Patent application title: Roof mounting bracket for photovoltaic power generation system
Ronald J. Gangemi (Grass Valley, CA, US)
IPC8 Class: AE04D1318FI
Class name: Static structures (e.g., buildings) combined with a sunlight activated device (e.g., passive solar or photoelectric)
Publication date: 2010-12-16
Patent application number: 20100313499
Multiple brackets are used together to support photovoltaic cells upon a
roof. Each bracket includes a mounting rail at an upper side and a bottom
rail at a lower side. The bottom rail of one bracket is configured to
overlap the mounting rail of another bracket. Lateral joints on each
bracket overlap each other to connect adjacent panels of photovoltaic
cells. Cell support structures are interposed between the mounting rail
and bottom rail to support a photovoltaic stack assembly thereon. Wind
clips allow the bottom rail of a higher bracket to be interconnected with
a mounting rail of a lower bracket. An undulating end piece allows
airflow to enter beneath a lowest bracket and pass up beneath the
brackets to provide cooling air for the overall system of photovoltaic
cells mounted upon the brackets. Edge flashing precludes water migration
laterally at edges of the panels.
1: A photovoltaic power generation system roof mounting system, comprising
in combination:at least two photovoltaic elements of substantially planar
form;said photovoltaic elements coupled together and adapted to convert
photonic radiation into electric power;at least two mounting brackets
including a higher mounting bracket above a lower mounting bracket, each
said mounting bracket adapted to be interposed between at least one
photovoltaic element and the roof;each said mounting bracket having a
similar form;each said mounting bracket having a mounting portion closer
to an upper side than to a lower side, said mounting portion adapted to
be coupled to the roof in fixed position relative to the roof;each said
mounting bracket having said lower side opposite said upper side;said
lower side of said higher mounting bracket adapted to fit over at least a
portion of said lower mounting bracket to define an overlapping
portion;at least one airflow pathway extending beneath said at least two
mounting brackets from said lower side of said lower mounting bracket to
said upper side of said higher mounting bracket; andsaid pathway adapted
to cool said photovoltaic elements and said mounting brackets at least
partially by natural convection.
2: The system of claim 1 wherein said system includes a series of vertically spaced overlapping mounting brackets, with said pathway extending from a lowermost one of said series to an uppermost one of said series, with said pathway being continuous along its entire path.
3: The system of claim 2 wherein each said mounting bracket includes ribs on an underside of said bracket, at least one of said ribs extending at least partially horizontally and having at least one passage being formed therein to allow airflow continuously from said lower side to said upper side beneath each said mounting bracket.
4: The system of claim 3 wherein said ribs include a plurality of vertical ribs and at least one lateral rib, substantially perpendicular to said vertical ribs, said at least one passage formed in said lateral rib.
5: The system of claim 2 wherein said mounting portion includes a mounting rail with a planar surface having holes passing therethrough for receipt of fasteners to secure said mounting rail to the roof, said planar surface of said mounting rail including a perimeter skirt on an uppermost side of said planar surface extending down from said planar surface, said perimeter skirt including at least one gap therein, said gap adapted to allow airflow to pass through said skirt, said gap forming a portion of said at least one airflow pathway.
6: The system of claim 2 wherein an end piece is located below a lower side of a lowermost one of said series of mounting brackets, said undulating end piece configured to hold said lower side off of said roof and adapted to allow airflow therethrough.
7: The system of claim 6 wherein said end piece is an undulating end piece configured to include repeating troughs and crests which are sufficiently open to allow airflow to enter beneath said bracket by passing through said undulating end piece.
8: The system of claim 1 wherein said mounting portion is adjacent said upper side, said mounting portion including a skirt extending down from a top edge of said upper side, said skirt including a plurality of gaps therein, said gaps adapted to allow air circulation therethrough.
9: The system of claim 8 wherein each said bracket includes at least one wind clip on an underside of said bracket extending downward and positioned to be located adjacent said roof when said bracket is located adjacent said roof, said wind clips positioned to fit into at least one of said gaps in said skirt of an adjacent mounting bracket, such that said gap in said skirt provides both airflow therethrough and holding of said wind clip of an adjacent said bracket.
10: The system of claim 1 wherein at least two photovoltaic elements are assembled together into a single stack of layers with said photovoltaic elements forming one layer in said stack assembly, said stack assembly sized to be approximately twice as wide as one of said mounting brackets and similar in height to a height of a cell support structure of each said bracket, such that two adjacent laterally spaced mounting brackets are similar in size to one of said photovoltaic element stack assemblies for support of said photovoltaic element stack assembly upon said pair of adjacent laterally spaced brackets, said brackets adapted to be coupled together laterally in a manner allowing lateral motion therebetween, such that thermal expansion of said mounting brackets relative to said photovoltaic element stack assembly is accommodated by an expansion joint between said pair of mounting brackets.
