U.S. patent application number 10/494053 was filed with the patent office on 2004-12-16 for low ballast mounting system.
Invention is credited to Diaz, Emilio Mera, Wildman, Eric.
Application Number | 20040250491 10/494053 |
Document ID | / |
Family ID | 8183495 |
Filed Date | 2004-12-16 |
United States Patent
Application |
20040250491 |
Kind Code |
A1 |
Diaz, Emilio Mera ; et
al. |
December 16, 2004 |
Low ballast mounting system
Abstract
An assembly typically comprising solar panel modules is
disclosed, which is mounted on a surface exposed to wind, and has a
panel mounted at an angle to said surface, and means defining a
concave surface extending from the top edge of said panel to the
surface on which it is mounted, whereby impingement of wind on said
concave surface reduces the wind-induced uplift applied to the
assembly. This arrangement reduces the amount of ballast required
to prevent the assembly from blowing away.
Inventors: |
Diaz, Emilio Mera;
(Guadalajara, ES) ; Wildman, Eric; (Madrid,
ES) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
1100 N GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
22201-4714
US
|
Family ID: |
8183495 |
Appl. No.: |
10/494053 |
Filed: |
August 12, 2004 |
PCT Filed: |
October 28, 2002 |
PCT NO: |
PCT/GB02/04861 |
Current U.S.
Class: |
52/518 |
Current CPC
Class: |
H02S 20/24 20141201;
F24S 40/85 20180501; F24S 25/16 20180501; Y02E 10/50 20130101; F24S
25/11 20180501; Y02B 10/10 20130101; Y02E 10/47 20130101 |
Class at
Publication: |
052/518 |
International
Class: |
E04D 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2001 |
EP |
01500258.7 |
Claims
1. Assembly mounted on a surface exposed to wind, having a panel
mounted at an angle to said surface, and means defining a concave
surface extending from the top edge of said panel to the surface on
which it is mounted.
2. Assembly according to claim 1, wherein said concave surface has
an aerofoil-type profile.
3. Assembly according to claim 2, wherein said concave surface has
a NACA profile.
4. Assembly according to claim 3, wherein the location of the point
of maximum curvature of the concave surface is closer to the
leading edge of the surface than to the edge adjacent the
panel.
5. Assembly according to claim 4, wherein the point of maximum
curvature of the concave surface is located between 20% and 40%
along the chord from the leading edge to the edge adjacent the
panel.
6. Assembly according to claim 4, wherein the maximum curvature (or
camber) of the concave surface is between 5% and 15.
7. Assembly according to claim 6, wherein the maximum curvature of
the concave surface is between 8% and 12%.
8. Assembly according to claim 1, wherein the junction of the edge
of the panel and the concave surface is shaped so as to give a
smooth cross-sectional profile across the junction.
9. Assembly according to claim 1, wherein the panel is a solar
panel.
10. Assembly according to claim 9, which comprises an array of
individual modules, each comprising a mounted solar panel, which
modules are linked together so as to form an elongate row of solar
panels joined to a corresponding elongate concave surface.
11. Assembly according to claim 10, which comprises a series of
parallel rows of linked modules, wherein the elongate panel from
one row meets and/or overlaps with the elongate concave surface of
the row immediately in front.
12. Assembly according to claim 10, wherein the concave surface is
in the form of a rigid sheet, containing one or more holes or
perforations so as to allow airflow into the area underneath the
panel and concave sheet.
13. Assembly according to claim 10, wherein the linked modules are
arranged such that the individual concave surfaces of each module
are spaced apart, so as to provide a gap for air to pass
through.
14. Assembly according claim 1, wherein a pair of slots is provided
on either side of the panel and/or concave surface, one underneath
said panel or surface defining a substantially horizontal opening,
and one above it defining a substantially vertical opening, in
association with an internal substantially vertical wall.
15. Assembly according to claim 14, wherein the pair of slots is
provided on either side of the panel.
16. Assembly according to claim 1, which additionally comprises a
base panel such that the panel, concave surface and base panel
together form a triangular assembly.
