TECHNICAL FIELD
The present invention relates to power generation and more particularly to systems that convert wind energy acting on aerial wind driven elements to rotary or electrical power.
BACKGROUND ART
As fossil fuels become depleted and more expensive, the need for cost competitive methods and apparatus for harnessing renewable energy sources increases. The wind was long used for powering sailing ships and windmills, but the advent of steam engines or turbines, internal combustion engines, and gas turbines provided cheaper, more convenient energy sources. Less expensive and more efficient apparatus and methods for utilizing wind power would now be beneficial.
Windmills (or wind turbines) are currently being used to generate electricity and to drive pumps, however the cost to generate electricity with a windmill is still more expensive than the cost of electricity generated from fossil fuels. Windmills have a high capital cost relative to power generated. Wind speed, in general, is higher and more consistent with increasing altitude. There is potential to generate significant power with airborne or aerial apparatus at altitudes above the heights reasonably reachable by ground based windmills.
The challenge with wind power generation is to convert the linear power of the wind to rotary motion to drive an electrical generator or a pump. One known approach to aerial wind power generation is a tethered, aerial windmill. Such aerial windmills can be supported by lighter than air aircraft, such as a blimp, or by lift from airfoil wing structures. These aerial windmills are relatively heavy and require long, heavy electrical cables to transmit the generated power to ground level.
A second known approach to aerial wind power generation is a wind powered element, such as a kite, blimp or airfoil, that is connected to a tow line. The tow line wraps around a reel on the shaft of a ground level power generation device. As the wind powered element is pulled by the wind, the distance from the wind powered element to the shaft increases and the tow line rotates the reel and shaft to generate power. The angle of attack or the shape of the wind powered element is changeable so that the wind powered element can be reeled back towards the ground level power generation device with little power use.
A third known approach to aerial wind power generation is an endless chain of spaced kites linked to the shaft of a ground level power generation device. The kites follow an ascending path and a descending path. The kites are adjustable to provide higher lift while on the ascending path.
DISCLOSURE OF THE INVENTION
An aerial power generation system includes a guide line that extends skywards at a selected angle. The guide line is connected at the upper end to a support body. A wind powered driven element is slidably mounted on the guide line. The driven element is connected by a tow line to a reel on a shaft of a means for generating power. Means are provided for changing the driven element from high force configurations to low force configurations. Another aerial power generation system includes a plurality of wind powered driven elements connected by tow lines to spaced attachment points on a revolving apparatus that drives a means for generating power. A means for changing the driven elements between high force configurations and low force configurations changes each driven element to high force configurations when the respective attachment point is moving downwind and to low force configurations when the respective attachment point is moving upwind to cause rotation of the revolving apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
Details of this invention are described in connection with the accompanying drawings that bear similar reference numerals in which:
FIG. 1 is a perspective view of a aerial wind power generation system embodying features of the present invention.
FIG. 2 is a front elevation view of a driven element of the system of FIG. 1.
FIG. 3 is a side elevation view of a driven element of the system of FIG. 1, in a high force configuration.
FIG. 4 is a side elevation view of a driven element of the system of FIG. 1, in a low force configuration.
FIG. 5 is a side elevation view of a driven element of the system of FIG. 1, with an alternative control line arrangement.
FIG. 6 is a top plan view of a means for generating power of the system of FIG. 1.
FIG. 7 is a sectional view taken along line 7-7 of FIG. 6.
FIG. 8 is a perspective view of another aerial wind power generation system embodying features of the present invention, with two guide lines.
FIG. 9 is a perspective view of a support body of FIG. 8.
FIG. 10 is a perspective view of another support body for the system of FIG. 8.
FIG. 11 is a side elevation view of another support body for the system of FIG. 8.
FIG. 12 is a perspective view of a driven element for the system of FIG. 8.
FIG. 13 is a top schematic view of another aerial wind power generation system embodying features of the present invention.
FIG. 14 is a top plan view of a revolving apparatus of the system of FIG. 13.
FIG. 15 is a partial side elevation view of the revolving apparatus of the system of FIG. 14.
FIG. 16 is a perspective view of a driven element of the system of FIG. 13.
FIG. 17 is a top plan view of another revolving apparatus of the system of FIG. 13.
FIG. 18 is a top plan view of another revolving apparatus of the system of FIG. 13.
