IL301684B2 - System and Method for Power Generation - Google Patents

Description

301684/3 System and Method for Power Generation FIELD OF THE INVENTION The present invention relates to a turbine power generator.

BACKGROUND OF THE INVENTION Wind power generation is uncommon in urban areas. Buildings and other structures affect high speed laminar flow and convert it into a low-speed turbulent flow.

It is challenging for most traditional wind power turbines because they are not designed to be effective in such working conditions. To increase the amount of energy that can be generated, wind turbines should be installed well above the structure (the higher the turbine, the greater the wind power), and since the energy extracted from the wind is proportional to the airflow area, it should be exposed to a significantly larger airflow area.

These principles not only make it difficult to integrate the turbine in harmony with the environment, but they also increase the production and installation costs of the turbine.

Currently, wind power is most often harvested by massive wind turbine generators whose production, installation, and maintenance are complex and very expensive. For these reasons, the wind industry targets locations with the highest wind energy potential – usually on mountains and offshore – to ensure appropriate Return on Investment (RoI).

To reduce production, installation, and maintenance costs and to achieve appropriate RoI, there is a need for simple, lightweight wind turbine generator that is easy to build and maintain. The lower the center of gravity of the system, and the lighter the main structure, the easier are the installation and the access to the components of the system for both installation and maintenance. 301684/3 US2010/0266412 discloses a horizontal wind turbine that includes turbine wheel carrying sailwing assemblies. Another variation of the sails wind turbine is shown in U.S.

Pat. 9,051,916, which discloses a vertical wind turbine that uses sails to drive a frame.

Additional configuration of the sails wind turbine is shown in US2014/0341736, which discloses a vertical sail wind turbine system that comprises rectangular sails in frames fixedly attached at the tip of parallel horizontal yardarms. Lanyards are used to limit the motion of the sails in a mechanical way and to introduce a braking system.

More specifically, it is known in the prior art to provide overload protection that prevents damage to the sails in the event of strong winds, such as hurricanes. For example, EP 1 828 598 discloses a governor articulated to the sails for inducing rotation of the sails out of the path of excessive wind forces.

U.S. Pat. No. 7,258,527 employs stop members adapted to limit a pivot angle of the airfoil, wherein each stop member is adapted to lift a pivot limitation of each airfoil for allowing the airfoil to pivot when the airfoil experiences a pushing force of the wind larger than a maximum resistance force thereof. The mechanical impact between the airfoil and the stop member produces significant noise, which is disruptive particularly when disposed in urban environments. The impact also increases the structural requirements of both the airfoil and the stop member.

The wind turbines described in the above-mentioned publications allow the wind turbine’s blades to be formed of lightweight and less expensive material. However, these advantages alone are not enough. High aerodynamic efficiency and structural simplicity of the system as a whole are needed to compete with current designs of vertical and horizontal wind turbines. In addition, mechanical impacts due to collision between the vanes and the stopper is detrimental as explained above. A significant cost reduction may lead the energy consumers in the areas considered as having medium wind energy potential, toward a model of self-generation and toward a decentralized power generation network. By achieving high efficiency in the low-to-medium wind speed range in laminar and turbulent wind conditions, in harmony with the environment, while subject to significantly lower production, installation, and maintenance costs, wind power technology can become viable for many more energy consumers around the world, both in urban and rural areas. 301684/3 SUMMARY OF THE INVENTION In accordance with one aspect of the present invention there is provided a system for energy generation comprising: a mast adapted for coupling to a support structure; a first rotor located toward a first end of the mast and being rotatable about a longitudinal axis of the mast; a second rotor located toward a second end of the mast and being rotatable about said axis; at least two vanes coupled to the first rotor and to the second rotor via respective coupling points, each vane being independently rotatable about a respective line joining the coupling points under force of a fluid directed to the system; and a pair of contactless reactive elements associated with each vane and configured to mutually co-operate to apply a respective reactive force whereby the fluid force acts in concert with the reactive force acting on at least one vane and opposes the reactive force acting on at least one different vane.

