FLUID FLOW INDUCED OSCILLATING ENERGY HARVESTER WITH VARIABLE DAMPING BASED UPON OSCILLATION AMPLITUDE

Abstract

An energy harvester including a stand supporting the energy harvester in a fluid flow, i.e. a stream or current; at least one bluff body extending from the stand and positioned substantially perpendicular to the fluid flow, wherein each bluff body moves relative to the stand at least in a direction perpendicular to the fluid flow, wherein sufficient flow causes oscillating movement of the bluff body; and an electrical generator coupled to the stand and coupled to at least one bluff body converting the oscillating movement to electrical power, wherein the rate of electrical power generation per movement of the bluff body (or harvesting) is varied throughout a range of amplitudes of the oscillation of the bluff body and wherein the harvesting rate of at least one amplitude of the body oscillation is greater than the harvesting rate of at least one lower amplitude of the body oscillation.

Claims

1. A fluid flow induced oscillating energy harvester comprising: a stand supporting the energy harvester and configured to support the energy harvester in a fluid flow; at least one bluff body extending from the stand configured to be positioned substantially perpendicular to the direction of fluid flow, wherein each bluff body is mounted for movement relative to the stand at least in a direction perpendicular to the direction of fluid flow, wherein sufficient fluid flow causes an oscillating movement of the bluff body relative to the stand; an electrical generator coupled to at least one bluff body, wherein the electrical generator is configured to convert oscillating movement of the bluff body to electrical power, and wherein the electrical generator is configured such that the rate of electrical power generation per movement of the bluff body is varied throughout a range of amplitudes of the oscillation of the bluff body and wherein a rate of electrical power generation per movement of the bluff body of at least one amplitude of the oscillation of the bluff body is greater than a rate of electrical power generation per movement of the bluff body of at least one lower amplitude of the oscillation of the bluff body.

2. The fluid flow induced oscillating energy harvester according to claim 1 wherein the electrical generator includes coils mounted to the stand and at least one magnet coupled to the at least one bluff body, wherein oscillation of the at least one bluff body will move the at least one magnet relative to the coils.

3. The fluid flow induced oscillating energy harvester according to claim 2 wherein the gap between the magnet and an immediately adjacent coil will vary with the amplitude of the oscillation of the at least one bluff body.

4. The fluid flow induced oscillating energy harvester according to claim 3 wherein the gap between the magnet and an immediately adjacent coil is lower at a higher amplitude of the oscillation of the at least one bluff body than at a lower amplitude of the oscillation of the at least one bluff body.

5. The fluid flow induced oscillating energy harvester according to claim 4 further including a spring supporting the at least one bluff body for oscillation about a rest position.

6. The fluid flow induced oscillating energy harvester according to claim 5 wherein no coils are immediately adjacent the at least one magnet with the bluff body in the rest position.

7. The fluid flow induced oscillating energy harvester according to claim 2 wherein the coil density of coils in the vicinity of the at least one magnet will vary with the amplitude of the oscillation of the at least one bluff body.

8. The fluid flow induced oscillating energy harvester according to claim 2 wherein the coil density of coils in the vicinity of the at least one magnet will increase with the amplitude of the oscillation of the at least one bluff body.

9. The fluid flow induced oscillating energy harvester according to claim 1 wherein the electrical generator includes magnets mounted to the stand and at least one coil coupled to the at least one bluff body, wherein oscillation of the at least one bluff body will move the at least one coil relative to the magnets.

10. The fluid flow induced oscillating energy harvester according to claim 9 wherein the magnet density of magnets in the vicinity of the coil will vary with the amplitude of the oscillation of the at least one bluff body.

11. The fluid flow induced oscillating energy harvester according to claim 9 wherein the magnet density of magnets in the vicinity of the coil will increase with the amplitude of the oscillation of the at least one bluff body.

