ELECTRICAL POWER GENERATOR AND AN ELECTRICAL POWER GENERATION METHOD

Abstract

An electrical power generator includes a first part configured to be located in a fluid such that, when the fluid moves, it generates vortices in the fluid so that a lift force is generated on the first part, which produces an oscillating movement of the first part, which has an amplitude. The natural oscillation frequency of the first part may be adjusted to wind speed by way of magnets, which repel each other. Magnets may also be used to generate electrical currents in coils. The first part can have a diameter that increases with distance above the base of the generator.

Claims

1. An electrical power generator, comprising: a first part configured to be anchored in an anchoring point such that the first part can perform a swaying motion relative to the anchoring point, the first part being configured to be located in a fluid and configured such that, when said fluid moves, it generates vortices in the fluid, so that a lift force is generated on the first part, which produces an oscillating and swaying movement of the first part relative to the anchoring point, said oscillating movement having an amplitude; and a second part that surrounds, at least partially, said first part; the generator comprising a system for generating a magnetic field which produces a magnetic repulsion force between the first part and the second part, which varies with the oscillating movement of the first part and which has a maximum value that increases when the amplitude of the oscillating movement of the first part increases.

2. The generator of claim 1, wherein the system for generating a magnetic field comprises at least one first magnet associated to the first part and at least one second magnet associated to the second part, said at least one first magnet and said at least one second magnet being arranged in such a way that they repel each other and in such a way that when the oscillating movement of the first part is produced, the distance between said at least one first magnet and said at least one second magnet varies according to said oscillating movement.

3. The generator according to claim 2, wherein said at least one first magnet comprises at least two diametrically opposed parts, and wherein said at least one second magnet comprises at least two diametrically opposed parts facing said at least two diametrically opposed parts of said at least one first magnet.

4. The generator according to claim 3, wherein said at least one first magnet is configured as at least one ring.

5. The generator according to claim 3, wherein said at least one second magnet is configured as at least one ring.

6. The generator according to claim 2, wherein said at least one first magnet comprises a plurality of magnets arranged at different heights above a base of the generator and wherein said at least one second magnet comprises a plurality of magnets arranged at different heights above the base of the generator.

7. The generator according to claim 2, wherein said at least one first magnet comprises a first plurality of magnets arranged substantially adjacent to each other and with polarities arranged so that the magnetic field produced by said first plurality of magnets is stronger on a side of said magnets facing said at least one second magnet than on an opposite side, or wherein said at least one second magnet comprises a second plurality of magnets arranged substantially adjacent to each other and with polarities arranged so that the magnetic field produced by said second plurality of magnets is stronger on a side facing said at least one first magnet than on an opposite side.

8. The generator according to claim 2, wherein the at least one first magnet and the at least one second magnet are arranged in an inclined manner in relation to a longitudinal axis of the first part.

9. The generator according to claim 1, wherein the first part is arranged so that the amplitude of the oscillating movement increases with the velocity of the fluid, at least within a certain range of velocities.

10. The generator according to claim 2, wherein the repulsion force between the at least one first magnet and the at least one second magnet is inversely proportional to the square of the distance between the first magnet and the second magnet, and wherein, when the speed of the fluid increases, the amplitude of the oscillating movement tends to increase, whereby the magnets tend to get closer during a part of maximum approach of each oscillation cycle, whereby the maximum repulsion force produced between the at least one first magnet and the at least one second magnet in each oscillation cycle increases accordingly, whereby the increase of the repulsion force increases the resonance frequency of the first part, whereby the structure of the generator contributes to an automatic increase in the resonance frequency of the first part when the speed of the fluid increases, and vice-versa.

11. The generator according to claim 2, comprising a subsystem of magnets and at least one coil, the generator being configured such that the oscillatory movement of the first part produces a relative displacement between the subsystem of magnets and the at least one coil, such that an electromotive force is generated in said at least one coil.

12. The generator according to claim 11, the subsystem of magnets comprising a plurality of magnets, arranged such that when the first part moves during the oscillatory movement from a neutral position to an extreme tilted position, said at least one coil is subjected to at least one change of direction of magnetic field.

13. (canceled)

14. The generator according to claim 11, the coils being arranged on the second part and the subsystem of magnets being arranged on the first part.

15. The generator according to claim 11, comprising a generator subsystem comprising a first generator module and a second generator module moveable in relation to said first generator module in parallel with a longitudinal axis of the first part, to produce the relative displacement between the subsystem of magnets and the at least one coil.

16.-28. (canceled)

29. The generator according to claim 15, arranged so that as a result of the oscillating movement of the first part, an oscillating movement of the second generator module is produced, the oscillating movement of the second generator module being in a direction parallel with the longitudinal axis of the first part and having a frequency higher than the frequency of the oscillating movement of the first part.

30. (canceled)

31. The generator according to claim 11, wherein the second part comprises a first generator module and a second generator module moveable in relation to the first generator module to produce the relative displacement between the subsystem of magnets and the at least one coil, wherein the second generator module is suspended so that it can oscillate in relation to the first generator module, at a frequency different from the frequency of the oscillating movement of the first part.

32.-37. (canceled)

38. The generator according to claim 1, wherein the first part comprises an oscillating pole and wherein the second part comprises a static structure located in correspondence with the base of the pole.

