Patent Publication Number: US-2011073155-A1

Title: Module for converting solar radiation into electricity

Description:
The invention relates to a module for converting solar radiation into electricity comprising a panel with a first and second main side, wherein solar energy converting means are arranged on or in the first main side of the panel and, furthermore, comprising a means for fixing the module to an object. 
     In such modules the solar radiation converting means are encapsulated to render the solar radiation converting means, for example in the from of crystalline solar cells or substrates with thin light absorbing layers, resistant against harmful environmental conditions and to satisfy the static requirements necessary for fixing the modules to an object, like the roof or wall of a building or directly greenfield. 
     A first kind of solar modules present on the market comprises a front layer, a solar radiation-converting layer (also called active layer), an adhesive layer and a backside plastic film. This type of layer structure does not yet satisfy the static requirements and is thus provided with a metal frame, typically out of aluminum, to provide the necessary mechanical stability. Due to this metallic frame, this kind of module becomes expensive. 
     A second kind of module, which is particularly applied to thin film solar modules, comprises a front glass layer, a thin solar radiation converting layer (also called the active layer), an adhesive layer and a backside glass layer. Compared to the first kind of module, no metallic frame is necessary as the back glass plate provides the necessary mechanical stability. As a consequence, cheaper modules can be fabricated. 
     Nevertheless also this kind of module represents disadvantages. To fix the module to an object four metallic clamps are attached to the edge region of the solar module (two on each side) by sandwiching the module in between the two legs of each clamp. The clamps furthermore provide the possibility to fix the module to a suitable frame using bolts. 
     The use of clamps in the technology without a metallic frame has however, the following problems. First of all, to prevent corrosion effects, it is mandatory that the metallic clamps are electrically isolated from the module, which renders the design of the clamps more complicated and thus more expensive. 
     Second, the mounting of the module at four points leads to a high, localized mechanical stress level under static load arising, for example, under windy conditions. These locally important stress peaks lead to a damaging of the module. To counter this negative effect, the glass plates, in particular the backside glass layer, need to have an important thickness and have to be hardened, like a so called TVG glass with 6 to 8 mm thickness. This leads to an increase in weight, which in turn leads not only to higher fabrication costs but also to a more difficult mounting of the modules. 
     In addition, the region where the clamps are to be fixed is free from solar radiation transforming means, thereby reducing the efficiency per m 2  as not the total surface of the panel can be used to obtain electricity. 
     Finally, the accumulation of dirt usually accompanied by the presence of humidity in the vicinity of the clamps, which protrude slightly above the surface plane of the solar module, has a negative impact on the lifecycle of the modules. In fact, the edge region of the laminate represents the weakest region of the laminate, as humidity can enter via the layer interfaces and damage the active layer by corrosion. 
     It has been proposed to provide a clamping mechanism, which uses clamps screwed to the edge of the panel and on the backside thereof. These clamps project laterally over the edge of the panel so that the panel can be fixed. Also with this kind of solution, the problem of dirt accumulation occurs and furthermore also high localized mechanical stress. In addition, the protruding parts make the overall surface area of the panel larger, which raises transportation costs. Finally the fixed position of the clamp renders the fixing of the module to a frame rather difficult. 
     To cope with these requirements, the known products either provide expensive aluminum frames or thick glass layers together with complicated clamps. Finally, the accumulation of dirt remains an unsolved problem. 
     It is therefore the object of the present invention to provide a module for converting solar radiation into electricity which overcomes the abovementioned problems, is cheaper to fabricate, easier to mount and provides a longer lifecycle. 
     This object is achieved with the module for converting solar radiation into electricity according to claim  1 . Accordingly, the module for converting solar radiation into electricity comprises a panel with a first and second main side, wherein a solar radiation converting means is arranged on or in the first main side and a means for fixing the module to an object. 
     According to the invention, the means for fixing the module is arranged over the back main side of the panel and with a clearance with respect to the edge. 
