DNV GL Standard for Floating Wind Turbines

2018 ◽  
Author(s):  
Anne Lene Haukanes Hopstad ◽  
Kimon Argyriadis ◽  
Andreas Manjock ◽  
Jarett Goldsmith ◽  
Knut O. Ronold
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Technical Specification ◽  
Oil And Gas Industry ◽  
Offshore Wind ◽  
Floating Structures ◽  
Service Specification ◽  
Technical Requirements ◽  
Floating Wind Turbine ◽  
Damage Stability

The first issue of the DNV Offshore Standard, DNV-OS-J103 Design of Floating Wind Turbine Structures, was published in June 2013. The standard was based on a joint industry effort with representatives from manufacturers, developers, utility companies and certifying bodies from Europe, Asia and the US. The standard represented a condensation of all relevant requirements for floaters in existing DNV standards for the offshore oil and gas industry which were considered relevant also for offshore floating structures for support of wind turbines, supplemented by necessary adaptation to the wind turbine application. The development of the standard capitalized much on experience from development projects going on at the time, in particular the Hywind spar off the coast of western Norway, the WindFloat off the coast of Portugal and the Pelastar TLP concept. In July 2018, DNV GL published a revision of DNV-OS-J103 as a part of the harmonization of the DNV GL codes for the wind turbine industry after the merger between Det Norske Veritas (DNV) and Germanischer Lloyd (GL) in the fall of 2013. The standard was re-issued as DNVGL-ST-0119 Floating wind turbine structures. This new revision reflects the experience gained after the first issue in 2013 as well as the current trends within the industry. Since 2013, numerous guidelines addressing the design of floating structures for offshore wind turbines have been published by various certifying bodies, and an IEC technical specification on the subject is under way. In addition, several prototypes have been installed and the first small array of floating wind turbines, Hywind Scotland pilot park, are currently in operation. The most important updates in the revision of the standard include formulation of floater-specific load cases, requirements to be fulfilled to support the exemption for design of unmanned floaters with damage stability, and replacement of current consequence-class based requirements for design fatigue factors with low-consequence based factors dependent on the accessibility for inspection and repair, the aim being a safety level against fatigue similar to that which is currently targeted for bottom-fixed structures. Other topics which have been considered in the revision are the floater motion control system and its possible integration with the control and protection system for the wind turbine, the issue of how to deal with slack in tendons in the station keeping system, corrosion, anchor design and power cable design. In parallel to the revision of the standard, a new service specification for certification of floating wind turbines has been developed by DNV GL, identified as DNVGL-SE-0422 Certification of floating wind turbines. For technical requirements, the service specification refers to the revised standard, DNVGL-ST-0119. The technical paper summarizes the updates and changes in the revised standard, in addition to the content of the new service specification.

Guideline for Offshore Floating Wind Turbine Structures

2010 ◽  
Author(s):  
Knut O. Ronold ◽  
Vigleik L. Hansen ◽  
Marte Godvik ◽  
Einar Landet ◽  
Erik R. Jo̸rgensen ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farms ◽  
Oil And Gas Industry ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Technical Requirements ◽  
Floating Wind Turbine ◽  
Floating Offshore Wind Turbines ◽  
Offshore Floating Wind Turbine

Floating offshore wind turbines is a field undergoing major development. Several companies and research institutes worldwide are engaged in research programs, pilot projects and even planning of commercial floating wind farms. Developing standards for design of floating wind turbine structures and a framework for prevailing rules are crucial and necessary for the industry to continue to grow. Det Norske Veritas (DNV) is an international provider of offshore standards for both the oil and gas industry and the wind energy industry. The standard DNV-OS-J101 “Design of Offshore Wind Turbine Structures” provides principles, technical requirements and guidance for design, construction and in-service inspection of offshore wind turbine structures. As a first step towards updating this standard to fully cover floating wind turbine structures, a DNV Guideline for Offshore Floating Wind Turbines has been established. This development is based on identification of current floating wind turbine concepts and the guideline includes an evaluation of what is required to make DNV-OS-J101 suitable for floating wind turbine structures. This paper presents the highlights of the new DNV Guideline for Offshore Floating Wind Turbine Structures.

