Abstract:
A flexible solar cell assembly having solar cells that are positioned within a sealed module chamber. A sealed wiring chamber is positioned on an end of the sealed module chamber and is interposed between the sealed module chamber and a junction box. Wiring interconnecting the junction box to the solar cells in the sealed module chamber are routed through the sealed wiring chamber to inhibit water entry into the sealed module chamber via the wiring.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation in part of U.S. application Ser. No. 12/685,540 filed Jan. 11, 2010, entitled RELIABLE THIN FILM PHOTOVOLTAIC MODULE STRUCTURES, which is hereby incorporated in its entirety by reference herein. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Inventions 
         [0003]    The aspects and advantages of the present inventions generally relate to apparatus and methods of photovoltaic or solar module design and fabrication and, more particularly, to roll-to-roll or continuous packaging techniques for flexible modules employing thin film solar cells. 
         [0004]    2. Description of the Related Art 
         [0005]    Solar cells are photovoltaic (PV) devices that convert sunlight directly into electrical energy. Solar cells can be based on crystalline silicon or thin films of various semiconductor materials, that are usually deposited on low-cost substrates, such as glass, plastic, or stainless steel. 
         [0006]    Thin film based photovoltaic cells, such as amorphous silicon, cadmium telluride, copper indium diselenide or copper indium gallium diselenide based solar cells, offer improved cost advantages by employing deposition techniques widely used in the thin film industry. Group IBIIIAVIA compound photovoltaic cells including copper indium gallium diselenide (CIGS) based solar cells have demonstrated the greatest potential for high performance, high efficiency, and low cost thin film PV products. 
         [0007]    As illustrated in  FIG. 1 , a conventional Group IBIIIAVIA compound solar cell  10  can be built on a substrate  11  that can be a sheet of glass, a sheet of metal, an insulating foil or web, or a conductive foil or web. A contact layer  12  such as a molybdenum (Mo) film is deposited on the substrate as the back electrode of the solar cell. An absorber thin film  14  including a material in the family of Cu(In,Ga)(S,Se) 2 , is formed on the conductive Mo film. The substrate  11  and the contact layer  12  form a base layer  13 . Although there are other methods, Cu(In,Ga)(S,Se) 2  type compound thin films are typically formed by a two-stage process where the components (components being Cu, In, Ga, Se and S) of the Cu(In,Ga)(S,Se) 2  material are first deposited onto the substrate or the contact layer formed on the substrate as an absorber precursor, and are then reacted with S and/or Se in a high temperature annealing process. 
         [0008]    After the absorber film  14  is formed, a transparent layer  15 , for example, a CdS film, a ZnO film or a CdS/ZnO film-stack is formed on the absorber film  14 . Light enters the solar cell  10  through the transparent layer  15  in the direction of the arrows  16 . The preferred electrical type of the absorber film is p-type, and the preferred electrical type of the transparent layer is n-type. However, an n-type absorber and a p-type window layer can also be formed. The above described conventional device structure is called a substrate-type structure. In the substrate-type structure light enters the device from the transparent layer side as shown in  FIG. 1 . A so called superstrate-type structure can also be formed by depositing a transparent conductive layer on a transparent superstrate such as glass or transparent polymeric foil, and then depositing the Cu(In,Ga)(S,Se) 2  absorber film, and finally forming an ohmic contact to the device by a conductive layer. In the superstrate-type structure light enters the device from the transparent superstrate side. 
         [0009]    In standard CIGS as well as Si and amorphous Si module technologies, the solar cells can be manufactured on flexible conductive substrates such as stainless steel foil substrates. Due to its flexibility, a stainless steel substrate allows low cost roll-to-roll solar cell manufacturing techniques. In such solar cells built on conductive substrates, the transparent layer and the conductive substrate form the opposite poles of the solar cells. Multiple solar cells can be electrically interconnected by stringing or shingling methods that establish electrical connection between the opposite poles of the solar cells. Such interconnected solar cells are then packaged in protective packages to form solar modules or panels. Many modules can also be combined to form large solar panels. The solar modules are constructed using various packaging materials to mechanically support and protect the solar cells contained in the packaging against mechanical damage. Each module typically includes multiple solar cells which are electrically connected to one another using the above mentioned stringing or shingling interconnection methods. 