     By providing the means for fixing the module over, in particular on, the back main side of the panel and away from the edge, there is no need to provide special isolating means to electrically isolate the means for fixing from the edge side walls of the panel as any electrical contact between the means for fixing and the active radiation converting means can be prevented due to the special geometrical arrangement, which keeps fabrication costs low. Furthermore, by providing a clearance between the edge region of the panel and the fixing means, any dirt which could eventually accumulate at or near the means for fixing the module can not reach the weak spot of the panel, namely the edge region, so that a corrosion of the solar radiation converting means can be prevented, at least to a large extent. Thus, with the inventive module the lifecycle of the module can be improved. 
     In this context “over” means that the means for fixing is either directly provided on the backside of the panel or on the backside of any additional layers, e.g. spacers or reinforcement members, that could be provided on the backside of the panel. Furthermore, the term “clearance” means that the means for fixing is spaced away from the edges of the panel. In addition, providing the solar radiation energy converting means on or in the front main side corresponds to an arrangement in which the solar radiation energy converting means are such that it can be reached by the solar radiation. 
     Preferably, the distance between the edge and the means for fixing can be at least 1 cm, in particular more than 5 cm. Dirt accumulation in the vicinity of the edge region can be prevented for a clearance value in this value range. 
     According to a variant, the means for fixing is configured such that, when seen from above, it is completely positioned inside the external contour of the panel. Therefore the fixing means is invisible, when the module is mounted. 
     Preferably, the means for fixing can be oblong and, in particular, extend over a range of about 20-95%, in particular 50-90% of the longest dimension of the panel of the module. By providing a fixing means that extends over a large surface area, a high stress load which might occur under windy weather conditions, can be distributed over a large part of the panel and thereby damage to the panel can be prevented. 
     According to a variant, the means for fixing can be oblong and, in particular, extend over a range of about 20-95%, in particular 50-90% of the smaller dimension of the panel of the module. By providing a fixing means that extends over a large surface area, a high stress load which might occur under windy weather conditions, can be distributed over a large part of the panel and thereby damage to the panel can be prevented. 
     Advantageously, the means for fixing the module can be attached to the back main side of the panel by gluing. Gluing has the advantage that the panel itself does not need to be damaged to achieve fixing. Furthermore the process can be realized in an automated way. Finally, gluing provides a reliable long lasting connection between the two parts. Even more preferred is an attachment by gluing, for which an elastic connection between the two parts—panel and means for fixing—is achieved which will be able to attenuate deformations. 
     Preferably, the means for fixing the module can comprise at least one profile, in particular an u-shaped metal profile or a z-shaped metal profile. In case of a u or z-shaped profile, the surface of one leg can be used to attach the means for fixing of the module to the panel and the other leg can be used to attach the module to the object, by e.g. using clamps, screws etc. 
     The object of the invention is also achieved with the module according to claim  7 . This module for converting solar radiation into electricity comprises a panel with a front and back main side, wherein solar radiation converting means are arranged on or in the front main side and a means for fixing the module to an object on the backside of the panel. The means for fixing the module is furthermore configured to mechanically engage with a fixing device of the object by a clamp connection. This module can be combined with any one of the features of the module as already described above individually or in combination. 
     A clamp connection has the advantage that no additional parts or pieces are necessary to achieve the fixing of the module with the fixing device and, thus, facilitates the mounting of the module. The frictional forces between the means for fixing and the fixing device are sufficient to keep the module in place. 
     Preferably, the means for fixing the module can be configured to engage by snapping into the fixing device. Such a snapping-in further prevents an unwanted displacement of the module with respect to the fixing device, as in addition to frictional forces also mechanical forces prevent a movement. The module can be configured to prevent movement by snapping-in in one or more directions. Preferably the snap-in connection is realized such that a release of the connection can be achieved. 
     Preferably, the means for fixing can comprise a tongue with a projection for snapping into a corresponding recess in the fixing device. This further serves to stabilize the connection between module and fixing device. According to a variant, the projection and the recess could be configured such that e.g. using an undercut in the recess and corresponding hook-like projection, an unwanted release can be prevented. This feature can thus be used as an anti-theft measure. 
