Abstract:
A novel modification of a Savonius rotor used as a wind turbine provides an exhaust channel in each vane. The vane of the modified Savonius rotor is formed into an “S” shape. The air that enters a given end of the vane exits that end through the new exhaust channel into the freestream. A plurality of modified Savonius rotors are stacked one on top of the other for self-starting and greater power output. The outer surfaces of the entire assembly may be coated with photo voltaic cell material for additional energy production. In one embodiment of the invention, a cone shaped solar collector is placed on top of the entire modified Savonius rotor assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO MICROFICHE APPENDIX 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to an alternate source of energy. More particularly the present invention relates to a modification to a Savonius wind turbine rotor for converting kinetic energy in the wind to shaft power. 
     2. Background Art 
     Shaft power has been derived from the wind for centuries. Dutch windmills were first used for grist, and later converted to raising water to sea level for land reclamation. Wind power was commonly harnessed across the prairie and plains states in the U.S. for pumping water from wells. In the early part of the 20 th  century, wind was utilized for converting kinetic energy to electrical energy. 
     The last quarter of the 20 th  century saw a marked increase in interest in converting wind energy to shaft power. Many units from that era were horizontal shaft wind turbines using airfoils of various types. Drawbacks of such an arrangement are the need to have the power unit (generator, air compressor, etc.) on top of the tower with the airfoils, or the need for gearing to transfer the power toward the ground. 
     Efforts have been made toward improving vertical-shaft wind turbines as well. The Darius rotor utilizes airfoils in a fashion quite different than the horizontal shaft units. However, the Darius rotor is not self-starting, so a starting scheme is required. 
     The Savonius rotor is a self-starting, low-speed, vertical axis wind turbine (the axis need not be vertical, however, that is the usual configuration). However, in its traditional form (see  FIG. 1 ), the Savonius rotor is known to exhibit low efficiencies. It is known as a drag-type wind turbine, as opposed to the lift-type wind turbines having horizontal axes and the Darius rotor. Rotation of the Savonius rotor is effected through momentum transfer from the air. The momentum of the air changes as its path is curved by the vanes of the Savonius rotor. Momentum exchange occurs on entrance to the vanes and on exit from the vanes. The change in momentum with time results in forces that tend to turn the Savonius rotor on its axis of rotation. 
     A modification to the Savonius rotor of FIG. 1 was disclosed in U.S. Pat. No. 5,494,407. The blades of this invention have been altered from half-circles in cross-section as seen in FIG. 1 to the shape shown in FIG. 2, having a linear portion nearer the axis of rotation and a curved portion, which is substantially an arc of a circle tangent to the linear portion and tangent to the circle defining the rotor diameter. 
     Another modification to the Savonius rotor of FIG. 1 is revealed in U.S. Pat. No. 6,283,711 wherein an additional, outer vane that is pivotally attached to the original, semicylindrical blade at the latter&#39;s leading edge. 
     A novel modification to the traditional Savonius rotor is shown in FIG. 3 wherein the vanes are reduced in size away from a vertical center such that they reach apexes at the top and bottom of the unit. Such a wind turbine can be made of light fabric material. 
     In all the prior art, the air flows into the cavity created by a vane, then is directed along a path that is substantially parallel to the vane until it exits the first vane and enters the second vane. The streamlines are, again, substantially parallel to this second vane. The air is finally exhausted downstream of the wind turbine to the freestream. None of the prior art discloses an exhaust port to permit air to exit the first vane without traveling through the second vane. 
     In addition, the known prior art does not reveal the use of Savonius rotor vanes as a surface on which to apply a solar panel. 
     There is, therefore, a need for an improved exit path for air to exhaust from a vane in a Savonius rotor. There is an additional need for the use of Savonius rotor vanes as a surface on which to apply solar panels. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a flow path for exiting air from a Savonius rotor without passing through a channel produced by a first and second vanes. 
     To effect the modification of a Savonius rotor, the two vanes are formed in a single “S” shapes vane and channels are provided, preferably along a lower edge of the vane and extending at least halfway up the vane. Through the channel is a flow path for the air to pass through the vane from the convex portion of the vane to the freestream. In shape, the exhaust channel transitions smoothly from the vane, in a shape roughly similar to a cylinder diverging from the vane. 
     The airflow will, in the preferred embodiment and in a coordinate system attached to the rotating modified Savonius rotor, pass along the curved vane of the Savonius rotor, thereby undergoing a change in its momentum and, therefore, imparting a force on the modified Savonius rotor causing the rotor to spin. As the air continues toward the axis of rotation of the modified Savonius rotor but before it reaches the axis of rotation, it exits through the exhaust channel which leads to the freestream. 
     Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a plan view of a Savonius rotor of the prior art with semicylindrical vanes; 
         FIG. 2  is a plan view of a first modified Savonius rotor of the prior art; 
         FIG. 3  is a plan view of a second modified Savonius rotor of the prior art; 
         FIG. 4  is a perspective view of a modified Savonius rotor assembly of the present invention with a load and tower; 
         FIG. 5  is a first top plan view of a modified Savonius rotor; 
         FIG. 6  is a detail of a lower flange of the modified Savonius rotor; 
         FIG. 7  is a first top plan view of the modified Savonius rotor; 
         FIG. 8  is a first detail of an exhaust channel of the modified Savonius rotor; 
         FIG. 9  is a first plan view of the modified Savonius rotor assembly; 
         FIG. 10  is a second detail of an exhaust channel of the modified Savonius rotor; 
         FIG. 11  is a third detail of an exhaust channel of the modified Savonius rotor; 
         FIG. 12  is a side elevation view of the modified Savonius rotor; 
         FIG. 13  is a fourth detail of an exhaust channel of the modified Savonius rotor; 
         FIG. 14  is a fifth detail of an exhaust channel of the modified Savonius rotor; 
         FIG. 15  is a sixth detail of an exhaust channel of the modified Savonius rotor; 
         FIG. 16  is a perspective view of a slip ring assembly; 
         FIG. 17  is a detail of the slip ring assembly; 
         FIG. 18  is a perspective view of a second embodiment of the modified Savonius rotor assembly of the present invention with a load and tower; 
         FIG. 19  is a first top plan view of the second embodiment of a modified Savonius rotor; 
         FIG. 20  is a detail of a lower flange of the second embodiment of the modified Savonius rotor; 
         FIG. 21  is a first top plan view of the second embodiment of the modified Savonius rotor; 
         FIG. 22  is a first detail of an exhaust channel of the second embodiment of the modified Savonius rotor; 
         FIG. 23  is a second detail of an exhaust channel of the second embodiment of the modified Savonius rotor; 
         FIG. 24  is a side elevation view of the second embodiment of the modified Savonius rotor; 
         FIG. 25  is a third detail of an exhaust channel of the second embodiment of the modified Savonius rotor; 
         FIG. 26  is a fourth detail of an exhaust channel of the second embodiment of the modified Savonius rotor; 
         FIG. 27  is a fifth detail of an exhaust channel of the second embodiment of the modified Savonius rotor; 
         FIG. 28  is a perspective view of an assembly of a third embodiment of the modified Savonius rotor; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A set of three (3) modified Savonius rotors  405 ,  410 ,  415  are shown stacked vertically in  FIG. 4  in a rotor assembly  400  in a first embodiment of the invention. By angling the “S” shaped vanes differently for each set (in this case 120° apart), automatic startup is assured because at least one rotor will be turned such that the change in momentum of the wind will cause the assembly to turn. The set of modified Savonius rotors  405 ,  410 ,  415  in the assembly  400  are rigidly affixed to a shaft  420  which rotates as the modified Savonius rotors  405 ,  410 ,  415  rotate. A bearing (not shown) at a lower end of the shaft  420  provides reduced friction rotation. Via the shaft  420 , power is transmitted to a power converting device  425  such as an electrical generator, an air compressor, pump, etc. An advantage of the Savonius rotor over horizontal-shaft wind turbines is the ability to locate the power converting device  425  at or near ground level where it is accessible for installation, maintenance, repair, and inspection. 
     Usually, a tower  430  is used to elevate the modified Savonius rotor assembly  400  into higher wind speeds to increase the power output of the power converting device  425 . 
     A support plate  450  is installed at the top of each of the modified Savonius rotors  405 ,  410 ,  415  and the bottom of the lowest modified Savonius rotor  405  to provide rigidity. 
     In this first embodiment of the invention, outer surfaces of the modified Savonius rotor assembly  400  are coated with photovoltaic cells as indicated by the crosshatching in  FIGS. 1–17 . 
     In  FIG. 5  a top plan view of a single modified Savonius rotor is depicted. Top flanges  510  and bottom flanges  610  (see  FIG. 6 ) provide stability for each end of the “S” shaped vane  710  (see  FIG. 7 ) and channeling of the air along the vane&#39;s surface. The outsides of the exhaust channels  530  are clearly seen in  FIG. 5 , the exhaust channel being extending out from the convex faces of the vane  710 . 
     A plan view of an end of an “S” shaped vane from a horizontal midsection is seen in  FIG. 6 . A lower flange  610  is clearly seen, as well as a portion of the exhaust channel  530 . A metallic edge  620  is applied to the lower flange  610  to enhance rigidity and provide some protection from abrasion. 
     The top flanges  510  and upper support plate  450  have been removed in  FIG. 7  to more clearly see the “S” shaped vane  710  of the modified Savonius rotor. The exhaust channels  530  are seen from above. The air flow across one end of the vane  710  for a given position of the vane  710  is indicated. 