In some embodiments at least one of the rotors or the mast supports at least two reactive elements configured to interact with the vanes to create reactive forces.

In some embodiments the first rotor and the second rotor are rigidly coupled to the mast and the mast is configured to rotate within a support structure and to drive, directly or via a transmission, a power converting device.

In some embodiments the first rotor and the second rotor are configured to rotate about the mast and the mast is rigidly coupled to a support structure, while either or both of the first and second rotors are configured to drive, directly or via a transmission, a power converting device. The power converting device can either be an electric generator, a pump, or any other form of mechanically driven device.

In some embodiments the reactive element is a mechanical stopper that arrests the rotation of the vane when it meets the reactive element.

In some embodiments the vane is configured to carry a reactive target which is made of either metal or a permanent magnet and configured to interact with a reactive element chosen from the group of permanent magnets or electromagnets to create a magnetic force between the vane and the reactive element. The magnetic force may be any of the following forms: repulsive, attractive, or controllable attractive or repulsive. 301684/3 In accordance with another aspect of the invention there is provided a method of energy generation, the method comprising: directing a fluid force against a rotatable structure comprising a mast and at least two vanes each configured to rotate about a respective vane rotation axis, whereby during a complete cycle of rotation the fluid force impinges against different ones of the vanes causing the structure to rotate about the mast; and associating with each of the vanes, respective pairs of contactless reactive elements wherein the reactive elements in each pair are configured to mutually co-operate to apply a respective reactive force whereby the fluid force acts in concert with the reactive force acting on at least one vane and opposes the reactive force acting on at least one different vane.

In some embodiments, under extreme rotational velocities or fluid flow, the force of the reactive elements is reduced by a retraction mechanism to avoid an overload of the system.

In some embodiments, the force of the reactive elements is partially reduced by a retraction mechanism to control the power generated by the system.

In some embodiments, under extreme rotational velocities or fluid flow, the magnetic force of the reactive elements is electrically reduced to avoid an overload of the system.

In some embodiments, partial reduction of the magnetic force of the reactive elements enables control over the power generated by the system.

BRIEF DESCRIPTION OF THE DRAWINGS To understand the invention and to see how it may be carried out in practice, embodiments will be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Figs. 1A and 1B are schematic views of one embodiment of a turbine power generation system of a conical shape according to the present invention; Figs. 2A and 2B are schematic views of system of the embodiment of Fig. 1B responding to the fluid flow; 301684/3 Figs. 3A and 3B are, respectively, perspective and cross-sectional views of a turbine power generation system of conical shape with a concentric power converting device; Fig. 4 is a schematic view of a turbine power generation system of cylindrical shape in idle mode responding to the fluid flow; Figs. 5A and 5B are cross-sectional views of the upper side of the system of the embodiment of Fig. 4 in an idle and in a power mode, respectively; Figs. 6A and 6B show respectively a perspective view of the embodiment of Fig. 1B having wing-shaped vanes and a detailed view of the wing-shaped vane; and Figs. 7A and 7B are side and top views, respectively, of the embodiment of Fig. 1B having vanes made of sail cloth.

DETAILED DESCRIPTION OF EMBODIMENTS Figs. 1A and 1B schematically show a system 2 for power generation, according to different embodiments of the invention. The system 2 includes a mast 4 attached to a support structure 6. A first rotor 8 and a second rotor 10 are coupled to the mast 4 toward opposite ends thereof and are configured to rotate about the axis of the mast 4. The second rotor 10 supports four reactive elements 16, which interact with complementary reactive elements 18 attached directly or indirectly to the vanes as shown in Fig. 1B. The reactive elements 16 and 18 co-operate to induce either an attractive or a repulsive force to the vanes that depending on the wind direction relative to the plane of the vanes will serve either to enhance or reduce the pressure of the wind on the vanes. Specifically, at any given instant, the reactive force of one vane will act in concert with the wind force, and the reactive elements of a different vane will oppose the wind force.