     Advantageously, the tongue can be flexible. This feature facilitates a relative movement between the fixing means and the fixing device and enables a release of the connection if necessary, e.g. to exchange a defective module. 
     The means for fixing can advantageously comprise a first means having a first groove, in particular an u-shaped profile and a second means having a second groove, in particular an u-shaped profile, wherein the first and second groove face in opposite directions. In this context the direction attributed to a groove corresponds to the surface normal of the opening of the grooves and which directs towards the outside of the groove away from the corresponding means. 
     Preferably at least one means can furthermore comprises a tongue with a projection. 
     According to a preferred embodiment, the panel can comprise a front layer, an active layer, and a backside layer, at which the means for fixing the module is arranged. In this context, the active layer comprises the solar energy converting means which are for example deposited in the form of thin films onto the front layer. Typically an adhesive layer is provided to attach the backside layer to the other layers. Nevertheless, the active layer could also be provided on the backside layer and this structure is then attached to a front layer. Thus, even a solar module having a laminated structure without a metal frame can thus be easily fixed to an object without the negative effects as described above. Furthermore, with the same thickness of the structure, the module can be used under harsher conditions compared to the above described laminate module, as the static load the module according to the invention can support is at least up to a factor two better. 
     Advantageously, the front and/or backside layer can be out of glass, in particular non hardened float glass, and can have a thickness of less than 5 mm, in particular less than 3.5, more in particular of 3 or 3.2 mm. Compared to the solar modules on the market, a thinner glass layer can be used for the same static load conditions, as the fixing means on the backside releases the mechanical requirements of the module by at least up to about a factor two compared to the fixing clamps used in the known devices. With the released mechanical requirements, it becomes even possible to use plastic sheets or foils instead of the glass layer. This advantage is particularly important for standard modules with a size of 1100 mm*1300 mm, as the weight reduction is important. 
     The object of the invention is also achieved with the fixing device for receiving a module for converting solar radiation into electricity like described above. This fixing device comprises a profile with a groove configured to receive the means for fixing the module of the module for converting solar radiation into electricity. In the embodiment realizing a clamping connection between the fixing device and the solar module, the especially adapted profile of the fixing device allows for a safe and easy mounting of the module on the fixing device of the object, without the necessity of additional means, like bolts etc. 
     Advantageously, the profile has a groove configured to at least partially receive the projection of the tongue of the means for fixing of the module. In this configuration, a snap-in connection (click-in) is realized which prevents a relative displacement of the module with respect to the fixing device at least along one direction. 
     Preferably, the fixing device can comprise a first fixing means comprising a first fixing groove and second fixing means comprising a second fixing groove, in particular u-shaped profiles, wherein the first and second fixing grooves are faxing into opposite directions. 
     The invention also relates to a combination comprising at least one module as described above as well as at least one fixing device as described above, wherein the means for fixing of at least one module is in clamp connection with the fixing device. The clamp connection allows for a reliable and easy connection between the module and the fixing device without additional fixing means and can, at the same time, be configured such that the connection is releasable in case, for example, a broken module needs to be exchanged. 
     Advantageously the clamp connection extends essentially over the entire length of the means for fixing. Thus, forces, which are transferred via the connection, are distributed over a large surface and thus high stress levels on the panel can be prevented. 
     The invention also relates to a method for mounting a module as described above on a fixing device as described above and which comprises the steps of: providing the fixing device, providing the module and mechanically engaging the means for fixing the module with the fixing device using a clamp-connection. This method is easy to carry out, as no further tools are mandatory. 
     Preferably the means for fixing can comprise a first means having a first groove, in particular an u-shaped profile and a second means having a second groove, in particular an u-shaped profile, wherein the first and second groove face in opposite directions and the fixing device comprises a first fixing means comprising a first fixing groove and second fixing means comprising a second fixing groove, in particular u-shaped profiles, wherein the first and second fixing grooves are facing into opposite directions, wherein the last step comprises: introducing a lower leg of the second means into the first fixing groove, then introducing a lower leg of the first means into the second fixing groove, in particular by sliding, while the lower leg of the second means remains in the first fixing groove. 
