Abstract:
A vertical-axis wind turbine for use with an electrical generator for producing power by converting the energy of wind currents into mechanical rotational energy which is then used to operate the electrical generator. In an embodiment, a rotor is responsive to wind currents by imparting rotation upon a central vertical shaft. Preferably, the rotor is designed with functional curved surfaces for efficient operation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 12/432,083, filed on Apr. 29, 2009, which claims the benefit of Provisional Patent Application Ser. No. 61/125,865, filed Apr. 29, 2008. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates to wind turbines, and more specifically to a vertical-axis wind turbine used to convert wind energy into mechanical energy, and still more particularly to the incorporation of a novel turbine blade in a vertical-axis wind turbine. 
       BACKGROUND OF THE INVENTION 
       [0003]    Wind as a source of energy is a concept that has been promoted for some time. According to one source, there is evidence which shows that windmills were in use in Babylon and in China as early as 2000 B.C. The U. S. Patent and Trademark Office has granted patents on windmill devices dating back to the early to mid 1800&#39;s. 
         [0004]    Generally, in the art, wind turbines have either a vertical or horizontal axis. Typically, most or all of commercial wind turbines today are built with a propeller-type rotor on a horizontal axis (i.e., a horizontal main shaft) in order that they may face directly into a wind. It is generally known that most horizontal axis turbines built today are two or three-bladed, although some have fewer or more blades. The purpose of the rotor is to convert the linear motion of the wind into rotational energy that can be used to drive a generator. 
         [0005]    Worldwide interest in renewable energy options, however, has given rise to a significant increase in new wind turbine designs. Some of the most recent models on the market, therefore, are vertical axis wind turbines (“VAWTs”). Vertical-axis wind turbines are typically of a long axis type, allowing large columns of air to be harnessed. 
         [0006]    There exist two main types of VAWTs—the Savonius turbine which is a high speed, low torque turbine and the Darrieus turbine, which is a low speed, high torque turbine. Generally, the Darrieus turbine resembles an egg beater, where two vertically oriented blades revolve around a vertical shaft. Generally, the Darrieus models use an airfoil design so that a wind turbine airfoil essentially works in the same way as an airplane wing so that an airfoil has a flat side and a curved side. The result of air passing over the two sides is a force known as “lift.” When an airplane speeds down a runway, air passing on both sides of the airfoil wings, the lift force literally lifts the airplane into the air. This will continue as long as there is forward motion over the airfoil to generate the required lift. 
       SUMMARY OF THE INVENTION 
       [0007]    A system and method is provided for conversion of wind energy into rotational mechanical energy. In an embodiment, a wind turbine system is provided comprising a base, with the base standing in a substantially vertical orientation in relation to a foundation or the ground and having a bottom plate and a top plate, a frame fixedly extending in a substantially vertical orientation, a power train mounted to the frame; an electrical generator attached below the power train; at least one rotor shaft rotably mounted to the frame extending in a substantially vertical orientation, a rotor blade assembly attached to the tube comprising an outer skin defining a blade surface having a leading edge and a trailing edge with a cord extending from the leading edge to the trailing edge, each side of the blade surface having a convex portion and a concave portion wherein the concave portion of one of the sides crosses the cord at a single occurrence, wherein the frame is attached to the rotor shaft so that the rotor rotates, with the blade, about the longitudinal axis of the rotor to catch the wind and use the power of the wind to optimally rotate about the vertical axis, and provide a greater efficiency than known wind turbine blades currently in use in converting the wind energy into mechanical energy. 
         [0008]    In yet another embodiment, the outer perimeter of the rotor blade is uniform in lateral cross section and includes a rounded leading edge and a pointed trailing edge. Extending between the leading edge and the trailing edge is a first side surface and a second side surface. The first side surface is concave proximate the front edge and convex proximate the trailing edge. Conversely, the second side surface is convex proximate the front edge and concave proximate the trailing edge. In an embodiment, the first surface does not cross the cord of the rotor blade. In contrast, the second surface crosses the cord at a single occurrence. 
         [0009]    Other embodiments, systems, methods, features, and advantages of the present invention will be, or will become, apparent to one having ordinary skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, method, features, and advantages be within the scope of the present invention, and can be protected by the accompanying claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The invention may be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. In the drawings, like reference numbers designate corresponding parts throughout. 
