U.S. patent number RE38,988 [Application Number 10/414,347] was granted by the patent office on 2006-02-28 for lightweight, self-ballasting photovoltaic roofing assembly.
Invention is credited to Thomas L. Dinwoodie.
United States Patent |
RE38,988 |
Dinwoodie |
February 28, 2006 |
**Please see images for:
( PTAB Trial Certificate ) ** |
Lightweight, self-ballasting photovoltaic roofing assembly
Abstract
A photovoltaic roofing assembly comprises a roofing membrane
(102), a plurality of photovoltaic modules (104, 106, 108) disposed
as a layer on top of the roofing membrane (102), and a plurality of
pre-formed spacers, pedestals or supports (112, 114, 116, 118, 120,
122) which are respectively disposed below the plurality of
photovoltaic modules (104, 106, 108) and integral therewith, or
fixed thereto. Spacers (112, 114, 116, 118, 120, 122) are disposed
on top of roofing membrane (102). Membrane (102) is supported on
conventional roof framing, and attached thereto by conventional
methods. In an alternative embodiment, the roofing assembly may
have insulation block (322) below the spacers (314, 314', 315,
315'). The geometry of the pre-formed spacers (112, 114, 116, 118,
120, 122, 314, 314', 315, 315') is such that wind tunnel testing
has shown its maximum effectiveness in reducing net forces of wind
uplift on the overall assembly. Such construction results in a
simple, lightweight, self-ballasting, readily assembled roofing
assembly which resists the forces of wind uplift using no roofing
penetrations.
Inventors: |
Dinwoodie; Thomas L. (Piedmont,
CA) |
Family
ID: |
24521389 |
Appl.
No.: |
10/414,347 |
Filed: |
April 15, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
08629052 |
Apr 8, 1996 |
05746839 |
May 5, 1998 |
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Current U.S.
Class: |
136/251; 136/291;
52/173.3; 136/246 |
Current CPC
Class: |
F24S
25/11 (20180501); F24S 25/16 (20180501); H02S
20/24 (20141201); F24S 2080/015 (20180501); Y02B
10/20 (20130101); Y02E 10/47 (20130101); Y02B
10/10 (20130101); F24S 40/85 (20180501); Y10S
136/291 (20130101); Y02B 10/12 (20130101); F24S
2025/6007 (20180501); F24S 2025/02 (20180501); Y02E
10/50 (20130101) |
Current International
Class: |
E04D
13/18 (20060101); H01L 31/048 (20060101) |
Field of
Search: |
;136/251,246,291
;52/173.3 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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3611542 |
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Oct 1987 |
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DE |
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59-175168 |
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Oct 1984 |
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JP |
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59-175169 |
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Oct 1984 |
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JP |
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59-175169 |
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Feb 1985 |
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JP |
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1-65154 |
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Apr 1989 |
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JP |
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3-200376 |
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Sep 1991 |
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JP |
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5-280168 |
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Oct 1993 |
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JP |
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5-280168 |
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Oct 1993 |
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JP |
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8-274364 |
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Oct 1996 |
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JP |
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Other References
Dinwoodie et al, "Optimizing Roof-Integrated Photovoltaics: A Case
Study of the PowerGuard Roofing Tile," Proceedings of the First
World Conference on Photovoltaic Energy Conversion, Dec. 4-9, 1994.
cited by examiner .
Dinwoodie et al "Optimizing Roof-Integrated Photovoltaics: A Case
Study of the PowerGuard.TM. Roofing Tile," IEEE/First World
Conference on Photovoltaic Energy Conversion, Dec. 4-9, 1994,
Waikoloa, Hawaii. cited by other.
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Primary Examiner: Diamond; Alan
Government Interests
This invention was made with Government support under Agreement No.
FG09-95EE15638 awarded by the Department of Energy. The Government
has certain rights in this invention.
Claims
What is claimed is:
1. A photovoltaic assembly comprising: .Iadd.a building rooftop;
.Iaddend. a photovoltaic module having sides and having upper and
lower surfaces; and a spacer secured to the lower surface of the
photovoltaic module .Iadd.and supported by the building
rooftop.Iaddend.; said spacer sized and configured to define: an
open region beneath said lower surface.Iadd., said open region
extending between and in contact with the lower surface and in
direct contact with the building rooftop, .Iaddend.and including
access openings formed therein for fluidly coupling said open
region to said upper surface; said access openings extending along
at least two sides of said photovoltaic module; whereby wind uplift
forces are resisted when said photovoltaic assembly is mounted to
.[.a support surface.]. .Iadd.the building rooftop.Iaddend..
2. The assembly according to claim 1 wherein said photovoltaic
module has at least three sides.
3. The assembly according to claim 2 wherein said spacer comprises
multiple spacer elements, at least one said spacer element secured
to said lower surface along each of said .Iadd.at least three
.Iaddend.sides.
4. The assembly according to claim 2 wherein said access openings
extend along said at least three sides of said photovoltaic
module.
5. The assembly according to claim 1 wherein said at least two
sides comprise two opposite sides of said photovoltaic module.
6. The assembly according to claim 1 wherein said access openings
extend along about 5% to 50% of the length of at least two said
sides.
7. The assembly according to claim 1 wherein said spacer has a
lower spacer surface and an upper spacer surface tapered relative
to said lower spacer surface, said tapered upper spacer surface
supporting said photovoltaic module so said open region is a
tapered open region tapering between said access openings along two
of said sides.
8. The assembly according to claim 7 wherein said tapered upper
spacer surface is at an angle of about 5.degree.-12.degree.
relative to the lower spacer surface so said photovoltaic module is
oriented at an angle of about 5.degree.-30.degree. relative to the
.[.support surface.]. .Iadd.building rooftop.Iaddend..
9. The assembly according to claim 7 wherein said photovoltaic
module has an upper side, said photovoltaic module extending
downwardly from said upper side, and further comprising a wind
deflection surface having an upper edge near said upper side, said
wind deflecting surface extending downwardly and outwardly away
from said upper side.