     Advantageously the method can further comprise a step of snapping a projection on the lower leg of the first means into a corresponding recess in the first fixing means. 
    
    
     
       Advantageous embodiments of the invention will be described in detail in combination with the enclosed Figures: 
         FIG. 1  illustrates a three dimensional view of a module for converting solar radiation into electricity according to a first embodiment of the invention, 
         FIG. 2   a  illustrates the module for converting solar radiation according to the first embodiment attached to a fixing device thereby forming a second embodiment, 
         FIG. 2   b  is a partial side cut view of the module attached to the fixing device, 
         FIG. 3   a  illustrates a partial side cut view of a third embodiment of the invention, 
         FIG. 3   b  illustrates the third embodiment in a mounted state, 
         FIG. 4   a  illustrate a partial side cut view of a fourth embodiment of the invention at a first mounting step, 
         FIG. 4   b  illustrates the fourth embodiment during a second mounting step, and 
         FIG. 4   c  illustrates the fourth embodiment in a mounted state, and 
         FIG. 5  illustrates a sixth embodiment of the invention. 
         FIGS. 6   a - 6   d  illustrate an eighth embodiment of the invention. 
     
    
    
       FIG. 1  illustrates a module  1  for converting solar radiation into electricity according to the invention. The module  1  comprises a panel  3  with a front main side  5  and a back main side  7 . The panel  3  itself is a laminate comprising a front layer  9 , an active layer  11  comprising solar energy converting means and a back layer  13 . In this embodiment both the front layer  9  and the back layer  13  are out of glass. The active layer in this embodiment is a thin layer deposited on the front glass layer  9 . The backside layer  13  is attached to the active layer  11  via an adhesive layer. The invention is nevertheless not limited to thin film solar modules. Furthermore, a means  15  for fixing the module  1  to an object (not shown) is attached to the backside  7  of panel  3 . 
     The panel  3  in this embodiment is rectangular, however, other forms or even curved surfaces are possible. Panel  3  represents a standard panel with a surface area of 1100 mm*1300 mm. 
     In this embodiment, the means  15  for fixing the module  1  is glued to the back main side  7  of panel  3 . Gluing ensures a simple but reliable connection with the backside of the panel  3  and its implementation into a fabrication process is easily achieved. 
     The means  15  for fixing the module of this embodiment is an oblong metal profile in a u-shape. Instead of the u-shape, other suitable profile shapes could be used, like for example a z-shape etc. . . . The legs of the u-shaped profile here have the same length, which is, however, not mandatory.  FIG. 1  illustrates the presence of only one metal profile made out of one piece. The invention is, however, not limited to providing only one profile  15  on the back main side of panel  3  but, depending on the requirements concerning mechanic stability, two or more profiles could be provided on the backside  7  of the panel  3  which are arranged in parallel or not. Furthermore  FIG. 1  shows a profile made out of one piece, instead the means  15  for fixing could also be made out of a plurality of shorter profiles arranged in line, to allow for example air or water to pass through. Alternatively clearances might be provided in the profile to achieve the same effect. 
     The metal profile  15  is preferably arranged essentially parallel to one of the edges  17   a - 17   d  of the panel  3 , here along the longer side A (edge  17   b ,  17   d ). It could of course also be arranged in parallel with respect to the short side B (edge,  17   a ,  17   c ) of the panel  3 . Other geometries are also possible without delimiting the application, like for example slanted with respect to the edges  17   a - 17   d.    
     According to the invention, the means for fixing the module  15  is attached to the backside  7  of the panel  3  such that it is arranged away from the edges  17   a - 17   d  by a clearance d. Preferably, the clearance “d” with respect to each one of the edges  17   a - 17   d  of the panel  3  is at least 1 cm. 
     Preferably, the means  15  for fixing the module extends over at least 20% up to about 95% of either length “A” or width “B” of the panel  3  depending on whether the profile is arranged in parallel to the length “A” or in parallel to the length “B”. 