Model Experiments on the Motion of a SPAR Type Floating Wind Turbine in Wind and Waves

2011 ◽  
Author(s):  
Toshiki Chujo ◽  
Shigesuke Ishida ◽  
Yoshimasa Minami ◽  
Tadashi Nimura ◽  
Shunji Inoue
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Offshore Wind ◽  
Floating Structure ◽  
Floating Structures ◽  
Water Basin ◽  
Offshore Wind Turbines ◽  
Floating Wind Turbine ◽  
Floating Offshore Wind Turbines

The study of floating offshore wind turbines has recently been attractive to many research groups in the renewable energy. Because the area of shallow water along Japanese coast is limited, the development of floating base for wind turbine is inevitable for making large scale wind farms. There are some problems to be solved for floating offshore wind turbines. Besides the mechanical problems of turbines, the influence of the motion of the floater in wind and waves to the electric generation properties, the safeties of floating structures such as the fatigue of machines and structures or criteria of electric facilities should be studied. Several types of floating structures have been proposed such as SPAR, TLP, pontoon, and semi submersibles. The authors have focused on SPAR type because its simpler shape seems to have economical advantages. In this paper, the authors performed experiments in a wind tunnel and a water basin from the viewpoint of “wind turbines on a SPAR type floating structure”. Firstly, forced pitching experiments were operated in a wind tunnel, and the difference in two types of wind turbines, upwind type and downwind type, is discussed. The former type is very popular and the latter type is thought to be suitable for floating structure. Secondly, experiments which thought to be more relevant for a floating wind turbine were carried out in a water basin. The relationship between the location of the attachment point of mooring lines and the motion of the SPAR in waves, and the influence of pitching angle of turbine blades to the motion of the SPAR in waves were inspected. In these experiments it was used a mechanism to control the pitch angle of the blades of the scale model of wind turbine.

Comparison of Spar and Semisubmersible Floater Concepts of Offshore Wind Turbines Using Long-Term Analysis

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Hasan Bagbanci ◽  
D. Karmakar ◽  
C. Guedes Soares
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Transfer Functions ◽  
Probability Distributions ◽  
Offshore Wind ◽  
Short Term ◽  
Offshore Wind Turbines ◽  
Floating Wind Turbine ◽  
Offshore Floating Wind Turbine

The long-term probability distributions of a spar-type and a semisubmersible-type offshore floating wind turbine response are calculated for surge, heave, and pitch motions along with the side-to-side, fore–aft, and yaw tower base bending moments. The transfer functions for surge, heave, and pitch motions for both spar-type and semisubmersible-type floaters are obtained using the fast code and the results are also compared with the results obtained in an experimental study. The long-term predictions of the most probable maximum values of motion amplitudes are used for design purposes, so as to guarantee the safety of the floating wind turbines against overturning in high waves and wind speed. The long-term distribution is carried out using North Atlantic wave data and the short-term floating wind turbine responses are represented using Rayleigh distributions. The transfer functions are used in the procedure to calculate the variances of the short-term responses. The results obtained for both spar-type and semisubmersible-type offshore floating wind turbine are compared, and the study will be helpful in the assessments of the long-term availability and economic performance of the spar-type and semisubmersible-type offshore floating wind turbine.

