US20110108019A1

US20110108019A1 - Heliostat joint

Info

Publication number: US20110108019A1
Application number: US13/001,855
Authority: US
Inventors: Alan B. Minick; Ronald Daniel
Original assignee: Pratt and Whitney Rocketdyne Inc
Current assignee: SOLARRESERVE TECHNOLOGY LLC
Priority date: 2008-08-18
Filing date: 2009-08-18
Publication date: 2011-05-12
Also published as: WO2010022027A3; CN102124284A; WO2010022027A2

Abstract

A heliostat includes a joint with a range of motion in both elevation and azimuth of more than 90 degrees.

Description

The present disclosure claims priority to U.S. Provisional Patent Disclosure Ser. No. 61/089,843, filed Aug. 18, 2008.

BACKGROUND

The present disclosure relates to a heliostat, and more particularly to a joint therefor. Current heliostats may have a relatively limited range of motion both in azimuth as well as in elevation. The relatively limited range of motion may require configuration changes for best operation at different field positions and at different latitudes. This may result in the use of different heliostat configurations in different fields or even in different parts of the same field to focus the sun's energy on the receiver.
The relatively limited range of motion may also require some heliostats to reposition themselves 180 degrees at specific times during the day to continue tracking the sun. This action typically requires approximately 15 minutes during which the sun's energy is not captured.

SUMMARY

A heliostat according to an exemplary aspect of the present disclosure includes a joint with a range of motion in both elevation and azimuth of more than 90 degrees.
A heliostat according to an exemplary aspect of the present disclosure includes a pedestal which defines a longitudinal axis, the pedestal defines a first radius. A first link is movably mounted to the pedestal about a first axis. A second link movably mounted to the first link about a second axis, the second axis displaced from the longitudinal centerline by at least the first radius.
A heliostat according to an exemplary aspect of the present disclosure includes a joint having a first member and a second member, wherein the first member has an axis of rotation that is skew to an axis of rotation of the second member, wherein the axis of the first member is offset a first distance from the axis of the second member, and wherein the second member has a radial length about the second axis at least approximately ½ of the first distance.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiment. The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1 is a general schematic view of a solar power tower system for use with the present invention;

FIG. 2 is a perspective view of a heliostat;

FIG. 3A is a side view of a heliostat with the heliostat array in a first position;

FIG. 3B is a top view of a heliostat with the heliostat array in a second position;

FIG. 4 is a perspective view of a first link for a joint for the heliostat;

FIG. 5 is a perspective view of a second link for a joint for the heliostat;

FIG. 6 is a perspective view of another embodiment of the first link for a joint for the heliostat;

FIG. 7A is a side view of a heliostat with the heliostat array in the first position illustrating a drive system;

FIG. 7B is a top view of a heliostat with the heliostat array in a second position illustrating a drive system;

FIG. 8 is a top expanded view of the drive system; and

FIG. 9 is a side expanded view of the drive system.