       FIG. 2A  illustrate module  1  mounted on a fixing device  21  which in turn could be attached to a roof or a wall of an object, for example of a house or building, or directly attached to a free-standing frame not shown in  FIG. 2A . The fixing device comprises a set of profiles  21   a  and  21   b , which are essentially arranged in parallel and form a supporting area for module  1 . 
       FIG. 2B  is a partial side-cut view of  FIG. 2A  illustrating how the mounting to the fixing device  21  is achieved with a means for fixing  15  according to the invention. The module  1  is actually held in place by inserting, at least partially, the profile  21   a  of the fixing device  21  into recess  23  of the u-shaped profile of the means for fixing  15  which forms a groove. 
     According to one variant of the embodiment, the cross section of profile  21   a  could be chosen such that the frictional forces between the profile  21   a  and the means for fixing  15  is sufficient to prevent an unintentional relative movement of the panel  3 , thereby achieving a clamp connection. According to another variant the contact surface between the profile  21   a  and the means for fixing  15  can be chosen such that a movement perpendicular to drawing plane is still possible which would facilitate the alignment of the panel  3  with respect to additional panels already in place. 
     The combination out of module  1  and fixing device  21  form a second embodiment according to the invention. 
     To prevent a relative movement between module  1  and the fixing device  21 , further securing means, like bolts or any other locking means, can be provided in addition. 
     With a module  1  according to the invention, the following advantages can be achieved with respect to prior art modules like described above. 
     Due to the fact that the means  15  for fixing the module are arranged on the backside  7  only of the panel  3  and furthermore spaced apart from the edges  17   a - 17   d  of the panel  3 , dirt, snow, etc. which might accumulate in the transitional region between the panel and the means for fixing cannot reach the edge region  17   a - 17   d  of the panel which represents the weakest points of such a laminate. Thus, water or other harmful elements, which might enter at the interfaces of the panel  3  and deteriorate or destroy the solar radiation converting means by corrosion is prevented from entering into the laminate. 
     In addition, by providing an oblong profile  15 , a connection with an object can be realized over a large surface such that stress which could for example occur during bad weather conditions with high winds, does not lead to excessive stress peaks at limited locations on the panel, like for example in prior art modules using clamps at the edge to mount. Thus the static requirements can be released such that thinner front and/or back layers can be used in the modules, which render the modules cheaper and their weight becomes reduced. Thus, according to a variant of the embodiment of the invention, glass layers with less than 5 mm, in particular less than 3.5 mm, more in particular of 3.2 mm or 3 mm of normal float glass are used. 
     Finally, by arranging the means for fixing  15  on the backside only, no particular measures need to be taken to electrically isolate the means for fixing  15  from the edge region  17   a  to  17   d , which is mandatory in the known fixing methods using clamps which have to be arranged on the edge of a module. 
       FIGS. 3   a  and  3   b  illustrate a third embodiment according to the invention. Features with reference numerals already used for the description of the first embodiment will not be explained in detail again, but their description is incorporated herewith by reference. 
     The left hand side of  FIG. 3   a  represents a partial cross cut view of a panel  31  with a second kind of means for fixing  33  the module which is attached, e.g. by gluing to a panel  3 , comparable to the illustration of  FIG. 2   a . The difference between the means for fixing  33  and the means for fixing  15  of the first embodiment is that the lower leg  35  of the u-shaped profile is flexible as indicated by the arrows and forms a tongue with a projection  37  towards the free extremity  41  of the lower leg  35 . The projection  37  in this embodiment is directed towards the first leg  39  of the profile. 
     The projection  37  can be present over the entire length of the lower leg  35  in the direction perpendicular to the drawing plane, or could only be present at one or more locations along the lower leg  37 . Furthermore,  FIG. 3   a  shows the projection  37  at the extremity  41 , however, the projection  37  could also be arranged with a certain distance with respect to the extremity  41 . In addition, the lower leg  35  can be longer or shorter compared to the upper leg  39 . The projection  37  and the profile of the means for fixing  33  here are made out of the same work piece. Nevertheless projection  37  could also be a separate piece out of a different material and attached to the lower leg  35 . 
