CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. Provisional Patent Application No. 61/188,476 filed August 11, 2008, which is incorporated herein by reference in its entirety for all purposes.

FIELD OF THE INVENTION

The present invention relates generally to the production of mechanical work from wind power. More particularly, the present invention relates to generation of electricity though the use wind power captured using an extendable and retractable kite having a variable air surface.

BACKGROUND OF THE INVENTION It is well known to generate mechanical work from wind power, such as rotating a shaft with a windmill to operate a generator to produce electricity, and alternate wind power systems have been patented.

US 4,124,182 (Loeb) teaches a method and apparatus using parakites or modified parachutes, for capturing wind energy and for converting the consequent wind-induced linear motion to shaft rotation. The parakite apparatus includes a plurality of trains of parakites, with each train comprising a power line having a plurality of serially coupled parakites secured thereto. Each train is secured at its earthbound end to a drum or windlass selectively rotatable in both clockwise and counter-clockwise directions to either reel in the power lines attached thereto, or to enable the power lines to be pulled upwardly and outwardly by the action of the winds on the parakites. Provision is made, including canopy lines, to selectively collapse the parakites on selected power lines to facilitate the reeling- in procedure. Gearing is provided to translate the rotational movement of each drum to a power takeoff shaft as the drum is rotated by the outward motion of the power line. The resulting shaft output is utilized to provide energy as, for example, by the operation of standard electrical generators, or air compressors. US 6,254,034 (Carpenter) teaches a tethered aircraft system in which the tethered aircraft is blown by wind to travel downwind at a controlled rate for maximal mechanical energy gathering from wind whose velocity fluctuates and gusts. A cycle of travel is completed when the aircraft is travelled upwind to the site of the beginning of downwind travel where downwind travel is recommenced. The downwind travelling aircraft pullingly unwinds its tether from an anchored windlass drum to spin the rotor of an interconnected electrical machine to convert the mechanical energy to electricity.

US 7,504,741 (Wrage et al.) teaches a device for converting wind flow energy into mechanical energy, comprising a wind-engaging member having an aerodynamic profile which generates an uplift force in the direction of a load cable when the airflow direction is perpendicular to the load cable, a steering mechanism configured to produce a steered movement about a first axis or in a first direction of the wind-engaging member and about a second axis or in a second direction that is different from the first direction or axis of the wind-engaging member, relative to the airflow direction, and a control unit configured to use the steering mechanism to move the wind-engaging member along a predetermined flight path in a flight plane perpendicular to the load cable. The present invention further provides a method for converting wind flow energy into mechanical energy and a docking station for use with the device.

It is, therefore, desirable to provide a wind power system which avoids some of the disadvantages of other wind power systems.

SUMMARY OF THE INVENTION

This variable air surface (VAS) wind power generating system (Figure 1) uses a retractable and extendable wind impingement surface to generate electrical power from wind. It is designed to utilize the low-wind speed conditions around the world that are not considered typical wind power generating conditions as well as generating power in extreme weather conditions be they extreme cold, extreme heat, rain, snow, sleet, or desert winds.

Unlike other wind electrical power generating devices that harness wind energy through rotating mechanisms placed in the wind, the VAS uses the principle that, even in low wind conditions, wind can exert a considerable force upon a surface that, when utilized as an input to a transmission designed to accept power at high torque and low rpm, can transfer the available power (high torque x low rpm = power) into a electrical generator at low torque and high rpm typical of available generators on the market.

The VAS may include redundant surface control cables and a fail-safe inflatable helium balloon release canister mechanism that will keep the VAS aloft in case of an unforeseen catastrophic failure. Inherent to the design is wind and weather monitoring to protect the VAS from severe weather. In extreme conditions, the VAS digital control system may retract the VAS and secure itself to a central protective mast until it is safe to generate power under better weather conditions. Extreme conditions may include high wind, sand storm, ice storm, or any condition where the system would be operated outside its design envelope (such as component stress, vibration, public or equipment safety) etc.

It is expected that this invention will have uses in disaster relief, remote climate areas including islands and, in general, where average low wind conditions prohibit the use of traditional wind generating equipment. The VAS may be grid-tied electrically into a main supply grid whereby the electrical output will match both frequency and voltage electronically. It can also be used as either a stand-alone AC or DC electrical generating system for emergency or fixed electrical needs. For instance the VAS could be utilized on a farm to power specific circuits independent of the existing electrical grid. There are a number of unique features to this invention namely:

The invention may utilize a variable air surface (VAS) that extends and retracts in order to generate relatively constant electrical power output under varying wind conditions.

