Pressure-equalizing PV assembly and method

Abstract
Each PV assembly of an array of PV assemblies comprises a base, a PV module and a support assembly securing the PV module to a position overlying the upper surface of the base. Vents are formed through the base. A pressure equalization path extends from the outer surface of the PV module, past the PV module, to and through at least one of the vents, and to the lower surface of the base to help reduce wind uplift forces on the PV assembly. The PV assemblies may be interengaged, such as by interengaging the bases of adjacent PV assemblies. The base may include a main portion and a cover and the bases of adjacent PV assemblies may be interengaged by securing the covers of adjacent bases together.
Description




BACKGROUND OF THE INVENTION




Air moving across an array of photovoltaic (PV) assemblies mounted to the roof of a building, or other support surface, creates wind uplift forces on the PV assemblies. Much work has been done in the design and evaluation of arrays of PV assemblies to minimize wind uplift forces. See U.S. Pat. Nos. 5,316,592; 5,505,788; 5,746,839; 6,061,978; and 6,148,570. Reducing wind uplift forces provides several advantages. First, it reduces the necessary weight per unit area of the array. This reduces or eliminates the need for strengthening the support surface to support the weight of the array, thus making retrofit easier and reducing the cost for both retrofit and new construction. Second, it reduces or eliminates the need for the use of roof membrane-(or other support surface-) penetrating fasteners; this helps to maintain the integrity of the membrane. Third, the cost of transporting and installing the assembly is reduced because of its decreased weight. Fourth, lightweight PV assemblies are easier to install than assemblies that rely on ballast weight to counteract wind uplift forces. Fifth, when designed properly, the assembly can serve as a protective layer over the roof membrane or support surface, shielding from temperature extremes and ultraviolet radiation.




SUMMARY OF THE INVENTION




Various aspects of the invention are based upon the discovery and recognition that (1) wind uplift forces are spatially distributed, both dynamically and randomly, so that wind uplift forces on a particular PV assembly within an array of PV assemblies changes rapidly in magnitude; and (2) interengaging the various PV assemblies within an array of PV assemblies causes wind uplift forces acting on a single PV assembly to be transferred to other, typically adjacent, PV assemblies.




A first aspect of the invention is directed to an array of pressure-equalizing photovoltaic (PV) assemblies mountable to a support surface. Each PV assembly comprises a base, a PV module and a support assembly securing the PV module to a position overlying the upper surface of the base. Vents are formed through the base. A pressure equalization path extends from the outer surface of the PV module, past the PV module, to and through at least one of the vents, and to the lower surface of the base. This provides pressure equalization between the outer surface of the PV module and the lower surface of the base to help reduce wind uplift forces on the PV assembly. The PV assemblies may be interengaged, such as by interengaging the bases of adjacent PV assemblies. The array may also include a deflector and a multi-position deflector support securing the deflector to the base at shipping and inclined-use angles. The array maybe circumscribed by a perimeter assembly. Cross strapping, extending above, below or through the array, or some combination of above, below and through the array, may be used to secure one perimeter element to a non-adjacent perimeter element.




A second aspect of the invention is directed to a PV system comprising a support surface and an array of pressure-equalizing photovoltaic (PV) assemblies mounted to the support surface, Each PV assembly comprises a base, a PV module and a support assembly securing the PV module to a position overlying the upper surface of the base. Vents are formed through the base. A pressure equalization path extends from the outer surface of the PV module, past the PV module, to and through at least one of the vents, and to the lower surface of the base. This provides pressure equalization between the outer surface of the PV module and the lower surface of the base to help reduce wind uplift forces on the PV assembly. The peripheral edges of adjacent PV assemblies are separated by an average distance of about d.




A third aspect of the invention is directed to a PV assembly, for use on a support surface. Each PV assembly comprises a base, a PV module and a module support assembly securing the PV module to a position overlying the upper surface of the base. The PV module is oriented at a first angle to the base by the module support and a deflector is oriented at a second angle to the base by a deflector support. Vents are formed through the base. A pressure equalization path extends from the outer surface of the PV module, past the deflector, to through at least one of the vents and to the lower surface of the base. This provides pressure equalization between the outer surface of the PV module and the lower surface of the base to help reduce wind uplift forces on the PV assembly.




A fourth aspect of the invention is directed to a PV system comprising a support surface, comprising alternating ridges and troughs, and an array of pressure-equalizing photovoltaic (PV) assemblies mounted to the support surface. Each PV assembly comprises a base, a PV module and a support assembly securing the PV module to a position overlying the upper surface of the base. A vent is formed through the base between the center of the PV module and the support assembly. A pressure equalization path extends from the outer surface of the PV module, past the PV module, to through the vent and to the lower surface of the base. This provides pressure equalization between the outer surface of the PV module and the lower surface of the base to help reduce wind uplift forces on the PV assembly.




A fifth aspect of the invention is directed to a method for reducing wind uplift forces on an array of pressure-equalizing photovoltaic (PV) assemblies mountable to a support surface. Each PV assembly comprises a base, a PV module and a support assembly securing the PV module to a position overlying the upper surface of the base. The method comprises forming vents through the base and creating a pressure equalization path extending from the outer surface of the PV module, past the PV module, to and through at least one of the vents, and to the lower surface of the base. The PV module may be oriented at an angle to the base and a deflector may be mounted at an angle to the base, the module and deflector having portions defining a gap therebetween.




A sixth aspect of the invention is directed to a method for reducing wind uplift forces on an array of pressure-equalizing photovoltaic (PV) assemblies mountable to a support surface comprising alternating ridges and troughs. Each PV assembly comprises a base, a PV module and a support assembly securing the PV module to a position overlying the upper surface of the base. The method comprises forming vents through the base and creating pressure equalization paths extending from the outer surface of the PV module, past the PV modules, to and through at least one of the vents, and to the lower surface of the base.




