Use of pre-curved bars in photovoltaic systems and associated racking systems

Abstract

Photovoltaic system (1), with - a supporting structure (2) that supports several photovoltaic modules (3), - wherein the supporting structure (2) comprises several posts (4) preferably designed in the form of metallic longitudinal profiles (5) and associated beams (6) extending transversely to the posts (4) and - wherein the bars (6) are attached, at least indirectly, to the posts (4) extending in a z-direction and each connect two adjacent posts (4) to each other, at least indirectly, characterized in that - that individual bars (6) are designed as pre-curved bars (11) by means of pre-curved longitudinal profiles (8) which, in an unloaded rest state, exhibit a longitudinal profile bent about a y-axis.

Description

[0001] The invention relates to a photovoltaic (PV) system based on a support structure that carries several PV modules. The support structure comprises several posts and associated crossbeams extending transversely to the posts. Preferably, both the posts and the crossbeams can be designed as longitudinal metallic profiles. The crossbeams are attached to the posts, at least indirectly or directly, in a manner known per se, with the posts extending in the vertical z-direction. Thus, the crossbeams connect two adjacent posts (at least indirectly or directly).

[0002] Such supporting structures and PV systems are generally known, for example from EP 3 560 098 B1.

[0003] Starting from this state of the art, the invention is based on the objective of providing an improved supporting structure that is optimized in terms of material usage and thus in terms of costs.

[0004] To solve this problem, the features of claim 1 are provided according to the invention for a PV system. In particular, according to the invention, to solve the problem in a PV system as described above, it is proposed that individual beams are designed by means of pre-curved longitudinal profiles. These so-called pre-curved beams thus exhibit a curved longitudinal profile in an unloaded rest state. The bend of the longitudinal profile is oriented about a y-axis, which runs perpendicular to an x-axis, the latter corresponding to the x-longitudinal direction of the respective pre-curved beam (compare Fig. 1).

[0005] This invention is applicable to both conventional PV systems based on monofacial PV modules and to vertical PV systems where bifacial PV modules are mounted upright on the support structure. For example, in the case of support structures for solar fences, monofacial PV modules can also be mounted upright on such a support structure according to the invention, depending on the location.

[0006] The invention thus provides for pre-curved beams that are pre-curved against the weight force of the respective PV module that the beam is intended to support. A "curved longitudinal profile" can therefore be understood in particular to mean that the course of a neutral fiber (which can coincide with the geometric centroid of the cross-sectional area of ​​the pre-curved beam) in an x-direction of the respective pre-curved longitudinal profile deviates significantly from a (straight) longitudinal axis of the beam, in particular by more than 5% of a (maximum) cross-sectional height H of the beam (measured in the vertical direction; this can, for example, correspond to the longitudinal axis of the posts in a vertical PV system with upright bifacial modules).In individual cases, this deviation can even be at least 10%, at least 15% or even at least 20% of the aforementioned cross-sectional height H, depending on the load-bearing capacity that the respective beam in the construction must bear.

[0007] The pre-curvature / pre-bending occurs along a vertical z-axis relative to the cross-section of the beam (more precisely, its vertical height H) and its subsequent installation within the supporting structure. This means that the pre-curvature is oriented against gravity in the installed position. The z-axis corresponds to the vertical direction along which the posts are aligned (more or less precisely, when installed in open fields).

[0008] Pre-curving the beams allows for a reduction in wall thickness, as a certain degree of deflection under the weight of the PV modules can now be tolerated, since the pre-curving fully or at least partially compensates for this deflection. As a result, the pre-curved beams can exhibit a largely straight profile in the final installation, thus achieving a planar appearance of the supporting structure after the PV modules are installed.The invention takes advantage of the knowledge that even with constant material thickness and appropriate selection of the cross-sectional shape of the bars, they can be designed in such a way that the bars have sufficient static reserves in the horizontal direction, in which wind loads act on the PV system and are also transferred to the bars, so that sufficient mechanical stability in this direction can be ensured.

