HORIZONTAL AXIS AIRFOIL TURBINE

Abstract

A Horizontal Axis Airfoil Turbine (HAAT) for harnessing wind power is presented. The horizontal axis airfoil turbine has an airfoil design configured for low cut-in-speed and operational speeds, and for high torque operation. Multiple airfoil blade tips depend inwardly from a structural shroud along the periphery of the shroud. A number of full airfoil blades depend inwardly from the shroud along spokes providing mechanical engagement between the shroud and a central hub. Advantages are derived from a large wind swept area distributed to maximize leverage in order to enable high torque operation.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Canadian Application No. 2,732,543, filed Feb. 23, 2011, the entirety of which is hereby incorporated by reference.

TECHNICAL FIELD

The horizontal axis airfoil turbine described herein relates to the general field of wind turbines, and in particular to wind turbines operating at higher torque and lower cut-in-speed.

BACKGROUND

In the field of wind power generation, harnessing wind power has been sought for some time. Initial designs concentrated on harnessing wind power for conversion into a mechanical motive force to actuate various machinery, for example for cutting wood or grinding seed. The simplest of these designs included a number of sails attached to a number of spokes on a hub and are generally referred to as wind mills emphasizing the early need for a motive force in processing raw materials. Some prior art wind mill designs include what can be generally referred as paddles instead of the sails. Such windmill designs operate simply by converting wind forces impinging over an area into a motive force employing general principles of sailing a sail ship.

Relatively recent research in fixed wing powered flight has brought an understanding of aerodynamic forces, such as lift and drag, which lead to aircraft wings having general tear shape cross-sections and to propellers having tear shape cross-section. War efforts have furthered the understanding of fixed wing power flight providing extensive empirical knowledge leading to extensively cataloguing the properties of airfoil cross-sections with an emphasis on tear shape derived airfoils. Recently propellers have been used “in reverse”, so to speak, to generate wind power, typically to convert wind forces into electrical power via an electrical power generator. These propeller inspired designs will be referred to herein as wind propeller generators. Currently wind power generation is dominated by wind propeller generators with three blades used for both residential applications and large wind farms. The cut-in-speed for this current technology is typically between 3 to 4.5 meters per second (“m/s”), wherein cut-in-speed is the speed at which the power production starts. Thus conventional wind propeller generators generally require high start speeds, which limits deployment to geographic regions benefiting from high winds. Additionally, despite requiring high wind speeds wind propeller generators generally produce low motive forces available for power conversion.

Much of the knowledge regarding the general field of aerodynamics is best supported by experimentation. In numerous cases theoretical models only approximate experimental reality due to air drag and air turbulence effects, which are not fully understood presently despite enormous prior research and development efforts. Theoretical analysis can explain linearly varying real world phenomena, a phrase reserved to characterize phenomena well approximated by some simple well behaved mathematical function(s). It is generally accepted and understood that actual real world phenomena do not fit perfectly such theoretical mathematical analysis. The phrases “well approximated” and “well behaved” have varying definitions: “well approximated” implies due consideration being given to measurement error, whereas “well behaved” implies smoothly varying with respect to some parameter. Measurement error is minimized in respect of laminar air flows; however, turbulent airflow defies functional mathematical modeling. Largely, turbulent airflow is modeled statistically. Real airflow phenomena are anything but well behaved and smoothly varying. A number of parameters such as air compressibility, air density, air pressure, etc. are not smoothly varying. For example, air compressibility and air density vary with temperature having abrupt discontinuities with temperature and air pressure (dew point); air pressure varies with airflow speed and airflow direction, having discontinuities at the sound barrier; etc. Much work has been done and much work remains to be done in aerodynamics in general and therefore in the field of wind power generation.

There is a need in the wind power generation industry to address the above-mentioned issues in order to more efficiently produce wind power.

