Patent Description:
Horizontal-axis wind turbines for generating electricity from rotational motion are generally comprised of one or more rotor blades each having an aerodynamic body extending outwards from a horizontal shaft that is supported by, and rotates within, a wind turbine nacelle. The rotor blades are examples of structures adapted to traverse a fluid environment, where the environment is primarily ambient air. The nacelle is supported on a tower which extends from the ground or other surface. Wind incident on the rotor blades applies pressure causing the rotor blades to move by rotating the shaft from which they extend about the horizontal rotational axis of the shaft. The shaft is, in turn, associated with an electricity generator which, as is well-known, converts the rotational motion of the shaft into electrical current for transmission, storage and/or immediate use. Horizontal-axis wind turbines are generally very well-known and understood, though improvements in their operation to improve the efficiency of power conversion and their overall operational characteristics are desirable.

Incident wind at even low speeds can cause the rotor blades to rotate very quickly. As would be well-understood, for a given rotational velocity, the linear velocity of a rotor blade is lowest in the region of its root - the portion of the rotor blade proximate to the shaft. Similarly, the linear velocity of the rotor blade is highest in the region of its wingtip - the portion of the rotor blade distal from the shaft. Particularly at higher linear velocities, aspects of the rotor blade can generate significant aeroacoustic noise as the rotor blade rapidly "slices" through air along its rotational path. This noise can be quite uncomfortable for people and animals in the vicinity to witness. However, the noise can also be an indicator that operation is not efficient, and maximum wingtip speed can actually be limited by such inefficiencies.

For example, aeroacoustic noise emitted from the region of the wingtip of a rotor blade is generally called tip vortex noise. Tip vortex noise is an indicator that a scattered vortex is being created due to the configuration of the rotor blade at the wingtip, which decreases the efficiency of the blade by creating undue drag.

It is known to modify the configuration of the rotor blade in the region of the wingtip, such as by having aspects of the rotor blade in the wingtip region deviate only from the generally linear path of the rest of the rotor blade at some angle. Such deviations have become known as winglets, and various configurations of winglets have been used to improve the efficiencies of wind turbines as a whole by limiting the vortices that may be created upon rotation of the rotor blades. <CIT> discloses a winglet for a rotor blade of a wind turbine. The effect of modifying the radial spanwise radius of the winglet, which modifies the sweep is described in this document.

At the present time, such winglets are known to either deviate into the oncoming wind incident with the rotor blade or to deviate away from the oncoming wind in the direction of the tower, without going forward or rearward of the leading or trailing edges of the rest of the rotor blade. These two prevalent winglet configurations have been shown to reduce the load on the rotor blade and to reduce the chance of blade failure by allowing the wind that is incident on the rotor blade to exit the wingtip smoothly. However, such configurations have addressed only the handling of wind incident on the front of the rotor blades that causes the rotor blades to rotate, and have not considered improvements in how the rotor blades might operate in respect of the air that is encountered at highspeed by the rotor blades during their high-speed traversal of their rotational path. In particular, the wind incident on the front of the rotor blades may reasonably be moving at only up to about thirty (<NUM>) kilometres per hour (kph), whereas the linear speed of the wingtip region as it traverses its rotational path may reasonably reach up to three hundred and twenty (<NUM>) kph for a very rapidly- rotating rotor blade. The higher-speed in this respect can be responsible for the bulk of the noise and inefficiencies of a wingtip.

In accordance with an aspect, there is provided a structure according to claim <NUM>.

Other aspects and their advantages will become apparent to the skilled reader upon review of the following.

Embodiments of the invention will now be described with reference to the appended drawings in which:.

Reference will now be made in detail to the various embodiments of the invention, one or more examples of which are illustrated in the figures. Each example is provided by way of explanation of the invention, and is not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the present invention includes such modifications and variations.

