FIELD OF THE INVENTION
The present invention relates generally to support frame assemblies for solar related devices, and more particularly to a support frame assembly for supporting a solar device and method of forming a support frame assembly to support a solar device.
BACKGROUND OF THE INVENTION
As solar energy devices are now being required to satisfy ever-larger energy requirements, they necessarily become physically larger. In some devices, the aggregate surface of the solar device being supported by the support structure may typically approach hundreds of square meters. Consequently, a reliable support structure for large solar devices (e.g., mirrors or photovoltaic modules) is critical to ensure excellent performance in varying atmospheric conditions and to guard against breakage of such devices. The weight of the support structure itself, and that of the attached solar devices along with wind loads and/or snow loads, can cause significant loads on the support structure.
Such solar devices requiring reliable support structures may include solar tracker devices and/or heliostats. A solar tracker device is a generic term for devices that orient various payloads toward the sun. Such payloads can be photovoltaic panels, reflectors, lenses or other optical devices (all hereinafter referred to as “mirrors” or “mirror elements”). A heliostat is a device that includes a plane mirror which turns to compensate for the sun's movement so as to keep reflecting sunlight toward a predetermined target.
In photovoltaic (PV) applications, solar trackers are typically used to minimize the angle of incidence between the incoming light and a photovoltaic panel. This increases the amount of energy produced from a fixed amount of installed power generating capacity. In concentrated photovoltaic (CPV) and concentrated solar thermal (CSP) applications, solar trackers are typically used to enable the optical components in the CPV and CSP systems. The optics in concentrated solar applications accept the direct component of sunlight and therefore must be oriented appropriately to collect energy. As such, tracking systems are found in virtually all concentrator applications because such systems do not produce energy unless oriented closely toward the sun.
For heliostats, the target may be a physical object, distant from the heliostat, or a direction in space. To reflect the sunlight, the reflective surface of the mirror is kept perpendicular to the bisector of the angle between the directions of the sun and the target as seen from the mirror. In almost every case, the target is a solar power generator which is held stationary relative to the heliostat, so the sunlight is reflected in a fixed direction. Most heliostats are used for the production of concentrated solar power, usually to generate electricity.
Many known solar devices rely on steel fabrications and weldments or aluminum extrusions configured and joined together using techniques developed in the building construction industry. Such techniques require pre-assembly and transportation of large frame sections, often to locations that are difficult to access, or they require labor intensive assembly of components on-site, often under unfavorable conditions.
A need exists for a simplified support system and method of construction which overcomes at least some of the limitations associated with the prior art.
SUMMARY OF THE INVENTION
According to at least one aspect of the present invention, a support frame assembly for supporting a solar device is provided. The support frame assembly includes at least one support arm assembly with at least two rails at least partially spaced from one another and converging towards one another from a first end to a second end. At least two web structures are spaced from one another and extend between the first and second rails with each web structure extending between and being attached to the at least two rails to interconnect the rails. At least one of the web structures has a base attached to one of the rails and at least two legs extending to the other of the rails and an opening between the legs. The web structures can be easily adapted to support arm assemblies having various shapes, sizes and designs. The web structures also allow for less strict tolerances between the components of the support frame assembly and for reduced assembly time and cost as compared to other known support frame assemblies.
According to another aspect of the invention, at least one of the web structures is shaped and sized to at least partially nest within the opening of another of the web structures. The nesting relationship of the web structures allows the components of the support frame assembly to be more efficiently shaped and shipped to an assembly location. Additionally, the nesting relationship allows multiple web structures to be stamped at one time from a single blank with very little material waste.
According to yet another aspect of the invention, the web structures are formed of a different, lighter material than the rails. Thus, the mass of the support arm assemblies may be reduced without compromising their structural integrity.
