Abstract:
The modular unit for generating solar power comprises a plurality of diamond-shaped cover plates ( 3.2, . . . , 3.3 ) for forming a surface trapping sunlight. The cover plates ( 3.2, 3.3 ) contain photovoltaic elements ( 106.1, 106.2, 106.3 ). The system further comprises a plurality of support rods ( 54 ) having a number of pre-manufactured fastening positions ( 55 ), said rods being arranged at a predetermined angle&gt;0° to the horizontal and extending in the direction of a line of slope. Every fastening position is associated with a fastening device ( 50 ) which connects two corners of the overlapping cover plates ( 3.2,3.3 ) to the support rod ( 54 ) in the fastening position. The cover plates ( 3.2, 3.3 ) are arranged diagonally and so as to overlap in a scale-type fashion with respect to a longitudinal direction of the support rod ( 54 ) in such a manner that the surface trapping the sunlight is at the same time rain water-repellent. The cover plates ( 3.2, 3.3 ) have a first cut-out section ( 15.3 ) in a first corner section and a second cut-out section ( 20.2 ) in a diagonally opposite second corner section, in which second cut-out section one of the fastening devices ( 50 ) engages. The fastening device ( 50 ) holds the first corner section of the first cover plate ( 3.3 ) in a first supported position at a first distance to the support rod ( 54 ) and the second corner section of the second cover plate ( 3.2 ) in a second supported position at a second distance to the support rod ( 54 ), the first corner section of the first cover plate ( 3.3 ) being interspaced from the second corner section of the second cover plate ( 3.2 ) by at least one cover plate thickness.

Description:
TECHNICAL DOMAIN 
       [0001]    The invention relates to a device for generating solar power comprising at least four diamond-shaped cover plates for forming a surface which captures sunlight, photovoltaic elements being contained in the cover plates, and at least one fastening device which connects the cover plates assigned to the fastening site to a support bar at this fastening site. Furthermore the invention relates to a component system for preparing this device. 
       PRIOR ART 
       [0002]    The use of the solar radiation which is incident daily on rooves and facades of inhabited or uninhabited buildings to obtain energy in the form of electrical current and heat has already acquired great importance. 
         [0003]    Photovoltaic modules are being increasingly mounted on rooves nowadays. With respect to minimizing costs, there is interest in being able to integrate the photovoltaic modules in the outer building skin (roof, facade) which is used as weather protection. This means that the structure which holds the photovoltaic modules performs two functions. 
         [0004]    The photovoltaic modules or roof elements themselves consist essentially of thin, flat, brittle silicon solar cells (in strip or disk form) which are embedded in an elastic transparent material, generally EVA (ethyl vinyl acetate), between a transparent front plate of tempered glass or plastic and a back film or another glass plate for protection against mechanical and chemical damage. The solar cells are electrically connected to one another so that the generated module voltage can be tapped via a terminal outlet which is generally located on the back. A host of these modules or roof elements are further connected in series and in parallel in order to obtain the respectively desired system voltage or direct current power. Generally the current is fed into the public grid via a rectifier or for small island installations is interim-stored in batteries. 
         [0005]    DE 100 46 134 discloses solar tiles for preparing a weather-proof solar roof. The tiles consist for example of an essentially diamond-shaped carrier plate with a somewhat smaller square solar cell which is located flush in the (lower) corner of the carrier plate so that the carrier plate projects on two sides or there is a region free of solar cells. The tiles are fastened with the side or corner at the top to horizontally running mounting rails. The mounting rail has an essentially U-shaped cross section with a profile section which projects toward the top in the manner of a nose on the open side. The tile on the upper end has a through hole through which a pin is guided which can be suspended on the mounting profile. On the mounting rail there is a sealing lip which covers the gap between the mounting rail and the tile. 
         [0006]    International application PCT/CH2008/000032 discloses a weatherproof building jacket, especially a pitched roof, with several square weatherproof plates which are laid with respect to the line of slope in a diagonal position with scale-like mutual overlapping. The plates are connected to a support structure on a corner region which lies underneath with respect to the line of slope, for the indicated corner region of the plate there being one sealing element at a time which closes a gap between plates which are arranged transversely to the main direction at the same height. Here the rectangular plates in two opposite corner regions each have one through opening for a fastener so that the plates are connected to the support structure on their corner regions which lie top and bottom in the main direction. 
         [0007]    The economic success of an outer building skin depends on its being able to be quickly and easily prepared and nevertheless its having the required weatherproof qualities. Last, but not least, the aesthetics should not suffer under the technical requirements. 
       DESCRIPTION OF THE INVENTION 
       [0008]    The object of the invention is to devise a device which belongs to the initially mentioned technical domain for generating solar power and which is aesthetically pleasing and can be easily and quickly prepared on site. In particular it should also be possible to replace defective cover plates without a larger number of adjacent cover plates having to be removed. 
         [0009]    This object is defined by the features of claim  1 . According to the invention, the device encompasses several, specifically at least four, preferably diamond-shaped cover plates, at least one (but typically several) support bars and at least one (but typically at least one per cover plate) fastening device. The cover plates in concert form a surface which captures sunlight with photovoltaic elements (solar cells) which are arranged (sealed) in the cover plates. The cover plates as claimed in the invention are laid in a position superimposed in the manner of scales, especially in a diagonal position with respect to the line of slope of the indicated surface. The incline of the support bars on which the cover plates are held will be in a direction which deviates from the horizontal alignment (=angle 0°) and will be so great that the tilt of the individual cover plate (whose tilt is of course smaller as a result of the scale-like arrangement) is enough for rain water to run off reliably along the line of slope. One example is an angle of at least 3°. 
         [0010]    The support bars have several, specifically at least three prefabricated fastening sites. The fastening sites (which can be for example threaded holes or simple drill holes) are therefore not made on site, but in the production of the support bars. The fastening sites therefore have CNC-produced precision. While holes made on site generally have a position tolerance in the millimeter range, the CNC tolerance is easily less than 1/10 mm (generally 1/100 mm or better). 
         [0011]    The cover plates are held with fastening devices on the support bars. There is at least one fastening device as claimed in the invention. It is attached at one of the fastening sites. Fundamentally there is one fastening device per cover plate, on the fastening device two cover plates being supported preferably with the first and second corner region so that the cover plates with respect to the lengthwise direction of the support bars are preferably arranged diagonally overlapping one another in the manner of scales and in this way at the same time make the sunlight-capturing surface rain water-repellant. In the preferred first or second corner region each cover plate has a first and a second recess into which the fastening devices fit. 
         [0012]    The fastening device is made such that it preferably keeps the first corner region of the first cover plate in a first support position at a first distance to the support bar and preferably the second corner region of the second cover plate in a second support position at a second distance to the support rod. Here the preferred first corner region of the first cover plate (viewed perpendicular to the support bar) is spaced away from the preferred second corner region of the second cover plate by at least the thickness of the cover plate. 
