Wave-Energy Conversion Through Relative Motion Between Two Single-Mode Oscillating Bodies (original) (raw)
Research Papers
Department of Physics, Norwegian University of Science and Technology NTNU, N-7034 Trondheim, Norway
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J. Falnes
Department of Physics, Norwegian University of Science and Technology NTNU, N-7034 Trondheim, Norway
J. Offshore Mech. Arct. Eng. Feb 1999, 121(1): 32-38 (7 pages)
Published Online: February 1, 1999
Wave-energy converters (WECs) need a reaction source against which the wave forces can react. As with shore-based WECs, sometimes also floating WECs react against a fixed point on the seabed. Alternatively, for a floating WEC, force reaction may be obtained by utilizing the relative motion between two bodies. A load force for energy conversion is assumed to be applied only to this relative motion. It is assumed that either body oscillates in one mode only (mostly, the heave mode is considered here). The system, if assumed to be linear, is proved to be phenomenologically equivalent to a one-mode, one-body system, for which the wave excitation force equals the force which is necessary to apply between the two bodies in order to ensure that they are oscillating with zero relative motion. It is discussed how this equivalent excitation force and also the intrinsic mechanical impedance of the equivalent system depend on the mechanical impedances for the two separate bodies, including the radiation impedance matrix (which combines radiation resistances and added masses). The equivalent system is applied for discussing optimum performance for maximizing the absorbed wave energy. It is shown that, for an axisymmetric system utilizing heave modes, it is possible to absorb an energy amounting to the incident wave power on a crest length which equals the wavelength divided by 2π, even though the power take-off is applied to the relative motion only. Moreover, it is shown that it is possible to obtain an equivalent excitation force which exceeds the wave excitation force on either body.
1.
,
1974
, “
Wave Power
,”
Nature
, Vol.
249
, pp.
720
–
724
.
2.
Masuda, Y., 1986, “An Experience of Pneumatic Wave Energy Conversion Through Tests and Improvement,” Utilization of Ocean Waves, eds., M. E. McCormick and Y. C. Kim, American Society of Civil Engineers, Symposium, La Jolla, CA, American Society of Civil Engineers, New York, NY, 1987, pp. 1–33.
3.
Whittaker, T. J. T., and Wells, A. A., 1978, “Experience With a Hydrodynamic Wave Power Device,” International Symposium on Wave and Tidal Energy, Canterbury, England, September 1978, ISBN 0 906085004, pp. B4-57–B4-72.
4.
Budal, K., 1985, “Floating Structure With Heave Motion Reduced by Force Compensation,” Proceedings, Fourth International Offshore Mechanics and Arctic Engineering Symposium, American Society of Mechanical Engineers, New York, 1985, Vol. 1, pp. 92–101.
5.
, and ,
1984
, “
Added Mass and Damping of a Sphere Section in Heave
,”
Applied Ocean Research
, Vol.
6
, pp.
45
–
53
.
6.
,
1883
, “
Sur un nouveau the´ore`me d’e´lectricite´ dynamique
,”
Comptes Rendues
, Vol.
97
, pp.
159
–
161
.
7.
Parks, P. C., 1980, “Wedges, Plates and Waves. Some Simple Mathematical Models of Wave Power Machines,” Power from Sea Waves, ed., B. Count, ISBN 0-12-193550-7, Academic Press, pp. 251–285.
8.
French, M. J., and Bracewell, R., 1985, “Heaving Point Absorbers Reacting Against an Internal Mass,” Hydrodynamics of Ocean Wave Utilization, eds., D. V. Evans and A. F. de O. Falca˜o, IUTAM Symposium, Lisbon, Portugal, 1985, Springer Verlag, Berlin, pp. 247–255.
9.
,
1995
, “
On Non-Causal Impulse Response Functions Related to Propagating Water Waves
,”
Applied Ocean Research
, Vol.
17
, pp.
379
–
389
.
10.
Eidsmoen, H., 1996, Simulation of a Slack-Moored Heaving-Buoy Wave-Energy Converter With Phase Control, Division of Physics, Norwegian University of Science and Technology NTNU, Trondheim (Technical report also available on internet address:http://WWW.phys.ntnu.no/grupper/stralbol/bolgegrp-e.html).
11.
,
1981
,
Maximum Wave-Power Absorption Under Motion Constraints
,
Applied Ocean Research
, Vol.
3
, pp.
200
–
203
.
12.
Evans, D. V., 1980, Some Analytic Results for Two and Three Dimensional Wave-Energy Absorbers, Power from Sea Waves, ed., B. Count, ISBN 0-12-193550-7, (Academic Press), pp. 213–249.
13.
, and ,
1985
, “
Surface Wave Interaction With Oscillating Bodies and Pressure Distributions
,”
Applied Ocean Research
, Vol.
7
, pp.
225
–
234
.
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