# Study on Mooring Design of 15 MW Floating Wind Turbines in South China Sea

^{1}

^{2}

^{3}

^{4}

^{5}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Methodology and Design Procedure

#### 2.1. Methodology

#### 2.1.1. Time Domain Motion Equation

#### 2.1.2. Weibull Distribution

#### 2.1.3. Rain Flow Counting Method and Goodman Correction

#### 2.1.4. Linear Fatigue Cumulative Damage Rule

#### 2.2. Design Procedure

## 3. Numerical Model and Hydrodynamic Coefficient Verification

#### 3.1. Turbine and Platform Characteristics

#### 3.2. Initial Mooring Design

## 4. Mooring Design and Optimization

#### 4.1. Environmental Condition

#### 4.2. Optimization Based on Mooring Maximum Breaking Limit and Fatigue Damage

#### 4.3. Mooring Optimization—Anchor Point

#### 4.4. Mooring Optimization—Nominal Diameter

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

- Global Wind Report 2023. Available online: https://gwec.net/globalwindreport2023/ (accessed on 15 July 2023).
- Lantz, E.; Wiser, R.; Hand, M. IEA Wind Task 26 the Past and Future Cost of Wind Energy; Technical Report; National Renewable Energy Lab.(NREL): Golden, CO, USA, 2012. [Google Scholar]
- Chen, M.; Li, C.B.; Lee, J. A Simulation Technique for Monitoring the Real-time Stress Responses of Various Mooring Configurations for Offshore Floating Wind Turbines. Ocean. Eng.
**2023**, 278, 114366. [Google Scholar] [CrossRef] - Barrera, C.; Battistella, T.; Guanche, R.; Losada, I.J. Mooring system fatigue analysis of a floating offshore wind turbine. Ocean. Eng.
**2020**, 195, 106670. [Google Scholar] [CrossRef] - Li, C.B.; Choung, J. Fatigue damage analysis for a floating offshore wind turbine mooring line using the artificial neural network approach. Ships Offshore Struct.
**2017**, 12, 288–295. [Google Scholar] [CrossRef] - Wang, Z.; Qiao, D.; Yan, J.; Tang, G.; Li, B.; Ning, D. A new approach to predict dynamic mooring tension using LSTM neural network based on responses of floating structure. Ocean. Eng.
**2022**, 249, 110905. [Google Scholar] [CrossRef] - Campanile, A.; Piscopo, V.; Scamardella, A. Mooring design and selection for floating offshore wind turbines on intermediate and deep water depths. Ocean. Eng.
**2018**, 148, 349–360. [Google Scholar] [CrossRef] - Hall, M.; Goupee, A. Validation of a lumped-mass mooring line model with DeepCwind semisubmersible model test data. Ocean. Eng.
**2015**, 104, 590–603. [Google Scholar] [CrossRef] - Pillai, A.C.; Gordelier, T.J.; Thies, P.R.; Dormenval, C.; Wray, B.; Parkinson, R.; Johanning, L. Anchor loads for shallow water mooring of a 15 MW floating wind turbine—Part I: Chain catenary moorings for single and shared anchor scenarios. Ocean. Eng.
**2022**, 266, 111816. [Google Scholar] [CrossRef] - Pillai, A.C.; Gordelier, T.J.; Thies, P.R.; Cuthill, D.; Johanning, L. Anchor loads for shallow water mooring of a 15 MW floating wind turbine—Part II: Synthetic and novel mooring systems. Ocean. Eng.
**2022**, 266, 112619. [Google Scholar] [CrossRef] - Xu, S.; Soares, C.G. Guedes Soares. Experimental investigation on short-term fatigue damage of slack and hybrid mooring for wave energy converters. Ocean Eng.
**2019**, 195, 106618. [Google Scholar] [CrossRef] - Ahn, H.; Ha, Y.-J.; Kim, K.-H. Load Evaluation for Tower Design of Large Floating Offshore Wind Turbine System According to Wave Conditions. Energies
**2023**, 16, 1862. [Google Scholar] [CrossRef] - Zhao, G.; Zhao, Y.; Dong, S. System reliability analysis of mooring system for floating offshore wind turbine based on environmental contour approach. Ocean. Eng.
**2023**, 285, 115157. [Google Scholar] [CrossRef] - Ding, W.-W.; Jiang, J.-Q.; Yue, W.-Z.; Li, Y.