The invention may provide an electrical wind power generating system that is designed to generate its rated electrical generating capacity (capacity factor) under the average wind conditions inherent to a geographical area.

The invention may provide an easily accessible and robust electrical wind power generating system that can be installed and used at a fraction of the cost of current wind generating technologies on the market. The invention may provide a stand-alone, electrical wind power generating system that can be easily shipped, assembled and used anywhere in the world so as to utilize wind energy that cannot be cost-effectively captured with current wind generating technologies on the market.

The invention may provide a stand-alone electrical wind power generating system that can be easily shipped, assembled and used anywhere in the world for disaster relief. The invention may provide an electronic control system that controls the VAS, its attack angle into the wind, the angle of the main mast and the extension and contraction of the VAS, power generators, control motor, and built-in safety features.

The invention may reduce the maintenance costs associated with electrical wind power generating systems. The invention may provide an electrical wind power generating system that can be used world- wide regardless of average wind speed conditions, temperature variations, or extreme weather conditions.

It is an object of the present invention to obviate or mitigate at least one disadvantage of previous systems for generating electricity from wind power. In a first aspect, the present invention provides a system for generating electricity from wind power having a kite member, having a variable air surface, a plurality of control cables extending between the kite member and a ground station, the ground station having a main mast, the main mast pivotable between a retracted position and an extended position, conversion means for converting the motion of the main mast between the retracted position and the extended position into electricity as the kite member is extended from the ground station, kite retraction means for retracting the kite when the kite reaches a selected distance from the ground station, main mast retraction means for retracting the main mast from the extended position to the retracted position, and a control system for selectively controlling the system. In another aspect, the present invention provides a system for generating electricity from wind power having a kite member, having a variable air surface, a plurality of control cables extending between the kite member and a ground station, the plurality of control cables independently extendible between a retracted position and an extended position, the ground station having a main mast, the main mast pivotable between a retracted position and an extended position upon extension of a mast retract cable, an electrical generator operable by movement of the main mast from the retracted position to the extended position, a powered kite retraction system for retracting the control cables from the extended position to the retracted position, a powered main mast retraction means for retracting the main mast from the extended position to the retracted position, and a control system for providing control signals to the kite member, the variable air surface, and the kite retraction system.

In one embodiment the kite retraction system is adapted to be powered by energy stored from the electrical generator.

In one embodiment the kite member having a framed kite, having v-shaped guides for the variable air surface. In one embodiment the kite member having a substantially planar variable air surface.

In one embodiment the kite further having a stabilizer having a spar extending downward from the kite and a weight at a distal portion of the spar.

In one embodiment the kite having an emergency lift system having a compressed lighter than air gas such as helium within a pressurized container, which may be selectively released into an inflatable balloon attached to the kite to provide additional lift.

In one embodiment, the compressed gas selectively released by the control system upon an emergency event.

In one embodiment, the main mast having mast stands, to provide lateral separation between the control cables.

In one embodiment, the control system having a PID controller receiving a pressure from a pressure transducer to control the area and angle of attack of the kite.

In one embodiment, the ground station having a plurality of indexed control cable reels, independently operable by a solenoid operated indexer. In one embodiment, the ground station having a mast shaft, operable by the main mast by an indexed mast clutch bearing.

In one embodiment, the ground station having an indexed mast cable retract reel, independently operable by a solenoid operated indexer.

In a further aspect, the present invention provides a method for generating electrical energy from wind power by providing a kite member having a variable air surface, the area of the air surface variable between a lesser area and a greater area, setting the VAS to the greater area, reeling out the kite member from a main mast using wind power to generate mechanical energy, which is used to generate electrical energy, setting the VAS to the lesser area when the kite member reaches a selected distance, and retracting the kite member. In one embodiment, the method includes storing a portion of the mechanical energy or electrical energy as stored energy.

In one embodiment, the method includes using the stored energy for retracting the kite member.