         [0013]    The diagonal position is an especially preferred embodiment of the invention. The retaining and sealing system as claimed in the invention can however also be used for “straight” (i.e. non-diagonally) laid rectangular plates. For “straight” installation the, for example, rectangular plates have an edge side which runs transversely to the line of slope and one edge side which runs parallel to the line of slope, as is apparent, for example, from  FIG. 1  of DE 100 46 134 (Arnold Glaswerke). For straight installation the recesses need not necessarily be arranged in the corner regions of the plates. They can be placed in the middle of one edge side. 
         [0014]    Since the fastening sites are prepared mechanically and with high precision, mounting is much simpler and faster than if holes must be prepared on site. Matching between the support bar and cover plates is also free of error. Only one cover plate is ever attached on one support bar, there is no “bridging” between adjacent support bars. Accordingly the system as claimed in the invention is also less sensitive to imperfect positioning of the support bars relative to one another. 
         [0015]    Since each cover plate is connected on its two diagonally opposite corners to the support bar, the device is also protected against wind gusts which could otherwise lift the cover plates. 
         [0016]    In one system as claimed in the invention, it is possible to replace an individual cover plate in the middle in a larger surface by the two fastening devices which are assigned to the cover plate being (at least) partially detached. 
         [0017]    Preferably the support bars consist of steel. They are made for example as a rectangular section or U-section so that they can be mounted on an underroof structure (which has laths which run parallel to the ridge). The sections can however also have a different shape (T, double-T, angle, etc) and can be fixed on the underroof structure with the corresponding clamps. The prepared fastening sites are for example threaded holes with a standard thread into which the fastening devices can be screwed. The fastening sites can also be welded pins or suitable shaped clips. A fastening site as claimed in the invention is characterized in that it stipulates an unequivocal position so that when the device is mounted on site it is not necessary to measure where the fastening device must be attached. 
         [0018]    For reasons of economy it is advantageous if the device is made available as a complete system. This means that the support bars are made available with a length in which the roof or wall surface of the building is to be covered by the device as claimed in the invention. For example the support bars have a length which extends from the lower (horizontal) edge of the roof to the ridge of the roof. In general (when the device is in some position) the length of the support bars corresponds essentially to an extension of the surface in the direction of the line of slope. The cover plates are then attached only on the support bars and the connection to the building-side support structure takes place solely via the support bars. 
         [0019]    Generally the surface which is covered with the device as claimed in the invention is rectangular and the support bars extend parallel to one another from one edge of the surface to the other. For large surfaces it is advantageous if the device is prepared from its individual parts on site. But it is also conceivable for the support bars to be connected among one another (for example by a frame) and for industrially prefabricated facade modules (with a plurality of cover plates) to be transported to the application site and to be mounted more or less in a component construction. In general however, with the component construction with respect to aesthetics less good designs can be implemented than with mounting on site. Specifically it is desirable for the device as claimed in the invention to appear to the observer as an integrated part of the building and not as an added separate part. Therefore it is preferred that for example an entire roof surface be built according to the principle as claimed in the invention. In this sense individual cover plates can also be made solely of glass and without photovoltaics so that a window is formed for passage of light. 
         [0020]    The underroof construction on which a device as claimed in the invention is mounted generally does not have weather protection, but only the thermal insulation and a vapor barrier. The object of the invention includes devising an economical building jacket with integrated photovoltaics. For this purpose it is necessary for the device to create sufficient weather protection (against rain and wind). 
         [0021]    Preferably there is a plate-shaped sealing element for sealing against wind gusts. It is positioned at the fastening site with the fastening element where the second corner region of the second cover plate overlaps the first corner region of the first cover plate in the manner of scales. The sealing element is located between the two indicated corner regions and has a thickness which corresponds at least to the thickness of the cover plates. The sealing element closes a gap which is present between the neither overlapping nor touching cover plates which are placed laterally to the fastening site. 
         [0022]    It is also possible to provide a sealing lip on the bottom of the cover plates instead of the plate-shaped sealing element. The sealing element need not be plate-shaped, but can also have the shape of an elongated flexible profile. 
         [0023]    Preferably the sealing element has two flexible elements which is pressed [sic] again one edge of a third and a fourth of the four cover plates. The third and fourth cover plate are those cover plates which are offset with respect to the line of slope relative to the first and second cover plate and are arranged at the same height to one another. The flexible elements have for example the shape of arms or finger-like extensions. They adjoin the edge of the cover plates which points down in the direction of the line of slope. 
         [0024]    Preferably the sealing element has a circular arc-shaped sealing lip which extends from a sealing lip which is attached to a third cover plate as far as to a sealing lip which is attached to the fourth cover plate. The third and fourth cover plate are located offset at the same height relative to the line of slope and opposite the first and second cover plate in the direction of the line of slope. In this way the tightness in the overlapping region of the cover plates can be additionally increased. The total of the thicknesses of the sealing element and of the circular arc-shaped sealing lip corresponds essentially to the total of the thicknesses of a cover plate with the sealing lip attached to it. 
         [0025]    The cover plates have a conventional multilayer structure. The top which is used for weather protection is preferably a glass plate. Behind it are the solar cells which are potted in an elastic layer or are cemented to the glass plate. The bottom of the cover plate can be another glass plate (so that a so-called sandwich structure arises) or other opaque plate. Instead of glass plates there can also be transparent plastic plates. On the back of the cover plate there are also electrical terminals which are formed essentially by two cable pieces with electrical connectors. The length of the cable pieces is chosen such that cover plates laid adjacently can be connected to one another and can also be removed as selectively as possible from the arrangement if a defect occurs. 
         [0026]    The solar cells toward the edge of the cover plate have a certain distance which corresponds to the scale-like overlapping. The distance is for example 1-3 cm. Furthermore, in one corner region there is a rectangular (especially square) region which is free of solar cells. The region which is free of solar cells has roughly the size of one solar cell. One advantageous arrangement arises when using n 2 −1 solar cells. 
         [0027]    The region which is free of solar cells after mounting of the cover plate is located under the corner of the cover plate which is located farther above. 
         [0028]    The recess in the first corner region of the cover plate is larger than the one in the second. Thus it is possible to equip the fastening device with a wider lower and a narrower upper part so that the cover plates with the recess can be turned over the fastening device and can be kept at a different height. 
         [0029]    But it is also possible to make the two recesses of the same size and to keep them at the correct height using aids which belong to the fastening device. 
         [0030]    The fastening device preferably has a tubular support part and a tension device which is placed in a tubular support part. The support part bears the overlapping corners of the cover plates at a mutual distance and in predefined support positions by way of the support bar. The support part has a first stop for making available a first support position for a first corner region of the first cover plate. The first support position is at a given distance to the support bar so that the cover plate does not rest directly on the support bar. Furthermore, on the support part there is a second stop for making available a second support position for the second cover plate at a second distance to the support bar. The second stop can be formed by the top end of the support part. In this way the upper cover plate can move freely relative to the support part. The first corner region of the first cover plate is spaced by at least one thickness of a cover plate away from the second corner region of the second cover plate. 
         [0031]    The tension device fixes the upper corners of the two cover plates, which corners lie on top of one another, relative to the support bar. Preferably the upper corner is pressed by the tension device onto the support part without resulting in rigid fixing. In a certain sense there is floating support (within certain boundaries). The tension device is implemented for example by a two-part pin and a cap. One (lower) end of the pin is fastened to the support bar and the other (upper) end bears the cap. The tubular support part can be moved to a certain extent. The second cover plate is also held, not rigidly, but slightly flexibly. The cover plates can thus be adjusted relative to the support bars. The different thermal expansion of the plate and bar is prevented from having an adverse effect. 
