Abstract:
The horizontal axis wind turbine of this invention has a space frame structure that enables a light weight blade system to force rotation of numerous small wheels into rolling contact with the surface of at least one ring that extends around the perimeter of said blade system. A portion of the wheels drive rotation of multiple small electrical generators, and air compressors (?), at a high initial RPM, in the numbers needed to produce this wind turbine&#39;s useful power output. 
     For offshore use, a wind turbine structure as described above surmounts two horizontal toroidal members held apart by multiple vertical columns. The lower toroidal member and the vertical columns above this member float at a depth that is nearly half the column heights. Added structure enables the extraction of energy from waves transiting the vertical columns.

Description:
FIELD OF INVENTION 
       [0001]    This invention relates to wind turbines, and in particular to horizontal axis type wind turbines of large diameter. 
       BACKGROUND OF THE INVENTION—PRIOR ART 
       [0002]    Conventional large horizontal axis wind turbines employ two or three long, slender blades cantilevered out from a central, horizontal axle that in turn is raised high in the air atop a tall, slender tower that cantilevers up from the earth&#39;s surface. One result: a small transverse wind force, X, exerted at the tip of a blade will create large (≈30X) tension (upwind) and compression (downwind) stress loads that the entire lengths of both blades and tower must be able to withstand. 
         [0003]    Furthermore, in a conventional horizontal axis wind turbine, power is taken off at the axis of blade rotation, at an RPM that must vary inversely with blade length to avoid an excessive tip speed. The lower RPM associated with greater blade length requires a proportionately heavier axis bearing to support blade rotation, and a heavier gearbox, or if gearless, a larger and heavier generator structure, to produce energy at the power line frequency. 
         [0004]    Wind turbine U.S. Pat. No. 4,417,853, drawing #12 (copy enclosed) shows two potential means for reducing the cost of extracting energy from the wind: 1) Small wheels at the turbine perimeter take off the useful power output from the wind at an initial RPM far higher than the RPM of blade rotation. 2) Upwind perimeter “stay” cables withstand the wind force exerted on the blade area with far less stress than the stress levels experienced by cantilever beam blades sweeping through the same area. However, the intricate cloth blade furling system shown in U.S. Pat. No. 4,417,853 has not proven suitable for large wind turbines. 
       SUMMARY OF THE INVENTION  
       [0005]    To make possible a much larger power output, the present invention replaces the furling cloth sails of U.S. Pat. No. 4,417 853, with blades having a more conventional airfoil shape, that are supported within a surrounding structure which can counter wind force exerted on the blades with far less weight than is needed by the conventional combination of cantilever beam blades, set atop a cantilever beam type tower. 
         [0006]    In a preferred option, the airfoil shaped blades of this invention extend from a common center of rotation, out to the inner ring of two concentric, nested rings. The inner ring attached to the blades is able to move smoothly through the interior of the outer nested ring by means of a rolling contact of the inner ring with a sufficient number of wheel mounted tires that drive rotation of multiple generators, and air compressors (?) mounted at intervals around the internal surface of the outer nested ring. This enables producing a useful power output at a far higher initial RPM than the RPM of blade rotation, in response to the wind&#39;s force. 
         [0007]    Individual blades as used in this invention can range in design from simple, impact air inflated, cloth airfoils whose angle of incidence to local airflow cannot be changed, to multiple, tandem, rigid airfoil segments, each of whose trailing edge flaps can be rotated in unison by a central actuator, to a common angle of attack to local airflows, as a means of maximizing recovery of energy from wind transiting the blade system. (Impact air inflated cloth airfoils have the advantage of weighing a tiny fraction of the weight needed for cantilever beam blades, and are easily made retractable for protection from severe weather.) 
         [0008]    “Stay” cables extend from between adjacent segments of the light weight airfoils made possible by this invention, fore and aft to ancillary structure having the depth and arrangement needed to directly absorb the axial force that the wind exerts oh the blade system, with far less stress than is experienced by the blades of a cantilever beam blade system. 
         [0009]    The space frame type structure for wind turbines as described in this invention, will greatly reduce the structural weight now needed to extract energy from the wind, and may enable the construction of wind turbines of much larger blade swept area than those currently available, that can intercept the wind at an increased height above ground level where the wind typically has a greater energy content. 
         [0010]    Other features and advantages of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1 , a side view of the wind turbine of this invention, illustrates that a substantial land area is needed for its deployment, in order to achieve a much lighter structure. 
           [0012]      FIG. 2  is a partial longitudinal section, showing how a single turbine blade is supported in order to drive rotation of multiple generators mounted out along this wind turbine&#39;s circumference 
           [0013]      FIG. 3  is a frontal view of the wind turbine, showing means for supporting nested perimeter rings in a vertical position, to enable their rotation in azimuth, into the current wind direction. 