10. The assembly according to claim 9 wherein said upper edge is
about the same elevation as the upper side.
.[.11. The assembly according to claim 1 further comprising an
insulation member securable to the spacer when said spacer is
situated between said photovoltaic module and said insulation
member..].
.[.12. The assembly according to claim 11 wherein said spacer and
insulation member forms a variable-height support structure for
said photovoltaic module so that said open region is a tapered open
region tapering between said access openings along two of said
sides..].
.[.13. The assembly according to claim 12 wherein said photovoltaic
module has an upper side, said photovoltaic module extending
downwardly from said upper side, and wherein said insulation member
comprises a wind deflection surface having an upper edge near said
upper side, said wind deflection surface extending downwardly and
outwardly away from said upper side..].
14. The assembly according to claim .[.13.]. .Iadd.1
.Iaddend.wherein said spacer comprises a plurality of elongate
tapered spacers spaced apart from one another.
.[.15. The assembly according to claim 11 wherein said photovoltaic
module, insulation member, and spacer have a combined weight of
about two to four pounds per square foot..].
.[.16. The assembly according to claim 11 wherein said photovoltaic
assembly comprises means for interengaging said photovoltaic
module, spacer, and insulation member to create an integral
assembly for resisting the forces of wind uplift thus enabling
lower installed weight per unit area..].
17. The assembly according to claim 1 wherein said photovoltaic
assembly comprises means for interlocking one said photovoltaic
.[.module.]. .Iadd.assembly .Iaddend.to another said photovoltaic
.[.module.]. .Iadd.assembly.Iaddend..
18. The assembly according to claim 1 wherein said photovoltaic
module and spacer have a combined weight of about two to four
pounds per square foot.
19. .[.A photovoltaic assembly,.]. .Iadd.The assembly according to
claim 1 further .Iaddend.comprising: a plurality of .Iadd.said
spacer, said plurality of said spacer comprising .Iaddend.spacers
configured for disposal on top of .[.a building roof.]. .Iadd.the
building rooftop.Iaddend.; .Iadd.and .Iaddend. a plurality of
.Iadd.said photovoltaic module, said plurality of said photovoltaic
module comprising .Iaddend.photovoltaic modules .[.having sides
and.]. disposed on top of said spacers to form a photovoltaic
array.[.; and said spacers: being arranged in a geometry which
generally follows the sides of said photovoltaic modules; and
having openings that are between about 5% and 50% of the length of
at least two sides of each photovoltaic module; whereby said
geometry enables said photovoltaic assembly to resist forces of
wind uplift.]. .
20. The assembly of claim 19 wherein said spacers have a top
surface which is joined to said photovoltaic modules, forming an
integral unit.
21. The assembly of claim 19 wherein said spacers are positioned
adjacent to one another with said photovoltaic modules spaced apart
from one another, whereby water may drain between said photovoltaic
modules.
22. The assembly of claim 19 further comprising perimeter ties
situated around the .Iadd.photovoltaic .Iaddend.array and joined
with said .Iadd.photovoltaic .Iaddend.array to make an integral
array assembly.
23. The assembly of claim 22 wherein said perimeter ties are joined
with one another whereby the integral array assembly is tied
together and strengthened.
24. The assembly according to claim 22 wherein said perimeter ties
comprise a chosen one of concrete pavers and hollow metal flashing
units.
25. The assembly of claim 19 wherein said assembly further
comprises means for resisting forces of wind uplift sufficiently to
eliminate the need for penetrations of .[.a building roof.].
.Iadd.the building rooftop.Iaddend..
26. The assembly of claim 19 wherein said spacers are preformed
spacers.
27. The assembly of claim 19 wherein said spacers have a tapered
profile for orienting the photovoltaic module.Iadd.s .Iaddend.in a
direction for increased sun exposure.
28. The assembly of claim 27 wherein said spacers have tapered
profiles with first outwardly and downwardly tapered portions
supporting said photovoltaic modules and defining a tapered
air-space and second outwardly and downwardly tapered portions,
whereby wind is caused to flow over the spacer.Iadd.s .Iaddend.and
not underneath the photovoltaic module.Iadd.s.Iaddend., whereby
internal pressures within the tapered air-space created by the
spacers offset external pressures which aids the overall assembly
in resisting net forces of wind uplift.
29. The assembly of claim 19 wherein said spacers are sized to
orient the photovoltaic modules at an angle of about
5.degree.-12.degree. and create a tapered air space beneath the
photovoltaic modules.
30. The assembly according to claim 19 wherein said photovoltaic
array has a weight of about two to four pounds per square foot.
31. A photovoltaic roofing assembly, comprising: a plurality of
insulation blocks disposed as a layer on top of a roofing membrane;
a plurality of spacers configured for disposal on top of said
insulation blocks; a plurality of photovoltaic modules having
.Iadd.first, second, third and fourth .Iaddend.sides and disposed
on top of said spacers to form a photovoltaic array; and said
spacers: being arranged in a geometry which generally follows the
sides of said photovoltaic modules; and having openings that are
between 5% and 50% of the length of .[.at least two.]. .Iadd.each
of the first, second, third and fourth .Iaddend.sides of each
photovoltaic module; whereby said geometry enables said
photovoltaic assembly to resist forces of wind uplift.
32. The assembly of claim 31 wherein each of said insulation blocks
have adjoining sides with a joint disposed between said sides for
water drainage.
33. The assembly of claim 31 wherein said insulation blocks have
top surfaces which are joined to the spacers which in turn are
joined to photovoltaic modules, forming three-part integral
units.
34. The assembly of claim 31 wherein said spacers are sized to
orient the photovoltaic modules at an angle of about
5.degree.-12.degree. and create a tapered air space beneath the
photovoltaic modules.
35. The assembly according to claim 31 wherein said photovoltaic
array has a weight of no more than about four pounds per square
foot.
