Abstract:
An improved wind energy generator is described. This invention is a wind turbine that utilizes airfoils in unique designs that are made of lightweight materials. The turbine is manufactured by low cost production methods as portable units that are stacked in series to provide for significant power harvesting. The use of three dimensional twisted airfoils enable high efficiency and easy start up.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    Not Applicable 
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable 
       BACKGROUND OF THE INVENTION 
       [0003]    Many different types of wind turbines have been built that can efficiently convert wind energy into electrical energy. For large scale power generation, a typical configuration is a wind farm consisting of three bladed horizontal axis turbines. These turbines are very large with blades of 50-100 feet or more built upon large steel towers and are pointed into the wind. Alternatively, vertical axis wind turbines do not need to be pointed into the wind and have been built in many different designs. Many wind turbines have problems operating or starting up in low wind speed conditions, require complex mechanisms to adjust to wind conditions and can have problems with noise and vibration. Existing models are rarely suitable for congested urban conditions or portability and are not always suitable to be manufactured from low cost materials. 
         [0004]    This invention is of a lightweight wind turbine that can be mounted either vertically or horizontally and is lightweight and portable. This wind generator utilizes an airfoil on the leading edge that is twisted into a three dimensional shape and consists of stackable units. Each unit can be inexpensively manufactured from lightweight materials, for example injection molded plastic or inflatable rubber. The units then connect together in a stack with the assembly held together by a central pole or cable. This design solves the problem of portability but retains the ability to provide for significant power generation when multiple units are stacked in series. One embodiment is of an efficient wind turbine that utilizes uniquely shaped three dimensional airfoil blades with opposing pitches of a helix twist angles to create beneficial wind flow during both low and high wind speed conditions. Other embodiments of this invention include methods of operation including multiple mounting configurations and the use of the turbine to generate power underwater. 
         [0005]    Several typical examples of turbines for wind power will be described, however none have the same characteristics as those of this invention. These examples represent the state of the art or the closest examples to this invention. In U.S. Pat. No. 7,362,004 B2, Becker describes a wind turbine made of straight outer airfoil blades and inner helical wing blades supported within a cage structure. As with many other wind turbines, a protective cage structure is required that adds expense, complexity and significant weight. In another example of a wind generator, Stephens describes a wind driven generator including a rotor comprised of blades in a cylindrical duct in U.S. Pat. No. 7,365,448 B2. This design is compact and much like a paddle wheel enclosed within a cylindrical housing. It also uses cams to put the blades into the wind. 
         [0006]    There are several commercial examples of portable wind generators. The Magenn Power Air Rotor System is a cylindrical turbine structure that is floated from 200-1,000 feet above ground transmitting energy through a tether. It is a lighter than air system that could be portable, but it is a complex design that is inherently costly to produce. The Quietrevolution QR5 has a helical design with three helical blades. Carbon fiber is used to manufacture the blades, which is a commonly used material for turbine blades. However, carbon fiber blades are costly and typically manufactured in small lots by hand. One example of a turbine that utilizes low cost plastic is Oregon Wind Corp.&#39;s Urban Turbine™. This design uses a helical blade on a central pole that is encaged in a steel or aluminum bracket. 
         [0007]    One type of wind turbine that has some similar features is the giromill or cycloturbine variety of vertical axis wind turbine. These are typically powered by three vertical airfoils attached by radial arms to a central rotating mast and were first described in U.S. Pat. No. 1,835,018 By Darrieus. Since radial airfoils are most effective at higher wind speeds, the cycloturbine variation alters the pitch of the airfoils to create drag for starting and then to generate greater lift to accelerate rotation. In a further evolution, Darrieus type vertical turbines have been built with helically twisted airfoil blades. The Quietrevolution and Turby brand commercial products have three vertical blades, each with a 60 degree helical twist. Start up for these models is typically achieved by using the generator as a motor. In U.S. Pat. No. 6,253,700 Gorlov teaches a helical turbine assembly that has primarily been used as a hydrofoil, producing energy from flowing water and works under the same principles as the Darrieus wind turbines. Savonius type wind turbines use scoops to create drag to turn a central shaft. Combinations of Darrieus and Savonius type units have been built with radial airfoils and cups attached to the central shaft to facilitate starting have been developed such as that in U.S. Pat. No. 3,918,839. In this design, starter rotors are used to only harness drag and facilitate rotation of the main shaft such that the exterior airfoil blades can then efficiently capture the wind energy. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    It is an object of this invention to provide for an improved wind energy generator. This invention is a wind turbine that utilizes airfoils in a unique design that are made of lightweight materials. Further, the turbine is manufactured as relatively small units by low cost production methods, and these portable units could be stacked in series to provide for significant power harvesting. It is a further object of this invention to provide a wind turbine made from a three dimensional twisted airfoil. The airfoil can contain two, three or four blades. 