DETAILED DESCRIPTION

Referring to FIG. 1, a solar power tower system 20 includes a high concentration central receiver system 22 having a receiver 24 coupled to a tower structure 25 at a predetermined height above ground to receive solar radiation S from a multiple of sun-tracking mirrors or heliostats 26. Molten salt or other thermal transfer fluid is communicated from a cold storage tank system 28 through the central receiver system 22 and heated. The heated thermal transfer fluid is then communicated to a hot storage tank system 30. When power is required, the hot thermal transfer fluid is pumped to a steam generator system 32 that produces steam. The steam drives a steam turbine/generator system 34 that creates electricity for communication to a power grid. From the steam generator, the thermal transfer fluid is returned to the cold storage tank system 28 for storage until reheated in the central receiver system 22 while the steam is recovered through a condenser system 36. It should be understood that although a particular component arrangement is disclosed in the illustrated embodiment, any arrangement which makes use of heliostats will also benefit from the present disclosure.
Referring to FIG. 2, the heliostat 26 generally includes a pedestal 40, a joint 42, a frame assembly 44, and a heliostat array 46. The pedestal 40 supports the joint 42 to permit articulation of the frame assembly 44 and thus the heliostat array 46 to track the sun and focus the solar radiation S as required.
Referring to FIG. 3A, the pedestal 40 may be a generally cylindrical column which defines a longitudinal centerline A and a radius r1 (FIG. 3B). A semi-spherical cap 48 in the disclosed, non-limiting embodiment tops the pedestal 40.
The joint 42 generally includes a first link 50 and a second link 52. The first link 50 includes a first arcuate arm 54 with end pivots 54A, 54B and a second arcuate arm 56 with end pivots 56A, 56B. The end pivots 54A, 54B, as illustrated define an initial elevation axis B and the end pivots 56A, 56B defines an initial azimuthal axis C (also illustrated in FIG. 4). The end pivots 54A, 54B are oriented relative the end pivots 56A, 56B such that axis B is transverse to axis C. In one non-limiting embodiment axis B is perpendicular to axis C.
The second link 52 includes an arcuate arm 58 with end pivots 58A, 58B (FIG. 5) which engages the end pivots 56A, 56B of the first link 50 (along axis C). Alternatively, the first link 50′ includes a single end pivot 56C (FIG. 6).
The first link 50 is movably mounted to the pedestal 40 about axis B. The second link 52 is movably mounted to the first link 50 about axis C. That is, axis C is offset by at least the column radius r1 relative to the longitudinal centerline A by axis B to achieve a significant freedom of motion. The second link 52 positions the heliostat array 46 at least an additional radius r1 from axis C to provide essentially unrestricted azimuth and elevation motion of the heliostat array 46 relative to the pedestal 40. By using the elevational axis B to achieve the offset, the joint 42 provides a significant range of motion in both elevation and azimuth. In one non-limiting embodiment, the range of motion is more than 90 degrees and typically approximately 180 degrees in both elevation and azimuth. It should be understood that the heliostat array 46 may be mounted asymmetrically as desired to optimize load and other operating characteristics and requirements.
Through the unique combination of kinematics, a full range of smooth and continuous motion with no singularity conditions is achieved. The range of motion avoids any unique non-sun gathering maneuvers.
Referring to FIG. 7A, a drive system 70 attached between the pedestal 40 and the heliostat array 46 at two points e, f on the heliostat array 46 defines the orientation and position of the heliostat array 46. The drive system 70 generally includes two drive rods 72A, 72B such as lead screws attached between the heliostat array 46 through mounts 74A, 74B and the pedestal 40 through offset aims 76A, 76B (FIG. 7B).
The drive system 70 adjusts the heliostat array 46 relative to the pedestal 40 to provide articulation to utilize the range of motion provide by the joint 42. The joint 42 essentially provides one point g in space for the heliostat array 46. By defining the two other points e, f as represented by the mounts 74A, 74B the definition and orientation of the heliostat array 46 plane is established. In this manner, there is no singularity point and no need to significantly realign the azimuth to continue tracking the sun. Instead, sun tracking is accomplished in a smooth and continuous manner.
Each of the drive rod 72A, 72B are attached to the mounts 74A, 74B through joints 78A, 78B such as a ball-joint or U-joint to provide a universal connection therebetween. The mounts 74A, 74B support the respective joints 78A, 78B to permit rotation and articulation of the respective drive rod 72A, 72B to position the heliostat array 46.
Referring to FIG. 8, each offset arm 76A, 76B generally includes a shoulder 80, an arm 82, a forearm 84, a rotational bearing 86, a wrist rotator 88 and a drive motor 90. A pivot 92 between the shoulder 80 and the arm 82 permits movement of the arm 82 in a plane P transverse to the pedestal 40 and generally parallel to ground G (FIG. 7A). It should be understood the plane P may be alternatively oriented.
The wrist rotator 88 is mounted to the forearm 84 through the rotational bearing 86 such that the wrist rotator 88 may rotate about the forearm 84 (illustrated schematically by axis F and arrow F). The rotational bearing 86 may essentially include a sleeve which permits rotation F.
The wrist rotator 88 includes a turntable 96 which permits rotation (illustrated by arrow W) of the drive motor 90 and thus the drive rod 72A about an axis W (also illustrated in FIG. 9). That is, the wrist rotator 88 supports the drive motor 90 through which the drive rod 72 may be extended and retracted along axis Y through, for example, a threaded engagement with the lead screw. It should be understood that other drive motors such as linear electric motors or other telescopic arrangements may alternatively or additionally be provided. The turntable 96 may include rotational couplings to communicate electrical power and controls signals to the respective drive motor 90.
The shoulder 80, arm 82 and forearm 84 provide an offset to provide full motion and avoid overextension of the drive rod 72A, 72B. The arm 82 and forearm 84 may each be of a length which is at least equivalent to the radius r1. The arm 82 and forearm 84 may alternatively be of a longer or shorter length dependant in part on whether more or less than a 180 degree range of motion is to be provided. The drive rods 72A, 72B may be maintained in tension when extended and only experience compressive loading when at reduced extension.
The joint 42 facilitates an extended operational range for the heliostat 26 with a robust drive system 70 for effective control and actuation of heliostat 26. Unique maneuvers are avoided and relatively uncomplicated and reliable hardware supports the heliostat array 46.
It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.
Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.
The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.

