Feasibility of Very Large Floating Structure as Offshore Wind Foundation: Effects of Hinge Numbers on Wave Loads and Induced Responses
Publication: Journal of Waterway, Port, Coastal, and Ocean Engineering
Volume 147, Issue 3
Abstract
Floating offshore wind is a rapidly growing technology that is attracting global interest. To date, most of the demonstrated concepts for offshore floating wind are based on a simple one turbine–one platform system, which might not be the most efficient approach for manufacturing, transportation, and onsite installation. Very large floating structures (VLFS), which allow for operation of multiple turbines, might be an effective alternative to traditional floating foundations. However, the large bending moment caused by waves is a major concern for a VLFS foundation. Adding hinges into the structure might help to alleviate the bending moment. Based on the discrete-module-beam-bending hydroelasticity method, the effects of hinge numbers on the bending moment will be investigated in detail and will be presented in this paper. Overall, the bending moment is reduced when the vertical displacement is increased by the addition of hinges, which indicates a compromise when choosing hinge numbers. In addition, a feasibility study for the application of the multihinged VLFS as a floating wind platform will be provided. It demonstrates that the existence of wind turbines might further reduce the wave-induced bending moment, but they enlarge the total bending moment by introducing a still water bending moment. The effect of wind turbines on the vertical displacement of the multihinged VLFS is insignificant.
Get full access to this article
View all available purchase options and get full access to this article.
Data Availability Statement
Some or all data, models, or codes that support the findings of this paper are available from the corresponding author upon reasonable request.
Acknowledgments
The authors would like to acknowledge the support of the SuperGen Offshore Renewable Energy (ORE) Hub program funded by the Engineering and Physical Sciences Research Council (EPSRC), Grant EP/S000747/1. The first author is supported by Shanghai Pujiang Program (Grant No. 19PJ1405400), State Key Laboratory of Ocean Engineering (Grant No. GKZD010077), State Key Laboratory of Coastal and Offshore Engineering (Grant No. LP2019), the 2020 Research Program of Sanya Yazhou Bay Science and Technology City (Grant No. SKJC-2020-01-006), and Hainan Provincial Natural Science Foundation of China (Grant no. 520QN290).
Notation
The following symbols are used in this paper:
- A
- incoming wave amplitude;
- B(ω)
- radiation damping;
- C
- hydrostatic restoring coefficient matrix;
- FA
- added mass force;
- FE
- wave excitation force;
- FHs
- hydrostatic force;
- FJ
- force vector for the hinge connection;
- FRd
- radiation damping force;
- FSt
- structural deformation-induced force;
- Fz
- shear force at the hinge;
- Ke
- beam element stiffness matrix;
- KSt
- stiffness Matrix of the entire structure;
- L
- length;
- M
- mass matrix;
- N
- submodules number;
- Δz
- vertical displacement;
- βλ
- wavelength;
- ξ
- (complex) displacement vector of each rigid submodule;
- constraint matrix;
- Ψ(ω)
- added mass; and
- ω
- wave frequency.
References
Floating Power Plant AS. 2013. “The P37.” Accessed August 28, 2019. http://www.floatingpowerplant.com/products/.
Fu, S., T. Moan, X. Chen, and W. Cui. 2007. “Hydroelastic analysis of flexible floating interconnected structures.” Ocean Eng. 34 (11–12): 1516–1531. https://doi.org/10.1016/j.oceaneng.2007.01.003.
Inoue, K. 2005. “Development of a floating wind farm with a mooringless system.” In Proc., 18th Symp. on the Ocean Engineering. SNAJ.
Jonkman, J., S. Butterfield, W. Musial, and G. Scott. 2009. Definition of a 5-MW reference wind turbine for offshore system development. Golden, CO: National Renewable Energy Lab. (NREL).
Kim, D., L. Chen, and Z. Blaszkowski. 1999. “Linear frequency domain hydroelastic analysis for McDermott’s mobile offshore base using WAMIT.” In Proc., 3rd Int. Workshop on Very Large Floating Structures, edited by R. Cengiz Ertekin, 105–113. Honolulu, HI: Np.
Lu, D., S. Fu, X. Zhang, F. Guo, and Y. Gao. 2019. “A method to estimate the hydroelastic behaviour of VLFS based on multi-rigid-body dynamics and beam bending.” Ships Offshore Struct. 14 (4): 354–362. https://doi.org/10.1080/17445302.2016.1186332.