FIG. 19 is a perspective view of a driven element of the system of FIG. 18.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, an aerial wind power generation system 11 embodying features of the present invention includes a first guide line 14, a first support body 15, a driven element 16, a first tow line 17, a second tow line 18 and a means for generating power 19. The first guide line 14 has a first end 21 that is tethered at the ground or to a structure, and the first guide line 14 extends skywardly at a selected elevation angle to a spaced second end 22 that is attached to the first support body 15. The first support body 15 is an aircraft that is lifted by the wind, such as a kite as shown, or a lighter than air aircraft, such as a blimp or a balloon. Preferably the lift of the first support body 15 can be varied to maintain the elevation angle of the first guide line 14.
The driven element 16 is slidably attached or mounted on the first guide line 14. The driven element 16 is a kite, sail, airfoil or other element that generates both drag and lift from the wind. The first and second tow lines 17 and 18 each connect at one end to the driven element 16. The first tow line 17, and generally the second tow line 18, connect to the means for generating power 19 to rotate the means for generating power 19 to generate power. The means for generating power 19 is generally positioned near the first end 21 of the first guide line 14, and can be an electrical generator, a rotary pump, a compressor or other rotary power generation equipment.
FIGS. 2, 3 and 4 show a driven element 16 including an upper spar 25, a spaced, substantially parallel lower spar 26, and a generally rectangular, flexible fabric sail portion 27 extending between the upper and lower spars 25 and 26. The sail portion 27 includes a plurality of spaced longitudinal spars or battens 28 transverse to the upper and lower spars 25 and 26. The battens 28 are shaped to curve the sail portion 27 into an airfoil shape with greater curvature near the upper spar 25 than near the lower spar 26 to provide increased lift force when needed. The battens can be shaped to provide such curvature by tapering the upper ends 31 relative to the lower ends 32 to make the upper ends 31 more flexible, as in some sailboat or iceboat sails. An airfoil 29 is attached to each end of the lower spar 26 and projects laterally therefrom to further control the shape of the driven element 16. The rotation angle of the airfoils about a horizontal axis can be remotely controlled. The pair of airfoils 29 could also be used along the bottom edge of the sail and would thus be similar to conventional aircraft ailerons.
A pulley block 34 having three pulleys 35 in a triangular arrangement is slidably mounted onto the first guide line 14, with two pulleys 35 above and one pulley 35 below the first guide line 14. A plurality of support lines 37 attach to the pulley block 34, and diverge outwardly and downwardly therefrom to attach in a spaced arrangement along the upper spar 25 of the driven element 16. The first tow line 17 attaches to the upper spar 25 and the second tow line 18 attaches to the lower spar 26.
Although a single driven element 16 is shown, a train or string of driven elements 16 can be used.
FIG. 3 shows the driven element 16 in a high force configuration. The wind acting on the driven element 16 is represented by an apparent wind vector 41. The apparent wind vector 41 is equal to the true wind vector 42 minus the driven element velocity vector 43. The first and second tow lines 17 and 18 are tensioned to bow the sail portion 27 into an airfoil shape and to position the sail portion 27 such that the leading edge 39 of the sail portion 27 points into the apparent wind vector 41. FIG. 4 shows the driven element 16 in a low force configuration. The second tow line 18 is lengthened relative to the first tow line 17, allowing the sail portion 27 to flatten and point into the apparent wind vector 41. The second tow line 18 acts as a control line.
In FIG. 1 the second tow line 18 extends to the means for generating power 19, and in combination with the means for generating power 19 forms a means for changing 45 the driven element 16 between high force and low force configurations. FIG. 5 shows an alternative means for changing 45 the driven element 16 between high force and low force configurations, with the second tow line 18 extending from the lower spar 26 of the driven element 16 to a remote control winch 47 that is mounted on the first tow line 17 and spaced from the upper spar 25 of the driven element 16. The winch 47 can include, by way of example and not as a limitation, a wind or solar powered electrical generator, batteries and a communications device for remote control. The winch 47 lengthens and shortens the second tow line 18. The winch 47 can be used in applications where the weight of the winch 47 is less than the weight of a second tow line 18 extending from the driven element 16 to the means for generating power 19.
Referring to FIGS. 6 and 7, the means for generating power 19 includes an electrical motor/generator 50 with a shaft 51 extending from one end, and spaced first and second reels 52 and 53. Preferably the means for generating power 19 is mounted a rotating platform 55 that rotates about a pivot 56 to maintain the orientation of the power generation system 11 relative to the direction of the wind. The motor/generator 50 is rigidly mounted on the platform 55 with the shaft 51 being supported by spaced support bearings 58 that are also mounted on the platform 55. Three support bearings 58 are shown with one support bearing 58 on the outer sides of each of the positioned first and second reels 52 and 53, and one support bearing 58 between the first and second reels 52 and 53.
