Abstract:
An aerial power generation system includes wind driven elements that are in the form of rectangular sails. The sails are configured and shaped to provide maximum force from both lift and drag during the downwind phase of operation and minimum force during the upwind phase. Guide lines, support elements such as kites or blimps, and/or radio controlled airfoils add stability to the system and provide better control over angular orientation and direction of motion. Power transfer is through one or more cables connected from the wind driven elements to various electromechanical devices on the ground. Another embodiment of the aerial power generation system includes a revolving apparatus and two or more wind powered driven elements connected by tow lines to the revolving apparatus.

Description:
TECHNICAL FIELD  
       [0001]     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  
       [0002]     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.  
         [0003]     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.  
         [0004]     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.  
         [0005]     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.  
         [0006]     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  
       [0007]     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  
       [0008]     Details of this invention are described in connection with the accompanying drawings that bear similar reference numerals in which:  
         [0009]      FIG. 1  is a perspective view of a aerial wind power generation system embodying features of the present invention.  
         [0010]      FIG. 2  is a front elevation view of a driven element of the system of  FIG. 1 .  
         [0011]      FIG. 3  is a side elevation view of a driven element of the system of  FIG. 1 , in a high force configuration.  
         [0012]      FIG. 4  is a side elevation view of a driven element of the system of  FIG. 1 , in a low force configuration.  
         [0013]      FIG. 5  is a side elevation view of a driven element of the system of  FIG. 1 , with an alternative control line arrangement.  
         [0014]      FIG. 6  is a top plan view of a means for generating power of the system of  FIG. 1 .  
         [0015]      FIG. 7  is a sectional view taken along line  7 - 7  of  FIG. 6 .  
         [0016]      FIG. 8  is a perspective view of another aerial wind power generation system embodying features of the present invention, with two guide lines.  
         [0017]      FIG. 9  is a perspective view of a support body of  FIG. 8 .  
         [0018]      FIG. 10  is a perspective view of another support body for the system of  FIG. 8 .  
         [0019]      FIG. 11  is a side elevation view of another support body for the system of  FIG. 8 .  
         [0020]      FIG. 12  is a perspective view of a driven element for the system of  FIG. 8 .  
         [0021]      FIG. 13  is a top schematic view of another aerial wind power generation system embodying features of the present invention.  
         [0022]      FIG. 14  is a top plan view of a revolving apparatus of the system of  FIG. 13 .  
         [0023]      FIG. 15  is a partial side elevation view of the revolving apparatus of the system of  FIG. 14 .  
         [0024]      FIG. 16  is a perspective view of a driven element of the system of  FIG. 13 .  
         [0025]      FIG. 17  is a top plan view of another revolving apparatus of the system of  FIG. 13 .  
         [0026]      FIG. 18  is a top plan view of another revolving apparatus of the system of  FIG. 13 .  
         [0027]      FIG. 19  is a perspective view of a driven element of the system of  FIG. 18 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]     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 .  
         [0029]     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.  
         [0030]      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.  
         [0031]     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 .  
         [0032]     Although a single driven element  16  is shown, a train or string of driven elements  16  can be used.  
         [0033]      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.  
         [0034]     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 .  
         [0035]     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 .  
         [0036]     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.  
         [0037]     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.  
         [0038]      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 body 15 . 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 .  
         [0039]     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 .  
         [0040]     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.  
         [0041]     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 .  
         [0042]      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.  
         [0043]     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.  
         [0044]      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 .  
         [0045]     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 .  
         [0046]      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 .  
         [0047]     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.  
         [0048]     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 .  
         [0049]     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 .  
         [0050]      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.  
         [0051]      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 .  
         [0052]     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 .  
         [0053]     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 .  
         [0054]     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.