12. The fluid flow induced oscillating energy harvester according to claim 11 further including a spring supporting the at least one bluff body for oscillation about a rest position.

13. The fluid flow induced oscillating energy harvester according to claim 12 wherein no magnets are immediately adjacent the coil with the bluff body in the rest position.

14. The fluid flow induced oscillating energy harvester according to claim 9 wherein the gap between the coil and an immediately adjacent magnet will vary with the amplitude of the oscillation of the at least one bluff body.

15. The fluid flow induced oscillating energy harvester according to claim 12 wherein the gap between the coil and an immediately adjacent magnet is lower at a higher amplitude of the oscillation of the at least one bluff body than at a lower amplitude of the oscillation of the at least one bluff body.

16. The fluid flow induced oscillating energy harvester according to claim 1 wherein the electrical generator converts oscillation of the at least one bluff body to rotation.

17. The fluid flow induced oscillating energy harvester according to claim 16 wherein the rate of rotation per oscillation displacement is higher at a higher amplitude of the oscillation of the at least one bluff body than at a lower amplitude of the oscillation of the at least one bluff body.

18. A fluid flow induced oscillating energy harvester comprising: a stand supporting the energy harvester and configured to support the energy harvester in a fluid flow; at least one bluff body extending from the stand configured to be positioned substantially perpendicular to the direction of fluid flow, wherein each bluff body is mounted for movement relative to the stand at least in a direction perpendicular to the direction of fluid flow, wherein sufficient fluid flow causes an oscillating movement of the bluff body relative to the stand; an electrical generator coupled to the stand and coupled to at least one bluff body, wherein the electrical generator is configured to convert oscillating movement of the bluff body to electrical power, and wherein the electrical generator is configured such that a harvesting rate is defined as the electrical power generation per movement of the bluff body and wherein the harvesting rate is varied throughout a range of oscillation amplitudes and is lower at small amplitudes than greater amplitudes.

19. The fluid flow induced oscillating energy harvester according to claim 18 further including a spring supporting the at least one bluff body for oscillation about a rest position.

20. The fluid flow induced oscillating energy harvester according to claim 18 wherein the harvesting rate is varied through at least one of i) varying a gap between magnets of the electrical generator and associated coils of the electrical generator, ii) varying the magnet density of the electrical generator at varying amplitudes of the bluff body oscillation; iii) varying the coil density of the electrical generator at varying amplitudes of the bluff body oscillation; and iv) the rate of rotation generated in the electrical generator per oscillation displacement is higher at a higher amplitude of the oscillation of the at least one bluff body than at a lower amplitude of the oscillation of the at least one bluff body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 is a schematic view of a fluid flow induced oscillating energy harvester with variable damping based upon oscillation amplitude according to the present invention;

[0042] FIG. 2A is a schematic view of a fluid flow induced oscillating energy harvester with variable damping based upon oscillation amplitude according to one embodiment of the present invention;

[0043] FIG. 2B is an enlarged schematic view of a stand and an electrical generator of the fluid flow induced oscillating energy harvester of FIG. 2A;

[0044] FIG. 3 is a schematic view of a fluid flow induced oscillating energy harvester with variable damping based upon oscillation amplitude according to another embodiment of the present invention;

[0045] FIGS. 4A and B are schematic views of a stand and an electrical generator of a fluid flow induced oscillating energy harvester with variable damping based upon oscillation amplitude according to another embodiment of the present invention;

[0046] FIG. 5 is a schematic view of a fluid flow induced oscillating energy harvester with variable damping based upon oscillation amplitude according to another embodiment of the present invention;

[0047] FIGS. 6A-C are schematic views of alternative linkage arrangements fluid flow induced oscillating energy harvester with variable damping based upon oscillation amplitude according to further embodiments of the present invention; and

[0048] FIG. 7 is a perspective view of a fluid flow induced oscillating energy harvester formed according to the present invention.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] This invention is directed to a cost effective, efficient, fluid flow induced oscillating energy harvester 10 that maximizes power output and overcomes at least some of the drawbacks of the existing proposed designs. The up and down orientations in the figures is arbitrary. The harvester 10 may be supported in a fluid flow 16 extending vertically upwards generally as viewed in the figures or may be supported downward in the flow 16, such as being suspended from a barge or deck structure on the surface of a river.