Description
[0001] This invention relates to a low ballast mounting system, for
use where a flat plate or similar requires to be mounted at an
angle relative to a supporting surface without significant fixings.
The invention has particular applicability to the mounting of solar
panels at an angle to a supporting surface.
[0002] Solar panels, such as for example photo voltaic cells, are
becoming increasingly important as a source of electricity. In
particular, the use of solar panels mounted on the roofs of
buildings for the generation of electricity is becoming
increasingly widespread.
[0003] Many types of solar panel mounting systems are known in the
art. For example, solar panels may be added to an existing roof, or
they may be incorporated into the original design of a new roof.
Where panels are added to an existing roof they are commonly
fastened to the existing surface by the use of fixing devices such
as bolts which penetrate the surface of the roof. Rupture of the
membranes covering a roof by such penetrating fixing devices is
generally undesirable, as it may lead to potential leakage problems
through the roof.
[0004] Alternatively solar panel mounting systems are used which
are not fixed to the roof, but instead simply hold the assembly
down on the surface using ballast. Sufficient ballast is used to
keep the solar modules firmly in place on the roof in the strongest
of winds.
[0005] Generally solar panels are mounted at an angle such that
their surfaces receive the optimum level of solar radiation. Unless
the roof surface on which they are mounted is similarly sloping,
the panels are consequently fixed at an angle relative to the roof
surface. The underside of such a panel, which forms an acute angle
with the surface of the roof, can clearly provide significant
resistance to a wind blowing from the appropriate direction, and in
such circumstances wind-lift and drag can be a major problem. To
overcome this, a mounting system relying solely on ballast requires
large quantities of ballast.
[0006] The requirement for significant ballast can however make
solar panel arrays unsuitable for many roofs, particularly many
flat roofs, which may have insufficient strength to withstand the
weight. There is consequently a need for a more lightweight
mounting system with sufficient resistance to wind-lift.
[0007] In U.S. Pat. No. 5,746,839, for example, it is disclosed
that the use of deflection plates on the rear of angled solar
panels deflects the wind around the panel and reduces the
corresponding wind up-lift. However only flat deflection plates,
which effectively act as a barrier to the wind reaching the rear
underside of the panels, are disclosed.
[0008] We have now found that wind uplift can be reduced more
effectively by the use of a mounting system which utilises a
concave surface to deflect the wind. This is applicable to any
assembly comprising a panel mounted at an angle to a surface where
wind uplift may be a problem.
[0009] Accordingly the present invention provides an assembly
mounted on a surface exposed to wind, having a panel mounted at an
angle to said surface, and means defining a concave surface
extending from the top edge of said panel to the surface on which
it is mounted.
[0010] In the present application, "concave surface" means a
surface having a concave cross-sectional profile over the majority
of its cross-section. It does not exclude surfaces which have a
different profile adjacent the edges: for example, the surface may
have a convex profile adjacent the edge of the panel to which it is
connected, so as to provide a smooth surface across the junction
with the panel.
[0011] Although wind may of course impinge on the assembly from any
direction, the problems of uplift addressed by the present
invention only occur when a component of the wind is blowing into
the acute angle defined by the panel and the surface on which it is
mounted. Accordingly for the sake of clarity the present invention
is described in relation to a nominal wind from such a direction,
i.e. one that impinges directly onto the concave surface. In this
orientation the edge of the concave surface adjacent the surface on
which the assembly is mounted (and remote from the junction with
the mounted panel) may be considered as a leading edge, with the
mounted panel being leeward and forming a trailing edge.
[0012] The mounted panel typically comprises a flat plate or other
similar sheet of material, but may be any construction which, when
mounted at an angle to its supporting surface, would be expected to
have a wind resistance significant enough to cause wind-lift
problems. The concave surface also typically comprises a sheet
rather than a solid body, in order to minimise weight.
[0013] A particular application of the present invention is for
mounting panels such as solar panels at an angle on flat roofs
without the need for penetrative fastenings to secure the system in
place. Equally the invention may be suitable for use in other
applications where a tilted panel or plate would benefit from
aerodynamically mitigated wind uplift, for example, in the case of
portable ramps or jumps.