     The right hand side of  FIG. 3   a  illustrates the cross section of a profile  43  of a fixing device, like illustrated in  FIG. 2   a , which has the same properties as profile  21   a ,  21   b  with the difference being that profile  43  has a recess portion  45  the shape of which is adapted to receive at least partially, preferably completely, the projection  37  of the fixing means  33 . The recess portion  45  can be arranged over the entire length of the profile thus forming a groove. 
     Furthermore the profile  43  has beveled portions  47  and  49  on the side of the profile, which will enter recess  51  of the u-shaped profile  33 . 
     The projection  37  and the recess portion  45  are arranged such that when the module  1  is mounted onto the fixing device, a snap-in connection between the means for fixing  33  and the profile  43  of the fixing device can be achieved. This situation is illustrated in  FIG. 3   b.    
     The beveled portions  47  and  49  serve to facilitate the bending of the lower leg  35 , such that when approaching the module  1  and the fixing device with respect to each other, the projection  37  can be moved out of the way of the profile  43 , such that the desired clamp- and snap-in connection between the two is achieved. 
     In this way a connection between the two elements is achieved that securely locks the module  1  in place, but that can still be released if necessary, by bending down the lower leg  35 . To prevent an accidental releasing of the connection additional fixing or securing means like mentioned with the first embodiment can be used. To prevent theft, according to a variant of this embodiment, the recess  45  can have an undercut region and the projection  37  a hook like form. In this case it is more difficult to release the connection. 
     With the module according to the third embodiment and the fixing device and their combination the same advantageous effects like for the first and second embodiment can be achieved. 
       FIGS. 4   a  to  4   c  illustrate a cross cut view of a fourth embodiment of the invention. Again features with reference numerals already used for the description of the first to third embodiment will not be explained in detail again, but their description is incorporated herewith by reference. The solar module  51  comprises a panel  3  and attached to its backside  7  two u-shaped profiles  53  and  55  playing the role of the means for fixing which are arranged in parallel. The left profile  53  has the shape of the means for fixing  33  of the second embodiment with a projection  57  at the lower leg and directed towards the upper leg. The right profile  55  has the shape of the means for fixing  15  of the first embodiment. Furthermore the base  59  and the base  61  of the u-shaped profiles  53  and  55  are facing each other such that the recesses  63  and  65  are facing in opposite directions and do not face each other—the openings thus face outwardly. 
     With this structure a simple but safe mounting to a frame of fixing device  71  comprising a first and second fixing profile  73  and  75 . Like profiles  53  and  55 , also the fixing profiles  73  and  75  are u-shaped and profile  73  furthermore comprises a recess portion  77  at the upper leg  79 , which is adapted to the projection  57  of profile  53 . Unlike profiles  53  and  55 , the fixing profiles  73  and  75  of the fixing device  71  have their recesses  81  and  83  facing each other—thus the openings face inwardly. 
     To fix the module  51  to fixing profiles  73  and  75  of the fixing device  71 , first of all the lower leg  85  of the right u-profile  55  is introduced into recess  83  of the fixing profile  75 . To facilitate the introduction of the lower leg  85  the widths a, a′ of the base  61  and base  87  of the fixing profile  75  inside the recesses  65  and  83  is larger than the one of the lower legs  75  and  85  such that the introduction can be achieved under an angle α (see  FIG. 4   a ). 
