U.S. patent application number 12/795949 was filed with the patent office on 2010-12-16 for supporting structure for an open-space photovoltaic system.
This patent application is currently assigned to Adensis GmbH. Invention is credited to BERNHARD BECK.
Application Number | 20100313500 12/795949 |
Document ID | / |
Family ID | 42732880 |
Filed Date | 2010-12-16 |
United States Patent
Application |
20100313500 |
Kind Code |
A1 |
BECK; BERNHARD |
December 16, 2010 |
SUPPORTING STRUCTURE FOR AN OPEN-SPACE PHOTOVOLTAIC SYSTEM
Abstract
A supporting structure for an open-space photovoltaic system
with several ground supports arranged in at least two mutually
parallel rows oriented in essentially North-South direction and
installed vertically in the ground, with beams supported on free
ends of the ground supports located at the same location along a
row, and with module rails attached to the beams for attachment of
fastening means for photovoltaic modules. The module rails are
secured on or between two corresponding adjacent beams in
essentially North-South direction. The free ends of the ground
supports are positioned at the same height above terrain ground, so
that the beams and the module rails extend essentially
plane-parallel to the terrain ground. This arrangement reduces
material consumption, and only a small surface area of the
supporting structure is effectively exposed to wind gusts. Each row
of ground supports includes ground supports with both rigid and
flexible flexural characteristics.
Inventors: |
BECK; BERNHARD; (Volkach,
DE) |
Correspondence
Address: |
HENRY M FEIEREISEN, LLC;HENRY M FEIEREISEN
708 THIRD AVENUE, SUITE 1501
NEW YORK
NY
10017
US
|
Assignee: |
Adensis GmbH
Dresden
DE
|
Family ID: |
42732880 |
Appl. No.: |
12/795949 |
Filed: |
June 8, 2010 |
Current U.S.
Class: |
52/173.3 ;
52/653.1; 52/745.21 |
Current CPC
Class: |
F24S 25/12 20180501;
Y02E 10/47 20130101; Y02E 10/50 20130101; F24S 25/50 20180501; H02S
20/10 20141201 |
Class at
Publication: |
52/173.3 ;
52/745.21; 52/653.1 |
International
Class: |
E04H 12/02 20060101
E04H012/02; E04B 1/38 20060101 E04B001/38 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 12, 2009 |
DE |
10 2009 024 738.6 |
Claims
1. A supporting structure for an open-space photovoltaic system,
comprising: a plurality of at least four vertical ground supports
arranged in parallel aligned rows and having defined positions
along a row, each vertical ground support having two ends, with a
first end installed in the ground, a plurality of beams supported
on a second end and positioned at an identical height above terrain
ground, with each beam installed on or between ground supports
located at identical row positions along the rows, and at least one
module rail secured on or between adjacent beams and configured for
attachment of fastening means adapted to receive photovoltaic
modules, wherein the plurality of beams and the at least one module
rail extend essentially plane-parallel to the terrain ground,
wherein each row of ground supports comprises ground supports with
a comparatively rigid flexural characteristic located at identical
positions in the rows, and wherein at least two comparatively
flexible intermediate ground supports are located between two
consecutive arranged ground supports having the rigid flexural
characteristic.
2. The supporting structure of claim 1, wherein the photovoltaic
modules are mounted on the module rails with an angle of
inclination between about 2.degree. and about 20.degree..
3. The supporting structure of claim 1, wherein at least one of a
ground support, a beam, a module rail or a fastening means is made
of an electrically insulating material.
4. The supporting structure of claim 1, wherein the different
flexural characteristics are based on cross sections of the ground
supports.
5. The supporting structure of claim 4, wherein the ground supports
comprise round pipes having different diameters, wherein the rigid
ground supports have a larger diameter than the flexible ground
supports.
6. The supporting structure of claim 4, wherein the ground support
is an IPE or a wide-flanged-I-beam, which can be installed
longitudinally or transversely, depending on a desired bending
direction.
7. The supporting structure of claim 6, characterized in that a
rigid bending direction of the intermediate ground supports is
oriented in an E-W direction, while the rigid bending direction of
all other ground supports, excluding the intermediate ground
supports, is in an N-S direction.