11: The system of claim 10 wherein each said mounting bracket includes both a vertical expansion joint for vertical thermal expansion between each said mounting bracket and adjacent vertically spaced mounting brackets, and each said mounting bracket includes a lateral joint adapted to move relative to lateral joints of adjacent mounting brackets.
12: The system of claim 11 wherein said lateral expansion joint includes each said mounting bracket having one lateral side thereof configured with an over tab and an opposite lateral side of each said mounting bracket configured to include an under tab, said over tab and said under tab adapted to be complementally formed to fit together with said over tab overlying said under tab, and accommodating lateral motion therebetween.
13: The system of claim 12 wherein said lateral expansion joint is similar at joints between pairs of brackets underneath a common photovoltaic element stack assembly and at joints between adjacent brackets of different photovoltaic element stack assemblies.
14: The system of claim 1 wherein said system includes edge flashing, said edge flashing adapted to overlie lateral edges of said mounting brackets and underlie roof shingles on the roof and lateral to said system.
15: The system of claim 14 wherein said edge flashing includes a top plate adapted to overlie a top surface of said mounting bracket and a bottom plate adapted to be located adjacent the roof and beneath the shingles mounted on the roof, with a web joining said top plate with said bottom plate.
16: The system of claim 15 wherein said web of said edge flashing between said top plate and said bottom plate taper in height to cause said top plate to be closer to said bottom plate of an upper end of said edge flashing than at a lower end of said edge flashing.
17: The system of claim 1 wherein each of said photovoltaic elements is coupled together in series with at least one adjacent photovoltaic element which coupled photovoltaic elements are in turn each coupled to a J-box assembly adapted to be formed within a solid housing to be resistant to moisture, with two leads extending therefrom, one of said leads extending to an adjacent panel of photovoltaic elements on one side with the other lead extending to an adjacent panel of photovoltaic elements on the other side, and with the leads adapted to be coupled to other J-boxes of other photovoltaic element panels or combined as strings of sufficient current and voltage, to combine power from different arrays of photovoltaic element panels.
18: A method for managing thermal heating of photovoltaic panels, comprising in combination:providing at least two photovoltaic elements of substantially planar form; the photovoltaic elements adapted to convert photonic radiation into electric power; at least two mounting brackets including a higher mounting bracket above a lower mounting bracket, the mounting brackets adapted to be interposed between at least one photovoltaic element and the roof; each mounting bracket having a similar form; each mounting bracket having a mounting portion closer to an upper side than to a lower side, the mounting portion adapted to be coupled to the roof in fixed position relative to the roof; each mounting bracket having the lower side opposite the upper side, the lower side of the higher mounting bracket adapted to fit over at least a portion of the adjacent lower one of the at least two mounting brackets to define an overlapping portion;providing an open pathway extending beneath the at least two mounting brackets from the lower side of the lower mounting bracket to the upper side of the higher mounting bracket;locating a second similar photovoltaic element at least partially overlapping the first photovoltaic element, the open pathways beneath the elements aligned together to allow natural convection airflow beneath both of the brackets.
19: The method of claim 18 including the further step of interlocking adjacent mounting brackets that are adjacent each other but vertically spaced from each other, such that the mounting brackets tend to hold each other down.
20: The method of claim 18 wherein said mounting brackets are configured to overlap laterally in a sliding fashion to accommodate thermal expansion across the joint between the laterally overlapping mounting brackets.
21: The method of claim 18 including the further step of sealing lateral edges of an array of multiple photovoltaic panels by configuring edge flashing with a top plate adapted to reside above a lateral edge of the photovoltaic panel and a bottom plate adapted to reside above a roof and beneath shingles on the roof, with a web jointing the top plate to the bottom plate.
22: A bracket for supporting a photovoltaic power generation element upon a roof, the bracket comprising in combination:a photovoltaic element support plane on an upper surface of the bracket;a plurality of vertical ribs extending down from said photovoltaic element support plane and adapted to hold the bracket above an underlying roof surface;a mounting rail adjacent an upper side of said bracket, said mounting rail adapted to be attached to the roof;said bracket having a bottom rail on a side of said bracket opposite said mounting rail;said mounting rail adapted to reside beneath a bottom rail of an adjacent higher similarly formed mounting bracket; andat least one wind clip coupled to said bracket, said wind clip adapted to fit beneath a mounting rail of an adjacent lower mounting bracket, such that the pair of mounting brackets support each other and wind loads are resisted.
23: The bracket of claim 22 wherein said wind clip is a thin elongate structure adapted to be located directly adjacent the roof, said wind clip sized to fit within a gap in a skirt extending down from an upper edge of a planar surface of said mounting rail, said gap in said skirt acting both to allow airflow therethrough and to receive said finger therein.
24: The bracket of claim 23 wherein said bracket includes an air circulation pathway beneath said bracket to facilitate natural convection.