         [0010]    In standard silicon, CIGS and amorphous silicon cells that are fabricated on conductive substrates such as aluminum or stainless steel foils, the solar cells are not deposited or formed on the protective sheet. Such solar cells are separately manufactured, and the manufactured solar cells are electrically interconnected by a stringing or shingling process to form solar cell circuits. In the stringing or shingling process, the (+) terminal of one cell is typically electrically connected to the (−) terminal of the adjacent solar cell. For the Group IBIIIAVIA compound solar cell shown in  FIG. 1 , if the substrate  11  is a conductive material such as a metallic foil, the substrate, which forms the bottom contact of the cell, becomes the (+) terminal of the solar cell. The metallic grid (not shown) deposited on the transparent layer  15  is the top contact of the device and becomes the (−) terminal of the cell. When interconnected by a shingling process, individual solar cells are placed in a staggered manner so that a bottom surface of one cell, i.e. the (+) terminal, makes direct physical and electrical contact to a top surface, i.e. the (−) terminal, of an adjacent cell. Therefore, there is no gap between two shingled cells. Stringing is typically done by placing the cells side by side with a small gap between them and using conductive wires or ribbons that connect the (+) terminal of one cell to the (−) terminal of an adjacent cell. Solar cell strings obtained by stringing or shingling individual solar cells are interconnected to form circuits. Circuits may then be packaged in protective packages to form modules. Each module typically includes a plurality of strings of solar cells which are electrically connected to one another. 
         [0011]    Generally, the most common packaging technology involves lamination of circuits in transparent encapsulants. In a lamination process, in general, the electrically interconnected solar cells are covered with a transparent and flexible encapsulant layer. A variety of materials are used as encapsulants, for packaging solar cell modules, such as ethylene vinyl acetate copolymer (EVA), thermoplastic polyurethanes (TPU), and silicones. However, in general, such encapsulant materials are moisture permeable; therefore, they must be further sealed from the environment by a protective shell, which provides resistance to moisture transmission into the module package. 
         [0012]    The nature of the protective shell determines the amount of water that can enter the package. The protective shell includes a front protective sheet through which light enters the module and a back protective sheet and optionally an edge sealant that is at the periphery of the module structure. The top protective sheet is typically transparent glass which is water impermeable. The back protective sheet may be a sheet of glass or a polymeric sheet of TEDLAR® (a product of DuPont) and polyeyhylene teraphthalate (PET). The back protective polymeric sheet may or may not have a moisture barrier layer in its structure such as a metallic film like an aluminum film. The edge sealant is a moisture barrier material that may be in the form of a viscous fluid which may be dispensed from a nozzle to the peripheral edge of the module structure or it may be in the form of a tape which may be applied to the peripheral edge of the module structure. 
         [0013]    A junction-box is typically attached on the exposed surface of the back protective sheet, right below the interconnected solar cells, using moisture barrier adhesives. Terminals of the interconnected solar cells are typically connected to the junction box through holes formed in the back protective sheet. In this way, the size of the module can be reduced as the frame holding the cells can be positioned very close to the solar cells. The holes in the back protective sheet must be very carefully sealed against moisture leakages using, for example, potting materials such as silicone, epoxy, butyl, and urethane containing materials. If the seal in the holes fails, such holes allow moisture to enter the module and can cause device failures. 
         [0014]    Thin film solar cells are more moisture sensitive than the crystalline Si devices; therefore, materials with moisture barrier characteristics need to be used in the module structure and any potential moisture sources such as holes in the back and front protective sheets are problematic. For a flexible module to last 25 years, all the packaging components are also required to preserve mechanical, thermal, and chemical stability at the outdoors. The front protective sheet for thin film devices can be either glass or a flexible sheet depending on the product design requirements. A flexible front sheet can be composed of a combination of one or more weatherable films, such as fluoropolymers, for example, ETFE (ethylene-tetrafluoroethylene) or FEP (fluoro ethylene propylene) or polyvinylidene fluoride (PVDF) and a transparent inorganic moisture barrier layer such as Al 2 O 3  or SiO 2 . In one product, a weatherable film (ETFE, FEP or PVDF) can be laminated onto one or more inorganic moisture barrier layers to form a front protective sheet. However, during the lamination, stresses resulting from UV exposure, temperature cycle and humidity can deteriorate the front protective sheet which can result in severe inorganic moisture barrier-layer delaminations from the weatherable films. One can alleviate these problems by first incorporating the inorganic barrier layers onto a carrier film like poly(ethylene teraphthalate) PET and poly(ethylene naphthalate) PEN and then applying the weatherable film onto the carrier film instead of the barrier layer. Such carrier polymers are thermally and mechanically more stable. Although PET and PEN films are not as weatherable as the ETFE and FEP films, any temperature cycling on the solar panel would not impose as much stress as it would on a fluoropolymer like ETFE, FEP. 
