Stabilized horizontal-axis wind turbine
The nacelle of a horizontal axis wind turbine is fixedly mounted on a tower, and the tower is mounted off-center with respect to a ring around which it is rotatable. The tower is a tripod. Two legs of the tripod are of fixed length and lie in a plane perpendicular to the axis of rotation of the turbine blades. The third leg of the tripod is of adjustable length and is aligned with the axis of rotation of the turbine blades. The third leg thus may be controlled to adjust for pitching of the base and other purposes. Multiple turbines, spaced apart laterally, may be mounted on a platform in a fixed orientation, with the platform rotatably mounted off-center relative to a base.
1. A wind turbine comprising a set of generally vertical blades which sweep around a generally horizontal axis of rotation; a nacelle comprising at least a generally horizontal shaft driven by the set of generally vertical blades and a drive train; an upright tripod structure supporting the nacelle and the set of generally vertical blades, the upright tripod structure extending below a sweep of the set of generally vertical blades, and a generally horizontal base supporting the upright tripod structure, wherein,
a pitch of the axis of rotation of the set of generally vertical blades relative to the upright tripod structure is adjustable and is controlled by a pitch control mechanism, the pitch control mechanism comprising an adjustable-length strut having a load path to the generally horizontal base,
the adjustable length strut causing part or all of two generally vertical legs of the upright tripod structure to pivot with respect to the generally horizontal base.
2. The wind turbine of claim 1 wherein the pitch control mechanism includes a controller programmed to orient the axis of rotation of the set of generally vertical blades away from horizontal to slow rotation of the set of generally vertical blades.
3. The wind turbine of claim 2 wherein the set of generally vertical blades lack a mechanism to control the pitch of individual blades relative to the generally horizontal axis of rotation.
4. The wind turbine of claim 1 wherein the upright tripod structure comprises two generally vertical legs spaced behind the set of generally vertical blades and a third leg and wherein the pitch of the axis of rotation of the set of generally vertical blades relative to the generally horizontal base is controlled by changing a length of the third leg.
5. The wind turbine of claim 1 wherein the generally horizontal base is floating, and wherein the pitch control mechanism includes a controller programmed to maintain the axis of rotation of the set of generally vertical blades generally horizontal as the generally horizontal base pitches.
6. The wind turbine of claim 1 , wherein the upright tripod structure maintains the nacelle and set of generally vertical blades fixed against yaw with respect to the upright tripod structure, and the upright tripod structure is rotatably mounted to the generally horizontal base, so that the upright tripod structure, the nacelle, and the set of generally vertical blades rotate together with respect to the generally horizontal base.
7. The wind turbine of claim 6 wherein as the base pitches the center of gravity of the turbine is positioned behind the axis of rotation of the upright tripod structure.
8. The wind turbine of claim 6 comprising an active yaw control at or adjacent the level of the generally horizontal base.
9. The wind turbine of claim 6 comprising a rotatable support for the upright tripod structure, the rotatable support being mounted for rotation within a ring structure on the generally horizontal base.
10. The wind turbine of claim 9 wherein the rotatable structure comprises an inner ring rotating inside the ring structure.
11. The wind turbine of claim 10 wherein ring structure comprises discrete spaced-apart supports supporting the inner ring vertically and horizontally.
12. The wind turbine of claim 6 wherein the generally horizontal base is floating, and wherein the pitch control mechanism includes a controller programmed to maintain the axis of rotation of the set of generally vertical blades generally horizontal as the generally horizontal base pitches.
13. The wind turbine of claim 12 further comprising a brake deployable to hold the upright turbine structure relative to the generally horizontal base when the generally horizontal base pitches or rolls.
14. The wind turbine of claim 6 wherein a plurality of turbines are mounted to the upright tripod structure on a single mounting platform, the mounting platform being rotatable with respect to the generally horizontal base and each of the plurality of turbines being fixed against yaw with respect to the upright tripod structure.
15. The wind turbine of claim 14 wherein the upright tripod structure is mounted with a combined center of gravity of the upright tripod structure and the plurality of turbines mounted to the upright tripod structure behind a center of rotation of the mounting platform.
16. The wind turbine of claim 14 wherein the generally horizontal base is floating, the plurality of turbines each comprises a set of blades, the pitch control mechanism maintaining an axes of rotation of each set of blades substantially horizontal as the generally horizontal base pitches.
17. The wind turbine of claim 1 wherein a plurality of turbines are mounted to the upright tripod structure.