<FIG> is a side elevation view of a horizontal axis wind turbine <NUM>, according to the prior art. Wind turbine <NUM> includes a tower <NUM> supported by and extending from a surface S, such as a ground surface. Supported by tower <NUM>, in turn, is a nacelle <NUM> extending horizontally. A hub with a spinner <NUM> is rotatably mounted at a front end of nacelle <NUM> and is rotatable with respect to nacelle <NUM> about a rotation axis R. Spinner <NUM> receives and supports multiple rotor blades <NUM> that each extend outwardly from spinner <NUM>. Rotor blades <NUM> catch incident wind W; flowing towards the wind turbine <NUM> and are caused to rotate. Due to their being supported by spinner <NUM>, rotor blades <NUM> when rotating cause spinner <NUM> to rotate about rotation axis R thereby to cause rotational motion that can be converted in a well-known manner into usable electrical or mechanical power. In this sense, rotor blades <NUM> are each structures adapted to traverse a fluid environment, where the fluid in this embodiment is ambient air. Nacelle <NUM> may be rotatably mounted to tower <NUM> such that nacelle <NUM> can rotate about a substantially vertical axis (not shown) with respect to tower <NUM>, thereby to enable rotor blades <NUM> to adaptively face the direction from which incident wind W; is approaching wind turbine <NUM>. A nose cone <NUM> of generally a uniform paraboloidal shape is shown mounted to a front end of spinner <NUM> to deflect incident wind W; away from spinner <NUM>.

<FIG> is a front perspective view of one of rotor blades <NUM> in isolation. Rotor blade <NUM> includes an elongate body that extends from a root <NUM> through a main section <NUM> to terminate at a wingtip <NUM>. Root <NUM> extends from nacelle <NUM> when attached thereto or integrated therewith, whereas wingtip <NUM> is the portion of the elongate body that is distal to nacelle <NUM>. The elongate body has a leading edge <NUM> and a trailing edge <NUM>, where leading edge <NUM> leads trailing edge <NUM> when rotor blade <NUM> is in motion rotating with nacelle <NUM> about rotation axis R in the direction D. A suction side <NUM> of the elongate body is shown in <FIG>, and a pressure side <NUM>, shown in dotted lines, is opposite the elongate body from suction side <NUM>.

<FIG> is a front perspective view of a structure <NUM> in accordance with one example not part of the invention, shown in isolation. Structure <NUM> may be employed as a rotor blade and includes an elongate body that extends from a root <NUM> through a main section <NUM> to terminate at a wingtip <NUM>. Root <NUM> of structure <NUM> extends from nacelle <NUM> when attached thereto or integrated therewith, and wingtip <NUM> is the portion of the elongate body that is distal to nacelle <NUM>. The elongate body of structure <NUM> has a leading edge <NUM> and a trailing edge <NUM>, where leading edge <NUM> leads trailing edge <NUM> when, for example, structure <NUM> is in motion rotating with nacelle <NUM> about rotation axis R in the direction D. Like rotor blade <NUM>, the elongate body of structure <NUM> has a pressure side <NUM> and a suction side <NUM>.

In accordance with an aspect of the example, structure <NUM> also includes a rigid winglet <NUM> that is associated with the wingtip <NUM>. In this example, rigid winglet <NUM> is integral with the wingtip <NUM>. Rigid winglet <NUM> has a planar winglet body <NUM> substantially normal to and, in this example, extending from, suction side <NUM> of the elongate body to a termination point, or tip, <NUM> that is rearward of the trailing edge <NUM>. Planar winglet body <NUM> is aligned with the tangent of the circle traversed by the winglet <NUM> during movement in direction D about rotation axis R, thereby to present a thin edge to the air it moves through during rotation. As shown, termination point <NUM> is rearward of trailing edge <NUM> by a distance x. It is to be understood that the distance x as shown in the figures does not necessarily have to be the same across all embodiments.

Winglet <NUM> is configured to have a termination point <NUM> that is rearward of trailing edge <NUM> of rotor blade <NUM> in order to allow vortex shedding at this region to be gradual and less abrasive when compared to prior art designs. For example, instead of 'ripping' the air, the configuration shown in <FIG> better enables air encountered during rotation to run along winglet body <NUM> smoothly and with reduced resistance, thereby to reduce turbulence and noise emissions at the region of wingtip <NUM>.