[0014] The leading edge (when the wind is in the direction of
concern) of the assembly has a concave profile that reduces
wind-induced uplift when impinged by wind. The concave surface
preferably has an aerofoil-type profile, for example, a profile
known in the art as a NACA [National Advisory Committee on
Aeronautics] profile. NACA profiles are well-known in the
aeronautical industry, and are frequently used in any application
which requires an aerodynamic profile. Although a large series of
numbered NACA profiles are publicly available, they can be
simplistically defined for the purposes of the present invention in
terms of the maximum degree of curvature (in %), and its location
along the profile from the leading edge thereof. Preferably the
location of the point of maximum curvature of the concave surface
is closer to the leading edge of the surface than to the edge
adjacent the panel; more preferably, it is located between 20% and
40% along the chord from the leading edge to the edge adjacent the
panel. The maximum curvature (or camber) at this point is
preferably between 5% and 15%, more preferably between 8% and
12%.
[0015] It will be readily apparent that the exact profile of the
concave surface utilised in any particular application will vary
depending on the angle of mounting of the panel, the wind speed(s)
it is required to withstand, and the total size and weight
(including ballast) of the assembly. For example, where there is a
strong requirement for minimum ballast, such as on a relatively
weak roof, then the profile would be designed so as to minimise the
wind-induced uplift. However, where the ballast requirement is not
so stringent and more ballast may be used, then the leading edge
may not need to be shaped for maximum reduction in uplift, and
other factors may influence the profile.
[0016] Preferably the junction at the edge of the panel and the
concave surface is shaped so as to give a smooth cross-sectional
profile across the junction, thereby encouraging laminar flow of
air across the junction and reducing turbulence. This makes the
design more effective at reducing lift. Thus the profile of the
concave surface is modified only close to its edge which abuts the
panel, so as not to disrupt the aerodynamic shape.
[0017] In a preferred embodiment, slots may be provided on either
side of the solar panel and/or concave surface, one underneath it
defining a substantially horizontal opening, and one above defining
a substantially vertical opening in association with an internal
substantially vertical wall. Wind blowing across the roof enters
the void defined by the panel and the concave surface through the
horizontal slot, and is then deflected upwards by the internal wall
so as to exit via the vertical slot, thereby generating a downward
reaction force on whichever of the panel or concave surface is
windward, which further assists in mitigating the wind-induced
uplift. It is most preferred that the slots are provided on either
side of the solar panel rather than the concave surface. This
arrangement has the additional advantage that it permits cooling of
the panel by convection.
[0018] In a further preferred embodiment, the assembly additionally
comprises a base panel such that the front panel, rear concave
surface and base panel together form a triangular assembly. Any
wind which gets into the internal void defined by the two
upstanding panels can exert an upward force on those panels and a
downward force on the surface on which they stand, which would
serve to separate them from that surface if it were the roof If the
surface on which they stand is an integral part of the assembly,
that risk is obviated.
[0019] In the case where the invention is a solar panel assembly,
the assembly typically comprises an array of individual modules,
usually arranged in rows, each comprising a mounted solar panel.
The overall assembly is preferably designed so that individual
modules interconnect together. Typically, the whole array is
secured together by a peripheral cable, which serves to distribute
lateral forces throughout the array, which may contain as many as
100 modules. This has the advantage that the overall array has
greater rigidity and resistance to wind-lift. In such a
configuration the array of adjacent individual modules form what is
effectively a single elongate solar panel attached to a similarly
elongate concave surface. Typically, several of such rows are
employed in parallel on a flat roof In such a case, it is preferred
that the elongate panel from one row meets and/or overlaps with the
elongate concave surface of the row immediately in front. In this
way an extended array is obtained that has a minimum of edges
exposed to potential wind uplift.
[0020] The ends of each row of an array are typically supplied with
end caps or fairings which have concave profiles. This helps to
minimise the effect of wind blowing across the array at an acute
angle.