Investigations of Unsteady Aerodynamics of an Offshore Floating Wind Turbine With Platform Motions Using Dual-Sliding Method

2020 ◽  
Author(s):  
Xiaodong Wang ◽  
Zhaoliang Ye ◽  
Ziwen Chen ◽  
Yize Guo ◽  
Yujun Qiao
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Aerodynamic Performance ◽  
Offshore Wind ◽  
Sliding Mesh ◽  
Unsteady Aerodynamic ◽  
Floating Wind Turbine ◽  
Mesh Method ◽  
Offshore Floating Wind Turbine ◽  
Platform Motions

Abstract Offshore wind energy developed rapidly in recent years. Due to the platform motions causing by ocean waves, the aerodynamics of floating offshore wind turbines (FOWT) show strong unsteady characters than onshore wind turbines. The widely used methods to investigate the unsteady aerodynamic performance of wind turbine are Blade Element Momentum (BEM) and Free-Vortex Wake (FVW) methods. The accuracy of these two methods strongly depend on empirical formula or correction models. However, for dynamics motions of wind turbine, there is still a lack of accurate models. CFD simulations using overset or dynamic mesh methods also have been used for FOWT aerodynamic investigations. However, the mesh deforming or reconstruction methods are usually suitable for small movement of wind turbine blade. In this paper, a dual-sliding mesh method is employed to simulate the unsteady aerodynamic characters of an offshore floating wind turbine with supporting platform motions using Unsteady Reynolds Averaged Navier-Stokes (URANS) simulations. Both rotor rotation and platform motions are treated as rigid angular motions. The relative motion and data exchange were simulated using sliding mesh method. The NREL 5MW reference wind turbine with platform pitching and rolling motions are considered. The pitching and rolling motions of floating platform are simplified in the form of a prescribed sinusoidal function. Different conditions with two amplitudes and two frequencies of pitching and rolling motions were investigated. URANS were performed with full structured mesh for wind turbine rotor using commercial software FLUENT. The platform motions were set using User Defined Function (UDF). Transitional Shear Stress Turbulence (T-SST) model was employed. The simulation results were compared with BEM method and FVW method results. Both steady status and dynamic pitching processes are investigated. The variations of wind turbine aerodynamic load, as well as the aerodynamic character of airfoils at different spanwise positions, were obtained and analyzed in detail. The simulations results show that the platform pitching introduce remarkable influence on the wind turbine aerodynamic performance. The platform pitching has much larger influence on the wind turbine power and thrust than the platform rolling. The dual-sliding mesh method shows potentials to investigation the dynamic process with multiple rigid motions.

Vibration and Load Suppression of Offshore Floating Wind Turbine

2014 ◽  
Vol 1025-1026 ◽  
pp. 891-896 ◽  
Author(s):  
Er Ming He ◽  
Ya Qi Hu ◽  
Yang Zhang ◽  
Ge Liang Yin
Keyword(s):  
Wind Turbine ◽  
Structural Dynamics ◽  
Wind Turbines ◽  
Structural Control ◽  
Offshore Wind ◽  
Dynamics Simulation ◽  
Type Model ◽  
Simulation Code ◽  
Offshore Wind Turbines ◽  
Floating Wind Turbine

The application of tuned mass dampers (TMDs) to offshore wind turbines has a huge potential to suppress the large vibration responses of these systems. Control module of TMDs is added into the wind turbine structural dynamics simulation code FAST and fully coupled aero-hydro-TMD-structural dynamics model of the 5MW Barge-type floating wind turbine by National Renewable Energy Laboratory (NREL) is established. A multi-parameter optimization study is performed to determine the optimal parameters of a fore-aft TMD system in the Barge-type model. The wind turbine model equipped with the optimal TMD is then simulated under five typical load conditions and the performance of the new system is evaluated. The results show that longitudinal loads at tower base and deflections at tower top reductions of up to 50% and longitudinal loads at blade root and deflections at blade tip reductions of up to 40% are achieved, which indicates that the optimal TMD can be used to suppress the vibration response of offshore wind turbines and also demonstrates the potential for TMD structural control approaches.