     Then module  51  is angled down and the lower leg  87  of profile  53  comes to a rest on the lower leg  89  of the left fixing profile  73 . This is achieved, as in this embodiment the lower leg  89  of the fixing profile  73  is longer than the upper leg  91 . Furthermore the distance between the profiles  53  and  55  on the one hand and the fixing profiles  73  and  75  is such, that the lower leg  85  of the right profile  55  is still positioned in the recess  83  of the fixing profile  75 , like shown in  FIG. 4   b . Now, a sliding of module  51  on the upper surfaces of the lower legs  89  and  75  is still possible. A movement perpendicular to the drawing plane would allow to align the module  51  with respect to other modules already mounted (see  FIG. 2   a ) and a movement in the plane, supported by the gravitational force, will allow the fixing of the module  51  by clicking of the projection  57  into recess  77  to prevent a further movement in this direction. This situation is illustrated in  FIG. 4   c . The connection between the left fixing profile  73  and the left profile  53  is preferably based on frictional forces between the legs of the u-shaped profiles and mechanical forces due to snapping-in. On the right hand side the lower leg  85  of profile  55  is still positioned in the recess  83  of the right fixing profile  75 . This prevents a tilting of panel  3 . 
     Of course the position of profiles  53  and  55 , as well as the position of the fixing profiles  73  and  75  can be exchanged. In this case, one would have to move the panel  51  against gravitational forces to bring let it snap into recess  77 . 
     Module  51  and fixing device  71  form the fifth embodiment of the invention. The fourth and fifth embodiment share all the advantages as previously described with respect to embodiments 1 to 3. It is furthermore important to mention that the advantages of the clamp connection and or the click-in (snap-in) connection can also be achieved with modules in which the means for fixing extends over the backside without clearance to the edge. Nevertheless in this case the problem of dirt accumulation remains. 
       FIG. 5  illustrates a module  101  according to a sixth embodiment of the invention. The only difference with respect to the module  51  of the fourth embodiment is that the position of the profiles  51  and  53  are inverted. Now the recesses (grooves)  65  and  63  are facing each other, but are still facing in opposite directions (as indicated by arrows). Accordingly also the fixing device  103  comprises the fixing profiles  73  and  75  as illustrated in  FIGS. 4   a  and  4   c , however also with inverted positions. The distance between the two fixing profiles  73  and  75  is also reduced to take into account the change of the direction of the openings of the recesses  65  and  63 . 
     The combination of module  101  and fixing device  103  form a seventh embodiment. 
       FIG. 6   a  illustrates a schematic 3-dimensional view of the backside of a solar module  201  according to the eighth embodiment of the invention. Again, features with reference numerals already used for the description of the first to seventh embodiments will not be explained in detail again, but their description is incorporated herewith by reference. 
     The solar module  201  comprises a panel  3  and attached to its backside  7 , two bar-shaped elements  203 ,  205  playing the role of the means for fixing according to the invention. The two bar-shaped elements  203 ,  205  are preferably arranged in parallel. In the upper left and right edge regions of the panel  3 , electric connectors  207 ,  209  are furthermore provided. The two extremities  203   a ,  203   b  and  205   a ,  205   b  of each of the bar-shaped elements  203 ,  205  respectively have a protruding portion such that a clearance  203   c ,  203   d  and  205   c ,  205   d  is formed with respect to the edges  17   d ,  17   b  of the panel  3  between the tongues and the backside  7  of the panel  3 . Preferably, the extremities  203   a ,  203   b ,  205   a ,  205   b  of the tongues are flush aligned with edges  17   d ,  17   b  of the panel  3 . 
     The invention is not limited to the presence of two bar-shaped elements  203 ,  205  as means for fixing. More than two bar-shaped elements can also be provided or only one, preferably centrally arranged, bar-shaped element can be sufficient to ensure a proper attachment of the module  201  on a fixing device. In the case of a single bar-shaped element, the lateral extension of the bar is preferably larger compared to the embodiment illustrated in  FIG. 6   a.    
     Thus, as in the fourth embodiment, the clearances  203   c ,  203   d  of bar-shaped element  203 , just like the clearances  205   a ,  205   b  of the bar-shaped element  205 , are facing in opposite directions, namely facing outwardly towards the edges  17   b  and  17   d  of the panel  3 . The difference with respect to the fourth embodiment is that the bar-shaped elements  203 ,  205  extend from one side  17   b  to the other side  17   d  where attachment with respect to a fixing device (see further below) will occur. Thus they are turned by 90° compared to the arrangement of u-shaped profiles  53 ,  55  of the fourth embodiment (see  FIG. 4   a ). 