         [0015]    Weatherable films can also be incorporated into the moisture barrier layer-carrier film combinations using various adhesives. The adhesion of the weatherable film to the adhesives and adhesives to the moisture barrier layer-carrier film becomes very critical. As mentioned above, fluoropolymers are known to be very difficult to adhere to. For a target 25 years of life time, one would need a very strong adhesion among the layers of weatherable film-adhesive-moisture barrier layer-carrier film. If the adhesion is weak on one of the interfaces, the reliability of the whole product will be in question as any delamination can continue to propagate. 
         [0016]    The weakness of the adhesion among the layers of the front protective sheet can also be problematic for junction box adhesion to the front protective sheet. Junction boxes conventionally have been attached to back side of the modules and on the back protective sheet, which is made of glass or TEDLAR due to the restrictions on the type of rigid solar panel installations. For a flexible module, there are implementations where the junction boxes should be attached on the front, especially when the modules are required to be incorporated on to the roof top membranes. However, once the junction box is placed on the front surface of a flexible module, there are adhesion issues with the ETFE and FEP fluoropolymers as explained above, and extra processes step (performed at additional cost) may be needed to improve adhesion between the top of the weatherable film and the junction box sealant or tape. Further, the weaker adhering front sheet layers are more likely to delaminate where the junction box is placed due to stress mismatches between the solar panel and the junction box. The delamination of one of the front sheet layers around the junction box area can create safety hazards as water can penetrate through the delaminated areas and touch live wires inside the junction box. 
         [0017]    As the brief discussion above demonstrates, there is a need to develop new module structures, especially for thin film solar cells, to eliminate aforementioned problems while minimizing moisture permeability. 
       SUMMARY 
       [0018]    The aspects and advantages of the present inventions generally relate to apparatus and methods of flexible photovoltaic or solar module and panel design and fabrication. The aforementioned needs are satisfied by one embodiment of the invention that comprises a flexible solar power apparatus, comprising a flexible bottom sheet of a first material having a front surface and a back surface, the flexible bottom sheet including a first portion including a first front surface region and a second portion including a second front surface region. This apparatus further comprises at least one sealed module chamber, including a solar cell circuit with interconnected solar cells, formed over the first front surface region of the first portion, and a sealed wire chamber formed over the second front surface region, wherein a peripheral edge seal wall applied along the periphery of the flexible bottom sheet seals the outer edges of both the at least one sealed module chamber by a first portion of the peripheral edge seal wall and also the sealed wire chamber by a second portion of the peripheral edge seal wall, wherein an inner seal wall separates the sealed module chamber and the sealed wire chamber; and wherein a first flexible top sheet of a second material disposed on the first portion of the peripheral edge seal wall and the inner seal wall thereby enclosing a light receiving side of the at least one sealed module chamber, and wherein a second flexible top sheet of the first material is disposed on the second portion of the peripheral edge seal wall and the inner seal wall thereby enclosing the sealed wire chamber. This embodiment comprises a junction-box formed over the second flexible top sheet of the sealed wire chamber, wherein terminal wires of the solar cell circuit are extended from the at least one sealed module to the junction box through the sealed wire chamber. 
         [0019]    In another embodiment, the present invention comprises a flexible solar panel, comprising a bottom protective sheet of a first material and a front protective sheet placed over the bottom protective sheet, the front protective sheet including a first section of a first material and a second section of a second material placed adjacent to the first section along an interface, wherein the first material is a transparent material and wherein the moisture resistance of the second material is greater than the first material. In this embodiment, the invention further comprises an edge moisture sealant wall formed between the bottom protective sheet and the front protective sheet along the perimeters of the bottom and the front protective sheet, thereby sealing the perimeters of the bottom protective sheet and the front protective sheet against moisture. In this embodiment, the invention further comprises an inner moisture sealant wall formed between the front protective sheet and the bottom protective sheet and along the interface and between the first section and the second section of the front protective sheet, thereby forming a sealed module chamber under the first section and a sealed wire chamber under the second section. In this embodiment, the invention further comprises a junction box is attached to the wire chamber to connect the flexible solar panel to a power circuitry; wherein a solar cell circuit including a plurality of interconnect solar cells is disposed in the sealed module chamber, and terminal wires of the solar cell circuit is extended from the sealed module chamber to the junction box through the sealed wire chamber. 
