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WO-2026093717-A1 - IMPROVEMENTS IN AND RELATING TO FLUID FLOW-DRIVEN GENERATORS

WO2026093717A1WO 2026093717 A1WO2026093717 A1WO 2026093717A1WO-2026093717-A1

Abstract

A fluid flow-driven generator (1) for generating energy from a flow of liquid or gas that comprises a fluid-driven device (3, 4) comprising at least one movable foil (41) that has an adjustable angle of attack, a sensor (24) for sensing a magnitude of a dynamic environmental or structural factor that is indicative of a dynamic load on the fluid-driven device, and a governor (21) for controlling the angle of attack of the foil according to the magnitude of the factor to moderate the drag on the foil in the flow. This allows the ratio of the power coefficient C p of the generator to the drag on the foil to be optimised, increasing the capacity factor of the generator. The fluid-driven device may comprise a fluid-driven flapping mechanism that undergoes reciprocal motion in the flow. Alternatively, or additionally, the governor may be configured to control the amplitude of the reciprocal motion according to the magnitude of the factor. Also disclosed is a passive or semi-passive fluid-driven flapping mechanism that comprises a swing arm (3) having a hydrofoil pivoted on a fulcrum (43) at a distal end (38) thereof, and at least one elevon (42) pivoted to the hydrofoil for movement between two opposite angled states relative to the hydrofoil. An elevon angle control mechanism (50, 55, 80) is arranged to invert the angle of the elevon at the end of each stroke of the swing arm, causing automatic reversal of the pitch of the hydrofoil. The angle of the elevon may be adjusted according to the magnitude of the factor automatically to control the angle of attack of the hydrofoil

Inventors

  • THOMAS, ADRIAN
  • HALL, MARTIN

Assignees

  • Porpoise Power Limited

Dates

Publication Date
20260507
Application Date
20251024
Priority Date
20241102

Claims (20)

