The present disclosure relates to ground mount-type solar energy collectors. More particularly, it relates to photovoltaic systems with solar tracking features.
Solar photovoltaic arrays are used for a variety of purposes, including as a utility interactive power system, a power supply for a remote or un-manned site, a cellular phone switch-site power supply, or a village power supply. These arrays can have a capacity from a few kilowatts to a hundred kilowatts or more, and are typically installed where there is a reasonably flat area with exposure to the sun for significant portions of the day.
In general terms, solar photovoltaic systems (or simply “photovoltaic systems”) employ photovoltaic (PV) cells made of silicon or other materials to convert sunlight into electricity. The cells are packaged in a PV laminate that is generally formed as an array of crystalline or amorphous semiconductor devices electrically interconnected and encapsulated. One or more electrical conductors are carried by the PV laminate through which the solar-generated current is conducted. A single PV laminate can then be assembled to a supportive frame to form a PV module, or can be supported directly (alone or with one or more additional PV laminates) without the use of a frame. As used throughout the specification, the term “PV assembly” (or “photovoltaic assembly”) generically encompasses one or more PV laminates, or one or more PV modules, assembled to a common support structure.
Most large scale PV installations entail mounting an array of PV assemblies to the earth or ground at a location where sunlight is readily present. In order to further improve solar collection efficiency, tracking devices have been employed to keep the PV laminate surfaces in a position close to optimum with respect to the sun for significant portions of the day.
Typical solar tracking systems arrange the laminates in a common plane, with this arrangement being linked to a torque tube or arm that serves as an axis of rotation. For example,
While the above-described solar tracking techniques are well-accepted, tracking the sun requires clearance relative to ground to allow the full tracking motion, necessitating a high rotational axis and therefore high support points (i.e., the mounting structures 18, 20 of
In light of the above, a need exists for improved photovoltaic solar tracking systems.
Some aspects in accordance with principles of the present disclosure relate to a photovoltaic solar energy collection and tracking system including a photovoltaic assembly, a first mounting structure, and a second mounting structure. The photovoltaic assembly includes at least one photovoltaic cell maintained by framework in a manner defining a PV plane. The first mounting structure is mountable to a support surface and rotatably maintains the framework at a first pivot point. The second mounting structure is also mountable to the support surface, and rotatably maintains the framework at a second pivot point. In this regard, assembly of the framework to the mounting structures establishes a tracking axis passing through the first and second pivot points, with the tracking axis being non-parallel with the PV plane. With this construction, the photovoltaic assembly can be rocked or rotated about the tracking axis to follow motion of the sun relative to the earth. By forming the tracking axis as being off-parallel with the PV plane, one or both of the mounting structures can be relatively small, and therefore the system entails lower structural costs as compared to conventional designs. Further, the off-parallel tracking axis effectuates a compound angle tracking motion that may promote increased performance or efficiency over the course of a year. In some embodiments, the second mounting structure, and thus the second pivot point, is spatially arranged below a perimeter frame otherwise maintaining the photovoltaic cells. In yet other embodiments, the framework includes a reinforcement assembly forming at least one truss structure, with the second pivot point being established at an apex of the truss.
Other aspects in accordance with principles of the present disclosure relate to a method of collecting energy from the sun. The method includes providing a photovoltaic assembly including at least one photovoltaic cell maintained by framework in a manner defining a PV plane. First and second mounting structures are mounted to a support surface. The framework is pivotably mounted to the first mounting structure at a first pivot point, and to the second mounting structure at a second pivot point. In this regard, a tracking axis is established that passes through the first and second pivot points, with the tracking axis being non-parallel with the PV plane. The photovoltaic assembly is operated to collect energy from sunlight via the photovoltaic cells. Further, the photovoltaic assembly is rotated along the tracking axis to follow a motion of the sun relative to earth. In some embodiments, the support surface is ground or earth, and the mounting structures each include a poured concrete footing formed into the earth.
