Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE OF THE INVENTION: SOLAR PANEL SECURING ASSEMBLY FOR SHEET
METAL SLOPING ROOFS
FIELD OF THE INVENTION
The present invention generally relates to securing spacer elements for
rooftop mounting
of assemblies, and more specifically for sloping rooftops covered with
corrugated sheet metal.
BACKGROUND OF THE INVENTION
Given the rapid climb of conventional energy costs and given the growing
concerns about
the environment, the interest in alternative energy sources that are both
renewable and clean is
growing steadfastly. In this regard, solar power is considered to be one
promising solution since
it is not only clean and renewable, but also plentiful: every day the sun hits
the earth with
roughly 20 000 times the current daily energy consumption by humankind.
The two main technologies currently used to harness the power of the sun are
Concentrating Power Systems (CPS) and Photovoltaic (PV) Panels. Concentrating
Solar Power
(CSP) systems use lenses or mirrors and sun tracking systems to focus a large
area of sunlight
into a small beam. The concentrated heat is then used as a heat source for a
conventional power
plant. While these systems may be very efficient, they are also cumbersome and
are thus
typically installed on open ground, thus monopolizing expensive land space.
Photovoltaic panels
are assemblies of photovoltaic cells (also called solar cells or photoelectric
cells), which are
electrical devices that convert the energy of light directly into electricity
by the photovoltaic
effect. They come in the form of thin rectangle boxes that can be assembled
into grids of various
sizes. Given their smaller size and weight, they can be installed on a broader
range of locations
relative to CSP systems.
PV panels are commonly found over roofs because their height usually provides
them
with better exposure to sun rays than open ground. Another advantage resides
in the fact that
rooftops are often unexploited otherwise, so that using this empty or "wasted"
space can thus
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free open ground for better use. Furthermore, since roofs are by their nature
part of buildings,
hooking the PV panels directly to the existing electric facilities is often
easier than with an open
ground PV installation requiring some excavation work, foundation building and
more complex
outdoors wiring.
A roof construction typically consists of footings of various shapes and an
outer
weatherproof skin or covering. A simple ridged roof may consist of declined
rafters that rest on
vertical wall plates on top of each wall. The top ends of the rafters meet at
the horizontal ridge
plate or ridge beam. Horizontal purlins are fixed to the rafters to support
the roof covering.
Heavier under purlins are used to support longer rafter spans. The beams or
ceiling joists, are
connected between the lower ends of opposite rafters to prevent them from
spreading and forcing
the walls apart. Collar beams or collar ties may be fixed higher up between
opposite rafters for
extra strength.
Corrugated sheet metal panels are commonly used as sloping roof weatherproof
covering
material. A single corrugated sheet metal panel is typically composed of a
series of large web
sections separated by a series of thin raised rib sections, each panel
starting and ending with a rib
section. When assembled to form roof covering, the ending rib of the new panel
being installed
overlaps on the ending rib of the panel already in place, thereby providing a
gravity borne
mechanical seal. The sheet metal panels are fixed to the roof's furring strips
or studs using lag
screws placed over the ribs at sheet junction points to minimize leakage
risks, the water being
drained over the lowered section.
On most roofs, the trusses are spaced every 24 inches. On metal roofs, the
metal sheets
are screwed to the structure on the ribs to prevent leak problems. The ribs of
a sheet metal roof
are in many cases spaced at 9 inches. A metal sheet is usually 36 inches wide.
The probability
that the ribs of the sheet metal roof will be directly over a truss (rafters)
is low. To ensure a good
long term seal, the lag bolts of the mounting system have to be secured on top
of sheet metal
ribs. The number of roof clamps to be installed depends on the type of
building structure and the
size of the furring strips (studs). Furring strip studs are weaker than
trusses, so more fixtures
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must be added accordingly. There are lots of different metal sheets with
different rib shapes and
sizes. Proper sealing with a good structural integrity is important. The metal
sheets are usually
fastened to furring strips or studs. These wood members are not always the
same size and each
consecutive pair thereof is not spaced the same distance relative to one
another.