Fig. 1A shows four cords 12 coupled to the rotors 8 and 10 via respective coupling points at opposite ends of each cord 12. The centerlines of the cords 12 serve as axes about which the respective vanes rotate independently of each other. The number of cords 12 and reactive elements 16 in Fig. 1A is for illustration only. Any number of cords 12 and of reactive elements 16, equal to or greater than two, may be employed. Fig 1B shows the system of Fig. 1A, wherein each cord supports a vane 14 that is rotatable about the axis of the cord 12. The reactive elements 16 are configured to interact with the complementary reactive elements 18 so as to create a reactive force which, depending on the direction of 301684/3 the wind against the vane, impedes or enhances rotation of the vane 14 about the cord 12 when the vane 14 is in close proximity to the reactive element 16. The interaction between the reactive elements 16 and the complementary reactive elements 18 can be effected mechanically, in a similar manner to the prior art, but is preferably contactless based on mutually attractive or repulsive magnetic or electrostatic forces. In some embodiments, the reactive element 16 is a first magnet that attracts or repels a second magnet constituting the complementary reactive element 18 attached to the vane 14.

The magnetic interaction between the reactive elements 16 and 18 can be of any of the following forms: repulsive, attractive (can be also achieved by forming the reactive target 18 of a ferromagnetic material such an iron), and controllable attractive or repulsive. For the sake of simplicity and for the purpose of this description it will be assumed that both the reactive elements 16 and 18 are permanent magnets whose polarities are configured to create a mutually repulsive force.

Based on Coulomb’s law, the magnitude, or absolute value, of the attractive or repulsive electrostatic force between two point charges is directly proportional to the product of the magnitudes of their charges and inversely proportional to the squared distance between them. The implication of this law is that reactive force between the reactive elements 16 and 18 increases as the two elements approach each other. The advantage of the electrostatic reactive force over prior art approaches is that the build-up of the reactive force is gradual and there is no impact. Accordingly, the noise and the significantly higher structural requirements associated with prior art approaches can be avoided. Another advantage, is that the electrostatic force can be adjusted by varying either the charge and/or the mutual separation between the reactive elements, either permanently or dynamically, to a threshold beyond which the wind force on the vane will overcome the reaction force and therefore the reactive elements 16 and 18 will no longer stop the rotation of the vane about the cord 12 and overload of the turbine caused by high winds will be avoided, while the turbine will continue to generate power.

The threshold can be computed in the following, simplified, way: The torque (Newton-meter) produced by a single vane may be estimated based on of the wind resource power (Watt) at the wind-speed limit value (meter per second) multiplied by the turbine coefficient of performance (unitless) and divided by the turbine rotation velocity (radian per second); The force (Newton) on the vane can be calculated by dividing the 301684/3 torque by the distance (meter) between the center of the mast 4 and the geometrical center of the vane 14; The threshold reactive force (Newton) for the vane 14 can be found based on Newton’s law.

Example for threshold reactive force calculation: Given: threshold wind-speed V of 16 ms-1; turbine front area A of 1m2 ; rotation velocity of 15.7 radian per second; vane geometry center from mast center of 0.3 meter; coefficient of performance of 0.2; air density ρ of 1.225 kgm-3 .

The solution is: The wind power P at the threshold wind-speed V is equal to 2,509 W, based on P=0.5*ρ*A*V 3 ; torque at 0.2 coefficient of performance equal to 32 Newton-meter; force on the vane equal to 106 Newton; approximate reactive force between elements 16 and 18 equal to 53 Newton. This level of reactive force can be achieved by elements 16 and 18 made of a neodymium magnet (also known as NdFeB, NIB or Neo magnet) of diameter 2.5 cm and length 1cm, approximately. For more accurate choice, the magnet material and the magnet grade should be evaluated based on the manufacturer’s data sheets.

