Field of the disclosure

The present disclosure generally relates to a wind-powered generator system, for example, a vertical-axis wind turbine (VAWT) system. Background of the disclosure

Wind is a form of renewable energy source. In harnessing wind power, movement of air is translated to rotational kinetic energy of a wind turbine, which in turn drives a power generator to produce electrical energy. Wind turbines are therefore mechanically coupled to their associated power generators. As wind speed changes, the rotational speed of the wind turbine changes accordingly. Dangerously high wind speed therefore has the potential to damage the power generator.

Summary of the disclosure

According to the present disclosure there is provided a wind-powered generator system including: a wind-rotatable member configured to rotate about a rotational axis substantially perpendicular to a wind direction; a power-generator configured to engage the wind-rotatable member and to generate power based on rotation of the wind-rotatable member; and an aerodynamic member configured to generate lift in response to wind, the lift being in a direction along the rotational axis and designed to, responsive to wind speed, vary the engagement between the wind-rotatable member and the power- generator.

The system may further include magnetic coupling means configured to facilitate the variable engagement between the wind-rotatable member and the power- generator. The aerodynamic member is configured to at least partially disengage the wind -rotatable member from the power-generator beyond a threshold wind speed. The variable engagement may vary continuously or near continuously responsive to the magnitude of the lift. The wind-rotatable member includes a first array of magnetic elements, and the power-generator includes a second array of magnetic elements, the first and second arrays arranged in the direction of the lift in a magnetically slipping arrangement.

The variable engagement may facilitate a substantially constant rotating speed of the power-generator. The variable magnetic coupling may be configured to, responsive to changes in the wind speed, allow corresponding changes in speed of the wind-rotatable member to facilitate the substantially constant rotating speed of the power-generator.

The system may further include an enclosure for housing the wind-rotatable member, the enclosure including an air inlet for allowing incoming wind to rotate the wind-rotatable member, an air outlet for allowing outgoing wind to leave the enclosure, perforations to facilitate drag reduction on the wind-rotatable member. The wind- rotatable member may include one or more blades, each movable along the wind direction during a first part of a rotational cycle and movable against the wind direction during a second part of the rotational cycle, and where the perforations are located within one part of the enclosure corresponding to the second part of the rotational cycle.

Further aspects of the present disclosure and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings. Brief description of the drawings

Figure 1 illustrates a wind-powered generator system in accordance with this disclosure. Figure 2 illustrates a top view of a wind-rotatable member in Fig. 1 in an enclosure.

Figure 3 illustrates air flow paths inside and outside the enclosure of Fig. 2.

Figure 4 illustrates a perspective view of the wind-rotatable member 2 of Fig. 2 in the enclosure.

Figure 5 illustrates a schematic diagram of magnetic coupling between the wind-rotatable member 2 and the power-generator.

Detailed description of embodiments

Described herein is a wind-powered generator system. While the disclosure herein relates to a vertical -axis wind turbine (VAWT), a skilled person would appreciate that, with minor modifications, the disclosure is applicable to a horizontal-axis wind turbine (HAWT).

Figs. 1 and 2 illustrate a wind-powered generator system 100. The disclosed system 100 includes a wind-rotatable member 2, a power-generator 28 configured to engage the wind-rotatable member 2 and to generate power based on rotation of the wind-rotatable member 2. The wind-rotatable member 2 is configured to rotate about a rotational axis 3 substantially perpendicular to a wind direction 6. The system 100 includes an aerodynamic member 10 (hereinafter “airfoil” for simplicity) configured to generate lift in response to wind, the lift being in a direction 10a along the rotational axis 3 and designed to, responsive to wind speed, vary the engagement between the wind-rotatable member 2 and the power-generator 28. In some arrangements, the lift is configured to at least partially disengage the wind-rotatable member 2 from the power- generator 28 beyond a threshold wind speed.

