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WO2013030359A2 - Système de conversion d'énergie houlomotrice - Google Patents

Système de conversion d'énergie houlomotrice Download PDF

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Publication number
WO2013030359A2
WO2013030359A2 PCT/EP2012/067001 EP2012067001W WO2013030359A2 WO 2013030359 A2 WO2013030359 A2 WO 2013030359A2 EP 2012067001 W EP2012067001 W EP 2012067001W WO 2013030359 A2 WO2013030359 A2 WO 2013030359A2
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WO
WIPO (PCT)
Prior art keywords
wave energy
energy absorber
wave
pto
controller
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Ceased
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English (en)
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WO2013030359A3 (fr
Inventor
Carlos Villegas
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Wavebob Ltd
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Wavebob Ltd
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Publication of WO2013030359A3 publication Critical patent/WO2013030359A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F03B13/16—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem"
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F03B13/16—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem"
    • F03B13/18—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore
    • F03B13/1845—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" where the other member, i.e. rem is fixed, at least at one point, with respect to the sea bed or shore and the wom slides relative to the rem
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03B—MACHINES OR ENGINES FOR LIQUIDS
    • F03B13/00—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates
    • F03B13/12—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy
    • F03B13/14—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy
    • F03B13/16—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem"
    • F03B13/20—Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus; Power stations or aggregates characterised by using wave or tide energy using wave energy using the relative movement between a wave-operated member, i.e. a "wom" and another member, i.e. a reaction member or "rem" wherein both members, i.e. wom and rem are movable relative to the sea bed or shore
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2220/00—Application
    • F05B2220/70—Application in combination with
    • F05B2220/706—Application in combination with an electrical generator
    • F05B2220/707—Application in combination with an electrical generator of the linear type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2260/00—Function
    • F05B2260/96—Preventing, counteracting or reducing vibration or noise
    • F05B2260/964—Preventing, counteracting or reducing vibration or noise by damping means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05B—INDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2270/00—Control
    • F05B2270/10—Purpose of the control system
    • F05B2270/20—Purpose of the control system to optimise the performance of a machine
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/30—Energy from the sea, e.g. using wave energy or salinity gradient