Coupling of Two Tools for the Simulation of Floating Wind Turbines

2013 ◽  
Author(s):  
Sébastien Gueydon ◽  
Koert Lindenburg ◽  
Feike Savenije
Keyword(s):  
Computer Program ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Time Domain ◽  
Domain Model ◽  
Offshore Wind ◽  
Floating Body ◽  
Research Centre ◽  
Floating Wind Turbine ◽  
Floating Offshore Wind Turbines

For the design of a floating wind turbine it is necessary to take the loading due to the wind, wave and current in equal consideration. The PHATAS computer program from ECN (Energy research Centre of the Netherlands) is a time-domain aero-elastic simulation program, that accounts for the complete mutual interaction of unsteady rotor aerodynamics, structural dynamics of the rotor blades and tower, and interaction with the turbine controller under influence of turbulent wind and wave loading for fixed wind turbines. The aNySIM computer program from MARIN is a multi rigid body time domain model that accounts for wave loadings, current loadings, wind loadings, floating body dynamics, mooring dynamics. The coupled computer program aNySIM / PHATAS accounts for all loadings acting on a floating wind turbine and its response whereas PHATAS can only be used for fixed wind turbines onshore and offshore. This paper reports on the dynamic coupling between PHATAS and aNySIM. As a typical case study, the controller for floating offshore wind turbines is evaluated. This new tool has been used to repeat phase IV of the Offshore Code Comparison Collaboration (OC3) within IEA Wind Task 23, regarding floating wind turbine modelling. The results of these simulations are presented in this paper.

Revision of DNV GL Design Standard for Floating Wind Turbine Structures

2017 ◽  
Author(s):  
Anne Lene Haukanes Hopstad ◽  
Knut O. Ronold ◽  
Kimon Argyriadis
Keyword(s):  
Wind Turbine ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Gas Industry ◽  
Floating Structures ◽  
Current Trends ◽  
Floating Wind Turbine ◽  
Standard Design ◽  
Offshore Oil And Gas ◽  
Offshore Oil

The first edition of the DNV Offshore Standard “Design of Floating Wind Turbine Structures”, DNV-OS-J103, was published in June 2013. The standard represented a condensation of all relevant requirements for floaters in existing DNV standards for the offshore oil and gas industry which were considered relevant also for offshore floating structures for support of wind turbines, supplemented by necessary adaptation to the wind turbine application. As part of the harmonization of the DNV GL codes for the wind turbine industry after the merger between Det Norske Veritas (DNV) and Germanischer Lloyd (GL) in the autumn of 2013, DNV GL currently plans to publish a revision of DNV-OS-J103 in 2017, to become identified as DNVGL-ST-0119. The new revision is intended to reflect the experience gained since 2013 as well as the current trends within the industry.

Model-Inversion Feedforward Control for Wave Load Reduction in Floating Wind Turbines

2021 ◽  
Author(s):  
Alessandro Fontanella ◽  
Marco Belloli
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Control Strategy ◽  
Feedforward Control ◽  
Operating Conditions ◽  
Offshore Wind ◽  
Linear Wave ◽  
Wave Load ◽  
Floating Wind Turbine ◽  
Floating Offshore Wind Turbines

Abstract This paper develops a novel feedforward control strategy for reducing structural loads caused by waves in floating offshore wind turbines. The proposed control strategy is based on the inversion of a linear model of the floating wind turbine, and a real-time forecast of the wave obtained from an upstream measurement is utilized to compute a collective pitch control action. Two feedforward controllers are considered: one is designed to cancel the rotor speed oscillations and one to lower the towertop fore-aft shear force. The feedforward control strategies are implemented in a 10MW floating wind turbine, complementing the standard feedback controller for generator speed regulation. Numerical simulations are carried out in FAST, in four operating conditions with realistic wind and waves, proving the proposed feedforward controller effectively mitigates the structural loads caused by waves. In detail, the feedforward action reduces the loads spectra in the frequency range where linear wave is active. The best performance is realized higher winds (the FA force is reduced up to 25% in 22 m/s wind), where the wave excitation is the strongest.