39. A method for making an electrical power generator tune with wind speed, the electrical power generator comprising: a first part anchored to an anchoring point and configured to be located in a fluid and configured such that when said fluid moves, it generates vortices in said fluid, so that a lift force is generated on the first part, which produces an oscillating and swaying movement of the first part relative to the anchoring point, and a second part which surrounds, at least partially, said first part; the method comprising the step of arranging at least one first magnet on the first part and at least one second magnet on the second part, such that said at least one first magnet and said at least one second magnet repel each other.

40.-41. (canceled)

42. The generator according to claim 1, wherein the first part comprises a substantially rigid part and another substantially flexible and elastic part to be anchored in the anchoring point, such that, given the flexibility and elasticity of the substantially flexible and elastic part, the first part can perform a swaying motion relative to the anchoring point.

43. The generator according to claim 12, wherein the subsystem of magnets includes the at least one first magnet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0069] To complement the description and to better understand the features of the disclosure, in accordance with examples of practical embodiments of the same, a set of drawings is attached wherein:

[0070] FIG. 1 is a schematic elevational view in which some of the components of a generator in accordance with a possible embodiment of the disclosure can be seen;

[0071] FIG. 2 is a schematic cross section view of the oscillating pole of the generator according to this preferred embodiment and of the vortices generated in the fluid surrounding it;

[0072] FIG. 3 is a diagram that illustrates, schematically, the relationship between the radius (R) of a pole and the height (H) above the ground, according to the state of the art (this figure is present in WO-2014/135551-A1);

[0073] FIG. 4 shows with greater detail the distribution of magnets and coils between the oscillating pole and the static structure, in the preferred embodiment illustrated in FIG. 1;

[0074] FIGS. 5 and 6 show, schematically, two different distributions of coils in a horizontal cross section of a generator according to two embodiments of the disclosure;

[0075] FIGS. 7 and 8 show two sets of magnets associated to the pole, according to a possible embodiment of the disclosure;

[0076] FIG. 9 illustrates, schematically, a cross section in the vertical plane of the two sets of magnets of FIGS. 7 and 8 and a coil with respect to which said sets can move;

[0077] FIGS. 10A and 10B illustrate two simplified models of the behaviour of a pole without any tuning system (FIG. 10A) and with a tuning system (FIG. 10B), respectively;

[0078] FIG. 11 represents the evolution against displacement (x) of the spring force (F.sub.k) and of the magnetic repulsion force (F.sub.b);

[0079] FIG. 12 represents the variation over time of the amplitude (displacement x) and frequency (oscillation along the time axis t) of a device without tuning (I) and a tuned device (II) (movement with magnetic repulsion) when subjected to the action of an instantaneous force in the initial instant;

[0080] FIGS. 13A-13D show, schematically, the geometric method used for determining the distance from the ground at which an extension of the pole does not suffer horizontal displacement for small bending angles;

[0081] FIG. 14 is a graph showing calculations performed to confirm what has been illustrated in FIGS. 13A-13D for several bending angles, showing that as the angles increase, the assumption of zero displacement is no longer correct;

[0082] FIG. 15 is a diagram illustrating the evolution with height of the diameter of a pole of height H for a working amplitude at its highest part of β.Math.D(H) and a lower diameter d;

[0083] FIGS. 16A-16D illustrate the arrangements of the first and second magnets in accordance with four different embodiments of the disclosure;

[0084] FIG. 17 is a cross sectional side view of a portion of a generator in accordance with an embodiment of the disclosure;

[0085] FIG. 18 is a cross sectional top view of a portion of the generator of the embodiment of FIG. 17; and

[0086] FIGS. 19A and 19B are schematic top views of two alternative magnet assemblies that can be used in the embodiment of FIGS. 17 and 18.

DETAILED DESCRIPTION OF THE DRAWINGS

[0087] FIG. 1 shows, schematically, a generator according to a possible embodiment of the disclosure comprising a first part in the shape of pole 1 extending vertically upwards from the ground 1000, the pole 1 being anchored in the soil by an anchoring base 13 which can be made of cement, concrete, or any other suitable material. In many embodiments of the disclosure, the pole has a longitudinal axis 100, and in many embodiments of the disclosure the pole 1 is substantially symmetric with regard to said longitudinal axis.

[0088] As shown in FIG. 2, when the laminar flow 1001 of the wind strikes on the pole-shaped first part 1, it produces a series of vortices 1002 that occur alternately on one side and on the other side of the pole 1 and with a constant distance 1003 between the successive vortices on each side of the pole. Therefore, a substantially constant drag force 1004 in the direction of the wind and a lift force 1005 substantially perpendicular to the general direction of the wind and to the direction of the drag force are produced on the pole 1. This lift force 1005 switches sign periodically, with a frequency which corresponds to the onset of the vortices, and this force causes the oscillation of the pole 1, towards one side and towards the other side. In this embodiment of the disclosure, the pole 1 has a circular cross section, such that its performance in what regards capturing energy of the wind does not depend on the direction of the wind, which can vary over time. In other embodiments of the disclosure, for example, when there is one very predominant direction of movement of the fluid, the pole may have another type of cross section, but the circular cross section can often be the most appropriate one.

[0089] The frequency of appearance of vortices depends on wind speed. Therefore, in order to maximise the energy capture of the pole, it may be desirable for the vortices to appear in a synchronised manner along the pole 1. Given that the wind speed, according to the Hellmann exponential Law, increases with height and given that the frequency of the appearance of vortices depends on both the relative velocity between air and pole (which in turn depends on wind speed) and on the characteristic dimension of the pole (in this case, on the diameter of the pole), it is appropriate for the diameter of the pole to increase with height as the relative velocity between air and pole increases with height. FIG. 3 illustrates schematically how, according to what is described in WO-2014/135551-A1, in the case of a pole having a radius (R) of approximately 60 mm at ground level, the radius increases to approximately 83 mm at the height (H) of 1 metre above the ground and to approximately 105 mm at a height of 4 metres above the ground. The ideal increase of the radius with height depends on the value of the Hellmann exponent and this exponent depends on the characteristics of the surroundings. In flat places, with ice or grass, its value is minimal and in very rough terrain or in cities, its value is higher.