In the illustrated system 100, the wind-rotatable member 2 is configured to rotate around the rotational axis 3 on a shaft 8. The wind-rotatable member 2 is housed in an enclosure 4. The enclosure 4 is of a cylindrical shape, accommodating the rotation of the wind-rotational member 2. The wind-rotational member 2 includes one or more blades or sails 7, each extending from the shaft 8. The enclosure includes an air inlet 1 and an air outlet 5. The inlet 1 allows incoming wind to rotate the wind-rotatable member 2. The outlet 5 allows outgoing wind to leave the enclosure 4.

In one arrangement, as illustrated in Fig. 3, when viewed from above, the wind-rotatable member 2 is configured to rotate in the clockwise direction. The one or more blades or sails 7 each include a curved portion 7a to define an air reservoir region for facilitating the receipt, or otherwise concentration, of moving air particles entering the enclosure 4 via the inlet 1. The one or more blades or sails 7 may be constructed with elastic fabric tightly stretched, e.g. from top to bottom. In the case of the elastic fabric construction, the curved portion 7a may be formed by stretching of the fabric in response to the wind imparting a force on the fabric. The fabric may be coated fabric to increase its rigidity and to avoid additional stretching of the fabric over time. The use of fabric reduces the weight of the blades or sails compared to using other materials. The entered air particles carried by the incoming wind impart forces along or in accordance with the wind direction 6 on the one or more blades or sails 7 to rotate the wind- rotatable member 2. The entered air particles travel from the inlet 1 to the outlet 5 by moving each blade or sail 7 for part of its rotational cycle (i.e. the “downwind” part cycle along an inside path 6a from the inlet 1 to the outlet 5). The “downwind” part cycle (and similarly the “upwind” part cycle below) is defined by the angular separation between the inlet 1 and the outlet 5, and may be but need not be exactly a half of the rotational cycle. For example, the downwind cycle may span 170 degrees when the air traverse the inside path 6a, while the upwind cycle may span 190 degrees when the air traverse the rest of the cycle. Compared to air particles travelling around the outside of the enclosure 4 along an outside path 6b from near the inlet 1 to near the outlet 5, the air particles travelling along the inside path 6a travel a shorter distance over the same amount of time, hence at a lower velocity and a lower fluid pressure at the outlet 5. The lower fluid pressure causes most air particles entered at the inlet 1 to exit the enclosure 4 when reaching the outlet 5. There are no or few air particles moving any blade or sail for the other part of its rotational cycle (i.e. the “upwind” part cycle from the outlet 5 to the inlet 1). In other words, each blade or sail 7 is movable along or in accordance with the wind direction 6 during a first part 6a of a rotational cycle and movable against or in contrary to the wind direction 6 during a second part of the rotational cycle.

In one arrangement, as illustrated in Fig. 4, the airfoil 10 includes a pair of guides 1 la and 1 lb to guide the lifting direction 10a of the airfoil 10. The airfoil 10 is mechanically coupled to the shaft 8 of the wind-rotatable member 2 via a mechanical member (e.g. a rigid push-pull rod) 9. In one arrangement, the shaft 8 includes a bore for slidably receiving the mechanical member 9. In this arrangement, the mechanical member 9 is free to move up and down with no connection to the shaft 8. The lift 10a experienced by the airfoil 10 causes the mechanical member 9 to pull the shaft 8 upwards. Conversely the system 100 includes a biasing member 17 for causing a counteracting downward force on the airfoil 10 by pulling the shaft 8 downwards. The downward force is configured to increase in accordance with extension of the biasing member 17 caused by a corresponding extension of the mechanical member 9 responsive to the lift 10a. The downward force and the lift 10a counteract each other to maintain the airfoil 10, and hence the shaft 8, at a height in accordance with the wind speed. The enclosure 4 may include a vane 14 to orientate the enclosure 4 such that the inlet 1 and/or outlet 5 is/are aligned in accordance with the wind direction 6.