The provision of the vents in the base of the PV assembly provides for pressure equalization to reduce or eliminate wind uplift forces. Appropriately positioning the array on the roof of a building also helps to reduce wind uplift forces. Reducing wind uplift forces provides several advantages. First, it reduces the necessary weight per unit area of the array. This reduces or eliminates the need for strengthening the support surface to support the weight of the array, thus making retrofit easier and reducing the cost for both retrofit and new construction. Second, it reduces or eliminates the need for the use of roof membrane-(or other support surface-) penetrating fasteners; this helps to maintain the integrity of the membrane. Third, the cost of transporting and installing the assembly is reduced because of its decreased weight. Fourth, lightweight PV assemblies are easier to install than assemblies that rely on ballast weight to counteract wind uplift forces. In addition, using a PV assembly comprising a base permits the PV assembly to help protect the support surface from the effects of sun, wind, rain, etc., and also, when the base comprises thermal insulation, increases the thermal insulation qualities of the support surface. Further, the interengagement of the PV assemblies, and the maintenance of the interengagement of the PV assemblies, helps to ensure that uplift forces on one PV assembly tends to get transferred to adjacent PV assemblies thereby helping to counteract wind uplift forces.




Other features and advantages of the invention will appear from the following description in which the preferred embodiments have been set forth in detail in conjunction with the accompanying drawings.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a simplified top plan view showing an array of PV assemblies mounted to the horizontal roof of a building;





FIG. 2

is a simplified side view illustrating the height of the building of FIG.


1


and the height of a parapet surrounding the roof surface;





FIG. 3

is a cross-sectional view taken along line


3





3


of

FIG. 1

with the bottom surface of the base shown spaced apart from the support surface for purposes of illustration;





FIG. 4

is enlarged view showing the joint between two PV modules of

FIG. 3

;





FIG. 5

is an alternative embodiment of the structure shown in

FIG. 4

;





FIG. 6

is a top plan view of a portion of the array of PV assemblies of

FIG. 1

illustrating the location of vents, formed through the base, and support assemblies, supporting the PV module above the base;





FIG. 7

is a simplified cross-sectional view taken along line


7





7


of

FIG. 6

;





FIG. 8

is a view similar to

FIG. 6

illustrating an alternative embodiment of the invention in which vent holes are formed at the joint between adjacent bases;





FIG. 9

is enlarged cross-sectional view taken along line


9





9


of

FIG. 8

;





FIG. 10

is a side view of an alternative embodiment of the PV assembly of

FIG. 3

showing the use of Z-type support assemblies;





FIG. 11

is enlarged view of a portion of the PV assembly of

FIG. 10

showing the use of a low-e film between the base and the PV module;





FIG. 12

shows an alternative embodiment of the structure of

FIG. 4

in which interengagement of the bases is accomplished by fastening one base to an adjacent base;





FIG. 13

shows a further alternative embodiment in which electrically conductive covers of adjacent bases are electrically secured to one another through an electrical ground connection which also acts to secure the adjacent PV assemblies to one another;





FIG. 14

is a simplified side view of the PV assembly in which the PV module comprises a flexible PV panel mounted to a PV panel stiffener which provides the necessary support of the flexible PV panel;





FIG. 15

illustrates an alternative embodiment of the perimeter assembly of

FIG. 3

in which a ballast element is housed within a perimeter pan;





FIG. 16

illustrates a further alternative perimeter assembly using a unitary perimeter element fastened to the adjacent PV assembly;





FIG. 17

is a simplified top plan view illustrating the interconnection of perimeter elements circumscribing an array of PV assemblies to create a belt-like perimeter assembly;





FIG. 18

is a further alternative embodiment of a belt-like perimeter assembly showing the use of cross strapping to secure spaced apart perimeter elements to one another;





FIG. 19

is a cross-sectional view taken along line


19





19


of

FIG. 18

illustrating the overlapping of adjacent perimeter pans;





FIG. 20

is a cross-sectional view taken along line


20





20


of

FIG. 18

illustrating the connection of the cross strapping to one perimeter element and the passage of the cross strapping between the PV module and the base;





FIG. 21

is a simplified side view of an alternative embodiment of the invention in which the PV module is positioned at an angle to the base, the PV assembly includes an angled deflector, and a gap is defined between the upper edges of the PV module and the deflector;





FIG. 22

is a top plan view of the PV assembly of

FIG. 21

illustrating the location of the vents formed through the base;





FIG. 23

illustrates an alternative to the PV assembly of

FIG. 21

in which vent conduits are used between the vents and the gap;





FIGS. 24 and 25

are top plan and side views of an alternative embodiment of the PV assembly of

FIGS. 21 and 22

in which the support assemblies for the PV module and deflector help to define a constricted flow path between the gap and the vent;





FIGS. 26

,


27


and


28


illustrate top, plan and side views of an alternative embodiment of the assembly of

FIGS. 24 and 25

in which the support assemblies are multiposition support assemblies which permit positioning the PV module and deflector in the inclined-use configuration of FIG.


27


and the shipping configuration of

FIG. 28

,

FIG. 28

also illustrating use of a shipping block to help support the PV module during shipping and storage;





FIG. 29

illustrates a portion of a perimeter element, used with the inclined PV assembly of

FIGS. 21 and 22

, including an end cap extending upwardly from the pan so to at least substantially cover the triangular opening created by the upwardly extending edges of the PV module and deflector;





FIG. 30

is a side view of the structure of

FIG. 29

including a ballast element housed within the pan;





FIG. 31

illustrates an alternative embodiment of the perimeter assembly of

FIG. 30

;





FIG. 32

is a simplified top plan view showing an array of PV assemblies mounted to a support surface comprising alternating ridges and troughs;





FIG. 33

is a simplified cross-sectional view taken along line


33





33


of

FIG. 32

showing the use of blocking within the troughs between the support surface and the bases of the PV assemblies, which blocking may be thermally insulating;





FIG. 34

is a side elevational view showing the details of a perimeter element used with a PV assembly mounted to a corrugated roof;





FIG. 35

is an isometric view illustrating a length of the perimeter element of FIG.