[0021] The concave surface is typically in the form of a rigid
sheet. In one embodiment it may contain one or more holes or
perforations to allow some airflow into the area underneath the
panel and concave sheet. Similarly, in the case where a series of
modules are connected together to form a row of panels, the
connection may be arranged such that the individual concave
surfaces of each module are spaced apart slightly, so as to provide
a gap for air to pass through.
[0022] Modules may be joined in this way to form an array of
several typically parallel rows of modules. The size and shape of
such an array may be suitably determined to fit within the layout
of the area on which the panels are to be mounted, such as, for
example the shape of a roof Other factors may also be considered
when determining the size and shape of an array, such as, for
example, allowing for suitable access to the modules in the array,
for example, for maintenance purposes.
[0023] When several modules are connected together in a row, the
assembly may include channels under the rows of modules. Such
channels may be used to house e.g. electrical components, where
they can be sheltered from the elements. For example, where the
mounting system is used for a solar panel array, inverters and
other electrical components may be housed under the array. Row end
fairings may be used to cover electrical roof penetrations or major
electrical junction boxes.
[0024] The means for fastening individual modules of the assembly
together in a row may comprise any suitable means as known to one
skilled in the art. Examples of fixings that can be used include
screws with expansion rawlplugs, standard screws and nuts, or metal
inserts in plastic. Any fastening plates used may be of any
suitable material such as plastics or metal.
[0025] It is preferred that any fixers and/or fastener plates used
to lock the adjacent mounting modules together are aerodynamically
shaped in such a way as to generate a smoother surface to the
entire array, reducing the numbers of edges exposed to wind-lift.
In particular it is preferred that the fasteners used to secure the
edges of each row are also aerodynamically shaped. In this way
smooth flow of wind over the entire assembly may be achieved,
reducing turbulence and improving the effectiveness of the design
in reducing lift.
[0026] In the case where the assembly comprises a row of adjacent
or interconnected solar panel modules, and several rows are sited
in parallel to form an array, the concave surface and any fasteners
of each row may be formed of or coated with a reflective material
so as to reflect solar radiation onto the solar panels of the row
behind.
[0027] A preferred embodiment of the invention is described further
with reference to the accompanying drawings, in which:
[0028] FIG. 1 shows a pair of adjacent modules each comprising a
panel and associated concave surface; and
[0029] FIG. 2 shows an array of parallel rows of the modules of
FIG. 1;
[0030] FIG. 3 shows the same view as FIG. 2 but from the other
side;
[0031] FIG. 4 shows a concave surface having an NACA profile;
[0032] FIG. 5 shows a concave surface having a symmetric NACA
profile.
[0033] In FIG. 1, a pair of connected modules is shown each
comprising a panel 1 attached to a respective concave surface 2. In
this particular embodiment, the concave surface has a convex
portion 3 at its edge adjoining the panel 1 in order to provide a
smooth surface across the junction between the two parts. This is
to ensure a laminar flow of air across the junction. This
embodiment also has connector plates 4 for connecting adjacent
modules together.
[0034] If an array of modules is to be created comprising parallel
rows, the panels at the front of the array have further
aerodynamically shaped attachments 5 to permit smooth airflow
across them from that direction. FIGS. 2 and 3 show part of such an
array, comprising three rows 6, 7, 8 of three modules each. To
demonstrate the internal construction, one panel of the array is
not shown, and another panel 9 is shown rotated forward. In these
Figures the connector plates 4 are again visible. It can be seen
how the construction is such that the panels of one row overlap
with the concave surfaces of the adjacent row.
[0035] Examples of the profile of the concave surfaces are shown in
FIGS. 4 and 5. These show modified NACA profiles having a maximum
camber of 10%, but located at different points along the profile of
the surface. It has been found that locating the point of maximum
camber closer to the leading edge than the edge adjacent the panel
is desirable. In both these theoretical profiles there is no
smoothing of the profile at its edge adjacent the edge of the panel
(i.e. remote from the leading edge). In practice, this would create
a sharp edge at the top of the assembly, leading to turbulent flow
and increased uplift. This can be counteracted by smoothing this
end of the profile to create a convex portion, which leads smoothly
into the adjacent upper surface of the panel.
* * * * *