Biased drive assemblies for heliostats
A drive assembly for a heliostat is described, wherein the drive assembly may be configured to dynamically adjust the position of an attached reflector in concentrated solar power applications. The drive assembly may be further configured to provide for biasing of the reflector to reduce backlash due to external loads. The biasing force may be provided by at least one of a spring, counterweight, or offset of the center of gravity of the reflector or other attachment, or some combination thereof.
1. A heliostat drive assembly for dynamically adjusting the position of a reflector, the drive assembly comprising:
a drive chassis;
at least one drive shaft;
a reflector channel;
an azimuth gear transmission comprising a series of interlocking spur gears, wherein the azimuth gear transmission is configured to rotate the drive shaft about an azimuth direction via an azimuth output gear;
an elevation gear transmission comprising a series of interlocking cluster spur gears and at least one worm gear, wherein the elevation gear transmission is configured to rotate the reflector channel about an elevation direction via an elevation output gear;
an azimuth torsion spring that surrounds said drive shaft, wherein said azimuth torsion spring is configured to supply a biasing force on said azimuth output gear; and
an elevation torsion spring connected to said elevation output gear, wherein said elevation torsion spring is configured to supply a biasing force on said elevation output gear.
2. The heliostat drive assembly of claim 1 , wherein the heliostat drive assembly further comprises a reflector mounted to said reflector channel.
3. The heliostat drive assembly of claim 1 , wherein the azimuth and elevation torsion springs are configured such that they each supply a biasing force based on predicted or actual wind loads.
4. The heliostat drive assembly of claim 1 , wherein the azimuth and elevation gear transmissions are housed in gear enclosures.
5. The heliostat drive assembly of claim 4 , wherein said gear enclosures are made integral with the drive chassis.
6. The heliostat drive assembly of claim 1 , wherein the azimuth and elevation gear transmissions each comprise a gear biased into engagement with at least one other gear using said azimuth or elevation torsion springs.
7. The heliostat drive assembly of claim 2 , wherein the center of gravity of the reflector biases the at least one drive shaft.
8. The heliostat drive assembly of claim 1 , wherein the magnitude of the biasing forces supplied by the azimuth or elevation torsion springs may be adjusted such that there always exists a biasing force through the heliostat range of motion necessary for the heliostat to reflect incident sunlight to the central tower in a concentrated solar power plant.
9. The heliostat drive assembly of claim 1 , wherein the elevation output gear comprises an arc segment of gear teeth, wherein the arc segment may be between 120 and 150 degrees.
10. The heliostat drive assembly of claim 9 , wherein the elevation output gear comprises:
a center face outfitted with a plurality of bolt holes through which fasteners connect said elevation output gear to said reflector channel;
a spring retaining aperture through which a tip of said elevation torsion spring is held; and
a protrusion configured to contact the elevation torsion spring during actuation of said elevation output gear through its range of motion, wherein said torsion spring induces a biasing force on said elevation output gear when said torsion spring makes contact with said protrusion.
11. The heliostat drive assembly of claim 1 , wherein the azimuth torsion spring is larger than the elevation torsion spring.
12. The heliostat drive assembly of claim 11 , wherein the azimuth torsion spring has a greater stiffness than the elevation torsion spring.