36. A photovoltaic roofing assembly comprising: a plurality of
photovoltaic assemblies, each said photovoltaic assembly
comprising: a photovoltaic module having upper, lower, and lateral
sides and having upper and lower surfaces; and a variable-height
spacer secured to the lower surface of the photovoltaic module so
to orient said photovoltaic module at an angle with said lateral
sides extending downwardly from said upper side to said lower side,
said angle being about 5.degree.-30.degree. from horizontal; said
spacer sized and configured to define: a tapered open region
beneath said lower surface; and access openings along said upper
and lower sides fluidly coupling said open region to said upper
surface; whereby wind uplift forces are resisted when said
photovoltaic assembly is mounted to a support surface; and means
for interengaging adjacent photovoltaic assemblies into an array of
photovoltaic assemblies, said array defining a perimeter.
37. The assembly according to claim .[.36.]. .Iadd.57
.Iaddend.wherein said perimeter assembly comprises a concrete
paver.
38. The assembly according to claim 36 wherein said photovoltaic
assembly further comprises a wind deflection surface, having an
upper edge near the upper side, extending downwardly and outwardly
away from said upper side.
39. The assembly according to claim 38 wherein said spacer provides
said wind deflection surface.
40. The assembly according to claim 36 wherein said .[.array.].
.Iadd.plurality .Iaddend.of photovoltaic assemblies has a weight of
no more than about four pounds per square foot.
41. A method of making a photovoltaic roofing assembly, comprising
the following steps: joining a spacer to a photovoltaic module
.Iadd.having first, second, third and fourth sides.Iaddend.; sizing
and positioning said spacer to provide an open region beneath said
photovoltaic module and openings into said open region .[.on at
least two.]. .Iadd., the openings extending along about 5% to 50%
of each of the first, second, third and fourth .Iaddend.sides of
said photovoltaic module to reduce wind uplift forces on the
photovoltaic module; joining an insulation layer to said spacer to
create a three-part integral assembly; and installing in the field
said three-part integral assembly as a layer on top of a roofing
membrane without forming penetrations through a roof surface;
whereby the completed assembly resists the forces of wind
uplift.
.[.42. The method of claim 41 further comprising the step of sizing
said openings to comprise about 5% to 50% of the length of at least
two sides of said photovoltaic module..].
.[.43. The method of claim 41 further comprising the step of
providing said openings on all sides of said photovoltaic
module..].
44. The method of claim 41 further comprising the step of
configuring said spacer to have a tapered surface to which said
photovoltaic module is joined, said tapered surface having an angle
of about 5.degree.-30.degree. from horizontal thereby forming said
open region as a tapered open region.
45. The method according to claim 41 further comprising the step of
providing said integral .[.assemblies.]. .Iadd.assembly
.Iaddend.with interengagable lateral edges, and said installing
step .[.is carried out so that.]. .Iadd.comprises installing a
first said integral assembly and a second said integral assembly
adjacent to one another with .Iaddend.said lateral edges of
.[.adjacent integral units are.]. .Iadd.said first integral
assembly and said second integral assembly
.Iaddend.interengaged.
46. The method according to claim 41 further comprising the steps
of: installing a plurality of said integral .[.assemblies.].
.Iadd.assembly .Iaddend.to form an array of .[.said.]. integral
assemblies, said array having a periphery; and joining perimeter
ties to said periphery to stabilize said array.
47. A method of making a photovoltaic roofing assembly, comprising
the following steps: joining a spacer to a photovoltaic module to
create a two-part integral assembly; sizing and positioning said
spacer to provide an open region beneath said photovoltaic module
and openings into said open region to reduce wind uplift forces on
the photovoltaic module; configuring said spacer to support said
photovoltaic module in a manner to form said open region as a
tapered open region; positioning said openings on at least two
sides of said photovoltaic module, said two sides being opposite
sides of said photovoltaic module, said tapered open region
tapering between said openings on said two opposite sides;
installing in the field said two-part integral assembly as a layer
above a roofing membrane; whereby the completed assembly resists
the forces of wind uplift.
48. The method of claim 47 further comprising the step of joining
an insulation layer to said spacer to create a three-part integral
assembly.
49. The method of claim 47 wherein said spacer configuring step is
carried out so .[.that said.]. .Iadd.as to provide a
.Iaddend.tapered surface .[.has.]. .Iadd.having .Iaddend.an angle
of about 5.degree.-30.degree..
50. The method of claim 47 wherein said installing step is carried
out without forming penetrations through, or adhering the unit to,
a roof surface.
51. The method according to claim 47 further comprising the steps
of: installing a plurality of said integral .[.assemblies.].
.Iadd.assembly .Iaddend.to form an array of .[.said.]. integral
assemblies, said array having a periphery; and joining perimeter
members to said periphery to stabilize said array.
52. A photovoltaic assembly comprising: an array of interlocking
photovoltaic units, said array having a perimeter, each said
photovoltaic unit comprising: a photovoltaic module having an upper
surface .Iadd.and first, second, third and fourth sides.Iaddend.;
an insulation layer; a spacer coupling the photovoltaic module and
the insulation layer and defining an open region
therebetween.Iadd., the spacer extending along each of the first,
second, third and fourth sides.Iaddend.; and .[.an.]. access
opening fluidly coupling said upper surface of said photovoltaic
module and the open region.Iadd., the openings extending along
about 5% to 50% of each of the first, second, third and fourth
sides.Iaddend.; and said array having a weight of about two to four
pounds per square foot; whereby the configuration of the
photovoltaic assembly resists wind uplift without the need for roof
surface penetrating elements.
53. The photovoltaic assembly according to claim 52 further
comprising a perimeter assembly joined to said perimeter of said
array.
