Note: Descriptions are shown in the official language in which they were submitted.
CA 02824032 2013-08-16
SOLAR PANEL RACK SYSTEM
Field of Invention
The present invention relates to mounting and installation apparatus for use
with solar
photovoltaic an-ays and to a solar panel mounting system that incorporates
such
apparatus.
Backuound
Since 2002, electrical power derived from photovoltaic cells has increased
from less than
1 GWp/year to more than 100G\Vp/year as of the end of 2012. Moreover,
photovoltaic
(PV) systems are now used to generate power in over 100 countries around the
world.
Continual research and development into improving the efficiency of PV systems
has
resulted in these devices becoming more economically viable as means for the
production
of electrical power from sunlight. For example, for crystalline silicon solar
cell devices
the cost of production of power was fallen from $77/Watt in 1977 to about
$0.74/Watt in
2013. The cost of producing power from PV system is now less than that
produced from
nuclear sources and continues to fall.
Despite this rapid growth, PV electrical production still accounts for only
about 0.5% of
global electrical production capacity, and so remains an area where
significant growth is
yet to be realized. Part of the inherent cost of any PV system is that of
installation.
Photovoltaic systems are generally provided as arrays of individual panels
that are then
CA 02824032 2013-08-16
linked together to produce the desired output. For example, a typical panel
may produce
on the order of 200-250W of power under full illumination. To create a system
capable
of practical output, a number of panels will be connected together as an
array. For
example, an array of 32 panels each capable of 225W can theoretically produce
'7.2kW,
which would generate enough power over the course of a year to offset the
electrical
energy needs of a typical household.
A drawback with this kind of arrangement is that it takes a significant amount
of effort
and time in order to build a mounting rack, install the individual panels onto
the rack, and
then make the electrical connections between each panel in the array and
various other
components such as inverters, ballasts and metering systems. As a result, for
larger
installations, there has been a trend towards manufacturers supplying pre-
fabricated
arrays on rack systems. These pre-assembled arrays can then be delivered to an
installation site and more easily installed.
For example, seine companies now offer pre-fabricated racking systems that can
be
quickly installed on a building, typically on a rooftop. For example, U.S.
Patent
Application Publication No. 2012/0036799 discloses a modular rack system
designed to
support a PV module, and which can be pre-fabricated into a rack array ready
to receive
PV panels. Using these system the rack is typically installed on a building
roof, and then
individual panels are installed and electrical connections made. This approach
suffers
from the problem that installation is still relatively labour intensive since
a significant
amount of assembly is required at the job site. Thus, what is needed in the
industry is a
PV array system that is substantially completely pre-fabricated, with the
rack. PV
modules, and electrical components assembled in a factory setting. However,
while in
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principle this might seem straightforward, in fact larger pre-fabricated
arrays create other
challenges.
For example, as the array and rack assembly become larger, there is a tendency
of the
rack to flex as it is moved or transported. Since PV panels comprise
crystalline materials,
flexing is a problem with PV panels fixed to racks, as the panels themselves
are prone to
damage if they are subjected to torsional stresses. Significantly, damage
caused during
assembly and transport may void the manufacturer's warranty coverage of the PV
panel.
One way in which to reduce flexing is to increase the rigidity of the members
that
comprise the rack portion of the system. However, increase the rigidity of
rack members
would normally be accomplished by increasing the size of the member. This
would lead
to significant increases in weight, which in turn leads to increased cost of
production,
transportation and difficulties in handling during installation.
As a result, there is a need in the industry for an improved design of PV
module racking
systems that allows for the manufacture of essentially "plug and play" PV
arrays, and
which protects the pre-fabricated array from damage to the PV modules during
assembly,
transport and installation.
List of Figures
While the invention is claimed in the concluding portions hereof, preferred
embodiments
are provided in the accompanying detailed description which may be best
understood in
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conjunction with the accompanying diagrams where like parts in each of the
several
diagrams are labeled with like numerals, and where:
Fig. 1 is a perspective view of an example of a PV module array installed on
a.
rack support system according to one embodiment of the present invention.
Fig. 2 is a perspective view of an example of a PV module array where the PV
panels are attached to the rack hinges. The modules are in an upright,
uninstalled
configuration to show the panels before they are attached at the top edge.
Fig. 3 is a perspective view of the underside of an example of a PV module
array
showing support pads designed to support the weight of the array when
installed
on a structure such as a rooftop.
Fig. 4 is a perspective view of an example of a PV module array depicting PV
panels installed on a rack.
Fig. 5 is a side view of an. example of a PV module array showing the detail
of the
top edge mount in the transport configuration.