SUMMARY

It was found that one of the prior art problems may best be described in terms of an acceptance by the scientific community that the energy in the wind is proportional to the cube of the wind velocity. In view of this relationship, some sources claim that the cut-in-speed does not matter because there is little energy in the wind at low speed levels. The present solution is contrary to this position:

It is pointed out that, assuming all other parameters remaining constant, employing the Weibull distribution for the wind in a chosen geographic location, each cut-in-speed decrease of 0.5 m/s results in an annual increase in the available energy by about 6 to 7%. The corresponding energy extraction percentage increase depends in a synergistic way on location, energy conversion apparatus and cut-in-speed reduction. Thus, it has been found that the cut-in-speed is actually very important, not only from the point view of energy production by also when considering areas apt for deployment. Geographic areas with lower wind speed particularly benefit from a lower cut-in-speed due to the fact that harnessing wind energy can be economically viable in these additional areas.

The proposed solution provides increased wind power production employing a Horizontal Axis Airfoil Turbine (HAAT) having an airfoil design configured for low cut-in-speed and operational speeds, and for high torque operation. HAAT implementations overcome the disadvantages of current technology by providing higher torque at all wind speeds. The main advantage of the proposed solution over conventional designs is that the increased torque at lower wind speed means that the cut-in-speed is reduced and therefore additional wind energy can be harnessed. While an increase in torque is associated with an increase of power and whereas a decrease in rotational speed is associated with a decrease in output power, field testing indicates that the overall effect is an increase in power out compared to conventional technologies.

In accordance with the proposed solution, the HAAT apparatus utilizes short radial airfoils that are primarily mounted on a periphery of the turbine, but include some full radius airfoils. The airfoil arrangement maximizes torque, yet captures wind energy across the cross-sectional area of the turbine.

In accordance with a broad aspect, there is provided a horizontal axis airfoil turbine for harnessing wind energy to provide a motive force for use in a power generator, the horizontal axis airfoil turbine comprising: a ring configured to provide structural support for an airfoil blade arrangement; a plurality of airfoil blade tips mechanically connected to, and depending radially from the ring, the blade tips being configured to interact with an airflow incident thereon, the airflow causing a deflection of the blade tips in a direction of rotation of the ring; a plurality of spokes mechanically connected to, and depending radially inwardly from, the ring, each spoke extending from the ring to a central hub, the spokes providing structural support for the ring and the airfoil blade arrangement; a plurality of full airfoil blades, each full blade being configured to provide airfoil characteristics to a corresponding spoke for reducing turbulent airflow past the spoke, mechanical engagement between the spokes and the hub providing torsional force transfer to the hub, the hub transforming the torsional force into the motive force for use in the power generator.

In other aspects, the ring further comprises an aerodynamically shaped leading edge for reducing resistance to incident wind. The ring may also have a structural shroud preventing radial airflow spill over distal ends of blades in the airfoil blade arrangement, each airfoil blade tip depending radially inwardly from the ring. The structural shroud may have an airfoil tear shaped cross-section for reducing turbulent airflow around the turbine. Each airfoil blade tip may be shaped to operate under one of drag or lift conditions causing the deflection of the blade tip in the direction of rotation of the ring and each airfoil blade tip may have an airfoil tear shaped cross-section for reducing turbulent airflow past the airfoil blade tip. Moreover, each airfoil blade tip may have an angle of attack between 30° and 50° and in particular substantially 40°. Each airfoil blade tip may extend radially inwardly from the ring between 10 to 40 percent of a radius of the ring and in particular substantially 25 percent of the radius of the ring.

In still other aspects, each full airfoil blade may be shaped to operate under one of drag or lift conditions causing additional deflection of the full airfoil blade in the direction of rotation of the ring. Each full airfoil blade having an airfoil tear shaped cross-section for reducing turbulent airflow past the full airfoil blade. Moreover, each full airfoil blade may have an angle of attack between 30° and 50° and in particular substantially 40°. Each full airfoil blade may extend radially inwardly from the ring between 80 to 95 percent of a length of the corresponding spoke and in particular substantially 88 percent of the length of the corresponding spoke.

In other aspects, each airfoil blade tip and each full airfoil blade may have a substantially equal angle of attack. The full airfoil blades may comprise an odd number of full airfoil blades for reducing harmonic resonant vibration and the odd number of full airfoil blades may be a prime number of full airfoil blades.