25: The bracket of claim 24 wherein said bracket includes at least one lateral rib extending substantially perpendicular to said vertical ribs, said lateral rib including at least one passage passing therethrough, such that airflow can occur from a lower end of said bracket to an upper end of said bracket at least partially through said at least one passage.
26: The bracket of claim 22 wherein said bracket is adapted to overlap laterally with adjacent photovoltaic element panels to form lateral joints, with said lateral joints configured to fit between adjacent brackets under a common photovoltaic element subassembly, or between adjacent photovoltaic element subassemblies.
27: The bracket of claim 26 wherein each photovoltaic element assembly is sized to fit upon two adjacent laterally spaced similar mounting brackets with a lateral joint interposed between said two brackets, said lateral joint adapted to expand and contract laterally due to thermal forces.
FIELD OF THE INVENTION
The following invention relates to mounting systems for mounting photovoltaic cells on roofs of buildings. More particularly, this invention relates to mounting brackets and mounting bracket systems which are particularly configured for supporting photovoltaic cells upon composition roofs in a manner which has a low profile and blends in nicely with adjacent shingles.
BACKGROUND OF THE INVENTION
Photovoltaic cells have enjoyed increasing popularity over time as various different technical hurdles associated with the use of photovoltaic cells have been overcome. Photovoltaic cells are generally solid state devices formed of various materials (often silicon) which generate electric current when exposed to photonic radiation, such as solar radiation.
One form of photovoltaic cell is configured so that it can rest upon a bracket which is particularly configured to be mounted to the shingles on a roof or directly upon the roof and have perimeter edges thereof blend into the roofing structure. Such a system is described in Published Patent Application No. 2007/0042683, and is by the same inventor of this application. This published application is incorporated herein by reference in its entirety. The system of that application is particularly configured for relatively thick concrete tile type roofs. In contrast, composition roofs are quite thin, as well as certain tile roofs, such as slate roofs which have relatively thin shingles. Accordingly, a need exists for a lower profile mounting bracket for a photovoltaic cell assembly. Also, with such a lower profile technical challenges are presented such as how to keep the bracket and cells below temperatures at which damage can occur, and how to secure the bracket and cells to the roof sufficient to resist high wind loads.
Photovoltaic cells must operate effectively in an extreme thermal environment. The brackets supporting the cells must similarly endure this extreme environment. Not only does the temperature do damage to the materials forming the bracket, but also thermal forces cause thermal expansion which can lead to distortion or breakage of the cells, or loosening of the mounting system provided by the brackets. As brackets for photovoltaic cells become thinner, the opportunity to cool by natural convection beneath the bracket and above the roof is diminished. Especially when it is desirable to have the photovoltaic cells blend into the adjacent shingles, such blending tends to block natural convection air circulation cooling, leading to degraded performance.
In addition to thermal issues, photovoltaic panels benefit from being able to withstand the wind loads expected by local building codes. Such wind loads can be quite extreme in some environments, particularly those which periodically experience hurricanes or other extreme weather phenomena.
SUMMARY OF THE INVENTION
With this invention a roof mounting bracket is provided for a photovoltaic power generation system that is particularly configured to allow assemblies of photovoltaic cells to be easily and securely mounted to roofs which have a thin roofing material such as composition roof shingles, slate shingles or other thin planar shingles. The mounting bracket and associated photovoltaic cells are relatively thin and are configured to be sealed in a watertight fashion so that the brackets and assemblies of cells can act effectively as shingles, while also accommodating natural convection air cooling of the brackets and panels to prevent excessive heat from building up and damaging the brackets or panels.
In particular, a standardized configuration bracket is provided which has an upper side generally defining a mounting portion which can be secured to an underlying roof. A lower side opposite the upper side forming the mounting portion is configured to overlap the mounting portion of the next lower bracket in a series of vertically spaced brackets extending down the slope of the roof. A cell support structure is provided between the mounting portion and the lower side. This cell support structure can support a plurality of photovoltaic cells and associated layers formed together in a cell stack assembly which rests upon the cell support structure and is secured to the cell support structure. This photovoltaic cell stack assembly is preferably twice as wide as the bracket so that two similarly formed brackets are placed adjacent each other and laterally spaced from each other to support a single photovoltaic cell stack assembly, and define a single "panel." The joint between the two brackets acts as an expansion joint for the panel.
Such panels can each be fitted with a single J-box which receives electric power from the various cells within the photovoltaic cell stack assembly. This J-box can then be coupled to leads of J-boxes of adjacent panels in series. Each series string of panels can also be connected to a combiner box, an inverter and a subpanel for effective utilization of the electric power generated by the panels.