34


and showing wind baffles extending into the troughs of the corrugated roof;





FIG. 36

is similar to

FIG. 35

with the curb cover and the wind baffle removed to illustrate the mounting elements;





FIGS. 37-39

illustrate structure similar to that of

FIGS. 34-36

used when the perimeter assembly runs parallel to the corrugations;





FIG. 40

illustrates the mounting elements of a perimeter assembly used with a standing seam roofing system and showing the use of support foam between the support surface of the roof and the bottom of the base; and





FIG. 41

is a cross-section view of the perimeter assembly of

FIG. 40

adjacent a PV assembly.











DESCRIPTION OF THE SPECIFIC EMBODIMENTS





FIG. 1

illustrates a PV system


10


comprising an array


12


of PV assemblies


14


mounted to a support surface


16


, the support surface being the horizontal roof of a building


18


. Array


12


is surrounded by a perimeter assembly


20


. As shown in

FIG. 2

, building


18


has a height H and a parapet


22


with a parapet height P. PV assemblies


14


are interconnected, as shown in

FIG. 3

, along their abutting edges. This interconnection is important because of the way wind uplift forces act on the array. The magnitude of the wind uplift forces on any particular PV assembly


14


within array


12


changes rapidly over time so that the wind uplift forces on one PV assembly may be much greater or much less than the wind uplift forces on an adjacent PV assembly. Therefore, large uplift forces tending to raise one PV assembly are counteracted because raising the one PV assembly will tend to be resisted by the weight of adjacent PV assemblies.




It has been found through wind tunnel testing that it is possible to determine if array


12


of PV modules


24


is or is not in a desired location on roof


16


of building


18


. Wind tunnel testing is carried out using the actual PV modules of interest. The collected data can be provided in chart form suitable for use with various roof locations, typically near an edge (an edge position), near two edges (a corner position) or not near an edge (a middle roof position). For example, assuming a parapet height of 40 cm and a building height of 30 meters, the maximum 3-second wind gust speed for a middle roof position may range from 120-140 mph (depending on the wind direction) while for a corner or edge position the maximum 3-second wind gust speed will be about 100 to 110 mph (depending on the wind direction).




As shown in

FIGS. 3 and 4

, each PV assembly


14


comprises a PV module


24


supported above a base


26


by a support assembly


28


. Support assembly


28


comprises spaced-apart support member


29


adhered, or otherwise fastened, to PV module


24


and to base


26


. Base


26


comprises a main body


30


, which may be made of thermally insulating foam, such as polystyrene, by DOW Chemical, or Noryl PPO (polyphenylene oxide) by GE Plastics, and a base cover


32


. Base cover


32


may serve several functions, including adding strength to base


26


, protecting main body


30


from degradation due to exposure to sunlight, and also permitting adjacent bases to be securely fastened to one another so to keep them from separating and thus losing the benefits of being interengaged. Base cover


32


may be an electrically conductive sheet metal cover made of polyvinylidene fluoride (PVDF) resin-coated metal. PVDF resin is available from ATOFINA Chemicals, Inc of Philadelphia, Pa. as KYNAR® polyvinylidene fluoride (PVDF) resin. Alternatively, base cover


32


could be made of, for example, galvanized steel, steel, zinc-alum, or aluminum. Cover


32


may have an electrically insulating surface coat of, for example, PVDF resin, Noryl PPO, ASA 606 Acrylic paint by Colloid Research, Inc., or ceramic filled resin coatings by ICS Technologies or EP21LV epoxy by Master Bond Inc. Alternatively, cover


32


may be electrically non-conducting, such as Noryl PPO, ASA 606 Acrylic paint, ceramic filled resin, or other non-conducting material. The interengagement of adjacent PV assemblies


14


is through the use of tongue and groove interengagement elements


34


,


36


formed in main body


30


of each base


26


and, alternatively, or in addition, by mechanically fastening covers


32


to one another using fasteners


38


. One or more radiant barriers


40


,


42


,


44


, shown in dashed lines in

FIG. 3

, may be used between or against PV module


24


and base


26


. The use of radiant barriers, typically low emissivity (low-e) films, is described in more detail in U.S. Pat. No. 6,061,978. The use of thermal insulation in conjunction with PV modules is described in the following U.S. Pat. Nos. 5,316,592; 5,505,788; 5,746,839; and 6,148,570.




A number of vents


46


are formed in base


26


to provide pressure equalization paths


48


extending from the outer surface


50


of PV module


24


, past the peripheral edge


52


of the PV module, to and through vents


46


, and to the lower surface


54


of base


26


. In

FIGS. 3 and 4

there is an exaggerated gap


56


shown between the lower surface


54


of base


26


and support surface


16


. Thus, when wind is moving over array


12


and creates one or more low pressure regions above the one or more PV assemblies


14


, the differential pressure between outer surface


50


of PV module


24


and lower surface


54


of base


26


can be at least partially equalized by the passage of air along paths


48


. The vents


46


include peripheral vents


58


, see

FIG. 6

, that are generally aligned or coincident with peripheral edge


52


, and interior vents


60


. Peripheral vents


58


are located between support assembly


28


and the outer edge


66


of base


26


. Pressure equalization paths


48


, passing through peripheral vents


58


, are unobstructed from peripheral edge


52


to the vents. The pressure equalization paths extending through interior vents


60


have partially obstructed path portions from peripheral edge


52


to vents


60


due to the locations of the various support elements


62


,


64


and the positions of vents


60


between the center


61


of PV module


24


and support elements


62


,


64


; see FIG.