     According to a variant, at least one tongue at the extremities  203   a ,  203   b  and  205   a ,  205   b  of the bar-shaped elements  203 ,  205  could also be equipped with a projection similar to projection  57  illustrated in  FIGS. 4   a - 4   c.    
     With the structure illustrated in  FIG. 6 , as with the one of embodiment 4, a simple but safe mount to a frame of a fixing device  211  comprising first and second fixing profiles  213 ,  215  can be achieved. 
     Whereas, for the eighth embodiment, the same fixing profile  73 ,  75 , as illustrated in the fourth embodiment ( FIGS. 4   a - 4   c ), could be used to fix the module  201 , the fixing device  211  illustrated in  FIG. 6   b  is configured to not only receive one module  201 , which can be introduced into a first recess  217  of fixing profile  215 , but also comprises a second recess portion  219  for receiving a second module  220  next to module  201 . The second fixing profile  213  has the same structure with a first recess  221  (for receiving a third module) corresponding to recess  217  and a second recess  223  (for receiving module  201 ) comparable to recess  219 . As illustrated in  FIG. 6   b , the lower legs  225 ,  227  of the fixing profile  213  have, in this cross-sectional view, preferably the same length (L 1 ) and serve as a supporting surface whereas the length (L 2 ) of the upper leg  229  of the second recess  223  is shorter than the one of the upper leg  231  (L 3 ) of the first recess  221 . In this embodiment, L 1 , L 2  and L 3  satisfy the following: L 2 &lt;L 3 &lt;L 1 . 
     According to a variant, and as in the embodiment illustrated in  FIGS. 4   a - 4   c , the fixing profile  213 ,  215  may comprise recess portions comparable to recess portion  77  at the upper leg  79  of the fixing profile illustrated in the fourth embodiment. 
     To fix module  201  to fixing profiles  213 ,  215  of the fixing device  211 , first of all, the upper tongue  203   b  of the bar-shaped element  203  is introduced into recess  217  of fixing profile  215 . Due to the fact that the lower leg  225  is longer than the upper leg  231  (see also description of the fixing profile  213  above), the alignment and the introduction of tongue  203   b  with respect to recess  217  is facilitated. The introduction of tongue  203   b  into recess  217  could, according to a variant, be further facilitated by a flexible arrangement of the upper leg  231  with respect to the support surface forming lower leg  225 . In addition, as in the fourth embodiment, the width w 1  of the clearance is larger than the width w 2  of the recess  217  in the fixing profile  215 . 
     As illustrated in  FIG. 6   c , the module  201  is then angled down and the left tongue  203   a  of the bar-shaped element  203  comes to a rest on the supporting lower leg  227  of lower fixing profile  213 . This is made possible due to the fact that the supporting lower leg  227  is longer than the upper leg  229 . The upper tongue  203   b  is now, preferably completely, introduced into recess  217  of the upper fixing profile  215 . 
     A sliding of module  201  on the upper surfaces of the supporting legs  227  of the first and second fixing profiles  213 ,  215  leads to the introduction of the lower tongue  203   a  into recess  223  of the lower fixing profile  213 , as illustrated in  FIG. 6   d . At the same time, the upper tongue  203   b  is still positioned inside recess  217  of the upper profile  215 , as in the embodiment shown in  FIGS. 4   a - 4   c . Module  201  is now fixed in the fixing device  211 . 
     According to variants, as already described above, the clamp connection between the module  201  and the fixing device  211  could be enhanced by the snapping-in of projections into corresponding recesses and/or a fixing by e.g. nuts and bolts. As illustrated in  FIG. 6   d , after having positioned module  201 , a similar module  301  can be placed on the supporting surface of lower leg  225  of the lower fixing profile  213 , illustrating the advantage of this embodiment, namely that two modules can come to a rest on one fixing device. 
     The combination of module  201  and fixing device  211  form a ninth embodiment according to the invention. 
     The features of the various embodiments 1 to 9 can be freely combined to achieve further advantageous variants according to the invention.