There are disclosed method and apparatus for the production of electrical power from high altitude winds. A kitecraft (12) secured to a ground tether (14) supports a cylindrical drum (10) rotatable about a horizontal shaft (60). The drum comprises a plurality of wheels (24) interconnected by airfoils (26) positioned about the cylindrical surface of the drum. Wind action on the airfoils rotates the drum about the horizontal shaft and turns generators (50) to provide electrical power. The kitecraft (12) and drum (10) assembly is constructed to the maximum practical extent from tension members to reduce weight.
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1. Apparatus for extracting energy from wind at high altitude, comprising:
- means for supporting a load at said high altitude;
- means for flexibly tethering said load supporting means to the surface of the earth;
- a plurality of elongated parallel airfoil elements supported by said load supporting means, said airfoil elements lying on the surface of an imaginary horizontal circular cylinder and rotatable about the horizontal axis of said cylinder in a closed cylindrical path;
- means for positioning said airfoil elements relative to said cylindrical surface whereby relative wind substantially normal to said axis exerts a force on said airfoil elements, causing said elements to rotate about said horizontal axis; and
- means responsive to the movement of said airfoil elements about said horizontal axis for transmitting power to the surface of the earth.
2. The apparatus of claim 1 wherein the airfoil element positioning means is adapted to alternatively position said elements in substantially fixed location about the surface of said cylinder with the aerodynamic lift of the airfoil elements adding to the support provided by the load supporting means.
3. The apparatus of claim 1 wherein said airfoil elements are secured to a plurality of wheels of substantially equal diameter suspended from said load supporting means, said wheels lying in substantially parallel planes spaced along the horizontal axis of said cylinder and rotatable about said horizontal axis.
4. The apparatus of claim 3 wherein:
- said positioning means pivotally secure the airfoil elements to the wheels whereby each airfoil element is rotatable about an attack-angle axis passing substantially through its center of gravity and substantially parallel to said horizontal axis.
5. The apparatus of claim 4 wherein said airfoil elements are substantially identical and wherein each said element has an aerodynamic center displaced downwind from its center of gravity.
6. The apparatus of claim 5 including means for pivotally positioning each of said airfoil elements about its center of gravity.
7. The apparatus of claim 6 wherein said pivotal positioning means comprises means for limiting the rotation of each said airfoil element.
8. The apparatus of claim 3 additionally comprising:
- at least one of said wheels having a circular rim defining a groove encircling its inner surface, and a smaller support wheel engaging and rollable in said groove with its axis secured to said load supporting means for suspending said wheel therefrom.
9. The apparatus of claim 8 wherein said rim defines a pair of axially spaced, coaxial grooves, and wherein at least one support wheel engages each of said grooves.
10. The apparatus of claim 3 wherein each of said wheels comprises:
- a hub;
- a substantially rigid rim; and
- a plurality of tension spokes interconnecting said hub and said rim.
11. The apparatus of claim 3 wherein at least one of said wheels has a circular rim defining a groove encircling its inner surface and said movement responsive means comprises:
- a smaller drive wheel engaging and rollable in said groove;
- an electrical generator; and
- means for transmitting power from said drive wheel to said generator.
12. The method of developing power from the wind at relatively high altitudes comprising:
- raising a load supporting assembly to a high altitude;
- tethering said load supporting assembly in a substantially fixed position relative to the earth;
- supporting with said assembly a plurality of elongated parallel airfoil elements lying on the surface of an imaginary horizontal circular cylinder and movable about the axis of rotation of said cylinder;
- moving said elements about said axis of rotation by wind action; and
- generating electrical power from the movement of said elements.