The brackets have an air circulation system that allows air to be routed by natural convection beneath the brackets. A lowermost bracket of a series of vertically spaced brackets has an end piece fitted under a lower side thereof to hold up the lower side of the lowermost bracket (because it is not resting upon an upper side of a next lower bracket) to allow air to enter beneath the lowermost bracket. Ribs forming an underside of each bracket have various different passages or gaps therein to allow airflow through the end piece and beneath each bracket and then beneath the next higher bracket up in the series, until the air by natural convection escapes out an upper side of an uppermost bracket.
Edge flashing is provided to keep water from migrating around lateral sides of the brackets and the panels, especially at edges of an overall system of multiple panels. This flashing has one side that fits beneath shingles upon the roof adjacent a perimeter of the system. Wind clips are provided on each bracket which interlock with adjacent and lower brackets so that the brackets are somewhat interlocked together and resist wind loads acting upon the brackets.
OBJECTS OF THE INVENTION
Accordingly, a primary object of the present invention is to provide a system for generating power directly from sunlight that is mountable on a roof having thin shingles thereon, without compromising the performance of the roof or the performance of the power generation system.
Another object of the present invention is to provide a photovoltaic power generation system which can be mounted on a roof or other support structure and which is cooled by natural convection and secured in place to prevent displacement thereof.
Another object of the present invention is to provide a roof mounted photovoltaic power generation system which is easy to mount upon a roof of a structure.
Another object of the present invention is to provide a photovoltaic power generation system which includes multiple mounting brackets each of a similar construction to simplify construction of the overall system.
Another object of the present invention is to provide a roofing system which effectively keeps water from coming in contact with structural portions of the roof and which also is configured to convert solar radiation into electric power.
Another object of the present invention is to provide a power generation system which effectively utilizes the space available on the roof of a building as a source of solar power generation.
Another object of the present invention is to provide a method for interlocking solar panels on a roof that allows the panels to be easily mounted upon the roof and resist displacement due to wind loads thereon.
Another object of the present invention is to provide a roof mounting bracket for photovoltaic power generation system which can expand and contract with temperature changes without damaging the system.
Another object of the present invention is to provide a photovoltaic panel which can be easily connected to adjacent panels and an electric subsystem for conditioning the power and delivering the power for beneficial use.
Other further objects of the present invention will become apparent from a careful reading of the included drawing figures, the claims and detailed description of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top perspective view of a single bracket of the roof mounted photovoltaic power generation system of this invention.
FIG. 2 is a bottom perspective view of that which is shown in FIG. 1.
FIG. 3 is a top perspective view of a pair of mounting brackets joined together and ready to receive a photovoltaic cell stack assembly thereon with an expansion joint provided between the two brackets of the panel.
FIG. 4 is a perspective view of an undulating end piece for placement below a lower side of a lowermost mounting bracket of an overall system of photovoltaic panels, such that air can enter beneath the panels for natural convection cooling of the panels.
FIG. 5 is a sectional view taken along the line 5-5 of FIG. 3 illustrating details of a lateral expansion joint between adjacent brackets.
FIG. 6 is a top perspective view similar to that which is shown in FIG. 3, but from an opposite side.
FIG. 7 is a sectional view taken from the side and showing how adjacent similar mounting brackets overlap each other vertically with a lower side of a higher bracket overlapping an upper side of a lower bracket to define an overlapping portion between adjacent brackets.
FIG. 8 is a perspective view of adjacent brackets from adjacent panels and illustrating wiring for the J-boxes that facilitate electric coupling of adjacent panels together and with photovoltaic cell stack assemblies removed.
FIG. 9 is a top perspective view of a photovoltaic cell panel including both a pair of brackets and a photovoltaic cell stack assembly, and configured as a lower most panel such that a pair of undulating end pieces are provided beneath a lower side of the panel.
FIG. 10 is a perspective view of portions of a pair of panels resting upon a roof and showing a portion of the undulating end piece and the air circulation system of this invention.
FIG. 11 is a perspective view of a portion of a roof with a series of panels thereon and with photovoltaic cell stack assemblies on two of the panels removed and with arrows depicting pathways for airflow beneath the panels.
FIG. 12 is a perspective view of edge flashing for use at lateral sides of panels at lateral edges of an overall system of panels for water tight integration with shingles upon the roof.
FIG. 13 is a perspective view of a portion of a roof with the edge flashing of FIG. 12 in use adjacent lateral edges of a series of panels.
FIG. 14 is a schematic of a series of solar panel tiles each linked together and to a combiner box as well as to an inverter and subpanel to define an overall photovoltaic power generation system according to this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings, wherein like reference numerals represent like parts throughout the various drawing figures, reference numeral 10 is directed to a bracket (FIGS. 1 and 2) for a roof mounted photovoltaic power generation system. The brackets 10 are provided in pairs 12 (FIG. 3) which together support a photovoltaic cell 102 stack assembly to form a panel 100 (FIG. 9). The panel 100 can act similar to a shingle S (FIG. 13) upon the roof R to shed water and protect structural portions of the roof. The brackets 10 interlock together laterally and vertically while accommodating airflow therebeneath for cooling. The brackets also accommodate thermal expansion and have edge details to facilitate airflow and to provide water preclusion. The brackets are also configured to facilitate interconnection of an electric subsystem 110 for combining adjacent panels 100 together as part of the overall photovoltaic power generation system.