         [0020]    In another embodiment, the invention comprises a flexible solar panel comprising a sealed module chamber having a first surface and a second surface, wherein the first surface is transparent to permit light to enter the sealed module chamber and wherein the sealed module chamber defines a first and a second end having end walls. In this embodiment, the invention further comprises a plurality of solar cells positioned within the sealed module chamber wherein the plurality of solar cells has at least one wire that transmits energy from the plurality of solar cells to an external recipient of the energy. In this embodiment, the invention comprises a sealed wiring chamber having outer surfaces that is attached adjacent to a first end of the sealed module chamber so that an end wall of the sealed module chamber defines an inner seal wall and wherein the at least one wire extends through the sealed wiring chamber. In this embodiment, the invention further comprises a junction box that is attached to one of the outer surfaces of the sealed wiring chamber, wherein the junction box receives the at least one wire from the sealed wiring chamber and permits electrical interconnection between the at least one wire and the external recipient of energy. 
         [0021]    These and other objects and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a schematic view a thin film solar cell; 
           [0023]      FIG. 2A  is a schematic cross sectional view of a flexible thin film solar panel; 
           [0024]      FIG. 2B  is a schematic cross sectional view of the flexible solar panel shown in  FIG. 2A ; 
           [0025]      FIGS. 3-4  are schematic views of various embodiments of the auxiliary unit and the junction box of the flexible panel; and 
           [0026]      FIGS. 5-6  are schematic views of various alternative embodiments of a flexible solar panel. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    The preferred embodiments described herein provide methods of manufacturing flexible photovoltaic power apparatus or solar panel including one more flexible solar modules employing interconnected thin film solar cells, preferably Group IBIIIAVIA compound solar cells. The photovoltaic power apparatus or solar panel preferably includes a sealed module chamber with a first top protective sheet and a sealed wire chamber with a second top protective sheet. A connection box or a junction box through which the apparatus is connected to a power circuitry may be attached to the sealed wire chamber so that the terminal wires of the interconnected solar cells are extended from the sealed module chamber to the junction box through the sealed wire chamber. 
         [0028]    The first top protective sheet is a transparent light receiving top protective sheet. The second top protective sheet is different from the first top protective sheet of the sealed module chamber. The second top protective sheet may be a high moisture resistive material and may not be transparent to visible light. The first and second top protective sheets form the front side of the solar panel, which may be manufactures as a single piece with the first and second top protective sheet portions or by attaching the second protective sheet to the first top protective sheet using various bonding and sealing methods. 
         [0029]    The chambers may be formed side by side and separated from one another by a common sealant wall or abutted individual sealant walls belonging to the chambers. Both chambers may be formed on the same back protective sheet or different back protective sheets. In either case, the first and second top protective sheets form the front side of the solar panel. In the preferred embodiment, the second top protective sheet covering the wire chamber includes the same material as the back protective sheet and the junction box is placed on the wire chamber by attaching it to the second top protective sheet As described above in the background, in rigid and flexible module structures employing thin film solar cells, it is important to minimize moisture permeability of the module structure while assuring that the structure passes the electrical safety tests necessary for safe operation in the field. In one embodiment, the current invention is related to a method for a flexible module design where the junction box is on the front side of a solar module and is attached to a back sheet material that is not as hard to adhere as the weatherable ETFE, FEP films. In another embodiment, the current invention also provides unique dielectric materials and lay-up structure to inhibit any electrical wet leakage failures. Both advantages bring the improved reliability and safety for the flexible solar panel to enhance its ability to last at least 25 years. 
         [0030]    Reference will now be made to the drawings wherein like numerals refer to like parts throughout.  FIG. 2A  shows in plan view an embodiment of a flexible solar panel  100  of the present invention. 
         [0031]    The flexible solar panel may comprise a module  102  having a module housing  102 A, a flexible auxiliary unit  104  including a auxiliary unit housing  104 A and a junction-box  106  or connection housing attached to the auxiliary unit  104 . A solar power generating solar cell circuit  108  is held in the module housing  102 A. As will be explained more fully below, terminal leads  109  of a solar cell circuit  108  is extended from the module  102  to the junction box  106  through the auxiliary unit  104  in a well sealed manner while inhibiting any moisture seepage into the module housing. In this configuration, the auxiliary unit  104  forms a buffer zone between the module  102  and the junction box  106 , which additionally seals the terminal leads  109  exiting the module  102  and entering junction box. Although in this embodiment the flexible solar panel  100  is exemplified with the module  102 , the auxiliary unit  104  and the junction box  106 ; the flexible solar panel  100  of the present invention may have multiple modules with a single auxiliary unit or multiple auxiliary units as well as single or multiple junction boxes. 