BRIEF DESCRIPTION OF THE DRAWINGS
Exemplary embodiments of the instant invention will now be described in conjunction with the following drawings, wherein like reference numerals refer to similar or identical parts throughout the several views, in which:
FIG. 1 is a perspective view showing a known support frame assembly for a trough-shaped solar concentrator assembly;
FIG. 2 is a perspective and elevation view of a first exemplary support frame assembly constructed according to one aspect of the present invention and supporting an array of mirror elements;
FIG. 3 is a side view of a second exemplary support frame assembly;
FIG. 4
a is a side view of a pair of support arm assemblies of the first exemplary support frame assembly;
FIG. 4
b is a side view of one of the support arm assemblies of the first exemplary support frame assembly;
FIG. 5 is a front elevation view of a plurality of web structures nested together after being stamped from a single blank;
FIG. 6 shows a cross-sectional profile of the first rail of a support arm assembly of the first exemplary support frame assembly and showing an adjustable fastener attaching the first rail to a mirror attachment bracket;
FIG. 7
a is a cross-sectional view of a pair of rails of a support arm assembly of the first exemplary support frame assembly interconnected to one another through a web structure and wherein the rails are welded to the web structure;
FIG. 7
b is a cross-sectional view of a plurality of rails of a support arm assembly of the first exemplary support frame assembly interconnected to one another through a web structure and wherein the rails are attached to the web structure through rivets;
FIG. 8 shows a perspective and elevation view of a support arm assembly of the second exemplary support frame assembly;
FIG. 9 is a perspective view of mirror elements mounted to the support arm assembly of the first exemplary support frame assembly;
FIG. 10 is a partial perspective view of the first rail of one of the support arm assemblies of the first exemplary support frame assembly attached to a torque tube.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
The following description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the embodiments disclosed, but is to be accorded the widest scope consistent with the principles and features disclosed herein.
In order to facilitate a better understanding of the features that are present in at least some of the embodiments of the present invention, one known type of support frame assembly 100 is described herein below, with reference to FIG. 1. The known support frame assembly 100 includes a parabolic, generally trough-shaped array of mirror elements 102 for reflecting solar rays to a solar power generator (not shown). The support frame assembly 100 includes a plurality of support arms, each of which includes an upper tube 104 and a lower tube 106 which are connected to an elongated central support element, or a torque tube 110. In particular, the upper tube 104 is connected to torque tube 110 via an upper structure-attachment bracket (not shown), and the lower tube 106 is connected to torque tube 110 via lower structure-attachment bracket 112. The upper and lower tubes 104, 106 are interconnected with one another via a plurality of lacing elements 108 which are arranged in a zig-zag pattern. The mirror elements 102 of the array are attached to and supported by the support arms via a plurality of mirror-attachment brackets 114, which are mounted to the upper tube 104 at predetermined locations along the length thereof. A torque plate 116 is provided at each end of the torque tube 110 for transferring rotational motion from a drive mechanism (not shown) to the torque tube 110 to rotate the support frame assembly 100 about a longitudinal axis which extends along the length of the torque tube 110. In this fashion, the parabolic trough-shaped solar array may be dynamically reoriented to track the movement of the sun across the sky, thereby maximizing the amount of solar rays reflected to the solar power generator.
In the known support frame assembly 100 of FIG. 1, the upper tubes 104, the lower tubes 106, and each of the lacing elements 108 are individually formed tubular structures. The shapes of the upper and lower tubes 104, 106 are typically created either by bending sections of a tubing that has been cut to length or by welding together shorter tubular sections with angled ends. Each of the individual lacing elements 108 must be cut to a specified length within very close tolerances and must be positioned precisely during the assembly of assembling the supports arms. Very close tolerances and precise positioning of the lacing elements 108 are necessary since each lacing element 108 must be welded at one end to a predetermined location along the upper tube 104 and at the other end to a predetermined location along the lower tube 106. Even relatively small cutting or positioning errors can result in difficulty during the assembly process and could compromise the structural integrity of the support arms. Further, since a large number of individual tubular structures are welded together to form the support arms, the process of assembling the known support frame assembly 100 of FIG. 1 winds up being very labor-intensive.
When a trough-shaped solar array is to be installed using the known support frame assembly 100 of FIG. 1, a plurality of the support arms are typically preassembled in a factory setting and then transported to the installation site or they must be assembled at the installation site, which could be under adverse working conditions. In either case, the resulting support frame assembly 100 is excessively heavy and often provides unsatisfactory rigidity. In addition, the support frame assembly 100 cannot be easily modified for supporting solar arrays of varying sizes and/or shapes since any such modification involves a redesigning a large number of components in order to ensure that all of the components fit together sufficiently closely.
Referring now to FIG. 2, a support frame assembly 200 constructed according to one aspect of the invention is generally shown. The exemplary support frame assembly 200 is shown supporting a generally flat (or planar) array of mirror elements 202 for reflecting solar rays to a solar power generator (not shown). However, it should be appreciated that the solar device could be an array of photovoltaic panels or any desirably type of solar collector or reflector. The support frame assembly 200 is preferably part of a larger sun tracker or heliostat assembly but could alternately be non-movably mounted, if desired.