54. A method for making a photovoltaic roofing assembly comprising
the following steps: selecting a photovoltaic unit having an outer
photovoltaic module, an insulation layer, and a spacer coupling the
photovoltaic module and insulation layer to define an open region
therebetween, the outer photovoltaic module having an outer surface
.Iadd.and first, second, third and fourth sides.Iaddend.; the
selecting step comprising the step of selecting a photovoltaic unit
weighing no more than about four pounds per square foot; placing a
plurality of said photovoltaic units on a roof surface without
securing the units to the roof surface to form an array of said
photovoltaic units; said selecting and placing steps further
comprising the step of providing at least one access opening
.Iadd.extending along about 5% to 50% of each of the first, second,
third and fourth sides .Iaddend.for each said photovoltaic unit
.Iadd.thereby .Iaddend.fluidly coupling the outer surface of said
photovoltaic module and said open region; and surrounding the array
with a perimeter assembly without securing the perimeter assembly
to the roof surface.
.Iadd.55. A photovoltaic assembly comprising: a photovoltaic module
having sides and having upper and lower surfaces; and a spacer
secured to the lower surface of the photovoltaic module, the spacer
being mountable directly to a building rooftop; said spacer sized
and configured to define: an open region beneath said lower
surface, said open region extending between and in contact with the
lower surface and in direct contact with the building rooftop, and
including access openings formed therein for fluidly coupling said
open region to said upper surface; said access openings extending
along at least two sides of said photovoltaic module; whereby wind
uplift forces are resisted when said photovoltaic assembly is
mounted to the building rooftop..Iaddend.
.Iadd.56. A photovoltaic/building rooftop assembly comprising: a
building rooftop; a photovoltaic module having sides and having
upper and lower surfaces; and a spacer secured to the lower surface
of the photovoltaic module to create a photovoltaic assembly, the
spacer being mounted directly to the building rooftop to create a
photovoltaic/building rooftop assembly; said spacer sized and
configured to define: an open region beneath said lower surface,
said open region extending between and in contact with the lower
surface and in direct contact with the building rooftop, and
including access openings formed therein for fluidly coupling said
open region to said upper surface; said access openings extending
along at least two sides of said photovoltaic module; whereby wind
uplift forces are resisted when said photovoltaic assembly is
mounted to the building rooftop..Iaddend.
.Iadd.57. The assembly according to claim 36 further comprising a
perimeter assembly, along said perimeter, interlocking with said
photovoltaic assemblies..Iaddend.
.Iadd.58. The assembly according to claim 1 wherein said
photovoltaic module and spacer have a combined weight of about
1.67-5.0 pounds per square foot..Iaddend.
.Iadd.59. The assembly according to claim 36 wherein said
photovoltaic module and spacer have a combined weight of about
1.67-5.0 pounds per square foot..Iaddend.
.Iadd.60. The assembly according to claim 47 further comprising
limiting the two-part integral assembly to a combined weight of
about 1.67-5.0 pounds per square foot..Iaddend.
.Iadd.61. The assembly according to claim 55 wherein said
photovoltaic module and spacer have a combined weight of about
1.67-5.0 pounds per square foot..Iaddend.
.Iadd.62. The assembly according to claim 56 wherein said
photovoltaic module and spacer have a combined weight of about
1.67-5.0 pounds per square foot..Iaddend.
.Iadd.63. The assembly according to claim 36 wherein said
photovoltaic module and spacer have a combined weight of about two
to four pounds per square foot..Iaddend.
.Iadd.64. The assembly according to claim 47 further comprising
limiting the two-part integral assembly to a combined weight of
about two to four pounds per square foot..Iaddend.
.Iadd.65. The assembly according to claim 55 wherein said
photovoltaic module and spacer have a combined weight of about two
to four pounds per square foot..Iaddend.
.Iadd.66. The assembly according to claim 56 wherein said
photovoltaic module and spacer have a combined weight of about two
to four pounds per square foot..Iaddend.
.Iadd.67. The assembly according to claim 19 wherein said
photovoltaic assembly comprises means for interlocking one said
photovoltaic assembly to another said photovoltaic
assembly..Iaddend.
.Iadd.68. The assembly according to claim 33 wherein said
photovoltaic roofing assembly comprises means for interlocking one
said integral unit to another said integral unit..Iaddend.
.Iadd.69. The method according to claim 47 wherein the installing
step comprises interengaging adjacent integral
assemblies..Iaddend.
.Iadd.70. The method according to claim 54 wherein the placing step
comprises interengaging adjacent photovoltaic units..Iaddend.
.Iadd.71. The assembly according to claim 55 wherein said
photovoltaic assembly comprises means for interlocking one
photovoltaic assembly to an adjacent photovoltaic
assembly..Iaddend.
.Iadd.72. The assembly according to claim 56 wherein said
photovoltaic/building rooftop assembly comprises means for
interlocking one said photovoltaic assembly to another said
photovoltaic assembly..Iaddend.
.Iadd.73. The assembly according to claim 1 wherein said assembly
further comprises means for resisting forces of wind uplift
sufficiently to eliminate the need for penetrations of the building
rooftop..Iaddend.
.Iadd.74. The assembly according to claim 19 wherein the
photovoltaic assembly is mountable to a building roof without
forming penetrations through the building rooftop..Iaddend.
.Iadd.75. The assembly according to claim 31 wherein the
photovoltaic roofing assembly is disposed on the roofing membrane
without forming penetrations through the roofing
membrane..Iaddend.
.Iadd.76. The assembly according to claim 36 wherein the
photovoltaic assemblies are mountable to a building rooftop without
forming penetrations through the building rooftop..Iaddend.
.Iadd.77. The method according to claim 47 wherein the installing
step is carried out without forming penetrations through the
roofing membrane..Iaddend.
.Iadd.78. The assembly according to claim 55 wherein the
photovoltaic assembly is mountable to the building rooftop without
forming penetrations through the building rooftop..Iaddend.
.Iadd.79. The assembly according to claim 56 wherein the
photovoltaic assembly is mounted to the building rooftop without
forming penetrations through the building rooftop..Iaddend.