Installing PV panels on sloping roof can be challenging because not only are
roofs
generally hard to access and dangerous to operate on by workers, but they are
also exposed to
weathering elements, including heavy winds, rain or snow, and large
temperature gradients. Such
installations must therefore take into account of not only the weight of the
panels and their
support structure, but of the combined loads imposed on the roof
infrastructure such as the wind
load, the rain and snow loads, other equipment load, and so forth.
Furthermore, PV structural elements of the panels tend to accumulate heat when
exposed
to sunlight. Unfortunately photovoltaic performance degrades as their
temperature increases.
Excess heat can also lead to sheathing material degradation that can reduce
the roof effectiveness
in protecting the building. For example, excess heat could lead to sheet metal
paint degradation,
exposing the metal to corrosion, thus compromising the roof's integrity.
Excess thermal loads
can be mitigated by providing spacer elements between the PV panels and the
rooftop sheathing,
so that natural ventilation occurs.
However, it was found by the present inventor that such prior art spacer
elements
provided overall weak ventilation capabilities around the PV panels
overhanging rooftops.
Finally, installing any equipment on a roof can increase water leakage hazard
inside the
building because of water, snow or ice accumulations that can lead to water
levels rising above
their usual levels, therefore exposing sections of the roof normally not or
less exposed to water.
In the case of sloping sheet metal roof, this could be water rising above a
sheet metal rib with
improperly sealed fastening screws. Moreover PV installations will likely
require additional
holes to be pierced across the roof's sheathing material in order to reach the
underlying
infrastructure to insure the proper anchoring of the PV panels support
assembly. This evidently
increases the risks of water leaking into the building.
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It is recommended to wear gloves during PV installations, to prevent
electrical
hazard accidents.
SUMMARY OF THE INVENTION
The invention relates to a spacer element for supporting and retaining a
peripheral edge
portion of a photovoltaic panel assembly spacedly over a rooftop corrugated
sheet supported by
underlying rooftop frame elements, said spacer element including: a unitary
main body being
generally U-shaped and defining a base leg and two opposite first and second
legs, said first leg
being shorter than said second leg and having an oblong bore, said second leg
having an
intermediate ridge section extending parallel to said oblong bore and toward
the plane of said
first leg and forming a web and two diverging walls, said web closely spaced
from said first leg
parallel thereto, a screw aperture made centrally into said web and axially
clearing said shorter
first leg, said first and second legs defining inner walls facing each other
and opposite outer
walls, said second leg intermediate ridge section outer wall for abutting in
conformingly fit
fashion against a longitudinal rib of the corrugated sheet, a fraction of said
first leg outer wall for
supporting a peripheral edge portion of the photovoltaic panel assembly; a
screw member
engaging said main body screw aperture for anchoring said main body to the
supporting rooftop
frame elements through the corrugated sheet; an L-shape bracket, defining
inner and outer legs,
said bracket inner leg abutting against said main body first leg outer wall,
said bracket outer leg
for abutting sideways against a registering portion of the peripheral edge
portion of photovoltaic
panel assembly; and a first nut and bolt member engaging said first oblong
bore and adjustably
interlocking said L-shape bracket to said spacer element main body wherein
said L-shape bracket
is movable relative to said main body along an axis parallel to said main body
ridge section for
adjustment of the photovoltaic panel assembly in a plane parallel to the
rooftop corrugated sheet.
Preferably, there is further included a second oblong bore made into said
bracket outer
leg and extending parallel to the plane of said main body base leg, and a
second nut and bolt
member engaging said second oblong bore for releasably adjustably interlocking
said L-shape
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bracket to a registering portion of the peripheral edge portion of
photovoltaic panel assembly,
wherein said second nut and bolt member is movable along an axis orthogonal to
the plane of
said main body shorter first leg, for providing adjustable displacement
transversely between the
photovoltaic panel assembly and the rooftop corrugated sheet.
5 A flexible waterproof membrane, fixedly applied to said second leg outer
wall, said
membrane having a bore registering with said screw aperture, said screw member
further
engaging said membrane bore.