6


.




The inner surface


63


of PV module


24


is separated from the upper surface


65


of base


26


by an average distance of about h. Peripheral edges


52


are separated by an average distance of about d. The d/h ratio is preferably about 0.1 to 6 and more preferably about 0.5 to 3. Distances h and d typically range from about 1.3 cm to 10 cm for h and about 1.3 cm to 7.6 cm for d, but may be greater or lesser than these distances.




There is a trade-off between the size and number of vents and the thermal insulation provided by base


26


. Assume peripheral vents


58


for a PV assembly


14


have a total cross-sectional area of V and PV module


24


has a cross-sectional area of P. The percentage of V to P is (1) at least about 0.02 percent and preferably at least about 0.07 percent, and (2) about 0.02 percent to 50 percent, and preferably about 0.05 percent to 5 percent and more preferably about 0.07 percent to 2 percent. Forming vents in this manner aids the ability to use a PV assembly


14


having a weight of about 5-25 kg per square meter while avoiding the need to attach PV assembly


14


to support surface


16


. In addition, if the total cross-sectioned area of peripheral vents


58


is w, it is preferred that the percentage of w to P be about 0.1% to 50% and more preferably about 0.4% to 5%. The determination of the percentage of w to P involves balancing the desire to minimize the holes, as they require additional manufacturing steps and degrade the insulating quality of the foam layer, with the desire to maximize the holes to improve resistance to wind uplift. So the final decision as to the percentage of w to P will typically result in the determination of the minimum vent area needed to withstand uplift forces with comfortable safety margin.





FIG. 5

illustrates an alternative embodiment of a PV assembly


67


in which PV module


24


is mounted directly onto base


68


using an adhesive as the support assembly; other support structures, such as fasteners or clips, or a combination of support structures, could be used as the support assembly. Base


68


is similar to base


26


but includes no cover


32


. Also, base


68


only has peripheral vents


58


which lie generally coincident with peripheral edge


52


of PV module


24


.





FIGS. 8 and 9

illustrate vents


70


formed at the intersecting outer edges


66


of adjacent bases


26


. Such vents


70


are also considered to be generally aligned with or coincident with peripheral edge


52


of PV module


24


.





FIGS. 10 and 11

illustrate a PV assembly


72


using Z-type supports


74


secured to PV module


24


with an adhesive


76


. Z-type supports


74


are preferably integral, one-piece extensions of base cover


32


. Supports


74


may also be attached to base cover


32


. A low emissivity (low-e) film


78


is situated between cover


32


and PV module


24


.





FIG. 12

illustrates an alternative method of interengaging adjacent bases


68


using


30


fastener brackets


80


mounted to each base with the brackets secured together by a double-headed fastener


82


, such as a nut and bolt or rivet.

FIG. 13

illustrates another alternative in which base covers


32


are interengaged and electrically connected by an electrical ground connection


84


between adjacent covers. A wide variety of interengagement elements and electrical ground connections, including rigid, flexible and elastic elements, may be used.





FIG. 14

illustrates supporting a flexible PV panel


86


with a PV panel stiffener


88


to create a self-supporting, generally rigid PV module


89


.




Perimeter assembly


20


, see

FIGS. 1 and 3

, comprises a series of perimeter elements


90


. Typically, each perimeter element


90


is the same length as one side of a PV assembly


14


. Perimeter elements


90


are preferably secured to one another so that perimeter assembly


28


is a belt-like perimeter assembly. Perimeter assembly


20


serves several functions including (1) maintaining the spatial integrity of array


12


by helping to prevent PV assemblies


14


from shifting or otherwise moving laterally relative to one another, and (2) deflecting air away from the lateral edges of array


12


. This latter function is aided by configuring perimeter elements


90


with a sloped outer surface


92


and providing perimeter elements


90


with an upper edge


94


which is about equal in elevation to or above outer surface


50


of PV module


24


. Perimeter elements typically weigh about 3-52 kg per linear meter, and more preferably about 18-30 kg per linear meter.





FIG. 15

illustrates an alternative perimeter element


96


comprising a perimeter pan


98


having an outer lip


100


which is joined to a base portion


102


. A generally v-shaped coupler


104


extends from base portion


102


and may be fastened to base


26


by a fastener


106


. Perimeter element


96


also includes a ballast element


108


, typically made from concrete, stone or other suitably heavy material.

FIG. 16

illustrates a unitary perimeter element


110


which may be fastened to base


26


by a fastener


112


. Perimeter element


110


is preferably a molded or cast material, such as concrete, or plastic. As shown in

FIG. 17

, perimeter elements


110


may be secured together using ball and socket type of engagement members


114


.





FIGS. 18-20

illustrates a further embodiment of a perimeter assembly using perimeter elements


116


similar to perimeter element


96


with the following differences. A cap


118


is used to cover ballast element


120


, the cap defining a sloped outer surface


122


and an upper edge


124


of perimeter element


116


. A coupler


126


is a relatively simple L-shaped member and extends from a pan


128


. The pans


128


of adjacent perimeter elements


116


, overlap, as shown in

FIGS. 18 and 19

, to help increase the structural rigidity between perimeter elements


116


.

FIGS. 18 and 20

also illustrate the use of cross strapping


130


between perimeter elements


116


on opposite sides of the array


132


of PV assemblies


14


. In this embodiment cross strapping


130


passes between PV module


24


and base


26


. It could, however, pass entirely beneath PV assembly


14


, entirely above the PV assembly, or combination of above, below and through the PV assembly. Cross strapping


130


helps to maintain the desired shape of perimeter assembly


134


and thus of array


132


of PV assemblies


14


. Other cross-strapping arrangements, such as triangular, may also be used.





