Abstract:
Photovoltaic solar panels are a know means of generate electricity from ultra-violet and solar power. Known problems associated with photovoltaic solar panels include poor efficiency and a short apparatus lifespan; alongside an inability to be easily integrated into architectural surroundings. Disclosed herein is a photovoltaic solar panel, designed to be attached to the front face of a roof tile, which generates electricity with an improved efficiency, has increased longevity and can be incorporated into a variety of architectural surroundings.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a photovoltaic solar panel. 
       BACKGROUND OF THE INVENTION 
       [0002]    Photovoltaic solar panels are known which absorb solar and ultra violet rays, transforming them into electrical energy. 
         [0003]    Referring to  FIG. 1  herein, there is illustrated schematically in perspective view an installation comprising a plurality of known solar roof tiles, integrated into an existing concrete tile roof. Each solar roof tile has a width of approximately 3 concrete roof tiles. To install the solar roof tiles, rows of individual roof tiles are removed, and the solar roof tiles are fitted to the rafters of the roof in place of the concrete roof tiles. Electrical connections to the solar roof tiles are passed through the water proof membrane of the roof, and the electrical connectors at the rear of each roof tile are connected into an electrical circuit within the loft of the roof. Alternatively, the electrical connectors can be connected together on top of the water impermeable membrane, and routed to the edge of the roof, so that a single electrical cable is fitted outside the building down to an electrical junction box at ground level. 
         [0004]    Referring to  FIG. 2  herein, there is illustrated schematically in detail, part of a solar roof tile as shown in  FIG. 1  herein. The solar roof tile comprises a relatively thick sheet of substrate  200 , for example made of a plastic sheet, of a thickness similar to the thickness of the adjacent concrete tiles. On top of the plastic substrate, are positioned a plurality of substantially square solar panels  201 . On top of the solar panels, is positioned a glass or plastics cover sheet  202 , which is held to the plastic substrate by a plurality of external clips  203  around the edges of the clear transparent plastics sheet. 
         [0005]    Referring to  FIG. 3  herein, there is illustrated schematically in perspective view, a pair of solar tiles as shown in  FIGS. 1 and 2 . 
         [0006]    Referring to  FIG. 4  herein, there is illustrated schematically in cross sectional view part of a known photovoltaic solar panel. The solar panel  400  comprises a back sheet  401 ; first and second encapsulation layers  402 ,  403 ; a photovoltaic cell  404 ; and an ultra-violet resistant glass or plastic screen front sheet  405 , which protects the panel against mechanical impact and weathering. 
         [0007]    The back sheet portion  401 , of the photovoltaic solar panel  400  comprises two surfaces  406 ,  407 , wherein the first surface  406  may be attached to the surface of a roof tile. The second surface of the back sheet portion  407  is adjacent to a first surface  408  of encapsulation layer  402 ; and a second surface  409  of first encapsulation layer  402  is in adjacent contact with the photovoltaic cell  404 . The photovoltaic cell is also in adjacent contact with a first surface  410  of second encapsulation layer  403 ; and a second surface  411  of second encapsulation layer  403  is in adjacent contact with a first surface  412  of the front sheet  405 . 
         [0008]    The term “adjacent contact with” does not necessarily mean that the second surface of the encapsulation layer is in contact with a surface of the photovoltaic cell. A layer of encapsulation material may be used between the photovoltaic cell and the back sheet  401  and/or the front sheet  405   
         [0009]    Polyethylene terephthalate PET is a known encapsulation material, which is used in solar panels to bond front and back sheets of the panel together by the process of lamination. 
         [0010]    Lamination of solar cells with polyethylene-vinyl acetate films is conducted at about 150° C., and permits molten polyethylene-vinyl acetate to flow into voids in a solar panels to encapsulate the solar cell. 
         [0011]    The current lifespan of PET solar panels is in the region of 5 to 10 years. 
         [0012]    Known photovoltaic panels do not integrate well into the architecture of older, traditional buildings. 
       SUMMARY OF THE INVENTION 
       [0013]    It is an object of the current invention to increase the efficiency and lifespan of current solar panels whilst providing a photovoltaic solar panel which can be easily integrated into various architectural surroundings. 
         [0014]    According to a first aspect of the present invention, there is provided a photovoltaic solar panel for attachment to a roof tile configured with a through aperture, the panel comprising: 
         [0015]    a rigid back plate; 
         [0016]    a support sheet comprising at least one photovoltaic solar cell; 
         [0017]    a negative and a positive connection extending from the or each solar cell through a sealed aperture of the back plate and accessible at the rear of the panel; 
         [0018]    a diode connected to the positive connection; 
         [0019]    an ultra-violet resistant front sheet for covering a front face of the or each solar cell; 
         [0020]    wherein the back plate, support sheet and front sheet form a sealed laminated structure. 