8. The supporting structure of claim 1, wherein the modular rails
are bands or cables having ready-made lengths with ends, the
modular rails comprising a spring disposed on at least one of their
ends.
9. The supporting structure of claim 8, wherein several module
rails are joined with one another via the spring.
10. The supporting structure of claim 9, wherein several module
rails are joined with one another via an isolator.
11. The supporting structure of claim 1, wherein the ground
supports are arranged in a grid pattern and the module rails
include openings configured for attachment to the beams.
12. The supporting structure of claim 8, wherein the module rail
comprises a flat metal band and the spring is implemented as a
corrugated section disposed on at least one of the ends of the flat
metal band.
13. The supporting structure of claim 1, wherein the plurality of
ground supports is aligned in rows oriented substantially in the
North-South direction, wherein the plurality of beams is aligned
substantially in the East-West direction, and wherein the at least
one module rail is aligned substantially in the North-South
direction.
14. The supporting structure according of claim 1, wherein the
plurality of beams is located at a height of 0.5 m to 1.5 m above
the terrain ground.
15. The supporting structure of claim 1, comprising at least four
module rails arranged in mutually parallel relationship.
16. A method for installing a supporting structure having the
structure of claim 1, comprising the steps of: securing the at
least four vertical ground supports in the ground to form several
parallel adjacent rows, with the free ends of the ground supports
being located approximately at an identical height above terrain
ground, connecting the plurality of beams to the free ends of those
ground supports that are located next to one another at identical
row positions along the rows, tensioning the at least one module
rail by affixing one end of the module rail and applying a
tensioning force to another end of the module rail, and attaching
the at least one module rail to the plurality of beams under
tension.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the priority of German Patent
Application, Serial No. 10 2009 024 738.6, filed Jun. 12, 2009,
pursuant to 35 U.S.C. 119(a)-(d), the content of which is
incorporated herein by reference in its entirety as if fully set
forth herein.
BACKGROUND OF THE INVENTION
[0002] The invention relates to a supporting structure for an
open-space photovoltaic system with several ground supports with
one end rising from the ground, with beams being supported on the
other end, and with module rails mounted on the beams for
attachment of fastening means, in particular clamps, for
photovoltaic modules.
[0003] The following discussion of related art is provided to
assist the reader in understanding the advantages of the invention,
and is not to be construed as an admission that this related art is
prior art to this invention.
[0004] Supporting structures of this type are widely used. They
have mostly a superstructure where ground supports of different
lengths rise vertically from the ground or are embedded vertically
in a foundation connected with the ground. The ground supports are
arranged in two rows, with the row with short ground supports and
the row with the longer ground supports both extending in East-West
direction. Beams or joists are placed on top of the free ends of
the ground supports, which also oriented in East-West direction,
and attached. This produces two continuous beams having a length
of, for example, hundred meters, which are each supported by a
plurality of ground supports. One of the continuous beams is at a
lower level than the other, with a typical height difference
ranging from, for example, 60 cm to 80 cm. The height difference
defines the slope of the module rails, which extend perpendicular
to the supports and are mounted thereon in North-South direction,
with respect to the ground plane. The photovoltaic modules all then
attached on the module rails with clamps.
[0005] This arrangement provides an advantageous angle of incidence
for the photovoltaic modules, but is relatively complex and
relatively massive, in order to be able to withstand wind forces
which attack below the mounted inclined PV modules. Moreover,
automated installation of the PV modules is difficult due to the
large inclination. In addition, in an arrangement with several
rows, space must be left between the rows to prevent shadowing of
the lower region of the adjacent northern row of PV modules by the
upper photovoltaic modules of the adjacent southern row of
photovoltaic modules. Finally, ground supports and beams cannot be
used for dual purposes where a row of beams supports module rails
for two rows of photovoltaic modules, as this is not possible due
to the aforementioned required spaces between the rows and the
different levels.
[0006] It would therefore be desirable and advantageous to obviate
the aforementioned disadvantages associated with the massive
structure and the space requirement, to provide an improved
supporting structure for a photovoltaic system which facilitates
automatic installation of the photovoltaic modules and reduces
oscillations caused by the wind load by transferring the associated
wind forces into the ground.