Fig. 6 is a perspective view of an example of a PV module array showing a
hinge
assembly in the transport configuration.
Fig. 7 is a perspective view of an example of a PV module array depicting PV
panels in the installed configuration and examples of electrical accessories
that
can be mounted on the rack underneath a PV panel.
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Fig. 8 is a view of an example of a PV module array showing electrical conduit
and wiring situated within the rack.
Fig. 9 is a view of an example of a PV module array showing a loading support
that bears the load of the rack assembly during transport.
Fig. 10 is a view of an example of PV module arrays fully assembled and loaded
on a transport, ready for delivery to a job-site.
Description of Invention
The following discussion provides examples of embodiments of the inventive
subject
matter. Although each embodiment represents a single combination of inventive
elements, the inventive subject matter is considered to include all possible
combinations
of the disclosed elements. Thus if one embodiment comprises elements A. B. and
C. and
a second embodiment comprises elements B and D, then the inventive subject
matter is
also considered to include other remaining combinations of A, B, C, or D, even
if not
explicitly disclosed. Those of skill in the art will recognize that the
described
embodiment are examples of possible configurations of the invention, and are
not
intended to be limiting, to the scope of the invention. Accordingly, the
drawings and
descriptions contained herein are to be regarded as illustrative of the
invention as set forth
in the accompanying claims.
These and all other extrinsic materials discussed herein are incorporated by
reference in
their entirety. Where a definition or use of a term in an incorporated
reference is
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inconsistent or contrary to the definition of that term provided herein, the
definition of
that term provided herein applies and the definition of that term in the
reference does not
apply. Similarly, in some cases alternative terms refer to the same item. For
example PV
module and PV panel are generally understood to mean the same thing. A PV
array will
refer to a plurality of PV modules connected together, generally, although not
necessarily
in a single rack.
Unless the context dictates the contrary, all ranges set forth herein should
be interpreted
as being inclusive of their endpoints, and open-ended ranges should be
interpreted to
include commercially, practical values. Similarly, all lists of values should
be considered
as inclusive of intermediate values unless the context indicates the contrary.
In cases
where dimensions or other measurements are provided in illustrations or the
accompanying description, it is not intended that any such information is to
be interpreted
as limiting the scope of the invention.
As shown in Fig. 1, an example of the present inventive technology shows a
series of PV
modules installed in a rack system. Racks are generally intended to be mounted
on
rooftops in order to make use of otherwise \\Fasted space. The rack system as
described
herein is also compatible with other types of mounting arrangements, such as
post
mounts, ground mounts, and mounts that are designed to steer the PV array such
that it
continually faces the sun during the course of the day.
Racks can also be fashioned to improve the efficiency of a solar array system.
As can be
seen, in some cases the rack can be inclined at a gradient. The gradient
provided by the
rack can be selected based on the slope of the location where the array is to
be installed,
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taking into consideration the average elevation of the sun above the horizon
over the
course of the year. For example, at higher latitudes for an installation on a
flat roof, a
steeper rack gradient would be desirable so that the PV array more directly
faces the sun.
The inverse would be true where the array is to be installed on a sloped roof
and/or at
lower latitudes. Those of skill in the art will be readily able to determine
an optimal rack
gradient as described as an angle theta formed with reference to the top and
bottom edges
of the rack assembly.
Fig. 2 provides an example of a PV array and rack assembly vdiere the PV
panels are
secured to a bottom edge of a rack, but are not yet attached to the top edge
of the rack.
Conveniently, the PV module can be secured to the bottom edge (or hinge edge)
of the
rack with hinge assemblies. Each PV module can be secured to the rack by at
least one
hinge, and preferable two hinges, one generally at each side of the PV module.
'There is
no specific number of hinges that are required, and it may be desirable where
larger
length PV panels are used to provide hinges near each end as well as hinges in
the middle
of the panel to better support the panel over its entire length.
Fig. 3 shows an example of a PV panel and rack assembly from underneath. In
some
case it may be advantageous to provide support pads secured to the underside
of the rack.
These pads can be fashioned from any resilient material, for example, and
without being
limiting, polystyrene foam. The pads are designed to support the weight of the
area on
the structure \\here the array has been installed, for example on a rooftop.
The support
pads further provide the advantage of spreading out the weight of the area so
that the risk
of overloading the roof structure at the points of contact between the array
and the roof is
essentially obviated. In some cases support pads can be provide at each comer
of the
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anay and at locations between the corners. The spacing and number of pads will
depend
on the weight of the array and the particular structural characteristics. Pads
may also be
configured to be affixed onto mounting points, for example bolts, or other
structures, and
be able to be secured with fasteners to such structures. Such methods of
securing solar
arrays to buildings are well known in the art.