.Iadd.80. A photovoltaic assembly comprising: a building rooftop; a
photovoltaic module having sides and having upper and lower
surfaces; and a plurality of spacers secured to the lower surface
of the photovoltaic module and supported by the building rooftop;
said spacers sized and configured to define: an open region beneath
said lower surface, said open region extending between and in
contact with the lower surface and in direct contact with the
building rooftop, and including access openings formed therein for
fluidly coupling said open region to said upper surface; said
access openings extending along at least two sides of said
photovoltaic module; whereby wind uplift forces are resisted when
said photovoltaic assembly is mounted to the building
rooftop..Iaddend.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to U.S. Pat. No. 5,316,592, issued May
31, 1994 to Dinwoodie, and U.S. Pat. No. 5,505,788, issued Apr. 9,
1996 to Dinwoodie, the disclosures of which are incorporated by
reference.
BACKGROUND OF THE INVENTION
This invention generally relates to a photovoltaic roofing
assembly, and in particular to a lightweight photovoltaic roofing
assembly requiring no roofing penetrations and which resists wind
up-lift due to specialized component geometry and by acting as an
integral assembly.
As the cost of solar cells declines, the non-solar cell components
necessary for a functioning photovoltaic system begin to dominate
the overall system costs. For this reason, there is a growing trend
to develop photovoltaic assemblies which eliminate or reduce
non-solar cell components, and where the photovoltaic cell
displaces conventional building components. Special care must be
taken to ensure that new products based on photovoltaic materials
remain safe with respect to environmental factors such as
wind-loading and environmental stresses.
A prior art photovoltaic roofing assembly is shown in U.S. Pat. No.
4,886,554 issued Dec. 12, 1989 to Woodring et al. Woodring's
assembly includes a plurality of insulation blocks disposed as a
layer on top of a roofing membrane, a plurality of concrete pavers
disposed as a layer on top of the plurality of insulation blocks,
and a plurality of photovoltaic cells, each supported on a
respective paver. A key feature of Woodring's assembly is the
attachment of the solar cell to the supporting paver. But such
attachment suffers from several disadvantages:
a) by including a roofing paver, the assembly is more complicated
than necessary and more costly to manufacture.
b) the assembly does not employ a method by which to limit the
temperatures experienced by the solar cells and other components.
Solar cells are known to decline in efficiency with increasing
temperatures. Hence, by offering no mechanism for temperature
abatement, the assembly will operate less efficiently, with unknown
long-term effects due to high temperature exposure.
c) by placing both a concrete paver and photovoltaic module onto
the insulation block, the insulation block is inhibited from
ventilating and expiring moisture. As a result, upon exposure to
moisture, the insulation block takes longer to dry out, thus
reducing its insulating value and degrading the integrity of the
insulation block over time.
d) the assembly has multiple modes of potential failure, which
include the paver component and its means of bonding. These
components will be subjected to 20-30 years of an exposed and harsh
weather environment at elevated temperatures. Any form of
delamination is unacceptable. Delamination would cause dislocation
of solar cells due to wind loading, and potential exposure of the
insulation and membrane layers below.
Another prior art solar roofing assembly is shown in U.S. Pat. No.
4,674,244 issued Jun. 23, 1987 to Francovitch. Frankovitch's
assembly includes a roof substrate which is substantially flat, an
insulation structure thereon having an inclined surface, an
elastomeric membrane over the substrate and the structure, the
membrane being applied to and supported by the substrate and
structure, and supporting an array of photocells. A key feature of
this assembly is the attachment of the solar cell directly to the
roofing membrane. By such attachment, this assembly suffers from
several disadvantages:
a) the assembly does not employ a method by which to limit the
temperatures that will be experienced by the solar cells and
roofing membrane, thus reducing the efficiency of the solar cells
and reducing the life of the roofing membrane.
b) the assembly has multiple modes of potential failure, which
include failure due to thermal stresses on the roofing membrane and
its means of bonding.
c) the assembly requires roof fasteners which penetrate the
protective roofing membrane, which make the installation much more
complicated and more costly than is necessary. In addition, such
penetrations increase the risk of water leakage, with consequent
damage to the building and its contents.
Other patents related to a photovoltaic roofing assembly include
U.S. Pat. Nos. 4,835,918 issued Jun. 6, 1989 to Dippel; 4,189,881
issued Feb. 26, 1980 to Hawley; 3,769,091 issued Oct. 30, 1973 to
Leinkram et al; 4,040,867 issued Aug. 9, 1977 to Forestieri et al;
4,321,416 issued Mar. 23, 1982 to Tennant; 4,860,509 issued Aug.
29, 1989 to Laaly et al; 5,092,393 issued March, 1992 to Nath et
al; 5,112,408 issued May, 1992 to Melchior, 4,389,533 issued Jun.
21, 1983 to Ames; 4,677,248 issued Jun. 30, 1987 to Lacey;
5,338,369 issued Aug. 16, 1994 to Rawlings; German patent No. DE
3611542 A1 issued Apr. 5, 1986 to Cohausz et al.; and Japanese
patent No. 3-200376 issued Sep. 2, 1991.
SUMMARY OF THE INVENTION
According to the present invention, a lightweight, self-ballasting
solar cell roofing assembly is preferably formed with two portions.
One portion consists of a plurality of photovoltaic modules,
together with spacers which rest on a conventional building
rooftop. The spacers are preferably pre-formed and are sized and
configured to provide passageways beneath the photovoltaic modules
extending from at least two sides of the modules to reduce uplift
forces on the modules. The photovoltaic modules with spacers
preferably have interlocking edges or corners. The second portion
is a means of perimeter securement which avoid roof membrane
penetrations, such as the use of roofing pavers.
The photovoltaic module portion is situated over the building
rooftop in a manner to be exposed to solar radiation and
electrically connected for transport of electricity. The paver
portion is situated over the same building and interlocks with the
photovoltaic modules with spacers. Other means of perimeter
securement are possible, including placing metal flashing along the
edge of the perimeter modules and connecting the flashing
end-to-end around the array perimeter, or adhering said flashing to
the roofing membrane. The photovoltaic module performs the multiple
functions normally provided by a roofing paver, including ballast,
UV protection, and weather protection for the membrane and
insulation layers below. Together the two portions serve the dual
function of a self-ballasted protective roof covering and an
assembly for the collection of radiant energy.
