WO2013188397A1

WO2013188397A1 - Linear array of wave-energy converters

Info

Publication number: WO2013188397A1
Application number: PCT/US2013/045170
Authority: WO
Inventors: Allan Chertok; Arthur R. Williams; P. William Staby
Original assignee: Resolute Marine Energy, Inc.
Priority date: 2012-06-12
Filing date: 2013-06-11
Publication date: 2013-12-19

Abstract

A linear array of component wave-energy converters includes at least two component oscillating wave surge converters. Each component oscillating wave surge converter includes a paddle and a hinge configured to attach the paddle to a stationary "" surface. The component oscillating wave surge converters are arranged in an end-to-end configuration with a narrow, vertical region separating vertical edges of adjacent component oscillating wave surge converters. Efficiency-reducing flow through this vertical region is minimized both by minimization of the vertical region's size and by paddle shapes that direct flow away from the region. Component wave-energy converters can oscillate with different phases and frequencies.

Description

LINEAR ARRAY OF WAVE-ENERGY CONVERTERS

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 61/658,718, filed June 12, 2012, entitled "LINEAR WAVE ENERGY CONVERTER ARRAYS", which is hereby incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

[0002] The present application relates to wave-energy converters. More specifically, the application refers to linear arrays of wave-energy converters for capturing energy carried by waves propagating at a surface of large bodies of water and converting the captured energy into a form more convenient for storage and/or consumption.

[0003] Wave-energy-conversion devices can be segregated into two groups: those that capture the vertical component of the water motion, and those that capture the horizontal or surge component of the water motion. One technology used to capture the horizontal or surge component of the water motion is an oscillating wave surge converter. An example of the fundamental structure and components of an oscillating wave surge converter 10 are illustrated schematically in Fig. 1, which shows a paddle 11 that is attached to a stationary surface 12 via a hinge 13. For example, the stationary surface 12 may be the sea bed or a nominally stationary platform disposed in a body of fluid below the depth at which local water motion associated with surface wave action becomes negligible. The oscillating wave surge converter 10 extends into the plane of Fig. 1.

[0004] The vertical edges of an oscillating wave surge converter represent potential escape routes for water particles that allow the water particles to avoid imparting their energy to the paddle. Figure 2 shows the dramatic efficiency losses thereby implied for narrow oscillating wave surge converter paddles for which water escaping around the vertical edges of the paddle is a dominant effect. With increasing paddle width, these edge losses become relatively less important, and efficiency ultimately approaches a constant value. The data shown in Fig. 2 are presented in a report entitled "Advances in the Design of the Oyster Wave Energy Converter" by Henry, K. Doherty, Cameron, Whittaker and R. Doherty, the contents of which are incorporated herein by reference in its entirety. The fact that efficiency approaches zero with decreasing paddle width is discussed by Whittaker and Folley in Phil. Trans. R. Soc. A 2012 370, 345-364, the contents of which are incorporated herein by reference in its entirety.

[0005] Efficiency data Eff(w) are well described by a simple exponential dependence on paddle width w according to the following Equation 1 :

Eff(w) = Eff(∞) [1 - exp(-w/w_edges)] Equation 1, where Eff(∞) is the efficiency of an infinitely wide paddle and w_edges is the width of the two edge regions along the vertical edges of the oscillating wave surge converter paddle. Equation 1 indicates that surge-converter paddles narrower than Wedges will not be very efficient. The data shown in Fig. 1 indicate that, for this data, W_edge ~9m. The exponential efficiency loss due to edge losses shown in Fig. 2 indicates that the efficiency of end-to-end oscillating wave surge converter arrays can be significantly improved by reducing or effectively eliminating escape routes created by spaces between the vertical edges of adjacent paddles. The data in Fig. 2 are for oscillating wave surge converters with paddle heights greater than the water depth, and thus focus on efficiency losses associated with the vertical edges of the paddle.

[0006] A need exists for a linear arrays of wave-energy converters that minimize or eliminate conversion-efficiency losses caused by fluid flow through a space between adjacent vertical edges of individual oscillating wave surge converters . The embodiments of the present invention substantially fulfill these needs.

SUMMARY OF THE INVENTION

[0007] An embodiment of the invention is directed to a linear array of component wave-energy converters comprising at least two component oscillating- wave-surge converters. Each component oscillating wave surge converter comprises a paddle and a hinge configured to attach the paddle to a stationary surface. The component oscillating wave surge converters are arranged in an end-to-end configuration with a narrow, vertical region separating vertical edges of adjacent component oscillating wave surge converters.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate preferred embodiments of the invention and together with the description serve to explain principles of the invention.

[0009] Fig. 1 illustrates a conventional oscillating wave surge converter device including a paddle, a hinge and a stationary surface to which the paddle is attached.