  1. 1. A fluid-driven flapping mechanism for a hydropower generator (1) comprising a mounting (75) for fixing the flapping mechanism to a supporting structure (2) that is positioned in or adjacent a body of flowing water (10), a fin (4) having a hydrofoil (41) and at least one elevon (42), a mechanical linkage (3, 35, 43) that is attached at one end (37) to the mounting (75) and at another end (38) to the fin (4) and is configured and arranged to hold the fin (4) in the water when attached to the supporting structure (2) and to permit and constrain movement of the fin (4) relative to the mounting (75) to a reciprocal plunging motion across the direction of the flow (F), and an elevon angle control mechanism (21, 50, 55, 80); the fin (4) being pivoted to the mechanical linkage (3, 35, 43) at a fulcrum (43) such that it can pitch freely about the fulcrum (43) in two opposite directions relative to the direction of the flow (F), the hydrofoil (41) having two opposite surfaces that are each shaped to generate lift (L) in the flow (F) when the fin (4) is pitched in either direction, and the at least one elevon (42) being pivoted to the hydrofoil (41) for movement between two angled states, in each of which angled states the elevon (42) is angled towards a respective opposite surface of the hydrofoil (41); the elevon angle control mechanism (50, 55, 80) being configured to retain the at least one elevon (42) in different respective ones of the angular states during opposite strokes of the flapping mechanism, and to pivot the elevon (42) to the other angled state when the mechanical linkage (3, 35, 43) is moved by the fin (4) in either direction relative to the mounting (75) past an actuation point; the arrangement being such that when the at least one elevon (42) is held in one of its angled states by the elevon angle control mechanism (50, 55, 80) in a flow of water (F), the elevon (42) generates a turning moment on the fin (4), causing the fin (4) to pitch in one direction about the fulcrum (43) until it reaches an equilibrium position in which the resulting lift (L) produced by the hydrofoil (41) generates an equal and opposite turning moment about the fulcrum (43), the lift (L) causing the fin (4) to plunge on the mechanical linkage (3, 35, 43) in one direction relative to the mounting (75), thereby driving motion of the mechanical linkage (3, 35, 43) in the one direction relative to the mounting (75) until it moves beyond the actuation point, whereupon the elevon angle control mechanism (50, 55, 80) pivots the elevon (42) to its other angled state, thereby inverting the pitch of the fin (4) in the flow (F), the resulting lift (L) causing the fin (4) to plunge in the opposite direction relative to the mounting (75); whereby the mechanical linkage (3, 35, 43) is caused to undergo reciprocal motion relative to the mounting (75).
  2. 2. The fluid-driven flapping mechanism of claim 1, comprising a position sensor module, wherein the position sensor module is configured to determine the angle of the mechanical linkage (3, 35, 43) relative to the mounting (75), and wherein in response to a signal from the position sensor module indicating that the mechanical linkage has passed the actuation point, the elevon angle control mechanism (50, 55, 80) is arranged to pivot the elevon (42) from the one angled state to the other angled state. - 47 - A+I Ref: P040773WO
  3. 3. The fluid-driven flapping mechanism of claim 2, wherein the position sensor module comprises an inertial measurement unit (IMU) configured to determine the angle of the mechanical linkage (3, 35, 43) relative to the mounting (75).
  4. 4. The fluid-driven flapping mechanism of claim 2 or claim 3 wherein the position sensor module comprises a rotary encoder configured to determine the angle of the mechanical linkage (3, 35, 43) relative to the mounting (75).
  5. 5. The fluid-driven flapping mechanism of claim 2 wherein the position sensor module comprises a microswitch, the microswitch being arranged to switch when the mechanical linkage (3, 35, 43) passes the actuation point, thereby sending the signal to the elevon angle control mechanism.
  6. 6. The fluid-driven flapping mechanism of claim 5 wherein the position sensor module comprises a pair of microswitches, each microswitch being associated with an actuation point in one direction of the reciprocal motion, and wherein each microswitch is arranged to switch when the mechanical linkage (3, 35, 43) passes the respective actuation point, thereby sending the signal to the elevon angle control mechanism.
  7. 7. The fluid-driven flapping mechanism of claim 6, wherein the mechanism comprises a pair of camming surfaces arranged to rotate with the mechanical linkage (3, 35, 43), and wherein the pair of microswitches are arranged as cam-followers to the camming surfaces, the shape of the camming surfaces defining the actuation points such that as each microswitch passes over the respective camming surface at its respective actuation point, the microswitch sends the signal to the elevon angle control mechanism.
  8. 8. The fluid-driven flapping mechanism of any of claims 2 to 7, wherein the elevon angle control mechanism (50, 55, 80) comprises an electro-mechanical actuator, the electro-mechanical actuator being responsive to the signal from the position sensor module to actuate the elevon.