Advantages over conventional designs are derived from a lower wind speed required to start up the horizontal axis airfoil turbine and from higher torque operation in general.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the HAAT will become more apparent from the following detailed description of several aspects of the proposed solution illustrated by way of example, and not by way of limitation, in detail in the figures, wherein:

FIG. 1 is a schematic diagram illustrating, in accordance with one embodiment of the proposed solution, a front view of a horizontal axis airfoil turbine;

FIG. 2 is a schematic diagram illustrating, in accordance with one embodiment of the proposed solution, a rear view of the horizontal axis airfoil turbine;

FIG. 3 is a schematic diagram illustrating, in accordance with one embodiment of the proposed solution, a perspective view of the horizontal axis airfoil turbine;

FIG. 4 is a schematic diagram illustrating a perspective view of the horizontal axis airfoil turbine hub;

FIGS. 5a, 5b and 5c illustrate examples of shroud cross-sections in accordance with the proposed solution: FIG. 5a illustrates a low profile shroud having an aerodynamic shape; FIG. 5b illustrates a tear shaped shroud in cross-section, and FIG. 5c illustrates a composite shroud having an overall aerodynamic shape;

FIG. 6 is a schematic diagram illustrating a cross-sectional view of a prototype airfoil blade employed in a horizontal axis airfoil turbine implemented in accordance with the proposed solution;

FIG. 7 is a plot of actual comparative rotational speed versus wind speed measurements for a conventional wind propeller generator and horizontal axis airfoil turbines implemented in accordance with the proposed solution; and

FIG. 8 is a plot of actual comparative torque versus wind speed measurements for conventional wind propeller generators and horizontal axis airfoil turbines implemented in accordance with the proposed solution.

In the attached figures like reference numerals indicate similar parts throughout the several views. As will be realized, the HAAT is capable for other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the present description.

DETAILED DESCRIPTION

The instant disclosure is provided to further explain in an enabling fashion the best modes of making and using various embodiments in accordance with the proposed solution. The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the HAAT and is not intended to represent the only embodiments contemplated by the inventor. The detailed description includes specific details for the purpose of providing a comprehensive understanding of the HAAT. However, it will be apparent to those skilled in the art that the HAAT may be practiced without some of these specific details. For certainty, while the following description of the proposed solution concentrates on describing aspects of the horizontal axis airfoil turbine, some consideration will be been given, where appropriate, to aspects of an electrical generator needed to convert wind power to electrical power, and with respect to an overall necessary support structure of a typical installation.

In accordance with a preferred embodiment of the proposed solution, a frontal view of a Horizontal Axis Airfoil Turbine (HAAT) is illustrated in FIGS. 1 to 3. HAAT 10 includes a central hub 20 configured to connect the HAAT 10 to a generator (not shown), for example an electrical power generator, via a shaft (not shown), for example in the form of a support rod. The shaft provides motive force transfer from the HAAT 10 to the electrical power generator for conversion. The hub 20 is configured to provide mechanical support for the HAAT 10 while aggregating motive forces in providing torque. Hub 20 includes a faired design best shown in FIG. 3, for example having an aerodynamic shape, in order to reduce air drag and/or to reduce turbulence. The HAAT is not limited to hub 20 including a spherical section nose cone. It is envisioned that the hub 20 can be configured to actively minimize air drag and/or to minimize turbulence.

With reference to FIG. 4, illustrating a hub 20 without the nose cone, hub 20 includes a bore 22 providing mechanical engagement with the shaft. Hub 20 also includes a number of spoke bores 24 configured to provide mechanical engagement and support for a number of spokes 30.

Returning to FIGS. 1 to 3, the overall mechanical support structure of the HAAT 10 includes spokes 30 which extend from the hub 20 to an outer ring 40. The number of spokes 30 can be varied to optimize various structural aspects of the HAAT 10, for example an odd number of spokes 30 reduces vibration. Preferably a prime number of spokes 30 is employed to minimize resonant harmonics.

Ring 40 can include a substantially cylindrical structure. Preferably ring 40 is a cylindrical structural shroud having an aerodynamic cross-section to reduce drag. The HAAT is not limited to shroud 40 having a tear shaped cross-section as shown in FIG. 5B. A variety of airfoil profiles can be employed. An airfoil profile providing superior structural support and turbulent flow reduction is preferred. FIGS. 5A, 5B and 5C illustrate examples of cross-sections through shrouds 40. FIG. 5A illustrates a low profile shroud 40 having an aerodynamic shape. FIG. 5B illustrates a tear shaped shroud 40 in cross-section. FIG. 5C illustrates a composite shroud 40 having an overall aerodynamic shape.