       FIG. 8  is a cross section of a lower portion of a modified Savonius rotor vane. The wall of the exhaust channel  530  and the lower flange  610  are clearly seen. The metallic edge  620  is affixed to the leading edge of the lower flange  610 . 
     A top view of the modified Savonius rotor assembly  400  is shown in  FIG. 9 . From this angle, the 120° shifts in angle are evident between each of the modified Savonius rotors  405 ,  410 ,  415 . 
       FIG. 10  is a view from the concave side of one end of a vane  710  of the modified Savonius rotor  405  in the neighborhood of the axis of rotation. From the angle of  FIG. 10 , the interior of the exhaust channel  530  is clearly seen. 
     In  FIG. 11 , the direction of view is opposite that of  FIG. 10 . From the angle of  FIG. 11 , the convex side of one end of the vane  710  and the outer wall of the exhaust channel  530  are seen. 
     A side view of the modified Savonius rotor  405  is shown in  FIG. 12 . On the left, the vane  710  is viewed from its convex side, and the exhaust channel  530  is seen from its outside. On the right, the vane  710  is viewed from its concave side, and the inner surface of the exhaust channel  530  is seen. 
       FIGS. 13 and 14  further detail the exhaust channel  530 . In  FIG. 13 , the view is toward the inside of the exhaust channel  530  whereas  FIG. 14  is a view of the outside of the exhaust channel  530 . 
     Another view from the open end of the exhaust channel  530  is shown in  FIG. 15 . 
     Because solar panels are affixed to the outer surfaces of the modified Savonius rotor assembly  400 , the energy produced by the photovoltaic cells must be transferred to the ground for use or storage. Wires  1610  lead from the photovoltaic cells through the hollow shaft  420  towards the ground. Near the power converting device, a slip ring assembly  1710 , shown in  FIG. 17 , is used to transfer the electrical power from the wires  1610  rotating with the shaft  420  to stationary wiring  1720 . The wires  1610  from the photovoltaic cells lead through the hollow shaft  420  to slip rings  1730  that are electrically insulated from each other. Stationary brushes  1740  are forced against the slip rings  1730  and are connected to the wiring  1720  provide the conductive path for the electrical power to take from the rotating slip rings  1730  to the stationary components  1720 ,  1740 . The stationary wiring  1720  conduct the current to storage, an inverter, or end use. 
     A second embodiment of the present invention is shown in  FIG. 18  wherein larger support plates  1810  are used in place of the smaller support plates  450  shown in  FIGS. 4 and 5  and no photovoltaic cells are utilized. In this preferred embodiment, each support plate  1810  is attached to the top flange  510  and bottom flange  610  by bolts or rivets as shown. Other possibilities for adjoining a support plate  1810  and a vane  710  are by adhesive or combining the top and bottom flanges  510 ,  610  into one support plate  1810 . 
     The view shown in  FIG. 19  is similar to that of  FIG. 6  with the addition of the larger support plate  1810  and the absence of solar collecting material. Again, a metallic edge  1910  is provided on the leading edge of the bottom flange  610 . A detail of a cross section of the vane  710  and metallic edge  1910  is shown in  FIG. 20 . The metallic edge  1910  has a sharpened leading edge to reduce the disturbance to the boundary layer of the flow over the support plate  1910  and bottom flange  610 . 
     Looking through the top flanges  510  and upper support plate  1810  in  FIG. 21 , the “S” shaped vane  710  of the modified Savonius rotor can be discerned. The exhaust channels  530  are also seen. 
       FIGS. 22 and 23  further detail the exhaust channel  530 . In  FIG. 21 , the view is toward the inside of the exhaust channel  530  whereas  FIG. 22  is a view of the outside of the exhaust channel  530 . The larger support plates  1810  are seen in these views. 
     A side view of the modified Savonius rotor  405  is shown in  FIG. 24 . On the left, the vane  710  is viewed from its convex side, and the exhaust channel  530  is seen from its outside. On the right, the vane  710  is viewed from its concave side, and the inner surface of the exhaust channel  530  is seen. 
     Two other views of the exhaust channel  530  for the second embodiment of the invention are shown in  FIGS. 25 and 26 . The inside of the exhaust channel  530  is shown in  FIG. 25  whereas the outside of the exhaust channel  530  is shown in  FIG. 26 . 
     Another view from the open end of the exhaust channel  530  is shown in  FIG. 23 . 
     A third embodiment of the modified Savonius rotor assembly  400  is shown in  FIG. 28  wherein the assembly shown in  FIG. 18  is outfitted with the addition of a cone-shaped solar collector  2810  at its top. Separate isosceles triangular sections  2820  of photovoltaic solar cells are creased so as to have a ridge running from the top apex to the base. These individual triangular sections  2820  are adjoined to produce the cone shape. As shown, the cone has an included angle of 120°. 
     The above embodiment is the preferred embodiment, but this invention is not limited thereto. It is, therefore, apparent that many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.