[0010] Fig. 2 graphically illustrates exponential efficiency loss caused by fluid flow around vertical edges of the paddle of Fig. 1.

[0011] Fig. 3 illustrates a schematic frontal view of (a) a single oscillating wave surge

converter, as shown in Fig. 1 , and (b) an end-to-end linear array of such oscillating wave surge converters.

[0012] Figs. 4(a) and 4(b) illustrate a schematic top view of the paddles of adjacent oscillating wave surge converters in an end-to-end array of oscillating wave surge converters and the paddle motion of adjacent oscillating wave surge converters relative to each other.

[0013] Fig. 5 illustrates a schematic top view of the paddles of two adjacent oscillating wave surge converters in an end-to-end array of oscillating wave surge converters, as in Fig. 3(b), the paddles having a concave shape.

[0014] Fig. 6 illustrates a schematic top view of the paddles of two adjacent oscillating wave surge converters in an end-to-end array of oscillating wave surge converters, as shown in Fig. 3(b), where adjacent vertical edges of adjacent paddles are joined by a barrier comprised of elastic material.

[0015] Fig. 7 illustrates a schematic edge view of an oscillating wave surge converter device of an embodiment in which a single power take-off axle rotates in two directions as the paddle oscillates in response to waves.

[0016] Fig.8 illustrates a schematic edge view of an oscillating wave surge converter device of an embodiment in which two power take-off axles each rotate in a single direction.

[0017] Fig.9 illustrates a schematic edge view of an oscillating wave surge converter device of an embodiment in which a single power take-off axle rotates in a single direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Referring now to Figs. 1 and 3, a principal attribute of a wave-energy-capture device, in particular, an oscillating wave surge converter, is the surface area it presents to local fluid (e.g., water) particle motion concomitant with surface-wave propagation on large bodies of the fluid (e.g., the ocean). Although water is used as the primary example of the fluid throughout the specification, one of ordinary skill in the art will appreciate that the linear array of wave-energy converters described herein may be used in other fluids.

[0019] Referring now to Fig. 3(a), an oscillating wave surge converter 100 includes a paddle 101 that is attached to a stationary surface 102 via a hinge 103. For example, the stationary surface 102 may be the sea bed or a nominally stationary platform disposed in a body of fluid. The fluid may be, for example, water. The oscillating wave surge converter 100 may further include a power take-off unit 104 that may be any known, conventional power take-off unit, have a power take-off axle 104A. As illustrated in Fig. 3(b), in a preferred embodiment, a plurality of oscillating wave surge converters 100 may be arranged in an end-to-end configuration with a vertical region 105 separating vertical edges 106 of adjacent oscillating wave surge converters 100. Although the specification and figures discuss two adjacent oscillating wave surge converters 100, one of ordinary skill in the art will appreciate that any number of oscillating wave surge converters 100 may be arranged in an end-to-end configuration. The number and size of the paddles may depend on, for example, factors such as capacity, performance, manufacturing availability, transport consideration and deployment options. In addition, the paddles 101 must be substantially parallel so that the adjacent paddles 101 do not collide.

[0020] The paddle 101 oscillates about the hinge 103 in response to sub-surface fluid-particle motions concomitant with approaching surface waves. The power take-off unit 104 is configured to convert paddle oscillations into a more useful form of energy, such as electrical power or pressurized fluid flow. The amount of energy captured by an oscillating wave surge converter 100 depends primarily on an area of paddle 101, that is, the product of a height of the paddle 101 and a width of the paddle 101. Paddle height is limited by a depth of the fluid and by allowances for stresses that may occur during violent weather. Paddle length is limited by phase coherence within each wave and by deviations in wave angle of incidence from normal. To increase the amount of energy captured by the oscillating wave surge converter 100 and minimize efficiency losses that would occur if the paddles 101 were widely separated, a nominally horizontal width of the paddle 101 is increased, as illustrated by Fig. 3b, by combining two or more oscillating wave surge converters 100 in a substantially end-to-end configuration.

[0021] For nominally planar oscillating wave surge converter paddles 101, multiphase paddle motion opens up a vertical region 105, illustrated in Fig. 4a, between the vertical edges 106 of adjacent paddles 101 through which water can escape. In some embodiments, the vertical region 105 is substantially triangular in shape. A simple and straightforward way to minimize fluid flow through the vertical region 105 between adjacent paddles 101 is to minimize the separation between adjacent paddles 101 by narrowing the vertical region 105. In one embodiment, this is accomplished by rigidly attaching adjacent paddles 101 are rigidly attached to a common structural element, such as an axle 104A. Rigid attachment to a common structural element forces adjacent paddles 101 to oscillate with the same frequency and same phase.