FIGS. 21 and 22

illustrates an inclined PV assembly


138


comprising a base


140


, an inclined PV module


142


, and an inclined deflector


144


; the PV module and deflector are mounted at first and second angles


146


,


148


to the base by a pair of dual purpose supports


150


. Angle


146


is typically about 5 degrees to 30 degrees while angle


148


is typically about 20 degrees to 70 degrees. The opposed upper edges


152


,


154


of module


142


and deflector


144


define a gap


156


overlying a set of vents


158


formed in base


140


. Gap


156


is typically about 2-8 cm wide. Edges


152


,


154


are typically about the same distance above base


140


. While it may be desirable to use additional vents through base


140


at different locations, it has been found through wind tunnel testing that positioning vents


158


to be generally aligned with or coincident with gap


156


and providing substantially unobstructed flow paths between the gap and the vents appears to be effective in substantially reducing wind uplift forces on inclined PV assembly


138


.





FIG. 23

illustrates an alternative embodiment to the assembly shown in

FIGS. 21 and 22

in which an inclined PV assembly


160


uses hollow conduits


162


to fluidly couple gap


156


and vents


158


. An advantage of using hollow conduits


162


by constraining the fluid pathway, more pressure at the top the gap is transferred directly to under the base.





FIGS. 24 and 25

illustrates a further alternative embodiment of an inclined PV assembly


166


in which the support assembly is split up into a PV module support assembly


168


and a deflector support assembly


170


. A deflector


172


is formed by the outer surface of deflector support assembly


170


. Support assemblies


168


,


170


are formed of bent sheet metal and define a constrained flow path


174


between a gap


176


and a single, slot-like vent


178


. Base


180


is an extended-width base to provide a walkway


182


adjacent to deflector


172


. Within an array, all of the PV assemblies do not need to be designed with an extended-width base to provide a walkway


182


.





FIGS. 26 and 27

illustrate an inclined PV assembly


186


similar to the embodiment of

FIGS. 24 and 25

but using a multiposition PV module support assembly


188


and a multiposition deflector support assembly


190


. Support assembly


188


comprises a hinged support


192


at one end of PV module


142


and a strut


194


pivotally mounted near upper edge


152


of module


142


. Assembly


188


also includes a clip


196


at the outer end of strut


194


and a complementary clip


198


positioned adjacent to a hollow extension


200


of vent


178


(see FIG.


28


). The deflector support assembly


190


includes similar support structure. Clips


196


,


198


engage when assembly


186


is in an inclined, in-use configuration of

FIG. 27

to maintain the inclined configuration under wind loads.

FIG. 28

shows PV module


142


and deflector


144


in a shipping configuration at which PV module


142


and deflector


144


are generally parallel to base


140


so that angles


146


,


148


are generally about 0 degrees or about 180 degrees. To aid support of module


142


in the shipping configuration of

FIG. 28

, a shipping block


202


is positioned between PV module


142


and base


140


; a similar support block may be used between deflector


144


and base


140


. Other means for stabilizing and supporting PV module


142


and deflector


144


in either or both of the in-use and shipping configurations may be used. Also, strut


194


may be made to be adjustable in length so to vary first angle


146


; this may require that deflector support assembly


190


be adjustable so to permit adjustment of the second angle


148


.





FIGS. 29 and 30

illustrate the use of an end cap perimeter element


204


, similar to perimeter element


96


of

FIG. 15

, including a ballast element


206


. The primary difference is that coupler element


96


is substantially enlarged to create an end cap coupler


208


sized to at least substantially cover the generally triangular opening created by the upwardly extending edges


210


and


212


of PV module


142


and deflector


144


.

FIG. 31

illustrates a perimeter element


214


similar to the perimeter element of

FIGS. 29 and 30

. Perimeter element


214


includes a sloped end cap


216


, similar to that shown in

FIGS. 19 and 20

, and a tongue and groove interengagement region


218


for interengagement with base


140


. Perimeter elements


204


,


214


provide end caps for angled PV assemblies; end caps may also be provided separate from the perimeter elements.





FIG. 32

is a top plan view illustrating an array


220


of PV assemblies


222


. The PV assemblies illustrated are conventional assemblies available from PowerLight Corporation of Berkeley, Calif. as PowerGuard® and are similar to PV assemblies


14


of FIG.


3


. Array


220


is supported by a corrugated roof


224


, having alternating ridges


226


and troughs


228


, and thermally insulating support blocking


230


within troughs


228


. Array


220


is surrounded by a perimeter assembly


232


, shown in more detail in

FIGS. 34-38

. Perimeter assembly


232


comprises mounting elements


234


mounted to ridges


226


of roof


224


using conventional corrugated roof fasteners


236


which pass through base


238


of mounting element


234


. Mounting element


234


includes an upstanding portion


240


having a support tab


242


at its upper end and a laterally extending securement clip


244


between base


238


and support tab


242


. The clip


244


engages the upper surface


246


of the base


248


of PV assembly


222


to help secure PV assembly


222


, and thus array


220


, to roof


224


. Base


248


is of conventional construction with upper surface


246


of a cementitious material covering an expanded polystyrene main body


249


.




An L-shaped wind baffle member


250


is secured to bases


238


of mounting elements


234


and has a series of downwardly extending wind baffles


252


sized and shaped to fill substantial portions of troughs


228


beneath perimeter assembly


232


. Perimeter assembly


232


also includes a cover


254


extending between support tabs


242


and bases


238


. Cover


254


has a sloped outer surface


256


. Perimeter assembly


232


has an upper edge


258


that is generally even with or vertically above the outer surface


260


of the PV module


262


of PV assembly


222


.