BRIEF DESCRIPTION OF THE FIGURES OF DRAWINGS
In the annexed drawings:
Figure 1 is an isometric view of the rooftop portion of a house shown partly
broken for
the clarity of the view, and equipped with an array of PV panels secured
thereto by spacer
elements according to one embodiment of the invention;
Figure 2 is an enlarged view of a corner portion of the roof, PV panels and
spacer
elements of figure 1;
Figure 3 is a view of still enlarged scale of the rooftop portion, PV panels
and spacer
elements of figure 2;
Figure 4 is an exploded view of a spacer element, sealing membrane, corrugated
sheet
portion, and furring strips from figure 3;
Figure 5 is a view of en enlarged scale of the spacer element of figure 4;
Figure 6 is a view similar to figure 5 but further showing an attachment bolt
and the
integral adjustable height connector securing the PV panel peripheral frame
(only a portion
thereof being illustrated) to the spacer element;
Figure 7 is an edge view of the elements of figure 6;
Figure 8 is a cross sectional view of the elements of figure 7, without the
attachment bolt;
and
Figure 9 is a cross sectional view taken along line 9-9 of figure 7.
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DETAILED DESCRIPTION OF THE DRAWINGS
Figure 1 shows a building 20 comprising an upright side wall 24, and a sloping
roof 22
partially supported by upright walls 24. Sloping roof 22 has a top edge 28
being the ridge of roof
22 and extending horizontally from a first end 28a to a second end 28b, a
bottom edge 30 located
at the bottom of roof 22 near the junction with upright wall 24 and extending
from a first end 30a
to a second end 30b, and inclined opposite lateral edges 32, 34 extending
respectively from the
top edge first and second ends 28a, 28b to the bottom edge first and second
ends 30a, 30b.
Sloping roof 22 is covered with a corrugated sheet metal sheathing 36 (figure
2, 4)
comprising a series of raised rib sections 36a separated by lowered base
sections 36b each
downwardly extending from the roof top edge ridge 28 to the roof bottom edge
30. Sloping roof
22 comprises a set of horizontal purlins or furring strips 90 (see figure 2)
extending from lateral
edge 32 to lateral edge 34 and placed at regular intervals between the roofs
top and bottom edges
28, 30 to provide a support base for the installation of sheet metal sheathing
36.
Sloping roof 22 is equipped with a photovoltaic (PV) panel array 29 comprising
one or
more PV panels 33, 33', 33", arranged in a full or partial grid formation. PV
panels 33, 33',
33", ... are supported at the periphery of PV panel array by underlying
extrusion support rails
100, 102, and at intermediate sections by additional transverse rails 104
spacely parallel to rails
102. PV panel array 29 is fixed on roof 22 with a PV panel mounting spacer
system 31 further
depicted in figures 2 and 3.
According to a preferred embodiment of the invention illustrated in figures 4
to 7 of the
drawings, PV panel mounting spacer system 31 includes a number of spacer
mounting elements
40, preferably forming generally U-shaped sheet metal fixtures. Each spacer
element 40 defines
a web 42, from which transversely projects a spacer leg 48, at one edge
thereof. Web 42 further
includes an intermediate ridge section 46 also transversely projecting
therefrom toward leg 44
spacedly from leg 48. Ridge section 46 is sized and shaped to conformingly fit
over
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corresponding rib section 36a of corrugated sheet 36. Ridge section 46
includes a raised flat
section 46A, orthogonal to the plane of leg 48 and two diverging sections 46B,
46C. Ridge
raised section 46A has a central lag bolt bore 49, for passage by a bolt 74
(figure 6). A seat leg
44 transversally projects from the longitudinal edge of leg 48 opposite web 42
and in
overhanging fashion relative to web 42, but extending slightly short of the
longitudinal axis of
bore 49 for clearing same. Seat leg 44 includes an oblong bore 47 extending
parallel to the
longitudinal axis of raised ridge section 46A. Seat leg 44 is sized and shaped
to provide seating
support at an exposed outer face thereof 44A (opposite web 42) for a portion
of PV panel
assembly peripheral rail 100 or 102 (figure 3). As shown in figure 3, seat leg
44 preferably
includes structural extruded projections 44B, projecting toward the plane of
units 42, for
increasing structural rigidity of spacer fixture 40. A bolt 76 (figure 6)
releasably engages oblong
bore 47.
