Patent Application
20110232715
The application relates generally to a photovoltaic array. More particularly, it relates to a minimally penetrating photovoltaic assembly for use with a sloped roof.
Currently, photovoltaic (PV) modules can be secured to roofs with rack systems that include vertical stanchions and lateral rails. In particular, the lateral rails are attached to the stanchions, which are typically several inches off the roof, and the PV modules are attached to the rails. Installations of PV modules using such traditional rack systems may be difficult because, for example, the installations can be very labor intensive due to the deficient designs of the stanchions and rails. Additionally, the stanchions may possibly penetrate deeply into the roof and/or in a large number of locations. For example, relatively large holes are often pre-drilled through the roofing material to accommodate the mounting hardware. Because of the size of these large holes, and/or the large number of penetrations, it is often difficult to tell if adequate waterproofing has been achieved. It should be appreciated that many of these traditional PV rack systems may often include one or more of the above-described drawbacks or other drawbacks not mentioned.
An assembly includes an interconnected array of photovoltaic (PV) modules, where each of the PV modules is defined in part by a module outer perimeter portion. The array is defined in part by an outer perimeter portion including an upper edge portion, side edge portions, and a lower edge portion. The interconnected array is configured to be secured to a sloped roof along at least one of the upper or lower edge portion of the array. The assembly further includes interlocking features along the module outer perimeter portion which distribute uplift forces to adjacent modules. Additionally included is at least one wind deflector located along the lower edge of the array and one or more non-penetrating base feet are configured to be disposed on the sloped roof, where the base feet supports at least a portion of the interconnected array of PV modules. Wind uplift forces on the array may be resisted through distribution of forces within the array, pressure equalization treatment, and/or aerodynamic treatment of the array.
A method includes mounting two or more PV modules on a sloped roof with non- penetrating roof mounting structure. The two or more PV modules are interconnected into an array of PV modules and at least a portion of an upper edge portion of the array is configured to be secured with the sloped roof. Additionally, at least one wind deflector is coupled with at least a portion of a lower edge portion of the array. The method further includes resisting wind uplift forces on the array through distribution of forces within the array, pressure equalization treatment, and/or aerodynamic treatment of the array.
These and other embodiments, aspects, advantages, and features will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art by reference to the following description of embodiments of the invention and referenced drawings or by practice of the embodiments. The aspects, advantages, and features are realized and attained by means of the instrumentalities, procedures, and combinations particularly pointed out in the appended claims and their equivalents.
Embodiments of the invention may be best understood by referring to the following description and accompanying drawings which illustrate such embodiments. In the drawings:
The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the present photovoltaic assemblies and methods may be practiced. These embodiments, which are also referred to herein as “examples,” are described in enough detail to enable those skilled in the art to practice the present photovoltaic assemblies and methods. The embodiments may be combined, other embodiments may be utilized or structural or logical changes may be made without departing from the scope of the present photovoltaic assemblies and methods. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present photovoltaic assemblies and methods is defined by the appended claims and their legal equivalents.
In this document, the terms “a” or “an” are used to include one or more than one, and the term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. In addition, it is to be understood that the phraseology or terminology employed herein, and not otherwise defined, is for the purpose of description only and not of limitation.
An assembly includes an interconnected array (or “array”) of photovoltaic (PV) modules, interlocking features, at least one wind deflector, and one or more non-penetrating base feet. In an option, the interconnected array, wind deflector, and base feet are collectively lightweight such that an average load on the roof does not exceed about 10 lb/sq. feet. For example, an average load of the lightweight structure is between about 2 lb/sq. feet and about 5 lb/sq. feet. In another example, an average load of the lightweight structure is about 2.5 lb/sq. feet. As used herein, the term “about” means that the specified dimension or parameter may be varied within an acceptable tolerance for a given design or application. In some embodiments, for example, an acceptable tolerance for a parameter is ±10%.
The array 100 of PV modules 110 are interconnected to one another with interlocking features 130, as depicted in
The array 100 of PV modules 110 may be subjected to wind uplift forces. In an option, wind uplift forces on the array 100 are resisted in one or more different manners. For instance, a majority of wind uplift forces may be resisted through distribution of forces within the array 100, pressure equalization treatment, and/or aerodynamic treatment of the array 100.
