Patent Application
20130000693
1. Field of the Invention
The present invention is generally directed to apparatuses and methods for positioning an object and, more particularly, to apparatuses and methods for positioning a solar energy capture device using linear actuators.
2. Background
For numerous reasons—including lowering the concentrations of greenhouse gases, strengthening the ozone, reducing global warming effects, and obtaining a sustainable source of energy—energy sources other than fossils fuels are becoming more popular. One common alternative energy source is solar energy.
There are two common systems for generating electricity from solar energy: a thermal system and a photovoltaic system. In a thermal system, a mirror assembly reflects sunlight onto a receiver. The receiver, in turn, may heat a fluid or gas. In some thermal systems, the receiver heats the fluid or gas to power a turbine to create electricity, for example, by turning a fluid into a gas. In other thermal systems, the receiver can simply heat the fluid or gas for process heat applications. In photovoltaic systems, a photovoltaic panel converts sunlight into electricity. In both systems, the position of the solar energy capture device—the mirror assembly in a thermal system or the photovoltaic panel in a photovoltaic system, for example—should continuously change as the position of the sun changes. For example, as the sun moves, the orientation of the mirror assembly needs to change to keep the reflected light focused on the receiver. In photovoltaic systems, the photovoltaic panel should be reoriented to ensure that the panel is orthogonal to the direction of the sunlight to achieve peak efficiency.
In many of these systems, a solar energy capture devices is coupled to a frame post by two direct-drive motors located at the top of the post. One of the motors is aligned to change the elevation angle of the solar energy capture device, and the other motor is aligned to change the azimuth angle of the solar energy capture device. The weight of the motors and their relatively high position on the post can require a frame that is large and, consequently, one that may be expensive and heavy. This requirement can make implementation and scaling of many solar energy systems unduly expensive, especially when increasing the size of solar energy capture devices and the number of devices deployed in an array.
In one embodiment, an apparatus for receiving sunlight includes a frame, a solar energy capture device, a joint, and first and second linear actuators. The joint connects the solar energy capture device to the frame and allows the solar energy capture device to rotate relative to the frame. The first and second linear actuators are coupled to the solar energy capture device. The first and second actuators actuate in combination to rotate the solar energy capture device about a pitch axis, and the first and second actuators actuate differentially to rotate the solar energy capture device about a roll axis. The solar energy capture device may include a mirror assembly or a photovoltaic panel.
In another embodiment, an apparatus includes a frame having a lateral axis and a longitudinal axis, a solar energy capture device, a joint assembly, a first variable length actuator, and a second variable length actuator. The joint assembly connects the solar energy capture device to the frame, while allowing rotation of the solar energy capture device relative to the frame. The joint assembly includes a lower portion connected to the frame to allow rotation of the solar energy capture device about the lateral axis. The joint assembly also includes an upper portion connected to the solar energy capture device and the lower portion to allow rotation of the solar energy capture device about the longitudinal axis. The first variable length actuator has a first pivot end coupled to the solar energy capture device on a first side of the joint assembly, and the second variable length actuator has a second pivot end coupled to the solar energy capture device on a second side of the joint assembly opposite the first pivot end. The first and second actuators actuate in combination to rotate the solar energy capture device about the lateral axis and actuate differentially to rotate the solar energy capture device about the longitudinal axis.
In one embodiment, an apparatus for positioning an object at a desired pitch angle and a desired roll angle includes a frame, an object, a joint, a first linear actuator, and a second linear actuator. The joint connects to the object and the frame to allow rotation of the object relative to the frame. The first and second linear actuators each have a variable length member. The variable length members are coupled to the object and the frame. The lengths of the first and second variable length members are simultaneously and equally changed to rotate the object about a pitch axis, while the length of the first variable length member is differentially changed relative to the length of the second variable length member to rotate the object about a roll axis. The object can be a solar energy capture device.
Methods for using apparatuses according to embodiments described herein are also provided.
In one embodiment, a method for positioning a solar energy capture device comprises moving the solar energy capture device to a desired orientation by collectively actuating first and second linear actuators to rotate the solar energy capture device about a pitch axis and by differentially actuating the first and second linear actuators to rotate the solar energy capture device about a roll axis. The first and second linear actuators are coupled to the solar energy capture device and a frame.
The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art(s) to make and use the invention.
The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements.