[0090] On the other hand, as is known, when a force of oscillation is applied to an element or object, the corresponding energy is absorbed better if the force that is applied oscillates at a frequency that corresponds to the natural oscillation frequency of the object in question. The natural frequency depends on parameters such as the density and rigidity of the element. For a first part or pole 1 having a specific configuration and constitution, the frequency at which the vortices are generated and at which the lift force 1005 oscillates, will depend on the wind speed. As indicated in WO-2012/017106-A1 and in WO-2014/135551-A1, it may be desirable to synchronise the natural oscillation frequency of the first part with the frequency of appearance of the vortices.

[0091] Given that this frequency of appearance of vortices, for a determined capture element or pole, depends on wind speed, it may be desirable to vary the natural oscillation frequency of the pole based on wind speed.

[0092] For a solid bar, its natural oscillation frequency is:

ω=((I*E*K.sup.4)/d)−a.sup.2).sup.(1/2)

where E is Young's modulus, I is the sectional inertia moment, d is the density of the bar per unit of length, K is the spatial mode of oscillation (the 1.sup.st mode and its harmonics) and a is a damping constant. The more a structure is dampened (in other words, the more energy is extracted from it in the form of viscous losses, friction, etc.), the lower their oscillation frequency will be. The natural oscillation frequency of any structure depends on the damping to which it is subjected. Consequently, the more electrical power is extracted from the generator, the less its natural oscillation frequency is, unless this is offset by, for example, tensioning the structure, increasing its rigidity, etc.

[0093] WO-2014/135551-A1 describes how this can be achieved by actively acting on the piezoelectric material that is part of the structure of the pole. The generator illustrated in FIG. 1, a detail of which is shown in FIG. 4, has a passive system for adapting the natural oscillation frequency, based on the use of magnets associated to the pole 1 and with a static structure 2 arranged in correspondence with the base of the pole 1, surrounding the pole 1. FIGS. 1 and 4 show how in this embodiment of the disclosure the static structure 2 comprises a substantially cylindrical wall 21 which surrounds the pole 1 in correspondence with its bottom part.

[0094] As shown in FIGS. 1 and 4, this static structure 2 forms a second part of the generator and completely or partially surrounds the pole 1. The pole 1 comprises a relatively rigid part 11, which can be substantially hollow and made of lightweight materials such as, for example, carbon fibre, fibreglass, polyester resin, epoxy resin, basalt fibres, balsa wood, aluminium and/or titanium, etc. It may be advantageous that the material does not conduct electricity. This rigid part may include internal reinforcing elements 11a such as ribs, brackets or beams that provide structural rigidity. The upper end of the pole is preferably closed, for example, by a cap.

[0095] On the other hand, the pole 1 comprises a relatively flexible part 12, which is the one joining the pole 1 to the anchoring base 3 such that the rigid part 11 may substantially oscillate with respect to the base, despite its stiffness. This flexible part 12 may be a type of flexible rod which can be elastically deformed sideways, in an oscillatory manner, allowing the rigid part to oscillate as well. The bottom part of the flexible part 12 is embedded in a base 22 of the static structure 2 and its top part is housed within the rigid part 11 of the pole. FIG. 1 shows how the flexible rod 12 extends through the base 22 of the static structure and is also embedded in the anchoring base. However, a substantial part of the flexible part 12 is free and able to oscillate, together with the rigid part 11 towards one side and the other, owing to the aforementioned lift force.

[0096] FIG. 4 shows that the flexible part 12, in the shape of a rod, supports five magnet rings 30 and that coaxially with respect to these magnet rings 30 there are five magnet rings 40 mounted on the static structure 2, coaxially with respect to the flexible part 12 of the pole. The magnets 30 mounted on the flexible part 12 of the pole 1 and the magnets 40 mounted on the static structure 40 are arranged in such a way that they repel each other, or in other words, the poles of the same sign are facing each other, as schematically illustrated in FIG. 4 where the black part of the magnet represents the N pole and the white part the S pole.

[0097] In this way, when the oscillation of the pole 1 is produced, the flexible part 12 bends towards one side and towards the other, whereby a part of the magnets 30 mounted on the flexible part 12 approaches a part of the magnets 40 mounted on the static structure 2, while on the diametrically opposite side of the flexible part 12, a part of the magnets 30 moves away from the corresponding part of the magnets 40. The repulsion force between the magnets 30 and 40 is inversely proportional to the square of the distance between the magnets 30 and 40. When the wind increases, the amplitude of the oscillatory movement of the pole tends to increase, whereby the magnets 30 and 40 tend to get closer and closer during the part of maximum approach of each oscillation cycle and therefore, the maximum repulsion force produced between the magnets 30 and 40 in each oscillation cycle increases accordingly. The increase of this repulsion force increases the resonance frequency of the structure. In this way, the very structure of the generator of FIGS. 1 and 4, with its magnets 30 and 40, contributes to an automatic increase in the resonance frequency of the pole when the wind speed increases and vice versa. In this way, by properly selecting and arranging the magnets 30 and 40, something that can be done by trial and error tests and/or by computer simulations, the automatic adjustment of the natural oscillation frequency of the pole to wind speed can be achieved, such that it is always tuned with the frequency of appearance of vortices, thereby achieving a good uptake of energy from the movement of the fluid. In other words, a function of the magnets 30 and 40 may be to obtain the automatic tuning between the natural oscillation frequency of the pole and the frequency of appearance of vortices.