Definitions

  • the present invention relates to a wave energy conversion system.
  • the present invention relates to a wave energy conversion system whichin a first arrangement is configured to reduce parametric resonance which causes large pitch motion in thesystem, and thus optimise power conversion efficiency.
  • the wave energy conversion system is configured to have a variable water piercing area so as to experience parametric resonance, which can be exploited to increase power capture.
  • Theavailable energy in the oscillating system may be transformed, via a power take-off (PTO), to useful electrical or other power.
  • PTO power take-off
  • the interaction between the oscillating bodies and the PTO is therefore of vital importance to the
  • one type of wave energy conversion system comprises a point absorber or heaving buoy wave energy absorber.
  • Point absorbers may be comprised of one or more buoys and extract energy from the motion of each buoy and/or their relative motion.
  • Each of such buoys has its own resonance frequency given mainly by its mass and geometry. The resonance frequency is particularly important for devices with more than one body as they tend to capture power mainly available between the highest and the lowest resonance frequencies.
  • Such wave energy absorbers have normally either a very short draught to become a wave follower (high resonance frequency) or a constant water piercing area for their operational range.
  • the main source of large pitch motions of a heaving buoy wave energy absorber can be associated with parametric resonance, whichis a nonlinear behaviour that affects floating bodies.
  • Parametric resonance has beenwidely investigated for ships and offshore platforms andhas been analyzed using various non-linear approaches such asdescribing functions, the circle criterion or the extended Popovcriterion.
  • Such behavior in the context of a heaving buoy wave energyabsorber arises from harmonic variations in the pitch
  • a system which reduces parametric resonance in order to optimise wave energy absorption.
  • Such a system comprises acontrolled power take off system that reduces parametric resonance of a wave energy absorber by using the concept of harmonic balance.
  • a wave energy absorber is provided with a variable water piercing area such that the absorber experiences parametric resonance under certain sea conditions.
  • Such geometry together with suitable control means allows the non-linear effects of parametric resonance to be exploited in order to increase power capture.
  • the present teaching provides a wave energy conversion system as detailed in claim 1 . Further, another wave energy conversion system is provided according to claim 39. Advantageous features are provided in the dependent claims.
  • Figure 1 is a block diagram showing the main components of a wave energy conversion system according to the present teaching
  • Figure 2 is aview of aheaving buoy wave energy absorber
  • Figure 3 is a graph showing a transfer function of vertical motion to wave amplitude for a high-damping coefficient and a low damping coefficient
  • Figure 4 is a graph illustrating the amplitude of a pitch transfer function G(s) plotted as a functionof frequency
  • Figure 5 is a graph showing wave elevation for experimental results with typical North Sea waveconditions
  • Figure 6 is a graph showing pitch motion for experimental results with typical North Sea wave conditions
  • Figure 7 is a graph showing mechanical power capture for experimental results with typical North Sea wave conditions
  • Figure8a is a block diagram illustrating how a notch filter is applied to a PTO force signal in a wave energy conversion system for reducing parametric resonance, according to the present teaching
  • Figure 8b illustrates Bode diagrams showing the frequency response of the notch filter of Figure 7a, according to the present teaching
  • Figure 9 is a graph illustrating the region where dangerous frequencies are excited at twice the resonance frequency in a wave energy absorber
  • Figures 10 and 1 1 are graphs illustrating methods of reducing parametric resonance by decreasing and increasing the natural frequency of a wave energy absorber, respectively, according to the present teaching
  • Figure 12 is a graph illustrating a method of reducing parametric resonance by increasing the damping factor in a wave energy absorber, according to the present teaching
  • Figures 13a and 13b respectively illustrate a side view and a top view of a wave energy absorber with fins and plates to increase damping in pitch, according to the present teaching
  • Figures 14a and 14b illustrate a wave energy absorber wherein the parametric resonance in pitch can be reduced by varying the water piercing area of the wave energy absorber;
  • Figure 15 illustrates an exemplary wave energy conversion system for harnessing wave energy
  • Figure 16a illustrates a buoy with a constant area
  • Figure 16b illustrates a buoy with a variable area relative to wave height and heave
  • Figure 17 illustrates examples of buoys with varying surface piercing area
  • Figure 18 is a Bode diagram illustrating the excitation force to heave transfer function for both heaving buoys in Figures 16 and 17;
  • Figures 19a and 19b are graphs illustrating a comparison of heave motion and mechanical power for both heaving buoys for a wave excitation at the natural frequency;
  • Figures 20a and 20b are graphs illustrating a comparison of heave motion and mechanical power for both heaving buoys for a wave excitation at twice the natural frequency;
  • Figures 21 a and 21 b are graphs illustrating a comparison of heave motion and mechanical power for both heaving buoys for a panchromatic wave excitation
  • Figures 22a and 22b respectively illustrate a two-body point absorber with constant area and with variable area relative to wave height and heave;
  • Figures 23a and 23b respectively illustrate a spar platform with an array of heaving buoys with constant area (a) and with variable area (b);
  • Figures 24a and 24b respectively illustrate a two-body point absorber with one body tethered to the sea floor with constant area (a) and with variable area (b) relative to wave height and heave.