The exemplary support frame assembly 200 includes an elongated central support element, or a torque tube 204, extending along an axis and a plurality of support arm assemblies 206 extending generally perpendicularly outwardly from the torque tube 204. As best shown in FIG. 4a, each of the support arm assemblies 206 includes a first rail 208 and a second rail 210 interconnected by a plurality of web structures 212a-d. Referring back to FIG. 2, the first and second rails 206, 208 each extend from a first end which is coupled to the torque tube 204, to a distal second end. In this exemplary embodiment, the first and second rails 206, 208 converge towards one another from the first ends to the second ends. Thus, the first and second rails 206, 208 extend in non-parallel relationship with one another with the second ends being closer to one another than the first ends.
The first rails 206 of the support arm assemblies 206 are each attached to the torque tube 204 via an upper structure attachment bracket 214 (best shown in FIG. 10), and the second rails 208 of the support arm assemblies 206 are each attached to the torque tube 204 via a lower structure attachment bracket 216. The structure attachment brackets 214, 216 could be fastened to the torque tube 204 and to the respective rail 208, 210 through any suitable process including, for example, fasteners, riveting, spot welding, Tox® joining, etc. The upper and lower structure attachment brackets bracket 214, 216 may include either holes or slots depending on the functionality required for each application. In this exemplary embodiment, each of the upper structure attachment brackets 214 has a hole for receiving fasteners, such as bolts, which also extends through the brackets 214. It may be desirable to fabricate the upper and lower structure attachment brackets 214, 216 with slots (not shown) to allow for adjustments of the orientations of the support arm assemblies 206 relative to the torque tube 204 by adjusting the position of the fasteners within the slots.
Referring now to FIG. 9, in this exemplary embodiment, a plurality of mirror elements 202 are shown in attachment with one of the first rails 206 of one of the support arm assemblies 206 via a plurality of mirror attachment brackets 218 disposed underneath the mirror elements 202 and a plurality of adjustable fasteners 220 located at predetermined locations along the lengths of the first rails 206. As shown in FIG. 6, each of the exemplary fasteners 220 includes a threaded rod 222 extending through the upper surface of the first rail 208 and through a hole in a mirror attachment bracket 218. The first rail 204 includes an aperture 224 to permit access to a nut 226 (or any other fastener) which is threaded onto the end of the threaded rod 222. Another nut 226 is disposed within the mirror attachment bracket 218, and at least one nut 226 is disposed between the mirror attachment bracket and the first rail 206. In the exemplary fastener 220, adjustment of the positions of the nuts 226 along the threaded rods 222 allows for the gap (i.e., the vertical distance) between the mirror element 222 and the first rail 206 to be adjusted. Thus, the mirror elements 202 may be mounted at varying distances above the first rail 208 relative to one another. This adjustment feature may be useful depending on the functionality of the mirror elements 202 including, without limitation, whether a partial parabolic shape of the solar array is desirable and also to accommodate dimensional variations in the mirror elements 202. It should be appreciated that the mirror elements 202 (or other elements of the solar device) could alternately be attached to the support arms 206 through any suitable adjustable or non-adjustable process including, for example, other types of fasteners, adhesives, brazing, welding, etc. The mirror attachment brackets 218 could also be fixed to the mirror elements 202 through any suitable process, and any desirable number of mirror attachment brackets 218 may be attached to each support arm assembly 206. The number of mirror attachment brackets 218 may depend, at least partially upon among other things, the length of the first rail 204 and the size and mass of the solar device being supported, etc.
Referring now to the cross-sectional views of FIGS. 7a and 7b, each of the exemplary first and second rails 208, 210 is shaped to present a generally rectangular opening with a pair of flanges 228 extending downwardly therefrom in spaced and parallel relationship with one another and extending substantially the entire length of the first and second rails 208, 210. The spacing of the flanges 228 from one another presents an open channel for receiving the web structures 212a-d. In FIG. 7a, the web structure 212a is attached to the flanges 228 via a weld 229a which fixedly secures the sides of the web structure 229a to the ends of the flanges 228. In contrast, the web structure 212a of FIG. 7b is attached to the flanges 228 via a rivet 229b which extends through the flanges 228 and the web structure 212a. It should be appreciated that the web structures 212a-d could alternately be attached to the first and second rails 208, 210 through any suitable process including, for example, other types of welding, other types of fasteners, brazing, adhesives, riveting, press metal joining (such as toggle locking or Tox® joining), etc. It should be appreciated that the first and second rails 208, 210 could have any desirable cross-sectional profile including, without limitation, a generally triangular, rectangular or circular shape. The shape and dimensions of each rail's profile are preferably selected according to the specific requirements of a particular application. The first and second rails 208, 210 are preferably shaped through a roll forming process. However, it should be appreciated that the rails 208, 210 could alternately be shaped through an extrusion, stamping, machining or any suitable process.
