本文針對台灣西部離岸海域不同水深的浮動式海上風機的繫纜系統進行了建模與優化研究。考慮使用OC4-DeepCwind半潛式浮動平台和美國再生能源實驗室(NREL)開發的5兆瓦基準風力渦輪機。本文對繫纜的材料，類型和配置進行了擴展分析，以便為給定的水位選擇可行和可靠的繫纜設計。選定的繫纜系統包括有懸鏈式的studless chain和drag embedment anchor。考慮了三個公稱尺寸的繫纜直徑，包括有：直徑為95毫米，115毫米和135毫米。

使用此配置，再根據兩個認證機構Det Norske Veritas-Germanischer Lloyd(DNV GL)和American Petroleum Institute(API)的規定和建議，總共分析了五種針對不同水深（即5​​0米，60米，70米，80米，100 米）的繫纜設計。考慮基於50年回歸期的颱風波浪和10年回歸期海流條件的極限狀態、25年疲勞設計壽命的疲勞極限狀態以及1年回歸期颱風波浪的最大運作海況作為對繫纜斷裂強度、疲勞以及穩定性進行了長期的預測。 OrcaFlex 10.3d版本的數值軟體用於模擬和設計繫纜系統。出於實際原因，所有設計均考慮相同的海況條件，海床剖面，土壤類型，浮動平台，風力渦輪機，錨碇尺寸和繫纜材料。

這項研究的結果是50米水深的繫纜設計呈現出比其他水深都更重的繫纜，從而增加了硬件的成本。另一方面，100米水深的設計具有更長的繫纜，使該參數成為驅動成本的因素。這將導致最小的繫纜成本範圍介於水深60米至80米之間。

This thesis presents a study about the modeling and optimization of mooring systems for floating offshore wind turbines (FOWT) for different water depths in Taiwan western offshore areas. A semi-submersible floating wind turbine system is considered based on Offshore Code Comparison Collaborative Continuation (OC4) DeepCwind platform and the National Renewable Energy Laboratory (NREL) offshore 5-MW baseline wind turbine. Extended analysis on the materials, types and configurations of the mooring line are presented in this thesis in order to select the feasible and reliable option for the given water sites. The mooring system proposed consists of a catenary mooring with studless chain and a drag embedment anchor (DEA). Three nominal sizes of the mooring chain links are taken into account: diameter of 95 mm, 115 mm and 135 mm.

With this configuration, a total of five mooring designs for different water depths (i.e. 50 m, 60 m, 70 m, 80 m, 100 m) are analyzed according to the rules and regulations of the two certification institutions, Det Norske Veritas and Germanischer Lloyd (DNV GL) and American Petroleum Institute (API). Considering ultimate limit state (ULS), fatigue limit state (FLS) and maximum operating sea state (MOSS) based on a storm with a 50-year return period and current with a 10-year return period, 25-year design life, as well as 1-year return period respectively, long-term predictions of breaking strength, fatigue and stability are performed. The software OrcaFlex version 10.3d is used to simulate and design the mooring systems. For the practical reasons, all designs consider the same metocean conditions, seabed profile, soil type, floating platform, wind turbine, anchor size and mooring material.

As a result of this study, the shallow mooring design of 50 m water case presents heaviest chains among the other water cases, driving their mooring costs. On the other hand, 100 m waters design has much longer mooring lines, making this parameter the cost driving ones. This fact leads to a minimum range is from 60 m to 80 m water depth.