         [0009]    It is a further object of this invention to provide a wind turbine comprised of airfoil blades made from a flexible material such that the blades bend towards the center of the turbine upon their return into the wind. This effectively reduces negative drag to further increase efficiency. 
         [0010]    It is a further object of this invention to provide for airfoils in which the twisted blades contain cut-outs, or hollow sections in blades. These hollow sections provide for a decreased weight of the turbine while not reducing its efficiency. 
         [0011]    It is a further object of this invention to provide a wind turbine that could be assembled from portable unit pieces to the desired length. It is a further object of this invention to provide a wind turbine that is lightweight and portable and requires minimum external support. 
         [0012]    It is a further object of this invention to provide a wind turbine constructed from inflatable airfoils. It is a further object of this invention to provide a wind turbine that could be easily mounted on a roof, a pole, or a horizontal cable. It is a further object of this invention to provide a wind turbine that is portable and could be transported and then mounted on a vehicle, or on a cable between two vehicles. It is a further objective of this invention to provide an inflatable wind generator with a swivel joint. This allows the inflatable design of the airfoil to be mounted between trucks, buildings, or other structures. It is a further object of this invention to provide for an airfoil generator system in which multiple airfoil units are mounted horizontally on wheel hubs. It is a further object of this invention to provide a turbine unit that can be used underwater to generate hydro power. The hollow plastic airfoil units of this invention could be filled with foam or another substance to increase rigidity for underwater use. 
         [0013]    It is a further object of this invention to provide for a double airfoil turbine that has an interior twisted airfoil and an outer airfoil. 
         [0014]    It is a further object of this invention to provide for airfoil wind turbines that provide better efficiency by utilizing airfoil segments with opposing pitches. 
         [0015]    It is a further object of this invention to provide an air turbine that is comprised of a central airfoil that is highly efficient at low wind speeds, and a plurality of circumferential airfoils to provide greater efficiency at higher wind speeds. Preferably, the assembly consists of three circumferential airfoils, although there can be fewer or greater than three. The spin of the air turbine rotates a central shaft that powers a generator. It is a further object of this invention to provide for an air turbine with a central airfoil and a plurality of circumferential airfoils in which said central airfoil is of a multiple bladed inverted helix. Preferably, said central airfoil consists of three blades although there can be fewer or greater than three blades. More preferably, the central airfoil is comprised of two joined parts; one half with a clockwise helix and one half with a counterclockwise helix. 
         [0016]    It is a further object of this invention to attach, via a spoked hub, a plurality of circumferential airfoils to the central twisted helix airfoil. The circumferential airfoils are single blades and can either be a flat or bent, or be comprised of two conjoined twisted segments of opposite pitch. In each case, said spoked hub must have arms long enough so that the central airfoil can spin without interference from the circumferential airfoils. 
         [0017]    It is a further object of this invention to provide for an improved energy generator in which a plurality of airfoils are positioned circumferentially around a central rotating shaft to power a generator. In this design, the circumferential airfoils taught previously are attached to each other via spoked hubs and no central airfoil is necessary. In a preferred embodiment, the circumferential airfoils are of a single bladed helical configuration. Further preferred is that multiple assemblies of these airfoils, connected by spoked hubs, be stacked with the pitch of the adjoining airfoil blades alternating between clockwise and counterclockwise. There can be any number of these blades. In another embodiment, some of the spoked hubs are removed and instead the circumferential pitched airfoil blades are connected to each other by means of integral tabs. For these configurations, the V-shaped counterclockwise and clockwise helix airfoil turbine can be asymmetrical or symmetrical or a combination of both in a helix profile. 