In essence, and with particular reference to FIGS. 1-3, basic details of the bracket 10 are described. The bracket 10 is typically utilized in pairs 12 (FIG. 3) as a structural portion of a panel 100 (FIG. 9) also supporting photovoltaic cell 102 stack assemblies thereon. The brackets 10 each include a mounting rail 20 at an upper side and a bottom rail 50 at a lower side. A cell support structure 30 is interposed between the mounting rail 20 and bottom rail 50. A lateral joint 40 defines lateral sides of each bracket 10. The lateral joint 40 is configured so that it can interface with lateral edges of adjacent brackets 10 for lateral interconnection of multiple brackets 10, either of a common panel 100 (where the joint 40 is an expansion joint 14 (FIGS. 3 and 9) in the middle of the panel 100) or lateral interconnection of adjacent panels 100.
An air circulation system 60 routes air beneath the brackets 10 so that by natural convection air can be circulated beneath the brackets 10 and cool the brackets 10 and associated photovoltaic cell stack assemblies 102. An end piece 70 (FIGS. 3, 4, 9-11 and 13) is provided adjacent the bottom rail of a lowest bracket in a series of vertically spaced brackets 10. The end piece 70 holds up this lower side of the lowermost bracket so that air can pass beneath the bracket 10 and be routed beneath the series of brackets 10 for cooling. Edge flashing 80 (FIGS. 12 and 13) is provided so that water is prevented from migrating around the brackets 10 or panels 100 laterally. A J-box 90 (FIG. 8) is provided for each panel 100 to combine power from photovoltaic cells 102 of each panel 100 and allow the power from each panel 100 to be combined together into strings which can then be routed to a combiner box before being passed on to an inverter 140 and subpanel 130 for effective utilization of the electric power from the system. An electric subsystem 110 (FIG. 14) is described which utilizes the panels 100 formed of brackets 10 according to this system.
More specifically, and with particular reference to FIGS. 1-3, specific details of the bracket 10 are described, according to a preferred embodiment. Each bracket 10 is preferably similar in form and in this preferred embodiment is comprised of a mounting rail 20 (FIGS. 1 and 2), a cell support structure (FIGS. 1 and 2), a lateral joint (FIG. 5) and a bottom rail 50 (FIGS. 1, 2 and 7). Each bracket 10 most preferably provides only half of the structural under support for a panel 100 (FIG. 9). Thus, a pair 12 of brackets 10 are provided together along with the photovoltaic cells 102 within a stack assembly to complete the panel 100 (FIG. 3). In this way, an expansion joint 14 (FIG. 3) is provided between the two brackets 10 within each pair 12. Note that the expansion joint 14 is the same as the lateral joint 40 with different terminology used depending on whether the brackets 10 are coming together at a midpoint within a panel 100 or at a lateral edge of a panel 100 where adjacent panels 100 are joined together laterally.
An upper side of each bracket 10 is defined by the mounting rail 20. The mounting rail 20 provides a preferred form of mounting portion for the bracket 10. This mounting rail 20 preferably includes a planar surface 22 with holes 24 passing therethrough for fasteners to pass and then penetrate the roof R. Preferably, a recess 26 surrounds each hole 24 to provide relief into which a head of the fastener can reside, such as the head of a roofing nail, or the head of a fastening screw.
A perimeter skirt 28 preferably surrounds at least an upper edge of the planar surface 22 of the mounting rail 20. The perimeter skirt 28 preferably extends perpendicularly down from the planar surface 22. Gussets 29 are preferably formed beneath the planar surface 22 to provide structural support and rigidity to the mounting rail 20 (FIG. 2). The perimeter skirt 28 also helps to rigidify the bracket 10.
The mounting rail 20 is typically covered by a bottom rail 50 of a higher adjacent similar bracket 10 of a separate higher adjacent panel 100 (FIGS. 7 and I1). However, a highest panel 100 will be formed of brackets 10 which have mounting rails 20 which are not covered by adjacent brackets 10 or panels 100. Instead, the highest panels 100 will have their mounting rails 20 typically covered by shingles placed on the roof R and allowed to have lower shingle edges overlap the mounting rail 20 portion of the bracket 10. If desired, a tapering piece of filler material can be provided directly above this highest bracket so that rather than having a somewhat abrupt transition in thickness at the perimeter skirt 28 of the mounting rail 20, a more gradual transition to greater thickness can be provided.