In one embodiment, each pair of successive spacer fixtures 40, 40, on roof
covering 36
support a width of up to six feet of PV panel assembly rail extrusions 60
(figure 6). The distance
between spacer fixtures 40, 40, depends on the combined load and structural
calculations by an
Engineer.
As illustrated in figures 6 and 7, PV panel mounting spacer system 31 also
comprises L-
shaped fixture corner brackets 50 defining first and second legs 52, 54. Leg
54 includes a second
oblong slot 55 releasably engaged by a bolt 72.
As shown in figures 3, a set of L-shaped rail corner brackets 110 are provided
to interlock
corner portions of PV panel assembly rails 100 and 102 with bolt means 72, 76.
Elongated support extrusion rails 60 (see figures 2-3, 6) each defines first
and second
opposite ends 62, 64. Support rail 60 forms extrusion channels 63, 66, 67,
opening at their
opposite ends 62, 64. As shown in figures 6 and 8, a zink-lock nut 70 of
parallelepipedic shape
is lodged inside extrusion channel 65 of rail 100, and is transversely
threadingly engaged by bolt
72, the latter extending through oblong bore 55, so as to releasably interlock
L-shape bracket 50
to rail 100. Rail 100 can be adjustably moved away from or toward exposed
surface 44A of
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bracket seat leg 44 by temporarily unscrewing bolt 72 and allowing the bolt 72
to slide along
oblong bore 55, wherein the spacer gap between planar PV panel assembly 29 and
roof sheet
covering 36 can vary.
A flexible waterproof adhesive membrane 80 is applied underneath the web 42
opposite
leg 44 to be taken in sandwich between roof covering 36 and web 42. Sealing
washer 82 (figure
4) is added to bolt 74, for improved waterproofness.
The first step in assembling PV mounting panel system 31 consists in placing
an
appropriate number of suitably inter-spaced spacer mounting elements 40 on the
sheet metal
sheathing 36 of roof 22 to form an adequate underlying support grid for PV
panel array 29. The
number of required spacer mounting elements 40 is typically determined by a
structural engineer
and depends on the combined downward pressure and the uplift pressure that the
installation may
likely have to sustain during its lifecycle, the strength of the purlins or
furring strips 90 to which
they are anchored (by bolts 74), and the size and thread depth of the lag
bolts 72. The flexible
adhesive sealing membrane 80 is first glued on the underface of web 46 thereby
conformingly
fitting therewith to provide sealing between the web 46 and the roof
corrugated sheet 36. Spacer
mounting element 40 is then placed over roof sheet metal rib 36a on an
appropriate location as
calculated by the structural engineer with the rib-shaped groove web 46
properly aligned with
sheet metal rib member 36a of roof covering sheet 36. Lag bolt seal washer 82
is then placed
beneath the head of lag bolt 74 which is in turn inserted into lag bolt hole
49 of web 46 and
screwed through sheet metal rib member 36a into purlins or furring strips 90.
The complete
waterproof sealing of the installation is insured by the combined effect of
the sealing nature of
sealing membrane 80 flexible material, the sealing nature of sealing washer 82
material, the
thickness of sealing membrane 80 compensating for irregularities on roof
corrugated sheet 36,
the shape of ridge 46 of spacer mounting element 40 matching the shape of rib
member 36a of
roof corrugated sheet 36, and the pressure induced by lag bolt 74 on matching
ridge 46, seal
washer 82 and sealing membrane 80.
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Fixture corner bracket 50 (see figure 6) is then applied onto top surface 44A
of spacer
element 40. Bolt 76 is then successively inserted through bolt hole 56 of
fixture corner bracket
50 and bolt slot 47 of sheet metal fixture 40, with bolt slot 47 allowing for
the proper horizontal
alignment between all corner brackets 50 located on the same rail. Nut 78 is
then screwed on bolt
76, thereby anchoring the fixture corner bracket 50 to sheet metal fixture 40.