         [0032]    As shown in  FIG. 2A  in top view and in  FIG. 2B  in cross sectional side view, the flexible solar module has a flexible outer shell  100 A that may be made of a bottom flexible protective sheet  112 , a top flexible protective sheet  114 , and a peripheral sealant wall  116  extending between the bottom and top flexible protective sheets and applied along the perimeter of them. An inner seal wall  118  divides the interior space of the shell into two, as the module housing and the auxiliary unit housing in which the components of the respective housings are placed. The peripheral sealant wall  116  may be made of a viscous moisture barrier sealant or a moisture barrier sealant tape. An exemplary material for the peripheral sealant and the inner seal walls may be butyl rubber with desiccants having 5 to 13 mm width and 0.5 mm to 1.5 mm thickness. 
         [0033]    The solar cell circuit  108  includes a number of solar cells  110  interconnected using a stringing technique that employs conductive leads  120 , such as conductive wires or ribbons, to electrically connect the solar cells, preferably in series. However, the solar cell circuit  108  may also be formed using shingling techniques to interconnect the solar cells  110  without using conductive leads, such shingling principles are described above in the background section. Each solar cell  110  generally includes a substrate  110 A, an absorber layer  110 B formed over the substrate and a transparent layer  110 C formed over the absorber layer  110 B. The absorber layer  110 B may be a Group IBIIIAVIA absorber layer such as a Cu(In, Ga) Se 2  compound layer. The substrate  110 A may be a flexible foil substrate such as a stainless steel foil or an aluminum foil. There may be a back contact layer (not shown), such as a molybdenum layer between the substrate and the absorber layer. A current collecting structure (not shown) including a busbars and fingers is deposited onto a top surface of the transparent layer  110 C, which is also the light receiving side of the solar cells. A support material  122  or encapsulant, such as ethylene vinyl acetate (EVA) and/or thermoplastic polyurethane (TPU), and thermoplastic polyolefins, fills the space surrounding the solar cell circuit  108  in the module housing. The support material  122  is a transparent material which fills any hollow space among the cells and tightly seals them into a module structure by covering their surfaces. The conductive leads  120  are connected to the solar cell strings using methods which are well known in the solar cell manufacturing technologies. 
         [0034]    In this embodiment, the top flexible protective sheet  114  may comprise a first section  114 A including a first material and a second section  114 B including a second material. As shown in  FIGS. 2A and 2B , the first section  114 A of the top protective sheet forms top of the module  102  and the second section  114 B forms top of the auxiliary unit  104 . An intersection  115  separating the first and second sections  114 A,  114 B are placed adjacent top of the inner seal  118  between the module housing  102 A and the auxiliary unit housing  104 A. The junction box  106 , preferably a junction box enclosure  107 , is preferably attached to a top surface  113  of the second section  114 B of the top flexible protective sheet  114  covering the auxiliary unit housing  104 A. The first material of the first section  114 A may be different from the second material of the second section  114 B, or at least the material of the top surface  113  of the second section, of the top flexible protective sheet  114  of the flexible solar panel  100 . The first and the second materials may be sheet materials including single or multiple material layers. As will be described more fully below, the second material of the second section  114 B may be the same as the material of the bottom protective sheet  112  or another material having a top surface that is more compatible with the sealants or adhesives used to attach the junction box to the second section surface. The first section  114 A and the second section  114 B may be separate pieces that brought together and sealed along the interface  115 . Alternatively, the first and the second sections may be integrated and manufactured together as a single top flexible protective sheet. Of course, the second section may also include the material of the first section. In this particular case, an inner surface of the second section (the surface facing towards the auxiliary unit housing) may preferably be treated with a moisture sealant layer. 
