 bolts to provide a firm fixing between the MP-TP. It is in the interest of offshore wind operators to reduce the number of maintenance visits to these wind turbines by maintaining a preload (Fp) level above the minimum requirement for bolted MP-TP connections. The present study focuses on the effect of the tightening sequence on the Fp behaviour of M72 bolted connections. A detailed finite element (FE) model of a seven-bolt, representative segment of a monopile flange was developed with material properties obtained from the available literature. Three analyses were made to examine the effect on Fp after tightening, including the initial Fp level applied to the bolts, the tightening sequence and the effect of an additional tightening pass.

Effect of Foundation Modelling Methodology on the Dynamic Response of Offshore Wind Turbine Support Structures

2011 ◽  
Author(s):  
Eric Van Buren
Keyword(s):  
Wind Turbine ◽  
Dynamic Properties ◽  
Dynamic Performance ◽  
Optimization Procedure ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Support Structures ◽  
Design Standards ◽  
Modelling Methodology

When preliminarily investigating offshore wind turbine tower concepts it is common to develop optimization software for determining the best possible structural layout. This type of optimization procedure requires a large number of iterations to determine the best possible design and can be quite time consuming, particularly if the dynamic performance of each structure is to be investigated using an aero-hydro-servo-elastic type solver. When performing this type of “dynamic optimization” it is convenient to simply assume fixed boundary conditions at the soil-structure interface and ignore the dynamic properties of the foundation. Using fixed conditions allows for each of the layouts to be compared quickly and makes the computer models simple to create and more efficient in computation than if the foundation is included. Alternatively, the foundations of offshore wind turbine support structures can be represented with several different methods of varying complexity and detail. The most widely used method is the use of a distributed spring model commonly known as the p-y method. This approach is the primary method in most offshore wind turbine design standards for determining the static and cyclic reaction of offshore piles. In this work, two offshore wind support structure layouts are modeled and analyzed in the wind turbine analysis program HAWC2. Dynamic time series analyses under operating conditions are carried out for each tower with fixed conditions and with foundation models based on the p-y method in order to determine the appropriateness of utilizing fixed foundation conditions for optimization procedures.

scholarly journals Structural Modeling and Failure Assessment of Spar-Type Substructure for 5 MW Floating Offshore Wind Turbine under Extreme Conditions in the East Sea

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6571
Author(s):  
Kwangtae Ha ◽  
Jun-Bae Kim ◽  
Youngjae Yu ◽  
Hyoung-Seock Seo
Keyword(s):  
Wind Energy ◽  
Wind Turbine ◽  
Three Dimensional ◽  
Offshore Wind ◽  
East Sea ◽  
Offshore Wind Turbine ◽  
Fe Model ◽  
Offshore Wind Energy ◽  
Floating Offshore Wind Turbine ◽  
Load Analysis

Not only the driving for offshore wind energy capacity of 12 GW by Korea’s Renewable Energy 2030 plan but also the need for the rejuvenation of existing world-class shipbuilders’ infrastructures is drawing much attention to offshore wind energy in Korea, especially to the diverse substructures. Considering the deep-sea environment in the East Sea, this paper presents detailed modeling and analysis of spar-type substructure for a 5 MW floating offshore wind turbine (FOWT). This process uses a fully coupled integrated load analysis, which was carried out using FAST, a widely used integrated load analysis software developed by NREL, coupled with an in-house hydrodynamic code (UOU code). The environmental design loads were calculated from data recorded over three years at the Ulsan Marine buoy point according to the ABS and DNVGL standards. The total 12 maximum cases from DLC 6.1 were selected to evaluate the structural integrity of the spar-type substructure under the three co-directional conditions (45°, 135°, and 315°) of wind and wave. A three-dimensional (3D) structural finite element (FE) model incorporating the wind turbine tower and floating structure bolted joint connection was constructed in FEGate (pre/post-structural analysis module based on MSC NASTRAN for ship and offshore structures). The FEM analysis applied the external loads such as the structural loads due to the inertial acceleration, buoyancy, and gravity, and the environmental loads due to the wind, wave, and current. The three-dimensional FE analysis results from the MSC Nastran software showed that the designed spar-type substructure had enough strength to endure the extreme limitation in the East Sea based on the von Mises criteria. The current process of this study would be applicable to the other substructures such as the submersible type.

scholarly journals Cost optimization of a symbiotic system to harvest uranium from seawater via an offshore wind turbine

2018 ◽  
Vol 169 ◽  
pp. 227-241 ◽  
Author(s):  
Margaret Flicker Byers ◽  
Maha N. Haji ◽  
Alexander H. Slocum ◽  
Erich Schneider
Keyword(s):  
Wind Turbine ◽  
Cost Optimization ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Symbiotic System ◽  
Uranium From Seawater

scholarly journals Reliability analysis of offshore wind turbine foundations under lateral cyclic loading

2019 ◽  
Author(s):  
Gianluca Zorzi ◽  
Amol Mankar ◽  
Joey Velarde ◽  
John D. Sørensen ◽  
Patrick Arnold ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Wind Turbine ◽  
Limit State ◽  
Large Diameter ◽  
Probabilistic Approach ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Fe Model ◽  
Foundation Design

Abstract. The design of foundations for offshore wind turbines (OWT) requires the assessment of the long-term performance of the soil–structure-interaction (SSI) which is subjected to a large number of cyclic loadings. In terms of serviceability limit state (SLS), it has to be ensured that the foundation does not exceed the operational tolerance prescribed by the wind turbine manufacturer throughout its lifetime. This work aims at developing a probabilistic approach along with a reliability framework with emphasis on verifying the SLS criteria in terms of maximum allowable rotation during an extreme cyclic loading event. This reliability framework allows the quantification of uncertainties in soil properties, in the constitutive soil model for cyclic loadings and extreme environmental conditions and verifies that the foundation design meets a specific target reliability level. A 3D finite element (FE) model is used to predict the long-term response of the SSI accounting for the accumulation of permanent cyclic strain experienced by the soil. The proposed framework is employed for the design of a large diameter monopile supporting a 10 MW offshore wind turbine.

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