[0050] One embodiment of the energy harvester 10 of the present invention is shown in FIGS. 1 and 2A and B and 7. The currently proposed oscillating energy harvester 10 includes a stand 12 supporting the oscillating energy harvester 10 in a fluid stream or current 16, such as a river bed. The stand 12 may also be called a base, a housing, a support and/or a piling. The construction of the stand 12, such as the shape shown in FIG. 7, is generally known in the art and need not be described in detail herein.

[0051] The stand 12 supports at least one, and generally a plurality of spaced bluff bodies 14. Each bluff body 14 may also be referenced as a prism or a beam. In the preferred embodiment each bluff body 14 is extending from the stand 12 in a cantilevered fashion as shown in FIG. 1 or 7. Further FIG. 7 shows a pair of bodies 14 extending from the side of the stand 12, which may be more common arrangement while the remaining figures suggest a placement of the bodies 14 above the stand 12 mainly to simplify the schematic illustration of the components of the harvester 10. Both arrangements are possible, as is suspending the bodies 14 below the stand 12 where the stand 12 is mounted above the primary flow 16, such as to a floating platform or barge and which surface location may represent a simpler easier location for the electrical generator and associated elements. Alternatively, each bluff body 14 may be supported between a pair of stands 12 at opposed ends thereof, however the cantilevered arrangement shown in FIGS. 1 and 7 is believed to be more economical. Each bluff body 14 is configured to be positioned substantially perpendicular to the direction of fluid flow (shown at 16). The particular construction of the bluff bodies 14 is believed to be known to those of ordinary skill in the art and the shape and surface of the bluff body 14 may be optimized for maximizing oscillation.

[0052] In the harvester 10, each bluff body 14 is mounted for movement relative to the stand 12 at least in a direction perpendicular to the direction of fluid flow 16. As shown each bluff body 14 is coupled to a support 18 which extends into the stand 12 to an electrical generator 20 within the stand 12. The support member 18 may take a number of forms and can include several elements, but can be generally described as the coupling between the moveable elements of the electrical generator 20 and the oscillating bluff bodies 14. The schematic figures form a representational image of the function of the support member 18. Conventional bearing, packing and sealing structures 22 can maintain and restrict the movement of the support 18 and associated bluff body 14 to a constrained oscillation motion. The details of constructing the support 18 and the bearing, packing and sealing structures 22 are generally known in the art. The form of the sealing structures 22 is dictated by the particulars of the support member 18.

[0053] Oscillation of the bluff body 14 is driven by fluid flow 16 past the bluff body 14, wherein sufficient fluid flow 16 causes an oscillating movement of the bluff body 14 relative to the stand 12. The oscillating support 18 and bluff body 14 is suspended or supported by a spring 24. The spring 24 establishes a zero-displacement or rest position. If there is no flow, the structure formed of support 18 portion of the electrical generator 20 coupled thereto and body 14 will rest at this position and when there is sufficient flow, the structure will oscillate about this rest position.

[0054] Harvesting electrical power in the harvester 10 damps the motion of the oscillating structure. At lower flow rates, it is possible to prevent oscillation if too much damping is imposed (i.e. if the rate of power generation per movement of the structure is too high), however, at higher flow rates, there is more energy available to harvest, so a higher rate of harvesting is desirable. Since the oscillation amplitude of the bluff body 14 varies with the flow rate 16, harvesting rates that varies with the flow rate 16 can be achieved in a simple, cost effective, passive design in the energy harvester 10 by varying the rate of harvesting with the position of the oscillating structure.

