1. Field of the Invention
The present invention relates to energy generators, and particularly to a vertical wind turbine of the Savonius-type that provides increased efficiency in converting wind energy into usable energy.
2. Description of the Related Art
Alternative energy plays an important role in the worldwide economy and the living conditions in current times. Some of these alternative energy solutions and the production thereof include solar energy, wave energy, geothermal energy, and wind energy.
Wind turbines are a common device for generating energy by harnessing the kinetic energy of the wind into mechanical energy, and then into electricity. As electricity generators, wind turbines can be connected to electrical networks, such as battery charging circuits, power systems, and large utility grids. The performance of a wind turbine can be related to three points on a velocity scale. The first point is the cut-in speed which is the minimum speed required to deliver useful power. The second point is the rated wind speed, which is the wind speed at which the rated power is reached. The third point is the cut-out speed, which is the maximum speed at which the turbine is allowed to deliver power. Wind turbines are mainly classified into two types according to the orientation of the rotor, a horizontal axis wind turbine (HAWT) and a vertical axis wind turbine (VAWT).
The HAWT-type of wind turbine includes a rotor in which the axis of rotation is parallel to the ground and to the wind stream, and the generator is usually disposed on top of a tower. Most modern HAWT have a propeller-type rotor having a plurality of airfoil blades. This configuration converts the linear motion of the wind into rotational energy by the wind acting against the airfoil blades. The airfoil blades are designed much like the wings of an airplane to create areas of high pressure and low pressure as the wind passes over the airfoil blades. The pressure differential creates lift that pushes the airfoil blades. As a result, the movement of the airfoil blades rotates the rotator. A certain amount of force acts in opposition to the lift force, and this force is referred to as drag. Drag diminishes the actual amount of lift force acting on the airfoil blades, which lowers the power-generating potential or efficiency of the turbine. Thus, a relatively high lift-to-drag ratio is preferred.
The VAWT-type of wind turbine includes a rotor in which the axis of rotation is perpendicular with respect to the ground and the wind stream. The generator and gearbox are typically located in the base of the wind turbine, which is easier for maintenance. Such turbines do not need an orientation mechanism because the turbine rotates from the action of the wind, no matter from which direction the wind impacts the VAWT. However, these VAWTs tend to rotate at lower speeds. One of the main issues associated with VAWTs is the relatively large torque generated during operation. This tends to lead to higher failure rates and operation at lower efficiency compared to HAWTs.
One common type of VAWT is named after a Finnish engineer, Sigurd Johannes Savonius, ca. 1922. An example of a Savonius wind turbine S is shown in
Although the efficiency of a Savonius-type wind turbine is relatively low, it is believed that the efficiency thereof may be increased by reducing some of the negative drag present in such a wind turbine. Thus, a vertical wind turbine solving the aforementioned problems is desired.
The vertical wind turbine is provided with a rotating vane housing mounted between an upper, cam disk and a lower, base disk, the base disk being mounted to a shaft. A plurality of turbine blades are pivotally mounted around the vane housing, each of the blades being pivotal between open and closed positions with respect to the housing. The cam disk defines a cam profile. A follower is coupled to each turbine blade. The follower forces the connected blade to open or close as the follower travels along the cam profile during each revolution of the housing. The open position of the blade harnesses wind energy to induce torque for rotating the housing. The closed position of the blade reduces drag to increase efficiency of the vertical wind turbine.
These and other features of the present invention will become readily apparent upon further review of the following specification and drawings.
Similar reference characters denote corresponding features consistently throughout the attached drawings.
The vertical wind turbine, generally referred to by the reference number 10 in the Figures, provides a continuous means of controlling the angular position of the blades to reduce negative drag and increase efficiency. In a typical Savonius wind turbine, as shown in
As best seen in
A plurality of turbine vanes or blades 14 are pivotally mounted to the exterior of the vane housing 12. Each turbine blade 14 is preferably an elongate, arcuate plate having an inner, generally concave face 14a and an outer, generally convex face 14b. The concave face 14a captures the airstream of the incoming wind to induce torque on the housing 12 and rotate the same during operation. One side of each turbine blade 14 is rigidly attached to an elongate pivot pin 17. Each pivot pin 17 is pivotally supported between an upper pivot support bracket or tab 17a and a lower pivot support bracket or tab 17b extending radially from the top and bottom of the housing 12, respectively. This configuration permits each turbine blade 14 to pivot between open and closed positions with respect to the exterior of the housing 12 during a complete revolution of the housing 12. In the open position shown in
To facilitate opening and closing operations of each turbine blade 14, the vertical wind turbine 10 is provided with a cam mechanism. The cam mechanism includes the cam disk 20 and a roller follower 15 coupled to the pivot pin 17 of each turbine blade 14. The cam disk 20 is a generally circular disk having a curvilinear cutout along an arcuate segment of the cam disk 20, defining a non-circular cam profile 21 along the periphery. The cam disk 20 is stationary with respect to the housing 12. Each follower 15 is coupled to the corresponding pivot pin 17 by a follower arm 16 so that as the follower 15 rolls along the cam profile 21, the follower 15 causes the follower arm 16 to pivot the connected pivot pin 17 and vary the angular position of the turbine blade 14.
In use, during each revolution of the housing 12, each turbine blade 14 remains substantially closed for a major angular segment of the revolution. Each turbine blade 14 begins to open as the follower 15 enters the curvilinear cutout section of the cam profile 21 and fully opens in an arcuately projecting central portion of the cam profile 21. The turbine blade 14 closes as the follower 15 exits the cutout section. Any wind striking the concave face 14a of the blade 14 causes the shaft 11 and housing 12 to rotate, while adjacent blades 14 remain closed and collapsed against the housing 12, thereby diminishing drag. Inertia causes the housing 12 to continue to rotate until the roller follower 15 of the next adjacent blade 14 follows the cam profile, extending the next adjacent blade 14 to the open position so that its concave face 14a catches the wind to further drive rotation of the housing 12 and shaft 11, thereby generating power.
Another embodiment of a cam disk 120 is shown in
A further embodiment of a cam disk 220 is shown in
It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.