           [0011]      FIG. 1  is a simplified side elevation view of a wind turbine system in accordance with the present invention; and, 
           [0012]      FIG. 2  is a simplified view of the wind turbine system from plane  2 - 2  of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    The following descriptions of detailed embodiments are for exemplifying the principles and advantages of the inventions. They are not to be taken in any way as limitations on the scope of the inventions. 
         [0014]    In one application of an embodiment in accordance with the present invention, a wind turbine is provided for converting wind energy into mechanical energy. Turning to  FIG. 1 , a simplified side elevation view is provided of a system in accordance with the present invention. 
         [0015]    The system  12  includes a support structure or frame  14  with a power train  16  mounted to the frame. A tubular rotor shaft  18  is rotatably mounted to the frame  14  and is coupled to the power train  16 . Secured to the rotor shaft  18  is a wing or blade  20  that extends vertically upwardly from the power train  16 . 
         [0016]    In an embodiment, the frame  14  is generally U-shaped and can be constructed of a metal or metal alloy. Preferably, the frame  14  is fixedly mounted or anchored so that it does not move about. In an embodiment, but not necessarily, the frame can be attached to a support structure (not shown) that is mounted to a concrete pad or the like. In an alternative embodiment, the frame  14  can be attached to a preexisting freestanding tower, rooftop, or other suitable structure. 
         [0017]    The rotor shaft  18  can be a hollow metal or metal alloy tube that is secured to the frame  14  through an upper bearing assembly at the top  22  of the rotor and through a lower bearing assembly near the bottom  24  of the rotor shaft. The rotor shaft  18  can be a single piece or may comprise a plurality of tube sections attached together. 
         [0018]    In another embodiment, the rotor shaft  18  can be two separate shafts in coaxial alignment with each other wherein one shaft is mounted to one end of the blade  20  and/or end plate  40  and the other shaft is mounted on the opposite end of the blade and/or end plate  44 . 
         [0019]    As shown in  FIG. 2 , the rotor blade  20  can include an inner frame  26  surrounded by an outer skin  28  to define a blade-like structure. The frame  26  is attached to the rotor  18  so that the rotor rotates, with the blade, about the longitudinal axis of the rotor. The frame  26  can be constructed of any suitable material such as plastic, fiberglass, metal, a metal alloy, wood, a fill material such as, but not limited to, polyurethane foam, or any combination thereof. In an embodiment, the frame can be constructed in a manner similar to an aircraft wing wherein the rotor shaft  18  is the spar of the blade  20  and ribs perpendicularly extend from the spar. 
         [0020]    The outer skin  28  of the rotor blade  20  can be constructed of any suitable material such as plastic, carbon-fiber, fiberglass, metal, a metal alloy, wood, or any combination thereof. In an embodiment, the outer skin  28  and the frame  26  are a metal alloy, such as an aluminum alloy, wherein the outer skin  28  is attached to the frame  26  by rivets. 
         [0021]    As shown in  FIG. 2 , in an embodiment, the outer perimeter of the rotor blade  20  is uniform in lateral cross section and includes a rounded leading edge  30  and a pointed trailing edge  32 . Extending between the leading edge  30  and the trailing edge  32  is a first side surface  34  and a second side surface  36 . The first side surface  34  is concave proximate the front edge  30  and convex proximate the trailing edge  32 . Conversely, the second side surface  36  is convex proximate the front edge  30  and concave proximate the trailing edge  32 . In an embodiment, the first surface  34  does not cross the cord  38  of the rotor blade  20 . In contrast, the second surface  36  crosses the cord at a single occurrence  39 . 
         [0022]    As also shown in  FIG. 2 , in an embodiment, the cord  38  of the rotor blade  20  is about 66 inches long from the leading edge  30  to the trailing edge  32 . 
         [0023]    As also shown in  FIG. 2 , the blade  20  has an upper camber  33  and a lower camber  35 , with a maximum separation between the cambers of about 28 inches. Furthermore, the blade has a mean camber line  37  that is generally S-shaped. The mean camber line  37 , as illustrated in  FIG. 2 , is the line that is equidistant at all points between the upper  33  and lower  35  cambers of the blade  20 . 