Once all spacer mounting elements 40 are secured along with their respective
fixture
corner brackets 50 forming a grid on roof covering 36, a number of lower
support rails 100
matching the number of rows of spacer mounting elements 40 is installed, one
more support rail
60 being linked together if need be by linking plates, and placed in parallel
to roof top and
bottom edges 28, 30. For each fixture corner bracket 50, lock bolt 72 is first
inserted through
lock bolt slot 55 and then partially secured by screwing lock nut 70 on lock
bolt 72, leaving some
room so that lock nut 70 can be later on inserted into one of extrusion
channels 63, 65 of support
rail 100, for example lock nut channel 65. For each support rail 100, each
zinked lock nut 70 for
that rail is successively inserted by aligning the lock nut 70 and fixed into
place by fully
screwing lock bolt 72, securing support rail 100 atop rail support leg 44 and
against the rail
securing member of corresponding fixture corner bracket 50. As the
installation progresses,
manual adjustments can be made as required to compensate for sheet metal
fixtures 40
positioning errors by adjusting the position of fixture corner bracket 50
using bolt 72 in oblong
slot 47 insuring that supports rails 100 are parallel and properly aligned
with the roof top and
bottom edges 28, 30. In a similar fashion, vertical alignment can be made as
required by the
installer using lock bolt oblong slots 59 on fixture corner brackets 50
insuring that support rails
102 are on an even plane parallel to the surface of roof 22 at adjustable
distance.
Once all support rails 100 are in place, a number of upper support rails 102
are installed,
each support rail 102 comprising one or more support rail elements 60 linked
together if need be
by linking plates, and placed in parallel to roof lateral edges 32, 34 in such
a way that both lateral
edges of PV panels 33 can rest on top of a supporting rail 102. Given the
length and weight of
PV panels 33, additional rails can be installed at regular intervals between
the support rails 102
placed on each side of PV panels 33 to provide reinforced support under the
midsection of PV
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panels 33. To proceed with upper support rail installation, rail corner
brackets 110 are first
installed at the junction point of every support rail 100 and support rail 102
on the underlying
support rail 100. For each rail corner bracket 110, lock bolt 72 is first
inserted through a rail
extrusion channel and partially secured by screwing lock nut 70 on lock bolt
72, leaving some
5 room so that lock nut 70 can be later on inserted into lock nut channel 66
of the underlying
support rail 100. For each support rail 102, each lock nut 70 for that rail is
successively inserted
into the extrusion channel underlying support rail 100, and fixed in place
facing either one of
roof lateral edges 32, 34 (but always the same edge) by fully screwing lock
bolt 72, securing rail
corner bracket 110 atop underlying support rail 100.
10 Support rails 102 can now be installed using the rail corner brackets 110
installed on the
lower rail support rails 100. For each rail corner bracket 110, lock bolt 72
is inserted in the rail
extrusion channel and lock nut 70 is then partially screwed on lock bolt 72 so
that lock nut 70
can be inserted into one of support rail 60 lock nut channels 63, 65, for
example lock nut channel
65. For each support rail 102, each lock nut 70 for that column is
successively inserted into a rail
extrusion channel 102 by aligning the lock nut 70 therewith, and fixed into
place by fully
screwing lock bolt 72, securing support rail 102 atop underlying support rail
100 and against the
rail securing member of corresponding rail corner bracket 50. As the
installation progresses,
manual adjustments can be made by adjusting the position of rail corner
bracket 50 ensuring that
supports columns 102 are parallel and properly aligned with the roof lateral
edges 32, 34. In a
similar fashion, vertical alignment can be made as required using lock bolt on
rail corner
brackets 110 ensuring that support rails 102 are on an even plane parallel to
the surface of roof
covering 36.