         [0032]    The cap has a greater transverse elongation than the pin. The pin can be easily guided through the through opening in the cover plate, while the cap is designed to completely cover the passage opening. Preferably the transverse elongation of the cap on the lower (i.e. facing the cover plate) side corresponds to the transverse elongation of the support part. The upper cover plate is then held between two annular contact surfaces of roughly the same size. But it is also possible to make the cap larger or smaller than the transverse dimension of the support part. 
         [0033]    Advantageously the pin is essentially two-part. The first part is dimensioned such that in the mounted state it does not project over the tubular support part. The second part is seated on the first part, i.e. can be detachably coupled to the first and constitutes the part of the pin which projects beyond the tubular support part. The second part is routed through the recess in the second corner region of the second cover plate. 
         [0034]    The cap preferably has a through opening for a tensioning screw which can be screwed into a thread on the top end of the pin. 
         [0035]    The two parts of the pin make it possible to remove individual cover plates from the overall combination with minimum effort and to replace them. Of the two fastening devices which hold the cover plate, one must be completely dismounted and the other half-dismounted. 
         [0036]    The division of the pin can of course be different. A one-piece pin also lies within the framework of the invention. 
         [0037]    The first support position can be formed by the fastening device with one shoulder which is made outside on the tubular support part and the second support position by the top end of the support part. The tubular support part therefore forms a type of hollow peg which can be inserted into the first recess of the first (i.e. lower) cover plate. 
         [0038]    The support part can also be made such that it can be inserted both through the lower and also through the upper cover plate. In this case it tapers from bottom to top and is preferably staggered so that two defined shoulders are made available as support positions for the cover plates. Instead of a support part supported on the support bar there can also be support parts which are supported only on the pin. It is then however not possible to remove the pin without the support parts and the pertinent cover plates. 
         [0039]    On at least one edge of the cover plates there can be a sealing lip on the top. It seals the gap which would otherwise exist between the cover plates which overlap in the manner of scales. Preferably the sealing lips are on the two abutting sides of the cover plates, i.e. on those edges which lie under the next higher cover plates which overlap them. 
         [0040]    The sealing lips can be cemented on beforehand (i.e. industrially) or for example clipped on on site. But the sealing lips are not critical. 
         [0041]    The invention is also embodied in a system of components for preparing a device for recovering solar power. This system of components consists of the following parts: 
         [0042]    a) a preferably diamond-shaped cover plate which contains photovoltaic cells, 
         [0043]    b) a support bar with at least three prefabricated fastening sites, 
         [0044]    c) a fastening device for connecting the cover plate at this fastening site of the support bar. 
         [0045]    These parts are available in any number so that the desired roof or facade part can be prepared. Special parts are not mentioned here; they are required for edge termination between the photovoltaic cover plates and the remaining vicinity to complete weather protection. The technical execution of the aforementioned system components is as follows: 
         [0046]    d) The cover plate preferably has a first recess in the first corner region and a second recess preferably in a diagonally opposite second corner region. They are ultimately the locations on which the cover plate is held (preferably exclusively). 
         [0047]    e) The fastening device and the two recesses of a cover plate are matched to one another such that the fastening device can engage the recess. This has the advantage that during installation first the fastening device can be fixed at the fastening site of the support bar and afterwards the cover plates can be placed on the fastening device. 
         [0048]    f) The distances of the fastening sites correspond to the distance of the recesses of one cover plate. The cover plates are therefore laid and held diagonally with respect to the longitudinal direction of the support bars. 
         [0049]    g) The fastening device is designed to hold preferably the first corner region of the cover plate in a first support position at a first distance to the support bar and preferably the second corner region of the cover plate in the second support position at a second distance to the support bar, the preferred first corner region of the first cover plate being spaced by at least one thickness of the cover plate away from the preferred second corner region of the second cover plate. 
         [0050]    This system of components can preferably be equipped with the optional features which were explained above. 
         [0051]    To prepare a device as claimed in the invention the procedure is as follows: 
         [0052]    Several support bars are fixed on the prepared substructure (for example a roof truss). They should have a given tilt angle&gt;0° to the horizontal and a uniform mutual distance transversely to the line of slope. 
         [0053]    Accordingly the fastening devices (for example their pins) are attached to the prepared fastening sites of the support bars. 
         [0054]    Finally, the tubular support part is located on the pins and the first corner region of a first cover plate is supported on the support part. In this way for example all cover plates which are located at the same height transversely to the line of slope are mounted with their lower (i.e. “second”) corner region and their upper (“first”) corner region. Afterwards a row of cover plates which is to be arranged next higher is installed. 
         [0055]    Preferably, after arranging the first corner region and before clamping the second corner region a sealing element is attached to the fastening device. 
         [0056]    Other advantageous embodiments and combinations of features of the invention will become apparent from the following detailed description and the totality of claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0057]    The drawings are used for explanation of the exemplary embodiment. 
           [0058]      FIG. 1  shows a top view of a weatherproof surface which is prepared with the component system as claimed in the invention, consisting of cover plates with photovoltaic cells; 
           [0059]      FIG. 2  shows a schematic cross section along the line of slope; 
           [0060]      FIG. 3  shows a top view of the overlapping region; 
           [0061]      FIG. 4  shows a fastening device in cross section; 
           [0062]      FIG. 5   a  shows a top view of the cover plate with solar cells; 
           [0063]      FIG. 5   b  shows a sectional view of the cover plate according to  FIG. 5   a;    
           [0064]      FIG. 6  shows a schematic of the system unit  1 ; 
           [0065]      FIG. 7  shows a schematic of the sealing element attached at the top on the cover plate; 
           [0066]      FIG. 8   a  shows the top view of one version of a sealing element; 
           [0067]      FIG. 8   b  shows a sectional view of the sealing element according to  FIG. 8   a;    
           [0068]      FIG. 9   a  shows a detailed view of one end of the sealing element; 
           [0069]      FIG. 9   b  shows a side view of the detailed view according to  FIG. 9   a;    
           [0070]      FIG. 10   a  shows a side view of the sealing element according to  FIG. 8   a;    
           [0071]      FIG. 10   b  shows a detailed view of the end of the sealing element according to  FIG. 10   a; and    
           [0072]      FIG. 11  shows a perspective of the sealing element according to  FIG. 8   a.    
       
    
    
       [0073]    Fundamentally the same parts are provided with the same reference numbers. 