         [0024]    Turning back to  FIG. 1 , as indicated previously, end plates  40  and  42  are mounted on the ends of the rotor blade  20 . In an embodiment, each end plate has a cord  45  of about 96 inches that is offset from the cord  38  of the rotor blade  20 . The end plates can be constructed of plastic, fiberglass, metal, a metal alloy or another suitable material. The end plates can be attached to the blade assembly in a conventional manner such as by screws, bolt, rivets or by other suitable means. 
         [0025]    Preferably, the end plates  40  and  42  are in coplanar spaced relationship to each other and are symmetrical in shape relative to each other. As shown in  FIG. 2 , the outer perimeter  44  of each end plate is symmetrical about a longitudinal axis  46  and a lateral axis  48 . In an embodiment, the sides of each end plate are parallel to each other and the ends are arcuate. Moreover, the cord  38  of the rotor blade  20  is offset from the longitudinal axis  46  of each end plate. 
         [0026]    In a further embodiment, but not necessarily, one or more center or intermediate plates  76 , similar to end plates  40  and  42 , can be mounted to the rotor blade  20  between the end plates  40  and  42 . In this embodiment, the intermediate plate(s) can have the same outer geometry, shape and size as the end plates  40  and  42 , or have a different outer geometry, shape or size. 
         [0027]    In an embodiment, the mean camber line  37  intersects with the longitudinal axis  46  of the rotor shaft  18 . 
         [0028]    As will be appreciated by those having ordinary skill in the art, the rotor blade  20  is responsive to wind currents. In particular, the blade  20  imparts rotation upon the central vertical shaft  18  when the blade is subjected to a wind current. It is believed by the inventor that the curvilinear profile of the outer skin  28  of the blade  20 , depicted in  FIG. 2 , provides a greater efficiency than other wind turbine blades currently in use. Stated another way, as wind passes about the surface of the rotating blade, the unique profile of the blade is more efficient in converting the wind energy into mechanical energy than other blade profiles currently in use. 
         [0029]    Furthermore, it will be apparent to those having ordinary skill in the art that the choice of wind direction is entirely arbitrary in the present invention inasmuch as the curvilinear shape of the blade will turn irrespective of the wind direction. 
         [0030]    In an embodiment, but not necessarily, the power train  16  includes mechanical components such as a conventional speed increaser wherein the output of the speed increaser is received by an electrical generator  50 . As will be appreciated by those having ordinary skill in the art, the speed increaser is operatively attached to the rotor shaft  18  by, for example, belts and/or gears and has an output shaft wherein rotation of rotor  18  results in rotation of the output shaft at a higher rotational speed than that of the rotor  18 . 
         [0031]    In an embodiment, the electrical generator  50  is a conventional device and is operatively attached to the speed increaser output shaft by, for example, belts and/or gears and generates an electrical output in response to rotation of the output shaft of the speed increaser. 
         [0032]    Although the blade  20  is shown in  FIG. 1  to be mounted in a vertical orientation relative to the horizon, in an alternative embodiment, the system  12  can be positioned so the blade is mounted in a horizontal orientation (i.e., the rotor shaft is parallel with the horizon). 
         [0033]    The turbine of the present invention can be used for generating mechanical energy, e.g., electricity, and in many other areas contemplated by those having ordinary skill in the art, whether disclosed or not. For example, the turbine of the present invention can also be used to charge storage batteries should the user decide to generate electricity to a residence, or some other facility. 
         [0034]    The foregoing also describes only some embodiments of the present invention and modifications, obvious to those skilled in the art can be made thereto without departing from the present invention. For example, either clockwise or anti-clockwise rotation of the rotor is contemplated. Similarly, the extension to three, four or more blades mounted on a plurality of shafts is readily apparent. 
         [0035]    It should, therefore, be emphasized that the above-described embodiments of the present invention, particularly, any “preferred” embodiments, are possible examples of implementations merely set forth for a clear understanding of the principles for the invention. Many variations and modifications may be made to the above-described embodiment(s) of the invention without substantially departing from the spirit and principles of the invention. All such modifications are intended to be included herein within the scope of this disclosure and the present invention, and protected by the following claims.