[0009] In other words, the pre-curved beams, designed as pre-curved longitudinal profiles, exhibit a pre-curvature K, which can be defined as the maximum deviation of the neutral fiber of the longitudinal profile from an (imaginary) longitudinal axis of the beam, as will become clear with reference to the figures. This deviation can be understood as the deviation of the center of gravity curve SK(x) of the beam's cross-sectional area from the straight axis along which the beam runs (in the final installation position). This axis will generally coincide more or less closely with the horizontal, although some deviations may occur if the actual installation position differs from the desired one, for example, due to an inclination of the posts. If a deliberate inclination of the beam's longitudinal axis to the horizontal is already incorporated into the design of the supporting structure, the pre-curvature K can be somewhat smaller (for the same load-bearing capacity): because...For example, if the angle of inclination is 20° to the horizontal, then due to the load-bearing capacity only a force perpendicular to the longitudinal axis of the bar acts on the bar, which is reduced by a factor of cos(20°)<1.

[0010] In their final assembly position within the supporting structure, the pre-curved beams are arranged and aligned such that the aforementioned pre-curvature K points upwards in the vertical direction, thus opposing the vertical load direction in which the weight of the respective PV module supported by the pre-curved beam acts upon it. This also applies when the longitudinal axis of the beam is inclined relative to the horizontal.

[0011] Ideally, the pre-curvature K and the material thickness of the pre-curved longitudinal profile forming the respective pre-curved bar can be selected such that, under the influence of the aforementioned weight forces (load-bearing load acting on the bar), the pre-curved bar maintains a substantially straight path along its longitudinal axis in the final assembly position. "Substantially straight" here can be understood to mean, in particular, that any (negative) deflection or remaining (positive) residual curvature K resulting from the application of the weight force is minimal. res The residual curvature of the pre-curved beam must be less than + / -3% of the beam's cross-sectional height H in the vertical direction. However, larger residual curvatures or deflections may still be acceptable, for example, if identical pre-curved beams are used throughout the supporting structure, but the load-bearing capacity varies from beam to beam within the structure.

[0012] From another perspective, the invention proposes the use of pre-curved longitudinal profiles intended to serve as pre-curved beams in the support structure of a photovoltaic system. As previously explained, these pre-curved beams are each designed with a pre-curved longitudinal profile that exhibits a curved longitudinal profile in an unloaded rest state. In addition to the aforementioned beams, the support structure comprises vertically extending posts and a multitude of PV modules arranged in corresponding mounting bays between the posts. According to the invention, in such a situation, the pre-curved beams are each subjected to a load acting transversely to a longitudinal direction of the beam.are pre-curved to such an extent that (when the pre-curved beam is subjected to the load) a desired shear center is achieved, the spatial position of which, compared to the horizontal width of the beam, deviates by less than 20% (preferably by less than 10%) from the position of a shear center of a comparable beam of the same cross-section, but which is straight and not loaded. This is advantageous because, under wind loads, the torsion occurring in the curved (and loaded) beam is reduced compared to a straight beam in the same situation.The shear center (sometimes also called the shear force center or torsional rest point) can be understood here as the (imaginary) point on a cross-section of the respective beam on which a resulting shear force must act to achieve a torsion-free force application, where no torsion is exerted on the cross-section. The load is caused by at least one PV module, which is supported by the respective beam. In the final mounting position, the load acts (following the force of gravity) perpendicular to the longitudinal direction of the pre-curved beam (i.e., downwards). The pre-curved beams can connect two adjacent posts of the supporting structure, either directly or indirectly. Depending on the design of the PV system, other configurations are also possible.

[0013] Thus, the degree of pre-curvature of the curved beam can be designed, depending on the load-bearing capacity, so that the shear center of the curved profile is optimized in its final mounting position within the supporting structure (where the load then acts on the respective curved beam), as it is comparable to the location of the shear center of an unloaded, straight beam. This has the particular advantage of minimizing / reducing torsional moments that arise in the curved beam when wind loads act on the PV modules and thus on the supporting structure, which is beneficial for the mechanical strength of the supporting structure. Because of this advantage, the amount of material used in the beam can also be minimized, saving costs. Therefore, when wind loads act, no significant (i.e., negligible) torsion of the beam is caused.Torsion is negligible at least if the torsion of the loaded and curved beam caused by a wind load is at most 20% higher than the torsion that would occur in a beam with an identical cross-section if it were designed without curvature and not loaded with a load.

[0014] The inventive design and use of curved beams in the supporting structure thus maintains a desired ideal or nearly ideal shear center, even when the beam is subjected to the weight forces of the PV modules it supports. This effectively prevents a shift of the shear center in the vertical direction and, consequently, twisting / torsion of the beam's cross-section under wind loads. In other words, additional torsional moments can be eliminated. The result is a supporting structure that is extremely stable and can withstand high wind loads.