           [0014]      FIG. 4  shows a sea going version of this invention, with modifications that allow the wind turbine of this invention to operate in this more challenging environment. 
           [0015]      FIG. 5  shows how a central actuator can cause multiple blade segment trailing edge flaps to rotate all segments to a uniform angle of attack to each segment&#39;s own, local airflow. 
           [0016]      FIG. 6  shows how retractable air impact inflated blades can cover much smaller chord biplane blades, to better cope with a wide range of wind speeds and weather conditions. 
           [0017]      FIG. 7  compares the stress levels experienced by a cantilever beam type wind turbine blade, with the stress levels experienced by the equivalent structure of this invention. 
       
    
    
       [0018]    Final  FIG. 12  is reproduced from U.S. Pat. No. 4,417,853, with additions to this figure to emphasize elements of U.S. Pat. No. 4,417,853 that are pertinent to the present invention. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    As shown in  FIG. 1 , the present invention is a cable-stayed, space frame-type horizontal axis wind turbine whose base extends out over a far larger area, land or sea, than is needed for base installation for a conventional horizontal axis wind turbine.  FIG. 7  incorporates a stress analysis explaining why this broad base enables a major reduction in wind turbine stress loads developed in response to wind force. 
         [0020]      FIG. 1 , and in more detail  FIG. 2 , show how a radial array of blades segments  1  can extend from a horizontal axis of rotation  2 , out along radial cables  3 , to an inner ring  4  (see  FIG. 2 ) that moves through the interior of outer ring  5  in pace with the rotation of blade segments  1 , in order to force the rotation of electrical generators  6 , and air compressors?, mounted circumferentially along the interior of outer ring  5 , at an initial RPM that can be 100 or more times the RPM of blade system rotation. 
         [0021]      FIG. 1  illustrates that this major reduction in wind induced stress loads will require a base structure extending over a far larger land area that is occupied by the footing for a conventional HAWT, but can do so with little interference to the use of this same land area for farming and ranching. 
         [0022]    In  FIGS. 1 and 2 , wind force exerted on the blade system is reacted primarily by stays  7  that extend from multiple points along blade segments  1 , to the upper ends of fore and aft spars  8 , whose lower ends rest on a central pivot  9 , itself located at the ground level intercept of vertical axis line  10 , around which nested blade rings  4 ,  5  rotate in azimuth to stay headed into the current wind direction. 
         [0023]    Shroud cables  11  prevent spars  8  from being pulled upward by stay cable tension, by pulling upward on wheels  12  that roll in an inverted position along a suitable downward facing surface of flange  14  molded into curb  13 . Curb  13  is elevated on columns  16  to free the local land surface for use in farming and ranching. Curb lid  15  serves to keep the various elements riding the curb moving in unison, and also keeps the curb top clean. 
         [0024]    In  FIG. 1 , rings  4  and  5  are further supported for operation in a vertical position by lateral side spars  17  whose lower ends rest on jib cars  18 . Jib cars  18  use opposing wheels sets  19  to secure the lower ends of side spars  17  to suitable surfaces of curb  13 . Wheel sets  19  then allow rotation of side spars  17 , along with the blade system, into the current wind direction. 
         [0025]      FIG. 2  depicts in more detail one of the many alternatives for blade structure that are made possible by this invention. In  FIG. 2 , multiple light weight airfoils are supported. Sequentially as blade segments  1 , along radial cables  3  that extend from a common horizontal axis of rotation  2 , out through the length of blade segments  1 , to a lug  4   a  attached, through a slot in outer ring  5 , to the inner edge of ring  4 , the inner ring of the two nested, concentric rings  4  and  5  that extend around the perimeter of the blade system of this invention. 
         [0026]    Inner ring  4  is supported for circumferential rotation in step with blade segments  1 , through the interior of outer ring  5 , by engaging multiple air inflated tires on outer ring wheels  20  that drive power generating equipment distributed at regular intervals around the interior of outer nested ring  5 . If needed, idler wheels, not shown, can be interspersed between wheels  20  in the numbers needed to keep inner ring  4  moving smoothly through the interior of outer ring  5 . 
         [0027]    An alternative arrangement eliminates the inner nested ring  4  and instead uses the blade system to drive rotation of tires on wheels that move with the blade system while bearing on appropriate surfaces of the remaining ring  5 , but this alternative seems likely to make the transfer of power output from tire/wheel driven generators to ground level much more difficult to accomplish reliably, and could eliminate wheel driven compression of air for energy storage. 
         [0028]    In  FIG. 2 , tension maintenance in the array of wind force absorbing stay cables  7  is achieved by terminating the front (windward) end of each stay cable  7  with a tensioning device,  21  mounted on a shield  22  that is rotatably mounted within a collar  23  located at the point of convergence of stay cables  7  at the upper end of each diagonal spar  8 . Vibration of stay cables  7  can be suppressed by surrounding their termini with viscous material. If additional damping is needed, adjacent stay cables  7  can be held together for that portion of their lengths where they run nearest each other, by means of cable clamps. ( 7   a ) having a viscous damping action, without substantial effect on the adjustment of tension in individual members of grouped stay cables  7  by tensioning devices  21  mounted on shield  22 , within collar  23 . 