[0098] In other words, for example, both the oscillating pole 1 and the stationary part 2 are provided with magnets, for example, in the shape of magnetic rings or sets of individual magnets arranged in the shape of a ring, arranged coaxially and in such a way that the poles of the same sign repel (north against north or south against south). This allows magnetically confining the movement of the pole and increasing the oscillation frequency of the pole as the amplitude of oscillation increases.

[0099] FIG. 16A shows how these magnets can be arranged in one embodiment of the disclosure. The magnets are arranged in rings surrounding a vertical axis of symmetry of the generator, whereby the magnets 40 are arranged on a portion 21 of the static structure forming an outer ring of magnets, and the magnets 30 are arranged on the flexible part 12 of the pole 1, forming an inner ring of magnets. The outer ring of magnets 40 has a height corresponding to five magnets 40 arranged above each other, and the inner ring of magnets has a height corresponding to five magnets 30 arranged above each other. In both rings, the magnets are arranged following the so-called Halbach array in the vertical direction, that is, with the polarities alternating so that the magnetic field generated by the magnets is stronger on the side where the two rings of magnets are facing each other, than on the other side. Thus, efficient use is made of the magnets in terms of their contribution to the tuning of the natural oscillation frequency of the pole.

[0100] FIG. 16B illustrates a similar arrangement, but with only three magnets following each other in the vertical direction.

[0101] FIG. 16C illustrates an arrangement in line with the one of FIG. 16B, but with the magnets arranged in an inclined manner, so that both the outer and the inner rings have a shape corresponding to a truncated cone. This arrangement is considered useful for the purpose of producing a certain torque on the flexible part 12, preventing it from entering resonant modes different from the first mode of resonant oscillation of the first part.

[0102] FIG. 16D schematically illustrates an embodiment like the one of FIG. 16C, with the difference that each ring of magnets has a heighT corresponding to only one magnet. This kind of layout may be simpler to produce than the one of FIG. 16C, but it does not feature the advantages provided by the Halbach effect.

[0103] FIG. 4 illustrates how a plurality of coils 50 is mounted on the static part 2, in correspondence with its top part where substantial movement of the flexible rod 12 towards the sides occurs. The turns of the coils 50 are parallel or almost parallel to the horizontal plane. As illustrated in FIG. 4, the coils 50 are distributed in three levels, i.e., at three different heights above the base of the generator. These coils 50 can be provided with ferromagnetic cores 51.

[0104] The coils are arranged such that when the pole 1 oscillates, some of the above mentioned magnets 30 pass above and below the coils. As shown in FIG. 4, for each coil 50 there is a magnet 30 located at a height slightly above the coil and another magnet 30 located slightly below the coil, the polarity of the magnets being inverted such that when the coil passes above one of the magnets 30, the coil 50 passes once through a magnetic field oriented in one direction (for example N-S) and once through a magnetic field oriented in the opposite direction (S-N), as it has been schematically indicated in correspondence with one of the coils and pairs of magnets in FIG. 4. The passage of the coil through a varying magnetic field induces an electromotive force or potential in the coil, which may be collected and adapted by an electric power system 60, schematically shown in FIG. 4.

[0105] In other words, in order for the turns to produce an electromotive force and to generate electric power, several levels of magnetic rings 30 (or a set of individual magnets arranged in the shape of a ring) have been arranged on the flexible rod 12. The number of levels of magnetic rings 30 is equal to the number of levels of coils plus one (there are four levels of magnetic rings associated to the three levels of coils 50 in FIG. 4). In this way, the movement of the magnetic rings produces a change of direction and sense of the field lines within the coils. Each level of magnetic rings will have its antagonist, from the magnetic point of view, on its neighbour or neighbours, i.e., if the outermost part of one of the levels of magnetic rings is a south pole, its neighbouring level or levels will have on the outermost part a north pole and vice versa, as it has been schematically illustrated in FIG. 4.

[0106] FIG. 4 shows, schematically, how the magnets 30 are mounted on a support structure 13 mounted on the flexible part 12 and how the coils 50 are mounted on the static structure 2 itself (see also FIG. 5). It would also be possible to mount the coils 50 on the pole, but from the practical point of view it may be preferable to mount them on the fixed portion to facilitate the connection to the external network to which the generated power is intended to be transmitted, thereby reducing the risk of fatigue rupture of the conductors evacuating the energy and avoiding unnecessary viscous losses. The energy generated by the coils 50 can be appropriately rectified and conditioned by a power electronics system 60, which may include for example an inverter, etc., and a conduction system 61 can evacuate the electric power generated.

[0107] FIG. 6 shows an alternative configuration in which, at every level of coils—there are three levels of coils 50 in FIG. 4—the coils are arranged in two concentric rings. The number of rings, the size of the coils, etc., is something that the person skilled in the art will chose depending on aspects such as the size of the generator, the displacement in the lateral direction of the flexible part during the oscillation, etc., with the purpose of achieving an optimal or at least acceptable performance of the generator.