Most preferably, this perimeter skirt 28 is kept ventilated so that air circulating beneath the brackets 10 can escape out of the perimeter skirt 28, such as through gaps 58 (FIG. 2). In a preferred form of the invention, this highest row of brackets 10 are near a ridge of the roof and a ridge vent is provided which overlaps the mounting rail 20 portion of the bracket 10 and allows air circulating beneath the brackets 10 to escape. Such ridge vents are known in the composition shingle roofing construction trades.
The cell support structure 30 is provided below the mounting rail 20 and extending down to the bottom rail 50. This cell support structure 30 is generally formed of a series of vertical ribs 32 and at least one lateral rib 34 extending substantially perpendicular to the vertical ribs 32. A perimeter deck 36 surrounds a perimeter of this cell support structure space with the perimeter deck 36 generally planar with upper sides of the vertical ribs 32 and lateral rib 34. A trough 38 (FIG. 5) preferably is formed in the perimeter deck 36 and defines a slightly recessed depression in the perimeter deck 36. This trough 38 can accommodate adhesive to hold the photovoltaic cell 102 stack assembly within the cell support structure 30 space and against the perimeter deck 36 (FIG. 7). A lip 39 defines a lowermost edge of the cell support structure 30 and acts as a barrier to keep the photovoltaic cell 102 stack assembly from migrating downward out of the cell support structure 30 space.
The cell support structure 30 of the bracket 10 adds some rigidity to the overall panel 100 when two brackets 10 are provided laterally together along with a photovoltaic cell 102 stack assembly. However, the photovoltaic cell 102 stack assembly also adds rigidity and strength to the resulting panel 100. Windows between adjacent vertical ribs 32 and lateral rib 34 are open until covered by the photovoltaic cell 102 stack assembly. With such a rib cell support structure 30, the overall bracket 10 has a minimum of material and thus maintains light weight while still providing strength where required to keep the panel 100 sufficiently strong to resist weight loads, such as from snow loading or from maintenance personnel walking on the panels 00.
The lateral joint 40 (FIG. 5) is formed of an over tab 42 on one lateral side of the bracket 10 and an under tab 46 on the other lateral side of the bracket 10. The over tab 42 and under tab 46 fit together with the over tab 42 over the under tab 46. A cell support plane 41 is defined above the lateral joint 40 formed of the photovoltaic cell 102 stack assembly which rests upon this cell support plane 41.
The over tab 41 extends to a tip 43. The tip 43 extends primarily upward from the trough 38, but also extends slightly downward to a heel 44. The heel 44 rests within an expansion slot 49 formed on a shelf 48 of the under tab 46. A perimeter wall 47 is located beneath the shelf 48 and helps support the shelf 48. The heel 44 can ride within this expansion slot 49 some distance to allow for lateral motion therebetween (along arrow B of FIGS. 3 and 5), such as to decrease spacing when temperatures increase and increase spacing when temperatures decrease. Such lateral expansion and contraction across the lateral joints 40 and expansion joint 14 (FIG. 3) allows the brackets 10 to accommodate temperature changes without damaging the panels 100 or causing the system to fail. In one embodiment the lateral joint 40 is formed with the heel 44 in a middle of the expansion slot 49 with the brackets 10 and other portions of the panel 100 substantially at room temperature. In this way, the bracket 10 and panel 100 can undergo thermal expansion or contraction away from room temperature either in a cooling direction or a heating direction and the heel 44 will have room to move in either direction within the expansion slot 49 before damage will occur to the brackets 10 or the panel 100.
Preferably, the lateral joint 40 (and expansion joint 14) are not fitted with any adhesive, but rather are allowed to float relative to each other. Both the over tab 42 and under tab 46 are able to shed water in a downward direction while overlapping each other, such that water is prevented from migrating beneath the bracket 10 around or through this lateral joint 40. When configured as the expansion joint 14, the photovoltaic cell 102 stack assembly further covers the expansion joint 14 to resist water migration therethrough except at the mounting rail 40 (FIGS. 3 and 9).
The bottom rail 50 defines a lowermost portion of each bracket 10 (see particularly FIG. 2). The bottom rail 50 includes an edge wall 52 defining an extreme lower side of each bracket 10. Feet 53 (FIG. 7) define an underside of the bottom rail 50 which are configured to rest upon the mounting rail 20 of an adjacent lower bracket 10 and most particularly just below the mounting rail 20 and over the cell support structure 30 as well as over the photovoltaic cells 102 of the stack assembly of the next lower panel 100 (FIG. 7). In such an arrangement, thermal expansion and contraction can be accommodated (along arrow C of FIG. 7) by sliding of the feet 53 up or down along the pitch of the roof R (horizontally in FIG. 7).
The bottom rails 50 are configured not to rest on the roof R directly, but rather to rest upon an adjacent lower bracket 10. A wind clip 55 defines a portion of the underside of each bracket 10 adjacent the bottom rail 50. These wind clips 55 are preferably in the form of elongate rigid structures extending downwardly as a portion of an underside of each vertical rib 32. These wind clips 55 are configured so that they can rest on the roof R and fit within the gaps 58 of the perimeter skirt 28 in the mounting rail 20 of the next lower bracket 10. In this way, the bottom rail 50 of each bracket 10 is held down by the mounting rail 20 of the next lower bracket 10.