With the spokes 30 providing mechanical connectivity between hub 20 and structural shroud 40, shroud 40 rotates with the hub 20. Such a rotating structural shroud 40 has the potential to store a large angular momentum (inertia). The angular momentum contribution of the shroud 40 is proportional to mass of the shroud 40 multiplied by the corresponding square of the radius of the shroud 40, and is proportional to the angular velocity of rotation. The angular momentum and inertia of the HAAT 10 have an impact on the implementation and operation thereof. The disadvantage of high angular momentum implementations is that yaw control can be more difficult. In some implementations a larger rudder may be required. In other implementations, a separate motor driven yaw control system may be required for larger units. In yet other implementations, the center of mass of the HAAT may have to be displaced further from the yaw axis to provide adequate drag induced yaw control. In order to minimize the angular momentum, HAAT implementations would benefit from utilizing the lightest economically viable and suitable (e.g. water resistant, corrosion resistant) materials available which provide sufficient strength. For example, durable non-corrosive carbon fiber reinforced plastic, fiberglass and other composites can be used. As well, angular momentum can be reduced by minimizing the amount of material used, for example by employing spin molding techniques to produce hollow shroud 40. As another example illustrated in FIG. 5C, structural support can be provided by a support structure 44 within the shroud 40 made of a first dense high strength material, while the aerodynamic surface of the shroud 40 can be provided by a shell 46 made of a second low density material. The leading edge 42 (i.e. edge facing the wind) of the shroud 40 is aerodynamically shaped to reduce resistance to the wind.

A balance needs to be struck between the need to minimize angular momentum to reduce stress on the anchoring structure of the HAAT 10 in operation, and operability of the HAAT 10 in gusty conditions. Higher inertia provides a more stable HAAT 10 for operation in gusty conditions, the advantage being less variation in power output easing operational requirements of the electrical power generator. Field tests have shown that the HAAT 10 sped up slower with increased angular momentum implementations; however, advantageously a HAAT 10, having a large angular momentum, slowed down more slowly in response to decreasing wind speed.

In accordance with the proposed solution, a number of airfoil blade tips 50 cooperate together in harnessing wind power (at slow speed) along the periphery of the shroud 40, such that in operation the structural shroud 40 rotates with the blade tips 50 it supports. As shown in FIGS. 1 to 3, a large number of short length airfoil blade tips 50 are disposed along the circumference of the shroud 40 depending inwardly from the shroud 40 providing high torque. For example, the airfoil blade tips 50 can extend between 10 to 40 percent of the radius of the shroud 40, preferably 25 percent. From an angular momentum perspective, the airfoil blade tips 50 add angular momentum to the HAAT 10 while the airfoil blade tips 50 are subjected to wind forces over a large peripheral wind swept area exerting a greater torsional force due to a greater mechanical advantage at reduced bulk per blade compared to conventional wind propeller generator designs.

FIG. 6 illustrates an airfoil blade tip 50 in cross-section. Blade tip 50 illustrates an example of angular momentum reduction wherein blade tip 50 can be produced by extrusion techniques. Blade tip 50 has an overall airfoil shape with a rounded leading edge 52 and a tipped trailing edge 54. A longitudinal bore 56 provides anchoring, for example by receiving a short spoke, a support rod or a bolt. While FIGS. 1 to 3 show short spokes depending inwards from the shroud 40 and extending the length of the corresponding airfoil blade tip 50, the HATT is not limited thereto. For example, each airfoil blade tip 50 can be made of structurally rigid materials, such as but not limited to: aluminum, high density plastic, etc. employing a shot bolt and countersunk nut to hold the airfoil blade tip 50 in place. If the angle of attack of the blade tips does not require adjustment, it is envisioned that the blade tips 50 can be welded or bonded to the shroud 40 by employing suitable attachment techniques. Airfoil blade tips 50, can also be mounted to depend outwardly from the shroud 40. In accordance with the proposed solution, airfoil blade tips 50 preferably depend inwardly from the shroud 40 in order to prevent radial air spill. As the wind impinges on the airfoil blade tips 50 the airfoil blade tips 50 rotate, which in turn imparts a centrifugal component to the air as the air transfers linear momentum into HAAT 10 angular momentum. Unimpeded, the centrifugal component tends to push the air radially outwards and past the distal end of each airfoil blade tip 50. Employing the shroud shaped ring 40 stops radial motion of the wind air providing an increased momentum transfer. Advantageously, the HAAT 10 provides increased torque.

