Vertical Axis Wind Turbine
An improved vertical axis wind turbine for generating electric power which includes blades that provide improved performance per unit of surface area. The blades are adapted to rotate about a vertical axis and are shaped having a leading cupped section joined to a lagging airfoil section. The leading cup section is defined by a cup radius r and the lagging airfoil section is defined by an airfoil chord length CL. The leading cupped section and lagging airfoil section extend vertically a distance h between terminal bottom and top ends. The cup radius r and chord length CL both decrease towards the terminal bottom and top ends of the blade. Also, the airfoil section is located a radial distance Cd from the vertical axis and the radial distance Cd decreases towards the terminal bottom and top ends of the blade.
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This application claims priority under 35 U.S.C. 119(e) of U.S. provisional patent application Ser. No. 62/809,217 filed on Feb. 22, 2019 entitled Vertical Axis Wind Turbine Blade and Illuminated Ornament Powered by a Vertical Axis Wind Turbine, the disclosure of which is hereby incorporated herein by reference.
BACKGROUND OF THE INVENTION 1. Field of the InventionThe present invention relates generally to a wind powered vertical axis wind turbine and an illuminated ornament which utilizes a vertical axis wind turbine to charge a rechargeable battery. Energy stored in the battery is used to illuminate a decorative ornament at night. The present invention is also directed to a curved blade design for a vertical axis wind turbine which provides improved performance relative to traditional straight blades per unit of surface area.
2. BackgroundDecorative devices that move in the wind, often referred to as wind sculptures or wind spinners, are popular as lawn decorations. During the day, if it is windy, they provide a colorful moving display. Some also include a generator or alternator that illuminates light emitting diodes (LED's) at night when the device is spinning in the wind.
Vertical axis wind turbines (VAWT) lend themselves well to decorative lawn ornaments since the blades rotate at a fixed distance from a central vertical axis. The volume enclosed within the rotating blades provides a convenient and attractive location for an illuminated decorative ornament and the alternator and electronics needed to charge a battery and control the LED illumination. It is desirable that the blades used in a VAWT operate in both drag and lift modes. Drag mode operation allows power generation in light wind and insures that the VAWT is self-starting in almost all wind conditions. Lift mode operation at higher wind speeds optimizes power generation by increasing the tip speed ratio (TSR) which is the ratio between the tangential speed of the tip of the blade to the actual speed of the wind. The blade shapes typically used for VAWT's that combine drag and lift mode are lacking in aesthetic qualities and do not provide optimum performance. Therefore there is a need for a combined drag/lift mode VAWT blade design with improved aesthetics and performance.
SUMMARY OF THE INVENTIONThe present invention overcomes disadvantages of prior combined drag/lift mode VAWT blade designs intended to be used with an illuminated ornament located within a volume enclosed by the rotating blades.
One object of the invention is to provide a combined drag/lift mode VAWT blade design that produces more power per unit surface area of the blade.
Another object of the invention is to provide a combined drag/lift mode VAWT blade design that increases the area under the curve on a plot of full-system power (Cp) versus wind tip speed ratio (TSR) to improve system performance while the turbine revolutions per minute (RPM) is lagging behind changing wind speeds.
Another object of the invention, is to provide a combined drag/lift mode VAWT blade design with increased hysteresis in the power transfer curve as load impedance is increased compared to as load impedance is decreased in order to improve performance in variable wind conditions.
Another object of the invention is to provide a control system that ensures that the system operating point is on the optimum portion of the hysteresis curve.
Another object of the invention is to provide a combined drag/lift mode VAWT blade design that minimizes turbulence and noise at the blade ends.
Another object of the invention is to provide a combined drag/lift mode VAWT blade design that causes specular reflections from sunlight at multiple elevations during the day to reach the eye of an observer.
Another object of the invention is to provide a combined drag/lift mode VAWT blade design that is self-starting.
Another object of the invention is to provide a combined drag/lift mode VAWT blade design that spins freely in winds that are too slow to create useful power output but are fast enough to create a pleasing visual experience.
Another object of the invention is to provide a VAWT with an alternator consisting of a rotor with a self-contained stator, where the rotor is attached to multiple blades at a centralized location and includes an illuminated ornament within the blades and in close proximity to the rotor.