<FIG> is a front perspective view of a structure 405A in accordance with an alternative example not part of the invention, shown in isolation. Like structure <NUM>, structure 405A includes an elongate body that extends from a root <NUM> through a main section <NUM> to terminate at a wingtip <NUM>. Root <NUM> of structure 405A extends from nacelle <NUM> when attached thereto or integrated therewith, and wingtip <NUM> is distal to nacelle <NUM>. The elongate body of structure 405A also has a leading edge <NUM> and a trailing edge <NUM>, where leading edge <NUM> leads trailing edge <NUM> when structure 405A is in motion such as for example when rotating with nacelle <NUM> about rotation axis R in the direction D. Like structure <NUM>, the elongate body of structure 405A has a pressure side <NUM> and a suction side <NUM>.

In accordance with an aspect of the example, structure 405A includes a rigid winglet 470A associated with the wingtip <NUM>. In this example, rigid winglet 470A is integral with the wingtip <NUM>. Rigid winglet 470A of structure 405A has a planar winglet body 472A substantially normal to and, in this example, extending from, pressure side <NUM> of the elongate body to a termination point, or tip, 474A that is rearward of trailing edge <NUM>. Planar winglet body 472A is aligned with the tangent of the circle traversed by the winglet 470A during movement in direction D about rotation axis R, thereby to present a thin edge to the air it moves through during rotation. As shown, termination point 474A is rearward of the trailing edge <NUM> by a distance x.

Like winglet <NUM>, winglet 470A is configured to have a termination point 474A that is rearward of trailing edge <NUM> of structure 405A in order to allow vortex shedding at this region to be gradual and less abrasive when compared to prior art designs. For example, instead of `ripping' the air, the configuration shown in <FIG> better enables air encountered during rotation to run along winglet body 472A smoothly and with reduced resistance, thereby to reduce turbulence, drag and noise emissions at the region of wingtip <NUM>.

Rigid winglets <NUM> and 470A represent very simple embodiments, for which numerous alternatives are contemplated.

For example, <FIG> is a front view of a wingtip region of a structure such as a rotor blade, as an observer might see it when standing facing the front of a horizontal wind turbine of which the rotor blade is a part - in accordance with another embodiment, in isolation. This structure is configured to be rotated clockwise in the direction D.

In this embodiment, the structure has a leading edge <NUM> slicing at high speed into wind Whs during rotation, a trailing edge <NUM>, and a wingtip <NUM>. A rigid winglet 470B is integral with wingtip <NUM> and extends smoothly from wingtip <NUM> by gently twisting so as to curve upwards while sweeping backwards with respect to the direction of rotation D so as to extend substantially normal to the suction side <NUM> (out of the page ie. , towards the observer). The rigid winglet 470B continues to twist a total of about <NUM> degrees (to reveal the pressure side <NUM>) and sweep backwards to a termination point, or tip, 474B, which is rearward of the trailing edge <NUM> by a distance x. The termination point 474B points away from the wind Whs. Winglet body 472B is substantially planar and is generally parallel to the tangent T of the circle traversed by the winglet 470B during movement of a turbine.

Without being bound by a particular theory, it is believed that the twisted configuration of the rigid winglet 470B contributes to the formation of laminar flow that reduces the intensity of vortex shedding and accordingly the noise due to vortex shedding.

<FIG> is a front view of a wingtip region of a structure suitable as a rotor blade in accordance with another embodiment, in isolation. In this embodiment, the structure has a leading edge <NUM> slicing at high speed into wind Whs during rotation, a trailing edge <NUM>, and a wingtip <NUM>. A rigid winglet 470C is integral with wingtip <NUM> and extends smoothly from wingtip <NUM> by gently twisting so as to curve upwards while sweeping backwards with respect to the direction of rotation D so as to extend substantially normal to the suction side <NUM> (out of the page ie. , towards the observer). The rigid winglet 470C continues to twist a total of about <NUM> degrees (to reveal the pressure side <NUM>) and sweep backwards to a termination point, or tip, 474C, which is rearward of the trailing edge <NUM> by a distance x. Termination point 474C is sharper than termination point 474B but, like termination point 474B, termination point 474C points away from the wind Whs Winglet body 472C is substantially planar and is generally parallel to the tangent T of the circle traversed by the wingtip during movement of a turbine.