[0108] FIGS. 7, 8 and 9 show, schematically, how in some embodiments of the disclosure, the magnets mounted on the support 13 discussed above can be arranged, at every level, in the shape of a plurality of concentric rings 30, 31 and 32. FIG. 9 is a vertical cross section view of the two sets of magnets illustrated in FIGS. 7 and 8, one arranged above the other and separated by a gap in which the coils 50 can fit. As it is shown, with these two sets placed at a certain distance from each other in a vertical direction, a separator space is established in which three changes of polarity or direction of the magnetic field occur in each coil. Therefore, when a coil 50 passes through said space owing to the oscillatory movement, the coil will be subjected to a magnetic field that changes polarity a plurality of times. Given that the current generated depends on the variations in the magnetic field to which the coil is subjected, this high frequency variation in the magnetic field is beneficial for the generation of current.

[0109] In some embodiments of the disclosure, the magnets 30, 31 and 32 mounted on the flexible rod 12 may have ferromagnetic material attached to them to conduct the field lines in a suitable manner for, for example, increasing, within a given space, the number of polarity/direction changes of the magnetic field, to maximize the number of changes of direction of magnetic field to which the coils 50 are subjected during a cycle of oscillation of the pole.

[0110] As follows from what has been previously explained, in an embodiment of the disclosure as the one from FIGS. 1 and 4, the top part of the static part has a function corresponding to that of the stator of a non-conventional alternator designed to produce energy without the use of any bearing or reduction gearbox and that can produce power regardless of the direction in which the rod 12 is flexed.

[0111] FIG. 4 shows how the magnets are mounted on a total of five rows, of which the four top rows contribute to the electrical power generation owing to their interaction with the coils 50, while both the four top rows and the bottom row contribute to the auto-tuning of the generator to wind speed.

[0112] FIGS. 10A and 10B illustrate schematically the behaviour of a pole without any tuning system (FIG. 10A) and the behaviour of a pole with the tuning system according to a possible embodiment of the disclosure (FIG. 10B).

[0113] The object of the tuning mechanism is to modify the natural oscillation frequency of the equipment according to the speed of the fluid. When the device has no tuning system its movement can be modeled as the one of a damped simple harmonic oscillator (a) (FIG. 10A):

m.Math.{umlaut over (x)}+c.Math.{dot over (x)}+k.Math.x=0  a)

[0114] where m is its mass, c is the damping constant including the structural damping of the device itself, other losses and the mechanical energy converted into electrical energy and k is the elasticity constant of the elastic rod. In this case, the natural oscillation frequency of the equipment is:

[00001]$\begin{array}{cc}{w}_0=\sqrt{\frac{k}{m}}& b)\end{array}$

[0115] When, given the generation of vortices, the oscillating pole is affected by the sinusoidal force F with maximum value F.sub.0 (proportional to the square of the frequency if the value of the lift coefficient is considered constant), a delay in φ and frequency w=2.Math.π.Math.f (w[rad/s], f[Hz]), the movement can be modelled as the one of a forced damped harmonic oscillator:

m.Math.{umlaut over (x)}+c.Math.{dot over (x)}+k.Math.x=F=F.sub.0.Math.cos(wt+φ)  c)

[0116] When the frequency w coincides with the natural frequency of the equipment w.sub.0, the latter enters in resonance and experiences a remarkable increase in its ability to absorb energy from the fluid.

[0117] As the frequency ω is proportional to the speed of the fluid, in principle, given that the device has only one natural oscillation frequency (in the first oscillation mode), there will only be one single speed at which the device would work. However, a power generator such as an aerogenerator will be more profitable the greater the number of hours/year it can be in operation. As explained above, there is a small range of wind speeds (the aerodynamic phenomenon of lock-in) in which an equipment based on the Karman vortices can maintain its resonance, but this is far smaller than desirable for a reasonably competitive aerogenerator.

[0118] In order to be able to increase this range of wind speeds, a tuning mechanism can be incorporated that modifies the oscillation frequency of the device. Thus, the pole will oscillate at greater frequency in the presence of higher wind speed, or in other words, in the presence of an increase in the frequency of appearance of vortices.

[0119] The arrangement of FIG. 10B differs from that of FIG. 10A by the addition of two pairs of magnets in repulsion mode. The movement of said model can be described by the following expression:

[00002]$\begin{array}{cc}m.Math.\stackrel{\mathrm{.Math.}}{x}+c.Math.\stackrel{.}{x}+k.Math.x+\frac{b}{{\left(d-x\right)}^2}-\frac{b}{{\left(d+x\right)}^2}=F& d)\end{array}$

[0120] where b would include (the Coulomb law for magnetism), the inverse of the magnetic permeability and the product of the magnetic masses, d is the distance at rest between each pair of magnets.

[0121] As shown in FIG. 11, the evolution with the displacement x of the spring force F.sub.k produced on the mass by deformation of the rod and the joint force produced by the two pairs of magnets F.sub.b are very different. As it can be seen and as already mentioned, as the mass (the pole) moves, near its neutral position of zero bending, the spring force is predominant against the magnetic forces. As the displacement increases, its influence begins to equalise and in high displacements, the predominant force is of magnetic origin.

[0122] This has several implications.

