The present paper concerns an oscillating water column (OWC) spar-buoy, possibly the simplest concept for a floating OWC wave energy converter. It is an axisymmetric device (and so insensitive to wave direction) consisting basically of a (relatively long) submerged vertical tail tube open at both ends and fixed to a floater that moves essentially in heave. The length of the tube determines the resonance frequency of the inner water column. The oscillating motion of the internal free surface relative to the buoy, produced by the incident waves, makes the air flow through a turbine that drives an electrical generator. It is well known that the frequency response of point absorbers like the spar buoy is relatively narrow, which implies that their performance in irregular waves is relatively poor. Phase control has been proposed to improve this situation. The present paper presents a theoretical investigation of phase control through the latching of an OWC spar-buoy in which the compressibility of air in the chamber plays an important role (the latching is performed by fast closing and opening an air valve in series with the turbine). In particular, such compressibility may remove the constraint of the latching threshold having to coincide with an instant of zero relative velocity between the two bodies (in the case under consideration, between the floater and the OWC). The modeling is performed in the time domain for a given device geometry and includes the numerical optimization of the air turbine rotational speed, chamber volume, and latching parameters. Results are obtained for regular waves.

References

References
1.
Falcão
,
A. F. de O.
,
2010
, “
Wave Energy Utilization: A Review of the Technologies
,”
Renewable Sustainable Energy Rev.
,
14
, pp.
899
918
.10.1016/j.rser.2009.11.003
2.
Wells
,
A. A.
,
1976
, “
Fluid Driven Rotary Transducer
,” UK Patent Spec. No. 1595700.
3.
Masuda
,
Y.
, and
McCormick
,
M. E.
,
1986
, “
Experiences in Pneumatic Wave Energy Conversion in Japan
,”
Proceeding of the ASCE Specialty Conference on Utilization of Ocean Waves-Wave to Energy Conversion
,
M. E.
McCormick
and
Y. C.
Kim
, eds., pp.
1
33
.
4.
Masuda
,
Y.
,
1986
, “
An Experience With Wave Power Generation Through Tests and Improvement
,”
IUTAM Symposium Hydrodynamics of Ocean-Wave Energy Utilisation
,
D. V.
Evans
and
A. F. de O.
Falcão
, eds.,
Springer-Verlag
,
New York
, pp.
445
452
.
5.
Whittaker
,
T. J. T.
, and
McPeake
,
F. A.
,
1986
, “
Design Optimization of Axisymmetric Tail Tube Buoys
,”
IUTAM Symposium Hydrodynamics of Ocean-Wave Energy Utilisation
,
D. V.
Evans
and
A. F. de O.
Falcão
, eds.,
Springer-Verlag
,
New York
, pp.
103
111
.
6.
Tucker
,
A.
,
Pemberton
,
J. M.
,
Swift-Hook
,
D. T.
,
Swift-Hook
,
J. M.
,
Burrett
,
M. J.
, and
Phillips
,
J. W.
,
2010
, “
Laminated Reinforced Concrete Technology for the SPERBOY Wave Energy Converter
,”
Proceedings of the 11th World Renewable Energy Congress
, pp.
941
946
.
7.
Department of Trade and Industry (UK)
,
2005
, “
Nearshore Floating Oscillating Wave Column: Prototype Development and Evaluation
,” Report No. URN 05/581, http://www.berr.gov.uk/files/file17347.pdf
8.
McCormick
,
M. E.
,
1974
, “
Analysis of a Wave Energy Conversion Buoy
,”
J. Hydronaut.
,
8
, pp.
77
82
.10.2514/3.62983
9.
McCormick
,
M. E.
,
1976
, “
A Modified Linear Analysis of a Wave-Energy Conversion Buoy
,”
Ocean Eng.
,
3
, pp.
133
144
.10.1016/0029-8018(76)90029-9
10.
Korde
,
U. A.
,
2000
, “
A Note on the Hydrodynamics of a Tail Tube Buoy
,”
Ocean Eng.