<FIG> is a front view of a wingtip region of a structure suitable as a rotor blade in accordance with another embodiment, in isolation. In this embodiment, the structure has a leading edge <NUM> slicing at high speed into wind Whs during rotation, a trailing edge <NUM>, and a wingtip <NUM>. A rigid winglet 470D is integral with wingtip <NUM> and extends smoothly from wingtip <NUM> by gently twisting so as to curve upwards while sweeping backwards with respect to the direction of rotation D so as to extend substantially normal to the suction side <NUM> (out of the page ie. , towards the observer). The rigid winglet 470D continues to twist a total of about <NUM> degrees (to reveal the pressure side <NUM>) and sweep backwards to a termination point, or tip, 474D, which is rearward of the trailing edge <NUM> by a distance x. In this embodiment, winglet body 472D is slightly curved, or arced, and generally conforms to an arc of circumference of a circle traversed in the direction D by the winglet 470D during movement of a turbine.

<FIG> is a front view of a wingtip region of a structure suitable as a rotor blade in accordance with another example, in isolation. In this example, the structure has a leading edge <NUM> slicing at high speed into wind Whs during rotation, a trailing edge <NUM>, and a wingtip <NUM>. A rigid winglet 470E is integral with wingtip <NUM> and extends smoothly from wingtip <NUM> by gently twisting so as to curve upwards while sweeping backwards with respect to the direction of rotation D so as to extend substantially normal to the suction side <NUM> (out of the page ie. , towards the observer). The rigid winglet 470E continues to twist a total of about <NUM> degrees and sweep backwards to a termination point, or tip, 474E, which is rearward of the trailing edge <NUM> by a distance x. Winglet body 472E is substantially planar and is generally parallel to the tangent of the circle traversed by the winglet 470E during movement of a turbine.

<FIG> is a front view of a wingtip region of a structure suitable as a rotor blade in accordance with another embodiment, in isolation. In this embodiment, the structure has a leading edge <NUM> slicing at high speed into wind Whs during rotation, a trailing edge <NUM>, and a wingtip <NUM>. A rigid winglet 470F is integral with wingtip <NUM> and extends smoothly from wingtip <NUM> by gently twisting so as to curve downwards while sweeping backwards with respect to the direction of rotation D so as to extend substantially normal to the pressure side <NUM> (into the page ie. , away from the observer). The rigid winglet 470F continues to twist a total of about <NUM> degrees (to reveal the suction side <NUM>) and sweep backwards to a termination point, or tip, 474F, which is rearward of the trailing edge <NUM> by a distance x. In this embodiment, winglet body 472F is substantially planar and is generally parallel to the tangent of the circle traversed by the winglet 470F during movement of a turbine.

<FIG> is a side elevation view of a wingtip region of a structure suitable as a rotor blade in accordance with another embodiment, in isolation. In this embodiment, the structure has a leading edge <NUM> slicing at high speed into wind Whs during rotation, a trailing edge <NUM>, and a wingtip <NUM>. A rigid winglet <NUM> is integral with wingtip <NUM> and extends from a linear connection mechanism <NUM> through a planar transition region <NUM> from wingtip <NUM> before gently twisting so as to curve upwards while sweeping backwards with respect to the direction of rotation D so as to extend substantially normal to the suction side <NUM> (out of the page ie. , towards the observer). In this embodiment, the connection mechanism is a rigid joint retaining the rigid winglet <NUM> in a fixed position with respect to the wingtip <NUM>.

The rigid winglet <NUM> continues to twist a total of about <NUM> degrees (to reveal the pressure side <NUM>) and sweep backwards to a termination point, or tip, <NUM>, which is rearward of the trailing edge <NUM>. Winglet body <NUM> is substantially planar and is generally parallel to the tangent of the circle traversed by the winglet <NUM> during movement of a turbine.