[0015] Further advantageous embodiments, as claimed in the dependent claims, are explained below: It is possible to arrange the PV modules upright on the supporting structure. This makes particular sense if the PV modules are bifacial (so that they can receive sunlight from either the front or the back and convert it into electricity).

[0016] Furthermore, the invention is also applicable to PV systems where the PV modules are oriented at an angle to the vertical / z-direction and / or horizontally. In these cases, as well as in others, the PV modules can also be monofacial. This is because, regardless of the orientation, the PV modules generate a load that can be absorbed by the pre-curved bars according to the invention.

[0017] The pre-curved beams can be characterized, for example, by the fact that, in an unloaded state, the respective geometric center of gravity S of a yz cross-sectional area A of the respective pre-curved longitudinal profile follows a curved center of gravity curve SK in one x-longitudinal direction of the beam. The center of gravity curve SK(x) can deviate from one x-longitudinal direction of the respective pre-curved beam by more than 5% of a cross-sectional height H of the pre-curved beam in an unloaded state. In a final assembly position (i.e., when the beam is fully mounted to the two adjacent posts and the weight of at least one PV module acts on the pre-curved beam), the respective center of gravity curve SK of the respective pre-curved beam can exhibit a resulting residual curvature in the vertical direction under the influence of a weight force caused by at least one of the PV modules.Ideally, this residual curvature should be less than 3% of the cross-sectional height H. However, instead of residual curvature, a deflection (then in the opposite direction of bending to the initial curvature) of ideally less than -3% of the cross-sectional height H in the final assembly position can also result.

[0018] The pre-curved longitudinal profiles that form the pre-curved bars can be produced, for example, by a rolling process (especially cold rolling), i.e., profiled. Alternatively or additionally, it can be provided that a pre-curvature K of the longitudinal profiles is produced either during rolling or by means of a subsequent post-processing step. This post-processing step can, for example, involve bending the longitudinal profiles under compression or tension about a transverse axis that runs perpendicular to an x-longitudinal direction of the longitudinal profiles. Alternatively, the aforementioned post-processing step can also be an additional rolling step that leaves the cross-section of the longitudinal profiles unchanged.

[0019] In the roll forming process for the longitudinal profiles of the beams, as described above, metallic strips, particularly steel, can serve as the starting material. The strip passes through several profile rolling stations in succession, with each station progressively deforming the strip towards the desired profile cross-section. In this way, for example, C-, S-, U-, or Ω-shaped cross-sections can be produced in the longitudinal profiles.

[0020] Alternatively, “curved bars” or “pre-curved longitudinal profiles” within the meaning of the invention can also be obtained from edge-formed parts which are pre-curved by means of a downstream process such as pressing, or press edges, or press edges with downstream bending.

[0021] It can be provided that all beams of the supporting structure have identical wall thicknesses, which has the advantage that the beams can be manufactured from a common raw material. In such a design, it can be provided that some of these beams have no pre-curvature K (and are thus designed as straight beams).

[0022] Such a configuration represents only one preferred and possible embodiment; naturally, the pre-curved beams according to the invention can also differ within the supporting structure in terms of wall thickness and / or the cross-sectional profile used. Thus, in particular, different types of pre-curved beams according to the invention can be used within a supporting structure according to the invention.

[0023] For example, even uppermost beams, to which only the PV modules located below are mounted, can be designed without pre-curvature, particularly if the weight of the PV module is primarily borne by another beam located below it. This means that both pre-curved and non-pre-curved beams can be used in a support structure according to the invention.

[0024] The pre-curved beam used in the supporting structure can, for example, be the bottom and / or middle beam of the structure. Such bottom or middle beams each support at least one, or even two, PV modules arranged above them. These features can be implemented in both conventional PV systems with stacked monofacial PV modules and vertical PV systems with stacked bifacial PV modules in the same module plane.

[0025] Another embodiment provides that individual bars are formed by a pair of two interconnected longitudinal profiles arranged vertically one above the other. Such an arrangement can be understood as a bar assembly consisting of two individual bars. It is preferred that the two longitudinal profiles of the bar assembly are arranged directly above one another. Furthermore, it can be provided that a first longitudinal profile of the bar assembly is a pre-curved longitudinal profile, while a second longitudinal profile of the bar assembly is a straight, non-pre-curved longitudinal profile. With a suitable connection, e.g., by means of a screw connection, the straight longitudinal profile, after being connected to the curved longitudinal profile arranged above it, can maintain a tensile force on the curved longitudinal profile, whereby the tensile force counteracts any straightening of the upper curved longitudinal profile as soon as it is subjected to the weight of the PV modules.This also allows for a higher load-bearing capacity of the supporting structure, when using comparatively delicate longitudinal profiles for the beams.