         [0018]    It is a further object of this invention to provide for an improved energy generator in which a plurality of circumferential airfoils are attached via a hub to a central rotating shaft. In this embodiment, the helical airfoils are wing tipped and the tipped ends are not attached to a hub. This type of configuration prevents roll off at the end of the airfoil for better efficiency. 
         [0019]    It is a further object of this invention to provide for a collapsible energy generator in which a plurality of hinged airfoil blades are mounted circumferentially to spoked hub on a rotating shaft. The blades are preferably of opposing pitches with a hinge in the middle and at the spoke connection. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    To improve the understanding of this invention, figures are provided to better describe examples of design and operation. These drawings represent examples of preferred embodiments but additional designs and operational conditions may also be included in this invention. While each example is described as a wind powered device comprised of airfoils, it is also possible to be utilized as a water powered device comprised of hydrofoils. 
           [0021]      FIG. 1  shows multiple airfoil units stacked together and mounted on a central pole. 
           [0022]      FIG. 2  shows two individual units of a twisted airfoil design with end caps. 
           [0023]      FIG. 3  shows the end view of a three vane airfoil. 
           [0024]      FIG. 4  is a flexible three vane airfoil. 
           [0025]      FIG. 5  is a four vane airfoil built from a stack of individual units. 
           [0026]      FIG. 6  shows a stack of airfoils with a hollow cutaway manufactured in the side of each blade. 
           [0027]      FIG. 7  shows the details of how a clockwise pitched airfoil is stacked upon a counter-clockwise pitched airfoil. 
           [0028]      FIG. 8  details a counter-clockwise pitched airfoil stacked upon a clockwise pitched airfoil. 
           [0029]      FIG. 9  shows multiple inflatable airfoil units tethered to a ground unit spool. 
           [0030]      FIG. 10  shows multiple airfoils mounted on a hub. 
           [0031]      FIG. 11  is an airfoil assembly with an attached swivel joint. 
           [0032]      FIG. 12  is an assembly with a twisted inner airfoil and outer airfoil. 
           [0033]      FIG. 13  is a wind turbine with an inverted clockwise and counterclockwise helical three bladed central airfoil and three circumferential bent airfoils. 
           [0034]      FIG. 14  is a wind turbine with an inverted clockwise and counterclockwise helical three bladed central airfoil and three circumferential inverted clockwise and counterclockwise helical airfoils. 
           [0035]      FIG. 15  is a wind turbine with three inverted clockwise and counterclockwise helical airfoils. 
           [0036]      FIG. 16  shows a stack of multiple airfoil wind turbines. 
           [0037]      FIG. 17  illustrates a collapsible airfoil assembly in which each of the airfoil blades is hinged. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0038]    An assembly, built of multiple individual airfoil units  1  is shown in  FIG. 1 . This assembly is mounted on a center pole  2  that is attached to a frame  3  to which a generator  4  is attached. This design is a true airfoil design and thus it is always exposed to the wind regardless of wind direction. The airfoil of this invention provide a leading edge like an airplane wing and thus provides separation of the airflow between the top and bottom sections of the airfoil in such a manner that it generates lift in addition to being pushed. The combination of lift and push is not typical for conventional wind turbines and provides for improved efficiency. 
         [0039]    The twisted airfoil, shown in  FIG. 2 , is comprised of multiple units that stack upon each other until the desired size is formed. Shown are the individual unit  5 , and the manner in which these units attach to each other  6 . Also shown are optional metal end caps  7  that fit into the bosses on both ends and provide a strong attachment point. Typically, wind turbines require a large size to produce significant power but large blades or turbine components made of the requisite lightweight materials require expensive hand made manufacturing whereas the stackable units of this invention could be manufactured by low cost processes including plastic injection molding. The design of the individual units is unique in that it includes both mechanical interconnects on the ends of each unit and a hollow square central section, in which a pole or cable runs, that acts as a keyway. For larger units, metal end caps could be inserted between sections to provide additional strength. Having individual units lowers manufacturing costs as well as transportation costs over having a one piece large turbine. 