In this embodiment, planar transition region <NUM> is angled upwards by an angle Θ from connection mechanism <NUM> with respect to suction side <NUM>, and therefore extends more abruptly with respect to wingtip <NUM> than in other embodiments.

<FIG> is a side elevation view of a wingtip region of a structure suitable as a rotor blade in accordance with another embodiment, in isolation. In this embodiment, the structure has a leading edge <NUM> slicing at high speed into wind Whs during rotation, a trailing edge <NUM>, and a wingtip <NUM>. A rigid winglet <NUM> is integral with wingtip <NUM> and extends from a linear connection mechanism <NUM> through a planar transition region <NUM> from wingtip <NUM> before gently twisting so as to curve upwards while sweeping backwards with respect to the direction of rotation D so as to extend substantially normal to the suction side <NUM> (out of the page ie. , towards the observer). In this embodiment, the connection mechanism is a hinge permitting the rigid winglet <NUM> to rotate freely with respect to the wingtip <NUM> in response to fluid flow incident on the elongate body.

Figure 9C is a side elevation view of a wingtip region of a structure suitable as a rotor blade in accordance with another embodiment, in isolation. In this embodiment, the structure has a leading edge <NUM> slicing at high speed into wind Whs during rotation, a trailing edge <NUM>, and a wingtip <NUM>. A rigid winglet 470I is integral with wingtip <NUM> and extends from a linear connection mechanism 476I through a planar transition region 478I from wingtip <NUM> before gently twisting so as to curve upwards while sweeping backwards with respect to the direction of rotation D so as to extend substantially normal to the suction side <NUM> (out of the page ie. , towards the observer). In this embodiment, the connection mechanism 476I is a control structure permitting the rigid winglet to 470I rotate with respect to the wingtip in response to control signals. The control structure includes a hydraulic/pneumatic pump structure connected to wingtip <NUM> and that can be operated to either extend or retract an arm with a distal end that is connected to planar transition region 478I. Extension of the arm using the pump structure causes the arm to push planar transition region 478I clockwise, and retraction of the arm using the pump structure causes the arm to pull planar transition region 478I counterclockwise.

The rigid winglet 470I continues to twist a total of about <NUM> degrees (to reveal the pressure side <NUM>) and sweep backwards to a termination point, or tip, 474I, which is rearward of the trailing edge <NUM>. Winglet body 472I is substantially planar and is generally parallel to the tangent of the circle traversed by the winglet 470I during movement of a turbine.

<FIG> is a front view of a wingtip region of a structure suitable as a rotor blade in accordance with another example, in isolation, and <FIG> is a front perspective view of the wingtip region of <FIG>.

In this example, the structure has a leading edge <NUM> slicing at high speed into wind Whs during rotation, a trailing edge <NUM>, and a wingtip <NUM>. A rigid winglet 470J is attachable to wingtip <NUM> using rigid connection mechanism 476J at connection points 473J using suitable fasteners passed through both the rigid winglet 470J and the wingtip <NUM>. In this example, rigid connection mechanism 476J is a rigid bar incorporating connection points 473J which are, in this example, holes through the rigid bar. In this example, connection mechanism 476J is formed of metal and is integral with a planar extension region 479J through which rigid winglet 470J extends. Planar extension region 479J is intermediate the connection mechanism 476J and a transition region 478J. In this example, transition region 478J is curved between extension region 479J and winglet body 472J so as to smoothly transition to winglet body 472J from wingtip <NUM>. In this example, winglet body 472J is not twisted but is swept backwards with respect to the direction of rotation D so as to extend substantially normal to the suction side <NUM> (out of the page ie. , towards the observer). The rigid winglet 470J continues to sweep backwards to a termination point, or tip, 474J, which is rearward of the trailing edge <NUM> by a distance x. In this example, winglet body 472J is substantially planar and is generally parallel to the tangent of the circle traversed by the winglet 470J during movement of a turbine.

In <FIG>, it can be seen that the connection mechanism 476J is stepped in the region of the distal end of wingtip <NUM> thereby to ensure transition region 479J is primarily in the same plane as wingtip <NUM>.