SUMMARY OF THE INVENTION
[0007] The present invention resolves prior art problems by
arranging at least two mutually parallel rows having each at least
four ground supports in substantially North-South direction,
installing a corresponding beam in substantially East-West
direction on or between ground supports located at the same
position along a row, mounting at least one module rail on or
between two corresponding adjacent beams in substantially
North-South direction, wherein the other ends of the ground
supports are located at the same height above the ground, so that
the beams and the module rails extend substantially plane-parallel
to the ground, wherein each parallel aligned row of ground supports
disposed at the same position in the row has ground supports with a
comparably rigid flexural characteristic, and wherein at least two
comparatively flexible intermediate ground supports are located
between each of two consecutive ground supports with rigid flexural
characteristic.
[0008] This arrangement allows installation of the photovoltaic
modules without requiring a large area; however, because the
photovoltaic modules extend parallel to the ground, the light
efficiency is reduced.
[0009] The reduced light efficiency can be compensated in part by
installing the photovoltaic modules on the module rails with an
angle of inclination between 2.degree. and 20.degree..
Advantageously, the angle of inclination may be provided by the
type of the fastening means. For example, clamps may be employed
which support the lower edge of a photovoltaic module on a support
surface which is located at a lower level than the upper edge of
the preceding photovoltaic module which rests on the clamp on a
support surface at a higher level. Such clamps are commercially
available for use with system installed on flat roofs.
[0010] A large facility dimensioned according to the invention with
a rectangular design may have edge lengths of several hundreds of
meters, which may introduce substantial forces under windy
conditions or may even cause oscillations. The substantial forces
are counteracted according to the invention in that each parallel
aligned row of ground supports at the same position in the row has
a comparable rigid flexural characteristic, and two comparatively
flexible intermediate ground supports are located between two
corresponding consecutive ground supports with the rigid flexural
characteristic. A portion of the forces is then advantageously
transferred through flexing of the intermediate ground supports
into the ground as a bending moment, while only fixed points are
defined to prevent excessive flexing. A buildup of oscillations can
be counteracted with springs, as described below in more
detail.
[0011] The supporting structure described above represents the
smallest unit exhibiting the advantages of the invention. In
practical application with large photovoltaic systems extending
over several hundred meters and having areas of up to 1 km.sup.2
equipped with PV modules, the smallest unit can be easily expanded
or multiplied. The smallest feasible lower dimension to justify the
costs for construction vehicles, installation automat, personnel,
etc., appears to include at least four mutually parallel rows
having each at least four ground supports and accordingly four
beams. The term "beam" in the context of the present invention
refers to any support member capable of supporting module rails. It
is also not required that a corresponding dedicated, separate beam
is mounted on or between two grounds supports. The beam may be
dimensioned to extend across several ground supports. Accordingly,
only a portion of the beam is then located between two grounds
supports.
[0012] As mentioned above, large areas of contiguous metal may be
accumulated in an area, which would represent an attractive target
for lightning strikes during a thunderstorm. Accordingly, the
entire metal mass is advantageously subdivided into a large number
of small, mutually insulated metal masses, which then no longer
form a large "striking electrode" for a lightning bolt. This is
accomplished by fabricating at least one of the parts: ground
support, beam, module rail, or fastening means from an electrically
insulating material. Alternative or additional measures provide:
[0013] that the ground supports and the beams are made of metal and
that an insulating material separates the beams from the ground
supports, and/or [0014] that the beams and the module rails are
made out of metal, and that an insulating material separates the
module rails from the beams, and/or [0015] that the fastening means
is made of an electrically insulating material.
[0016] The aforementioned different flexural characteristics can be
due to the cross sections of the ground supports. For example, the
ground supports may be round pipes having different diameters,
wherein the rigid ground supports have a greater diameter than the
flexible ground supports. IPE or a wide-flanged-I-beams can also be
used as ground supports, which can be installed in the longitudinal
or transverse direction depending on the desired flexing direction.
The terms "rigid" and "flexible" are meant to indicate relative
properties and do not represent a limitation with respect to the
physical value of the flexural characteristic.