FIGS. 37-39

show mounting elements


264


; mounting elements


264


are modified from mounting elements


234


to accommodate positioning perimeter assembly


232


along the sides of array


220


that run parallel to troughs


228


. The main difference is that base


266


of mounting element


264


is much longer and extends to both sides of upstanding portion


240


.





FIGS. 40 and 41

illustrate a standing seam roofing system


268


having standing seam or ridge portions


270


and pan or trough portions


272


. Trough portions


272


are effectively filled with blocks of thermally insulating support foam


274


to both provide thermal insulation for roofing system


268


and support an array of PV assemblies


222


and a walkway-type of perimeter assembly


276


. Perimeter assembly


276


includes a paver


278


made similarly to base


248


to provide a walkway around the array of PV assemblies


222


. L-shaped flashing


280


engages the outer peripheral edge


282


of paver


278


and is secured to standing seam portions


270


by brackets


284


, such as available from Hougovens Aluminum Bausysteme GmbH of Koblenz, Germany as Kal-Zip brackets. A sloped cover


286


is mounted along the edge


288


of paver


278


to lie adjacent to assemblies


222


. Sloped cover


286


has an upper edge


290


positioned at least about even with or above outer surface


268


of PV module


262


.




The embodiments of the

FIGS. 33-41

show the use of insulating foam blocking within the troughs of the building surface. Other types of material, preferably thermally insulating material, can be used, such as polyurethane-based spray foam insulation.




In use, vents are formed through base


26


to create one or more pressure equalization paths


48


extending from outer surface


50


of PV module


24


, past peripheral edge


52


, to and through at least one of the vents, and to lower surface


54


of the base. At least some of vents


46


may be positioned to be generally aligned or coincident with peripheral edge


52


. Pressure equalization path


48


may be created so that the portion of the path extending from peripheral edge


52


to a vent


46


is an unobstructed path portion. See, for example,

FIGS. 4

,


9


,


21


and


24


. As shown in

FIGS. 21-31

, PV module


142


may be oriented at an angle


146


to the base


140


and a deflector


144


may be mounted at an angle


148


to the base, the module and deflector having upper edges


152


,


154


defining a gap


156


therebetween. At least one hollow conduit


162


may be used to fluidly couple gap


156


and vent


158


. An array of the PV assemblies is mounted to a support surface, typically a horizontal roof; sloped support surfaces may also be used. Mounting typically can be accomplished without the need for fasteners to attach to PV assemblies to the support surface even though the weight of the PV assemblies is in the range of about 10 kg per square meter to 40 kg per square meter and preferably in the range of about 15 kg per square meter to 25 kg per square meter. This is possible, as discussed above, by the of pressure-equalization created through the use of vents and pressure equalization flow paths, and by the use of a perimeter assembly to help maintain the interengagement of the PV assemblies and help deflect wind away from the edges of the array. If desired, support surface-penetrating fasteners or adhesives, or a combination thereof, may be used.




The mounting procedure varies somewhat when an array of PV assemblies is mounted to a support surface comprising alternating ridges and troughs. The troughs beneath the perimeter of the array of PV assemblies will typically be filled with wind deflectors. Thermal insulation is preferably placed in the troughs beneath the array for thermal insulation and to help support the array; however, the location of the thermal insulation may be limited to the perimeter portions of the array, such as the first meter in from all edges. At least one of the vents may be positioned at a location between the center of the PV module and the support assembly for each of a plurality of the PV modules.




Modification and variation can be made to the disclosed embodiments without departing from the subject of the invention as defined in the following claims.




Any and all patents, applications, and printed publications referred to above are incorporated by reference.