  • the present teaching provides a wave energy conversion system which reduces parametric resonance due to pitch motion using a number of techniques.
  • a wave energy conversion system having a variable surface piercing area is provided which is configured to achieve parametric resonance in order to improve power capture.
  • FIG. 1 is a block diagram of an exemplary wave energy conversion system according to the present teaching.
  • the system includes a wave energy absorber 1 10 coupled to a power take off (PTO) 1 15.
  • a sensor 130 is provided for sensing operating parameters of waves 150 and the wave energy absorber 1 10.
  • a controller 120 is provided for determining the force at the PTO 1 15 in response to the sensed parameters of the waves 150 and the wave energy absorberl 10.
  • the controller 120 may be configured to allow a dynamic varying of at least one of the operating parametersto provide the required PTO force to vary the parametric resonance of the wave energy absorber 1 10.
  • the sensor 130 senses the operating parameters of the waves 150 and the wave energy absorberl 10 which are then read by the controller 120.
  • the controllerl 20 in response to the sensed operating parameters of the waves 150 and the wave energy absorberl 10, appropriately dynamically varies the operating parameters ofthe wave energy absorberl 10 so as to reduce the parametric resonance of the wave energy absorberl 10 in order to optimise power conversion efficiency or to achieve parametric resonance in order to maximise the power captured from the system.
  • the controller 120 is co- operable with the sensor 130 for selectively controlling the system.
  • the system may further include a calibration module 140 for calibrating the data read by the sensor 130. It will be appreciated therefore that the present teaching provides a feedback system whereby sensed operating parameters of the system and the waves are used to dynamically vary the parametric resonance of elements or components of the convertor, thereby maximising the power conversion efficiency. It will be appreciated that in certain configurations the controller 120 can also use the sensed operating parameters of the wave energy absorber 1 10 to estimate and/or predict the current and future parameters of the waves 150.
  • Harmonic balance arguments to postulate the existence of periodic motion to characterize the boundary of instability. It will be appreciated that the effect of the cosine is to split the feedback signal into two sidebands. Using Harmonic balance arguments, the condition for instability is that some frequency has a unity amplification and a phase shift of 2 ⁇ in the feedback loop.
  • FIG. 2 is a view of a heaving buoy wave energy absorberl .
  • the heaving buoy wave energy absorberl comprises an inner body 10, an outer floating body 1 1 , wherein the outer floating body 1 1 is annular and surrounds the inner bodyl 0. A significant portion 10a of the inner body 10 is located below the surface 20 of the body of liquid.
  • / e is the time-varying pitch restoring coefficient. Referto Table Ibelow for a description of the notation used.
  • the restoringcoefficient can be represented as a function of the displacedvolume and the metacentric height:
  • GM new GM - 0.5(5 - ⁇ ) (7)
  • V ne , V - Ai (z ! - ⁇ ) - A 2 (z 2 - ⁇ ) (8)
  • the new restoring coefficient k $ can be written as:
  • the Mathieu system may be used in analysing floating devices. While waves are not really periodic, it will be appreciated that given certain assumptions that they may be considered periodic, and given that the Mathieu analysiscan be extended to general periodic multipliers, the present inventor has realized that a study of this equation gives insights that can be used for the design of wave energy converters and their controllers. In particular, the Mathieu analysis shows that periodic multipliers that have significant frequency components at twice the resonant frequency of the pitch dynamics are most dangerous.
  • the present teaching provides a simple control design that is based on reducing the loop gain at this frequency. In particular, the present teaching provides an approach to reduce the harmonic excitations at half the resonance period by using the PTO force.
  • FIG. 4 The amplitude of G(s) is plotted as a function of frequency in Figure 4.
  • Figure 5 is a graph showing wave elevation for experimental results with typical North Sea wave conditions. Referring to Figure 5, the solid line represents high damping, the dashed line represents low damping, and the dotted line represents application of a notch filter.
  • simulations not involving parametric motion suggested using a high damping. However, experimental tests with such damping resulted in higher than expected pitch and much lower mechanical power capture, as illustrated in Figures 6 and 7.
  • Figure 6 is a graph showing pitch motion for experimental results with typical North Sea wave conditions
  • Figure 7 is a graph showing mechanical power capture for these experimental results.
  • the first approach was a reduction in the overall PTO damping D and the second involved application of a notch filter at half the resonance period to the reference PTO force. Both approaches reduced pitch motion and increased power.
  • a notch filter mainly the damping at half the resonance period of pitch was affected leading to higher power output and capacity factor than a reduced damping.
  • a description of the implementation of the notch filter is provided below.
  • FIG 15 illustrates an exemplary wave energy conversion systeml OO for harnessing wave energy.
  • the systeml OO comprises a power take-off (PTO) device in the form of a mechanical energy converter 102.
  • the mechanical energy converter 102 may be a linear switch reluctance (LSR) generator configured to convert mechanical energy into electrical energy.
  • LSR linear switch reluctance
  • the PTO may comprise another type of mechanical energy converter such as the application of actuators in the form of hydraulic pumps.
  • the mechanical energy converter 102 is coupled to and driven by a wave energy absorber 105. It will be understood that wave energy absorbers are known in the art, an example of which is shown in European Patent No.