[0017] Advantageously, the rigid flexing direction for the
intermediate ground supports extends in the East-West direction and
for all other ground supports in the North-South direction. This is
related to the later installation of the module rails which are
tensioned. The rigid flexing direction of the intermediate ground
supports in the East-West direction prevents excursions at great
lengths which could cause the PV modules made of glass to push
against each other. However, the ground supports may also be
installed with the directions reversed or even in arbitrary
directions.
[0018] To simplify their fabrication, the module rails are provided
as bands or cables with a ready-made length and have on at least
one end a spring element--preferably in conjunction with an
isolator. Several of these ready-made module rails are then
connected with one another via the spring and optionally the
isolator. This preparation of the module rails reduces the
complexity of installation on-site, which is more expensive than at
the place of manufacture.
[0019] To simplify installation, the ground supports may be
arranged in a grid pattern, wherein the module rails in this grid
pattern are provided with preparation means for preparing their
attachment to the beams. The preparation means is in its simplest
form an opening or a hole extending through the module rail,
through which a screw can later be screwed into the beam for
affixing the module rail on the beam.
[0020] The module rails are typically made of aluminum profile.
Alternatively, to shorten the installation time, the module rail
may advantageously be a flat steel band, wherein the spring is
realized by corrugating the flat steel band at an end.
[0021] A height of the beams or joists of 0.5 m to 1.5 m above
terrain ground, i.e., above ground level, has proven to be
sufficient in the context of the stated object to achieve a low
installation height of the supporting structure.
[0022] According to a possible method of the invention for
installing the supporting structure, the ground supports are first
fixedly installed in the ground so that their free ends are all
approximately at the same height and several parallel adjacent rows
are formed, whereafter the beams are connected with the free ends
of the ground supports which are located next to one another at the
same position of the rows. In an additional step, the module rails
are attached on one end and tensioned by applying a tension force
at the other end, whereafter they are attached on the beams in the
tensioned state. This approach requires that the module rails are
made of at least a flexible material, for example the
aforementioned flat steel, or even made of a flexible material,
such as nylon or Teflon band, which then has an integrated spring
action. The band which is attached with one end to the beam on the
rigid ground support is tensioned with a cable winch until all
openings are located at the height of additional beams. The band is
then affixed in this position to the beams through the holes.
BRIEF DESCRIPTION OF THE DRAWING
[0023] Other features and advantages of the present invention will
be more readily apparent upon reading the following description of
currently preferred exemplified embodiments of the invention with
reference to the accompanying drawing, in which:
[0024] FIG. 1 is a top view onto a supporting structure for a
photovoltaic system,
[0025] FIG. 2 is a longitudinal section taken along the line II-II
in FIG. 1,
[0026] FIG. 3 is a cross-sectional view taken along the line
III-III in FIG. 1,
[0027] FIG. 4 is a perspective view of an open-space photovoltaic
system,
[0028] FIG. 5 shows a single row of the system of FIG. 4 according
to the invention,
[0029] FIG. 5a is a detailed view of a cross-section of a ground
support, wherein the ground support is rigidly installed in the N-S
direction,
[0030] FIG. 5b is a detailed view of an intermediate ground support
cross-section, wherein the ground support is flexibly installed in
the N-S direction,
[0031] FIG. 6a shows a beam with a module rail before tensioning,
and
[0032] FIG. 6b shows a module rail affixed on the beam after
tensioning.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0033] Throughout all the figures, same or corresponding elements
may generally be indicated by same reference numerals. These
depicted embodiments are to be understood as illustrative of the
invention and not as limiting in any way. It should also be
understood that the figures are not necessarily to scale and that
the embodiments are sometimes illustrated by graphic symbols,
phantom lines, diagrammatic representations and fragmentary views.
In certain instances, details which are not necessary for an
understanding of the present invention or which render other
details difficult to perceive may have been omitted.
[0034] Turning now to the drawing, and in particular to FIGS. 1 to
3, there is shown a supporting structure 1 having two parallel rows
3a, 3b of ground supports 5, 5' which are embedded in the ground
13. The ground supports 5, 5' are either directly pile-driven into
the ground or connected with the ground by way of a foundation (not
shown). In both situations, a fixed support for the ground supports
5, 5' is provided on the ground level.