,
27
(
12
), pp.
1473
1484
.10.1016/S0029-8018(99)00053-0
11.
Gomes
,
R. P. F.
,
Henriques
,
J. C. C.
,
Gato
,
L. M. C.
, and
Falcão
,
A. F. O.
,
2012
, “
Hydrodynamic Optimization of an Axisymmetric Floating Oscillating Water Column for Wave Energy Conversion
,”
Renewable Energy
,
44
, pp.
328
339
.10.1016/j.renene.2012.01.105
12.
Falnes
,
J.
,
2002
, “
Optimum Control of Oscillation of Wave-Energy Converters
,”
Int. J. Offshore Polar Eng.
,
12
(
2
), pp.
147
155
.
13.
Falnes
,
J.
, and
Budal
,
K.
,
1978
, “
Wave-Power Absorption by Point Absorbers
,”
Norw. Marit. Res.
,
6
, pp.
2
11
.
14.
Budal
,
K.
, and
Falnes
,
J.
,
1980
, “
Interacting Point Absorbers With Controlled Motion
,”
Power From the Waves
,
B.
Count
, ed.,
Academic Press
,
London
, pp.
381
399
.
15.
Babarit
,
A.
, and
Clement
,
A.
,
2006
, “
Optimal Latching Control of a Wave Energy Device in Regular and Irregular Waves
,”
Appl. Ocean Res.
,
28
, pp.
77
91
.10.1016/j.apor.2006.05.002
16.
Falcão
,
A. F. de O.
,
Justino
,
P. A. P.
,
Henriques
,
J. C. C.
, and
André
,
J. M. C. S.
,
2008
, “
Modelling and Control of the IPS Buoy
,”
Proceedings of the 2nd International Conference of Ocean Energ
y
.
17.
Henriques
,
J. C. C.
,
Lopes
,
M. F. P.
,
Gomes
,
R. P. F.
,
Gato
,
L. M. C.
, and
Falcão
,
A. F. O.
,
2012
, “
On the Annual Wave Energy Absorption by Two-Body Heaving WECs With Latching Control
,”
Renewable Energy
,
45
, pp.
31
40
.10.1016/j.renene.2012.01.102
18.
Falcão
,
A. F. O.
,
Gato
,
L. M. C.
, and
Nunes
,
E. P. A. S.
,
2013
, “
A Novel Radial Self-Rectifying Air Turbine for Use in Wave Energy Converters
,”
Renewable Energy
,
50
, pp.
289
298
.10.1016/j.renene.2012.06.050
19.
Clément
,
A. H.
, and
Babarit
,
A.
,
2012
, “
Discrete Control of Resonant Wave Energy Devices
,”
Philos. Trans. R. Soc. London Ser. A
,
370
, pp.
288
314
.10.1098/rsta.2011.0132
20.
Falcão
,
A. F. de O.
, and
Justino
,
P. A. P.
,
1999
, “
OWC Wave Energy Devices With Air Flow Control.
Ocean Eng.
,
26
, pp.
1275
1295
.10.1016/S0029-8018(98)00075-4
21.
Dixon
,
S. L.
,
1998
,
Fluid Mechanics and Thermodynamics of Turbomachinery
,
4th ed.
,
Butterworth
,
London
.
22.
Watkins
,
D. S.
,
1991
,
Fundamentals of Matrix Computations
,
John Wiley & Sons
,
New York
.
23.
Storn
,
R.
, and
Price
,
K.
,
1997
, “
Differential Evolution—A Simple and Efficient Heuristic for Global Optimization Over Continuous Spaces
,”
J. Global Optim.
,
11
(
4
), pp.
341
359
.10.1023/A:1008202821328
24.
Lee
,
C. H.
, and
Newman
,
J. N.
,
2005
, “
Computation of Wave Effects Using the Panel Method
,”
Numerical Models in Fluid-Structure Interaction
,
S.
Chakrabarti
, ed.,
WIT Press
,
Southampton, UK
.
You do not currently have access to this content.