Fig. 4 depicts an exaniple of a PV array and rack system of the present
invention,
showing the PV panels in the installed configuration. As shown, the module can
be
secure to the rack by a top edge mount, vskiose structure and function will be
described in
greater detail below. As can also be seen the rack is designed to provide an
enclosed
space. The enclosure is able to keep rodents and other larger pests out from
underneath
the array. It also provides an enclosed area where other components can be
placed and
protected both from the elements and pests. For example, the bulk of the
electrical
wiring within the array that connects PV modules to each other can be placed
within the
enclosed space within the rack. Similarly, other electrical components such as
inverters,
ballast and wiring are able to fit within this enclosure. Conveniently, the
rack sides can
include venting slots to provide airflow through the rack and under the PV
panels in order
to allow for heat to be dissipated by convection. In some applications, small
electrical
fan assemblies might also be placed under the PV panels within the enclosed
rack space
in order to actively move cooling air to dissipate heat generated while the
system is in
operation. Power for the fans could be derived from the output of the array
itself.
Fig. 5 depicts an example of a top edge mount of the present invention in
greater detail.
As shown, the mount assembly comprises a nut and bolt arrangement that secures
the PV
panel to the rack assembly. In the transport configuration the nut and bolt
are not
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tightened as is typical in prior art assemblies, but rather a space is left s
that the PV panel
is able to "float" above the top edge of the rack, and separation is provided
between the
panel and its rack.
In the transport configuration there is also provided a shock absorber spacer.
The spacer
is designed to support the PV panel and maintain separation between the panel
and the
rack. In some cases the shock absorber can be formed from a resilient material
such as a
foain that allows some up and dowi movement of the PV panel along the length
of the
bolt while generally preventing the PV panel from corning into direct contact
with the
rack. A major advantage provided is that in the course of transportation of
the solar array
the PV modules are isolated from vibration and flexing of the rack as it is
being moved.
This isolation system protects the PV panels from potential damage due to
torsional
strains and/or vibration as as might otherwise occur if the panels were
securely attached
to the rack. Vibration and torsion are common occurrences during handling of
solar array
assemblies, and the damage they cause is generally not covered by manufacturer
warranties provided by solar panel makers.
In some cases, and as shown in Fig. 5, the shock absorber may be placed
between a rack
flange and the PV module in order to keep them separate during transport.
Conveniently,
the shock absorber can be designed so that it is easily removable prior to
final installation
of the solar array. For example, the shock absorber may be attached to the
rack flange
with an temporary adhesive, for example the glue used on items like paper Post-
It
notes. The adhesive will be sufficiently secure tc) maintain the shock
absorber in place
during manufacture and transport of the array, but can be easily removed by
hand when
the array is in position and ready for the final steps in the installation
process. In some
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cases it may be desirable to provide a shock absorber that slides onto the
shaft of the bolt
and supPorts the PV module, keeping it separate from the rack. In this case,
the shock
absorber might have a slit cut into one side to allow for easily placement
onto the bolt
shaft, with or without the need to a temporary adhesive.
As shown in Fig. 6, on the opposite edge of the PV panel there are provide
hinges that
secure the bottom edge of the pane to the bottom edge of the rack. As with the
design of
the top edge mount, the hinges are also designed with a nut and bolt
arrangement that
leaves a space between the PV module and the rack when in the transportation
configuration. As with the top edge mount, a shock absorber can be placed
within the
space provided to maintain the separation between the PV module and rack, and
to isolate
the PV module from vibration and flexing during handling of a solar array.
Amin, like
the top edge mount, once the rack is in place, the shock absorber can be
removed and the
nut and bolt assembly tightened to secure the PV module to the rack.
Alternatively, in some cases, it may be desirable to leave the shock absorber
in place
during installation and simply tighten the nut and bolt assemblies thereby
compressing
the shock absorber in place between the PV module and the rack assembly.
Leaving the
shock absorber in place could provide an advantage where the solar array is
installed in a
high vibration location in order to maintain some isolation between the rack
and the PV
modules. Similarly, leaving a spacer in place could provide additional
electrical isolation
between the panels and the rack on which they are mounted should that be
desirable.
