Patent Application
20100034636
The present invention generally relates to a stabilizing apparatus for vertical axis wind turbine (VAWT), and more specifically to an apparatus for automatically changing rotational inertia of the wind turbine rotor to reduce the vibration and shaking of wind turbine rotor caused by turbulence during rotation, and to achieve low wind speed start and to stabilize and maintain the rotor rotation speed.
Vertical axis wind turbine (VAWT) uses the wind turbine rotor with multiple blades and an axis perpendicular to the ground. The main advantage of VAWT is that VAWT can extract energy of wind streaming from any directions; therefore, VAWT performs better in turbulence than horizontal axis wind turbine (HAWT).
Wind turbine rotor is one of the most important components of VAWT. The blade geometry of the wind turbine rotor will directly affect the power efficiency of VAWT. The wind turbine rotor with higher rotational inertia is better at reducing the shaking and vibration of the wind turbine rotor caused by the turbulence while requiring a higher wind speed and torque for starting and activating. On the other hand, the wind turbine rotor with lower rotational inertia is easily affected by turbulence on the rotation stability while the advantage is easy to activate.
The theoretic value of the equivalent rotational inertia is
or I=MR2, where M is the mass of wind turbine rotor, and R is the radius of the wind turbine rotor.
Therefore, to increase the rotational inertia of the wind turbine rotor can be achieved by increasing the mass or the radius of the wind turbine rotor. However, VAWT needs a higher start-up wind speed for the wind turbine rotor with bigger mass. And, to increase the radius of wind turbine rotor will cause constraint to VAWT products design for applications. Therefore, it is imperative to devise a stabilizing apparatus to be used with the original design and structure of wind turbine rotor so as to automatically change the rotational inertia of the wind turbine rotor to achieve the objectives of requiring a lower start-up wind speed, and maintaining and stabilizing the rotor rotation speed.
The primary objective of the present invention is to provide a stabilizing apparatus for vertical axis wind turbine (VAWT). The apparatus is installed on the same axis as the wind turbine rotor of the VAWT, and the two rotate synchronously around the same axis. The main feature of the apparatus is that the rotational inertia of the apparatus can be changed by rotor speed. The apparatus includes a plurality of ball units. The ball units can move from the center outward to the circumference of the apparatus due to the centripetal force caused by the rotation of the apparatus. Therefore, when the apparatus starts rotated by the wind, the distance between the ball units and the center of the rotation axis increases; hence, the rotational inertia of the apparatus is increased. Because the apparatus and the wind turbine rotor can be integrated together and rotate synchronously, the overall rotational inertia of the wind turbine rotor is also changed accordingly. When the rotation speed of wind turbine rotor is increasing, the rotational inertia of rotor system is also increasing until the ball units are all on the brink of the circumference of the apparatus to obtain a maximum rotational inertia of rotor system, so as to achieve the objectives of reducing the vibration and shaking of wind turbine rotor caused by turbulence during rotation, and maintaining and stabilizing the rotor rotation speed.
Another objective of the present invention is to provide a stabilizing apparatus having a wide range of applications. Because the apparatus of the present invention is capable to automatically change the rotational inertia without changing the original design and structure of the wind turbine rotor of the VAWT when the wind turbine rotor rotates, the apparatus of the present invention is easier to be integrated with the current wind turbine rotor of VAWT.
Yet another objective of the present invention is to provide a stabilizing apparatus to be installed at the top, bottom, or the shaft body between the top and the bottom of wind turbine rotor. The present invention can also be installed and integrated between two wind turbine rotors when a plurality of wind turbine rotors are stacked so as to obtain higher torque.