At this point, PV mounting system 31 is ready to receive the PV panels 33
forming PV
array 29. PV panels 33 are evenly placed along the support rails 102 in a grid
formation (figure
1), with each panel having its lateral edges coinciding with a support rail
102. PV panels 33 are
secured onto the support rails 102 using various kinds of panel securing
clamps: end-column
clamps 102 are placed on the top and bottom edges of the PV panel array 29
preventing
accidental movement of the panels 33 along an axis parallel to the roof
lateral edges 32, 34, end-
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row clamps are placed on lateral edges of PV panel array 29 preventing
movement of PV panels
33 along an axis parallel to the roof top and bottom edges 28, 30 and finally
intersection clamps
are placed at every junction point of four PV panels 33 preventing the
movement of PV panels
33 along an axis perpendicular to the surface of roof covering 36 and to
prevent from moving on
the support rails. All three types of PV panel securing clamps are fixed using
the lock bolt and
nut 72, 70 combinations in slightly different ways: end-row clamps are secured
on the support
rails 102 that are located on each side of PV panel array 29 using the lock
nut channel 66, end-
column clamps are secured on the support rails 102 located on the top bottom
and bottom edges
of PV panel array 29, and intersection clamps are secured over the PV array 29
located on the
top portion of the support rails 102 lying underneath.
One of the advantages of this invention is that the PV panels 33 are spacedly
elevated
from the sheet metal sheathing 36 of roof 22 allowing the wind to flow around
PV panels 33,
thus evacuating the excess generated heat more rapidly. This is important
because PV panel
performance degrades as their temperature increases beyond their optimal
range.
The elevated status of PV panel array 29 also facilitates proper drainage
under rain or
melting snow conditions and at least partially prevents water or snow
accumulations on the
surface of the roof, altogether minimizing the risks of water reaching
otherwise unexposed and
possibly improperly sealed areas of roof 20, thereby reducing the risks of
water leaking inside
the building.
Moreover, elevated panels reduce the risk of damaging the roof sheathing's 36
protective
paint coating by either excess of improper drainage leading to the corrosion
of the sheet metal
which can also lead to water leaking problems and costly repairs.
Finally sheet metal ribs offer lateral support, so mounting spacer elements 40
won't
accidentally move or turn around their lag bolts 74 when PV mounting system 31
is exposed to
extreme external forces, thereby providing a well-sealed and sturdy
installation.
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It is understood that the installation of a solar mounting system on any kind
of roof must
be supervised by a professional Engineer. A professional Engineer must design
an appropriate
anchoring system that allows the mounting system to be securely attached to
the roof. Wind,
snow and dead loads have to be considered in the structural engineer's
analysis. The installer
must verify that all roof anchors are attached to a structural member of the
receiving structure:
this includes purlins, rafters, truss cords, Z-rails or any other such
structural member. The
installer must verify that the roof, its rafters, connections and other
structural members can
support the array under all code-level loading conditions. The installer
should ensure that all
installed fasteners have adequate pullout strengths and shear capacity.
Ensuring the strength of
any fastener used to attach the present invention fixture mounting spacer
element to the roof and
the waterproof integrity of the roof, including the selection of appropriate
flashing and sealing
materials. The installer must ensure the safe installation of all electric
aspects of the PV array.
Parameters such as snow loading, wind loading, dead loads, exposure and
topographic factors
should be confirmed with professional Engineer.
Appropriate thermal management measures are necessary to ensure optimal
performance
of the PV array 29. There is an inverse relationship between operating
temperature and system
performance. Lower pitched roofs 22 typically trap more heat and thus cause
solar arrays 29 to
operate at higher temperature. For better cooling, the air gap between the
roof sheet covering 36
and the PV panels 29 should be increased. Cooling alleys help evacuate heat
and thus reduce
operating temperature. Cooling alleys are edgewise spacings between two
successive coplanar
solar panel assemblies 29, 29, mounted on the supporting pairs of extrusion
rails 60, 60.
Preferably, a horizontal cooling alley should be mounted at least every six
rows of PV panel
assemblies 29. Such cooling alleys provide access for maintenance, heat
evacuation and thermal
expansion capability.
Different parameters have to be evaluated in order to build the right array
with an
optimized racking solution, to ensure maximum modular performance and maintain
structural
integrity.
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Although the present securing spacer element 40 and associated L-shape bracket
50 are
best suited for use with PV panel assemblies over sloping roofs, other
applications are not
excluded from the scope of the present invention, e.g. a work platform or an
advertisement
medium spacedly mounted over a building sloping roof.