         [0029]    Wind force that is exerted on the outer nested ring  5  may require perimeter stays.  7   b  that extend fore and aft from outer nested ring  5  to terminate on the same diagonal spar mounted collars  23  that support rotation of shields  22  in synchrony with rotation of fore and aft sets of stay cables  7 , along with the blade system. 
         [0030]      FIG. 3  offers a frontal view, showing how for greater ground clearance, nested rings  4  and  5  can be supported on a sling cable  25  that hangs between the tops of two side spars  17 , which in turn rise from jib cars  18 , up near to lateral quadrant locations on outer ring  5 . Jib car  18  mounted hinge mechanisms  24   a  and  24   b , in conjunction with a center pivot mounted hinge  24   c , will still allow the blade system of this, invention to be lowered from a vertical to a horizontal position for maintenance, and to reduce public annoyance when this wind turbine fails to rotate for lack of wind. Two smaller, V shape booms  26 , extend from center pivot  9 , via hinge  24   c , to appropriate points along outer ring  5  that will prevent any displacement of the blade system away from vertical axis  10 . 
         [0031]    The wind turbine structure described above can be modified for offshore use as shown in  FIG. 4 , by supporting nested rings  4  and  5  on a circular crib-like arrangement of two horizontal rings  32  and  33 , separated by multiple vertical columns  34 , wherein the lower ring  32 , and columns  34  have sufficient water displacement volume to support the weight of the entire structure to a depth which submerges lower ring  32  completely and columns  34  to an appropriate portion of their lengths to enable their use in recovering energy from transiting waves. Cables  35  moor this floating structure to the ocean floor. If greater resilience to severe storms is needed, sag weights  36  can be added to cables  35 . A separate tower  37 , if centrally positioned within this floating structure, can provide a protected means for sending a useful power output down to the sea bed for its further transport to shore and the point of use. 
         [0032]    Ring  33  at the top of columns  34  can then support wind turbine structure  38 , by means which allow rotation of structure  38  into the current wind direction. This may consist of supporting the weight of wind turbine structure  38  on multiple, interconnected jib cars  18  that travel along the upper surface of upper ring  33 . 
         [0033]    Wind turbine structure  38  differs from the land based version of this invention in requiring a replacement for diagonal spars  8  as a means of absorbing wind force exerted on the blade system via stay cables  7 . This may consist of: 1) a blade rotational, axis spar  39  that extends horizontally between opposite focal points for stay cables  7 , 2) four nearly vertical spars  40  whose lower ends rest on jib cars  18  and whose upper ends converge in pairs at the two focal points for stay cables  7 , and cables  41  that interconnect the foregoing elements into a structure that can rotate in azimuth into the current wind direction, and that will prevent the blade system from collapsing forward, should the wind suddenly reverse direction. 
         [0034]    A major concern is that an extreme wave could exert enough lateral pressure on submerged ring  32  and columns  34  to overstress the sea bed anchoring system. This possibility can be minimized by: 
         [0035]    1) Submerging ring  32  to a sufficient depth to greatly diminish ring motion in response to the passage of a storm wave, 
         [0036]    2) By placing “sage” weights on tower anchor cables  35  at a suitable point along each cable in the direction of the arrow  36 , so that greater resilience is offered to wave side force exerted on lower ring  32  and column  34 . 
         [0037]    Optionally, the rotation of inner nested ring  4  by the blade system may be used to drive rotation of air compressors as well as generators, in order to compress air for transmission to tower  37  and from there transmission to underground storage via passage through a volume of eutectic salt that is stored within tower  37 , for later recovery to meet system demand for electrical energy. Optionally, submerged ring  32 , and partially submerged columns  34  can support means  42  for extracting energy from wave motion in the surrounding water body, to supplement energy derived from the wind. 
         [0038]    Many novel wind turbine blade systems are made possible by this invention. For one example,  FIG. 5  shows how a central scissors mechanism,  27 , can induce radial motion of rods  28  that in turn, through linkages  29 , rotate the trailing edge elevators  30  of all blade segments  1  to achieve a uniform angle of incidence to each blade segment&#39;s local airflow, for the purpose of recovering maximum energy from the wind. 
         [0039]    As a second example of the novel blade system made possible by this invention,  FIG. 6  shows how blade segments  1  can consist of impact air inflated cloth blade segments for light winds that envelop much smaller chord biplane blade segments  31 , that 1) are able to resist stronger winds, and 2) can be made to resist a substantial portion of the centripetal component of stay cable tension that would otherwise be exerted on perimeter nested rings  4  and  5 .