         [0021]    Other aspects of are as recited in the claims herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which: 
           [0023]      FIG. 1  show schematically a known solar tile in a roof installation; 
           [0024]      FIG. 2  shows schematically a detail of the known solar tile of  FIG. 1  herein; 
           [0025]      FIG. 3  shows schematically two known solar tiles prior to installation in a roof; 
           [0026]      FIG. 4  is a schematic cut away view of a known photovoltaic solar panel; 
           [0027]      FIG. 5  illustrates schematically a first embodiment solar panel and roof tile in exploded view; 
           [0028]      FIG. 6  illustrates schematically in view from the front, a solar panel comprising the first embodiment solar tile; 
           [0029]      FIG. 7  is an exploded view of a second embodiment photovoltaic solar panel and roof tile; 
           [0030]      FIG. 8  is an enlarged view of a printed circuit board of the solar tile of  FIG. 7  herein; 
           [0031]      FIG. 9  is a perspective view of a cross-section taken along line ‘A’ in of the circuit board of  FIG. 8 ; 
           [0032]      FIG. 10  is a perspective view of an improved solar roof tile incorporating a solar panel disclosed herein; 
           [0033]      FIG. 11  is a plan view of the improved solar roof tile of  FIG. 10  herein; 
           [0034]      FIG. 12  is a cross-section along plane ‘C’ of  FIG. 11 ; 
           [0035]      FIG. 13  is a close up view of one end of  FIG. 12  herein; 
           [0036]      FIG. 14  is an illustration of one stage of a photovoltaic solar panel manufacturing process; 
           [0037]      FIG. 15  is an illustration of another stage of manufacture of the photovoltaic solar panel; 
           [0038]      FIG. 16  illustrates schematically in view from the front, a solar cell comprising a solar panel described herein; 
           [0039]      FIG. 17  illustrates schematically the solar cell of  FIG. 16  in view from the rear; and 
           [0040]      FIG. 18  illustrates schematically circuit diagram for connecting a plurality of solar roof tiles as described herein before in a solar roof panel installation. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0041]    There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description. 
         [0042]    There is disclosed herein a novel photovoltaic solar panel designed to be attached to the front face of proprietary concrete, clay, metal or plastic roof tile. The solar panel is capable of generating electricity and thus providing a solar tile. The solar tile may be fitted directly to a roof to form a flat roof surface. The apparatus is designed to fit to new and replacement roofs. 
         [0043]    Referring to  FIG. 5  herein, there is illustrated schematically in exploded view a first embodiment solar tile incorporating a novel solar panel. 
         [0044]    The roof tile comprises a roof tile  500 , which can be a cement, plastics or metal roof tile. The solar panel comprises a silicone based adhesive sealant layer  501 ; a fiber glass back plate  502 ; a sheet  503  comprising a one or a plurality of monocrystalline or polycrystalline solar cells each comprising one or more solar wafers; and an ultra-violet transparent plastics cover sheet  504 . 
         [0045]    The one or more solar cells are sandwiched between the clear cover sheet  504 , on the side of the wafer which is exposed to sun light, and the fiber glass back plate  502  at the rear side, which is adjacent the roof tile  500 . The silicone based adhesive sealant layer  501  sticks a rear surface of the fiber glass back plate  502  to a front surface of the roof tile  500 . The fibre glass back sheet gives rigidity and support to the sheet  503  which contains the solar cells. 
         [0046]    The solar panel further comprises electrical connections which are accessible at the rear of the roof tile, for connecting the solar panel to an electrical circuit. The electrical connections comprise a negative connector  505 ; a positive connector  506 ; a silicone based seal  507 , which fits into an aperture in the roof tile  500  and surrounds a pair of positive and negative conductors  508 ,  509  respectively such that the connectors are spaced apart, and protected from the weather and moisture; each electrical conductor  508 ,  509  comprising a copper wire surrounded with an insulating plastic sheath; a diode  510  connected to a positive output of the solar cells  503  and to positive conductor  509 ; and first and second aluminum strips  511 ,  512  which respectively form electrical connectors to the solar cells of the sheet  503 , the aluminum strips each being covered with a respective strip of insulating electrical tape, the first strip  511  being connected to the positive conductor  509  via diode  510 , and the second aluminum strip  512  being connected to the negative conductor  508 . 
         [0047]    The clear or transparent plastics cover sheet  504 , the solar wafer sheet  503 , along with first and second aluminum strip conductors  511 ,  512 , and the fiber glass back plate  502  form a sealed laminated unit, which is sealed against the ingress of moisture. 
         [0048]    Referring to  FIG. 6  herein, there is illustrated schematically in frontal view, an individual solar wafer. The solar wafer has general characteristics as follows: 
         [0049]    In the example shown, a Monocrystalline P type boron doped silicone sheet has dimensions 156 mm height by 156 mm width. The Monocrystalline silicon wafer is grown by the CZ method. Electrical characteristics of the solar sheet are as follows: 
         [0000]    
       