[0055] In other words, the electrical generator 20 is configured such that the rate of electrical power generation per movement of the bluff body 14 (i.e. the harvesting rate) is varied throughout a range of amplitudes of the oscillation of the bluff body 14 and wherein a rate of electrical power generation per movement of the bluff body 14 of at least one amplitude of the oscillation of the bluff body 14 is greater than a rate of electrical power generation per movement of the bluff body 14 of at least one lower amplitude of the oscillation of the bluff body 14.

[0056] FIG. 2A is a schematic view of a fluid flow induced oscillating energy harvester 10 with variable damping based upon oscillation amplitude according to one embodiment of the present invention and FIG. 2B is an enlarged schematic view of a stand 12 and an electrical generator 20 of the fluid flow induced oscillating energy harvester 10 of FIG. 2A. In this embodiment of the invention the electrical generator 20 includes coils 26 mounted to the stand 12 and a magnet 28 (a plurality of magnets 28 may be implemented) coupled to the support 18 of the associated bluff body 12, wherein oscillation of the bluff body 12 will move the magnet 28 relative to the coils 26 to generate electricity in generator 20 in a manner generally known in the art.

[0057] The embodiment of FIGS. 2A and 2B the gap between coils 26 and magnet 14 varies with the amplitude of the oscillation of the body 14 in this linear generator. Near the zero-displacement or rest point, the gap would be large and for higher displacements the gap could be smaller. In other words the gap between the magnet 28 and an immediately adjacent coil 26 will vary with the amplitude of the oscillation of the at least one bluff body 14. The phrase “immediately adjacent coil 26” in this context will be the coils 26 that are the same vertical height/horizontal level of the magnet 28 (assuming the stand 12 is positioned vertically). With this configuration the gap between the magnet 14 and an immediately adjacent coil 26 is lower at a higher amplitude of the oscillation of the bluff body 14 than at a lower amplitudes of the oscillation of the at least one bluff body 14 as generally shown. The fluid flow induced oscillating energy harvester 10 as shown in FIGS. 2A and B may be provided such that there are no coils 26 immediately adjacent the magnet 28 with the bluff body 14 in the rest position.

[0058] It is possible to reverse the position of the coils 26 and the magnets 28 in the embodiment of FIGS. 2A and B such that one or more coils 26 are carried on the support 18 and a plurality of magnets 28 are coupled to the stand 12 and wherein the gap between the coil 26 mounted to the support 18 and an immediately adjacent magnet 28 mounted to the inside of the stand 12 will vary with the amplitude of the oscillation of the at least one bluff body 14. Specifically, the gap between the coil 26 mounted to the support 18 and an immediately adjacent magnet 14 mounted to the inside of the stand 12 is lower at a higher amplitude of the oscillation of the at least one bluff body 14 than at a lower amplitude of the oscillation of the at least one bluff body 14.

[0059] FIG. 3 is a schematic view of a fluid flow induced oscillating energy harvester 10 with variable damping based upon oscillation amplitude according to another embodiment of the present invention. As with the described inverse of the embodiment of FIGS. 2A and B, this embodiment provides wherein the electrical generator 10 includes magnets 28 mounted to the inside of the stand 12 and at least one coil 26 coupled to the support 18 of the at least one bluff body 14, wherein oscillation of the at least one bluff body 14 will move the at least one coil 26 relative to the magnets 28 to generate electricity via generator 20. In this embodiment the gap between coil 26 and adjacent magnets 28 is constant. In this embodiment the distribution of the magnets 28, also called herein the density of the magnets 28, varies with height as shown here. No magnets 28 are placed near the zero displacement or rest point and the magnet density increases at higher amplitudes, as shown thereby increasing the harvesting rate at higher amplitudes.