In one embodiment, the mechanical energy is generated by the conversion of the high torque, low RPM drag force on the main mast into a higher RPM, lower torque.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein:

Fig. 1 is a system of the present invention; Figs. 2A-B are views of a system of the present invention; Fig. 3 is a view of a kite of the system of Fig. 1 ;

Fig. 4 is a view of a ground station of the system of Fig. 1; Fig. 5 is an enlarged view of a portion of the ground station of Fig. 4; Fig. 6 is a view of a cover for the ground station of Fig. 4; Fig. 7 is a partial detail view of the kite of the present invention; Fig. 8 is an enlarged partial detail view of the kite of Fig. 7;

Figs. 9A-C are views of the kite of the present invention with the VAS in varying states of extension and retraction;

Fig. 10 is a view of a kite of the present invention with an emergency lift system deployed; and Figs. 1 IA-E are views of the system of the present invention through a cycle. DETAILED DESCRIPTION

Generally, the present invention provides a method and system for generating electricity from wind power. Referring to Fig. 1 a system 10 for generating electricity from wind power of the present invention includes a kite 20, having a variable air surface 30 remotely operable from a ground station 40 through a plurality of control cables 50-U/50-L to a main mast 60.

Referring to Figs. 2A-B the ground station 40 includes a lower, ground mounted platform 70 and a freely rotatable upper platform 80 (see Fig. 4) which allows the system 10 of the present invention to self orient to the prevailing wind direction.

Referring to Fig. 3, a plurality of control cables 50-U/50-L extend between the kite 20 and the ground station 40 (see also Fig. 4). The control cables 50-U/50-L may be designed to include redundancy, for example each control cable may include a plurality of cables to provide redundancy. The control cables 50-U/50-L may include a tensile cable to support the tension between the kite 20 and the ground station 40. The control cables 50- U/50-L may include a signal cable to provide for power or signal communications, or both, between the kite 20 and the ground station 40, for example for pressure transducers, control cable tension monitors, emergency lift system, etc. onboard the kite 20. The ground station 40 uses a main mast 60 to provide a desired base elevation for operation of the kite 20. Elongate mast stands 90 provide for full contraction of the VAS 30 and improved control of the kite 20. The main mast 60 may be designed to be somewhat flexible to absorb or dampen some wind fluctuations. For example, the main mast may be built from a composite fiber. A wind pressure or speed sensor, such as an anemometer 100, may be included on the main mast 60 and that information fed to the control system.

In Fig. 3, the kite 20 uses two control cables 50-U/50-L, where the control cable 50-U is the upper cable which extends from the ground station 40 to an upper portion of the kite 20 and back to the ground station 40. The control cable 50-L is the lower cable which extends from the ground station 40 to a lower portion of the kite 20 and back to the ground station 40. The control cables 5O-U/5O-L may be operated independently or cooperatively to fly or control the kite 20, or both, as desired (see below Figs. 4-5). The VAS 30 of the kite 20 may also be varied through the selective operation of the control cables 50-U/50-L (see below Figs. 7-9).

A stabilizer 110 having a spar 120 with a weight 130 at the end extends downward from the kite 20 to provide additional stability.

Referring to Figs. 4-5, the main mast 60 is pivotally mounted on an indexed mast clutch bearing 140. The mast clutch bearing 140 allows the selective pivoting of the main mast 60. In the embodiment shown, the range of motion 150 of the main mast 60 is between about 15 degrees upwind (retracted) and about 15 degrees downwind (extended), but one skilled it the art recognizes that those angles could be increased or decreased.

The main mast 60 selectively drives a mast shaft 160 through the indexed mast clutch bearing 140. A transmission #1 170 converts the high torque, low rpm motion of the mast shaft 160 into higher rpm motion for a power take off (PTO) shaft 180 connected in this case to an electrical generator #1 190. The electrical generator #1 190 may be an AC generator or DC generator.

A flywheel 200 may be utilized to help stabilize the rotation of the PTO shaft 180 by storing and dissipating rotational inertia throughout the cycle.

The ends of the control cables 50-U/50-L are routed down the main mast 60 onto indexed control cable reels 210-1/210-2/210-3/210-4 on a control shaft 220. Each control cable reel 210-1/210-2/210-3/210-4 is selectively operable independently from the others.

Each control cable reel 210-1/210-2/210-3/210-4 has its own solenoid actuated indexer having indexing pins 240-1/240-2/240-3/240-4 that engage the indexing discs 250-1/250-2/250-3/250-4 respectively. To control pitch and yaw one can simply engage the indexing pins (either 1 through 4) individually which holds the respective control line indexed at a fixed length while the other three extend. This can be done either individually or in combination of two or three to control angle of attack and maintain a relatively constant power output.