Fig. 1B shows an initial disposition of the vanes 14 and will serve to explain the response of the system 2 to calm weather, where the fluid flow speed is either zero or very low, and therefore cannot move the vanes 14 from their equilibrium position where the orientation of all vanes relative to the mast is substantially identical. For the sake of clarity, it should be noted that the fluid can be either gaseous or liquid and that the system can operate in both environments. Because of the angle between the axis of the cord 12 and the axis of the mast 4, in calm weather gravitational forces of the vanes 14 will lead them to reach an equilibrium shown in Fig. 1B, where the reactive elements 16 and 18 are in close proximity. Owing to the repulsive force between the reactive elements 16 and 18, the vanes 14 are unable to remain in the plane defined by the axis of the cord 12 and the reactive element 16. As a result, all the vanes 14 will be slightly rotated about the axis of the cords 12 as shown in Fig. 1B. It will be appreciated that the direction of this rotation is for illustration only.

Fig. 2A shows that when the system 2 subjected to fluid flow 40, the four vanes 14a, 14b, 14c and 14d will react in the way shown in the figure: vane 14a will enter a hold state as its attack angle creates a lift force balanced by an internal repulsive force between 301684/3 the reactive elements 16a and 18a. At the same time, vane 14b will also enter a hold state as its attack angle creates a drag force balanced by an internal repulsive force between its corresponding reactive elements only one of which 18b is shown. As a result, vanes 14a and 14b will create a torque about the axis of the mast 4 in a counterclockwise direction shown by an arrow at the bottom of the mast 4. This torque will turn the rotors 8 and 10 and all the vanes 14a-14d rotatably coupled thereto.

Simultaneously, vanes 14c and 14d will enter a free state as their lift and drag forces act in the same direction as the repulsive forces between their corresponding pairs of reactive elements 16 and 18. Free state is characterized by negligible of reactive force between the reactive element 16 and 18 allowing the vanes 14 to rotate about the axis of the cord 12 to a position where all the forces that are acting on the vane (lift, drag, inertia and gravity) cancel each other out.

Vanes that are in a hold state (14a and 14b) contribute to power generation. Vanes that are in a free state (14c and 14d) neither aid nor significantly oppose power generation, because their attack angle relative to the net fluid flow vector is close to zero (if gravitational and inertial forces are neglected).

Vane 14b will alter its state from hold to free at the point where the net torque (sum of the individual torques as result of lift, drag, inertia and gravity) about the axis of the cord 12b causes its direction to change, so that its respective reactive elements 16 and 18 are mutually repelled. Vane 14d will alter its state from free to hold at the point where the net torque (sum of the individual torques as result of lift, drag, inertia, gravity, and reaction) about the axis of the cord 12d becomes zero (meaning no rotation about the cord 12d). During rotation, each vane 14 cyclically alters its state between hold and free owing to changes in the net torque about the axis of the cord 12, corresponding to an imaginary line that connects the opposing coupling points of the cord 12.

Fig. 2B shows the system 2 facing a fluid flow vector normal to and into the page.

This view demonstrates an advantage of the self-steering vanes 14. As can be seen, while to the right of the mast 4 the projection of the area of the vane 14b in the flow 40 direction is maximal, to the left of the mast 4 the projection of the area of the vane 14d in the flow 40 direction is minimal. This is explained by the fact that for the right-hand vane 14b, the repulsive force between the reactive elements opposes the wind force thereby preventing or at least impeding rotation of the vane about the cord 12. Consequently, the vane 301684/3 assumes an equilibrium disposition where its surface is substantially normal to the direction of the wind. On the other hand, for the left-hand vane 14d, the repulsive force between the reactive elements acts in concert with the wind force thereby rotating the vane about the cord 12 such that its surface is substantially parallel to the direction of the wind. Since the power generated by the fluid flow is proportional to the projection of the area impacted by the wind, the system 2 will not only harvest more energy from the fluid flow 40 on the right side but will also significantly reduce the energy loss on the left side.