       EMBODIMENTS OF THE INVENTION 
       [0074]      FIG. 1  shows a system unit  1  with a surface  2  which captures sunlight and which is formed by several cover plates as claimed in the invention, hereinafter called plates  3 . 1 ,  3 . 2 ,  3 . 3 ,  3 . 4 ,  3 . 5 ,  4 . 1 ,  4 . 2 ,  5 ,  6 . 1 ,  6 . 2  for short. Not all plates need be provided with solar cells. The system unit  1  forms a weatherproof building enclosure. This building enclosure can be for example a roof (i.e. a tilted surface) or a facade (i.e. a vertical surface) of a building. The surface  2  which captures the sunlight is generally a plane, but with a corresponding configuration of the plates can also be a two- or three-dimensionally curved surface (cylinder envelope surface, spherical cap or other). The length and width of the surface  2  preferably depends on the size of the roof surface. Therefore the entire roof (or an entire roof side) is covered with the described system unit so that aesthetically a uniform picture and technically a closed, weatherproof building enclosure result. 
         [0075]    The surface  2  has a lower edge  9 . 1  which lies transversely with respect to the line of slope A and an edge  9 . 2  which is aligned parallel to the line of slope A. The edges  9 . 1  and  9 . 2  abut at a right angle and form a corner  10  of the surface  2 . The other, only schematically shown edges  9 . 3  and  9 . 4  border the surface to the top and side. 
         [0076]    The individual plates  3 . 1 ,  3 . 2 ,  3 . 3 ,  3 . 4 ,  3 . 5 ,  4 . 1 ,  4 . 2 ,  5 ,  6 . 1 ,  6 . 2  underlie a basic shape  7  which is diamond-shaped with respect to a line of slope A. In particular the basic shape  7  of the individual plates is formed by a square shape which stands on one corner  8  such that a corner  14  opposite this corner  8  likewise lies on the line of slope A. This is called diagonal laying of the plates. Not each plate has the complete basic shape  7 . Depending on its arrangement in the surface  2 , the plates can have different shapes.  FIG. 1  shows plates  3 . 1 , ...,  3 . 5 , edge plates of the line of slope  4 . 1 ,  4 . 2 , transverse edge plates  6 . 1 ,  6 . 2 , and corner plates  5 . The plates  3 . 1 , . . . ,  3 . 5  have a complete basic shape  7 , for example a square shape standing on the corner  8 . 
         [0077]    The plates  4 . 1 ,  4 . 2  are located in the edge area  9 . 2  of the system unit  1 , which area is parallel to the line of slope. The shape of the plates  4 . 1 ,  4 . 2  results from the straight-line division of the square regular basic shape  7  parallel to the line of slope A. The plates  6 . 1 ,  6 . 2  on the lower edge  9 . 1  of the surface  2  have different shapes which arise due to the straight-line division of the square regular basic shape  7 , perpendicular to the line of slope A. In the corner  10  is the corner plate  5 . The shapes of the plates  4 . 1 ,  4 . 2 ,  5 ,  6 . 1 ,  6 . 2  which are located on the edge are such that the surface  2  is altogether rectangular. The upper horizontal edge of the surface is provided for example on the ridge of the roof and the lower edge on the rain gutter. The plate  3 . 2  which is located in the interior of the surface  2  has six adjacent plates at a time (plates  3 . 1 ,  3 . 3 ,  3 . 4 ,  3 . 5  and the edge plates of the line of slope  4 . 1  and  4 . 2 .). The plate arrangement of the system unit  1  is described below using one plate  3 . 2  which has been chosen by way of example. 
         [0078]    The plates  3 . 1  to  3 . 3  are arranged overlapping in the manner of scales in the direction of the line of slope A, the plate  3 . 2  being overlapped by the adjacent upper plate  3 . 1  in a square corner region  11 . 1  and the plate  3 . 3  being overlapped by the plate  3 . 2  in turn in a square corner region  11 . 2 . In  FIG. 1  the corner regions  11 . 1 ,  11 . 2  occupy only a small part of the entire surface of the plate  3 . 2 , especially roughly one ninth or one sixteenth of the total surface. 
         [0079]    Transversely to the line of slope A four laterally adjacent plates border the plate  3 . 2 , specifically the plates  3 . 4  and  3 . 5  and the edge plates  4 . 1  and  4 . 2 . The adjacent plates are arranged shifted relative to the plate  3 . 2  by a certain amount of overlapping less than one half diagonal length of the basic shape  7  in the direction A of the line of slope. Transversely to the line of slope A the adjacent plates are spaced such that overlapping regions form along the edges  13 . 1  to  13 . 4  of the plate  3 . 2 . The distance transversely to the line of slope is therefore greater than half the diagonal length of the basic shape  7 . The overlapping regions  12 . 1  to  12 . 4  perpendicular to the edges  13 . 1  to  13 . 4  have a dimension which is small compared to the edge length. In particular the dimension of the overlapping regions  12 . 1  to  12 . 4  perpendicular to the edge  13 . 1  to  13 . 4  corresponds roughly to one tenth of the edge length of the plate  3 . 2 . Preferably the width of the overlapping regions  12 . 1  to  12 . 4  is not less than 2 cm. 
         [0080]    With respect to the line of slope A, the two edge plates  4 . 1  and  4 . 2  as well as the two plates  3 . 4  and  3 . 5  are each located on the same side of the plate  3 . 2 . The overlapping regions  12 . 3  and  12 . 4  are located in the region between the plate  3 . 2  and edge plates  4 . 1  and  4 . 2  and the regions  12 . 1  and  12 . 2  between the plate  3 . 2  and plates  3 . 4  and  3 . 5 . 
         [0081]    The plate  3 . 2  in the corner region  11 . 2  at the lower corner  8  has a through opening  20 . 2 . The lower corner region  11 . 2  is bounded by imaginary extensions of the overlapping regions  12 . 1  and  12 . 4 . The corner region  11 . 2  for example has roughly the size of a photovoltaic cell. Furthermore the plate  3 . 2  in the upper corner region  11 . 1  on one corner  14  diagonally opposite the corner  8  likewise has a through opening  15 . 2  which for an overlapping arrangement with the adjacent plate  3 . 1  in the line of slope A is located congruently with its opening  20 . 1 . Likewise the through opening  20 . 2  is congruent with the through opening  15 . 3  of the plate  3 . 3 . The upper through opening  20 . 1  is farther from the edge or from the corresponding corner of the plate  3 . 2  than the through opening  20 . 2 . 
         [0082]    The edge plates of the line of slope  4 . 1  and  4 . 2  have a shape which is formed by straight-line division along the dividing lines  16 . 1  and  16 . 2  of a plate corresponding to the shape of the plate  3 . 2  in the direction of the line of slope A. The edge plates of the line of slope  4 . 1  and  4 . 2  form a termination of the surface  2  to the edge  9 . 2  which is parallel to the line of slope. The dividing line  16 . 1  and  16 . 2  does not pass through the through openings of the edge plates of the line of slope  4  which correspond to the through openings  20 . 1 ,  20 . 2  and  15 . 2 ,  15 . 3  so that the edge plates of the line of slope  4 . 1 ,  4 . 2  likewise have through openings comparably to the plate  3 . 2  and can be fastened using these through openings. The dividing lines  16  coincide with the edge  9 . 2 . The edge plates of the line of slope  4 . 1  and  4 . 2  are made identically. 