Another object of the invention is to provide VAWT with a stator that attaches to a shaft with a terminal end that is mounted to a decorative assembly that includes a light emitting diode (LED) for illumination, a battery to store energy derived from the wind, electronics to control the charging of the battery and the illumination of the LED, all enclosed within a decorative ornament that is illuminated by the LED.
In one form thereof, the present invention is directed to a vertical axis wind turbine comprising a plurality of blades adapted to rotate about a vertical axis, wherein each of the blades comprise: a leading cupped section joined to a lagging airfoil section, wherein the leading cup section is defined by a cup radius r and the lagging airfoil section is defined by an airfoil chord length CL; wherein the leading cupped section and lagging airfoil section extend vertically a distance h between terminal bottom and top ends; and, wherein the cup radius r and chord length CL both decrease towards the terminal bottom and top ends of the blade.
Preferably, the cup radius r and chord length CL both decrease towards the terminal bottom and top ends of the blade starting from a vertical midpoint between the terminal bottom and top ends. Also preferably, the airfoil section is located a radial distance Cd from the vertical axis and wherein the radial distance Cd decreases towards the terminal bottom and top ends of the blade starting form a vertical midpoint between the terminal bottom and top ends.
More preferably, the airfoil section is located a radial distance Cd from the vertical axis and wherein the radial distance Cd decreases towards the terminal bottom and top ends of the blade.
The leading cupped section can extend between an outermost edge and an inner area, wherein the inner area is joined with the airfoil section and the outermost edge traverses along an arcuate path defined by a diameter D as the blades rotate about the vertical axis and, preferably, r/D<CL/D<1.
The blades can be coupled to an alternator adapted to produce electric power. Also, the blades can be formed of sheet material. A light emitting device can be centrally located between the plurality of blades and can be powered by the alternator. The blades can be secured to each other at their terminal bottom ends.
Preferably, the blades are coupled to an alternator adapted to produce electric power and the alternator is selectively connectable to a load through a load switch and further wherein, when an output of the alternator is insufficient to produce useful power, the load is disconnected from the alternator and, after the blades and alternator gain momentum, the load is again connected to the alternator.
The blades can be coupled to a rotor of an alternator adapted to produce electric power, wherein the blades are attached to the rotor below a vertical midpoint between the bottom and top terminal ends of the blades and wherein the blades are secured to each other at their terminal bottom end.
In another form thereof, the present invention is directed to a vertical axis wind turbine comprising a plurality of blades adapted to rotate about a vertical axis, wherein each of the blades comprise: a leading cupped section joined to a lagging airfoil section, wherein the leading cup section is defined by a cup radius r and the lagging airfoil section is defined by an airfoil chord length CL; wherein the leading cupped section and lagging airfoil section extend vertically a distance h between terminal bottom and top ends; and, wherein the airfoil section is located a radial distance Cd from the vertical axis and wherein the radial distance Cd decreases towards the terminal bottom and top ends of the blade. Preferably, the radial distance Cd decreases towards the terminal bottom and top ends of the blade starting form a vertical midpoint between the terminal bottom and top ends.
The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout several views. Although the exemplification set out herein illustrates embodiments of the invention, in several forms, the embodiments disclosed below are not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise forms disclosed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTSIn a preferred embodiment, the decorative ornament (6) is centrally located within the blades (1) (2) (3) and occupies a large portion of the volume within the blades so that, aside from the blades, the decorative ornament is the dominant visual feature. In the case where the decorative ornament is essentially a sphere, this means the diameter of the sphere should be 30% or more of the diameter of a circle that would inscribe the blades at their maximum horizontal cross section. For non-spherical decorative ornaments, the diameter of a circle that inscribes the maximum horizontal cross section of the decorative ornament should be 30% or more of the diameter of a circle that would inscribe the blades at their maximum horizontal cross section. The alternator (4) is mounted directly below the decorative ornament (6) to help conceal the alternator and make the ornament (6) the dominant feature within the spinning blades (1) (2) (3). The rotor (5) positions the blades such that they are very close to the decorative ornament (6) which helps conceal the rotor (6) and helps insure that the dominant visual features are the blades and the decorative ornament.
The blades (1 thru 3) spin the rotor (5) to create an electromotive force (EMF) and induce an electric current/electric power in the coils (93) as those skilled in the art will understand. The faster the alternator rotor (5) rotates, the stronger is the EMF produced. The decorative ornament (6) sits within the blades (1) (2) (3) and is illuminated at night by an LED (95). A rechargeable battery (96) within the decorative ornament (6) is charged by the alternator (4) when the blades rotate and provides power for the LED (95). An electronic circuit (94) optimizes the charging of the battery (96) and controls the illumination of the LED (95).