The first tow line 17 wraps around the first reel 52 and the second tow line 18 wraps around the second reel 53. The first reel 52 is rigidly attached to the shaft 51 and the second reel 53 is rotably mounted on the shaft 51. The second reel 53 has cylindrical drum 60 mounted on the shaft 51 by bearings, and spaced first and second flanges 61 and 62 at opposite ends of the drum 60. A toothed gear 64 is rigidly attached to the shaft 51 and spaced from the second flange 62. Two control motors 66 are mounted on the outside of the second flange 62 on opposite sides of the shaft 51. A worm gear 67 is connected to and driven by each control motor 66, with the worm gears 67 being parallel and meshing to opposite sides of the toothed gear 64. Two motors are used to provide good mass balance of the reel assembly and thus allow for higher rotation rates. Slipring assemblies 69 on the end of shaft 51 opposite the motor/generator 50 and inside the drum 60 provide power to the control motors 66. Driving the control motors 66 rotates the second reel 53 relative to the first reel 52, lengthening or shortening the second tow line 18 relative to the first tow line 17, thereby providing a means for changing 45 the driven element 16 between high force and low force configurations. Therefore, the second reel 53, toothed gear 64, worm gears 67 and control motors 66 form a means for shortening and lengthening the second tow line 18 relative to the first tow line 17. Alternatively, the means for generating power 19 could include two independent, vertically stacked motor/generators to provide a means for changing 45 the driven element 16 between high force and low force configurations.
The first guide line 14 provides stability to the driven element 16, allowing the use of driven elements 16 with higher power and less stability than the driven elements 16 that could be used without the first guide line 14. The first guide line 14 also guides the driven element 16 along a path having a selected elevation angle, so that the power of the driven element 16 can be further optimized.
FIG. 8 shows an aerial wind power generation system 11 embodying features of the present invention including a first guide line 14, a second guide line 71, a first support body 15, a second support body 72, a driven element 16, a first tow line 17, a second tow line 18 and a means for generating power 19. The first guide line 14 has a first end 21 that is tethered at the ground or to a structure, and the first guide line 14 extends skywardly at a selected elevation angle to a spaced second end 22 that is attached to the first support body15. The second guide line 71 has a first end 74 that is tethered at the ground or to a structure, and the second guide line 71 extends skywardly, spaced from and generally parallel to the first guide line 14, at a selected elevation angle to a spaced second end 75 that is attached to the second support body 72. The first and second support bodies 15 and 72 are each an aircraft that is lifted by the wind, such as a kite as shown, or a lighter than air aircraft, such as a blimp or a balloon. Preferably the lift and angle of attack of the first and second support bodies 15 and 72 can be varied to maintain an optimum elevation angle of the first and second guide lines 14 and 71.
Referring to FIG. 9, the first support body 15 includes a kite 77 and a bridle 78. The kite 77 is generally a modified sled kite and has a substantially rectangular framework 80 with a top spar 81, a spaced bottom spar 82, and two spaced, parallel side spars 83 that extend from the top spar 81 to the bottom spar 82. A sail portion 84 covers the framework 80 and has equal triangular wings 85 extending laterally beyond the side spars 83. The outward corners 86 of the wings 85 are located significantly nearer to the top spar 81 than to the bottom spar 82. A pair of spaced, triangular holes 87 are located in the sail portion 84 near the bottom spar 82 to add stability to the kite 77.
A winch 88 is mounted in each lower corner of the framework 80. Wires 91 extend from each winch 88 to a control module 90, suspending the control module 90 below the bottom 82, intermediate the winches 88, and connecting the control module 90 to the two winches 88. The suspended control module 90 acts as tail for the kite 77, increasing the stability of the kite 77. The control module 90 can include, by way of example, and not as a limitation, a two way radio link to the ground, a rechargeable battery, a wind or solar battery charging device, measurement devices and aircraft warning lighting. The measurement devices can include wind speed, light, altitude, GPS, three dimensional acceleration, temperature, humidity, and orientation sensing and measurement.
The bridle 78 includes two each upper bridle lines 93, lower bridle lines 94 and common bridle lines 95. One end of each upper bridle line 93 connects to an outward corner 86 of a wing 85 of the sail portion 84. One end of each lower bridle line 94 connects to a winch 88. The other ends of the upper and lower bridle lines 93 and 94 on each side of the kite 77 connect together and to one end of a common bridle line 95. The other ends of the common bridle lines 95 connect together and to the second end 22 of the first guide line 14. The lower bridle lines 94 in combination with the winches 88 can vary the angle of attack of the kite 77 relative to the wind, thereby forming a means for varying lift 96 (or drag) of the kite 77. Differential control of the lower bridle line lengths will allow for azimuth angle control with respect to the wind direction. Although a single kite 77 is shown, a train of kites 77 can be used to form the first or second support body 15 or 72.