In the detailed description that follows, references to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
In one embodiment, frame 200 is adapted to structurally support and position object 100. Frame 200 can be figured to directly or indirectly contact a mounting surface, for example, the ground, a roof, a wall, an overhead surface, or other suitable surface. Frame 200 elevates object 100 above the mounting surface. Frame 200 may define a lateral axis that runs from the left side of frame 200 to the right side of frame 200, and define a longitudinal axis that runs from the front of frame 200 to the back of frame 200. The longitudinal axis may be orthogonal to the lateral axis. Frame 200 can be made of any suitable rigid material having sufficient strength to support object 100. For example, frame 200 can be formed from square tubing, piping, or channel made of iron, aluminum, composites (e.g., carbon fiber composites), wood, plastic, or any other suitable material.
Joint 300 rotatably couples object 100 to frame 200 such that object 100 can rotate relative to frame 200. Joint 300 defines a pitch axis PA and a roll axis RA. In one embodiment, pitch axis PA is parallel to the lateral axis of frame 200, and roll axis RA can project on the longitudinal axis of frame 200 and may be planar with the longitudinal axis of frame 200. When coupled to joint 300, object 100 can rotate about pitch axis PA and roll axis RA. Joint 300 can be a universal joint (U-joint), a ball and socket joint, or any other type of joint that has at least two degrees of freedom. In one embodiment, joint 300 can be made of one or more rotating members.
In one embodiment, apparatus 10 includes at least two linear actuators 400. Linear actuators 400 are coupled to object 100 and are adapted to position the object relative to a source. Linear actuators 400 can include a drive component, for example, a motor or hydraulic pump and cylinder, and a variable length member that can selectively change its length. Linear actuators 400 can selectively apply a force to object 100 by changing the length of the variable length member, which rotates object 100 about pitch axis PA and roll axis RA. Particularly, as further described below, in one embodiment linear actuators 400 may collectively rotate object 100 about pitch axis PA and differentially rotate object 100 about roll axis RA. In some embodiments, apparatus 10 may include two, three, or more than three linear actuators. In one embodiment, each linear actuator 400 may comprise a cable actuation mechanism including a motor and a cable, a hydraulic piston, a scissor-jack, a linear screw drive, or any other suitable linear actuator having a variable length member. Linear actuators 400 coupled to object 100 may comprise the same type or different types of actuators. For example, in some embodiments, first and second linear actuators 400 may both comprise a cable-actuated mechanism. In other embodiments, for example, a first linear actuator 400 may comprise a cable actuator and a second linear actuator 400 may comprise a hydraulic piston actuator.
In one embodiment, apparatus 10 includes control unit 500. Control unit 500 includes a processor and memory. Control unit 500 is operatively connected to linear actuators 400. Control unit 500 is adapted to generate and manipulate control signals that cause the variable length member of linear actuators 400 to change lengths and, thus, change the orientation of object 100.
Apparatus 10 may be used as an individual unit for positioning a single object 100 or as a series of units in an array for positioning a plurality of objects 100. For example, in one embodiment, a plurality of apparatuses 10 each having a solar energy capture device 100 may be arranged in a solar field. In one embodiment such as a thermal system, the plurality of apparatuses 10 may be arranged to concentrate the reflected sunlight onto a receiver that powers a heat engine which, in turn, drives a rotary generator, for example, a turbine. In one embodiment, apparatuses 10 in an array can be arranged in one or more linear or arcuate rows.
Apparatus 10 also includes frame 200. As shown in
In one embodiment, frame 200 further includes a vertically extending front strut 210. In an embodiment, front strut 210 extends upward from the intersection of right diagonal strut 202 and left diagonal strut 204. Frame 200 also includes right diagonal vertical strut 212 and left diagonal vertical strut 214. Right diagonal vertical strut 212 extends from the back portion of right diagonal strut 202 to the top portion of vertical front strut 210. Left diagonal vertical strut 214 extends from the back portion of left diagonal strut 204 to the top portion of vertical front strut 210. Collectively, right and left vertical diagonal struts 212 and 214 help prevent vertical strut 210 from moving, particularly, from rotating front to back or left to right. An intermediate cross strut 216 extends horizontally from right diagonal vertical strut 212 to left diagonal vertical strut 214. Intermediate cross strut 216 stabilizes right and left vertical diagonal struts 214 and 216 and may limit right vertical diagonal strut 214 and left vertical diagonal strut 216 from moving relative to each other.