To simplify further discussions,
The shape of the blades (1), (2) and (3) is shown in
Referring again to
It is noted that in the following discussions data is presented that was obtained from measurements made in a wind tunnel at wind speeds of approximately 7 MPH. These measurements are very noisy. For clarity, the data has been averaged and smoothed to a thin line when presented in graphical form.
Continuing to refer to
As depicted in
The chart (55) details the blade (56) parameters at elevations above and below the vertical midpoint of the blade in 20 mm increments where, at the vertical midpoint of the blade: D=182.4 mm, CL=68.1 mm, r=18.7 mm, Cd=53.5 mm, and θ=7.5 degrees. These are the same parameters as in the chart (50) in
The chart (62) defines the blade (60) parameters at a distance d above and below the vertical midpoint of the blade (60) for the preferred embodiment of the invention. The chord length CL, the cup radius r, and the cord distance Cd from center at a distance d from the vertical center of the blade (60) are given by three simple, second order polynomials. The coefficients jCL and kCL define the variation in chord length CL as d increases. Similarly, the coefficients jr and kr define the variation in cup radius r as d increases. Similarly, the coefficients jCd and kCd define the variation in chord distance Cd from center as d increases. D also varies with distance d from the vertical center of the blade, but it is a dependent variable and is fully defined by the cup radius r and the cord distance Cd from center at any particular distance d from the vertical center of the blade. However, it also can be described by a second order polynomial and its equation is included for completeness. To insure that the cup radius r, cord length CL, and cord distance Cd from center continuously decrease as d increases, the j and k coefficients in the table (62) must satisfy the following condition: 2*j*d+k<=0. As shown in table (63), the attack angle θ also decrease near the tips (61) of the blades (60) which further reduces losses and noise due to turbulence.
As depicted in
The chart (63) details the blade (60) parameters at elevations above and below the vertical midpoint of the blade in 20 mm increments where, at the vertical midpoint of the blade: D=182.4 mm, CL=68.1 mm, r=18.7 mm, Cd=53.5 mm, and θ=7.5 degrees. These are the same parameters as in the chart (50) in
Samples of the blades described in tables (50), (55), and (63) were fabricated and their performance was compared in a wind tunnel at a wind speed of approximately 7 MPH. As in
Referring again to
Referring now to
Referring now to
The ornament platform (89) is located directly above and in close proximity to the stator (85). This minimizes the length of shaft (81) which minimizes the distance from the circuit board (94) to the coils (93). The ornament platform (89) provides two posts (116) and a screw hole (117) to locate and attach PCB (94) using screw (119). Ornament platform (8) also provides a pocket (115) for battery (96) and two slots (118) for installing positive contact (106) and negative contact (108). Structures (120) and (121) capture springs (97) and (110) and hold them in place. Retaining clips (98) and (109) can slide in radially extending slots (122) formed on the ornament platform 89 and are pressed radially outward by springs (97) and (110), respectively. Latches (123) on the retaining clips (98) and (109) catch on tabs (not shown) on the underside of ornament platform (89) to prevent the retaining clips (98) and (109) from overextending. Tabs (100) are provided on the retaining clips (98) and (109) so that the retaining clips can be compressed manually if the decorative ornament (6) needs to be removed. In FIG. 19, retaining clip (109) is shown in its compressed position which releases the decorative ornament (6), whereas retaining clip (98) is shown in the extended position whereby it captures the decorative ornament (6) at contact point (111).
Decorative ornament (6) rests on ornament platform (89) and encloses and hides from view the battery (96), battery contacts (106) (108), circuit board (94), retaining clips (98) (109) and springs (97) (110). In a preferred embodiment, the decorative ornament (6) is a decorative hollow glass globe with an opening sized to fit ornament platform (89). A thin diffusing layer (99), preferably a thin layer of white glass, on the inside of the ornament reflects a portion of the light from LED (95) to evenly illuminate decorative ornament (6). The translucence of the diffusing layer (99) is chosen to maximize the light intensity on the surface of the decorative ornament (6) while remaining opaque enough to hide the structures internal to the ornament. Those skilled in the art will understand that methods other than a thin white layer of glass can achieve the same effect including, but not limited to, using frosted glass or adding diffusing agents or pigments to the glass. Materials other than glass could also be used.