The distribution of forces within the array 100 includes, but is not limited to, the mechanical and structural interconnections between the individual PV modules 110. Pressure equalization treatment includes methods and/or structure which equalize pressure between the array 100 and the sloped roof 120 and above the array 100. For example, the array 100 can include air gaps between various components so that air can flow through it. Examples of such gaps include one or more gaps located between the individual PV modules 110, a perimeter gap located between one or more PV modules 110 and an outer deflector, and a gap located between the deflector and the lower edge of the array 100. In another option, pressure equalization is enhanced by promoting flow of air under the PV modules 110 while also limiting the volume of air that can exist in these regions. In a further option, the deflector is a wind deflector, which may be porous to allow for convective air flow between the array 100 and the sloped roof 120 and deflecting wind gusts above the array 100.
The aerodynamic treatment also assists in resisting a majority of wind uplift forces on the array 100. The aerodynamic treatment includes, but is not limited to wind deflectors 109, such as upper wind deflectors, side wind deflectors, or lower wind deflectors. The wind deflectors can be placed at any relatively large entry points to an underside of the array 100 to prevent wind penetration into the entry point. In an option, the wind deflectors are as tall as the tallest adjacent components in the array 100 to minimize drag forces on the array 100. In an option, the wind deflectors are sloped at an angle to reduce drag forces on the deflector. In a further option, a curb section is utilized to provide improved aerodynamic performance and aesthetics may also include compatible features so that the PV modules 110 can lock into the curb directly, for example either using a rotating or sliding motion. In a further option, at least one wind deflector is located along the lower edge of the array 100 so as to minimize aerodynamic drag and uplift on the array 100.
Still referring to
The one or more base feet 160 are configured to be disposed, for example, in a non-penetrating and/or non-ballasted manner on the sloped roof 120, and the one or more base feet 160 support at least a portion of the interconnected array 100 of PV modules 110. In a further option, the base feet 160 comprise a majority of supporting structures of the array 100, where the base feet 160 include 50% or greater of the supporting structures of the array 100, not including the sloped roof 120. An adhesive 167 is optionally disposed between the base feet 160 and a roof surface of the sloped roof 120. The adhesive 167, such as a temporary adhesive, would allow for the base feet 160 to be laid out, without the base feet 160 sliding down the sloped roof 120 or without the base feet 160 moving when a PV module 110 is slid into place on top of the base feet 160. Once installed, the adhesive 167 may not be necessary since the weight of the PV modules 110, anchors on adjacent PV modules 110, or other locking mechanism would keep the base feet 160 in position.
The assembly including the array 100 includes interlocking features 130, which is depicted in
In an example, as depicted in
In an example as shown in
In an option, a locking tab 135 is further included to prevent the PV module 110 from rotating back out of position as well as a bias member 137, such as a molded-in spring feature, to provide positive engagement in the joint between the adjacent PV modules 110. These features also provide positive feedback of proper engagement of the projection attachment feature 134. This type of feature may also be advantageous because bending down to engage PV modules 110 on a sloped roof 120 laterally can be difficult. Thee embodiments uses a more natural motion during placement that can be done from a standing position, and the features to help correct slight misalignment.
In another option, as shown in
Returning to
To ease installation, the bottom of the base feet 160 could be coated with a glue or adhesive 167. The adhesive 167 would allow for the base feet 160 to be laid out, without the base feet 160 sliding down a sloped roof 120 or without the base feet 160 moving when a PV module 110 is slid into place on top of it. Once installed, the weight of the PV modules 110, the anchors on adjacent PV modules 110, or a locking mechanism would keep the base feet 160 in place. The adhesive 167 would no longer be necessary in maintaining the structural integrity of the array 100 and therefore would not need to be weather resistant.
The PV module 110′ is shift in the direction shown as 127, and a cut out in adjacent PV module 110″ allows the PV module 110′ to be shifted further for removal. As PV module 110′ is slid, the interlocking features, such as the projection attachment features and recessed attachment features, can be disengaged from one another. As shown in
Referring to
The assembly further includes one or more penetrating members 180 coupled with the sloped roof 120. The penetrating members 180 can be placed along a rafter 122 under the roof surface for increased hold-down form, or attached to the roof decking independent of rafter location. This allows for positioning of the penetrating members 180 to be independent of the placement of the PV modules 110. In a further option, the one or more penetrating members 180 are offset from the module outer perimeter portion. In another option, the penetrating members 180 are disposed within a footprint of the array 100, along the outer perimeter portion of the array 100, or combinations thereof. In yet another option, the penetrating members 180 are coupled with the sloped roof 120 and the array 100, for example with at least one tie down.