Yet other aspects in accordance with principles of the present disclosure relate to a solar tracking and photovoltaic support assembly including framework, a first mounting structure and a second mounting structure. The framework is configured for mountably supporting at least one photovoltaic cell in a manner establishing a major PV plane. The mounting structures are mountable to a support surface (e.g., earth or ground). The framework is pivotably assembled to the first mounting structure at a first pivot point, and to the second mounting structure at a second pivot point. A tracking axis is defined as passing through the pivot points, and is non-parallel with the PV plane. With this construction, the framework can be rocked relative to the mounting structures and about the tracking axis to follow motion of the sun relative to earth.
One construction of a photovoltaic (PV) solar energy collection and tracking system 50 in accordance with principles of the present disclosure is shown in
The PV cell(s) 54 can assume a variety of forms that may or may not be implicated by the Figures. In some constructions, the PV cell(s) 54 are formed as part of a PV laminate 55 that can have any form currently known or in the future developed that is otherwise appropriate for use as a solar photovoltaic device. Further, the system 50 can include a single, large PV laminate 55 or a plurality of PV laminates 5 combining to define a large PV laminate arrangement. In general terms, the PV laminate 55 consists of an array of the photovoltaic cells 54. A glass laminate may be placed over the photovoltaic cells for environmental protection. In some embodiments, the photovoltaic cells 54 advantageously comprise backside-contact cells such as those of the type available from SunPower Corp., of San Jose, Calif. As a point of reference, in backside-contact cells, wirings leading to external electrical circuits are coupled to a backside of the cell (i.e., the side facing away from the sun upon installation) for increased solar collection area. Backside-contact cells are also disclosed in U.S. Pat. Nos. 5,053,083 and 4,927,770, which are both incorporated herein by reference in their entirety. Other types of photovoltaic cells may also be used without detracting from the merits of the present disclosure. For example, the photovoltaic cells 54 can incorporate thin film technology, such as silicon thin films, non-silicon devices (e.g., III-V cells including GaAs, CdTe, CIGs), etc. Further, the PV laminate 55 can be bifacial.
While not shown in the Figures, additional components can be provided with each of the PV laminates 55, such as wiring or electrical components. Further, the PV laminates 55 can be mounted to or maintained by framing components apart from the framework 58. Thus, for example, one or more of the PV laminates 55 can be provided as a standalone PV module (as that term is conventionally employed) and subsequently assembled to the framework 58.
In other constructions contemplated by the present disclosure, the PV cell(s) 54 are provided in a format that may or may not include the PV laminate 55. For example, the systems of the present disclosure can include or relate to PV concentrator devices incorporating optical components such as mirrors and/or lenses (e.g., Fresnel lens) to direct and concentrate sunlight on the PV cell(s) 54.
Regardless of an exact construction, the PV cell 54 defines a PV front surface 70 and a PV rear surface 72 (referenced generally in
With the above understanding of the PV cell(s) 54 in mind, the framework 58 can assume a variety of forms, and generally serves as a support structure or base for the PV cell(s) 54 and corresponding structures (e.g., the PV laminate(s) 55, concentrator components, etc.). In some constructions, the framework 58 includes a perimeter frame 80 and a reinforcement assembly 82. The perimeter frame 80 serves to maintain the PV cell(s) 54 (and related components) in the PV plane P mentioned above, with the reinforcement assembly 82 projecting from the perimeter frame 80 below the PV plane P.