The wind clip 55 includes a clearance space 56 above each wind clip 55. A step 57 defines an abutment which can be provided on every other rib 32, rather than a wind clip 55, and help to keep the brackets 10 aligned adjacent each other. Preferably, the brackets 10 are not placed with the steps 57 abutting the mounting rails 20 when installed, but rather with a small gap therebetween to accommodate some thermal expansion that would tend to drive adjacent brackets 10 against each other. The bottom rail 50 also preferably includes stiffeners 59 in the form of horizontal and vertical ribs adjacent the bottom rail 50 to help strengthen the bottom rail 50 and also supporting the feet 53 of the bottom rail 50. The gaps 58 (FIG. 2) in the perimeter skirt 28 of the mounting rail 20 are sized to receive the wind clips 55 therein, while also providing openings for air circulation therethrough.
With particular reference to FIGS. 3, 6, 10 and 11, details of the air circulation system 60 of this invention are described, according to a preferred embodiment. The brackets 10 are configured to interconnect together in a way that preserves an air circulation system 60 driven by natural convection to help cool the brackets 10 and the overall photovoltaic power generation system. This air circulation system 60 begins with end pieces such as the undulating end piece 70 (FIG. 4) which are fitted beneath the bottom rail 50 of a lowermost bracket 10 of an overall power generation system (FIG. 11).
The bottom rail 50 is not configured to have the feet 53 rest upon the roof R. Rather, the feet 53 are configured to rest upon an adjacent lower mounting rail 20 or the cell support structure 30 just below the mounting rail 20. Thus, the end piece 70 is provided to hold up the bottom rail 50 of the bracket 10 defining a lowermost portion of the overall system.
This end piece 70 is preferably in the form of an undulating end piece with lateral ends 72 spaced from each other and with troughs 74 and crests 76 alternating between the ends 72. Airflow is thus easily accommodated through the end piece 70 and beneath the brackets 10. While the end piece 70 is shown relatively shallow in extent toward the mounting rail 20, most preferably the end piece is deep enough toward the mounting rail 20 to abut the steps 57 (FIG. 2). In this way the lowest brackets 10 in the series of panels 100 is fully supported beneath the bottom rail 40 by the end piece 70. The deeper end piece can be captured by the wind clip 55 to further secure the end piece to the bracket 10.
Airflow (along arrow A) passes through the troughs 74 and crests 76 in the undulating end piece 70. This air is then located beneath the bracket 10. Heat within the bracket 10 or within other portions of the panel 100 or roof R is allowed to transfer to the air in this space beneath the bracket 10. With the air having been heated, natural convection causes the air to rise. While the photovoltaic cell 102 stack assembly keeps the air from rising purely vertically, passages 62 are preferably formed in the lateral rib 34 which allow the air to pass beneath the cell support structure 70 from the bottom rail 50 up to the mounting rail 20.
The gaps 58 in the perimeter skirt 28 allow the air to continue from beneath the mounting rail 20 and to under the next bracket 10 (arrow A of FIGS. 3 and 11). This airflow can continue beneath each of the brackets 10 until the highest bracket 10 is reached. The air can then escape out the gaps 58 in the highest brackets 10. With such airflow, a maximum temperature of the panels 100 is minimized. Different patterns of gaps 58 and passages 62 can be provided to route the air where desired for maximum cooling heat transfer, to optimize performance of the power generation system.
With particular reference to FIGS. 12 and 13, details of the edge flashing 80 are described, according to a preferred embodiment. The edge flashing 80 is provided to keep water from migrating beneath the brackets 10 and panels 100 along lateral edges of the overall system. While the lateral joints 40 preclude water from getting beneath the panels 100 where panels 100 are spaced laterally from each other, eventually the panels 100 at a perimeter edge of the overall system are reached. The edge flashing 80 is then utilized to transition from the panels 100 to shingles S upon the roof R.
With particular reference to FIG. 13, a series of three panels 100', 100'', 100''' are shown stacked adjacent each other with an undulating end piece 70 at a lower side of the lowermost panel 100'. The edge flashing 80 is configured with upper ends 82 opposite lower ends 84 and with a top plate 86 spaced from a bottom plate 88 by a web 85, with the plates 86, 88 generally parallel with each other. The top plate 86 is configured to rest upon an upper surface of the panel 100. The bottom plate 88 is configured to rest adjacent the roof R with shingles S resting on top of the bottom plate 88. The web 85 joints the two plates 86, 88 together and precludes water from migrating laterally beneath the panels 100. The edge flashing 88 overlaps somewhat at the ends 82, 84 to further preclude water migration at seams between adjacent pieces of edge flashing 80.