Referring back to FIGS. 1 to 3, in accordance with the proposed solution, a number of full airfoil blades 60 cooperate together with the airfoil blade tips 50 to capture wind power in the centre of the HAAT 10 closer to the hub 20. Full airfoil blades 60 depend inwardly from shroud 40 and benefit from reduced air spill.

Without limiting the scope, each full airfoil blade 60 can have the same cross-section as the airfoil blade tips 50 illustrated in FIG. 6. The bore 56 receives each spoke 30 and therefore the number of full airfoil blades 60 corresponds to the number of spokes 30 employed. In view of the vibration and harmonic resonance considerations presented hereinabove, an odd/prime number of full airfoil blades 60 are employed. Balance considerations lead to employing an equal number of airfoil blade tips 50 between full airfoil blades 60 and therefore to an odd total number of airfoil blades 50, 60. While six full airfoil blades 60 are illustrated in FIGS. 1 to 3 and employed in tested prototypes, three or five full airfoil blades 60 are preferred, however, seven or more are not excluded. While larger numbers of airfoil blade tips 50 would increase the swept area, the closer the airfoil blades 50, 60 are to each other, the more slipstreams from each airfoil blade 50, 60 interfere with each other creating turbulent air flow behind the HAAT 10 which creates to drag against the HAAT 10 depleting available power. The number of airfoil blades 50, 60 can be increased compared to conventional wind propeller generator designs because fewer full airfoil blades 60 extend in the center of the HAAT 10 providing ample spacing therebetween, and along the shroud 40 larger spacing is available between all airfoil blades (50, 60).

While each full airfoil blade 60 provides a corresponding spoke 30 with an aerodynamic shaped shell to reduce turbulence while harnessing additional wind power, the full airfoil blades 60 need not extend from the shroud 40 all the way to the hub 20. For example full airfoil blades 60 extend radially inwardly from the shroud 40 between 80 to 95 percent of the length of the corresponding spokes 30, typically 88 percent. Spokes 30 rotate slower at the hub 20 and therefore contribute less turbulence. It has been discovered that a crossover point exists along the radius of the HAAT 10 for spokes 30 of constant angle of attack and constant chord length where the aerodynamic cross-section of each full airfoil blade 60 no longer provides a power extraction advantage, on the contrary the full airfoil blade 60 simply stirs air. The full airfoil blades 60 can extend inwardly only to the crossover point for the intended rotational speed range of the HAAT 10. Such limited extension can also reduce bulk and angular momentum. In accordance with the proposed solution all surfaces of the HAAT 10 are aerodynamically shaped. However this is not an absolute requirement, for example the spokes 30 near the hub 20 can be sufficiently aerodynamic.

While FIGS. 1 to 3 illustrate airfoil blade tips 50 and full airfoil blades 60 of constant cross-section, the scope of the HAAT is not limited thereto. Constant cross-section construction benefits from simplified manufacturing. For example, if variable cross-section construction is employed, the cross-section can be made to taper from the shroud 40 to the crossover point.

It is envisioned that the airfoil blade tips 50 and full airfoil blades 60 can have either different cross-sections or different angles of attack. For example, the cross-section and/or angle of attack of the airfoil blade tips 50 can be configured to provide low cut-in-speed operation, while the cross-section and/or angle of attack of the full airfoil blades 60 can be configured to control rotational speed and therefore angular momentum.

Various airfoil cross-sectional shapes permit the airfoil blades to operate either under lift conditions or under drag conditions. Under drag conditions the airfoil blades 50/60 act as sails being deflected by the wind to cause HAAT 10 rotation, while under lift conditions the airfoil blades 50/60 minimize drag being deflected by an experienced lift which causes HAAT 10 rotation. Depending on the angle of attack, an airfoil blade having a cross-sectional shape capable of operation under lift conditions can be configured to operate under drag conditions. The available wind speed factors into which operating conditions are appropriate.