The tie down, such as a flexible tie down, is coupled with the one or more penetrating members 180, and further with a portion of the array 100, such as a PV module 110, at an attachment point. The tie down can go through slots in a frame of the PV module 110, allowing for attachment, or detachment from the PV module 110. The tie down can be a cable, wire, conductive or non-conductive element. An optional tie down tightening member 186 can also be included. For example, the tie down is pulled though slots and then into a screw, which when turned takes up the remainder of slack in the tie down. Since the location of the penetrating members 180 is independent of the placement of the PV modules 110, the tie down 182 is not necessarily perpendicular relative to the surface of the sloped roof 120. For instance, in an option, an angle 184 formed between the tie down 182 and the sloped roof 120 is obtuse.
The penetrating members 180 may, for example, be placed with a much larger spacing tolerance than is typical of those used in PV mounting systems, while still providing uplift resistance needed to keep the array 100 intact. The embodiments may, for example, provide a low cost method of attaching some points within an array 100 to the sloped roof 120 to prevent upward wind forces from lifting PV modules 110 from the sloped roof 120 or overstressing inter-module connections. By using a flexible tie down, such as a cable or wire, the resulting force on the joiner is only slightly higher than that of the upward wind force, but the low-cost attribute of non-precision alignment of the fixture is maintained.
Methods of installing and/or uninstalling the various arrays 100, PV modules 110 and the various embodiments and options discussed and shown are further discussed herein. The method includes mounting two or more PV modules 110 on a sloped roof 120 with minimally penetrating and lightweight roof mounting structure. What is meant by minimally penetrating is that the penetrating structures are not the primary structures used to hold the array 100 to the sloped roof 120. Other mechanisms, such as pressure management, or wind uplift management are used to keep the array 100 on the sloped roof 120. The assembly may also be lightweight, as discussed above. In an option, mounting the PV modules 110 includes disposing the PV modules 110 in a horizontal row of PV modules 110, and disposing an interlock between adjacent PV modules 110. To remove a PV module 110, the interlock is removed and a first PV module is slid relative to the adjacent PV module. The method includes securing at least a portion of an upper edge portion of the array 100 with the sloped roof 120.
The method further includes interconnecting the two or more PV modules 110 into an array 100 of PV modules 110 which planarize adjacent module edge portions. In an option, interconnecting the PV modules 110 include inserting a projection attachment feature of a first PV module into a recessed attachment feature of a second PV module and rotating the first PV module relative to the second PV module. The method further optionally includes removing at least one individual PV module 110 from an array 100 of interconnected PV modules 110 without removing surrounding PV modules 110. In an option, removing the at least one individual PV module 110 includes sliding a first PV module relative to a second PV module.
Several options for the method are as follows. For instance, the method includes locking a first PV module relative to a second PV module, for instance by rotating the first PV module relative to the second PV module. In a further option, the method includes disposing adhesive 167 between the roof mounting structure and a surface of the sloped roof 120, or a height of the roof mounting structure. In yet another option, the method includes securing the array 100 to the sloped roof 120 with a tie down, such as a tie down cable, including securing the tie down cable with the array 100 and a penetrating member coupled with the sloped roof 120.
The disclosed embodiments discuss various methods of interconnecting and securing PV modules 110 to sloped roofs 120. These methods incorporate pressure equalization effects to, for example, reduce wind loading. The embodiments may also provide a reduction in the number and penetrations into the sloped roof 120, and create the ability to remove an individual PV module 110 for maintenance or replacement without disturbing surrounding PV modules 110. The embodiments further allow for both portrait and landscape module orientation. Although developed with sloped roof applications in mind, many of these concepts are equally applicable to flat or low-slope roofs.
References in the specification 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.
It is to be understood that the above description is intended to be illustrative, and not restrictive. For instance, any of the aforementioned examples may be used individually or with any of the other examples. Many other embodiments may be apparent to those of skill in the art upon reviewing the above description. The scope of the present PV assemblies and methods should, therefore, be determined with reference to the appended claims, along with the full scope of legal equivalents to which such claims are entitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, assembly, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of such claim.
The Abstract of the Disclosure is provided to comply with 37 C.F.R. §1.72(b), requiring an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, various features may be grouped together to streamline the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter may lie in less than all features of a single disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.
The invention described herein was made with government support under contract number DE-FC36-07GO17043 awarded by the United States Department of Energy. The United States Government may have certain rights in the invention.