Claims

1. A heliostat comprising:

a joint with a range of motion in both elevation and azimuth of more than 90 degrees.

2. The heliostat as recited in claim 1, further comprising a pedestal to which said joint is mounted, said pedestal defines a first radius, said joint includes an offset in which a heliostat array azimuthal axis of rotation is displaced at least said first radius from said pedestal longitudinal axis.

3. The heliostat as recited in claim 1, wherein said joint provides a range of motion in both elevation and azimuth of approximately 180 degrees.

4. The heliostat as recited in claim 1, wherein said joint includes no singularity point.

5. The heliostat as recited in claim 1, further comprising a drive system which positions a heliostat array relative to a pedestal.

6. The heliostat as recited in claim 5, wherein said drive system defines two points on said heliostat array and said joint defines one point on said heliostat array.

7. The heliostat as recited in claim 6, wherein said two points are defined in part by a respective drive rod.

8. The heliostat as recited in claim 7, wherein each of said respective drive rods includes a lead screw.

9. The heliostat as recited in claim 7, wherein each of said respective drive rods are mounted to said pedestal through an offset arm structure.

10. A heliostat comprising:

a pedestal which defines a longitudinal axis, said pedestal defines a first radius;

a first link movably mounted to said pedestal about a first axis; and

a second link movably mounted to said first link about a second axis, said second axis displaced from said longitudinal centerline by at least said first radius.

11. The heliostat as recited in claim 10, wherein said first axis is a longitudinal axis.

12. The heliostat as recited in claim 11, wherein said second axis is an azimuthal axis.

13. The heliostat as recited in claim 10, wherein said second axis is perpendicular to said first axis.

14. The heliostat as recited in claim 10, further comprising a heliostat array mounted to said second link.

15. The heliostat as recited in claim 14, further comprising a drive system which positions said heliostat array relative to a pedestal.

16. The heliostat as recited in claim 15, wherein said drive system includes two points attached to said heliostat array, said two points defined in part by a respective drive rod.

17. A heliostat comprising:

a joint having a first member and a second member,

wherein the first member has an axis of rotation that is skew to an axis of rotation of the second member,

wherein the axis of the first member is offset a first distance from the axis of the second member, and

wherein the second member has a radial length about the second axis at least approximately ½ of the first distance.

18. The heliostat as recited in claim 17, wherein said radial length is at least equal to said first distance.

19. The heliostat as recited in claim 17, wherein said joint provides a range of motion in both elevation and azimuth greater than 90 degrees.

20. The heliostat as recited in claim 17, wherein said joint provides a range of motion in both elevation and azimuth of approximately 180 degrees.