Electronics on the circuit board (94) (not shown) control the charging of the battery and the illumination of the LED. In a preferred embodiment, the LED is illuminated at a first illumination level when dusk is detected. In order to minimize the drain on the battery (96), the illumination level is gradually reduced to a second illumination level. The first illumination level is brighter than the second illumination level. The transition time from the first illumination level to the second illumination level is chosen so the ornament will be brighter during the early part of the evening when it is most likely to be observed and dimmer, and therefore using less power, during late evening and early morning hours when the ornament is less likely to be observed. The LED is then turned off at dawn. In this manner, the ornament is illuminated from dusk to dawn but can use considerably less current that if the ornament was illuminated at the first illumination level for the entire night. In a preferred embodiment, the transition time from the first illumination level to the second illumination level is six hours and the first illumination level is eight times the second illumination level. As there are likely to be days and nights with little wind intermixed with days with lots of wind, it is desirable that the battery be able to provide illumination for multiple nights with little or no wind after being fully charged on a windy day. The first and second illumination levels and the time to gradually fade from the first illumination level to the second illumination level are selected so that the average current used during the night provides an acceptable tradeoff between brightness and battery life in this situation. In the preferred embodiment, the first illumination level is set by setting the LED current to 8 mA. Using commonly available LEDs with efficacies of 100 lumens/watt or more, this is enough illumination to create a pleasing ornament illumination level. The second illumination level is set by setting the current through the LED to 1 mA, which results in dimmer illumination of the decorative ornament, but is still adequate. Assuming a linear decrease in illumination, the average current during the first six hours of operation is then 4.5 mA. Assuming a 12 hour night, the remaining six hour before dawn will have an average current a 1 mA. The average current for a typical 12 hour night would then be 2.75 mA, thus consuming 33 mAHr in a single night assuming that only minimal current is used by the electronics. In the preferred embodiment, rechargeable battery (96) is a Lithium Phosphate, 3.2 volt battery with a 400 mAHr capacity, so if the battery is fully charged on a windy day it will be able to continue illuminating the ornament for at least ten nights without any additional wind.
While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles.
Claims
1. A vertical axis wind turbine comprising a plurality of blades adapted to rotate about a vertical axis, wherein each of the blades comprise:
- a leading cupped section joined to a lagging airfoil section, wherein the leading cup section is defined by a cup radius r and the lagging airfoil section is defined by an airfoil chord length CL;
- wherein the leading cupped section and lagging airfoil section extend vertically a distance h between terminal bottom and top ends; and,
- wherein the cup radius r and chord length CL both decrease towards the terminal bottom and top ends of the blade.
2. The vertical axis wind turbine of claim 1 wherein the cup radius r and chord length CL both decrease towards the terminal bottom and top ends of the blade starting from a vertical midpoint between the terminal bottom and top ends.
3. The vertical axis wind turbine of claim 1 wherein the airfoil section is located a radial distance Cd from the vertical axis and wherein the radial distance Cd decreases towards the terminal bottom and top ends of the blade starting form a vertical midpoint between the terminal bottom and top ends.
4. The vertical axis wind turbine of claim 1 wherein the airfoil section is located a radial distance Cd from the vertical axis and wherein the radial distance Cd decreases towards the terminal bottom and top ends of the blade.
5. The vertical axis wind turbine of claim 4 wherein the leading cupped section extends between an outermost edge and an inner area, wherein the inner area is joined with the airfoil section and the outermost edge traverses along an arcuate path defined by a diameter D as the blades rotate about the vertical axis.
6. The vertical axis wind turbine of claim 5 wherein r/D<CL/D<1.
7. The vertical axis wind turbine of claim 4 wherein the blades are coupled to an alternator adapted to produce electric power.
8. The vertical axis wind turbine of claim 4 wherein the blades are formed of sheet material.
9. The vertical axis wind turbine of claim 1 wherein the leading cupped section extends between an outermost edge and an inner area, wherein the inner area is joined with the airfoil section and the outermost edge traverses along an arcuate path defined by a diameter D as the blades rotate about the vertical axis.
10. The vertical axis wind turbine of claim 9 wherein r/D<CL/D<1.
11. The vertical axis wind turbine of claim 1 wherein the blades are coupled to an alternator adapted to produce electric power.