The configurations of winglets disclosed herein have been provided to decrease noise emissions and to improve the operational efficiency of horizontal wind turbines through reduction of vortex tip shedding and associated sound waves.

Tests were conducted of a small scale wind turbine with structures for traversing a fluid-environment as described herein, from various distances from a source of incident wind and various power levels, for each of: prior art structures with no winglet, prior art structures with winglet, structures according to the present invention with a rigid winglet associated with a wingtip having a winglet body extending substantially normal to one of a suction side and a pressure side of the elongate body to a termination point that is rearward of the trailing edge. The test results demonstrated a subtle increase in power output at various wind speeds and distances from the wind source with a standard winglet and even higher power output differences resulting from structures according to the present invention.

The above-described rotor blade configurations improvements to the winglet of a rotor blade for a horizontal-axis wind turbine can also be applied to one or more rotor blades usable for vertical-axis wind turbines, and both of any scale, or to one or more rotor blades usable in hydroelectric dam turbines, gas turbines, tidal turbines or airborne wind energy turbines or in other kinds of turbines dealing with fluid flow whether of gas or of liquid.

The above-described rotor blade configurations may alternatively be employed in aircraft such as commercial airliners, military jet aircraft, helicopter blades, helicopter wings, civilian airplanes, drones, and other similar aircraft. The invention or inventions described herein may be applied to wind turbines having fewer or more blades than described by way of example in order to increase the operational efficiency of a wind turbine, to decrease maintenance costs, and to increase the scalability and marketability of such wind turbines.

It is observed that commercial airliners, civilian airplanes, drones, helicopter wings would have a winglet of similar size ratio to those of modern commercial airliners, with an architecture that bends back beyond the line of the trailing edge.

However, military jet aircraft, helicopter blades, would likely employ a similar winglet that is in size in comparison to blade length due to the wingtip speed that would be incurred. For scale reference, a helicopter rotor is roughly <NUM>/<NUM> the size of a commercial airliner, with similar tip speed, the size would be <NUM>/<NUM> that of an airliner's winglet.

Although embodiments have been described with reference to the drawings, those of skill in the art will appreciate that variations and modifications may be made without departing from the scope thereof as defined by the appended claims.

For example, a rigid winglet as described herein may be further equipped to integrate into the lightning protection system of a rotor blade and may contain miniature projections that reduce impact forces of rain and snow, thus limiting erosion and blade failure.

Furthermore, a winglet may be provided with a surface treatment such as a series of dimples and/or a series of hexagonal patterns and/or a series of troughs or grooves, all of which may either be sunk into the surface or raised above the surface of the winglet. For example, <FIG> is a front view of a wingtip region of a structure in isolation, with a hexagonal-patterned surface treatment <NUM> applied to the suction side <NUM>. <FIG> shows an enlarged portion of the hexagonal-patterned surface <NUM> in isolation. As shown, each hexagon H is wedge-shaped in cross-section, with the thin edge of the wedge <NUM> facing towards the source of incident wind Wi thereby to form somewhat of a ramp upwards from suction side <NUM>, and the thick end of the wedge <NUM> facing away from the source of incident wind Wi thereby to be spaced from suction side <NUM>.

Such improvements may apply equally well, mutatis mutandis, with such mutations as being relevant, including but not limited to, commercial airliners, military jet aircraft, helicopter blades, helicopter wings, civilian airplanes, spacecraft, drones, and other things.

Furthermore, the structures disclosed herein are usable in other fluid environments besides ambient air, such as water environments, oil environments and so forth.

The structure adapted to traverse a fluid environment may be applied to a vertical-axis wind turbine. In such an embodiment, the rigid winglet departs from the lower and upper region of the blade, as shown generally in <FIG>. This winglet can spiral any of: in toward the central shaft of the wind turbine, or flare out and away from the shaft. In this application, these novel winglets may also flare directly back from the direction of rotation.

The structure adapted to traverse a fluid environment may be applied to a hydroelectric dam turbine. In such an embodiment, the winglet departs from the tip at the trailing edge, as these blades are generally quite wide in comparison to their length. The curl as described in the art of this patent would begin generally at the leading edge tip, and slowly increase in severeness of curl as it moves towards the trailing edge, terminating beyond it, where the curl is not more than <NUM> degrees.