In an alternate embodiment, the solar cell roofing assembly is
formed with three portions. The first portion consists of a
plurality of insulation blocks which are situated on a conventional
roofing membrane. The second portion consists of a plurality of
photovoltaic modules, together with spacers which rests on the
plurality of insulation blocks. The insulation blocks with
photovoltaic modules and spacers have interlocking edges. The
photovoltaic module performs multiple functions, including ballast,
UV protection, and weather protection for the membrane and
insulation layers below. A third portion is a means of perimeter
securement, such as metal flashing or conventional roofing pavers,
located at the perimeter of arrays of photovoltaic modules and
tying the entire array together as an integral assembly. Other
means of perimeter securement are also possible. Together the three
portions serve the dual function of a protected membrane roofing
system and an assembly for the collection of radiant energy.
Accordingly, the present invention provides several features and
advantages:
a) a detailed geometry for lightweight photovoltaic roofing tiles
and assemblies which ensure adequate resistance to wind uplift
forces acting on a building rooftop while eliminating the need for
roof membrane penetrations for holddown;
b) a roofing assembly which weighs roughly one-sixth to one-third
that of conventional ballasted roofs, thus reducing or eliminating
the need for added building structural support;
c) an assembly which works with virtually all built-up and single
ply membranes, and an assembly which can be free of chlorinated
fluorocarbon;
d) a simple and low-cost photovoltaic roofing assembly, where
components within the product provide multiple functions as a
roofing component, including ballast, weather protection, and UV
protection for the insulation and waterproof membrane below;
e) a photovoltaic roofing assembly which enjoys ease of fabrication
due to its simple construction;
f) a photovoltaic roofing assembly that displaces the costs of
conventional roofing materials and their installation, thereby
enhancing the value of the photovoltaic portion as a synergistic
building component;
g) a product with minimal modes of potential failure;
h) a roofing assembly which yields social benefits by making
photovoltaic technology more cost competitive. This facilitates
transition to a clean, renewable energy economy, and helps to
mitigate air pollution and global warming.
The foregoing and other features and advantages of the invention
will be more fully apparent from the description of the preferred
embodiments of the invention when read in connection with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A to 1D show views of one embodiment of the invention with
spacers resting directly on a roofing membrane and with spacer
geometry designed to minimize wind uplift on the overall
assembly;
FIGS. 2A to 2D show views of a second embodiment of the invention,
whereby the invention shown in FIG. 1 is a panelized system of
photovoltaic modules;
FIGS. 3A to 3D shows views of an alternate embodiment of the
invention whereby spacers are attached to an insulation block and
arranged in a geometry which minimizes wind uplift on the overall
assembly, the outline of the location of the photovoltaic module
shown in dashed lines in FIG. 3D;
FIGS. 4A to 4B show views of various means of perimeter securement
installed according to the invention; and
FIG. 5 shows a plan view of a building with a photovoltaic roofing
assembly installed according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Description of FIGS. 1A-1D:
Spacer Geometry Directly on Roofing Membrane
FIG. 1A shows a sectional view of a photovoltaic roofing assembly.
The assembly includes a plurality of photovoltaic modules 104, 106,
108, a plurality of pre-formed spacers, pedestals, or supports 112,
114, 116, 118, 120, 122 which are respectively disposed below the
plurality of photovoltaic modules 104, 106, 108 and integral
therewith, or fixedly connected thereto. Spacers 112, 114, 116,
118, 120, 122 are disposed on top of a roofing membrane 102.
Photovoltaic modules 104, 106, 108 and the associated spacers
112-122 define open regions 123 beneath the photovoltaic
modules.
Membrane 102 is supported on conventional roof framing (not shown),
and may be attached thereto by conventional methods, such as
fasteners or adhesives. Membrane 102 may also rest directly on an
insulation block which is supported on conventional roof framing.
Modules 104, 106, 108 are electrically connected using electrical
conductors (not shown) and are arranged in an array of modules.
Each of modules 104, 106, 108 has at least one photovoltaic cell.
Examples of photovoltaic modules include those incorporating
thin-film deposition onto glass, stainless steel or ceramic
substrates and manufactured by such companies as Solarex
Corporation, United Solar Systems Corporation, Energy
Photovoltaics, Inc. and Astropower, Inc., and modules of single or
polycrystalline silicon cells such as those manufactured by
Astropower, Inc., Siemens Solar Industries, and Solarex
Corporation.
FIG. 1B shows a plan view of a detail of the assembly whereby
pre-formed spacers 116, 118, 124, 126 are disposed on top of
membrane 102 and provide support along the edges of module 106 to
which they are fixedly connected or made integral. FIG. 1A shows
dimension h representing the distance between the module and the
roofing membrane. The assembly has preferred dimensions whereby h
measures 2.5 cm (1 inch) to 15.2 cm (6 inches), depending upon the
temperature to which the module and other components are to be
limited. The photovoltaic modules are preferably sized in the range
of 61 cm (2 feet) by 122 cm (4 feet) to 122 cm (4 feet) by 244 cm
(8 feet), which dimension has been determined from wind tunnel test
evaluation to be preferred from the standpoint of minimizing wind
uplift and which dimension can be readily handled by a roofing
installation crew.
FIG. 1C shows a sectional view of an alternate detail of the
assembly whereby spacers 130, 132, 134 have a tapered profile and
are disposed on top of membrane 102 and provide support for modules
104, 106, 108 to which they are fixedly connected or made integral.
Spacers 130, 132, 134 may be made of glass, concrete, plastic
(vacuum-formed or other), insulation block, integral concrete over
insulation block (such as the product known as Lightguard, by T.
Clear Corporation), or other material.
In FIGS. 1C and 1D spacer 132 is shown pre-formed with openings
150, 152 which enable free air exchange at the low and high sides
of module 106 to the underside of the module 106. Such free air
exchange with the spacer geometry shown has been determined through
wind-tunnel testing to aid in the instantaneous equilibration of
air pressures between the top and bottom side of module 106, thus
reducing net forces of wind uplift.