Because each of the brackets 10 and associated photovoltaic cell 102 stack assemblies taper somewhat in thickness with a thinnest edge adjacent the mounting rail 20 and a thickest edge adjacent the bottom rail 50, the web 85 preferably tapers from being shorter at the upper ends 82 to being longer at the lower ends 84. In this way, such tapering of the brackets 10 and overall panels 100 can be accommodated. Typically, the edge flashing 80 is formed by cutting rigid planar material, such as galvanized steel, and bending it to have the shape depicted in FIG. 12.
With particular reference to FIG. 8, particular details of a J-box 90 and associated electrical interconnection for the photovoltaic cells 102 within each panel 100 are described, according to a preferred embodiment. The J-box 90 is preferably an electronic device embedded within a waterproof resin to make it entirely waterproof.
Each photovoltaic cell 102 stack assembly is preferably formed of a series of separate cells 102 (most typically fourteen in two rows of seven a piece). In a simplest form of the invention, as few as one photovoltaic cell could be provided on each panel 100 of two brackets 10. Photovoltaic cells 102 are shown in this embodiment as a preferred form of photovoltaic element. Other photovoltaic elements could be substituted, such as thin film photovoltaic materials or structures, either now known or later developed. These separate cells 102 are joined together in series electrically. They are then laminated together between layers of waterproof materials.
Particularly, this layering preferably involves a low iron glass as a top layer, followed by a low melt temperature plastic layer such as EVA, followed by the photovoltaic cells themselves, followed by another low melt temperature plastic layer such as EVA, followed by a layer of Tedlar. This layering stack is laminated to further preclude water penetration. This stack is followed by an adhesive for mounting to the perimeter deck 36 of the cell support structure 30 of the bracket 10. One adhesive that can be utilized is known as adhesive 804 Dow Flexible Adhesive provided by the Dow Chemical Company of Midland, Mich.
Because the photovoltaic cells 102 are encased within this sandwich, electrical connections between adjacent photovoltaic cells are kept from shorting out, such as due to the presence of water when rain is falling on the roof. At the J-box 90, separate conductors from the series of photovoltaic cells 102 are routed into the J-box 90 so that all of the power from the series of photovoltaic cells 102 within the panel 100 are received at the J-box 90. This power is then routed through leads 94, 96. The leads 94, 96 allow adjacent panels 100 to be coupled together, typically in series.
Support clips 98 preferably extend from the perimeter skirt 28 of the mounting rail 20. These support clips 98 can hold the leads 94, 96 therein to prevent them from experiencing damage. The leads 94, 96 are preferably insulated to allow direct exposure to the elements. Slots 95 are provided at strategic locations in the perimeter skirt 28 of the mounting rail 20 to allow the leads 94, 96 to extend through the perimeter skirt 28 before bending 90° and extending along the perimeter skirt 28 and over the support clips 98. Couplers 97 allow the leads 94, 96 to be interconnected together to connect a series of such panels 100 together in series.
Each series connection of such panels 100 can be combined together through an end lead 112 extending into a combiner box 120 to further combine power from individual panels 100 and to configure the overall power from the series of panels 100 into power having the desired voltage and current. Inverters 140 can be utilized downstream from a combiner box 120 if it desired to generate AC power. Transformers can be utilized if a different current and voltage is desired.
The inverter 140 is typically coupled to a subpanel 130 where the power can be effectively utilized as AC power service within a residential structure or sold to a power company, or put to other beneficial use. The converter box 120, inverter 140 and subpanel 130 together form an electrical subsystem 110 which receives end leads 112 from separate strings of panels 100 through function of the leads 94, 96 and J-box 90.
Each panel 100 (also referred to as a "tile" or "solar tile") is typically provided in an array including N columns and M rows. Typically, each row is coupled in series and routed to a common combiner box 120 through end leads 112. In one form of the invention, panels 100 are coupled together in series until the desired voltage for the system is achieved. Then multiple such strings of series connections of panels are joined together in the combiner box 120 to increase the current provided by the overall system.
This disclosure is provided to reveal a preferred embodiment of the invention and a best mode for practicing the invention. Having thus described the invention in this way, it should be apparent that various different modifications can be made to the preferred embodiment without departing from the scope and spirit of this invention disclosure. When structures are identified as a means to perform a function, the identification is intended to include all structures which can perform the function specified. When structures of this invention are identified as being coupled together, such language should be interpreted broadly to include the structures being coupled directly together or coupled together through intervening structures. Such coupling could be permanent or temporary and either in a rigid fashion or in a fashion which allows pivoting, sliding or other relative motion while still providing some form of attachment, unless specifically restricted.
Patent applications by Ronald J. Gangemi, Grass Valley, CA US
Patent applications in class With a sunlight activated device (e.g., passive solar or photoelectric)
Patent applications in all subclasses With a sunlight activated device (e.g., passive solar or photoelectric)