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Special Section Articles

Experimental Comparison of Three Floating Wind Turbine Concepts

[+] Author and Article Information
Andrew J. Goupee

Advanced Structures and Composites Center,
University of Maine,
35 Flagstaff Road,
Orono, ME 04469
e-mail: agoupe91@maine.edu

Bonjun J. Koo, Kostas F. Lambrakos

Technip USA, Inc.,
11700 Katy Freeway, Suite 150,
Houston, TX 77079

Richard W. Kimball

Maine Maritime Academy,
54 Pleasant Street,
Castine, ME 04420

Habib J. Dagher

Advanced Structures and Composites Center,
University of Maine,
35 Flagstaff Road,
Orono, ME 04469

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received January 13, 2013; final manuscript received August 5, 2013; published online March 24, 2014. Assoc. Editor: Krish Thiagarajan.

J. Offshore Mech. Arct. Eng 136(2), 020906 (Mar 24, 2014) (9 pages) Paper No: OMAE-13-1003; doi: 10.1115/1.4025804 History: Received January 13, 2013; Revised August 05, 2013

Beyond many of Earth's coasts exists a vast deepwater wind resource that can be tapped to provide substantial amounts of clean, renewable energy. However, much of this resource resides in waters deeper than 60 m where current fixed bottom wind turbine technology is no longer economically viable. As a result, many are looking to floating wind turbines as a means of harnessing this deepwater offshore wind resource. The preferred floating platform technology for this application, however, is currently up for debate. To begin the process of assessing the unique behavior of various platform concepts for floating wind turbines, 1/50th scale model tests in a wind/wave basin were performed at the Maritime Research Institute Netherlands (MARIN) of three floating wind turbine concepts. The Froude scaled tests simulated the response of the 126 m rotor diameter National Renewable Energy Lab (NREL) 5 MW, horizontal axis Reference Wind Turbine attached via a flexible tower in turn to three distinct platforms, these being a tension leg-platform, a spar-buoy, and a semisubmersible. A large number of tests were performed ranging from simple free-decay tests to complex operating conditions with irregular sea states and dynamic winds. The high-quality wind environments, unique to these tests, were realized in the offshore basin via a novel wind machine, which exhibited low swirl and turbulence intensity in the flow field. Recorded data from the floating wind turbine models include rotor torque and position, tower top and base forces and moments, mooring line tensions, six-axis platform motions, and accelerations at key locations on the nacelle, tower, and platform. A comprehensive overview of the test program, including basic system identification results, is covered in previously published works. In this paper, the results of a comprehensive data analysis are presented, which illuminate the unique coupled system behavior of the three floating wind turbines subjected to combined wind and wave environments. The relative performance of each of the three systems is discussed with an emphasis placed on global motions, flexible tower dynamics, and mooring system response. The results demonstrate the unique advantages and disadvantages of each floating wind turbine platform.

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Figures

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Fig. 1

Clockwise from left: spar-buoy, TLP, and semisubmersible floating wind turbines utilized in model testing

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Fig. 2

Orientations and degrees of freedom (DOF) used during model testing

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Fig. 3

Theoretical and measured spectra for the (a) U10 = 17.0 m/s and (b) 24.0 m/s NPD dynamic winds

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Fig. 9

Semisubmersible (a) surge and (b) pitch response spectra for an Hs = 10.5 m sea state with three different wind conditions

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Fig. 8

Spar-buoy (a) surge and (b) pitch response spectra for an Hs = 10.5 m sea state with three different wind conditions

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Fig. 7

TLP (a) surge and (b) pitch response spectra for an Hs = 10.5 m sea state with three different wind conditions

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Fig. 6

Pitch response spectra for all three systems under wave only loading for the (a) Hs = 2.0 m, (b) 7.1 m, and (c) 10.5 m irregular waves

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Fig. 5

Surge response spectra for all three systems under wave only loading for the (a) Hs = 2.0 m, (b) 7.1 m, and (c) 10.5 m irregular waves

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Fig. 4

Theoretical and measured spectra for the (a) Hs = 2.0 m, Tp = 7.5 s, (b) Hs = 7.1 m, Tp = 12.1 s, and (c) Hs = 10.5 m, Tp = 14.3 s Joint North Sea Wave Observation Project (JONSWAP) irregular waves

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Fig. 10

Nacelle surge acceleration spectra for all three systems under three distinct combined steady wind and irregular wave conditions of (a) Um = 11.2 m/s and Hs = 2.0 m, (b) Um = 11.2 m/s and Hs = 7.1 m, and (c) Um = 21.8 m/s and Hs = 10.5 m

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Fig. 11

Tower base bending moment spectra for all three systems for two combined wind/wave conditions with U10 = 17.0 m/s dynamic wind and (a) Hs = 2.0 m and (b) Hs = 10.5 m sea states

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Fig. 12

Fairlead mooring tension response spectra for the (a) TLP, (b) spar-buoy, and (c) semisubmersible systems in a combined U10 = 17.0 m/s dynamic wind and Hs = 2.0 m sea state environment

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