Claims
  • 1. An array of pressure-equalizing photovoltaic (PV) assemblies mountable to a support surface, each PV assembly comprising:a base having an upper surface and a lower surface; a PV module having an inner surface, an outer surface and a peripheral edge; a support assembly securing the PV module to a position overlaying the upper surface of the base; vents formed through the base; and a pressure equalization path extending from the outer surface of the PV module, past the PV module, to and through at least one of said vents, and to the lower surface of the base, whereby pressure equalization between the outer surface of the PV module and the lower surface of the base is provided to help reduce wind uplift forces on the PV assembly.
  • 2. The array according to claim 1 wherein adjacent ones of said PV assemblies engage one another so wind uplift forces on one of said PV assemblies tend to transfer to adjacent PV assemblies so to help counteract said wind uplift forces.
  • 3. The array according to claim 1 wherein adjacent ones of said PV assemblies engage at at least one of the bases, the PV modules and the support assemblies so wind uplift forces on one of said PV assemblies tend to transfer to adjacent PV assemblies so to help counteract said wind uplift forces.
  • 4. The array according to claim 1 wherein the base comprises an electrical conductor, and further comprising electrical ground connectors between the electrical conductors.
  • 5. The array according to claim 1 wherein the bases of adjacent PV assemblies are interengaged so wind uplift forces on one of said PV assemblies tend to transfer to adjacent PV assemblies so to help counteract said wind uplift forces.
  • 6. The array according to claim 1 wherein said vents have a total cross-sectional area of V and the PV module has a total surface area of P and the percentage of V to P is about 0.02% to 50% thereby aiding the ability to use a 1W assembly having a weight of about 5-25 kg per square m while avoiding the need for attachment of the PV assembly to the support surface.
  • 7. The array according to claim 1 wherein said vents have a total cross-sectional area of V and the PV module bas a total surface area of P and the percentage of V to P is about 0.05% to 5% thereby aiding the ability to use a PV assembly having a weight of about 5-25 kg per square m while avoiding the need for attachment of the PV assembly to the support surface.
  • 8. The array according to claim 1 wherein said vents have a total cross-sectional area of V and the PV module has a total surface area of P and the percentage of V to P is about 0.07% to 2% thereby aiding the ability to use a PV assembly having a weight of about 5-25 kg per square iii while avoiding the need for attachment of the PV assembly to the support surface.
  • 9. The array according to claim 1 wherein said vents have a total cross-sectional area of V and the PV module has a total surface area of P and the percentage of V to P is at least about 0.02% thereby aiding the ability to use a PV assembly having a weight of about 5-25 kg per square m while avoiding the need for attachment of the PV module to the support surface.
  • 10. The array according to claim 1 wherein said vents have a total cross-sectional area of V and the 1W module has a total surface area of P and the percentage of V to P is at least about 0.07% thereby aiding the ability to use a PV assembly having a weight of about 5-25 kg per square m while avoiding the need for attachment of the PV module to the support surface.
  • 11. The array according to claim 1 wherein the inner surface of the PV module is separated from the upper surface of the base.
  • 12. The array according to claim 1 wherein at least one of said vents is positioned generally centrally beneath the PV module.
  • 13. The array according to claim 1 wherein the support assembly is a multi-position support assembly and comprises first and second parts securing the PV module to the base at shipping and inclined-use angles relative to the base, said shipping angle being generally 0 degrees, said inclined-use angle being a first acute angle with the PV module extending away from the base.
  • 14. The array according to claim 13 further comprising:a deflector, and a multi-position deflector support securing the deflector to the base at deflector shipping and deflector inclined-use angles relative to the base, said deflector shipping angle being generally 0 degrees, said deflector inclined-use angle being a second acute angle with the deflector extending away from the base.
  • 15. The array according to claim 1 wherein the array of PV modules is circumscribed by a perimeter assembly.
  • 16. The array according to claim 15 wherein the perimeter assembly is a continuous, belting perimeter assembly, and further comprising cross-strapping, extending at least one of above, below or through the array, securing a first position along the perimeter assembly to at least a second position along the perimeter assembly thereby stabilizing the array against wind up-lift forces.
  • 17. A PV system comprising:a support surface; an array of pressure-equalizing photovoltaic (PV) assemblies mounted to the support surface, each PV assembly comprising: a base having an upper surface and a lower surface; a PV module having an inner surface, an outer surface and a peripheral edge; a support assembly securing the PV module to a position overlying the upper surface of the base; vents formed through the base; and a pressure equalization path extending from the outer surface of the PV module, past the PV module, to and through at least one of said vents, and to the lower surface of the base, whereby pressure equalization between the outer surface of the PV module and the lower surface of the base is provided to help reduce wind uplift forces on the PV assembly; and the peripheral edges of adjacent PV modules being separated by an average distance of about d.
  • 18. A PV assembly, for use on a support surface, comprising:a base having an upper surface and a lower surface; a PV module having an inner surface, an outer surface and a peripheral edge; a module support assembly securing the PV module to a position overlying the upper surface of the base; the PV module being oriented at a first angle to the base, the PV module extending away from the base from a first module portion to a second module portion; a deflector oriented at a second angle to the base by a deflector support, the deflector having first and second deflector portions, the deflector extending away from the base from the first deflector portion to the second deflector portion; vents formed through the base; and a pressure equalization path extending from the outer surface of the PV module, past the deflector, to and through at least one of said vents, and to the lower surface of the base, whereby pressure equalization between the outer surface of the PV module and the lower surface of the base is provided to help reduce wind uplift forces on the PV assembly.
  • 19. A PV system comprising:a support surface comprising alternating ridges and troughs; and an array of pressure-equalizing photovoltaic (PV) assemblies, each of a plurality of said PV assemblies comprising: a base having an upper surface and a lower surface; a PV module having an inner surface, an outer surface, a center and a peripheral edge; a support assembly securing the PV module to a position overlying the upper surface of the base; a vent formed through the base between the center of the PV module and the support assembly; a pressure equalization path extending from the outer surface of the PV module, past the PV module, to and through said vent, and to the lower surface of the base; and whereby pressure equalization between the outer surface of the PV module and the lower surface of the base is provided to help reduce wind uplift forces on the PV assembly.
  • 20. A method for reducing wind uplift forces on an array of pressure-equalizing photovoltaic (PV) assemblies mountable to a support surface, each PV assembly comprising a base having an upper surface and a lower surface, a PV module having an inner surface, an outer surface and a peripheral edge, and a support assembly securing the PV module to a position overlying the upper surface of the base, the method comprising:forming vents through the base; and creating a pressure equalization path extending from the outer surface of the PV module, past the PV module, to and through at least one of said vents, and to the lower surface of the base, whereby pressure equalization between the outer surface of the PV module and the lower surface of the base is provided to help reduce wind uplift forces on the PV assembly.
  • 21. The method according to claim 20 further comprising interengaging adjacent ones of said PV assemblies so wind uplift forces on one of said PV assemblies tend to transfer to adjacent PV assemblies so to help counteract said wind uplift forces.
  • 22. The method according to claim 20 further comprising selecting a base comprising an electrical conductor, and further comprising electrically grounding the electrical conductors of adjacent ones of said PV assemblies.
  • 23. The method according to claim 20 wherein said vents forming step is carried out so said vents for one PV assembly have a total cross-sectional area of V and the PV module has a total surface area of P and the percentage of V to P is about 0.02% to 50% thereby aiding the ability to use a PV assembly having a weight of about 5-25 kg per square m while avoiding the need for attachment of the PV assembly to the support surface.
  • 24. The method according to claim 20 wherein said vents Conning step is carried out so said vents for one PV assembly have a total cross-sectional area of V and the PV module has a total surface area of P and the percentage of V to P is about 0.05% to 5% thereby aiding the ability to use a PV assembly having a weight of about 5-25 kg per square m while avoiding the need for attachment of the PV assembly to the support surface.
  • 25. The method according to claim 20 wherein said vents forming step is carried out so said vents for one PV assembly have a total cross-sectional area of V and the PV module has a total surface area of P and the percentage of V to P is about 0.07% to 2% thereby aiding the ability to use a PV assembly having a weight of about 5-25 kg per square m while avoiding the need for attachment of the PV assembly to the support surface.
  • 26. The method according to claim 20 wherein said vents forming step is carried out so said vents for one PV assembly have a total cross-sectional area of V and the PV module has a total surface area of P and the percentage of V to P is at least about 0.02% thereby aiding the ability to use a PV assembly having a weight of about 5-25 kg per square m while avoiding the need for attachment of the PV assembly to the support surface.
  • 27. The method according to claim 20 wherein said vents forming step is carried out so said vents for one PV assembly have a total cross-sectional area of V and the PV module has a total surface area of P and the percentage of V to P is at least about 0.07% thereby aiding the ability to use a PV assembly having a weight of about 5-25 kg per square m while avoiding the need for attachment of the PV assembly to the support surface.
  • 28. The method according to claim 20 further comprising orienting the PV module at a first angle to the base so that the PV module extends away from the base from a first module portion to a second module portion.
  • 29. The method according to claim 28 further comprising mounting a deflector, having first and second deflector portions, to the base so that the deflector extends away from the base from the first deflector portion to the second deflector portion.
  • 30. The method according to claim 29 further comprising forming a gap between the second module and deflector portions.
  • 31. The method according to claim 30 wherein said gap forming step is carried out so that at least some of said vents are generally vertically aligned or coincident with said gap.
  • 32. The method according to claim 31 wherein said vents and gap forming steps are carried out so the outer surfaces of the PV modules have a total area equal to about m and the total cross-sectional area of said vents that are generally vertically aligned with said gaps is about w, the percentage of w to m being about 0.1% to 50%.
  • 33. The method according to claim 31 wherein said vents and gap forming steps are carried out so the outer surfaces of the PV modules have a total area equal to about m and the total cross-sectional area of said vents that are generally vertically aligned with said gaps is about w, the percentage of w to in being about 0.4% to 5%.
  • 34. The method according to claim 30 wherein the gap forming step comprises providing at least one hollow conduit fluidly coupling the gap and said at least one of said vents.
  • 35. The method according to claim 20 wherein said path creating step creates a constrained leakage path along said unobstructed path portion.
  • 36. A method for reducing wind uplift forces on an array of pressure-equalizing photovoltaic (PV) assemblies mountable to a support surface comprising alternating ridges and troughs, each PV assembly comprising a base having an upper surface and a lower surface, a PV module having an inner surface, an outer surface and a peripheral edge, and a support assembly securing the PV module to a position overlying the upper surface of the base, the method comprising:forming vents through the base; creating pressure equalization paths extending from the outer surfaces of the PV modules, past the PV modules, to and through at least one of said vents, and to the lower surface of the base, whereby pressure equalization between the outer surfaces of said PV modules and the lower surface of the base is provided to help reduce wind uplift forces on the PV assembly; and mounting the array of PV assemblies to the support surface.
CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. patent application Ser. No. 09/902,493 filed Jul. 10, 2001 now U.S. Pat. No. 6,570,084 and entitled Pressure-Equalizing Photovoltaic Assembly and Method.