For completeness, we will describe alternative forms of interaction between the reactive elements 16 and 18. For clarity, no distinction is made between each pair of reactive elements, the only requirement being that they are mutually complementary. It will also be understood that opposing vanes operate in a mutually opposed manner, whereby one vane is active and contributes to power generation while the other is inactive and plays no part in the current generation cycle. These two vanes will exchange their functionalities during every half-revolution (180) of the mast. The following description relates to operation of the active vanes only. a. A controlled attractive force can be achieved by forming one of the reactive elements of a ferromagnetic material and its complementary reactive element being an electromagnet. The electromagnet can be controlled by a controller (constituting a first controller, not shown) that may be triggered by proximity sensor switches (not shown) that are configured to turn the electromagnet ON when the vane 14 rotates within range of the complementary reactive element thereby maintaining the vane in the hold state, and OFF when the vane 14 has accomplished its power generating function for the current cycle.

For the complementary inactive vane, the attractive force between its respective reactive elements is deactivated to allow the vane to rotate into the free state as shown in Fig. 7B.

It will be appreciated that other sensors may be used to trigger or activate the controller.

For example, an angular encoder can be used to provide a measure of angular rotation relative to a predetermined origin, the controller being responsive to the encoder signals for energizing or de-energizing the reactive elements. b. Alternatively, a controlled repulsive force can be achieved by forming one of the reactive elements of a permanent magnet and its complementary reactive element being an electromagnet controlled by a first controller responsive to sensors as explained above. 301684/3 c. A controlled attractive or repulsive reactive force can be achieved by interaction between a reactive element formed of a permanent magnet and an electromagnet controlled by a controller in like manner. The controller is responsive to sensor signals for changing the polarity of the electromagnet during the hold state, thereby increasing the power generation efficiency of the system 2 by controlling the duration of the hold state relative to duration of the free state. As in the previous configuration, during the free state the electromagnet will be switched to OFF; however, during the hold state the interaction between the reactive elements can start with a repulsive polarity and then be switched to the attractive polarity to delay the timing of the state switching from hold to free.

The mast 4 can either be rotatable, as shown in Figs. 1A, 1B, 2A, 2B, 3A and 3B, or static, as shown in Fig. 4.

If the mast 4 is rotatable (Figs. 1A, 1B, 2A, 2B, 3A and 3B), the rotors 8 and 10 are rigidly coupled to the mast 4, which is configured to rotate in a support structure 6 carried by a shaft 28 that is supported in bearings 30 (Figs. 3A and 3B) and driving a power converting device 22 either directly (Figs. 3A and 3B) or via transmission gears (Fig. 1B).

The support structure 6 may be coupled to a building, to ground or to a mobile platform or static structure (not shown).

Fig. 4 shows a system 2 for power generation, according to another embodiment of the invention. In this configuration, the system 2 is of cylindrical shape and the mast 4 is static. The first rotor 8 and the second rotor 10 are configured to rotate about the mast 4 supported by bearings 32 and the mast is rigidly coupled to a support structure 6. The second rotor 10 drives a power converting device 22 via transmission gears 20.. The power converting device 22 may be an electric generator, pump, or a mechanically driven device.

To prevent overload of the system 2 under extreme conditions, such as extreme rotational speed or an extreme fluid flow 40, for example in harsh weather conditions, the system 2 can be switched into idle mode which prevents all the vanes 14 from entering the hold state. An idle mode can be realized by reducing the force between the reactive elements 16 and 18 either by weakening the magnetic field strength of either or both elements, or simply by increasing the distance between them. The distance between the 301684/3 reactive elements 16 and 18 can be controlled by a retraction mechanism (constituting a second controller), such as a retraction arm 34 as shown in Fig. 4 and in cross-section in Figs. 5A and 5B, or by any other suitable retraction mechanism. The retraction arm 34 is rotatable about the shaft 35 (Fig. 5A) and can be retracted by a centripetal force on the arm 34 being a function of the rotation velocity, by a spring 36 or by a repulsive force between the reactive elements 16 and 18. To switch the system 2 from the idle mode back to the power generation mode, the retraction arm 34 can be brought back into the power mode initial position (Fig. 5B) by a gravity force of an arm 34 or by a control cable 37 extending longitudinally through an inner bore of the mast 4 and configured to pull down the retraction arms 34 via a thrust bearing 38. To control the reactive forces dynamically, the retraction arms 34 after being retracted by the springs 36 can be reverted to the power mode by a servo motor 39 operatively coupled to the control cable 37 (Fig. 5B) for pushing the arms 34 down via the central thrust bearing 38.