-Z.; Wang, W.-S.; Sheng, S.-W.; Chen, M. Numerical Study on Hydrodynamic Performance of a New Semi-Submersible Aquaculture Platform. Appl. Sci.
**2023**, 13, 12652. [Google Scholar] [CrossRef] - Trubat, P.; Molins, C.; Gironella, X. Wave hydrodynamic forces over mooring lines on floating offshore wind turbines. Ocean. Eng.
**2020**, 195, 106730. [Google Scholar] [CrossRef] - Chueh, C.-J.; Chien, C.-H.; Lin, C.; Lin, T.-Y.; Chiang, M.-H. Dynamic Co-Simulation Analysis and Control of an IEA 15MW Offshore Floating Semi-Submersible Wind Turbine under Offshore Wind-Farm Conditions of Wind and Wave. J. Mar. Sci. Eng.
**2023**, 11, 173. [Google Scholar] [CrossRef] - Mazarakos, T.P. Wind Energy Calculations of a 15 MW Floating Wind Turbine System in the Mediterranean Sea. Environ. Sci. Proc.
**2023**, 26, 191. [Google Scholar] [CrossRef] - Benassai, G.; Campanile, A.; Piscopo, V.; Scamardella, A. Mooring control of semi-submersible structures for wind turbines. Procedia Eng.
**2014**, 70, 132–141. [Google Scholar] [CrossRef] - Chen, M.; Zhou, H.; Li, C.B. Fully Coupled Dynamic Analysis of the OO-STAR Floating Wind Turbine in Different Water Depths. In Proceedings of the 2022 ISOPE International Ocean and Polar Engineering Conference, Shanghai, China, 6–10 June 2022. [Google Scholar]
- Kim, H.; Jeon, G.-Y.; Choung, J. A Study on Mooring System Design of Floating Offshore Wind Turbine in Jeju Offshore Area. Int. J. Ocean. Syst. Eng.
**2013**, 3, 209–217. [Google Scholar] [CrossRef] - Li, C.B.; Chen, M.; Choung, J. The Quasi-Static Response of Moored Floating Structures Based on Minimization of Mechanical Energy. J. Mar. Sci. Eng.
**2021**, 9, 960. [Google Scholar] [CrossRef] - ANSYS Inc. ANSYS AQWA Theory Manual; ANSYS Inc.: Canonsburg, PA, USA, 2023. [Google Scholar]
- Zhao, Y.; Liao, Z.; Dong, S. Estimation of characteristic extreme response for mooring system in a complex ocean environment. Ocean. Eng.
**2021**, 225, 108809. [Google Scholar] [CrossRef] - Kebir, T.; Correia, J.; Benguediab, M.; Jesus, A.M.P.D. Numerical study of fatigue damage under random loading using rainflow cycle counting. Int. J. Struct. Integr.
**2021**, 12, 149–162. [Google Scholar] [CrossRef] - Yang, Y.; Bashir, M.; Wang, J.; Michailides, C.; Loughney, S.; Armin, M.; Hernández, S.; Urbano, J.; Li, C. Wind-wave coupling effects on the fatigue damage of tendons for a 10 MW multi-body floating wind turbine. Ocean. Eng.
**2020**, 217, 107909. [Google Scholar] [CrossRef] - Milne, I.; Ritchie, R.O.; Karihaloo, B.L. (Eds.) Comprehensive Structural Integrity: Cyclic Loading and Fatigue. Elsevier: Amsterdam, The Netherlands, 2003; Volume 4. [Google Scholar]
- Low, Y.M. Extending a time/frequency domain hybrid method for riser fatigue analysis. Appl. Ocean. Res.
**2011**, 33, 79–87. [Google Scholar] [CrossRef] - Du, J.; Wang, H.; Wang, S.; Song, X.; Wang, J.; Chang, A. Fatigue damage assessment of mooring lines under the effect of wave climate change and marine corrosion. Ocean. Eng.
**2020**, 206, 107303. [Google Scholar] [CrossRef] - Gaertner, E.; Rinker, J.; Sethuraman, L.; Zahle, F.; Anderson, B.; Barter, G.; Abbas, N.; Meng, F.; Bortolotti, P.; Skrzypinski, W.; et al. Definition of the IEA Wind 15-Megsestt Offshore Reference Wind Turbine. 2020, Technical Report. Available online: https://www.nrel.gov/docs/fy20osti/75698.pdf (accessed on 15 July 2023).
- Allen, C.; Viscelli, A.; Dagher, H.; Goupee, A.; Gaertner, E.; Abbas, N.; Hall, M.; Barter, G. Definition of the UMaine VolturnUS-S Reference Platform Developed for the IEA Wind 15Megawatt Offshore Reference Wind Turbine; 2020 Technical Report; National Renewable Energy Lab.(NREL): Golden, CO, USA, 2020. [Google Scholar]