Government Interests

The U.S. Government has a paid-up license in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of PVMat Subcontract ZAX-8-17647-12 awarded by the Department of Energy.

US Referenced Citations (20)
Number Name Date Kind
4677248 Lacey Jun 1987 A
4886554 Woodring et al. Dec 1989 A
5092939 Nath et al. Mar 1992 A
5316592 Dinwoodie May 1994 A
5505788 Dinwoodie Apr 1996 A
5647915 Zukerman Jul 1997 A
5746839 Dinwoodie May 1998 A
5787653 Sakai et al. Aug 1998 A
6046399 Kapner Apr 2000 A
6051774 Yoshida et al. Apr 2000 A
6061978 Dinwoodie et al. May 2000 A
6148570 Dinwoodie et al. Nov 2000 A
6495750 Dinwoodie Dec 2002 B1
6501013 Dinwoodie Dec 2002 B1
6534703 Dinwoodie Mar 2003 B2
6570084 Dinwoodie May 2003 B2
20030154666 Dinwoodie Aug 2003 A1
20030154667 Dinwoodie Aug 2003 A1
20030154680 Dinwoodie Aug 2003 A1
20040007260 Dinwoodie Jan 2004 A1
Foreign Referenced Citations (4)
Number Date Country
3611542 Apr 1986 DE
59-175168 Oct 1984 JP
62-73039 Apr 1987 JP
3-200376 Sep 1991 JP
Non-Patent Literature Citations (6)
Entry
Mr. Dan Shugar, P.E., “PowerLight to Install Solar Electric Roof Tile Manufacturing Facility with NYSERDA Cost-Sharing,” Press Release, Mar. 21, 1997, PowerLight Corporation, Berkeley, CA, USA.
Daniel S. Shugar, P.E., “PowerLight Completes 50 kW of PV Systems in Wyoming,” Press Release, Oct. 10, 1996, PowerLight Corporation, Berkeley, CA, USA.
Daniel S. Shugar, P.E. and Thomas L. Dinwoodie, AIA, “Photovoltaic Roof Tiles for Commercial Buildings,” Solar Today Magazine, Jul./Aug. 1996, pp 18-20, Boulder, CO, USA.
Patent Abstracts of Japan, abstract for JP 5-280168, Oct. 1993.
Patent Abstracts of Japan, abstract for JP 59-175168, Oct. 1984.
Patent Abstracts of Japan, abstract for JP 59-175169, Oct. 1984.
Continuations (1)
Number Date Country
Parent 09/902493 Jul 2001 US
Child 10/384513 US