  9. 9. The fluid-driven flapping mechanism of claim 1, the mechanical linkage (3, 35, 43) being operably connected to the elevon angle control mechanism (50, 55, 80), thereby to operate the elevon angle control mechanism (50, 55, 80) automatically to invert the angle of the at least one elevon (42) when the mechanical linkage (3, 35, 43) moves past the actuation point in either direction, during each stroke of the flapping mechanism.
  10. 10. The fluid-driven flapping mechanism of claim 9, the elevon angle control mechanism (21, 50, 55, 80) incorporating a bistable toggle mechanism (80) that is operably connected between the at least one elevon (42) and the mounting (75) and is arranged to be operated by the mechanical linkage (3, 35, 43); the bistable toggle mechanism (80) defining the actuation point and being configured to switch automatically between first and second stable configurations when it is moved in either direction past the actuation point by the mechanical linkage (3, 35, 43), thereby to pivot the elevon (42) between its angled states. - 48 - A+I Ref: P040773WO
  11. 11. The fluid-driven flapping mechanism of any of claims 1 to 10, further comprising a governor mechanism (25) for controlling the degree of movement of the mechanical linkage (3, 35, 43) relative to the mounting (75) during each stroke before the actuation point is reached, thereby to control the amplitude of each stroke.
  12. 12. The fluid-driven flapping mechanism of any of claims 1 to 10, further comprising a governor mechanism (25) for controlling the maximum angle of the at least one elevon (42) in each angled state during each stroke before the actuation point is reached, thereby to control the angle of attack of the fin (4).
  13. 13. The fluid-driven flapping mechanism of any of claims 1 to 12, the mechanical linkage (3, 35, 43) comprising a swing arm (3) having a hinge assembly (35) at one end (37) for attachment to the mounting (35) and the fin (4) pivoted to the other end (38) thereof.
  14. 14. The fluid-driven flapping mechanism of claim 12, further comprising a sensor (24) for sensing the magnitude of a dynamic environmental or structural factor that is indicative of the load on the flapping mechanism, or the strain in the supporting structure (2) or a positioning system (5, 6) for the supporting structure, when the flapping mechanism is in use; and a governor actuator (22, 23) for operating the governor mechanism (25) according to the sensed magnitude of the dynamic environmental or structural factor.
  15. 15. The fluid-driven flapping mechanism of claim 14, the sensor (24) being adapted and arranged to sense a load in a positioning system (5, 6) for the supporting structure (2), where the supporting structure is a floating vessel or platform.
  16. 16. The fluid-driven flapping mechanism of claim 14 or 15, the governor actuator (22, 23) being configured to operate the governor mechanism (25) to control the amplitude of the plunging motion of the mechanical linkage (3, 35, 43) according to the sensed magnitude of the dynamic environmental or structural factor.
  17. 17. The fluid-driven flapping mechanism of claim 14, claim 15 or claim 16, the governor actuator (22, 23) being configured to operate the governor mechanism (25) to control the maximum angle of attack of the fin (4) according to the sensed magnitude of the dynamic environmental or structural factor.
  18. 18. A hydropower generator (1) comprising the fluid-driven flapping mechanism of any of claims 1 to 17, an electric generator (12) and a power take-off mechanism (31, 32) that is operably connected between the mechanical linkage (3, 35, 43) and the electric generator (12) such that reciprocal motion of the mechanical linkage (3, 35, 43) drives the electric generator (12).
  19. 19. A fluid flow-driven generator (1) for generating energy from a flow of liquid or gas, which fluid flow-driven generator (1) comprises a fluid-driven device (3, 4) comprising a mounting (75) for fixing the - 49 - A+I Ref: P040773WO fluid-driven device (3, 4) to a supporting structure (2) that is positioned in or adjacent a fluid flow (F) and at least one movable fluid foil (41) having an adjustable angle of attack that is configured to be driven by the fluid flow (F); an electric generator (12); a power take-off mechanism (31, 32) that is operably connected between the fluid-driven device (3, 4) and the electric generator (12) such that motion of the fluid-driven device (3, 4) drives the electric generator (12); and a governor (21) being configured and arranged for controlling the angle of attack of the fluid foil (41); the governor (21) comprising a governor mechanism (25) for adjusting the angle of attack of the fluid foil (41), a sensor (24) for sensing a magnitude of a dynamic environmental or structural factor that is indicative of a dynamic load on the fluid-driven device (3, 4), the supporting structure (2), or a positioning system (5, 6) for the supporting structure (2) when the fluid-driven device (3, 4) is in use, and a governor actuator (22, 23) for operating the governor mechanism (25) to reduce the angle of attack of the fluid foil (41) according to the sensed magnitude of the dynamic environmental or structural factor, thereby to moderate the drag on the fluid foil (41) in the fluid flow.
  20. 20. The fluid flow-driven generator (1) of claim 19, the governor actuator (22, 23) being configured to reduce progressively the angle of attack of the fluid foil (41) according to the sensed magnitude of the dynamic environmental or structural factor between a first lower threshold and a second upper threshold; the angle of attack being maximal when the sensed magnitude is below the first lower threshold (T L ) and being minimal when the sensed magnitude is above the second upper.