For certainty, the proposed solution includes a variation in the number, shape, dimensions and angle of attack for the airfoil blades 50/60 depending on the wind speed and diameter of the HAAT 10.

It is noted that current thinking in the art is that, in view of economic considerations, increasing rotor blade length of a wind propeller generator is cheaper and easier to sustain high wind speed operation than to utilize a shroud around a propeller. However, increasing rotor blade length without a shroud is limited by: material strength, angular momentum considerations, blade vibration, drag which increases nonlinearly with blade length, and at an extreme by tips rotating at very high speeds incompatible with the wind speed. In contrast, the shroud 40 proposed not only provides a support structure for the airfoil blade tips 50 but also restricts radial air spill.

Experiments and Results:

With reference to FIG. 7, field testing outdoors has confirmed that the rotational speed for HAAT wind turbines JA306 and JA246621 implemented in accordance with the proposed solution, was less than that for a commercially available wind propeller generator Prop51. Because, both centrifugal forces and vibration increase with the square of the speed, the wind turbines implemented in accordance with the proposed solution operating at lower speeds benefit from improved structural stability. Further benefits are derived from lower rotational speeds due to the rotational speed dependence of angular momentum which minimizes stresses on the HAAT support structure (not shown). Overall, the radial distribution of the wind swept area was closer to the outer ring (shroud 40) of the HAAT wind turbines than for the wind propeller generator(s). Comparatively, the angular momentum of the HAAT prototypes was estimated to be eight or nine times greater than the angular momentum of the wind propeller generator(s) tested.

A variety of angles of attack were tried with airfoil blades 50, 60 having the cross-sectional profile shown in FIG. 6. An angle of attack of approximately 40° produced the best results. For certainty, the HAAT is not limited to the airfoil blade cross-sectional profile illustrated in FIG. 6 or to the 40° angle of attack.

Advantageously, the total wind swept area of the prototype illustrated in FIGS. 1 to 3 is more than half of the inner area of the shroud 40, which is about five times the normalized swept area of a wind propeller generator, thereby a significantly increased wind power was expected.

FIG. 8 illustrates comparative torque measurements at different wind speeds for both conventional design wind propeller generators Prop51 and Prop69, and HAAT wind turbines JA306 and JA246621 implemented in accordance with the proposed solution. Advantageously, in the low wind speed operational range of the HAAT prototypes, the HAAT prototypes have been measured to have developed substantially larger torque. The increased torque developed in accordance with the proposed solution, confirmed the expectation.

As would be apparent to a person skilled in the art, the rotational speed vs. wind speed plots (FIG. 7) and the torque vs. wind speed plots (FIG. 8) show real outdoors gusty conditions. The data confirms the expected benefits of increased torque and decreased cut-in-speed. Employing HAAT derived wind turbines opens access to large geographic areas for deployments harnessing wind power, even under gusty wind conditions.

Surprisingly, the gusty wind conditions have shown that the low cut-in-speed overcome static friction on start up better and the additional angular momentum prevented, through inertial forces, the HAAT prototypes from falling back into the static friction regime between gusts.

Although various aspects of the proposed solution have been described herein including for example multiple airfoil blade tips, a full airfoil blades, and a shroud having an aerodynamic cross-section, it is to be understood that each of these features may be used independently or in various combinations, as desired, in a horizontal axis airfoil turbine.

While the above description of the proposed solution concentrates on the horizontal axis airfoil turbine, some consideration has been given in the above with respect to aspects of an electrical generator needed to convert wind power to electrical power, and with respect to an overall necessary support structure of a typical installation. For example, odd number airfoil implementations are preferred in order to reduce harmonic resonant vibration, low inertial mass designs are preferred in order to reduce toppling, shear, angular momentum restorative forces, etc.

The previous description of the disclosed embodiments has been provided to enable any person skilled in the art to make or use the present horizontal axis airfoil turbine described. Various modifications to those embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the horizontal axis airfoil turbine. Thus, the present horizontal axis airfoil turbine is not intended to be limited to the embodiments shown herein, but is to be accorded the full scope consistent with the claims, wherein reference to an element in the singular, such as by use of the article “a” or “an” is not intended to mean “one and only one” unless specifically so stated, but rather “one or more”. All structural and functional equivalents to the elements of the various embodiments described throughout the disclosure that are known or later come to be known to those of ordinary skill in the art are intended to be encompassed by the elements of the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 USC 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or “step for”. The horizontal axis airfoil turbine is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.