Manabe, H., T. Uehiro, M. Utiyama, H. Esaki, T. Kinoshita, K. Takagi, H. Okamura, and M. Satou. 2008. “Development of the floating structure for the sailing-type Offshore Wind Farm.” In OCEANS 2008-MTS/IEEE Kobe Techno-Ocean, 1–4. New York: IEEE.
Newman, J. N. 1994. “Wave effects on deformable bodies.” Appl. Ocean Res. 16 (1): 47–59. https://doi.org/10.1016/0141-1187(94)90013-2.
Riggs, H. R., R. C. Ertekin, and T. R. J. Mills. 2000. “A comparative study of RMFC and FEA models for the wave-induced response of a MOB.” Mar. struct. 13 (4–5): 217–232. https://doi.org/10.1016/S0951-8339(00)00029-0.
Robertson, A., J. Jonkman, F. Wendt, A. Goupee, and H. Dagher. 2016. Definition of the OC5 DeepCwind semisubmersible floating system. Technical report. Golden, CO: NREL.
Stansby, P., E. C. Moreno, and T. Stallard. 2015. “Capture width of the three-float multi-mode multi-resonance broadband wave energy line absorber M4 from laboratory studies with irregular waves of different spectral shape and directional spread.” J. Ocean Eng. Mar. Energy 1 (3): 287–298. https://doi.org/10.1007/s40722-015-0022-6.
Sun, Y., D. Lu, J. Xu, and X. Zhang. 2018. “A study of hydroelastic behavior of hinged VLFS.” Int. J. Nav. Archit. Ocean Eng. 10 (2): 170–179. https://doi.org/10.1016/j.ijnaoe.2017.05.002.
Suzuki, H. 2005. “Overview of Megafloat: Concept, design criteria, analysis, and design.” Mar. Struct. 18 (2): 111–132. https://doi.org/10.1016/j.marstruc.2005.07.006.
Suzuki, H., B. Bhattacharya, M. Fujikubo, D. Hudson, H. Riggs, H. Seto, H. Shin, T. Shugar, Y. Yasuzawa, and Z. Zong. 2006. “ISSC committee VI. 2: Very large floating structures.” In Proc., 6th Int. Ship and Offshore Structures Congress, 394–442. ISSC.
van der Laan, P., S. J. Andersen, N. R. García, N. Angelou, G. Pirrung, S. Ott, M. Sjöholm, K. H. Sørensen, J. X. V. Neto, and M. C. Kelly. 2019. “Power curve and wake analyses of the Vestas multi-rotor demonstrator.” Wind Energy Sci. 4 (2): 251–271. https://doi.org/10.5194/wes-4-251-2019.
Wu, Y. 1984. “Hydroelasticity of floating bodies.” Ph.D. thesis, Dept. of Mechanical Engineering, Univ. of Brunel.
Wu, Y., D. Wang, H. R. Riggs, and R. C. Ertekin. 1993. “Composite singularity distribution method with application to hydroelasticity.” Mar. Struct. 6 (2–3): 143–163. https://doi.org/10.1016/0951-8339(93)90017-W.
Yago, K. 2003. “Basic study on a floating wind power system.” In Proc., 17th Ocean Engineering Symp., 127–134. Tokyo, Japan: The Society of Naval Architects of Japan.
Yago, K., and H. Endo. 1996. “On the hydroelastic response of box-shaped floating structure with shallow draft.” J. Soc. Naval Archit. Jpn. 1996 (180): 341–352. https://doi.org/10.2534/jjasnaoe1968.1996.180_341.
Zhang, X., and D. Lu. 2018. “An extension of a discrete-module-beam-bending-based hydroelasticity method for a flexible structure with complex geometric features.” Ocean Eng. 163: 22–28. https://doi.org/10.1016/j.oceaneng.2018.05.050.
Zhang, X., D. Lu, Y. Gao, and L. Chen. 2018. “A time domain discrete-module-beam-bending-based hydroelasticity method for the transient response of very large floating structures under unsteady external loads.” Ocean Eng. 164: 332–349. https://doi.org/10.1016/j.oceaneng.2018.06.058.
Information & Authors
Information
Published In
Journal of Waterway, Port, Coastal, and Ocean Engineering
Volume 147 • Issue 3 • May 2021
Copyright
© 2021 American Society of Civil Engineers.
History
Received: Feb 19, 2020
Accepted: Oct 14, 2020
Published online: Jan 20, 2021
Published in print: May 1, 2021
Discussion open until: Jun 20, 2021
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.