If the force of the reactive elements 16 and 18 is adjusted to a threshold value, as explained above, by being configured to create a weaker force, either by increasing their mutual separation, or by reducing their magnetic field strengths, or by reducing the current running through the electromagnet, in extreme conditions when the wind power is beyond the force threshold, the reactive force between the elements 16 and 18 will no longer be sufficient to retain the vanes 14 and therefore the vanes 14 will rotate past the respective reactive elements 16 and will prevent an overload of the system 2. The threshold force can be calculated as described above.

If the reactive elements 16 are fully retracted by the retraction arms 34 to the idle mode, the vanes 14 will be unable to interact with the reactive elements 16. Consequently, they will be unable to enter the hold state, and all the vanes 14 will be steered by the fluid flow 40 to a downstream position, as shown in Fig. 4.

It should be noted that partial retraction of the reactive elements 16 will allow control over the reactive force and thereby over the peak power generated by the system.

Although the vanes 14 illustrated in the Figs. 1A to 5B are of a planar shape, it will be understood that they may also be of other forms, such as blade, wing, or sail, and they may be made of rigid, flexible, or combined materials.

Figs. 6A and 6B illustrate vanes 14 having the form of a wing. The cross-section of the wing may be symmetric about a vertical axis as shown in Fig. 6A, but alternatively 301684/3 it may be asymmetric (not shown). The connection between the wing-shaped vanes 14 and the coupling points on the rotors 8 and 10 can be effected either by a cord 12 fixedly attached to the rotors 8 and 10 and rotatably coupled to the element 14 or by a cord 12 fixedly attached to the element 14 and rotatably coupled to the rotors 8 and 10 as shown schematically in Fig. 6B.

Fig. 7A shows a vane 14 made of a sail cloth of triangle shape. One edge of the vane 14 is tied via attachment points 50 to a boom 52 while the second edge of the vane 14 is tied via the attachment points 50 to the cord 12, either directly or via rotary joints 54 rotatably attached thereto as shown in Fig. 7A. The boom 52 is attached to the lower end of the cord 12, either directly or via the rotary joint 54 rotatably attached thereto and supports a reactive target 18. Rotation of the vane 14 about the axis of the cord 12 may be configured in two ways: cord 12 is fixedly connected to the rotors 8 and 10 via the coupling points and the vane 14 with the boom 52 rotate about the cord 12 via the rotary joints 54, or the cord 12 is rotatably coupled to the rotors 8 and 10 via the coupling points and the sail constituted by the vane 14 together with the boom 52 are fixedly connected to the cord 12. These two configurations are equally applicable to any other form (blade, wing, or sheet) of the vane 14.

It should be noted that each vane may carry more than one reactive element 18 which interacts with an equal number of complementary reactive elements 16 supported by any one or more of the first rotor 8, the second rotor 10 and the mast 4.

It should further be noted that the cord 12 can be chosen from any of the following groups: cables, ropes, wires, rods, bars, and they may be made of rigid or flexible material.

Moreover, the cords 12 can be an independent component, as shown in Fig. 1A, or can be combined with the vanes 14 into a single structure, as shown in Fig. 6B.

It should also be noted that the system 2 is not limited by dimensions, scale, geometry, or shape. The shape of the system may be conical, with a base facing either up or down (Figs. 1A, 1B, 2A, 2B, 3A and 3B), cylindrical (Fig. 4), or any other shape that meets the functionality or the purpose of the system 2.