Fully Coupled Aero-Hydro-Structural Simulation of New Floating Wind Turbine Concept

2018 ◽  
Author(s):  
Aengus Connolly ◽  
Marc Guyot ◽  
Marc Le Boulluec ◽  
Léna Héry ◽  
Aonghus O’Connor
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Structural Model ◽  
Capital Expenditure ◽  
Offshore Wind ◽  
Floating Platform ◽  
Simulation Methodology ◽  
Floating Wind Turbine ◽  
Floating Offshore Wind Turbines ◽  
Fully Coupled

This paper describes a fully coupled numerical simulation methodology which is tailored towards floating offshore wind turbines. The technique assembles three key components; an aerodynamic model of the applied wind loads based on blade element momentum theory, a structural model of the floating platform and its associated mooring lines based on the nonlinear finite element method, and a hydrodynamic model of the wave-induced forces based on potential flow theory. The simulation methodology has been implemented in a commercial software product called ‘Flexcom Wind’, and the technical validation involves comparisons with experimental data derived from model-scale tank test facilities. The validation process centres on an innovative floating wind turbine concept developed by Eolink. Unlike most wind turbines in industry which are supported by a single mast, this patented design uses four separate pillars to connect the turbine structure to the corners of the floating platform. This unique configuration offers several advantages over conventional designs, including a more even stress distribution in structural members, reduced dynamic vibration, smaller floater size and lower overall capital expenditure. Data obtained from the numerical simulations combined with the empirical tests is helping to optimise the device, with a view to further improving its structural design and performance.

Fatigue Damage to the Spar-Type Offshore Floating Wind Turbine Under Blade Pitch Controller Faults

2014 ◽  
Author(s):  
Mahmoud Etemaddar ◽  
Elaheh Vahidian ◽  
Otto Skjåstad
Keyword(s):  
Wind Turbine ◽  
Fatigue Damage ◽  
Wind Turbines ◽  
Pitch Angle ◽  
Offshore Wind ◽  
Offshore Wind Turbines ◽  
Composite Blade ◽  
Floating Wind Turbine ◽  
Offshore Floating Wind Turbine ◽  
Blade Pitch Angle

The safety and reliability margin of offshore floating wind turbines need to be higher than that of onshore wind turbines due to larger environmental loads and higher operational and maintenance costs for offshore wind turbines compared to onshore wind turbines. However rotor cyclic loads coupled with 6 DOFs motions of the substructure, amplifies the fatigue damage in offshore floating wind turbines. In general a lower fatigue design factor is used for offshore wind turbines compared to that of the stationary oil and gas platforms. This is because the consequence of a failure in offshore wind turbines in general is lower than that of the offshore oil and gas platforms. In offshore floating wind turbines a sub-system fault in the electrical system and blade pitch angle controller also induces additional fatigue loading on the wind turbine structure. In this paper effect of selected controller system faults on the fatigue damage of an offshore floating wind turbine is investigated, in a case which fault is not detected by a fault detection system due to a failure in the fault detection system or operator decided to continue operation under fault condition. Two fault cases in the blade pitch angle controller of the NREL 5MW offshore floating wind turbine are modeled and simulated. These faults include: bias error in the blade pitch angle rotary encoder and valve blockage or line disconnection in the blade pitch angle actuator. The short-term fatigue damage due to these faults on the composite blade root, steel low-speed shaft, tower bottom and hub are calculated and compared with the fatigue damage under normal operational conditions considering same environmental conditions for both cases. This comparison shows that how risky is to work under the fault conditions which could be useful for wind turbine operators. The servo-hydro-aeroelastic code HAWC2 is used to simulate the time domain responses of the spar-type offshore floating wind turbine under normal and faulty operational conditions. The rain-flow cycle counting method is used to calculate the load cycles under normal operational and fault conditions. The short term fatigue damage to the composite blade root and steel structures are calculated for 6-hour reference period. The bi-linear Goodman diagram and a linear SN curve are used to estimate the fatigue damage to the composite blade root and the steel structures respectively. Moreover the fatigue damage for different mean wind speeds, sea states and fault amplitudes are calculated to figure out the region of wind speeds operation with the highest risk of damage.

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