[0123] The kinetic energy of the oscillating pole when it passes through its neutral position of zero bending depends in both cases on the square of its mass and its speed. Not so with the stored potential energy when its displacement is maximum. In the case represented in FIG. 10A, the potential energy is only elastic potential energy and in the case represented in FIG. 10B, the potential energy will have both an elastic and a magnetic nature with the difference that the potential energy of magnetic origin increases with the cube of the displacement and not with the square, as is the case with the elastic potential energy. As shown in FIG. 12, in comparison with the damped simple harmonic movement (I) for large displacements, the trajectory of the movement with magnetic repulsion (II) suffers an increase in its frequency of oscillation. With small displacements (on the right side of the graph), where almost all the potential energy is accumulated by the elastic rod, both trajectories have a very similar size period.

[0124] FIG. 17 illustrates a portion of a generator in accordance with another embodiment of the disclosure. Here, the first part can generally be shaped as shown in FIG. 1, and include a flexible part 12. In the embodiment of FIG. 17, this flexible part is surrounded by a generator assembly comprising a stationary first generator module 200 which includes coils 50 and 500, and a second generator module 400 that is moveable in parallel with the longitudinal axis 100 of the first part 1, that is, in this embodiment, in the vertical direction. The second generator module 200 comprises a plurality of magnets 300 stacked on top of each other and arranged in rings, and the first generator module comprises coils 50 surrounding the magnets at the outside of the second generator module 400, and coils 500 surrounded by the magnets 300, within the second generator module 400. The coils can also be provided with iron or ferromagnetic elements schematically illustrated at 501, to concentrate the magnetic field. Movement of the magnets 300 in the vertical direction will generate an electromotive force in the coils, as known in the art.

[0125] The second generator module comprises an top annular frame member 602 on top of the magnets 300, and a bottom annular frame member 604 below the magnets. 300 Thus, the second generator module can be regarded as a kind of piston, arranged to move in the vertical direction, between the coils 50 and 500 of the first generator module.

[0126] The first generator module likewise comprises two annular frame members 601 and 603. An upper one of said annular frame members 601 is attached to the top annular frame member 602 of the second generator module by rod-shaped elements or connecting members 605 as shown in FIG. 18, whereas the lower annular frame member 603 of the first generator module 200 is attached to the bottom annular frame member 604 of the second generator module by similar rod-shaped members 608. These rod-shaped members can, for example, be of metal, of carbon fibre, or of any other material featuring sufficient traction and fatigue resistance.

[0127] FIG. 18 schematically illustrates how the rod members 605 are attached at one end to the annular frame member 601 of the first generator module, and at another end to the annular frame member 602 of the second generator module. Three openings 607 are provided in the annular frame member 602, said opening allowing a corresponding rod-shaped member 605 to pass through the annular frame member 602, said openings having an extension in the vertical direction that allows a displacement in the vertical direction between the rod-shaped member 605 and the annular frame member 602. Similar rod-shaped members 608 and openings 609 are provided in correspondence with the bottom annular frame members 603 and 604.

[0128] In FIG. 18 it is schematically illustrated how the points of connection 605A and 605B of the rod-shaped member 605 to the annular frame member 601 and the annular frame member 602, respectively, are separated by an angle α in the horizontal plane, in relation to an axis of symmetry 606 of the second generator module (in this embodiment, this axis of symmetry is aligned with the axis of symmetry 100 of the first part 1). In this case, this angle is approximately 120°. This substantial separation of the attachment points can be advantageous in that it allows for the use of relatively rigid connecting members 605, for example, metal or carbon fibre rods or bars, which can serve to maintain the relative position of the first generator module and the second generator module substantially fixed in the plane perpendicular to the longitudinal axis of the first part, thereby preventing contact between the first generator module and the second generator module, while at the same time allowing for a sufficient amplitude of the movement of the second generator module in relation to the first generator module, in parallel with said longitudinal axis of the first part.

[0129] Only three rod-shaped members are shown in FIG. 18, but any other suitable number of rod-shaped members can be used, and the angular placement of the attachment points to the annular frame members can be chosen as preferred by the person skilled in the art.

[0130] FIG. 17 shows how the second generator module is suspended or floating in the air, due to the repulsion between a ring of magnets 220 arranged below the second generator module 400, and a ring of magnets 420 arranged at the bottom of the second generator module. Thus, the interaction between these magnets 220 and 420 biases the second generator module upwards, against the force exerted by gravity. On the other hand, in this embodiment of the disclosure, magnets 460 associated to the first generator module and magnets 260 associated to the second generator module 200 at the top of the second generator module, bias the second generator module downwards. In some embodiments of the disclosure, the magnets can be replaced by springs, and/or the magnets are not present at the top of the second generator module, as in some embodiments gravity can serve alone to bias the second generator module downwards.

[0131] On the other hand, additional magnets 702 or 703 are attached to the second generator module 400 at the top thereof, and arranged to interact with corresponding magnets 700 or 701 attached to the first part, in this case, to the the flexible part 12 of the pole 1. More specifically, these magnets 700 or 701 are arranged on a frame 705 attached to the flexible part 12, the frame comprising a plurality of arms (three arms in the embodiment shown in FIGS. 19A and 19B). In FIG. 19A, spherical or partially spherical magnets 700 are arranged in correspondence with the ends of the arms of the frame. In FIG. 19B an alternative embodiment is shown, with magnets 701 having a strip-like shape in the horizontal plane extending along the arms. In FIG. 17 it is schematically shown how magnets having a corresponding spherical 702 or strip-like 703 shape are arranged at the top of the second generator module 400.