         
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Features 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 General Characteristics 
                   
               
               
                   
                 Resistivity 
                 1~3, 3~6 Ω · com 
               
               
                   
                 Oxygen Content 
                 1 × 10 18 atom/cm3 
               
               
                   
                 Carbon Content 
                 1 × 10 17 atom/cm 3 
               
               
                   
                 Structural Characteristics 
               
               
                   
                 Side 
                 156.0 mm ± 0.5 mm 
               
               
                   
                 Diameter 
                 200.0 mm ± 0.5 mm 
               
               
                   
                 Orientation 
                 &lt;100&gt; 
               
               
                   
                 Thickness 
                 180 ± 20 μm 200 ± 20 μm 
               
               
                   
                 Mechanical Characteristics 
               
               
                   
                 TTV 
                 ≦40 μm 
               
               
                   
                 Bow 
                 ≦70 μm 
               
               
                   
                 Surface 
                 No microcrystalline structure 
               
               
                   
                 Saw Mark 
                 ≦15 μm 
               
               
                   
                   
               
             
          
         
       
     
         [0050]    Whilst  FIG. 6  shows a best mode embodiment monocrystalline silicon solar wafer, variations to the dimensions may be applied in other embodiments. 
         [0051]    Referring to  FIG. 7  herein a second embodiment photovoltaic solar panel  700 , designed to be attached to the front surface of a roof tile  701 , comprises a male plug DC connector  702 , inserted from the front side of the tile; a female plug  703  located in a hole drilled through said tile; a printed circuit board  704 ; a junction box  705 , permanently sealed to the back of said circuit board; which houses a diode  706 , which is connected to positive and neutral wires  707 ,  708 , extending from the female plug  703 ; said wires are in turn connected to the circuitry of the circuit board  704 . 
         [0052]    A solar array  709  is provided and consists of a plurality of monocrystalline solar wafers  710  which are connected together in a bank of two rows. 
         [0053]    The junction box is rated at 1000 dcV. 
         [0054]    Each solar wafer  710  is situated on a layer of ethylene-vinyl acetate  711 , which covers the surface of the printed circuit board  704 . 
         [0055]    Soldered aluminum strips  712  connect individual solar cells  710 ; the ends of said strips are folded over the top of the cells  710  to attach them to the circuit board  704 . 
         [0056]    The aluminum strips are covered by a strip of electrical tape and a sheet of ethylene-vinyl acetate  713 . A layer of ethylene tetrafluoroethylene  714  covers the ethylene-vinyl acetate  713 . 
         [0057]    The total layered array is bound via lamination at a temperature range of 150° C. to 200° C., a vacuum pressure of 2 to 4 atmospheres for a period of 10 to 15 minutes. 
         [0058]    Referring to  FIG. 8  herein, the printed circuit board  704  comprises a substrate board  801 , substantially rectangular in shape; negative and positive electrical conductive tracks  802 ,  803 ; and an aperture  804  which extends through the circuit board  704 . 
         [0059]    Referring to  FIG. 9  there is shown a perspective view of a cross-section taken along line ‘A’ in  FIG. 8 , wherein, the aperture through the circuit board  704  is visible. 
         [0060]    Referring to  FIG. 10  herein there is shown a perspective view of a third embodiment improved solar roof tile and solar panel  1000 , comprising a substantially rectangular, flat roof tile  1001 , with first and second through tile apertures  1002 ,  1003 , equidistant from a perimeter of the tile, and grooves  1004 ,  1005  on the extreme edges of the tile to enable attachment of the tile to a roof; and a substantially rectangular photovoltaic solar panel  1006 , fixed to a front face of the roof tile the solar panel having area dimensions smaller than the area dimensions of a front face of the roof tile. 
         [0061]      FIG. 11  is a plan view of an improved solar roof tile and panel  1000 , shown in  FIG. 10  herein, comprising a substantially rectangular, flat roof tile  1001 , with through tile apertures  1002 ,  1003 , equidistant from the perimeter of the tile and grooves on the extreme edges of the tile  1004  to enable attachment of the tile to a roof; and a substantially rectangular photovoltaic solar panel  1004 , which is smaller than the dimensions of the roof tile. 
         [0062]    Referring to  FIG. 12  herein, there is shown a cross-section along plane ‘C’ of  FIG. 11  in which the height of the roof tile  1001  extends beyond the height of the photovoltaic solar panel  1006 , and in which the circle annotation denotes that the degree of overlap between the tile and the photovoltaic solar panel is variable and determined by the manufacturer. 