  • This exemplary wave energy absorber 105 comprises at least two devices (floats) 1 10, 1 1 1 . While it is not intended to limit the teaching of the present invention to such a specific type of wave energy absorber, this specific absorber is described to assist in an understanding of a mechanical to electrical energy converter.
  • each of the two devices comprises aninner surface float 1 10, an outer surface float 1 1 1 , and/or at least one submerged wave driven body 1 15 below the surface of the body of liquid.
  • the outer surface float 1 1 1 is annular and surrounds the inner surface float 1 10.
  • Linkages 139 are provided between the at least two devices 1 10, 1 1 1 . By configuring each of the two devices 1 10, 1 1 1 to oscillate at different frequencies relative to one another in response to passing waves, relative movement between the at least two devices 1 10, 1 1 1 may be used to generate an energy transfer which may be harnessed by the linkages 139 between the at least two devices 1 10, 1 1 1 .
  • the linkages 139 are coupled to the generator 102 which harnesses the mechanical energy generated by the wave energy absorber 105 and converts the mechanical energy into electrical energy.
  • the mechanical energy converter 102 may be a linear switched reluctance (LSR) generator and is directly coupled to the wave energy absorber 105.
  • LSR linear switched reluctance
  • the mechanical energy converter 102 may also be a rotary switched reluctance generator with a linear to rotary conversion mechanism such as a rotary switched reluctance generator with a rack and pinion.
  • the converter 102 comprises a translating member 120 of electrical steel which is moveable axially and intermediate to a pair of spaced apart stator members 125 also of electrical steel.
  • the translating member 120 includes first and second sets of teeth 132 of rectangular cross section on its respective opposite sides which define translator poles.
  • Each stator member 125 includes teeth 138 on one side thereof of rectangular cross section which define stator poles.
  • the respective sides of the translating member 120 are associated with the corresponding stator members 125 such that the translator poles 132 and the stator poles 138 define opposing pole arrangements.
  • the translating member 120 is operably coupled to the wave driven body 1 15 via linkages and is axially moveable along rails (not shown) such that the translating member 120 reciprocates in tandem with the oscillating wave driven body 1 15.
  • the opposing pole arrangements are dimensioned such that air gaps 140 exist between the translator poles 132 and the stator poles 138.
  • the translating member 120 is coupled to the inner surface float 1 10, and each stator member 125 is coupled to the annular outer surface float 1 1 1 .
  • Copper coils 141 are wound around the stator poles 138.
  • the sequential energisation of these poles creates a magnetic field and a steady aligning force between opposing stator poles 138 and translator poles 132.
  • the translating member 120 moves against the steady aligning force thereby converting mechanical energyinto electrical energy.
  • the aligning force may be considered to be an operating characteristic of the generator 102.
  • a person skilled in the art will appreciate that, in motoring operation, a forwardelectromagnetic force (forward EMF) is produced when electric current flowing in a coil 141 coincides with rising coil inductance. In generating operation, a backward electromagnetic force (back EMF) is produced when the coil 141 current coincides with falling coilinductance.
  • forward EMF forwardelectromagnetic force
  • back EMF backward electromagnetic force
  • large pitch motion in a heaving buoy wave energy absorber may affect the available useful powerat the PTO.
  • the main source of large pitch motions can be associated with parametric resonance.
  • the present teaching provides various approachesto deal with parametric resonance for wave energy absorbers - such as shape adjustments, specific mooring designs, and pitch stability control means.
  • the system according to the present teaching includes a controller or control means that is configured for reducing such parametric resonance of the wave energy absorber.
  • the control means incorporates a number of techniques for reducing the parametric resonance, as will be described below. It will be appreciated that any of the below methods of reducing parametric resonance may be utilised alone or in conjunction with each other.
  • the control means comprises a filter which may be applied to the PTO force set point signal or any other operating parameter associated with the waves and/or wave energy converter such as the velocity and position sensed parameters of the translating member 120 of the wave energy conversion system 100 of FIG. 15.
  • the filter is applied to a signal representing force of the PTO, the PTO force setpoint signal.
  • Figure 8a is a block diagram illustrating a control means for reducing parametric resonance of a wave energy conversion system, according to an embodiment of the present teaching. Referring to Figure 8a, the system includes an adaptive filter 750, an actuator control 710, a PTO control means 720, a PTO 700, a wave energy converter730, and signal conditioning means 740.
  • the signal conditioning means 740 may be a band-stop filter in the form of a notch filter.
  • the notch filter tested by the inventors is mainly a filter for the velocity signal of the translating member 120 of Figure 15.
  • the filter 740 may be applied to a signal representing the force to be applied by the PTO 700.
  • the notch filter is applied at half the resonance period of the wave energy absorber to a signal representing the PTO force.
  • a typical frequency response of the notch filter 740 is illustrated in Figure 8b. Note that all the filters in Figure 8b have a notch roughly at 0.075 Hz.
  • a linear damping would be a constant value for all frequencies. For example, in the present teaching, a linear damping of roughly 1 ,800,000 N is used (Plot 1 without notch).