[0035] The rows 3a, 3b are oriented in the terrain in North-South
direction N-S and connected at their upper, i.e., free, end to
joists or beams 7. These are only schematically indicated in FIG. 1
by a line. According to FIG. 3, the connection can be provided by
resting the beams 7 on the end face of the ground supports 5, where
they are then attached (not shown in FIG. 3). Alternatively, the
beams 7 can also be connected with unillustrated beam saddles, so
that the upper end the face of the ground supports 5 forms a flush
surface with the top side of the beam 7. In both situations, the
unsupported distance between the ground supports 5 is bridged in
the East-West direction E-W, i.e., two corresponding ground
supports 5 located at the same location in the row 3a, 3b are
connected with a beam 7. The first beam 7 hence connects the first
ground support 5 of the row 3a with the first ground support 5 of
the row 3b. The following beam 7 then connects the second ground
support 5 of the row 3a with the second ground support 5 of the row
3b, etc.
[0036] According to FIG. 2, beams 7 with a U-shaped profile may
also be used. Conventional fastening means 10, for example clamps,
are arranged between the individual beams 7.
[0037] At least two module rails 9 adapted to receive or support
several photovoltaic modules 11 are installed on the beams 7 in
mutually parallel relationship in the North-South direction N-S.
With this arrangement, all module rails 9 are located in a plane
extending plane-parallel to the ground 13.
[0038] FIG. 2 thus shows a variation of FIG. 3: the beam 7 is here
not a massive beam, but rather a beam with a U-shaped profile,
wherein the web of the profile rests on the end face of the ground
support 5.
[0039] FIG. 4 shows a detail of a photovoltaic system (PV system)
for open-space installation, which includes four rows 3a, 3b, 3c,
and 3d of ground supports 5. A minimum of two rows is required. A
beam 7 is installed from one ground support 5 to the next ground
support 5, wherein each row 3a to 3d includes a continuous a module
rail 9, similar to a model railroad. Alternatively, beams 7 may
span a greater distance than the distance between two ground
supports 5, so that not every ground support 5 has joints. For
example, correspondingly longer beams 7 may abut only at each
second or third ground support 5. In FIG. 4, each beam 7 has eight
module rails 9, which extend in the North-South direction and in
the illustrated example support four adjacent PV modules 11.
[0040] As shown in FIG. 4, these photovoltaic modules 11 are
installed on the module rails 9 at an angle of inclination of, for
example, between 2.degree. and 20.degree..
[0041] FIG. 5 shows a strip of the described PV open-air system,
showing sequentially two ground supports 5 located at a first
position of their respective row 3a to 3b. The eight module rails 9
arranged next to one another on the beam 7 are each implemented as
flat steel tape, which extends continuously across a large portion
of the supports 7. The length of the module rails 9 in form of the
flat steel tape is limited only by the ease with which the spool on
which the flat steel tape is delivered can be handled. A spring 15
is located on at least one end of the flat steel tape. The spring
15 is most easily formed by a corrugation in the flat steel tape.
In the illustrated exemplary embodiment, a spring 15 is provided on
adjacent ends of consecutive module rails 9. A (symbolically
indicated) connecting element 19 joins the two flat steel bands
with each other at the joint 17.
[0042] A corresponding isolator 21 (see FIG. 6a, 6b) which
electrically insulates the connected module rails 9 from one
another is arranged before each spring 15. Such isolators 21 are
known from overhead transmission lines and are used in the present
application to avoid a long, continuous, electrically conducting
metal mass. This is viewed as a cause for an above-average risk for
lightning strikes in PV open-air installations. The isolator 21 can
be omitted if a module rail 9 is made of an electrically insulating
material.
[0043] FIG. 5 also shows detail circles to the FIGS. 5a and 5b,
which illustrate the orientation of the installed
wide-flanged-I-beams (or other IPE-beams) as ground support 5. FIG.
5a shows a cross-section through a ground support 5 which is
fixedly oriented in the N-S direction and in which the module rails
9 extend. If forces develop that act in this direction, then these
forces are absorbed by the ground support 5 and partially
dissipated into the ground.