         [0063]    Referring to  FIG. 13  herein, in close up detail part of the cross section of  FIG. 12 , showing the laminate structure of the solar panel affixed to the front of the roof tile. 
         [0064]    Referring to  FIG. 14  herein, there is illustrated a view of one stage of a manufacturing process for making a solar panel and roof tile as described herein, in which a plurality of mono crystalline solar wafers  1401  are arranged on a circuit board  1402 , on a layer of ethylene-vinyl acetate and are connected together by soldered aluminum wires  1402 , in a bank of two rows. The soldered aluminum wires  1402  are covered by strips of electrical tape. 
         [0065]    Referring to  FIG. 15  herein, there is illustrated another manufacturing stage for manufacture of a solar panel as described herein. Each of a plurality of solar wafers  1500  in a row are connected together with an aluminum strip electrical connector  1501 . The aluminum strip connector is covered with a strip of black electrically insulating and protective tape  1502 . 
         [0066]    Referring to  FIG. 16  herein, there is illustrated schematically an individual solar wafer, having first and second electrical conductors  1601 ,  1602 . 
         [0067]    Referring to  FIG. 17  herein, there is illustrated schematically the reverse side of the solar wafer shown in  FIG. 16 . 
         [0068]    Referring to  FIG. 18  herein, there is illustrated schematically a wiring diagram for connection of a plurality of individual solar roof panels in a solar roof tile installation. 
         [0069]    An array of individual solar roof panels  1800  are arranged in rows and columns on a roof. Each individual solar panel has a positive conductor and a negative conductor as shown in  FIGS. 5, 7 and 8  herein, with a diode on the positive conductor, so that when a negative conductor of a first solar panel is connected to a positive conductor of a second solar panel in a serial chain, there is a single one-way D.C. electrical path flowing through a chain of solar cells in series. The plurality of semi-conductor diodes ensure that current can flow in only one director through the chain of serially linked solar panels. 
         [0070]    In  FIG. 18 , there are shown individual chains of solar panels  1801  to  1815 . A respective positive terminal of each chain of solar panels are connected together to form a positive bus  1816 , and similarly, a respective negative terminal of each chain of solar panels are connected together to form a negative bus  1817 . The positive and negative buses supply current, via a direct current circuit breaker  1818 , to an AC inverter, which converts the direct current output of the solar cells into a single phase alternating current electrical output. There is provided a surge protector  1820  which connects to earth, so that in the event of a high voltage or current spike experienced on the negative buses, these are grounded to earth. This provides protection from current and/or voltage surges during for example an electrical storm. 
         [0071]    Conventional roof tile dimensions from different manufacturers vary. The height and width of the solar panel embodiments disclosed herein may be selected to match the size of roof tile. A minimum length and width of each panel is calculated to produce a minimum of 10 Watts each at peak sunlight, and is dependent on the available area of the roof tile. Most known roof tile areas will achieve this minimum power output. Larger sized roof tiles allow the solar cell area to be increased, achieving a greater power output. 
         [0072]    Each solar panel contains a diode on the positive circuit of its printed circuit board. Each solar tile is fitted to a roof using a known roofing method. The solar tiles are wired together in series to form a solar array. The solar array is connected through a combiner box and to an inverter. 
         [0073]    The output of the solar array is dependent on the D.C. voltage range demanded by the inverter. The voltage is controlled by limiting the number of solar tiles wired in series. Each series or row of solar tiles has two final contact wires which are combined together through a suitable fuse to a positive and negative bus bar to form a parallel circuit with one positive and one negative output. These outputs are wired to an inverter. 
         [0074]    Each solar cell within the solar panel is protected by an electrical diode within the series circuitry to minimize the effect of “shadowing” for example as the incident light on the solar cells vary due to cloud movements. If one solar cell is shadowed, its performance is reduced without affecting the performance of any adjacent solar cell. Similarly, if one solar panel is shaded by for example a tree, then its performance may be reduced compared to an adjacent solar panel which is in full sunlight. Due to the serial diodes, the shading of one solar cell does not affect the performance of adjacent solar cells. 
         [0075]    The embodiments disclosed herein can be fitted to new or replacement roofs. Any individual failed solar panel is easily replaceable by a new solar roof tile.