[0026] To solve this problem, the invention also proposes a frame system comprising several posts and beams. The frame system, and in particular its beams, is / are designed such that a supporting structure can be erected on the basis of the frame system using fasteners (such as screws) or connecting elements (which, for example, create a clamping connection). This supporting structure allows for the construction of a photovoltaic system, as previously described or claimed here, after the installation of appropriate (especially bifacial) PV modules. In other words, this frame system provides that some of the beams are designed as curved beams, exhibiting a curved longitudinal profile and thus a pre-curvature K in an unloaded rest state.

[0027] The invention will now be described in more detail with reference to exemplary embodiments, but is not limited to these embodiments. Further embodiments of the invention can be derived from the following description of the figures in conjunction with the preceding general description, the claims, and the figures themselves.

[0028] In the following description of various preferred embodiments of the invention, elements that are identical in function are given identical reference numerals even if they differ in design or shape.

[0029] It shows: Fig. 1 a “pre-curved bar” designed according to the invention with a pre-curvature K in a side view, Fig. 2 the same pre-curved bar in a slightly twisted side view, Fig. 3 a perspective view of a supporting structure of a PV system according to the invention, Fig. 4 a detailed view of the lowest, pre-curved beam of the supporting structure made of Fig. 3, Fig. 5 the supporting structure made of Fig. 3, with PV modules now installed in the right-hand mounting fields, Fig. 6 the supporting structure made of Fig. 4, with PV modules now additionally installed in the left mounting fields, so that a PV system is obtained, Fig. 7 a front view of a PV system according to the invention with bifacial PV modules mounted upright on the supporting structure, and finally Fig. 8-10 the views of Fig. 3, Fig. 5 and Fig. 6 each in a view from a slightly oblique front angle.

[0030] The Fig. Figure 7 shows a photovoltaic (PV) system, designated as a whole by 1, which is based on a support structure 2 comprising several posts 4 designed as longitudinal metallic profiles 5 and associated transverse beams 6. Bifacial PV modules 3 are mounted upright on the support structure 2, specifically on the transverse beams 6, by means of separate module mounting elements 17, which are inserted into corresponding slots formed in the transverse beams 6. Thus, the transverse beams 6 initially absorb the respective load of each PV module 3 and transfer these forces to the posts 4. The middle bars 6b, which separate the upper mounting fields 21a from the lower mounting fields 21b, as well as the uppermost bars 6c, are each designed as non-pre-curved bars 12 / as straight bars 12 and therefore do not have a pre-curvature K, as can be seen in particular by comparing bars 6b and 6a in Fig. 3 recognizes (see also) Fig. 7).

[0031] In Fig. 7, but also, for example, in Fig. Figure 3 shows that the posts 4 are designed in a known manner as two parts, with an upper holding section 14 designed as a longitudinal profile 5 and a lower fastening section 15 designed in the form of a C-shaped driving profile 5, which has been driven into the ground 19. The two longitudinal profiles 14 and 15 are screwed together by means of the screw 16a.

[0032] The upper retaining sections 14 of the posts 4 each provide through-holes 13 into which the rails 6 are inserted to a greater or lesser depth. In the area of ​​each through-hole 13, the longitudinal profile 5 of the post 4 or the retaining section 14 forms a pair of tabs 18, with the rails 6 being screwed to the tabs 18 by means of the illustrated screw connection 16b. In other words, the rails 6 are thus directly connected to the respective post 4 / the respective longitudinal profile 5.

[0033] As the Fig. As illustrated in Figures 1-3, the lowest beams 6a of the supporting structure 2 are designed as pre-curved beams 11, namely by means of pre-curved longitudinal profiles 8. The [unclear text] in the Fig. 1 and Fig. The pre-curved longitudinal profile 8 shown in Figure 2 was first produced as a straight longitudinal profile 8 using a rolling process and then subjected to post-processing to imprint an additional pre-curvature K into the longitudinal profile 8. This is evident in the Fig. 1 and Fig. 2, that both the upper edge 20 and the lower edge 22, which before post-processing still ran strictly along the x-longitudinal direction 9 of the longitudinal profile 8, now show a longitudinal path curved around the y-axis. If, for example, as in Fig. 2 If the left end of the pre-curved bar 11 is aligned strictly horizontally, i.e. parallel to the x-direction, a pre-curvature K can be seen at the right end of the bar 6a. max .