Description

- 1 - A+I Ref: P040773WO Improvements in and relating to fluid flow-driven generators Field of the Disclosure [0001] The present disclosure provides improvements in and relating to fluid flow-drive generators. More particularly, but not exclusively, the present disclosure relates to hydropower generators of the kind comprising a flapping mechanism that includes a hydrofoil arranged to move back and forth on a mechanical linkage in a flow of water, the mechanical linkage being connected to an electric generator for converting the reciprocal motion of the hydrofoil into electrical energy. Aspects of the present disclosure are also applicable to other fluid flow-driven generators such for example as water and wind turbines. [0002] Background [0003] The conversion of kinetic energy in flowing air or water into electrical energy by rotary turbines or by oscillating wings or sails is well known. Hydropower extracts power from flowing water. The water flow could be due to tides or river currents, or could be the flow past a vessel in motion such, for example, as a sailing or motor yacht. [0004] All hydropower systems generate power by slowing the flow. There is a physical limit (the Betz limit) to the maximal power that can be generated by slowing the flow, because if the flow is stopped completely, no power can be generated. The power available from the flow is: [0006] where Pfiow is the power available from the flow; r is fluid density; S is the area swept by the turbines, wings or sails; and V is the flow velocity. [0007] In a horizontal axis hydropower turbine system such, for example, as a turbine, the flow acts on turbine blades to generate a hydrodynamic force, which rotates the turbine and drives a generator. The magnitude of the hydrodynamic force depends on the twist of the blade, its size, and the angle of attack between the blade and the flow. Meanwhile, a flapping hydropower system uses a fin in the flow to generate hydrodynamic forces and requires a mechanism to adjust the angle of attack of the fin to the flow to generate a flapping motion and thus the forces required to drive the generator. At any instant the force on the fin depends on the flow velocity, the size of the fin and the angle of attack of the fin relative to the flow. Some of the interest in flapping hydropower systems stems from the fact that for the same span and amplitude, a turbine sweeps a circle with TT/4 smaller area than the square swept by a flapping foil, and therefore the available power is lower. [0008] Real hydropower systems are neither optimal nor 100% efficient. Conventionally, inefficiencies are captured in a power-coefficient: - 2 - A+I Ref: P040773WO [0010] The power that can be extracted by slowing the flow thus varies with a power coefficient, Cp, which is a maximum at the Betz limit of 16/27 or 0.59. When the flow passing through the hydropower system is slowed to about one-third of its initial velocity, the power coefficient is maximised. At the time of writing, wind turbines typically slow the flow by only about 0.5-0.7 at rated power, giving Cp= 0.4-0.5. [0011] Prior approaches to flapping hydropower prescribe the kinematics and geometry of the flapping stroke using actuators or mechanical systems to set the angle-of-attack of the fin and the shape of the stroke. These mechanisms require the angle of attack of fin to be specified and controlled throughout the stroke. Many different methods have been developed to control fin angle of attack. [0012] McKinney, W., & DeLaurier, J. (1981). The Wingmill: An oscillating-wing windmill. Journal of Energy, 5(2), 109-115 describe a horizontally mounted wing whose plunging motion is transformed into a rotary shaft motion. The wing is pivoted to pitch at its half-chord location by means of a fitting which, itself, is rigidly attached to a vertical support shaft. Also fixed to the support shaft is an outer sleeve of a push-pull cable whose end pivots on a wing-fixed lever to control the wing's pitch. The up-and-down motion of the support shaft is transformed, through a Scotch-yoke mechanism, into a rotary motion of a horizontal shaft. This shaft, in turn, operates a crank at its far end which actuates the previously mentioned pitch-control cable. Hence the wing's pitching and plunging motions are articulated together at a given frequency and phase angle. The phase angle is controllable while the wingmill is running. [0013] US 7989973 B2 discloses power generation apparatus including a wing-shaped blade having opposite sides, opposite ends and leading and trailing edges extending between those ends. A lift differential producing device in the blade produces a lift differential at the opposite sides of the blade and that device is switched so that one blade side or the other produces the greater lift. A blade shaft extends along an axis in the blade that is in close parallel relation to the leading edge of the blade and that shaft is fixed to move with the blade. Support