Apparatus 10 includes joint 300 that rotatably couples solar energy capture device 100 to frame 200. Joint 300 defines pitch axis PA and roll axis RA. In an embodiment, pitch axis PA and roll axis RA are parallel to a plane defined by solar energy capture device 100, and pitch axis PA and roll axis RA are perpendicular. Joint 300 allows solar energy capture device 100 to rotate about pitch axis PA and roll axis RA relative to frame 200.
In an embodiment as shown in
Extending upward from hub 330 is a pair of opposing arms 332 and 334. Arms 332 and 334 are spaced apart to create a gap in a substantially U-shaped configuration. Upper yoke 304 includes a base portion 336 and a pair of opposing arms 338 and 340 extending from the ends of base portion 336 in a substantially inverted U-shaped configuration. Lower yoke 302 and upper yoke 304 are rotatably coupled together by center portion 342. Center portion 342 can be X-shaped or cross-shaped with a first pair of pins 306 extending from opposing legs of the center portion 342 and a second pair of pins 308 extending from the other pair of opposing legs. Accordingly, second pair of pins 306 are perpendicular to first pair of pins 306. First pair of pins 306 are rotatably coupled to lower yoke 302, for example, by coupling pins 306 with ball bearings seated in openings defined in the top portions of arms 332 and 334. Similarly, second pair of pins 308 are rotatably coupled to upper yoke 304, for example, by coupling pins 308 with ball bearings seated in openings defined in the lower portions of arms 338 and 340.
Upper yoke 304 can be coupled to reinforcement plate 106 of solar energy capture device 100. Reinforcement plate 106 can include a mounting surface 108. Mounting surface 108 is securely coupled to back surface 102 of device 100 using any suitable adhesive or any suitable fasteners. A pair of opposing front and back walls 112 and a pair of opposing side walls 114 extend perpendicularly from mounting surface 108. Front and back walls 112 and side walls 114 define a space that closely corresponds to the shape of base portion 336 of upper yoke 304. Accordingly, base portion 336 can be seated in the space defined by front and back walls 112 and side walls 114. Upper yoke 304 can be secured to reinforcement plate 106 by fasteners extending through front and back walls 112 and side walls 114 into base portion 336 of upper yoke 304 or by any other suitable means of attaching yoke 304 to reinforcement plate 106.
In one embodiment, as shown, for example, in
With reference to
In embodiments using linear actuators having variable length members that cannot withstand compressive forces, for example, cables 404, apparatus 10 can also include a return mechanism that prevents unwanted rotation of object 100 about pitch axis PA toward the variable length member. The return mechanism can be any device capable of applying a force (for example, tension or torsion springs, elastic chords, or linear actuators) or a counter weight (for example, the weight of object 100 or a separate weight coupled to joint 300 below pitch axis PA). In one embodiment, the return mechanism can be the weight of solar energy capture device 100 below pitch axis PA as determined by the location at which joint 300 couples to solar energy capture device 100. For example, as shown in
In some embodiments, the majority of the weight attributed to linear actuators 400a and 400b can be located relatively low on apparatus 10, for example, at the base portion of frame 200. The low center of mass attributed to linear actuators 400a and 400b may allow frame 200 to be lighter, especially at the top, which may decrease the fabrication costs of frame 200 and allow for favorable scaling with increasing the size of object 100.
Apparatus 10 may further include a control unit 500 (not shown in
To rotate solar energy capture device 100 about roll axis RA, control unit 500 differentially actuates linear actuators 400a and 400b so that one motor 402 spins in a direction that causes its respective cable 404 to be spooled (decreasing the length of the variable length member), and/or so that the other motor 402 spins in a direction that causes its respective cable 404 to be released (increasing the length of the variable length member). For example, as cable 404 of linear actuator 400a is spooled and cable 404 of linear actuator 400b is released, solar energy capture device 100 rotates about roll axis RA towards the left of apparatus 10. Conversely, as cable 404 of linear actuator 400a is released and cable 404 of linear actuator 400b is spooled, solar energy capture device 100 rotates about roll axis RA towards the right of apparatus 10.
Accordingly, the pitch angle and the roll angle of solar energy capture device 100 can be changed by a combination of collectively and/or differentially actuating linear actuators 400a and 400b.