[0132] FIG. 17 shows the flexible part 12 in the neutral position, that is, extending vertically along the vertical axis 100. Here, the displacing magnets 700 (or 701) attached to the frame 705 are close to the displaced magnets 702 (or 703) arranged at the top of the second generator module 400, thereby biasing the second generator module downwards. During the oscillating movement of the first part 1 including the flexible part 12, the distance between the displacing magnets 700/701 and the displaced magnets 702/703 will increase and decrease cyclically. On the other hand, the second generator module can, due to the way in which it is suspended due to the interaction between the magnets 220 and 420 (and/or springs) and optionally between the magnets 260 and 460 (and/or springs) and due to gravity, oscillate up and down. During each cycle of oscillation of the first part 1, the interaction between the displacing magnets 700/701 and the displaced magnets 702/703 repetitively provides an impulse to the second generator module 400, thereby transferring energy from the first part 1 to the second generator module 400, which will start to oscillate and continue to oscillate, whereby this oscillation displaces the magnets 300 in relation to the coils 50 and 500, generating electric energy.

[0133] It has been found that this arrangement is an appropriate option for the generation of electric energy out of the oscillatory movement of the first part produced by the vortices. Also, the described embodiment can be regarded as especially advantageous in that there is no friction between moving parts, and there are no roller bearings that require lubrication. The use of elements of for example titanium, steel or carbon fibre for physically interconnecting the first generator module and the second generator module can be an appropriate and resistant solution, allowing for long-term operation without the need for replacing parts due to wear, and without any need for lubrication. The fact that the second generator module can be caused to oscillate at a frequency higher than the frequency of oscillation of the first part can be useful to enhance to efficiency of the conversion of the energy represented by the oscillation of the first part, into electrical energy.

[0134] The described arrangement of the displaced and the displacing magnets can also be considered especially advantageous, in that the lateral displacement of the displacing magnets can imply that the duration of high repulsive forces between the displacing magnets and the displaced magnets is rather short, whereby the transfer of energy from the first part to the second generator module takes place during a short period, in an impulse-like manner. The oscillation of the second generator module will be determined on the one hand by this impulse, that is, on the energy received from the first part, and by the mass of the second generator module, by the dampening that takes place due to the extraction of electric power from the coils, by the rigidity of the connecting members 105, and by the repulsive forces exerted by the magnets 220/420 and 260/460.

[0135] On the other hand, as described above, WO-2012/017106-A1 proposes an increase in pole diameter with height introducing the Hellmann exponential Law according to which the speed of the air increases with height. In this way the vortices might be produced synchronously at all the sections of the pole. However, WO-2012/017106-A1 has not taken into account the variation of the relative velocity of the air against the pole that is due to the very movement of the pole.

[0136] The geometry of the pole should be carefully designed such that the generated vortices act synchronously throughout its length, so as to prevent the vortices generated at certain height from being fully or partially cancelled by those generated at a different height. In order for the geometry of the pole to have a proper or optimal performance it is not only necessary to consider the air speed profile in the working area of the device, but it is also necessary to take into account the oscillation of the pole itself, given that the oscillation of the pole affects the relative velocity between air and pole.

[0137] As explained above, in many embodiments of the disclosure the pole comprises a rigid element 11, sustained or supported by an elastic rod 12, which in some embodiments of the disclosure may be considered to have a constant cross section and to be longitudinally isotropic. If this is so, the position A (see FIGS. 13A and 13B) of its free top end (i.e., the top end of the area wherein the deformation of the rod is not limited by its embedding in the rigid element) in any of its radial planes X-Y may be calculated in the following way:

[00003]$\begin{array}{cc}x=\frac{L}{\theta }.Math.\left(1-\cos \left(\theta \right)\right).Math..Math.y=\frac{L}{\theta }.Math.\mathrm{sen}\left(\theta \right)& e)\end{array}$

where L is the length of the deformable area of the rod (i.e., the part of the rod that is not embedded in the base or in the rigid part) and e is the flexed angle with respect to the vertical.

[0138] FIGS. 13C and 13D show how a segment AA′ with length I may be drawn, with the top end matching the free top end of the elastic rod and with an angle θ with respect to the vertical (see FIG. 13D). The position of A′ is given by the following formula:

[00004]$\begin{array}{cc}x=\frac{L}{\theta }.Math.\left(1-\cos \left(\theta \right)\right)-l.Math.\sin \left(\theta \right).Math..Math.y=\frac{L}{\theta }.Math.\left(\mathrm{sen}\left(\theta \right)\right)-l.Math.\cos \left(\theta \right)& f)\end{array}$

[0139] It is possible to observe that, for sufficiently small flexion angles θ, the value of I for the displacement of A′ to be minimal during an oscillation of the rod, turns out to be

[00005]$l\approx \frac{L}{2}.$

(see FIG. 14). Given its “immobility” against flexion of this point, the formula of Von Karman can be applied in its position. The diameter d of the pole can be set as a design parameter at the point where its displacement produced by the oscillation is negligible, namely, at half the height of the flexible part of the rod:

[00006]$\begin{array}{cc}D\left(\frac{L}{2}\right)=d..Math.f\left(\frac{L}{2}\right)=\frac{S.Math.v\left(\frac{L}{2}\right)}{d}& g)\end{array}$

[0140] In order to be able to generalize this formula for any value of y, it can be assumed that at any height (∀y), in the range of Reynolds in which the device will work, the value of Strouhal is approximately constant and identical to the value it takes when

[00007]$y=\frac{L}{2}.$

It can be set as an objective that the frequency of appearance of vortices remains constant at any height.