The perimeter frame 80 can form a variety of shapes, and in some configurations is rectangular. For example, and with reference to
The frame members 90-96 can assume various forms that facilitate mounting of the PV laminates 55 (or other, alternative structures associated with the PV cells 54, such as concentrator components) thereto. For example, the frame members 90-96 can be metal beams or tubes forming a lip- or shelf-type structure adapted to receive and maintain (e.g., via an adhesive) one or more edges of the PV laminates 55. In other constructions, however, the perimeter frame 80 can be formed by a more homogenous or a continuous structure or body that directly contacts or more robustly supports the rear surface 72 (
The reinforcement assembly 82 can assume a variety of configurations, and in general terms forms or provides a coupling body 110 (referenced generally) that is spaced from the perimeter frame 80 and the PV plane P and is configured for pivotable connection to the second mounting structure 62 (
In some constructions, the reinforcement assembly 82 is adapted to enhance an overall stiffness or strength of the perimeter frame 80, and includes a plurality of rods 112 combining to form one or more truss structures 114 (referenced generally). The rods 112 can be segmented or coupled to one another as first and second rod sets 116, 118. In the assembled configuration of
In addition to the rod sets 116, 118, in some constructions, the reinforcement assembly 82 further includes a shaft 120 (or two or more shafts or rods linked together along a common axis) extending between and interconnecting the rod sets 116, 118 opposite the perimeter frame 80. As described below, the shaft 120 can function as a torque tube or arm to facilitate driven movement of the PV assembly 64 as part of a solar tracking operation.
The rod sets 116, 118 can assume a variety of forms differing from those reflected in the Figures. In some embodiments, the rod sets 116, 118 are foldable relative to the perimeter frame 80 to provide a compact, shipping format of the PV assembly 64 in which the rod sets 116, 118 are retracted from the orientation shown in the Figures. The rod sets 116, 118 need not be identical, and a greater or lesser number of the rods 112 can be provided. For example, in some constructions, the reinforcement assembly 82 consists of only two or three of the rods 112 that combine to form a single truss structure 114a at which the coupling body 110 is formed or provided. In yet other embodiments, the reinforcement assembly 82 can be constructed or formed by one or more structures that do not include a rod. For example, the reinforcement assembly 82 can be a single, homogenous body projecting from the perimeter frame 80 adjacent the second end frame member 96 and terminating at the coupling body 110.
Returning to
The second mounting structure 62 also includes a footing 140 and a pier 142. Once again, the footing 140 can be a poured concrete footing, with the pier 142 rigidly maintained by, and extending from, the footing 140 and terminating at a leading end 144. A second mounting structure height H2 (identified in
With specific reference to
Construction of the solar energy collection and tracking system 50 to the support surface 66 includes constructing/mounting the mounting structures 60, 62 to or on the support surface 66 as described above, with the mounting structures 60, 62 being spaced from one another. The PV assembly 64 is then connected to the mounting structure 60, 62. With specific reference to
The above construction defines the tracking axis T as extending through the first and second pivot points 160, 162. As shown, and in contrast to conventional solar tracking designs, the tracking axis T is non-parallel relative to the PV plane P. For example, the tracking axis T and the PV plane P combine to define an included angle Δ in the range of 3°-70°; in some embodiments in the range of 5°-60°. Further, while the arrangement of
Following installation, the system 50 operates to collect and convert sunlight into electrical energy in manners conventionally found with photovoltaic applications. Further, the PV assembly 64 is maneuvered (e.g., rocked) to track the position of the sun relative to the support surface 66. As a point of reference, with the installations implicated by
Further, because the second pivot point 162 is located in highly close proximity to the support surface 66 (at the east-looking orientation), the perimeter frame 80 (e.g., the second end frame member 96) is located closer to the support surface 66 (as compared to a conventional tracking arrangement), thereby presenting a lower wind profile to the PV assembly 64. By way of comparison,
The solar energy collection and tracking systems of the present disclosure provide a marked improvement over previous designs. By establishing a tracking axis that is off of parallel relative to the PV plane, the corresponding foundation or mounting structure(s) can be reduced. Further, the tracking motion created by a positive angle rotation axis and a relative negative angle PV plane can increase the efficiency or performance over the course of a year.
Although the present disclosure has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present disclosure.
This application claims priority under 35 U.S.C. §119(e)(1) to U.S. Provisional Patent Application Serial No. 61/176,669, filed May 8, 2009, entitled “Photovoltaic Solar Collection and Tracking System”, and bearing Attorney Docket No. S0141/S812.107.101; and the entire teachings of which are incorporated herein by reference.
This invention was made with Government support under Contract No. DE-FC36-07G017043 awarded by the United States Department of Energy. The Government has certain rights in this invention.
Number | Date | Country | |
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61176669 | May 2009 | US |