         [0083]    The transverse edge plates  6 . 1  and  6 . 2  have a shape which is formed by straight-line division along the dividing lines  18 . 1  and  18 . 2  of a plate corresponding to the shape of the plate  3 . 2  transversely to the line of slope A. The transverse edge plates  6 . 1  and  6 . 2  form a termination of the surface  2  to the edge  9 . 1  which is perpendicular to the line of slope A. The location of the dividing lines  18 . 1  and  18 . 2  depends on the arrangement of the plates  3 . 3  which are located nearest the edge region  9 . 1  in the direction of the line of slope A. Depending on the distance, the dividing lines  18 . 1  and  18 . 2  are made coincident with the edge  9 . 1  so that an edge which passes in a straight line through the transverse edge plates  6 . 1 ,  6 . 2  arises. The transverse edge plates  6 . 1  and  6 . 2  are therefore not made uniform and differ as a result of the above described half diagonal shift of the plates which are adjacent in the direction perpendicular to the line of slope A. 
         [0084]    The corner plate  5  has a shape which is attained for example by repeated division of the shape of the edge plates of the line of slope  4  in one direction perpendicular to the line of slope A. The location of the transversely lying dividing line  17  is chosen such that it coincides with the edge  9 . 1  or with the dividing lines  18 .  1  and  18 . 2  of the transverse edge plates  6 . 1  and  6 . 2 . Edge-side edges of the corner plate  5  thus form the corner  10  which is bordered by the edges  9 . 1  and  9 . 2 . 
         [0085]      FIG. 2  shows a schematic section of the arrangement of the plates  3 . 1  to  3 . 3  in the direction of the line of slope A. The plate  3 . 1  lies in the overlapping region  11 . 1  above the plate  3 . 2 , i.e. on the side which faces away from the support structure  30 . In the region  11 . 2  in turn the plate  3 . 2  lies over the plate  3 . 3 . The location of the plates  3 . 4  and  3 . 5  or of the edge plates of the line of slope  4 . 1  and  4 . 2  are shown by the broken line in  FIG. 2 . The plates  3 . 4 ,  3 . 5  and  4 . 1 ,  4 . 2  are arranged such that they are arranged at least in part in the regions  11 . 1  and  11 . 2  between the overlapping plates  3 . 1  and  3 . 2  as well as  3 . 2  and  3 . 3  which are adjacent in the direction of the line of slope A. In one system unit  1  as claimed in the invention all plates  3 . 1 ,  3 . 2 ,  3 . 3 ,  3 . 4 ,  3 . 5 ,  4 . 1 ,  4 . 2 ,  5 ,  6 . 1 ,  6 . 2  are arranged in the direction of the line of slope A according to the overlapping diagram shown in  FIG. 2 . 
         [0086]      FIG. 3  shows an enlarged view of the overlapping regions  11 . 2  without the uppermost plate  3 . 2  (which is shown only as a broken line). In the overlapping region  11 . 2  there is a sealing element  51  between the plates  3 . 2  and  3 . 3 . It is shaped such that it essentially fills the intermediate space formed by the plates  3 . 2 .,  3 . 3  and the plates  3 . 5  and  4 . 2  which are located in part in between. In other words, the gaps which exist in the spanning by the roof on the one hand between the plates  3 . 2  and  3 . 3  which overlap in sections and on the other hand the corners of the plates  4 . 2  and  3 . 5  spaced transversely to the line of slope are closed against wind and rain (which can be driven by the wind into the gaps). To achieve this, the sealing element  51  is made as follows. 
         [0087]    It consists preferably of rubber-elastic material and has a material which corresponds roughly to the thickness of the plate  3 . 5 . But it can be altogether slightly thicker so that the upper plate  3 . 2  is kept at a minimum distance of for example 1-2 mm over the plate  3 . 5  so that a capillary gap between the overlapping plates  3 . 2 ,  3 . 5  is not possible. 
         [0088]    The sealing element  51  has a through opening  55  for the fastening device  50 . It has a first and a second side  51 . 1 ,  51 . 2  which are for example at a right angle to one another and imitate the lower corner  8  of the upper plate  3 . 2  in terms of shape. The two sides  51 . 1  and  51 . 2  in the mounted state of the spanning by the roof as claimed in the invention are therefore flush with the corner  8  of the upper plate  3 . 2 . Since the sealing element  51  is made to mirror symmetrically (with respect to the line of slope) only one half is described below. The side  51 . 1  is followed by a hemispherical concave side  51 . 3 . The latter borders one of the two arms  52 . 1 ,  52 . 2  of the sealing element  51 . The arm  52 . 1  adjoins the edge  4 . 2 . 1  of the laterally adjacent plate  4 . 2 , which edge points down and runs obliquely to the line of slope (in the same way the arm  52 . 1  adjoins the edge  3 . 5 . 1  of the plate  3 . 5 , which edge points down). The outermost end of the arm  52 . 1  is preferably directly under the edge (shown by the broken line) of the upper plate  3 . 2 . The top side  51 . 4  of the sealing element  51  is for example likewise circular arc-shaped with a greater radius of curvature than the side  51 . 3 . On the side  51 . 3  which is pointed up (with respect to the line of slope) two finger elements  53 . 1 ,  53 . 2  are molded and offer a flexible stop for the corners of the plates  4 . 2  and  3 . 5 , which corners lie in the corner region  11 . 2 . The plate-shaped sealing element  51  preferably does not project beyond the overlapping region  11 . 2 . Subject to the recesses formed by the concave sides  51 . 3 , the sealing element  51  has room in a triangle which is bordered by half of the overlapping region  11 . 2 . 
         [0089]      FIG. 4  shows one preferred embodiment of the fastening device  50 . A support bar  54 , of which only one wall extract is shown, has a threaded insert  55  which is made in the manner of a tube section which projects into the interior of the support bar  54 , with an inside thread. The threaded insert  55  constitutes a mechanically prepared fastening site as claimed in the invention on the support bar  54 . The end  56 . 1  of the pin  56  is screwed into this threaded insert  55  as far as a stop which is made on the pin  56  (for example, a shoulder  57 ). The pins  56  which consist preferably of stainless steel can therefore be rigidly connected to the support bar  54  and can project perpendicularly to the longitudinal axis of the support bar  54 . 
         [0090]    On its upper end  56 . 2  the pin  56  has a blind hole  58  with an internal thread for an external fastening screw  59 . The pin  56  is located in the center of a tubular support part  60  of a preferably elastic material. The support part  60  with its lower face side  60 . 1  rests on the support bar  54 . At a first distance to the lower face side  60 . 1  a first shoulder  61  is made which forms a first support position for the plate  3 . 3 . The shoulder  61  runs around the support part  60  at a height which is for example less than half the height of the support part  60 . Between the support bar  54  and the lower plate  3 . 3  there is therefore a distance which corresponds roughly to the thickness of one plate. 
         [0091]    Above the shoulder  61  the outer cross section of the support part  60  is less than underneath the shoulder  61 . The through opening  15 . 3  which is provided in the plate  3 . 3  is dimensioned such that the part of the support part  60  which is located above the shoulder  61  can be routed through it. Preferably the support part  60  can be attached in the through opening  15 . 3  in a press fit. This facilitates mounting since the plate  3 . 3  together with the support part  60  can be pulled over the pin  56 . Fewer separate parts need be assembled at the building site. 