  • the parametric resonance may be reduced by changing the resonance frequency in pitch motion of the wave energy absorber.
  • the resonance frequency of the WEC can be adjusted such that the frequency content of ⁇ ⁇ - ⁇ ⁇ is away from twice the resonance frequency of
  • FIGS. 10 and 1 1 the resonance frequency ⁇ 3 ⁇ 4 K can be reduced or increased away fromtwice the resonance frequency of (b / 2)G(s)
  • G(s) l / (s 2 + ⁇ + ⁇ ) , having a magnitude amplification greater or equal to one.
  • the resonance frequency of a wave energy absorber with moorings can be adjusted in a number of ways. Referring to FIG. 2 and Table 1 above, the resonance frequency a> n of the wave energy absorber can be increased or decreased by varying at least one of the following:
  • the control means may comprise configuring the moorings, ballast and shape of the system to adjust the resonance frequency of the pitch resonance.
  • the damping term ⁇ of the linear pitch dynamics G(s) may be increased.
  • FIG. 12 is a graph showing the effect of increasing the damping term, showing how the amplitude of G(s) at the resonance frequency is reduced.
  • FIGs 13a and 13b respectively illustrate a side view and a top view of a wave energy absorber with one or more fins 4 and plates 5 to increase damping in pitch, according to the present teaching.
  • both fins 4or plates 5 could be attached to either body 1 or body 2 such that pitch damping (e.g. viscous drag) is increased mainly in pitch and roll with little effect on heave motion.
  • the fins may be disposed in a substantially vertical orientation. Note that the 3 ⁇ 4 term of the damping coefficient of pitch can be seen as a first order linearization of viscous drag.
  • one or more plates 5 may project outwardly from the outer portion of the body 2 of the wave energy absorber and are disposed in a substantially vertical orientation.
  • the long fins 4 or plates 5 present little drag in heave while they increase drag in roll and pitch motion.
  • the b g term of the damping coefficient of pitch can be seen as a first order linearization of viscous drag.
  • FIGS 14a and 14b illustrate a wave energy absorber wherein the parametric resonance in pitch motion can be reduced by varying the water piercing area of the wave energy absorber.
  • the parametric resonance in pitch motion can be reduced by varying the water piercing area of the wave energy absorber.
  • changes in metacentric height due to wave elevation can be reduced.
  • at least one of the inner and outer surface floats 2 and 3 may be configured to have a variable water piercing area.
  • At least one of the inner and outer surface floats 2 and 3 comprises an upper portion above the surface of the water 4, a lower
  • a wave energy absorber which comprises a variable water piercing area is provided such that the absorber experiences parametric resonance under certain sea conditions.
  • Such geometry together with suitable control means allow the non-linear effects of parametric resonance to be exploited in order to increase power capture.
  • control means are required to maintain stability and parametric oscillation. While resonance of typical wave energy absorbers is excited by waves at that same resonance frequency, parametric resonance is excited by waves at roughly twice the resonance frequency of the body. For example, waves of 2 Hz could cause parametric resonance of a body with resonance frequency of 1 Hz.
  • variable water piercing area changes linearly with respect to the water level.
  • parametric resonance may be achieved with other variable piercing areas including discrete area variations.
  • the wave energy absorber may be designed with natural frequencies away from critical sea conditions and capture such power using parametric resonance such that it would be easier to detune these frequencies from harsh sea conditions.
  • PTO power take off
  • the surface piercing area of the surface buoy 3 in Figure 16a is relatively constant with the waves 4 while the surface piercing area of the surface buoy 3 in Figure 16b varies with the waves 4.
  • both surface buoys will have a similar frequency response with a natural frequency w 0 .
  • the amplitude of the oscillations will be large while for waves away from the natural frequencies will be less.
  • the control means 6 uses sensor means 5 to measure the wave height and obtain the buoy elevation.
  • the control means 6 may also use means to predict wave elevation and wave energy converter parameters a few seconds ahead. Those variables are used to achieve parametric resonance and maintain overall stability.
  • FIG 17 illustrates examples of buoys with varying surface piercing area.
  • the buoys are described as a surface of revolution around an axis 6.
  • the area with no waves is given by the water level 5 and it changes linearly with changing wave elevation.
  • Parametric resonance can be excited either with smooth changing areas as in 1 and 2 or discrete changes as in 3 and 4.
  • the variations 2 and 4 may be employed.
  • FIG. 19a and 19b a sinusoidal wave excitation at the natural frequency is depicted.
  • the power capture between buoys (a) and (b) in Figure 16 would be similar.
  • the buoy (a) of Figure 16 will capture practically no power while buoy (b) will resonate and capture power from such waves.
  • the effect for real sea conditions is clear in Figure 21 where much more power is captured from the waves once the buoy starts to resonate (due to a parametric instability).
  • Figures 22a and 22b respectively illustrate a two-body point absorber with constant area and with variable area relative to wave height and heave.
  • the shape also reduces parametric pitch as the metacentric height change due to incoming waves is reduced.
  • Figures 23a and 23b respectively illustrate a spar platform with an array of heaving buoys with (a) constant area and (b) with variable area.
  • Figures 24a and 24b respectively illustrate a two-body point absorber with one body tethered to the sea floor (a) with constant area and (b) with variable area relative to wave height and heave.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Other Liquid Machine Or Engine Such As Wave Power Use (AREA)