To understand operation of the system 2 operating as a wind turbine, the method of energy generation will now be explained. Fig. 1B shows the system 2 in calm weather (i.e., with substantially zero wind force), during which the vanes 14 are subject solely to the influence of gravity and the reactive force. Due to these forces, the position that all 301684/3 the vanes 14 will adopt is as shown in Fig. 1B – generally directed towards the center of the mast 4 while being slightly deflected off-center due to the repulsive magnetic force between the reactive elements 16 and 18. The vanes 14 can be arranged to be deflected in a clockwise direction as seen from above (Fig. 1B) or in a counterclockwise direction (not shown). The rotation of the rotors 8 and 10 about the axis of the mast 4 will be in a direction opposite to the direction of the deflection: if the vanes are deflected in a clockwise direction as seen from above (as shown in Fig. 1B), the rotors 8 and 10 will rotate in a counterclockwise direction, and vice versa.

Fig. 7B shows a plan view of the system 2 rotating in a counterclockwise direction while subjected to the fluid flow 40. As can be seen, vanes 14a and 14b that are moving with the flow (general direction), are not able to rotate about the cords 12 owing to the repulsive force between the reactive elements 16 and 18 when in close mutual proximity.

In this situation, under the lift and drag forces, the vanes 14a and 14b are in a hold state and turn the rotatable components of the system 2 about the axis of the mast 4, while generating power. At the same time, the vanes 14c and 14d move against the flow (general direction) in a free state and rotate about the axis of the cords 12, while steering away from the reactive elements 16 due to the fluid flow 40. While the orientation of the vanes 14a and 14b that are moving with the flow 40 in the hold state is such as to bring their lift and drag forces to maximum, the orientation of the vanes 14c and 14d that are moving against the flow 40 in a free state is such as to bring their drag forces to minimum. As a result, energy losses of the system 2 are reduced and the efficiency of the power generation is increased. Rotational energy harvested from the fluid flow 40 is driven either directly (Figs. 3A and 3B) or indirectly (Figs. 2A and 2B), via transmission gears , and fed to an energy converting device 22 that may be an electric generator, pump, or a mechanically driven device.

During the rotation each of the vanes 14 cyclically alternates between the hold state and the free state, driven by the fluid flow. The segment of the hold state together with the segment of the free state (Fig. 7B) create 360 degrees turn. The concept of operation of the two-state (hold and free) turbine generator is such that it does not depend on the direction of the flow. 301684/3 It should be noted that the orientation of the system 2 is not limited to a vertical one only. Other orientations of the system, such as horizontal, tilted, upside down and others, are applicable as well.

It should also be noted that the vanes 14 can be designed to be steerable and switchable between the hold and the free states using electric motors (not shown), which can be stepper motors or servo motors. The motors can be controllable by a controller (constituting a third controller not shown) that is triggered by proximity sensor switches or other sensor signals as described above (not shown) and dynamically adjusted based on measurements of fluid flow power and direction (made by an anemometer in the case of wind).

It will be appreciated that although reference is made to first, second and third controllers, their functionalities may be combined and may optionally be implemented by a suitably programmed computer.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the scope of the appended claims. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims rather than by the foregoing description.

Claims (24)

301684/ - 15 - CLAIMS:

1. A system for energy generation, the system comprising: a mast adapted for coupling to a support structure; a first rotor located toward a first end of the mast and being rotatable about a longitudinal axis of the mast; a second rotor located toward a second end of the mast and being rotatable about said axis; at least two vanes coupled to the first rotor and to the second rotor via respective coupling points, each vane being independently rotatable about a respective line joining the coupling points under force of a fluid directed to the system; and a pair of contactless reactive elements associated with each vane and configured to mutually co-operate to apply a respective reactive force whereby the fluid force acts in concert with the reactive force acting on at least one vane and opposes the reactive force acting on at least one different vane.