[00008]$\begin{array}{cc}f\left(y\right)=f=\frac{S.Math.v_r\left(y\right)}{D\left(y\right)}=\mathrm{constant}& h)\end{array}$

where v.sub.r(y) is the relative velocity of the air (i) that strikes on the moving pole. This relative velocity has two components, one is the absolute velocity of the air relative to the ground and, the other, the velocity with respect to the pole caused by the oscillation of the same. Obviously, the average velocity of oscillation will be four times the maximum amplitude of oscillation divided by the period (or multiplied by its inverse, the frequency).

[00009]$\begin{array}{cc}{v}_r\left(y\right)={\left(v^2\left(y\right)+{\left(4.Math.X\left(y\right).Math.f\right)}^2\right)}^{\frac{1}{2}}& i)\end{array}$

X(y) being the amplitude of the oscillation at each height y. Substituting i) in the equation h) and squaring, the following is obtained:

[00010]$\begin{array}{cc}{f}^2=\frac{S^2.Math.\left(v^2\left(y\right)+16.Math.X^2\left(Y\right).Math.f^2\right)}{{D\left(y\right)}^2}.fwdarw.f^2=\frac{S^2.Math.v^2\left(y\right)}{{D\left(y\right)}^2-16.Math.S^2.Math.X^2\left(y\right)}& j)\end{array}$

Making it equal to the square of g) the following is obtained:

[00011]$\begin{array}{cc}{D}^2\left(y\right)=\frac{d^2.Math.v^2\left(y\right)}{v^2\left(\frac{L}{2}\right)}.Math. .Math.16.Math.S^2.Math.X^2\left(y\right)& k)\end{array}$

For a device of total height H and a “nominal” amplitude of maximum oscillation in its uppermost part of β times its diameter at that point X(H)=β.Math.D(H) and taking into account that the pole is considered as completely rigid, the following is obtained:

[00012]$\begin{array}{cc}X\left(y\right)=\frac{y-\frac{L}{2}}{H-\frac{L}{2}}.Math.\beta .Math.D\left(H\right).fwdarw.X\left(H\right)=\beta .Math.D\left(H\right)& l)\end{array}$

Applying this to the equation k) for y=H the following is obtained:

[00013]$\begin{array}{cc}{D}^2\left(H\right)=\frac{d^2.Math.v^2\left(H\right)}{v^2\left(\frac{L}{2}\right)}+16.Math.S^2.Math.{\beta }^2.Math.D^2\left(H\right).fwdarw.D^2\left(H\right)=\frac{d^2.Math.v^2\left(H\right)}{V^2\left(\frac{L}{2}\right).Math.\left(1-16.Math.S^2.Math.{\delta }^2\right)}& m)\end{array}$

Combining this with the equations l) and k) the following is obtained:

[00014]$\begin{array}{cc}{D}^2\left(y\right)=\frac{d^2}{v^2\left(\frac{L}{2}\right)}\left[v^2\left(y\right)+\frac{16.Math.S^2.Math.{\beta }^2}{\left(1-16.Math.S^2.Math.{\beta }^2\right)}.Math.{\left(\frac{y-\frac{L}{2}}{H-\frac{L}{2}}\right)}^2.Math.v^2\left(H\right)\right]& n)\end{array}$

Finally

[0141] [00015]$\begin{array}{cc}D\left(y\right)=\frac{d}{v\left(\frac{L}{2}\right)}.Math.{\left[v^2\left(y\right)+\frac{16.Math.S^2.Math.{\beta }^2}{\left(1-16.Math.S^2.Math.{\beta }^2\right)}.Math.{\left(\frac{y-\frac{L}{2}}{H-\frac{L}{2}}\right)}^2.Math.v^2\left(H\right)\right]}^{\frac{1}{2}}& o)\end{array}$

[0142] This expression describes the variation of the characteristic dimension of a pole that generates synchronously and throughout its whole length vortices taking into account the air velocity profile and the own oscillation.

[0143] In order to calculate v(y) with

[00016]$y=\frac{L}{2},$

y=H or any other value comprised between 0 and H, expressions that try to represent with different fidelity the distribution of velocities of the air with the height can be introduced. Typically, the Hellmann exponential law can be introduced for neutral atmospheres, the formulation linked to the Monin-Obukhov similarity theory for neutral, stable and unstable atmospheres, etc.

[0144] FIG. 15 illustrates schematically the evolution with height of the diameter of a pole of height H for a working amplitude at its uppermost part of β.Math.D(H) and a lower diameter d.

[0145] The diameter d is a mathematical artefact useful to describe the evolution of diameters (or characteristic dimensions) of the rest of the pole, but it is not necessary for the rigid element of the pole to actually exist as such, physically, at the height

[00017]$y=\frac{L}{2}.$

[0146] The expressions “first generator module” and “second generator module” are used for referring to the different parts, such as a stationary part and a moveable part, of the assembly in charge of converting kinetic energy into electrical energy by relative displacement between magnets or similar in relation to coils. The use of the term “module” is not intended to denote a specifically modular character of the generator.

[0147] In this text, the term “magnet” generally refers to a permanent magnet, although whenever appropriate also electromagnets may be used, as readily understood by the person skilled in the art.

[0148] In this text, the word “comprises” and its variants (such as “comprising”, etc.) should not be construed as excluding, that is, they do not exclude the possibility of other elements, steps, etc. from being included in the description.

[0149] On the other hand, the disclosure is not limited to the specific embodiments that have been described but it also includes, for example, the variants that can be carried out by the person of average skill in the art (for example, regarding the choice of materials, dimensions, components, configuration, etc.), within what follows from the claims.