12. The vertical axis wind turbine of claim 1 wherein the blades are coupled to an alternator adapted to produce electric power and a light emitting device is centrally located between the plurality of blades and is powered by the alternator.
13. The vertical axis wind turbine of claim 1 wherein the blades are formed of sheet material.
14. The vertical axis wind turbine of claim 1 wherein the blades are coupled to an alternator adapted to produce electric power and the alternator is selectively connectable to a load through a load switch and further wherein, when an output of the alternator is determined to be on a lower power of two available operating points, the load is disconnected from the alternator and, after the blades and alternator gain momentum, the load is again connected to the alternator resulting in operation at the higher of the two operating points.
15. The vertical axis wind turbine of claim 1 wherein the blades are coupled to an alternator adapted to produce electric power and the alternator is selectively connectable to a battery wherein, when the wind speed is too low to produce enough power to charge the battery, the load is disconnected from the alternator and the blades are allowed to spin freely.
16. The vertical axis wind turbine of claim 1 wherein the blades are secured to each other at their terminal bottom end.
17. The vertical axis wind turbine of claim 1 wherein the blades are coupled to a rotor of an alternator adapted to produce electric power, wherein the blades are attached to the rotor below a vertical midpoint between the bottom and top terminal ends of the blades and wherein the blades are secured to each other at their terminal bottom end.
18. A vertical axis wind turbine comprising a plurality of blades adapted to rotate about a vertical axis, wherein each of the blades comprise:
- a leading cupped section joined to a lagging airfoil section, wherein the leading cup section is defined by a cup radius r and the lagging airfoil section is defined by an airfoil chord length CL;
- wherein the leading cupped section and lagging airfoil section extend vertically a distance h between terminal bottom and top ends; and,
- wherein the airfoil section is located a radial distance Cd from the vertical axis and wherein the radial distance Cd decreases towards the terminal bottom and top ends of the blade.
19. The vertical axis wind turbine of claim 18 wherein the radial distance Cd decreases towards the terminal bottom and top ends of the blade starting form a vertical midpoint between the terminal bottom and top ends.
20. The vertical axis wind turbine of claim 18 wherein the blades are coupled to an alternator adapted to produce electric power and the alternator is selectively connectable to a load through a load switch and further wherein, when an output of the alternator is determined to be on a lower power of two available operating points, the load is disconnected from the alternator and, after the blades and alternator gain momentum, the load is again connected to the alternator resulting in operation at the higher of the two operating points.
21. The vertical axis wind turbine of claim 18 wherein the blades are secured to one each other at their terminal bottom.
22. The vertical axis wind turbine of claim 18 wherein the leading cupped section extends between an outermost edge and an inner area, wherein the inner area is joined with the airfoil section and the outermost edge traverses along an arcuate path defined by a diameter D as the blades rotate about the vertical axis.
23. The vertical axis wind turbine of claim 22 wherein r/D<CL/D<1.
24. The vertical axis wind turbine of claim 18 wherein the blades are coupled to an alternator adapted to produce electric power.
25. The vertical axis wind turbine of claim 18 wherein the blades are coupled to an alternator adapted to produce electric power and a light emitting device is centrally located between the plurality of blades and is powered by the alternator.
26. The vertical axis wind turbine of claim 18 wherein the blades are formed of sheet material.
27. The vertical axis wind turbine of claim 18 wherein the blades are coupled to a rotor of an alternator adapted to produce electric power, wherein the blades are attached to the rotor below a vertical midpoint between the bottom and top terminal ends of the blades and wherein the blades are secured to each other at their terminal bottom end.
28. The vertical axis wind turbine of claim 18 wherein the blades are coupled to an alternator adapted to produce electric power and the alternator is selectively connectable to a battery wherein, when the wind speed is too low to produce enough power to charge the battery, the load is disconnected from the alternator and the blades are allowed to spin freely.
Type: Application
Filed: Feb 20, 2020
Publication Date: Aug 27, 2020
Applicant: Jenesis International Inc. (Benton Harbor, MI)
Inventors: Kim Irwin McCavit (Saint Joseph, MI), Mark Adam Goldy (Anthem, AZ), Roger Don Bentley (Coloma, MI), Robert H. Ashton (Watervliet, MI)
Application Number: 16/796,809