In one arrangement, as illustrated in Fig. 4, the enclosure 4 includes perforations 13 to allow air communication between the air inside and the air outside the enclosure 4. The air communication is configured to facilitate drag reduction on the wind-rotatable member 2. In the illustrated enclosure 4, the perforations 13 are located within one part (e.g. approximately one half) of the enclosure 4 corresponding to the upward part cycle of the rotational cycle of the one or more blades or sails 7. The perforations 13 located as such allow air not having exited the outlet 5, and hence trapped inside the enclosure 4 between blades or sails during the upwind part cycle, to escape from the inside to outside the enclosure 4. The escape is further facilitated by the lower air pressure outside the enclosure 4 compared with the higher air pressure inside the enclosure 4. The air pressure differential therefore facilitates the escape of the trapped air during the upwind part cycle. The escape in turn reduces drag on the wind- rotatable member 2. A skilled person would appreciate that the perforations 13 need not be distributed over the entire part of the enclosure 4 corresponding to the upward part cycle. Further, a skilled person would appreciate that the perforated arrangement may be applicable to wind-powered generator systems that do not necessarily require the presence, mechanism or features (e.g. airfoil 10 etc) directed to the at least partial disengagement between the wind-rotatable member 2 and the power generator 28.

In one arrangement, as illustrated in Fig. 1, the system 100 further includes magnetic coupling means 500 configured to magnetically engage the wind-rotatable member 2 with the power-generator 28. Similarly, the magnetic coupling means 500 may be configured to at least partially magnetically disengage the wind-rotatable member 2 from the power-generator 28. A skilled person would appreciate that, in the context of magnetic coupling, disengagement is strictly only partial disengagement. Magnetic coupling between two separating magnetic elements continue to exist unless the two magnetic elements are separated by an infinite distance. In practice, however, two magnetic elements may be considered disengaged if the magnetic coupling therebetween reduces to a negligible level to have practical effect. The magnetic coupling means 500 is configured to vary magnetic coupling between the power- generator 28 and the wind-rotatable member 2. The magnetic coupling means may be a magnetic torque coupler, which includes a rotor (i.e. torque transmitter) and translator (i.e. torque receiver) variably separable in space from the rotor. The level of torque coupling therebetween depends on their separation. For smaller separation, the rotor and the translator are arranged to rotate in closer synchronisation with each other (e.g. more similar rotational speed). For larger separation, the rotor and the translator are arranged to rotate in less synchronisation with each other (e.g. less similar rotational speed). In the disclosed system 100, the rotor and the translator are configured to slip on separation responsive to the lift 10a on the airfoil.