Claims

1. A horizontal axis airfoil turbine for harnessing wind energy to provide a motive force for use in a power generator, the horizontal axis airfoil turbine comprising:

a ring configured to provide structural support for an airfoil blade arrangement;

a plurality of airfoil blade tips mechanically connected to, and depending radially from said ring, said blade tips being configured to interact with an airflow incident thereon, said airflow causing a deflection of said blade tips in a direction of rotation of said ring;

a plurality of spokes mechanically connected to, and depending radially inwardly from, said ring, each spoke extending from said ring to a central hub, said spokes providing structural support for said ring and said airfoil blade arrangement;

a plurality of full airfoil blades, each full blade being configured to provide airfoil characteristics to a corresponding spoke for reducing turbulent airflow past said spoke, mechanical engagement between said spokes and said hub providing torsional force transfer to said hub, said hub transforming said torsional force into the motive force for use in the power generator.

2. The horizontal axis airfoil turbine as claimed in claim 1, said ring further comprising an aerodynamically shaped leading edge for reducing resistance to incident wind.

3. The horizontal axis airfoil turbine as claimed in claim 1,

said ring further comprising a structural shroud preventing radial airflow spill over distal ends of blades in said airfoil blade arrangement; and

each said airfoil blade tip depending radially inwardly from said ring.

4. The horizontal axis airfoil turbine as claimed in claim 3, said structural shroud having an airfoil cross-section for reducing turbulent airflow around said turbine.

5. The horizontal axis airfoil turbine as claimed in claim 4, said structural shroud having an airfoil tear shaped cross-section.

6. The horizontal axis airfoil turbine as claimed in claim 2, each said airfoil blade tip shaped to operate under one of drag or lift conditions causing said deflection of said blade tip in said direction of rotation of said ring.

7. The horizontal axis airfoil turbine as claimed in claim 6, each said airfoil blade tip having an airfoil tear shaped cross-section for reducing turbulent airflow past said airfoil blade tip.

8. The horizontal axis airfoil turbine as claimed in claim 6, each said airfoil blade tip having an angle of attack between 30° and 50°.

9. The horizontal axis airfoil turbine as claimed in claim 8, said airfoil blade tip angle of attack being substantially 40°.

10. The horizontal axis airfoil turbine as claimed in claim 3, each said airfoil blade tip extending radially inwardly from said ring between 10 to 40 percent of a radius of said ring.

11. The horizontal axis airfoil turbine as claimed in claim 10, each said airfoil blade tip extending radially inwardly from said ring substantially 25 percent of said radius of said ring.

12. The horizontal axis airfoil turbine as claimed in claim 2, each said full airfoil blade shaped to operate under one of drag or lift conditions causing additional deflection of said full airfoil blade in said direction of rotation of said ring.

13. The horizontal axis airfoil turbine as claimed in claim 12, each said full airfoil blade having an airfoil tear shaped cross-section for reducing turbulent airflow past said full airfoil blade.

14. The horizontal axis airfoil turbine as claimed in claim 12, each said full airfoil blade having an angle of attack between 30° and 50°.

15. The horizontal axis airfoil turbine as claimed in claim 14, said full airfoil blade angle of attack being substantially 40°.

16. The horizontal axis airfoil turbine as claimed in claim 2, each said full airfoil blade extending radially inwardly from said ring between 80 to 95 percent of a length of said corresponding spoke.

17. The horizontal axis airfoil turbine as claimed in claim 16, each said full airfoil blade extending radially inwardly from said ring substantially 88 percent of said length of said corresponding spoke.

18. The horizontal axis airfoil turbine as claimed in claim 2, wherein each said airfoil blade tip and each said full airfoil blade have a substantially equal angle of attack.

19. The horizontal axis airfoil turbine as claimed in claim 2, said plurality of full airfoil blades comprising an odd number of said full airfoil blades for reducing harmonic resonant vibration.

20. The horizontal axis airfoil turbine as claimed in claim 19, said odd plurality of full airfoil blades comprising a prime number of said full airfoil blades for minimizing harmonic resonant vibration.