In FIGS. 1C and 1D spacer 132 is shown pre-formed with a tapered
profile 140 between its highest point along the high edge of module
106 extending downward to the low edge of adjacent module 108.
Tapered profile 140 serves as an aerodynamic wind-block, causing
wind which is traveling from the right in the drawing to flow over
the top of module 106, and obstructing its entry to the backside of
module 106.
In FIGS. 1C and 1D spacer 132 preferably has a tongue profile 160
along two edges and a groove profile 162 along its other two edges
such that spacer 132 interlocks with adjacent spacers. In this way,
interlocking joints are formed between adjacent integral assemblies
for better resistance to wind uplift. However, any means of
integral locking is possible.
The preferred method of manufacture of the solar roofing assembly
is indicated as follows: Modules 104, 106, 108 are added to, bonded
to, or otherwise attached to, respective spacers 112, 114, 116,
118, 120, 122, 124, 126 (or for sloped modules, spacers 130, 132,
134) in the manufacturing plant or in the field. A roofing membrane
is placed on a roof. The modules and spacers are placed in arrays
on top of the roof membrane. Roofing pavers are situated around the
perimeter of photovoltaic modules and interlock at the perimeter of
the modules. Such construction results in a simple, readily
assembled roofing assembly which can be lightweight while resisting
the forces of wind uplift.
The advantages of the foregoing assembly include:
1. The assembly is lightweight
(9.76-19.53 kg/sq. m or 2-4 pounds/sq. ft.) relative to
conventional roofing ballast (48.8-73.2 kg/sq. m or 10-15
pounds/sq. ft.), relying on a combination of weight, edge to edge
connection, and spacer geometry to resist the forces of wind
uplift.
2. The photovoltaic roofing assembly, which can be used on a flat
or mildly sloping roof, minimizes water leakage through the
roof.
3. The photovoltaic module provides multiple functions as a roofing
component, including ballast, weather protection, and UV protection
for the membrane layer below.
4. By displacing roofing components and their installation, the
value of the photovoltaic module is enhanced, thereby enhancing the
cost-competitiveness of energy from a clean and renewable
resource.
5. The cost of installation of the assembly is minimized due to
ease of fabrication and simple construction. Quality control is
maximized by using shop assembly.
6. The solar roofing modules are reusable. They can be readily
disconnected and reassembled onto other rooftops. Spacers 112, 114,
116, 118, 120, 122 of the assembly can take several forms, but
preferably follow the periphery of each of modules 104, 106, 108
while having openings that are between 5% to 50% of the edge length
of the module. This geometry has been determined to be preferred as
a result of extensive wind-tunnel testing, and results in near
instantaneous and uniform equilibration of pressures at the top and
bottom side of modules 104, 106, 108 under conditions of high
windspeed, thus reducing net uplift forces due to wind-loads.
Description of FIGS. 2A-2D:
Spacers as Panelized System
FIGS. 2A-2D show section and plan views of a second embodiment of
the invention. In FIG. 2A, the assembly includes a plurality of
photovoltaic modules 204, 206, 208, 210, 212, a plurality of
pre-formed spacers 220, 222, 224 which are respectively disposed
below modules 204, 206, 208, 210, 212 and integral therewith, or
fixed thereto. The spacers 220, 222, 224 rest on pedestals or
supports 240, 242 which are disposed on top of a roofing membrane
202. Alternatively, spacers 220, 222, 224 may rest directly on
membrane 202.
Spacers 220, 222, 224 of the assembly can take several forms,
including c-channels, plastic tube, or metal bar.
FIG. 2B shows a plan view of a detail of the assembly whereby
spacers 220, 220', 222, 222', 226, 226' provide support for modules
204, 206, 208, 210, 212, 214, 216, 218 to which they are fixedly
connected or made integral. Spacers 220, 220', 222, 222', 226,
226', 228, 228' also ensure consistent spacing between PV modules
and enable water drainage.
FIG. 2C shows a sectional end-view of the assembly whereby spacers
228, 222', 222, 226 are disposed on top of pedestals 240, 240'
which are disposed on membrane 202. Pedestals 240, 240' may be made
of concrete, plastic, insulation block, or other material and
interlock with spacers 228, 222, 222', 226. Whereas FIG. 2C shows
interlocking by intersecting c-channels, any means of interlocking
is possible.
In FIG. 2D, the assembly of FIG. 2A is modified by sloping modules
204, 206, 208, 210, 212 and introducing windspoils 260, 262, 264,
266, 268 in order to deflect surface winds from entering below
modules 204, 206, 208, 210, 212.
The advantages of the assembly of FIG. 2, which are in addition to
the advantages of the assembly shown in FIG. 1, include:
1. Inclined photovoltaic modules 204, 206, 208, 210, 212 operate at
a relatively high efficiency, due to their top surfaces being close
to a plane normal to solar radiation.
2. By inclining the photovoltaic modules, natural convection using
outside air as a convection fluid is enhanced, due to the
facilitation of convective currents on the backside of a planar
surface when that surface is inclined.
Description of FIGS. 3A-3D:
Spacer Geometry over Insulation Block
FIG. 3A shows a sectional view of a photovoltaic roofing assembly.
The assembly includes a plurality of photovoltaic modules 304, 306,
308, a plurality of pre-formed spacers, pedestals, or supports 312,
314, 316 which are respectively disposed below the plurality of
photovoltaic modules 304, 306, 308 and integral therewith, or
fixedly connected thereto. Spacers 312, 314, 316 are disposed on
top of insulation blocks 320, 322, 324 which are disposed on a
roofing membrane 302.
FIG. 3B shows a plan view of a single roofing tile 301, made of
insulation block 322 and spacers 314, 314', 315, 315'. The outline
of the position of photovoltaic module 306 is shown in dashed
lines. Spacers 314, 315' preferably follow the periphery of module
306 while leaving openings to the interior of tile 301 that are
between 5% to 50% of the edge length of module 306. This geometry
results in the formation of negative interior pressures under
conditions of high windspeed, thus reducing net uplift forces due
to wind-loads, as determined by wind-tunnel testing.