For example, as illustrated in Fig. 5, the magnetic coupling 500 includes a first array 502 of magnetic elements rotatably coupled to the wind-rotatable member 2 (which is in turn coupled to the wind-rotatable member 2) and a corresponding second array 504 of magnetic elements rotatably coupled to the power-generator 28 and variably separated in space from the first array 502. In one arrangement, the first array of magnetic elements is located on a first toroid or drum 25, whereas the second array of magnetic elements is located on a first toroid or drum 30. The different magnetic elements (such as on different rows) of each of the arrays 502 and 504 may have a different magnetic strength. In one arrangement, the magnetic strength of the arrays may be arranged to initially increase from an outermost row and then decrease away from the outermost row. For example, in array 504, an uppermost row of magnet elements may be arranged to be relatively weak (e.g. at an equivalent strength of N35) to facilitate a correspondingly low threshold wind velocity (e.g. ~ 1 m/s). The second uppermost row of magnet elements may be relatively strong magnets (e.g. N52), with the third and subsequent uppermost rows being of decreasing strength (e.g. N50, N48, N45, N42, N40 and N35). In one arrangement, the number of the magnetic elements within each row may be varied to adjust the magnetic coupling (hence the coupling force) between the rotor and the translator according to the expected wind speed in order to facilitate a substantially constant rotating speed of the power-generator 28. In another arrangement, applicable to areas with high wind speed, the magnetic elements are located on cones instead of using toroids or drums. The above description relating to the toroid / drum arrangement is also, with minor modifications, applicable to the cone arrangement. In yet another arrangement, the magnetic elements are located on a combination of cones and toroids or drums. The variable separation is achieved by the two arrays being slidably movable relative to each another In the illustrated arrangement, the second array 504 is fixed, while the first array 502 may be moved up and down in accordance with the magnitude of the lift 10a on the airfoil 10. The first array 502 (akin to the rotator) and the second array 504 (akin to the translator) are configured to enable torque transfer from the wind- rotatable member 2 to the power-generator 28. While the illustrated arrangement shows variably separated arrays as side-by-side, the variably separated arrays may alternatively be face-to-face or concentric. As the magnitude of the lift 10a increases, the first array 502 the torque transfer decreases (and vice versa). Accordingly, the variable magnetic coupling is responsive to a magnitude of the lift 10a experienced by the airfoil 10. In one arrangement, the magnetic coupling is configured to vary continuously or near continuously responsive to the magnitude of the lift. For example, as illustrated in Fig. 1, the biasing member 17 includes a resilient member 20 (hereinafter a spring). The stiffness of the spring 20 influences the restoring force counteracting the lift 10a, in turn influencing to the vertical position of the shaft 8 and hence the separation of the first array 502 of magnetic elements from the second array 504 of magnetic elements. The spring 20 may therefore be able to be configured to allow the variable magnetic coupling to, responsive to changes in the wind speed (which causes changes in the lift 10a), facilitate a substantially constant rotating speed of the power-generator 28. In one arrangement, as illustrated in Fig. 1, the biasing member 17 further includes a pneumatic chamber 22 to facilitate a linear motion of the shaft 8 and the second array 504 of magnetic elements. Nonlinearity may be caused by any one of more of: a non-linear response of the airfoil, changes in ambient temperature, and changes of barometric pressure, which is in turn dependent on weather and geographic locations. In this arrangement, the spring 17 and the pneumatic chamber 22 are separated by separator 21. The separator 21a is a fixed partition. The separator 21a limits the spring 17 when it is moved by a movable separator 19, pushed up by a plug 16 installed on a threaded rod 24 while the rod 24 is pulled up by the airfoil 10. The movable separator 19a may also be urged by the plug 16a , when the ambient temperature decreases or barometric pressure increases. The plug 16a is configured to push up the movable separator 19a and decouple the magnetic coupling to compensate for the increased rotational speed of the power-generator 28 due to air density increased by temperature and barometric pressure. The biasing member 17 includes air openings 23 for compressed air, a valve 15 to pressurize the pneumatic chamber 22 via a duct (not labelled), a plug 16 for an opening 18 through which the base 19 of the spring 20 is held in position. The biasing member 17 includes a sealed joint for the duct (not labelled) and the mechanical member 9. The biasing member 17 is coupled to the second array 502 of magnetic elements located on the toroid 25 which is supported on a support 26. The magnetic field of the second array 502 of magnetic elements can be intensified via inclusion of a ferrite rod 27. Now that arrangements of the present disclosure are described, it should be apparent to the skilled person in the art that at least one of the described arrangements have the following advantages:

• The use of an aerodynamic member 10 generating lift facilitates aerodynamic disengagement of the power generator 28 from the wind- rotatable member 2 beyond a threshold (e.g. dangerously high) wind speed, avoiding the use of mechanical brakes.

• The use of perforations 13 located within the part of the enclosure 4 corresponding to the upwind part cycle of the blades or sails 7 assists with drag reduction of the wind-rotatable member 2 in, for example,

VAWT systems.

• The magnetic coupling means 500 for continuously or near continuously coupling between the power generator 28 and the wind- rotatable member 2 allows for a constant or near constant rotational speed of the power generator 28.

• A lower cut-in wind velocity may be achieved so as to generate power at a correspondingly lower level.

It will be understood that the disclosure disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the disclosure.