[0060] As with the embodiment of FIGS. 2A and B, it is possible to reverse the respective position of the coils 26 and magnets 28 in the embodiment of FIG. 3 such that the coils 26 are coupled to the stand 12 and the magnet 14 is coupled to the support 12 and wherein the coil density of coils (via more coils 26 per length of stand 12) attached to the stand 12 in the vicinity of the magnet 14 will increase with the amplitude of the oscillation of the at least one bluff body 14.

[0061] FIGS. 4A and B are schematic views of a stand 12 and an rotary electrical generator 20 (represented by dual pinions 32 and 34) of a fluid flow induced oscillating energy harvester 10 with variable damping based upon oscillation amplitude according to another embodiment of the present invention in which the electrical generator 20 converts oscillation of the at least one bluff body to rotation via pinions 32 and 34 which are coupled to a rotor of a rotor-stator (not shown) generator. The specifics of the rotary generator 20 are well known and need not be described in detail herein.

[0062] In the embodiment of FIGS. 4A and B, a dual rack 36 and 38 is attached to the support 18 of the oscillating structure and meshes with and drives respective pinions 32 and 34 that would in turn drive the rotary generator 20, for example. In this form, when the oscillation is near the zero-displacement or rest point, the rotary generator 20 would turn few revolutions per length of travel (via large pinion 32 and associated engaged rack 36) and relatively many revolutions per length of travel (via smaller pinion 34 and associated engaged rack 38) at higher displacements. In other words, the rack 36 engages the larger diameter pinion 32 to drive the generator near the zero-displacement position and at larger displacements, rack(s) 38 could engage smaller diameter pinion 34, achieving a higher generator rotation per length of oscillator movement. It should be apparent that more than two rates of harvesting may be provided and the schematic figures are merely for illustration.

[0063] It is apparent that many variations to the present invention may be made without departing from the spirit and scope of the invention. For example, FIG. 5 is a schematic view of a fluid flow induced oscillating energy harvester 10 with variable damping based upon oscillation amplitude according to another embodiment of the present invention in which a rack 36 is mounted to a linkage 42 coupled to the support 18 and meshes with a pinion 32 driving a rotary generator with the pinion 32 mounted on a separate linkage 44 coupled to the stand 12. The compound motion of the support 18 and the linkages 42 and 44 provides for the variable harvesting rate. Specifically as the amplitude of the motion of the body 14 increases the motion of the rack 36 relative to the pinion 32 increases thereby increasing the rotation rate of the pinion 32.

[0064] FIGS. 6A and B are schematic views of a fluid flow induced oscillating energy harvester 10 with variable damping based upon oscillation amplitude according to further embodiments of the present invention. In FIG. 6A the support 18 is replaced with a four bar linkage 46 and the rotary generator 20 is moved outside of the stand 12 to a position between the four bar linkage 46 as shown using the linkages 42 and 44 similar to FIG. 5. Analogous to FIG. 5 the compound motion of the four bar linkage 46 and the linkages 42 and 44 provides for the variable harvesting rate. Specifically as the amplitude of the motion of the body 14 increases the motion of the rack 36 relative to the pinion 32 increases thus increasing the rotation rate of the pinion 32. The spring 24 can be replaced with torsional springs to maintain the rest position of the body 14.

[0065] FIG. 6B is analogous to the embodiment of FIG. 6A except the four bar linkage 46 is replaced with a Peaucellier-Lipkin linkage 48, wherein the compound motion of the Peaucellier-Lipkin linkage 48, and the linkages 42 and 44 provides for the variable harvesting rate. Specifically as the amplitude of the motion of the body 14 increases the motion of the rack 36 relative to the pinion 32 increases thus increasing the rotation of the pinion 32. FIG. 6C shows an alternative harvester 10 linkage arrangements (with the generator removed for clarity) that may be more applicable for a suspended harvester 10 described herein and is merely illustrating further linkage possibilities.

[0066] It should be apparent that other alternatives are possible within the spirit and scope of the present invention. The present invention is defined by the appended claims and equivalents thereto.