- DNV. Offshore Standard DNV_OS_E301, Position Mooring; DNV: Bærum, Norway, 2010. [Google Scholar]
- Hazelton, M. Blyth Offshore Demonstration Project Phase 2—Supporting Environmental Information Blyth Offshore Demonstrator Phase 2 Works 1 Document Control, 2020, Technical Report, EDF Renewables. Available online: https://www.edf-re.uk/ (accessed on 18 December 2023).
- Connolly, P.; Hall, M. Comparison of pilot-scale floating offshore wind farms with shared moorings. Ocean. Eng.
**2019**, 171, 172–180. [Google Scholar] [CrossRef] - Guo, Y.; Wang, H.; Lian, J. Review of integrated installation technologies for offshore wind turbines: Current progress and future development trends. Energy Convers. Manag.
**2022**, 255, 115319. [Google Scholar] [CrossRef] - Hsu, W.-T.; Thiagarajan, K.P.; Manuel, L. Extreme mooring tensions due to snap loads on a floating offshore wind turbine system. Mar. Struct.
**2017**, 55, 182–199. [Google Scholar] [CrossRef] - Chen, M.; Ouyang, M.; Li, T.; Zou, M.; Ye, J.; Tian, X. Numerical modelling of a catamaran float-over deck installation for a spar platform with complex hydrodynamic interactions and mechanical couplings. Ocean. Eng.
**2023**, 287, 115905. [Google Scholar] [CrossRef] - Wang, Z.; Zhou, L.; Dong, S.; Wu, L.; Li, Z.; Mou, L.; Wang, A. Wind wave characteristics and engineering environment of the South China Sea. J. Ocean. Univ. China
**2014**, 13, 893–900. [Google Scholar] [CrossRef] - Chen, M.; Zou, M.; Zhu, L.; Ouyang, M.; Liang, Q.; Zhao, W. A Fully Coupled Time Domain Model Capturing Nonlinear Dynamics of Float-over Deck Installation. Available at SSRN 4583209. Available online: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4583209 (accessed on 18 December 2023).
- Yan, X.; Chen, C.; Yin, G.; Ong, M.C.; Ma, Y.; Fan, T. Numerical investigations on nonlinear effects of catenary mooring systems for a 10-MW FOWT in shallow water. Ocean. Eng.
**2023**, 276, 114207. [Google Scholar] [CrossRef] - Ghafari, H.; Dardel, M. Parametric study of catenary mooring system on the dynamic response of the semi-submersible platform. Ocean. Eng.
**2018**, 153, 319–332. [Google Scholar] [CrossRef] - DNV-OS-E302; Offshore Mooring Chain. DNV: Bærum, Norway, 2022.
- ISO20438; Ships and Marine Technology—Offshore Mooring Chains. ISO International Standards: Geneva, Switzerland, 2018.
- Ma, K.-T.; Luo, Y.; Kwan, T.; Wu, Y. Mooring System Engineering for Offshore Structures; Gulf Professional Publishing: Houston, TX, USA, 2019. [Google Scholar]
- Chen, M.; Ren, W.; Xiao, P.; Zhu, L.; Li, F.; Sun, L. Numerical analysis of a floating semi-submersible wind turbine integrated with a point absorber wave energy convertor. In Proceedings of the Thirtieth International Ocean and Polar, Virtual, 11 October 2020. [Google Scholar]
- Chen, M.; Xiao, P.; Zhou, H.; Li, C.B.; Zhang, X. Fully Coupled Analysis of an Integrated Floating Wind-Wave Power Generation Platform in Operational Sea-States. Front. Energy Res.
**2022**, 10, 931057. [Google Scholar] [CrossRef] - Liu, H.; Chen, M.; Han, Z.; Zhou, H.; Li, L. Feasibility Study of a Novel Open Ocean Aquaculture Ship Integrating with a Wind Turbine and an Internal Turret Mooring System. J. Mar. Sci. Eng.
**2022**, 10, 1729. [Google Scholar] [CrossRef] - Harrold, M.J.; Thies, P.R.; Newsam, D.; Ferreira, C.B.; Johanning, L. Large-scale testing of a hydraulic non-linear mooring system for floating offshore wind turbines. Ocean. Eng.
**2020**, 206, 107386. [Google Scholar] [CrossRef] - Xu, S.; Wang, S.; Soares, C.G. Experimental study of the influence of the rope material on mooring fatigue damage and point absorber response. Ocean. Eng.
**2021**, 232, 108667. [Google Scholar] [CrossRef]