Pressure transducers or other measurement means may be incorporated into the indexing discs 250-1/250-2/250-3/250-4 to provide control information, for example the tension on the end of each control cable 50-U/50-L, to the electronic control system. A mast retract cable 240 extends between the main mast 60 onto a mast cable reel 270 on the control shaft 220. The mast cable reel 270 is selectively operable independently from the control cable reels 210-1/210-2/210-3/210-4. The mast cable reel 270 uses a similar indexing system as the control cable reels 210-1/210-2/210-3/210-4. A control motor 280 is selectively operable to drive the control shaft 220 and the control cable reels/mast cable reel and provides control and retraction. The control shaft is 220 operably connected with the PTO shaft 180 through transmission #2 290 and a drive belt 300. Transmission #2 290 converts the high torque, low rpm motion of the control shaft 220 into higher rpm motion for the PTO shaft 180. The control motor 280 may be driven by electrical generator #1 190 or an external power source such as an electrical grid, fossil fuel powered generator, or storage system such as a capacitor or batteries.

A control system 230 may be used to control the operation of the system 10, condition the power generated, and control the power distribution. The control system 230 may include a PID (proportional, integral, differential) response based on pressure transducers to provide a relatively constant power production from the wind energy. The area of the VAS 30 as well as the angle of attack may be controlled to maximize available wind energy.

As referred to above (see above Figs. 2A-B), the ground station 40 includes a lower, ground mounted platform 70 and a freely rotatable upper platform 80 which allows the system 10 of the present invention to self orient to the prevailing wind direction.

Referring to Fig. 6, a cover 320 is provided in sections which may be connected to enclose the mechanical works and includes a main mast opening 330 for the main mast 60 (see Fig. 4) and a mast retract cable opening 340 for the mast retract cable 260 (see Fig. 4). The main mast opening 330 and the mast retract cable opening 340 are elongate to provide for the range of motion of the main mast 60 and the mast retract cable 260 respectively. Weather seals 350 provide protection from the weather but allow the range of motions mentioned above. The control cables 50-U/50-L may also be sealed with cable seals 360 (see Fig. 4).

Referring to Figs. 7-9, the kite 20 includes a (variable air surface) VAS 30, variable between maximum area (see Fig. 9A) and a minimum area (see Fig. 9C), and in- between (see Fig. 9B) along guides 370. The kite 20 includes cable bearings 380, main VAS support bearings 390 and rotating central mast 400, around which the control cable is routed.

To selectively furl and unfurl the VAS 30, the control cables 50-U/50-L are selectively controlled. The upper control cable 50-U is continuous and is attached to control cable reels 210-1 and 210-2 (indexing discs 240-1 and 240-2) and the lower control cable 50-L is continuous and attached control cable reels 210-3 and 210-4 (indexing discs 240-3 and 240-4). To unfurl the VAS 30, control cable reels 210-1 and 210-3 are indexed which holds those two endpoints fixed and lets both the lower control cable 50-L and upper control cable 50-U to slowly release and unfurl the VAS 30 on the kite 20. When power output is within a selected range, for example within about 5-10% of rated output, all four index pins (250-1/250-2/250-3/250-4) may be released and all four control lines continue out (e.g. both ends of the upper control cable 50-U and both ends of the lower control cable 50-L). To furl the VAS, control cable reels 210-2 and 210-4 are engaged and the control motor 280 is operated to draw the two lines back. Note that all of these indexing wheels have clutch bearings which freewheel in one direction and allow power/control in the opposite direction.

Referring to Fig. 8, the material of the VAS 30 (which may be Kevlar (trade-mark) or other suitable material known to one skilled in the art) may be attached to the control cables 50-U/50-L by a stainless steel wire sewn into the seam of the VAS 30 which includes a loop extending outward at the corners of each seam. The loop is attached to the respective control cable 50-U/50-L at a fixed point using a spring loaded snap similar to a carabiner or otherwise attached using connectors known to one skilled in the art. The control cables 5O-U/5O-L are preferably a high strength polymer. A similar loop is fixed in the respective control cable 50-U/50-L and the snap allows for easy fabric removal. A similar attachment mechanism is used to attach the VAS 30 to the rotating central mast 400 of the kite 20.