[0022] In other embodiments, the paddles 101 of adjacent oscillating wave surge converts 100 may move out of phase and/or with different frequencies. Out-of-phase motion of adjacent paddles 101 reduces and may eliminate losses due to phase coherence along a single, wide paddle 101. In addition, out-of-phase motion of the individual paddles 101 of the oscillating wave surge converters 100 improves the efficiency with which the oscillating wave surge converter 100 captures waves that approach from different directions.

[0023] A structure of the paddle 101 may be altered to minimize the flow of water between adjacent paddles 101, namely within the vertical region 105. For example, fluid escape through the vertical region 105 may be reduced by including paddle terminations 107 as illustrated in Figs. 4(b) and 5. The paddle terminations 107 may be disposed perpendicular to the paddle 101, along a vertical edge 106 the paddle 101. The paddle termination 107 may be, for example, a planar wall (see Fig. 4(b)) or a curved or angular wall (see Fig. 5) configured to guide fluid away from the vertical region 105, thereby producing less turbulence.

[0024] In one embodiment, as illustrated in Fig. 6, adjacent paddles 101 are connected by a material 108 configured to block a passage of fluid between adjacent paddles 101 through the vertical region 105. The material 108 may be, for example, an elastic material. To the extent that the material 108 is elastic and allows out-of-phase motion of adjacent paddles 101, one of ordinary skill in the art will appreciate that the magnitude of the out-of-phase paddle motion is limited by the elasticity of the material 108.

[0025] Wave power captured by individual oscillating wave surge converter paddles 101 is aggregated and converted into more convenient forms of power, such as electricity or pressurized fluid flow by a power takeoff (PTO) subsystem. Numerous options are available for this PTO functionality, including linear-displacement pumps, rotational pumps and electric generators. In one embodiment, for example, the power-takeoff subsystem includes a hydraulic piston configured to attach the paddle of the oscillating wave surge converter to the stationary surface to produce a pressurized fluid flow.

[0026] The motion of the paddle 101 of the oscillating wave surge converter 100 is

fundamentally oscillatory, and thus, changes direction. Out-of-phase paddle motion can therefore include motion in opposite directions. In applications in which out-of-phase paddle motion is not required, paddles 101 of adjacent oscillating wave surge converters 100 can be locked onto a common power take-off axle 109 as illustrated in Fig. 7. The power take-off axle 109 rotates in two directions as the paddles 101 oscillate in response to waves. In other words, the power take-off axle 109 is a bidirectional power take-off axle.

[0027] In order to reap the benefits of out-of-phase paddle motion, the paddle 101 can be ratchet attached to at least two common power take-off axles 110, as illustrated in Fig. 8.

Figures 8 and 9 illustrate cable-based PTOs in which a cable attached to the oscillating paddle is wound around a drum 114, thereby converting the paddle motion into rotation of the drum 114 about its axis. The drum 114 may drive an electric generator or fluid pump. Ratchet attachment can be achieved using, for example, a Sprag clutch. As seen in Fig. 8, cables 111 are attached to the power take-off axles 110 only when they are in tension, and therefore, drive the power takeoff axles 110 in a single direction. In other words, the power take-off axle 110 is a unidirectional axle. In such a configuration, the paddles 101 of multiple oscillating wave surge converters 100 can drive the at least two power take-off axles 110 shared by adjacent oscillating wave surge converters 100 without working against one another. Embodiments in which the captured power is aggregated by combining the output of power take-off axles 110 associated with individual oscillating wave surge converters 100 allow the strength and rated capacity of component oscillating wave surge converters 100 to be independent of the width of the end-to-end array. In Fig. 8, each PTO drum 1 14 and axle 110 are used nominally half the time, that is, during that portion of the wave-oscillation period in which the paddle 101 moves away from the drum 114 and axle 110, putting the cable 111 in tension.

[0028] As illustrated in Fig. 9, power delivered can be aggregated, using pulleys 112, to a single, common power take-off axle 113. Figure 9 shows that pulleys 112 can be used to redirect cables 111 attached to opposite sides of the paddle 101 to drums 114 coaxially mounted on a common axle. In this way torque is applied to the PTO axle during most of the wave- oscillation period. [0029] According to the embodiments described herein, a linear array of wave-energy converters may include the construction and use of an arbitrarily long array of oscillating wave surge converters in which individual paddles oscillate with either the same or differing frequencies and phases. Efficiency losses due to wave phase coherence, off-normal incidence and turbulence at the vertical edges of the paddles are minimized by array and paddle structures, for example, paddle terminations, configured to minimize fluid flow between adjacent paddles. According to the configurations of the linear array of wave-energy converters described herein, an effectively large area comprising multiple component oscillating wave surge converters may be covered, without significant losses associated with fluid flows around the vertical edges of the component oscillating wave surge converters.