         [0092]    The free inside diameter of the support part  60  in this example is clearly for example 30-100% larger than the diameter of the pin  56 . In this way the cover plates can be adjusted relative to the support bars in a comparatively large range of variation (for example on the order of centimeters). 
         [0093]    In the region of the fastening device the sealing element  51  lies on the plate  3 . 3  whose thickness in this example is roughly one fourth of the height of the support part  60 . Its thickness is preferably greater than the thickness of the plate  3 . 3 . 
         [0094]    The through opening  20 . 2  in the upper plate  3 . 2  is smaller than the outer cross section of the upper end of the support part  60  so that the plate  3 . 2  can be supported on the support part  60  without the support part  60  projecting through the through opening  20 . 2 . Since the fastening screw  59  must be routed through the through opening  20 . 2  from overhead, the diameter of the through opening should correspond at least to the diameter of the fastening screw  59  and should preferably be at least 20% greater. 
         [0095]    In the embodiment as shown in  FIG. 4 , the pin  56  projects into the through opening  20 . 2 , but does not penetrate it completely. This means that the pin does not project over the outer main surface of the plate  3 . 2 . In other words, the pin  56  is longer than the support part  60 , but shorter than the sum of the length of the support part  60  plus one plate thickness. In this way the plate  3 . 2  cannot slide away during mounting (i.e. before clamping tight). 
         [0096]    The through opening  20 . 2  is covered by a dome-shaped cap against the penetration of rain water. The edge of the cap  62  therefore forms a sealing lip relative to the upper main surface of the plate  3 . 2 . The cap  62  has a central opening  63  for the fastening screw  59 . The cap  62  is elastic so that it ensures a peripherally running seal around the through opening  20 . 2  when the fastening screw  59  is tightened. At the same time it allows flexible (i.e. not rigid) holding of the plate  3 . 2 . In this way distortions can be equalized which can arise for different thermal expansion of plates, support bars and the fastening device. 
         [0097]    The lower edge of the cap  62  which lies on the plate  3 . 2  is annular and has roughly the same diameter as the upper face side  60 . 2  of the support part  60  on which the plate  3 . 2  rests. As is apparent in  FIG. 4 , the upper edge of the support part  60  is relatively thin. In particular, it is thinner than the lower edge which rests on the support bar  54 . 
         [0098]    The dome shape of the cap  62  makes the connection between the fastening screw  59  and the plate  3 . 2  elastic in the direction of the pin axis. At the same time there is also a certain elasticity of holding transversely to the pin axis. 
         [0099]      FIG. 5   a  shows a plate  100  which is designed as a solar panel or photovoltaic module. The plate  100  has a square or diamond outline with four edges  101 . 1 , . . . ,  101 . 4  and is aligned with reference to the line of slope A such that the square is on one corner  102  and a diagonally opposite corner  103  is likewise on the line of slope A which passes through the corner  102 . The corner  102  is called “down” (with respect to the line of slope) and the corner  103  is called “up”.  FIG. 5   b  shows a section through the plate  100  along the line of slope A (in plane B). The plate  100  encompasses a square plate  104 , for example of plastic or glass. The plate  104  lies outside here, i.e. during installation according to plates  3 . 1 , . . . ,  3 . 5  of  FIGS. 1-3  on the side facing away from the support structure  30 . On the back, i.e. on the side facing away from the surface  30 , a film or another glass or plastic plate  105  can be applied. Between the plates  104  and  105  there are solar cells  106 . 1 ,  106 . 2 ,  106 . 3  which are made as square panes in  FIGS. 5   a  and  5   b . The solar cells  106  can however also be configured as strips or in any other shape which appears suitable. In  FIGS. 5   a ,  5   b  there are  15  solar cells  106 . 1 ,  106 . 2 ,  106 . 3  which each have a square outline. The square solar cells  106 . 1 ,  106 . 2 ,  106 . 3  are arranged in a regular 4×4 pattern with edges aligned parallel to the edges  109  of the basic shape  101 , in one corner of the 4×4 pattern one solar cell being omitted (“n 2 −1” arrangement). 
         [0100]    Adjacent solar cells have a first distance  107  to one another. The solar cells which lie on one edge of the square outline  101  of the plate  100  are moreover spaced by a second distance  108  away from the edge of the basic outline  101 . On the upper corner  103  a square region  110  is left open (i.e. it does not have a solar cell) which corresponds to the area which a sixteenth solar cell would occupy in a regular 4×4 pattern. The solar cells  106  are cabled to one another and on the back preferably have a possibility for tapping of the generated solar power (cabling and tap not shown). It can be for example a plug outlet or cable connections. 
         [0101]    The second distance  108  which is drawn to the edge  109 . 4  corresponds roughly to one twentieth of the edge length of the square outline  101 . The indicated distance  108  can however if necessary also be chosen differently and is preferably larger than 2 cm, in particular the distance  108  can be roughly 3.5 cm. The first distance  107  which exists between adjacent solar cells can be varied within wide limits. For maximum utilization of incident solar radiation it is chosen to be as small as possible. But if the plate is however also to be used for light inlet, the distance  107  is chosen to be larger. In the figure the first distance  107  is roughly one tenth of the second distance  108 . 
         [0102]    The second distance  108  is preferably chosen such that it corresponds essentially to the width of the overlapping regions  12 . 1 , . . . ,  12 . 4  in the direction perpendicular to the edges  13 . 1 , . . . ,  13 . 4  when installed according to  FIGS. 1 to 3 . This results in that due to the overlapping of adjacent plates no solar cell is hidden. For the same reasons the region  110  left open on the upper corner  103  is preferably dimensioned such that it corresponds to the overlapping region  11 . 1  or  11 . 2  of the plates which are adjacent in the direction A of the line of slope, for example  3 . 1 - 3 . 3 , when the plate is installed according to  FIGS. 1 to 3 . 
         [0103]    Within the framework of the preferred execution of the distance  108  and of the region  110  which are dictated by the arrangement of plates  100  in the overlapping as claimed in the invention, the distance  107  however and the size and number of individual solar cells  106  can be matched depending on the requirement. For example, it is also conceivable to arrange only 8 solar cells in a regular 3×3 pattern, in turn the missing field being made on an upper corner. Likewise strip-shaped solar cells can be used which leave exposed the regions on the plate  100  which are preferably to be kept free. 
         [0104]    The plate  100  similarly to the version of the plates  3  of  FIGS. 1 to 3  has an upper and a lower through opening  111  or  112 , the upper through opening  111  being larger than the lower through opening  112 . The lower through opening  112  is made in a corner section which is free of solar cells on the corner  102 . The through opening  112  passes through the outside plate  104  and the rear plate or film  105  and lies on the line of slope A which passes through the corners  102  and  103  of the plate  100 . 
         [0105]    The upper through opening  111  is made in the region  110  which is free of solar cells. The latter corresponds in size roughly to the corner region  11 . 1  or  11 . 2 , as is shown in  FIG. 1 . In particular the through opening  111  is formed on the lower (i.e. pointed toward the center of the plate) corner  113  of the square region  110  and likewise lies on the line of slope A. But it is also conceivable to make the passage openings on other regions of the plate  100  which are free of solar cells. Depending on the arrangement of the plates  100  in overlapping and/or fastening arrangements for fastening of the plates  100 , the through openings can also be arranged horizontally in the region between two solar cells and/or not on the line of slope A. 