         [0040]      FIG. 3  is an end view of a three blade twisted airfoil unit  8 . The airfoil blades are designed such that the wind  9  provides both push  10  and lift  11 .  FIG. 4  shows this airfoil unit constructed of a flexible material such that the blade tips  12  are pushed towards the center thus reducing the negative drag as the wind  13  contacts the uncapped side of the airfoil  14 . 
         [0041]      FIG. 5  shows a four-bladed airfoil  15  with the blades tilted at the optimum 33-degree angle from normal  16 . While this angle is believed to be the optimum for efficiency, it is understood that different angles of the airfoil into the wind will also be effective. 
         [0042]      FIG. 6  is a stack of twisted airfoil units in which a portion of the center of each blade is removed  17  to reduce the weight of the structure. Since the leading edge  18  is a true airfoil, the wind is deflected both over and under the blade and thus the center part of the blade is not needed to obtain the desired turbine effect. Note that this concept of hollowing the blade center could be done in other shapes and could be used on three- and four-bladed airfoils as well. 
         [0043]      FIG. 7  shows a configuration of how two airfoil units could be stacked together. A three blade airfoil unit with a clockwise spiral  19  is attached to a three blade airfoil unit with a counter-clockwise spiral  20 . In this configuration, the leading edge  21  directs the wind into the center of the turbine  22  and sets up the direction of spin with the curve of the airfoils  23 . The mid section of the airfoil  24  acts like a wing while the leading edge  25  is an airfoil can create both push and lift creating this spin. The section  26  is bent over to reduce drag as it rotates forward into the funnel zone. 
         [0044]      FIG. 8  shows a configuration in which a three blade counter-clockwise spiral airfoil  27  is attached to a three blade clockwise-spiral airfoil  28 . In this configuration the air stream converges towards the center foil  29  such that the force is concentrated increasing the efficiency of the system. The spirals also tend to direct the air outward in the opposite direction on the back side of the turbine. 
         [0045]    Although the helical turbines described herein could be mounted horizontally or vertically  FIG. 9  shows another operation mode in which lighter than air inflatable gangs of airfoils  30  are tethered by a cable  31  to a spool  32  that is mounted on a vehicle or on the ground. The inflatable airfoil is made of a rubber-like material and can be mounted inside a fabric cover to which cables could be attached. The hollow airfoil could be filled with lighter than air gas and floated on a cable tether into the atmosphere where the wind currents are strong. 
         [0046]    Another operation mode is shown in  FIG. 10  where gangs of airfoils  33  are mounted to common hubs  34  such that the cumulative mechanical energy is captured by the hub mounted generator  35 . The hubs are attached to a bracket  36  that is mounted on a swivel  37  that can rotate the entire assembly into the wind. There can be different variations of this configuration including designs in which each twisted airfoil assembly powers an individual generator. 
         [0047]    Another operation mode is shown in  FIG. 11  where the turbine  38  is mounted horizontally on a pole  39  that is attached to a plurality of cables on one side  40  and to a swivel joint  41  connected to a cable  42  on the other. The swivel joint prevents tangling of the cable, while the generator  43  captures the mechanical energy from the spinning pole. The twisted airfoil of this invention simply needs a pole or cable running through the center to support it, perhaps with metal end caps between individual sections. Most other turbines require a large heavy aluminum or steel cage structure with welded bracket hubs to hold it together. This increases the weight of this other system significantly. In addition to stationary structures, it is an objective of this invention to provide a wind turbine that can be easily mounted to mobile structures, such as trucks and boats. 
         [0048]      FIG. 12  shows yet another operational mode in which the built up twisted airfoil turbine  44  is combined with an outer airfoil  45 . This configuration improves efficiency in that the inside foil spins better at low wind speeds while the outer foil can better utilize higher wind speeds. 