**Figure 8.**The optimization iterative process of mooring lines (

**a**) Mooring line 2 (

**b**) Mooring line 3.

Parameter | Value |
---|---|

Power | 15 MW |

Rotor diameter | 240 m |

Hub height | 150 m |

Hub diameter | 6 m |

Blade mass | 65.7 t |

Rotor nacelle assembly mass | 1446 t |

Tower mass | 1211 t |

Tower diameter at base | 10 m |

Cut-in, Rated, Cut-out Speed | 3 m/s, 10.59 m/s, 25 m/s |

Cut-in, Cut-out speed | 4.6 rpm, 7.6 rpm |

Parameter | Value |
---|---|

Hull displacement | 20.206 m^{3} |

Hull steel mass | 3.914 t |

Tower interface mass | 100 t |

Draft | 20 m |

Freeboard | 14 m |

Vertical Center of Gravity form SWL | −14.94 m |

Vertical Center of Buoyancy form SWL | −13.63 m |

Roll Inertia about Center of Gravity | 1.251 × 10^{10} kg-m^{2} |

Pitch Inertia about Center of Gravity | 1.251 × 10^{10} kg-m^{2} |

Yaw Inertia about Center of Gravity | 2.367 × 10^{10} kg-m^{2} |

Parameter | Value |
---|---|

Mooring System Type | Chain Catenary |

Line Type | R3 Studless Mooring Chain |

Number of Lines | 3 |

Line Breaking Strength | 22,286 kN |

Nominal Chain Diameter | 185 mm |

Dry Line Linear Density | 685 kg/m |

Extensional Stiffness | 3270 MN |

Fairlead Pretension | 564 kN |

Anchor Type | Gravity anchor |

Anchor Weight | 20 t |

Line | Anchor Coordinates | Line Length [m] | ||
---|---|---|---|---|

x [m] | y [m] | z [m] | ||

1 | −330 | 0 | −70 | 300.68 |

2 | 165 | 285.79 | −70 | 300.68 |

3 | 165 | −285.79 | −70 | 300.68 |

Direction | 0° | 30° | 60° | 90° | 120° | 150° | 180° |

Probability | 50% | 8.33% | 8.33% | 8.33% | 8.33% | 8.33% | 33.33% |

Significant Wave Height ${\mathit{H}}_{\mathit{S}}\left[\mathit{m}\right]$ | $\mathbf{Spectral}\mathbf{Peak}\mathbf{Period}{\mathit{T}}_{\mathit{Z}}\left[\mathbf{s}\right]$ | ||||
---|---|---|---|---|---|

4.2 | 5.6 | 7 | 8.4 | 9.8 | |

0.5 | 4 | 25 | 10 | 4 | 0.6 |

1 | 2 | 13 | 9.5 | 2 | 1.2 |

1.5 | 6 | 7 | 2 | 0.2 | |

2 | 0.6 | 5.5 | 1 | 0.1 | |

2.5 | 2 | 2 | 0.1 | ||

3 | 0.5 | 1 | 0.05 | ||

3.5 | 0.45 | 0.05 | |||

4 | 0.02 | 0.05 | |||

4.5 | 0.02 | 0.03 | |||

5 | 0.01 | 0.01 | |||

5.5 | 0.01 |

Tension [kN] | |
---|---|

Line 1 | 1037.99 |

Line 2 | 803.54 |

Line 3 | 908.85 |

Tension [kN] | |
---|---|

Line 1 | 4.36 × 10^{−7} |

Line 2 | 3.10 × 10^{−7} |

Line 3 | 3.33 × 10^{−7} |

Line | Anchor Coordinates | Line Length [m] | ||
---|---|---|---|---|

x [m] | y [m] | z [m] | ||

1 | −330 | 0 | −70 | 300.68 |

2 | 135 | 233.83 | −70 | 238.68 |

3 | 140 | −242.49 | −70 | 248.68 |

Parameter | Value | ||
---|---|---|---|

Line Type | R3 Studless Mooring Chain | ||

Line Breaking Strength | 16,405 kN | 22,286 kN | 26,749 kN |

Nominal Chain Diameter | 152 mm | 185 mm | 210 mm |

Dry Line Linear Density | 462 kg/m | 685 kg/m | 882 kg/m |

Extensional Stiffness | 1973.08 MN | 3270 MN | 3766.14 MN |

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |

© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Chen, M.; Jiang, J.; Zhang, W.; Li, C.B.; Zhou, H.; Jiang, Y.; Sun, X.
Study on Mooring Design of 15 MW Floating Wind Turbines in South China Sea. *J. Mar. Sci. Eng.* **2024**, *12*, 33.
https://doi.org/10.3390/jmse12010033

**AMA Style**

Chen M, Jiang J, Zhang W, Li CB, Zhou H, Jiang Y, Sun X.
Study on Mooring Design of 15 MW Floating Wind Turbines in South China Sea. *Journal of Marine Science and Engineering*. 2024; 12(1):33.
https://doi.org/10.3390/jmse12010033

**Chicago/Turabian Style**

Chen, Mingsheng, Jiale Jiang, Wei Zhang, Chun Bao Li, Hao Zhou, Yichen Jiang, and Xinghan Sun.
2024. "Study on Mooring Design of 15 MW Floating Wind Turbines in South China Sea" *Journal of Marine Science and Engineering* 12, no. 1: 33.
https://doi.org/10.3390/jmse12010033