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Research Papers: Ocean Renewable Energy

Characteristics of Hydrodynamics and Generating Output of the Offshore Floating Wave Energy Device “Mighty Whale”

[+] Author and Article Information
Hiroyuki Osawa

e-mail: osawah@jamstec.go.jp

Tsuyoshi Miyazaki

e-mail: tsuyoshim@jamstec.go.jp
JAMSTEC,
2-15 Natsushima-cho,
Yokosuka, 237-0061, Japan

Shogo Miyajima

Akishima Laboratories, (Mitsui Zosen) Inc.,
1-1-50 Tsutsujigaoka,
Akishima, Tokyo, 192-0012, Japan
e-mail: miyajima@ak.mes.co.jp

Contributed by the Ocean Offshore and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received July 22, 2004; final manuscript received August 1, 2007; published online February 22, 2013. Assoc. Editor: Daniel T. Valentine.

J. Offshore Mech. Arct. Eng 135(1), 011901 (Feb 22, 2013) (9 pages) Paper No: OMAE-04-1028; doi: 10.1115/1.4007248 History: Received July 22, 2004; Revised August 01, 2007

In this paper, a new numerical calculation method is presented; it was developed for the analysis of the hydrodynamic characteristics of a floating, oscillating water column (OWC) type wave power device. The method is examined by comparing results calculated with the method with results of water tank experiments. The examination was concerned with the determination of hydrodynamic coefficients, characteristics of air pressure and water level in an air chamber, and characteristics of hull motion and wave energy absorption. The calculated results agreed with the results of water tank tests; the method presented adequately estimated the hydrodynamic characteristics of the floating OWC type wave power device, including the wave energy absorption effects. An estimation method is presented for the output power of a turbine-generator system. The method was developed for the design of the “Mighty Whale” turbine-generator system. Moreover, the method was assessed by comparing predictions with open sea test results. The mean value of the output power was estimated reasonably well. In conclusion, the estimation methods presented are useful for the design of floating OWC wave power devices. Such tools are useful for the designer interested in developing optimal wave power devices.

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References

Figures

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Fig. 1

Coordinate system with a floating type OWC wave power device with a bottom plate

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Fig. 2

Mighty Whale model 1/20

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Fig. 3

Added mass coefficient of heave

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Fig. 5

Pressure and water surface height in the center air chamber in heave oscillation (close)

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Fig. 6

Pressure and water surface height in the center air chamber in heave oscillating (open)

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Fig. 7

Motions and efficiency of wave power absorption in head sea (θ = 180 deg)

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Fig. 8

Torque coefficient, coefficient of pressure drop, and efficiency of air turbine versus attack angle

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Fig. 9

Turbine differential pressure versus water surface velocity in an air chamber

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Fig. 10

Turbine output versus water surface velocity in an air chamber

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Fig. 11

Time series of wave height, rotational speed, and generated output (H1/3 = 1.16 m, T1/3 = 6.7 s)

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Fig. 12

Comparison of characteristic of output, estimate generated output, and open sea test output (H1/3 = 0.67 m, T1/3 = 6.8 s)

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Fig. 13

Comparison of characteristic of output, estimate generated output, and open sea test output (H1/3 = 1.16 m, T1/3 = 6.7 s)

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Fig. 14

Comparison of characteristic of output, estimate generated output, and open sea test output (H1/3 = 1.7 m, T1/3 = 7.0 s)

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