         [0106]      FIG. 6  shows how the photovoltaic outer building skin is mounted. First, several support bars  70 . 1 - 70 . 3  are fixed on the substructure  71  for the roof The support bars  70 . 1 ,  70 . 2 ,  70 . 3  are for example steel sections and are each provided with several industrially prepared fastening sites  72 . 1  . . .  72 . 3  and  72 . 4  . . .  72 . 6  and  72 . 7  . . .  72 . 9 . Each fastening site  72 . 1 ,  72 . 9  includes a fastening device  50  ( FIG. 4 ) with which two plate corners at a time can be connected to the support bar. Each plate on two diagonally opposite corner regions (compare through openings  111 ,  112  in  FIG. 5 ) are connected to a support bar. If the edge plates are ignored, one fastening device per cover plate as claimed in the invention must be prepared. 
         [0107]    The adjacent fastening sites  72 . 1  and  72 . 2  have a distance e corresponding to the mutual distance of the through openings  111  and  112  of one plate ( FIG. 5   a ,  5   b ). In a 4×4 arrangement of the solar cells in the plate the distance is roughly  3 / 4  of the diagonal of the plate, in a 5×5 arrangement the distance is roughly 4/5 of the diagonal of the plate. Generally the distance of the fastening sites for square plates is roughly (n−1)/n of the diagonal of the plate. 
         [0108]    The support bars are screwed tightly on the substructure  71  and span the surface  2  which captures the sunlight. The mutual distance d of the longitudinal center axes of the support bars  70 . 1 - 70 . 3  follows from the desired geometry of the plate arrangement. For square cover plates the distance d is larger by a certain amount c than the half diagonal of the cover plates. The amount c is smaller than the half diagonal of the region  110  which is free of solar cells and which is detailed in  FIG. 5 . 
         [0109]    The fastening sites  72 . 1 ,  72 . 2  and  72 . 4 ,  72 . 5  of adjacent support bars  70 . 1 ,  70 . 2  are offset to one another in the direction of the line of slope so that diagonal laying of the cover plates is possible. Preferably the support parts  70 . 1 , . . . ,  70 . 3  are produced and delivered with fastening sites which are made offset accordingly so that the support bars  70 . 1 , . . . ,  70 . 3  can always be mounted on site flush with the planned edge of the surface  2 . In this example therefore at least two different types of support bars  70 . 1  and  70 . 2  are prepared industrially and differ from one another in that the fastening which is the first at the time is spaced differently relative to the end of the support bar. In this way it is possible to prepare the part of the outer building skin as claimed in the invention as an industrially fabricated system unit. This reduces installation costs. 
         [0110]    At this point the pins (compare  FIG. 4 , pin  56 ) can be attached at the fastening sites  72 . 1 , . . .  72 . 9 . In the sense of one version the pins can be attached industrially to the support bars so that the support bars with the pins mounted can be delivered to the building site and fewer individual parts need be mounted at the building site. 
         [0111]    Afterwards the cover plates are installed. Generally first the edge plates must be installed along the lower end of the support bars. The roofer works from right to left or vice versa and lays one row which is located at the same height. Since mounting of the edge plates takes place essentially according to the same principle as for the plates, only laying of one (further) row of plates is explained below. 
         [0112]    One support part ( FIG. 4  support part  60 ) is laid over the pins on which the upper corner of the plate is to be attached. Then the plate is placed on the support parts of the adjacent fastening sites of the support bar. In doing so the lower through opening (compare  112  in  FIG. 5   a ) is placed on the upper face side of the support part of the lower fastening site and the upper through opening (compare  111  in  FIG. 5   a ) on the shoulder ( FIG. 4 , shoulder  61 ) of the upper fastening site. 
         [0113]    Next, the sealing element (compare  51  in  FIG. 3 ) is placed on the support part  60 . Since the sealing element can be turned around the support element, it can be easily placed in the position which is suitable for the adjacent cover plates. 
         [0114]    To tightly clamp the cover plate, the screw  59  is inserted through the cap  62  and is screwed into the pin  56 . Here the cover plate is not held in an immovable position, but can be shifted somewhat as required transversely to the line of slope or along the line of slope. Since the plate is clamped only between the rubber parts (support part/cap), therefore adjustment can also take place after attaching the screw  59 . The preferred fastening device allows a relatively stable connection between the lower corner of the cover plate and the support bar. 
         [0115]    As is shown in  FIGS. 3 and 4 , there can be a sealing lip  82  between two overlapping cover plates  80 ,  81 . This lip is attached on the upper main surface  83  of the lower cover plate  81 . The same seal can be provided on the side of the cover plate which is mirror-symmetrical with respect to the line of slope. This “over corner” arrangement is shown in  FIG. 3  using the sealing lips  84 . 1 ,  84 . 2 . The two remaining (or diagonally opposite) sides conversely do not have these sealing lips.  FIG. 8   a  shows a top view of one version of a sealing element  51 .  FIG. 8   b  shows a corresponding section of the sealing element along the section line A-A.  FIG. 8   a  shows the sealing element  51  together with plates  3 . 2 ,  3 . 3 ,  4 . 2 ,  3 . 5 ,  FIG. 8   b  shows the sealing element  51  without these plates. As already shown in  FIG. 3 , the version of the sealing element  51  now being discussed is located between the plates  3 . 2  and  3 . 3 . The plate  3 . 2  is shown in  FIG. 8   a  only by the broken line, in order to specify the site at which this plate comes to rest. The plate  3 . 3  is shown in extract in  FIG. 8   a . The sealing element is shaped such that it seals the intermediate space formed by the plates  3 . 2 ,  3 . 3  and the plates  4 . 2  and  3 . 5  which are arranged in part in between. The plates  4 . 2  and  3 . 5  are shown in extract in  FIG. 8   a , the plate  4 . 2  being located to the left of plate  3 . 2  and the plate  3 . 5  to the right of plate  3 . 3 . 
         [0116]    The sealing element  51  has a through opening  55 . In the installed state the sealing element  51  rests on the plate  3 . 2  and can be cemented for example on the plate  3 . 2 . The circular arc-shaped arms  52 . 1 ,  52 . 2  which are shaped to one another, specifically the left arm  52 . 1  and the right arm  52 . 2 , extend from the left plate  4 . 2  to the right plate  3 . 5 . On the circular arc-shaped arms  52 . 1  and  52 . 2  a sealing lip  84 . 3  which is circular arc-shaped relative to the through opening  55  is molded. 
         [0117]    As is known from  FIG. 3 , the sealing lips  84 . 1  and  84 . 2  are attached to the edges of the plate  3 . 2 . Likewise, on the edges of the left plate  4 . 2  a sealing lip  84 . 5  and of the right plate  3 . 5  a sealing lip  84 . 6  are attached. The sealing lips  84 . 1 ,  84 . 2 ,  84 . 5 ,  84 . 6  can be for example cemented on. 