Referring now to FIG. 5, each of the web structures 212a-d is generally U or chevron shaped with a base 230a-d in engagement with one of the rails 208, 210 and a pair of legs 232a-d extending to the other of the rails 208, 210. The legs 232a-d of the web structures 212a-d diverge away from one another as they extend from their respective bases 230a-d, and whichever leg 232a-d is to be positioned closer to the torque tube 204 is longer than the other leg to compensate for the greater distance between the first and second rails 206, 208 at this location. The particular shape and size of each of the web structures 212a-d is determined based on the requirements of a particular application including, without limitation, such considerations as strength, load, wind, and cost.
As also shown in FIG. 5, each of the web structures 212a-d of the support frame of FIG. 2 has an opening between the legs 232a-d. Each of the smaller web structures 212a-c is shaped and sized to nest, at least partially, within the opening of the larger web structures 212b-d. This provides for manufacturing advantages as well as cost savings since these web structures 212a-d can be stamped from a single blank in a single press with little wasted material. The web structures 212a-d can also be packaged efficiently for transportation before installation within one of the support arm assemblies 206. By way of a specific and non-limiting example, steel rule dies are used to stamp out the plurality of web structures 212a-d in a single press. It should be appreciated that the web structures 212a-d could have any desirable shape with at least two legs and an opening including, without limitation, a square, triangular, or W shape.
The torque tube 204 is preferably mounted to a drive mechanism (not shown) for rotating the support frame assembly 200. In this fashion, mirror elements 202 may be re-oriented to follow, or track, the movement of the sun across the sky, thereby maximizing the amount of solar rays reflected to a solar power generator (now shown). However, as discussed above, the support frame assembly 200 could alternately be non-movably mounted.
According to at least one embodiment, the first and second rails 208, 210 and the plurality of web structures 212a-d are fabricated from the same material, such as for instance high-strength steel. In this case, the plurality of web structures 212a-d are preferably attached to the first and second rails 208, 210, respectively, by one of welding, riveting or Tox® joining or any other suitable coupling mechanism.
According to another embodiment, the first and second rails 208, 210 and the plurality of web structures 212a-d are fabricated from different materials. For instance, the first and second rails 208, 210 are fabricated from high-strength steel and the web structures 212a-d is fabricated from aluminum or an alloy thereof, or from a composite material, etc. In this embodiment, the use of aluminum for the web structures 212a-d will provide less overall weight to the support frame assembly 200. Some examples of composite materials which may be suitable include steel/plastic/steel sandwich materials or steel/paper/steel sandwich materials. Depending on the specific combination of materials that is used, the plurality of web structures 212a-d may be attached to the first and second rails 208, 210 through welding, riveting, Tox® joining or any other suitable coupling mechanism.
Another aspect of the present invention provides for a process of fabricating a support frame assembly 200. The exemplary process includes roll forming a torque tube 204, a plurality of first rails 208 and a plurality of second rails 210. A plurality of web structures 212a-d are then formed through a single stamping process. The web structures 212a-d are formed with a base 230a-d and a pair of legs 232a-d to present an opening. During the stamping process, the smaller web structures 212a-c are at least partially formed in nesting relationship with the respective larger web structures 212b-d. The first and second rails 208, 210 are then positioned in a predetermined configuration relative to one another, e.g. converging towards one another from first ends to second ends. Next, the web structures 212a-d are attached between the first and second rails 208, 210 to define a plurality of support arm assemblies 206. The support arm assemblies 206 are then attached to the torque tube 204 through a plurality of upper and lower structure attachment brackets 214, 216. The assembly of the support arm assemblies 206 and the attachment of the support arm assemblies 206 to the torque tube 204 can either be done in a factory setting or in the field at an installation location.
Referring now to FIG. 3, an alternative exemplary embodiment of the support frame assembly 300 is generally shown. In this embodiment, the first and second rails 308, 310 extend in generally parallel relationship with one another. This embodiment also includes a torque tube 304 and plurality of support arm assemblies 306 with web structures 312a-d and fasteners 320, similar to the exemplary embodiment. It should be appreciated that the shape of the second rail may differ from the exemplary embodiment depending on a number of factors including, for example, strength, cost, functionality, etc. For example, the second rail could alternately have an arcuate shape.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings and may be practiced otherwise than as specifically described while within the scope of the appended claims.
Patent Application
20140117190