Abstract

Système de conversion d'énergie houlomotrice comportant un absorbeur d'énergie houlomotrice qui, dans une première disposition, est configuré pour réduire la résonance paramétrique qui entraîne un important mouvement de tangage de l'absorbeur d'énergie houlomotrice, et optimiser ainsi le rendement de conversion de puissance. Dans une deuxième disposition, l'absorbeur d'énergie houlomotrice est configuré pour présenter une aire variable traversant l'eau de façon à être soumis à une résonance paramétrique, qui peut être exploitée pour augmenter la puissance captée.
PCT/EP2012/067001 2011-09-02 2012-08-31 Système de conversion d'énergie houlomotrice Ceased WO2013030359A2 (fr)

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CN109911198A (zh) * 2019-03-22 2019-06-21 武汉理工大学 一种波浪能自发电固定翼海基无人机
CN117212034A (zh) * 2023-09-12 2023-12-12 浙江大学 一种可变形的多自由度多稳态波浪能发电装置

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ES2422459A1 (es) * 2013-06-20 2013-09-11 Univ Madrid Politecnica Dispositivo flotante para el aprovechamiento de la energía de las olas, modular y adaptativo
CN114992034B (zh) * 2022-06-21 2024-08-30 中国电建集团华东勘测设计研究院有限公司 基于多时间尺度综合查询的波浪能最大功率点跟踪方法

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EP1036274A1 (fr) 1997-12-03 2000-09-20 William Dick Houlomotrice
EP1295031A1 (fr) 2000-06-16 2003-03-26 Wavebob Limited Houlomotrice

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GB2408075A (en) * 2003-10-16 2005-05-18 Univ Manchester Device for utilising wave energy
US7538445B2 (en) * 2006-05-05 2009-05-26 Sri International Wave powered generation
US8193651B2 (en) * 2009-06-22 2012-06-05 Lightfoot Fred M Method and apparatus for ocean energy conversion, storage and transportation to shore-based distribution centers
GB2473659B (en) * 2009-09-19 2012-04-11 Bruce Gregory Dynamically tuned wave energy conversion system
CN102108933B (zh) * 2011-03-21 2012-11-07 中国水利水电科学研究院 一种参数共振的近岸波能发电系统

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EP1036274A1 (fr) 1997-12-03 2000-09-20 William Dick Houlomotrice
EP1295031A1 (fr) 2000-06-16 2003-03-26 Wavebob Limited Houlomotrice
EP1439306A1 (fr) 2000-06-16 2004-07-21 Wavebob Limited Houlomotrice

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109911198A (zh) * 2019-03-22 2019-06-21 武汉理工大学 一种波浪能自发电固定翼海基无人机
CN117212034A (zh) * 2023-09-12 2023-12-12 浙江大学 一种可变形的多自由度多稳态波浪能发电装置

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GB201115202D0 (en) 2011-10-19

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