Regardless of the type and placement of the shock absorber, as part of the
final
installation procedure, the shock absorber can be removed (or not as the case
may be),
CA 02824032 2013-08-16
and the nut and bolt tightened in order to firmly secure the PV module to the
rack. This
step will typically be done once the array has been lifted into place and the
rack secured
to the rooftop or whatever structures it may be mounted on. Accordingly,
during the
lifting of the array into place, another point at which significant flexing of
the rack can be
experience, the PV modules are isolated from the vibration and flexion and are
thus
substantially protected from inadvertent damage during the installation
process. Only
once the array is safely in place will it be necessary to finally tighten the
mounts. Until
that time the panels will be isolated from the rack and thus protected from
damage due to
vibration and/or flexion.
Engineering studies conducted by the inventors using typical rack systems have
shown
that rack flexion of up to 2.5 mm are not uncommon during handling of a rack
and solar
array system. The spacing between the PV module and the rack provided by the
bolt
assembly and shock absorber can be easily designed to provide at least this
much
movement of the rack without significant flexion of the PV modules.
Fig. 7 depicts an example of the present invention showing how other
electrical
components can be conveniently placed within the enclosure formed by the,
rack, taking
advantage of otherwise wasted space. Placing components such as inverters and
ballast
provides the advantage of protecting these devices from the elements or common
pests
such as rodents. Placing these components within the rack space also precludes
the need
to mount these devices elsewhere. Further, as part of the overall advantage of
providing
a completely ready to "plug and play" solar array system, these components can
be pre-
connected to the PV modules within the array, again saving significant time
during the
installation of the array. Typically current systems require each of these
electrical
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components to be installed once the array is in place, increasing the workload
and time
(as well as expense) required to put the array into commission.
Similarly, Fig. 8 depicts a rack assembly where the wiring is situated within
conduit
forming part of the rack stmcture. The conduit may be partially open or
completely
enclosed as desired. Enclosing the wiring protects it against damage due to
the elements
or pests. Conveniently, the pre-fabricated system can be produced such that
all the
wiring connections between individual PV modules, and other accessory
components is
completed at the factory. Unlike prior art systems where panels nmst be
shipped
separately from rack components to prevent damage during transport, the
present system
allows for an array to be essentially completely pre-fabricated such that an
entire array is
effectively operational with a single connection. This greatly simplifies the
time and
effort required to install and made such a system operational.
As shown in Fig. 9, .there can also be provided loading supports. These
supports are
desiped to allow for rack and panel assemblies to be stackable for transport.
These
loading supports provide sufficient spacing so that individual arrays of PV
modules on
racks can be stacked without the top of one assembly coming into contact with
the
bottom of an assembly stacked on top. In some cases, and as shown in Fig. 9,
the loading
support can include a resilient pad that provides vibration isolation between
the transport
vehicle and the rack assemblies, further protecting PV modules from the
possibility of
damage. The loading support can be designed to be removable, such that after
off-
loading of the assembly from the transport vehicle and prior to placement at
the
installation position, the support is removed from the assembly. As shown in
Fig. 9, a
simple pin and cotter pin arrangement permits the loading support to be easily
removable
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from the rack assembly, while permitting the support to maintained securely in
place until
such time as it is to be removed.
The positioning and number of loading supports will vary depending on the size
and
weight of the rack and PV module array. At a minimum it will be preferable to
have a
loading support positioned at each comer of an an-ay assembly. For larger
arrays it may
be preferable to include additional support in order to better support the
weight of the
array while it is transported. As can be appreciated from the diagram the
loading
supports are designed to be stackable so that the entire load is supported
generally
vertically through the loading support member. As a result, there is no
loading- on an
individual rack assembly other than the load each assembly exerts on the
loading support
to which it is connected. This type of arrangement provides the ability to
stack a number
of an-ays without concern for overloading the rack assemblies towards the
bottom of the
stack. Put another way, the supports carry the load, not the racks.
Fig. 10 thus depicts an example of finished pre-fabricated arrays loaded on a
truck for
transport to an installation site. The stackable arrangement of the loading
supports can be
appreciated from the figure.
It will be recognized that the specific materials used in constructing the
various
components of the system described herein, are not considered to be limiting
to the scope
of the invention. Those of skill in the art will readily recognize and be able
to select
materials and components that will accomplish the objectives of the invention
without
requiring any inventive skill.
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It should also be apparent to those skilled in the art that many more
modifications besides
those already described are possible without departing from the inventive
concepts
herein. The inventive subject matter, therefore, is not to be restricted
except in the scope
of the appended claims. Moreover, in interpreting bath the specification and
the claims,
all terms should be interpreted in the broadest possible manner consistent
with the
context. In particular, the terms "comprises" and "comprising" should be
interpreted as
referring to elements, components, or steps in a non-exclusive manner,
indicating that the
referenced elements, components, or steps may be present, or utilized, or
combined with
other elements, components, or steps that are not expressly referenced.
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