         [0118]    The circular arc-shaped arms  52 . 1  and  52 . 2  encompass one left end  52 . 11  and one right end  52 . 21  which directly adjoin the cover plates  4 . 2  and  3 . 5 , at this point a sealing site between the cover plates and the sealing element  51  being formed. As is shown in  FIG. 8   a , one region of the ends  52 . 11 ,  52 . 21  runs parallel to the sealing lip  84 . 1 ,  84 . 2 . 
         [0119]    The sealing element  51  and/or the circular sealing lip  84 . 3  consist preferably of a rubber-elastic material. Materials for the sealing lip  84 . 3 , but also for the sealing lips  84 . 1 ,  84 . 2 ,  84 . 5 ,  84 . 6  can be for example EPDM (ethylene-propylene-diene rubber) or a silicone. The rubber elastic material is preferably made soft so that a small contact pressure of the plates is enough to establish a seal. The thickness of the sealing element  51  with the circular sealing lip  84 . 3  corresponds to the sum of the thickness of one plate  3 . 5  and the thickness of the sealing lip  84 . 1 ,  84 . 2 . The thickness of the ends  52 . 11 ,  52 . 21  corresponds to the thickness of the sealing lips  84 . 1 ,  84 . 2 . 
         [0120]    With the cover plate  3 . 2  installed, between the plate  3 . 2  and the plate  4 . 2  a seal is established along the sealing lip  84 . 5  of the left plate  4 . 2 , between the plate  3 . 2  and the plate  3 . 3  along the sealing lip  84 . 3  of the sealing element  51 , and between the plate  3 . 2  and the plate  3 . 5  along the sealing lip  84 . 6  of the right plate. Thus the cover plate  3 . 2  is completely sealed relative to the underlying plates along a closed line. 
         [0121]    Moreover, there is a seal between the plate  4 . 2  and the underlying plate  3 . 3  along the sealing lip  84 . 1  and a corresponding seal between the plate  3 . 5  and the plate  3 . 3  along the sealing lip  84 . 2 . A closed and complete union of seals is formed on the ends  52 . 11  and  52 . 21  of the sealing element  51  by a seal existing between the sealing lip  84 . 1  and the end  52 . 11  (or the sealing lip  84 . 2  and the end  52 . 21 ) which adjoin one another along corresponding side surfaces, and by a seal existing between the face side of the plate  4 . 2  and the face side of the end  52 . 11  (or between the face sides of the plate  3 . 5  and the end  52 . 21 ). 
         [0122]      FIG. 9   a  shows a detailed view of the end  52 . 21  of the sealing element  51  which is labelled C in  FIG. 8   a . As is apparent from  FIG. 9   a , the end  52 . 21  has a straight area  52 . 210  which adjoins one side of the sealing lip  84 . 2 . In this way a seal is formed between the end  52 . 21  and the sealing lip  84 . 2 . The end  52 . 21  furthermore has a step, as is apparent from  FIG. 9   b , the thickness of the thinner part corresponding to the thickness of the sealing lip  84 . 2  and the thickness of the thicker part corresponding to the sum of the thickness of one plate  4 . 2  and one sealing lip  84 . 2 . 
         [0123]    In order to effect deformability of the sealing lips and thus a seal, the sealing lips  84 . 1 ,  84 . 2 ,  84 . 3 ,  84 . 5 ,  84 . 6  have different flanks with the corresponding 45° flank angle. On the ends  52 . 11 ,  52 . 21  these 45° flanks are also continued for the thinner part. In the middle region  52 . 211  of the end  52 . 21  (or analogously of the end  52 . 11 ) the flanks of the sealing lips are interrupted as shown in  FIG. 9   a , so that the bendability and deformability are additionally increased so that the ends  52 . 11 ,  52 . 21  rest for example more lightly on the plates  4 . 2 ,  3 . 5 . 
         [0124]      FIG. 10   a  shows the side view B of the sealing element  51  marked in  FIG. 9   a . The sealing element  51  encompasses the through opening  55  and the right end  52 . 21 . In  FIG. 10   b  in the detailed view E the right end  52 . 21  is shown enlarged. As is apparent from  FIG. 10   b , the end  52 . 21  encompasses several flanks with a 45° flank angle. The side  52 . 212  of the sealing element  51  facing the sealing lip  84 . 2  in the installed state has a cam  52 . 213  and has a tilt angle  52 . 214  which can be for example 105°. In this way the side  52 . 212  is matched to the shape of the sealing lip  84 . 2 , as a result of which installation of the sealing element  51  is simplified and the seal is improved. Sealing between the sealing lip  84 . 2  and the end  52 . 21  can be additionally improved by the choice of the angle of incline  52 . 214  and the shape of the cam  52 . 213 . Thus a cam which is shaped half-round or oval can be used which is favorably deformed with the corresponding pressure of the overlying plates in the direction of the sealing lip  84 . 2  and thus increases the seal. 
         [0125]      FIG. 11  is a perspective of the described version of the sealing element  51  and shows the through opening  55 , the two ends  52 . 11  and  52 . 21  and the sealing lip  84 . 3 . 
         [0126]    A roof which is built with the described cover plates and sealing elements is also rainwater-tight even for relatively small overlapping of the cover plates of for example 3 cm and a small slope of the cover plates of for example 5°. 
         [0127]    The described embodiments can be modified in various respects. 
         [0128]    In the fastening device the support part, instead of a round cross section, can have a different outer cross section (for example an oval or polygonal cross section). The free inner cross section can also be non-circularly symmetrical instead of circular (with free adjustability in all directions). For example, a slot-shaped cross section which limits the adjustability to one direction should also be mentioned. 
         [0129]    Instead of a threaded insert, a projecting threaded pin can be attached to the fastening sites. A pipe piece with an inner thread can for example be screwed onto this pin. 
         [0130]    The pin  56  need not consist of steel. It could for example be made also as a plastic molding to which the support part is captively attached. 
         [0131]    In the figures the recesses are made as round through openings. The shape of the recess can however also be non-round. In particular, it is also conceivable for the recess to open in the lower corner toward the edge (whether toward the corner or toward an edge site which lies next to the corner). Another modification consists in that the upper through opening is replaced by a coupling device which is attached on the back of the cover plate. It could for example be operated from the face side of the cover plate. The advantage of this construction consists in that the surface which captures the sunlight is not interrupted. The building skin facing the weather would then not have any projecting parts. 
         [0132]    The cover plates need not be square. In particular the corners can be rounded or cut off. Furthermore, it is possible to recess the plate in the square region  110  free of solar cells (or to cut off the corner  103 ), so that the region free of solar cells is for example only half as large or much smaller in terms of material, as shown in  FIG. 5   a.    
         [0133]    It is important that the three sealing systems, specifically the cap ( 62 ), the plate-shaped sealing element ( 51 ) and the sealing lip ( 82 ) can also be properly used for “straight” laying. Each of these three sealing systems can also be used individually, i.e. independently of the others. 
         [0134]    In summary, it can be maintained that the invention makes available a unit which forms an integrated part of the weatherproof building skin. The unit acts aesthetically not as an addition, but as the character of the building jacket. Finally, mounting is easy and defective cover plates can also be subsequently replaced with little effort.