Referring to Fig. 10, an emergency lift system 410 includes a pressurized container 420 holding a compressed lighter than air gas such as helium. Upon an emergency event, the gas may be released into an inflatable balloon 430 attached to the kite to provide additional lift. Alternatively, the lighter than air gas may be supplied by to the inflatable balloon 430 by providing an electric charge to a reactive chemical (as in an automobile air bag) to produce the gas.

Referring to Fig. 11, the complete cycle of the VAS wind power electrical generating system is shown. , Referring to Fig. 1 IA (and 1 IE), the VAS 30 is set to an extended position to create a substantial drag force on the control cables 50-U/50-L and is allowed to slowly travel downwind from the ground station 40. In doing so, the control cables 50-U/50-L convert that drag force into rotary motion of the mast shaft 160 (via indexed mast clutch bearing 140) as the main mast 60 is slowly pivoted downwind which generates electricity (see Fig. 4).

Referring to Fig. 1 IB-C, the kite 20 is allowed to extend in a controlled manner while generating electricity from the rotation of the mast shaft 160 (and the resulting motion of the PTO shaft 180). As the kite 20 travels downwind, control of the flight parameters, including pitch, yaw, angle of attack and area of the VAS 30 may be controlled from the ground station 40 through the control cables 50-U/50-L by the selective operation of the control cable reels 210-1/210-2/210-3/210-4 with the control system 230.

When the kite 20 reaches a selected distance (or other preselected or real-time parameter), the VAS 30 is retracted to a minimum position (furled) through the control cables 50-U/50-L by the selective operation of the control cable reels 210-1/210-2/210- 3/210-4 (as described in detail above), and both the main mast 60 and control cables 50- U/50-L retract. A typical selected distance might be in the order of 100' (30m) and the typical time to reach that extension might be in the order of 10 minutes.

The mast power system and the cable power system retract sequentially so that one system powers the other as they retract. The typical time for that retraction might be in the order of 15 seconds.

If there is not sufficient energy stored in the system 10 (for example as rotational inertia of the flywheel, or as electricity in a capacitor for powering the control motor 280) an intermediate partial cycle may be operated (repeatedly as necessary) as the control cables 50-U/50-L and the mast retract cable 260 are retracted. The partial cycle may include pausing the retraction of the control cables 50-U/50-L and mast retract cable 260, expanding the VAS 30 to maximum, and capturing wind energy to add power to the system 10, e.g. from the mast shaft 160 or the control shaft 220, or both.

Referring to Figs. 9D-E, upon complete retraction, the VAS 30 surface is extended (unfurled) and the cycle is repeated. If the system is fully stopped (i.e. neither the PTO shaft 180 nor the control shaft are rotating, or are not rotating at a sufficient speed), the mechanical works may be started by rotating the control shaft 220 by operation of the control motor 280 (if power for the control motor 280 is available) or by otherwise rotating the control shaft 220, for example by turning a crank manually. Throughout the cycle, the entire unit freely rotates on the rotatable upper platform

80 about the ground mounted platform 70 in order to change direction freely with varying wind directions.

In the preceding description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the embodiments of the invention. However, it will be apparent to one skilled in the art that these specific details are not required in order to practice the invention. In other instances, well-known electrical structures and circuits are shown in block diagram form in order not to obscure the invention. For example, specific details are not provided as to whether the embodiments of the invention described herein are implemented as a software routine, hardware circuit, firmware, or a combination thereof.

Embodiments of the invention can be represented as a software product stored in a machine-readable medium (also referred to as a computer-readable medium, a processor- readable medium, or a computer usable medium having a computer-readable program code embodied therein). The machine -readable medium can be any suitable tangible medium, including magnetic, optical, or electrical storage medium including a diskette, compact disk read only memory (CD-ROM), memory device (volatile or non- volatile), or similar storage mechanism. The machine-readable medium can contain various sets of instructions, code sequences, configuration information, or other data, which, when executed, cause a processor to perform steps in a method according to an embodiment of the invention. Those of ordinary skill in the art will appreciate that other instructions and operations necessary to implement the described invention can also be stored on the machine-readable medium. Software running from the machine-readable medium can interface with circuitry to perform the described tasks.

The above-described embodiments of the invention are intended to be examples only. Alterations, modifications and variations can be effected to the particular embodiments by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.