[1] GWEC. (2019). Global wind energy council report 2018. Wind Global Council Energy, April, 1–61.
[2] DNV GL, DNVGL-OS-E301. Offshore Standard Position Mooring, 2018.
[3] API RP 2SK, Recommended Practice for Design and Analysis of Stationkeeping Systems for Floating Structures, third ed, American Petroleum Institute, Octorber 2005. Addendum 2008; Reaffirmed 2015.
[4] EWEA, "Deep water. The next step for offshore wind energy", 2013.
[5] Chang, P. C., Yang, R. Y., &Lai, C. M. (2015). Potential of offshore wind energy and extreme wind speed forecasting on the west coast of Taiwan. Energies, 8(3), 1685–1700.
[6] Robertson, A., Jonkman, J., Masciola, M., Song, H., Goupee, A., Coulling, A., &Luan, C. (2012). Definition of the Semi-submersible Floating System for Phase II of OC4. September.
[7] N. Bastick, 2009, Blue H-the world’s first floating wind turbine, in: The First Dutch Offshore Wind Energy Conference, February 12 and 13, 2009, Den Helder, The Netherlands, Essential Innovations.
[8] S. Bratland, 2009, Hywind-the world first full-scale floating wind turbine, in: Seminar and B2B Meetings “Powering the Future- Marine Energy Opportunities”, November 5, 2009, Lisbon, Portugal.
[9] A. Aubault, C. Cermelli, A. Lahijanian, A. Peiffer, D. Roddier, WindFloat contraption: from conception to reproduction, ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering, American Society of Mechanical Engineers, 2012, pp.847-853.
[10] Ma, K. T., Luo, Y., Kwan, T., &Wu, Y. (2019). Mooring system engineering for offshore structures. In Mooring System Engineering for Offshore Structures. Elsevier.
[11] James R., Ros M.C. Floating offshore wind: market and technology review. The Carbon Trust. June 2015.
[12] ABS. (2017). Guidance Notes on Certification of Offshore Mooring Chain. American Bureau of Shipping, May, 55.
[13] Chaplin, C. R., Potts, A. E., & Curtis, A. (2008). Degradation of wire rope mooring lines in SE Asian waters. Offshore Asia 2008, 1–20.
[14] Anon. Steel Wire Ropes and Fittings, Bridon Ropes, 1992.
[15] Sudaia, D. P., Bastos, M. B., Fernandes, E. B., Nascimento, C. R., Pacheco, E. B. A. V., & da Silva, A. L. N. (2018). Sustainable recycling of mooring ropes from decommissioned offshore platforms. Marine Pollution Bulletin, 135, 357–360.
[16] Davies, P., Weller, S. D., Johanning, L., & Banfield, S. J. (2014). A review of synthetic fiber moorings for marine energy applications A review of synthetic fiber moorings for marine energy applications. In: 5th International Conference on Ocean Energy (ICOE 2014), Halifax/Canada.
[17] Jonkman, J. M., & Matha, D. (2011). Dynamics of offshore floating wind turbines — analysis of three concepts. Wind Energy, 14(4), 557–569.
[18] Toledo Monfort, D., Cyril Godreau João Manuel Ribeiro Costa Baltazar, E., & Alberto Caiado Falcão do Campos, J. (2017). Design optimization of the mooring system for a floating offshore wind turbine foundation Energy Engineering and Management Examination Committee. November.
[19] A. Almar-Naess, Fatigue Handbook: Offshore Steel Structures, Tapir Academic Press, Trondheim, Norway, 1985.
[20] M. Matsuishi, T. Endo, Fatigue of Metals Subjected to Varying Stress, Japan Society of Mechanical Engineers, Fukuoka, 1968.
[21] American Bureau of Shipping, Guide for Position Mooring, 2018.
[22] DNV GL, DNVGL-OS-J103. Design of Floating Wind Turbine Structures, 2013.
[23] Orcina Ltd., OrcaFlex Version 10.3d, 2019.
[24] Jonkman, J., Butterfield, S., Musial, W., Scott, G., Jonkman, J., Butterfield, S., Musial, W., & Scott, G. (2009). Definition of a 5-MW Reference Wind Turbine for Offshore System Development.
[25] IEC 61400-3, Wind Turbines-Part 3: Design Requirements for Offshore Wind Turbines, 1.0 ed., 2009.
[26] Coulling, A. J., Goupee, A. J., Robertson, A. N., Jonkman, J. M., & Dagher, H. J. (2013). Validation of a FAST semi-submersible floating wind turbine numerical model with DeepCwind test data. Journal of Renewable and Sustainable Energy, 5(2).
[27] Masciola, M., Robertson, A., Jonkman, J., Coulling, A., &Goupee, A. (2013). Assessment of the importance of mooring dynamics on the global response of the DeepCwind floating semi-submersible offshore wind turbine. Proceedings of the International Offshore and Polar Engineering Conference, 359–368.
[28] Tran, T. T., &Kim, D. H. (2015). The coupled dynamic response computation for a semi-submersible platform of floating offshore wind turbine. Journal of Wind Engineering and Industrial Aerodynamics, 147, 104–119.
[29] Izadparast, A., Heyl, C., Ma, K. T., Vargas, P., & Zou, J. (2018). Guidance for assessing Out-of-Plane Bending fatigue on chain used in permanent mooring systems. In 23rd Offshore Symposium 2018 (pp. 101–114). Society of Naval Architects and Marine Engineers (SNAME) Texas Section.