FIG. 10 shows the kite 77 with a modified bridle 97 for providing support to both the first and second guide lines 14 and 71. One end of each upper bridle line 93 connects to an outward corner 86 of a wing 85 of the sail portion 84. One end of each lower bridle line 94 connects to an end of the bottom spar 82 of the framework 80 of the kite 77. A tube 98, sized to extend between the first and second guide lines 14 and 71, has the control module 90 incorporated into the middle and the winches 88 incorporated into opposite ends. The other ends of the upper bridle lines 93 connect to opposite ends of the tube 98. The other ends of each of the lower bridle lines 94 connects to a winch 88. The second end 22 of the first guide line 14 connects to one end of the tube 98 and the second end 75 of the second guide line 71 connects to the opposite end of the tube 98. The winches 88 shorten or lengthen the lower bridle lines 94 to vary the angle of attack of the kite 77 relative to the wind.
As shown in FIG. 11, the first support body 15 can be a blimp 99 with a transverse support bar 100. The second end 22 of the first guide line 14 connects to one end of the support bar 100 and the second end 75 of the second guide line 71 connects to the opposite end of the support bar 100. The use of the blimp 99 eliminates the need to bring the aerial portions of the power generation system 11 to the ground during low wind conditions and may allow for larger scale systems with higher power generation.
FIG. 12 shows the driven element 16 with pulleys 35 at opposite ends of the upper spar 25 to slidably mount the driven element 16 on the spaced first and second guide lines 14 and 71. A plurality of bridle lines 101 attach at one end in a spaced arrangement to the upper spar 25 and converge to attach to the first tow line 17. A plurality of bridle lines 101 attach at one end in a spaced arrangement to the lower spar 26 and converge to attach to the second tow line 18. The first and second tow lines 17 and 18 are shown extending beyond the driven element 16 and may attach to additional driven elements 16 that are above and downwind from the shown driven element 16.
Referring to FIG. 13, an aerial wind power generation system 103 embodying features of the present invention includes a plurality of aerial wind powered driven elements 104, a tow line 105 for each of the driven elements 104, a means for changing 106 each of the driven elements 104 individually between high force and low force configurations, a revolving apparatus 107, and a means for generating power 108. The revolving apparatus 107 has a center 110 and, for each driven element 104, a tow line attachment point 111. The revolving apparatus 107 is represented by circle 112 and the tow line attachment points 111 are evenly spaced around the periphery of the revolving apparatus 107. One end of each tow line 105 connects to a driven element 104 and the other end of each tow line 105 connects to a tow line attachment point 111. The means for generating power 108 is linked to and driven by the revolving apparatus 107. The means for generating power 108 can be directly connected or can be linked by gears, belts, driveshafts or other means, and might be located near the center 110 and driven by a rotating shaft below the revolving apparatus 107.
FIGS. 14 and 15 show a revolving apparatus 107 with four cross bars 113 projecting horizontally from the center 110, and spaced ninety degrees from each other. At the end of each cross bar 113, opposite the center 110, an upright member 114 projects upwardly and transversely. An upper rotating collar 115 rotates around the upper end of each upright member 114 and a lower rotating collar 116 rotates around the lower end of each upright member 114. The upper rotating collar 115 provides the tow line attachment point 111. The lower rotating collar 116 provides a control line attachment point 118 for one end of a control line 119. The opposite end of the control line 119 connects to the driven element 104.
As shown in FIG. 16, a driven element 104 includes an upper spar 133, a lower spar 134 spaced from the upper spar 133, and a rectangular sail portion 135 extending between the upper and lower spars 133 and 134. A plurality of upper bridle lines 136 connect in a spaced arrangement to the upper spar 133 and converge to connect to the tow line 105. A plurality of lower bridle lines 137 connect in a spaced arrangement to the lower spar 134 and converge to connect to the control line 119. Three sled kites 138 are connected to the driven element 104 by support lines 139, to increase stability and support, with a kite 138 connecting to each end of the upper spar 133 and one kite 138 connecting to the middle of the lower spar 134. The angle of attack of the driven element 104 relative to the wind changes as the tow line 105 and control line 119 are pulled in or let out relative to each other, changing the driven element between high force and low force configurations. A similar change in the angle of attack of the kites 138, as described above, might also be used in synchronization with the changes in the driven element.