[0030] The benefits of the embodiments of end-to-end arrays of oscillating wave surge converters disclosed here include potential elimination of the exponential wave-energy-capture losses associated with fluid flow around the vertical edges of oscillating wave surge converter paddles. In addition, the array may cover a large area that remains sufficiently below the water surface to avoid excessive loading caused by violent weather. Aggregate wave energy captured by the array can be consolidated at a power take-off axle, power take-off device and power takeoff output levels. Namely, different embodiments may share different power take-off functions and structure, such as axles, power conversion subsystems and even entire power take-offs. Moreover, fluctuations in the power produced are reduced by the freedom of individual oscillating wave surge converts to oscillate out of phrase and at different frequencies.

[0031] It is to be understood that both the foregoing general description and detailed description are exemplary and explanatory only, and are not restrictive of the invention.

[0032] For purposes of this disclosure, the term "attached" means the joining of two components (electrical or mechanical) directly or indirectly to one another. Such joining may be stationary in nature or movable in nature. Such joining may be achieved with the two components (electrical or mechanical) and any additional intermediate members being integrally formed as a single unitary body with one another or with the two components or the two components and any additional member being attached to one another. Such joining may be permanent in nature or alternatively may be removable or releasable in nature.

[0033] The construction and arrangement of the linear arrays of wave-energy converters as shown in the preferred and other exemplary embodiments is illustrative only. Although only a few embodiments of the present airbag assembly have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g. variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in this disclosure. Accordingly, all such modifications attainable by one versed in the art from the present disclosure within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the preferred and other exemplary embodiments without departing from the spirit of the present application.

Claims

WHAT IS CLAIMED IS:

1. A linear array of component wave-energy converters comprising:

at least two component oscillating wave surge converters, each component oscillating wave surge converter comprising a paddle and a hinge configured to attach the paddle to a stationary surface,

wherein the component oscillating wave surge converters are arranged in an end- to-end configuration comprising a narrow, vertical region separating the vertical edges of adjacent component oscillating wave surge converters.

2. The linear array of component wave-energy converters of claim 1, wherein a passage of fluid between adjacent component oscillating wave surge converters is minimized by minimizing a width of the vertical region separating adjacent component oscillating wave surge converters.

3. The linear array of component wave-energy converters of claim 1, wherein each component oscillating wave surge converter further comprises paddle terminations disposed perpendicular to the paddle, along a vertical edge of the paddle, the paddle terminations of adjacent component oscillating wave surge converters configured to minimize a passage of fluid through the vertical region separating adjacent component oscillating wave surge converters.

4. The linear array of component wave-energy converters of claim 3, wherein a paddle termination comprises a curved or angled surface configured to direct fluid flow away from the narrow vertical region separating adjacent component oscillating wave surge converters.

5. The linear array of component wave-energy converters of claim 1, wherein a single power take-off unit converts wave power captured by multiple component oscillating wave surge converters.

6. The linear array of component wave-energy converters of claim 1, wherein the paddles of different component oscillating wave surge converters move with a common frequency and a common phase.

7. The linear array of component wave-energy converters of claim 1, wherein the paddles of multiple component oscillating wave surge converters are rigidly attached to a common axle.

8. The linear array of component wave-energy converters of claim 1, wherein the paddles of different component oscillating wave surge converters move with different frequencies.

9. The linear array of component wave-energy converters of claim 1, wherein the paddles of different component oscillating wave surge converters move with different phases.

10. The linear array of component wave-energy converters of claim 1, wherein the paddles of component oscillating wave surge converters are each ratchet attached to two power take-off axles that are shared by multiple component oscillating wave surge converters.

11. The linear array of component wave-energy converters of claim 1, wherein the paddles of component oscillating wave surge converters are ratchet attached to a common power take-off axle that is shared by multiple component oscillating wave surge converters.

12. The linear array of component wave-energy converters of claim 1, wherein each component oscillating wave surge converter is equipped with a power take-off unit.

13. The linear array of component wave-energy converters of claim 12, wherein the power take-off unit is configured to convert paddle motion into electrical power.

14. The linear array of component wave-energy converters of claim 12, wherein the power take-off unit is configured to convert paddle motion into pressurized fluid flow.

15. The linear array of component wave-energy converters of claim 12, wherein rotary motion of the paddle about its hinge powers the power take-off unit.

16. The linear array of component wave-energy converters of claim 14, wherein the power-takeoff unit comprises a hydraulic piston configured to attach the paddle of the component oscillating wave surge converter to the stationary surface to produce the pressurized fluid flow.

17. The linear array of component wave-energy converters of claim 1, wherein adjacent paddles in the array are connected by a material configured to block a passage of fluid between adjacent paddles.

18. The linear array of component wave-energy converters of claim 17, wherein the material connecting adjacent paddles is elastic and configured to enable motion of adjacent paddles, relative to each other.