In some embodiments in which solar energy capture device 100 is a mirror assembly 100 for a thermal system, the mirror assembly may include a mirror structure particularly adapted for edge actuation provided by embodiments of the present invention. In one embodiment, linear actuators 400a and 400b may be coupled to the solar energy capture device 100 at points more proximate to the edge of the mirror structure than the center point of the mirror structure. This configuration may provide an increased lever arm that may increase the effective actuator force (i.e., torque) on the mirror. In such an embodiment, the mirror structure may be adapted to have additional strength and stiffness proximate to its edges to accommodate edge actuation without breaking or defocusing. In some embodiments in which the mirror assembly is mounted to universal joint 300, the attachment may be provided such that the loading around the reinforcement plate 106 is symmetric. In this manner, joint 300 will not pivot on its own absent actuation forces from linear actuators 400a and 400b. In such an embodiment, the stiffness of the mirror structure may be less at the joint attachment location (e.g., at reinforcement plate 106) than at the edges of the mirror structure. In contrast, a center actuated mirror must be very strong around the joint mount location to avoid stress concentration at the edge of the bracket. Accordingly, in some embodiments of the present invention, the mirror structure may be thicker at a point proximate its edge than at a point proximate the joint attachment location to provide effective edge actuation.
As shown in
In another embodiment, joint 300 may be a ball and socket joint. In this embodiment, joint 300 includes an arm extending from apex 226. The front portion of the arm defines a ball or spherical surface. Joint 300 further comprises reinforcement plate 314 having one side coupled to solar energy capture device 100. The other side of reinforcement plate 314 defines a socket that has a shape that corresponds to the ball defined by arm 310. The socket captures the ball of the arm, allowing plate 314 and, thus, solar energy capture device 100 to rotate relative to the arm and frame 200. Alternatively, the arm can define a socket that captures a ball defined by reinforcement plate 314.
As illustrated in
As shown in
As illustrated in
In some embodiments having a square or rectangular object 100, object 100 can be coupled to joint 300 and frame 200 in an orthogonal configuration as shown in FIGS. 2 and 4-6 or a diamond configuration as shown in
In one embodiment, apparatus 10 can include a third linear actuator. The third linear actuator can be coupled to object 100 at a point below pitch axis PA. Accordingly, the third linear actuator can function as the return mechanism.
In an embodiment having joint 300 that includes a horizontal rotating member 316 and a vertical rotating member 318, linear actuators 400a and 400b can be replaced with a motor embedded within or operatively connected to horizontal rotating member 316, and a motor embedded within or operatively connected to vertical rotating member 318. Activation of the motor connected to the horizontal rotating member 316 causes object 100 to rotate about pitch axis PA, and activation of the motor connected to the vertical rotating member 318 causes object 100 to rotate about roll axis RA.
In step 1100, the current position of the sun is determined. For example, in one embodiment, the position of the sun is determined by known orbital patterns determined by date. As will be appreciated, the current position of the sun may be determined by one or more data elements including, but not limited to, date, time, and geographic location (e.g., latitude and longitude coordinates). In another embodiment, the position of the sun is determined by using a sensor.
Using the current position of the sun determined at step 1100, a desired orientation of the solar energy capture device is determined at step 1200. For example, if solar energy capture device 100 is a mirror assembly for a thermal system, the desired orientation can be one that positions the mirror assembly so that the reflected light is focused on a receiver. If solar energy capture device 100 is a photovoltaic panel, the desired orientation can be, for example, a position that orients the photovoltaic panel to be perpendicular to the incident light from the sun.
At step 1300, solar energy capture device 100 is moved to the determined desired position by collectively actuating the first and second actuators to rotate the mirror assembly about a pitch axis and by differentially actuating the first and second actuators to rotate the mirror assembly about a roll axis. Consequently, solar energy capture device 100 can be positioned at an orientation having a desired pitch angle and roll angle.
In one embodiment, control unit 500 can perform steps 1000, 1100, and 1200, and control the actuation in step 1300. In some embodiments, the method is repeated after a predetermined time interval, for example, every thirty minutes, every hour, every other hour, or any other suitable time interval. In some embodiments, positioning of solar energy capture device 100 is continuously updated in real-time.
In another embodiment, instead of determining an absolute desired orientation from the current position of the sun, for example, a desired rate and direction of orientation change of the device 100 can be determined. Accordingly, knowing the geometry of apparatus 10, control unit 500 can be programmed to move device 100 at the desired rate and direction by controlling the length and rate of change of the variable length member of each linear actuator 400.
The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.
The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. For example, although the figures illustrate the object 100 as a solar energy capture device, apparatus 10 can be adapted to position other objects such as communication antennas, weapon platforms, and directed-energy appliances, for example. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.
It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance. The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