[0034] In Fig. Figure 1 further illustrates the course SK(x) (center of gravity curve) of the geometric center of gravity S of the yz cross-sectional area A of the pre-curved longitudinal profile 8. It can be seen that this center of gravity curve SK(x) shows a curved course in the x-longitudinal direction 9 of the beam 6a.

[0035] How to in Fig. As can be seen in Figure 3, the pre-curved bars 11 have a W-shaped yz cross-section (with the opening of this semi-open cross-section facing downwards), such that the aforementioned center of gravity S lies within this yz cross-sectional area A. While in the situation of Fig. 3. The fact that the two lowest beams 6a there, in their unloaded state, continue to show a curved course can be seen in Fig. 5, that the lower right-hand bar 6a, which is already loaded with the PV module 3a, in the final mounting position shown and under the influence of the weight of the PV module 3a, exhibits a center of gravity curve SK with a residual curvature K res shows that less than + / - 3% of the in Fig. 2 and in Fig. 3 illustrated z-cross-sectional height H of the longitudinal profile 8 has (in Fig. Figure 3 also illustrates the y-cross-sectional width B of the bar 6b).

[0036] Is the bar 6a, i.e. the pre-curved longitudinal profile 8, as in Fig. Figure 3 illustrates that, when mounted as a pre-curved beam 11 in the lowest position of the supporting structure 2, a curvature profile K(x) results, as shown in Fig. 1 is illustrated and also in Fig. 3 can be seen in the two lower bars 6a, 6b (but not in the upper bars 6b). This curvature profile K(x) is also visible in the view of the Fig. 4 can be seen, where the module holding elements 17 are already mounted in the lowest, pre-curved bars 6a, 11.

[0037] The Fig. 5 and the Fig. Figure 6 illustrates how the individual mounting fields 21, provided by the supporting structure 2, are gradually fitted with PV modules 3. In the Fig. In the figure 5, the lowermost pre-curved bar 6a, 11 on the right is already loaded with the lower PV module 3a located there, and accordingly the lower edge 22 of the lowermost bar 6a on the right now runs approximately horizontally (compare the dashed line), while the lower edge 22 of the lowermost bar 6a on the left, which is not yet loaded with a PV module 3, continues to show a curved shape.

[0038] In the detailed view at the bottom of the Fig. Figure 7 indicates, by means of a dashed line, the position of the pre-curved longitudinal profile 8, which forms the left, lowest beam 6a. It can be seen that the beam 6a / 11 has deformed downwards due to the influence of the weight of the left, lower PV module 3a, so that on the one hand a straight course of its lower edge 22 is now visible and also a deflection of the beam 6a in the negative z-direction, namely by the amount Δz.

[0039] The respective situation of Fig. 3, Fig. 5 and Fig. 6 is also shown again from a steeper angle in the Fig. 8-10 illustrated.

[0040] In summary, to optimize material usage and thus costs, the use of pre-curved, metallic longitudinal profiles 8 as horizontally extending beams 11 of a supporting structure 2 of a PV system 1 is proposed. The pre-curved beams 11 are deformed by the weight of at least one PV module 3 supported by the beam 11 in such a way that any pre-curvature K (existing in the unloaded state) is largely eliminated, resulting in a substantially straight profile of the beam 11 in its final assembly position under load. In this way, a preferred location of the shear center of the longitudinal profile 5 under load can be ensured, which is advantageous for reducing or limiting torsional stress on the beam 11 when wind forces act on the PV modules 3. Fig. 5). Reference symbol list 1 photovoltaic system 2 Supporting structure 3 photovoltaic modules 4 posts 5 Longitudinal profile 6 bars 7 Frame system (includes 4 and 6, but not 3; used to assemble 2) 8 pre-curved longitudinal profile 9 Longitudinal direction (of 6 / 8) 10 Longitudinal direction (of 4) 11 pre-curved bars (especially middle and bottom bars) 12 straight bars (e.g., topmost bars that do not bear any weight; such bars do not have any pre-curvature K according to the invention) 13 Through-hole 14 Stop section 15 Fastening section 16 screw connection 17 module holding elements 18 tabs (bent open; used for mounting 6 to 4; formed by 5; shape defined by 13) 19 Soil 20 Top edge (of 5 / 6) 21 Assembly area (provided by 2 for 3) 22 Bottom edge (of 5 / 6) Geometric sizes K Pre-curvature (more precise curvature profile K(x)) A cross-sectional area (of 8) H Cross-sectional height (of 8 / A) B Cross-sectional width (of 8 / A) S center of gravity (of A) SK center of gravity curve (= course of S along the longitudinal direction of 8) QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 3 560 098 B1