Referring to FIG. 14, when a cross bar 113 is moving directly downwind, the respective upright member 114 projects downwind. At this position the end of the cross bar 113 has the longest distance, relative to other points of rotation of the revolving apparatus 107, to the attachment of the tow line 105 to the upper bridle lines 136. The lengths of the tow line 105 and control line 119 are tailored so that the driven element 104 is in the highest force configuration when the end of the cross bar 113 is moving directly down wind. The cross bar 113 moving directly upwind has the shortest distance, relative to other points of rotation of the revolving apparatus 107, from the end of the cross bar 113 to the attachment of the tow line 105 to the upper bridle lines 136 and this is the position of the lowest force configuration. The upright member 114 and control line 119 provide the means for changing 106. The driven elements 104 are pulled downwind by the wind in high force configurations and upwind by the revolving apparatus 107 in low force configurations, causing the revolving apparatus 107 to revolve and to drive the means for generating power 108.
The means for changing 106 can be a remote control system as described above or other mechanical means for lengthening and shortening the tow line 105 and control line 119 relative to each other. The means for generating power 108 can be an electrical generator, a liquid pump, a compressor or other power transfer device. The power generation system 103 can be scaled from smaller to larger sizes. For smaller sizes of the power generation system 103, the cross bars 113 of the revolving apparatus 107 can be self supporting. Larger versions of the power generation system 103 could have the revolving apparatus 107 as large as a revolving agricultural irrigation system. The cross bars 113 of a large revolving apparatus 107 can be supported by wheels 124 and linked by cables 125. The wheels 124 can carry and drive a generator 126.
FIG. 17 shows an aerial wind power generation system 103 with another revolving apparatus 128 having an endless, closed track 129 with a plurality of spaced, linked cars 130 on the track. The track 129 can be a railroad type track and the cars 130 can be similar to railroad cars. The track 129 does not have to have a circular shape and can be shaped to optimize power generation. Generally, the means for generating power 108 is carried on the cars 130 and connected to wheels 131 to generate power. The tow line 105 attaches forwardly on the car 130 and the control line 119 attaches rearwardly on the car 130, to change the driven element between high force and low force configurations as the cars 130 travel around the track. The aerial wind power generation system 103 could alternatively have a revolving apparatus with a plurality of towers with bullwheels similar to ski chairlifts and aerial trams. A cable could pass around the bullwheels in a generally circular path with tow lines 105 and control lines 119 attaching to the cable.
FIG. 18 shows an aerial wind power generation system 103 with another revolving apparatus 141 having a center 142 with a pair of cross bars 143 projecting horizontally in opposite directions from the center 142. A tow line attachment point 144 is provided at the end of each cross bar 143, opposite the center 142. A tow line 105 connects a driven element 145 to each tow line attachment point 144. Referring to FIG. 19, the driven element 145 shown is a modified sled kite and has a substantially rectangular framework 147 with a top spar 148, a spaced bottom spar 149, and two spaced, parallel side spars 150 that extend from the top spar 148 to the bottom spar 149. A sail portion 151 covers the framework 147 and has equal triangular wings 152 extending laterally beyond the side spars 150. The outward corners 153 of the wings 152 are located significantly nearer to the top spar 148 than to the bottom spar 149.
A bridle 155 for the driven element 145 includes two upper bridle lines 156 and two lower bridle lines 157. The upper bridle lines 156 connect at one end to corners 153, and the lower bridle lines 157 connect at one end to opposite ends of the bottom spar 149. A generally spherical control module 158 incorporates four winches 159 with the opposite ends of the upper and lower bridle lines 156 and 157 each connecting to a separate winch 159. The control module 158 connects to the upper end of a tow line 105. The control module 158 is remotely controlled and can change the length of each of the upper and lower bridle lines 156 and 157 independently. The control module 158 and the upper and lower bridle lines 156 and 157 provide a means for changing 106 the driven element 145 between high force and low force configurations, and a means for varying 160 the azimuth angle of the driven element 145.
Referring again to FIG. 18, the direction of the wind is shown by wind vector 162. By varying the azimuth angle of the driven elements 145, the driven elements 145 can fly at an angle relative to the wind vector 162. The azimuth angle of the driven elements 145 is selected through the rotation of the revolving apparatus 141 so that the driven elements 145, through the tow lines 105, each generate torque on the cross bars 143 over an arc of more than 180 degrees of the rotation of the revolving apparatus 141. By generating torque for more the 180 degrees, the driven elements 145 generate more power than would be generated without a means for varying 160 the azimuth angle of the driven element 145.
Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made by way of example and that changes in details of structure may be made without departing from the spirit thereof.
Patent Application
20070120005