2. The system as claimed in claim 1, wherein at least one of the first rotor or the second rotor supports at least two reactive elements configured to interact with the vanes to create reactive forces when in proximity to said reactive elements.

3. The system as claimed in claim 1 or 2, wherein the first rotor and the second rotor are rigidly coupled to the mast and the mast is configured to rotate in a support structure and to drive, directly or via a transmission, a power converting device.

4. The system as claimed in claim 1 or 2, wherein the first rotor and the second rotor are configured to rotate about the mast and the mast is rigidly coupled to a support structure, while the first or second or both rotors are configured to drive, directly or via a transmission, a power converting device.

5. The system as claimed in claim 3 or 4, wherein the power converting device is an electric generator, a pump, or a mechanically driven device. 301684/ - 16 -

6. The system as claimed in any one of the preceding claims, wherein each pair of contactless reactive elements includes a first element formed of a ferromagnetic material or a permanent magnet and a second element formed of a permanent magnet.

7. The system as claimed in claim 6, wherein the reactive force between each pair of reactive elements is repulsive or attractive.

8. The system as claimed in any one of the claims 1 to 5, wherein each pair of contactless reactive elements includes a first element formed of a ferromagnetic material or a permanent magnet and a second element formed of an electromagnet.

9. The system as claimed in claim 8, wherein the reactive force between each pair of reactive elements is fixedly or controllably repulsive or attractive.

10. The system as claimed in claim 8 or 9, further including a first controller configured to adjust the reactive force, said first controller being configured to energize the electromagnet so as to interrupt rotation of the vane during a hold state, and to de-energize the electromagnet when the vane has completed a power generation cycle.

11. The system as claimed in any one of the preceding claims, wherein the vanes are selected from any of the following: blades, wings, sails, or sheets.

12. The system as claimed in any one of claims 1 to 11, wherein the vanes are configured to be steerable by the fluid flow.

13. The system as claimed in any one of claims 1 to 11, wherein the vanes are configured to be steerable by an electric motor.

14. The system as claimed in any one of the preceding claims, wherein during rotation, each vane exhibits a hold state wherein the reactive elements associated with the vane are sufficiently close to co-operate and a free state wherein the reactive elements associated with the vane are too far apart to co-operate. 301684/ - 17 -

15. The system as claimed in any one of the preceding claims, further including a second controller configured to prevent overload of the system under excessive fluid force by actuating an electromagnetic reactive element or a retraction mechanism.

16. The system as claimed in claim 15, wherein the second controller is configured to control power generated by the system by adjusting current of the electromagnet reactive element or by partial retraction of the retraction mechanism.

17. The system as claimed in any one of the preceding claims, wherein the vanes are coupled to the rotors via respective cords anchored between the coupling points.

18. The system as claimed in claim 17, wherein each vane and its respective cord form a unitary structure.

19. The system according to any one of the preceding claims being a two-state turbine.

20. A method for generating energy, the method comprising: directing a fluid force against a rotatable structure comprising a mast and at least two vanes each configured to rotate about a respective vane rotation axis, whereby during a complete cycle of rotation the fluid force impinges against different ones of the vanes causing the structure to rotate about the mast; and associating with each of the vanes, respective pairs of contactless reactive elements wherein the reactive elements in each pair are configured to mutually co-operate to apply a respective reactive force whereby the fluid force acts in concert with the reactive force acting on at least one vane and opposes the reactive force acting on at least one different vane.

21. The method as claimed in claim 20, including adjusting the reactive forces to avoid an overload of the system under extreme rotational speeds or fluid flow.

22. The method as claimed in claim 20 or 21, including adjusting the reactive forces to control power generated by the system. 25 301684/ - 18 -

23. The method as claimed in claim 21, wherein one of the reactive elements in each pair is an electromagnet and the method further includes electrically adjusting a field strength of the electromagnet to avoid an overload of the system under extreme rotational speeds or fluid flow.

24. The method as claimed in any one of claims 20 to 23, wherein the fluid is wind.