[0002]

Claims

[1] Photovoltaic system (1), with - a supporting structure (2) that supports several photovoltaic modules (3), - wherein the supporting structure (2) comprises several posts (4) preferably designed in the form of metallic longitudinal profiles (5) and associated beams (6) extending transversely to the posts (4) and - wherein the bars (6) are attached, at least indirectly, to the posts (4) extending in a z-direction and each connect two adjacent posts (4) to each other, at least indirectly, characterized by , - that individual bars (6) are designed as pre-curved bars (11) by means of pre-curved longitudinal profiles (8) which, in an unloaded rest state, exhibit a longitudinal profile bent about a y-axis. [2] Photovoltaic system (1) according to claim 1, wherein the photovoltaic modules (3) - arranged upright on the supporting structure (2) and / or bifacially designed or - are inclined to the vertical and / or horizontally aligned and / or monofacial in design. [3] Photovoltaic system (1) according to claim 1 or 2, - wherein in the unloaded state a respective geometric center of gravity S of a yz cross-sectional area A of the respective pre-curved longitudinal profile (8) in a longitudinal direction (9) of the beam (6) follows a curved center of gravity curve SK(x), - wherein the center of gravity curve SK in the unloaded state deviates by more than 5% of a cross-sectional height H of the pre-curved beam (11) from an x-longitudinal direction (10) of the respective pre-curved beam (11), - in particular, in a final assembly position, under the influence of a weight force in the vertical direction caused by at least one of the photovoltaic modules (3), the respective center of gravity curve SK of the respective pre-curved bar (11) shows a resulting residual curvature of less than +3% or a deflection of less than -3% of the z-cross-sectional height H. [4] Photovoltaic system (1) according to any one of the preceding claims, - wherein the pre-curved longitudinal profiles (8) are / were produced / profiled by means of a rolling process, in particular by means of cold rolling and / or - wherein a pre-curvature K of the longitudinal profiles (8) (i) during rolling or (ii) were produced by means of subsequent post-processing. [5] Photovoltaic system (1) according to the preceding claim, wherein the post-processing, (a) bending of the longitudinal profiles (8) under compression or tension about a y-transverse axis extending transversely to an x-longitudinal direction (9) of the longitudinal profiles (8) or (b) is an additional rolling process which leaves a cross-section of the longitudinal profiles (8) unchanged. [6] Photovoltaic system (1) according to one of the preceding claims, wherein all beams (6) of the supporting structure (2) have identical wall thicknesses, but some of the beams (6) do not have a pre-curvature K and are thus designed as straight beams (12). [7] Photovoltaic system (1) according to one of the preceding claims, wherein the pre-curved bars (6) are the lowest and / or middle bars (6) of the supporting structure (2), each supporting at least one or even two photovoltaic module(s) (3) arranged above the respective bar (6). [8] Photovoltaic system (1) according to any one of the preceding claims, - wherein individual bars (6) are formed as a bar package by a pair of two interconnected and vertically superimposed longitudinal profiles (8a, 8b), - wherein the two longitudinal profiles (8a, 8b) of the bar package are arranged directly above one another and - wherein a first longitudinal profile (8a) of the bar package is a pre-curved longitudinal profile (8), while a second longitudinal profile (8b) of the bar package is a straight, non-pre-curved longitudinal profile (8). [9] Frame system (7) comprising several posts (4) and crossbars (6), - wherein the frame system (7), in particular the bars (6), is / are designed such that a supporting structure (2) can be built on the basis of the frame system (7) and using fastening means such as screws or connecting means, with which, after mounting corresponding photovoltaic modules (3), a photovoltaic system (1) according to one of the preceding claims can be realized, - wherein individual bars (6) of the frame system (7) are designed as curved bars (11) which in an unloaded rest state exhibit a curved longitudinal profile and thus a pre-curvature K.

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