The structure adapted to traverse a fluid environment may be applied to a gas turbines. In such an embodiment, the curl as described in the art of this patent begins generally at the leading edge tip, and slowly increases in severeness of curl as it moves towards the trailing edge, terminating beyond it. The termination however, in this case, would occur at an angle more towards the suction side, such to be in line with the flow of gas, and to induce a less turbulent flow onto the next set of blades.

The structure adapted to traverse a fluid environment may be applied to a tidal turbines. In such an embodiment, the winglet departs the tip in the same manner as the wind turbine, as described. This is most certainly true for tidal turbines that use a apparatus the is highly analogous to wind turbines. In cases where the tidal turbine is incased in a shell, with a multiple of fins extending from the outer circumference of the shell towards an inner portion of a shell, the winglets resemble those of the hydroelectric turbines, except that the winglets would be in the central region of the shell, and not at an outer circumference.

The structure adapted to traverse a fluid environment may be applied to an airborne airborne wind energy turbine. In such an embodiment, the winglets may be applied to both the wing of the kite itself, and to the power generating device, which is most often a propeller. In the case of the wing, that enables the kite to fly, the winglet would resemble those as applied to an aircraft, which have a similar shape to those of the wind turbine as described. In the case of the power generating device, which is most often a propeller, the winglet is similar to the hydroelectric dam turbines.

The structure adapted to traverse a fluid environment may be applied to a commercial airliner, with the winglet having a similar shape to those of the wind turbine described above.

The structure adapted to traverse a fluid environment may be applied to a military jet aircraft and to a spacecraft, with the winglets would be smaller then those seen on a commercial airline.

The structure adapted to traverse a fluid environment may be applied to a helicopter blade, wherein the winglet would curl down towards the ground and terminate rearwards the trailing edge.

The structure adapted to traverse a fluid environment may be applied to helicopter wings, where the winglet would curl up towards the sky and terminate rearwards the trailing edge.

The structure adapted to traverse a fluid environment may be applied to wings of civilian airplanes, where the winglet contains a similar shape to those of the wind turbine as described.

The structure adapted to traverse a fluid environment may be applied to wings of a drone, with the winglet contains a similar shape to those of the wind turbine as described.

It is observed that commercial airliners, civilian airplanes, drones, helicopter wings and helicopter blades would have a winglet of similar size ratio to those of modern commercial airliners, with an architecture that bends back beyond the line of the trailing edge. For scale reference, a helicopter rotor is roughly <NUM>/<NUM> the size of a commercial airliner, with similar tip speed, the size would be <NUM>/<NUM> that of an airliner's winglet.

However, military jet aircraft would likely employ a smaller winglet size as compared to those commercial aviation due to the wingtip speed that would be incurred. For scale reference, a military jet aircraft wing is roughly <NUM>/<NUM> the size of a commercial airliner, with much higher tip speed, the size would be less than <NUM>/<NUM> that of an airliner's winglet.

Claim 1:
A structure (<NUM>) adapted to traverse a fluid environment, the structure (<NUM>) comprising: an elongate body having a root, a wingtip, a leading edge and a trailing edge (<NUM>); and a rigid winglet (<NUM>) associated with the wingtip and having a winglet body (<NUM>) extending substantially normal to one of a suction side and a pressure side of the elongate body to a termination point (<NUM>) that is rearward of the trailing edge (<NUM>);
wherein the winglet body (<NUM>) is arced and conforms to an arc of circumference of a circle traversed by the rigid winglet (<NUM>) during movement of the elongate body about a rotational axis of a nacelle; and
wherein the winglet body is integral with the wingtip and extends from the wingtip by twisting such that the winglet curves upwards while sweeping backwards with respect to a direction of rotation of the elongate body so as to extend substantially normal to the suction side or curves downwards while sweeping backwards with respect to a direction of rotation of the elongate body so as to extend substantially normal to the pressure side;
characterized in that the twist of the winglet is <NUM> degrees.