Looking at FIG. 3B, wind tunnel investigations determined that the
preferred mode of operation is where spacers are normal to the
direction of the wind and following close to the perimeter of the
module. Poor performance is experienced where there is continuous
blocking of the interior cavity around the perimeter of the module.
Optimal holddown occurs where the modules have some small degree of
opening to the interior cavity, in the range of 10%-30%. In the
latter configuration, the best performance is experienced when the
ratio of d/h is in the range of 0.2-0.6, or greater than 1.20.
FIG. 3C shows a sectional view of an alternate detail of the
assembly whereby tile 301' consists of photovoltaic module 306
supported by spacer 350 resting on insulation block 340. Insulation
block 340 has a tapered profile in order to orient module 306 in
the direction of increased sun exposure. Alternatively, spacer 350
could have a tapered profile. Insulation block 340 is shaped such
that its top-most portion blocks the entry of surface winds from
entering beneath module 306.
Looking at FIG. 3C, wind tunnel investigations determined that
system performance is relatively insensitive to module slope where
slope is in the range of 5.degree.-12.degree.. Better performance
was experienced where the shape of the cavity beneath the PV module
is triangular, as in FIG. 3C, rather than rectangular.
FIG. 3D shows a plan view of tile 301' whereby spacers 350, 352,
354 are located below module 306 and fixedly connected thereto,
thus enabling free air exchange at the low and high sides of module
306. Such free air exchange with the spacer geometry shown has been
determined through wind-tunnel testing to aid in the instantaneous
equilibration of air pressures between the top and bottom side of
module 306, thus reducing net forces of wind uplift.
In FIGS. 3C and 3D spacer 340 is shown pre-formed with a tapered
profile 356. Tapered profile 340 serves as an aerodynamic
wind-block, causing wind which is traveling from the right in the
drawing to flow over the top of module 306, and obstructing its
entry to the backside of module 306.
The advantages of the foregoing assembly include, in addition to
the advantages of FIG. 1:
1. The spacer geometry serves to reduce to net forces of wind
uplift, thus enabling the assembly to be lightweight (9.76-19.53
kg/sq. m or 2-4 pounds/sq. ft.) relative to conventional roofing
ballast (48.8-73.2 kg/sq. m or 10-15 pounds/sq. ft).
2. The roofing tiles provide roofing insulation as well ballast,
weather and UV protection for the membrane layer below.
Description of FIGS. 4A-4B:
Perimeter Securement
FIGS. 4A-4B shows sectional views of alternate means of perimeter
securement for the roof tile system. FIG. 4A shows metal flashing
410 running the perimeter of an array of roof tiles and
interlocking with insulation block 404. Metal flashing 410 is
shaped to accept electrical conductors (not shown) which run the
perimeter of the assembly. FIG. 4B shows concrete paver 412
interlocking with insulation block 404. Whereas FIG. 4B shows
interlocking by tongue and groove, any other means of interlocking
is possible, including the use of metal z-flashing between the
insulation block and paver.
Description of FIG. 5
Plan View of the Photovoltaic Roofing Assembly
FIG. 5 shows a perspective view of the photovoltaic roofing
assembly where solar roofing tiles 504 form an array 502 which is
situated on a building rooftop. Perimeter securement 510 runs the
perimeter of array 502 and ties the roofing tiles 504 into an
integral assembly.
While the invention has been described in its preferred
embodiments, it is to be understood that the words which have been
used are words of description rather than limitation and that
changes may be made within the purview of the appended claims
without departing from the true scope and spirit of the invention
in its broader aspects.
The present invention provides a simple, efficient, quickly
installed, reusable, and low-cost solar module assembly for roofs
or other flat or mildly sloping surfaces whereby internal
geometries of the roofing tile components minimize the net forces
of wind uplift.
While the above description contains many specificities, these
should not be construed as limitations on the scope of the
invention, but rather as an exemplification of one preferred
embodiment thereof. Many other variations are possible. For
example, the integral solar module unit consisting of a solar
module bonded to insulation block can be utilized independent of a
roofing membrane. As a further example, the solar roofing assembly
may include an additional layer consisting of fabric or other
material disposed above the roofing membrane and below the
photovoltaic module with spacers, which layer may provide an
additional protective barrier for the roofing membrane and/or
slipsheet.
As a further example, the solar modules with pedestals or spacers
may include leveling plates placed under or over the pedestals or
spacers for leveling the photovoltaic modules, or for achieving a
pre-determined slope of the photovoltaic modules.
As a further example, the insulation block may be coated with an
intumescent coating or other means of fireproofing in order to
achieve a desired fire rating as a building roofing assembly.
As a further example, whereas the edge to edge connection between
adjacent modules was often shown as a tongue and groove assembly,
any means of edge connection is possible, including mechanical
clips, adhesives, "skewer" inserts which penetrate the insulation
block, and other means. In addition, the positive connection
between modules may be accomplished as follows. The photovoltaic
modules may rest on spacers which in turn rest on insulation board
which is loose laid on the roofing membrane. The photovoltaic
modules may then span and be bonded to adjacent insulation blocks
which would provide a positive connection between adjacent
insulation blocks and adjacent photovoltaic modules. The latter
would assist the assembly in resisting the forces of wind
uplift.
As a further example, the top of all insulation blocks may be
painted with a paint which is opaque to ultraviolet radiation,
thereby lengthening the life of the insulation block in
applications where the photovoltaic module is not opaque to
ultraviolet radiation.
As a further example, the spacers need not be made integral with
the photovoltaic module in the shop, but may be laid in the field
as stringers and the PV modules attached thereto in the field.
As a further example, the angle of the photovoltaic module can
range from about 0.degree.-30.degree., preferably about
5.degree.-30.degree., and more preferably about
5.degree.-12.degree..
Accordingly, the scope of the invention should be determined not by
the embodiments illustrated, but by the appended claims and their
legal equivalents.
* * * * *