[0044] The detail circle of FIG. 5 shows the ground support 5 as
installed as an intermediate ground support 5' which is located
between two ground supports 5 that are rigid in the N-S direction.
This ground support 5 is referred to as intermediate ground support
5' and is identical to all other ground supports 5, but has a
different installation orientation. The wide-flanged-I-beam of the
ground supports 5 operating as intermediate ground support 5' is
installed with its rigid flexural characteristic in the E-W
direction, whereas its more flexible flexing direction is oriented
in the N-S direction. In the illustrated embodiment, two
intermediate ground supports 5' a located between two corresponding
ground supports 5. If a joint 17 is required, then this joint 17 is
preferably located between the two intermediate ground supports
5'.
[0045] Alternatively, the ground supports 5 may be round pipes with
different diameters, wherein the rigid ground supports 5 have a
greater diameter than the flexible ground supports 5'.
[0046] A method for installing the supporting structure 1 is
described in more detail with reference to FIGS. 6a and 6b. The
ground supports 5, 5' and the beams 7 are introduced into the
ground in a conventional manner, until they are plane-parallel with
respect to the ground 13. The flat steel forming the module rail 9
is then unwound from a spool (not shown) and placed onto the beam
7, so that the module rail 9 sags between the beams 7--similar to
an overhead transmission line. FIGS. 6a and 6b also show that the
module rail 9 has an opening 23 which is located in FIG. 6a
noticeably beyond and to the left of the center of the beam 7. The
beam 7 is here constructed--as viewed in cross-section--as a
pot-shaped metal part, with an inner pot bottom abutting the free
upper end face of the ground support 5. Before the module rail 9 is
unwound and positioned, it is attached to a ground support 5 (not
shown in FIG. 6a) which is rigidly installed in the N-S direction.
The result is the illustration of FIG. 6a, where the opening 23 is
located to the left of the beam center. A winch is connected to the
unattached end of the module rail 9, which pulls the module rail 9,
which is attached only at the left side, in the direction of the
arrow 25.
[0047] The winch is operated until the module rail 9 is tightened
to a point where all openings separated by the same spacing as the
spacing between the beams 7 are located on top of the respective
beam 7. This position is illustrated in FIG. 6b for a beam 7
positioned with one of its ends on the right. The module rail 9 is
then affixed on the beam 7, for example with a conventional
screw-nut connection 27.
[0048] FIGS. 6a and 6b further illustrate a first insulation means
29 which electrically insulates the module rail 9 from the beam 7.
Also shown is a second insulation means 31, which electrically
insulates the beam 7 from the ground support 5. Both measures are
intended to prevent large, electrically contiguous masses of metal
to reduce the risk of a lightning strike.
[0049] In summary, a supporting structure 1 for an open-space
photovoltaic system is advantageously provided, which has several
ground supports 5, 5' which rise at one end from the ground, with
beams 7 resting on the other end, wherein module rails 9 are
secured on the beams 7 to which then fastening means, in particular
clamps, for photovoltaic modules 11 can be attached. The ground
supports 5 form at least two aligned rows 3a, 3b having each at
least three ground supports 5 oriented it essentially North-South
direction. A corresponding beam 7 is installed substantially in the
East-West direction on or between ground supports 5, 5' disposed at
the same position in the row 3a, 3b. At least two module rails 9
are attached on or between two respective adjacent beams 7 in
essentially North-South direction. The other ends of the ground
supports 5, 5' are at the same level above terrain ground 13, so
that the beams 7 and the module rails 9 extend it essentially
plane-parallel to the terrain ground 13. This arrangement enables
an effective installation with little material consumption, and the
supporting structure 1 exposes only a small effective surface area
to wind gusts. Each row 3a, 3b of ground supports includes ground
supports 5, 5' with partially relatively rigid and flexible
flexural characteristics.
[0050] While the invention has been illustrated and described in
connection with currently preferred embodiments shown and described
in detail, it is not intended to be limited to the details shown
since various modifications and structural changes may be made
without departing in any way from the spirit and scope of the
present invention. The embodiments were chosen and described in
order to explain the principles of the invention and practical
application to thereby enable a person skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated.
* * * * *