         [0049]      FIG. 13  shows an example of a wind turbine comprised of a three dimensional inverted clockwise and counterclockwise central helical airfoil with three circumferential airfoils. The central airfoil is comprised of two separate three bladed winged airfoils, one winged helical airfoil in the counterclockwise direction  46  and the other winged helical airfoil in the clockwise direction  47 , that are joined together. They can also be molded as one continuous part. When a clockwise rotated airfoil is attached to a counter-clockwise rotated airfoil, the spinning action of this system in the wind will create a vacuum where the two halves meet. This effective pushing of the air into the center, while pushing it away from the center on the backside is not found in standard turbines. The wind turbine of this example also is comprised of three Darrieus type circumferential airfoils  48  that are bent outward to allow for the central airfoil to spin freely. The central airfoil is attached to a three spoke hub  49  on the top and the bottom; the spokes of which are attached to the three circumferential airfoils. The central airfoil is very efficient in low wind speed conditions and the three circumferential airfoils are very efficient at high wind speeds. Also visible is the mounting hub  50  and the central rotating shaft  51  that the turbine is attached to and powers the generator. Note that the circumferential airfoils are optional and can be omitted or can be configured differently, such as straight blades, with corresponding changes in the spokes. Although the central and circumferential airfoils may spin independently of each other, it is preferred that they are fixed in position relative to each other such that they spin together. In this way the central airfoil can effectively be used to start up the assembly in low wind conditions and the circumferential airfoils can impart greater efficiency once the turbine is spinning. While any number of circumferential airfoils can be utilized, three are used in the preferred embodiment. 
         [0050]    The central three bladed airfoil in the example shown in  FIG. 14  is the same as the central airfoil used in the previous figures with a counterclockwise helix half  52  joined to a clockwise helix half  53 . In this example the three circumferential airfoils are also comprised of a counterclockwise helix half  54  joined to a clockwise helix half  55 . The central and circumferential airfoils are all connected to a three spoke central hub  56  on each end. The leading edge of the two counterclockwise and clockwise airfoils direct the air outward while the back side of these two helices directs the fluid inwards. A vacuum is created by the air moving outward, and the air is rapidly pulled into the center leading to a very high efficiency. This wing shaped turbine airfoil design can self start in low wind conditions and work efficiently in high winds without the need for an interior drag foil. The improved three dimensional helical wing shape effectively produces drag in low winds and lift in high winds across the leading edge airfoil shape not found on conventional helix designs. This contrasts with the single Darrieus helix designs that have difficulty starting in low winds. 
         [0051]      FIG. 15  represents a similar wind turbine as the previous examples, except that the central airfoil is absent. Instead there are three circumferential airfoils, each with half of the airfoil helix clockwise  57  and half helix counterclockwise  58  joined by a three spoke hub  59  at the top, middle and bottom. Through the center of the assembly a rotating shaft  60  is attached to each of the three spoked hubs. 
         [0052]      FIG. 16  is an example of a similar multiple helix airfoil wind turbine to  FIG. 15  in which two units are stacked to provide for a larger more powerful unit. However in this example, the ends of each helical airfoil have a tab such that they could be connected directly to the next twisted airfoil. As shown, the central three spoked hub of  FIG. 15  is no longer necessary in this configuration. Visible is the circumferential airfoil blade segment with a clockwise helix  61  and a segment with a counterclockwise helix  62 . The circumferential airfoils are connected by three spoke hubs  63  and a central rotating shaft  64  powers the generator. 
         [0053]    An example of the type of wind generator described by this invention in a collapsible configuration is shown in  FIG. 17 . In this model, the counterclockwise helical half of the airfoil  65  is connected to the clockwise helical half  66  by a hinge  67 . Hinges  68  and  69  connect the airfoils to spoked hubs  70  and  71  that are attached to the central rotating shaft  72 . This entire assembly can collapse for a very portable energy generator. This configuration still provides for the improved efficiency of the opposed pitched blade combination, yet in a portable design.