To achieve the above objectives, the present invention provides a stabilizing apparatus for VAWT, including a plurality of ball units and at least a guiding unit. The ball units are balls with proper weight, such as metal balls. The guiding unit has a circular cross-section and has a ring-shaped housing space formed inside the guiding unit. The ball units are housed inside the ring-shaped housing space of the guiding unit. The inner wall of the bottom of the ring-shaped housing space inside the guiding unit forms a ring-shaped guiding surface. The ring-shaped guiding surface extends from the center of the apparatus towards the brink of the circumference of the apparatus. The straight line connecting the edge of the inner circle and the edge of the outer circle of the ring-shaped guiding surface forms an angle of 0-45° to the horizon surface. When the apparatus starts rotated with wind turbine rotor by wind, the ball units are closer to the center initially; therefore, rotor system having a smaller rotational inertia and requires a lower wind speed to start the rotation. When the rotation speed increases, the ball units are moved by the centripetal force so that the rotational inertia also increases and the wind turbine rotor can rotate more stably.
The foregoing and other objectives, features, aspects and advantages of the present invention will become better understood from a careful reading of a detailed description provided herein below with appropriate reference to the accompanying drawings.
The present invention can be understood in more detail by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:
The following describes the components of the present invention in details.
Guiding unit 20 is a disk with a certain height and has a circular lateral cross-section. Guiding unit 20 has a circular cross-section and has a ring-shaped housing space 21 formed inside. The inner wall of the bottom of ring-shaped housing space 21 inside guiding unit 20 forms a ring-shaped guiding surface 22. Ring-shaped guiding surface 22 extends from the center of apparatus 100 towards the brink of the circumference of apparatus 100. The straight line connecting the edge of the inner circle and the edge of the outer circle of ring-shaped guiding surface 22 forms an angle α of 0-45° to the horizon surface. However, ring-shaped guiding surface 22 can be of a plurality of different forms. The following describes some of the embodiments of ring-shaped guiding surface 22 used in the present invention. Firstly, ring-shaped guiding surface 22 can be a ring-shaped flat surface. In this case, the angle α is 0°. Secondly, ring-shaped guiding surface 22 has a shape of an upside-down cone with the vertical cross-section view of two symmetrical slant lines. In this case, the angle between the slant lines and the horizon surface is 0-45°. Thirdly, ring-shaped guiding surface 22 is an upside-down cone with a vertical cross-sectional view of two symmetrical curves monotonically increasing from the center edge towards the outer edge. Therefore, the curve can be of any shape, such as arc. Fourthly, the vertical cross-sectional view of ring-shaped guiding surface 22 consists of a plurality of segments, with each segment not necessarily the same. However, the cross-section of each segment must be of symmetrical straight lines, slant lines or curves. The present embodiment uses the aforementioned fourth form. As shown in
Furthermore, guiding unit 20 includes a ring wall 23 close to the center. Ring wall 23 has an axis hole 24 for installing an axis 30. When apparatus 100 of the present invention is assembled with the wind turbine rotor of VWAT, apparatus 100 shares axis 30 with the wind turbine rotor. In the present embodiment, the bottom view of guiding unit 20 has the same shape as the shape of inside ring-shape guiding surface 22, but is not limited to the details described thereof. The shape of guiding unit 20 can be designed to meet the requirements of the wind turbine rotor used with the VAWT.
The above embodiment with actual applications shows the apparatus of the present invention with a single guiding unit. However, the present invention can also include two or more guiding units in the design, as shown in the following embodiment.
In summary, when a plurality of guiding units are included, the plurality of guiding units can be engaged together as concentric rings, with the next guiding unit as the outer ring of the previous guiding unit. Each guiding unit forms an independent ring-shaped housing space with a ring-shaped guiding surface to house a plurality of ball units inside. In this manner, the overall structural strength of the apparatus is enhanced. Although the apparatus with a plurality of guiding units require a higher wind speed to start, the rotation inertia is also increased. Therefore, the apparatus with a plurality of guiding units is suitable for operation in an environment with stronger and yet unstable winds.
Although the present invention has been described with reference to the preferred embodiments, it will be understood that the invention is not limited to the details described thereof. Various substitutions and modifications have been suggested in the foregoing description, and others will occur to those of ordinary skill in the art. Therefore, all such substitutions and modifications are intended to be embraced within the scope of the invention as defined in the appended claims.