         [0035]    In modules employing thin film devices, such as thin film CIGS solar cells, it is important that the bottom protective sheets be a moisture barrier. The bottom flexible protective sheet  112  of the flexible solar panel  100  may typically be a polymeric sheet having moisture barrier characteristics such as TEDLAR®, a polyvinyl fluoride PVF film available from DuPont, Inc., or other polymeric sheet materials such as PVDF (Poly vinyledene difluoride), PET (poly ethylene teraphtalate), Perfluoro-alkyl vinyl ether, PA (polyamide) or PMMA (poly methyl methacrylate). The flexible bottom protective sheet  112  may be non-transparent sheet and may preferably comprise a composite structure, i.e., multiple layers stacked and bonded, including one or more metallic layers such as aluminum layers between the polymeric sheets to further improve moisture resistance of the bottom flexible protective sheet. The metallic layer, or moisture barrier, may be interposed between polymeric sheets such as TEDLAR® layers or other polymeric material layers so that the polymeric sheet forms the outer surface exposed to outside. For example, when a 18 to 50 um thick aluminum (Al) sheet is laminated into the structure of such TEDLAR sheets, very low water vapor transmission rates of 10 −3  g/m 2 /day or lower can be achieved. In addition to its high moisture barrier property, TEDLAR exhibits good adhesion to the sealants used to adhere junction box or other module components to TEDLAR surfaces. TEDLAR forms moisture resistant seals with such a sealant used to attach junction boxes  107  to TEDLAR surfaces. An exemplary flexible bottom protective sheet may include the structure of a top TEDLAR layer/Aluminum layer/PET layer/Primer and may have a thickness of about 0.4 mm. When the same material is used for the second section  114 B of the top flexible protective sheet  114 , the auxiliary unit  104  becomes more moisture resistant and moisture transmission through the path ways of terminal wires  109  is reduced. 
         [0036]    Thus, the second section  114 B of the top flexible protective sheet may be made of any polymeric sheet or polymeric-metal sheet combinations. The top surface  113  of the second section may be a polymeric back sheet material such as TEDLAR, PVDF, PET, Perfluoro-alkyl vinyl ether, PA or PMMA. The junction box  106  on the solar module can be located on the second section  114 B of the top flexible protective sheet  114  as shown in  FIGS. 2A and 2B  and attached to the polymeric materials on the top surface  113 . It is easier to adhere the junction box to this material than the weatherable ETFE, FEP films that are mentioned in the background section. The flexible bottom protective sheet  112  as well as the second section  114 B of the flexible top protective sheet  114  may at least include an outer polymeric layer, such as TEDLAR, covering a non-transparent inorganic moisture barrier layer such as a metallic layer, for example Al. The junction box enclosure  107  may be made of Noryl, PPE (poly phenylene ether), PET, Nylon, Polycarbonate, or PPE with PS (poly styrene) materials. Exemplary adhesive that can be used to attach the junction box to the top surface  113  of the second section  114 B may be silicone sealants such as Dow Corning PV804, Shinetsu KE220/CX220, Tonsan 15276 or adhesive tapes like 3M VHB 5952, Duplomont 9182. The adhesive tapes may need a primer to apply them to the surface materials. 
         [0037]    Exemplary flexible and transparent materials for the first section  114 A of the top flexible protective sheet may include ethylene tetrafluoroethylene (ETFE) under TEFZEL® commercial name or fluorinated ethylene propylene (FEP) from DuPont or poly vinylidene fluoride (PVDF) under KYNAR commercial name. The first section  114 A may at least include an outer polymeric layer, such as ETFE, FEP or PVDF, covering a transparent inorganic moisture barrier layer such as Al 2 O 3  or SiO 2 . As explained above, although such materials are very weather-resistant materials, they have weaker adhesion to the junction box sealants (Silicone based one or two component systems, with room temperature cure chemistry) and VHB type tapes used to attach junction box to the modules, and the lack of any inorganic moisture barrier layer or foil make them more vulnerable against the moisture. The moisture transmission rate of an ETFE or FEP front sheet is around 1 to 10 g/m 2 /day. An exemplary first section of the top protective sheet may include the structure of a top FEP, ETFE or PVDF layer/Adhesive film/Moisture barrier-Carrier film and may have a thickness in the range of 0.1 to 0.15 mm. As described in the background section, the carrier film may include PET poly(ethylene teraphthalate) and PEN poly(ethylene naphthalate). An exemplary transparent moisture barrier material may include Al 2 O 3  or SiO 2 . 
         [0038]      FIGS. 3 and 4  schematically illustrate various manners in which the auxiliary unit  104  and the junction box  106  of the flexible solar panel shown in  FIGS. 2A and 2B  are constructed. 
         [0039]    In the embodiment shown in  FIG. 3 , the terminal wires  109  pass through the inner seal wall  118  and enters the auxiliary unit housing  104 A, and then through openings  124  in the second section  114 B of the top flexible protective sheet  114 , connected to terminals  126  in the junction box  106 . To reduce any moisture leakage in the auxiliary housing, a seal material  128  may be used to seal the holes  124 . As described above, the junction box enclosure  107  is sealably attached to the top surface  113  of the second section  114 B, which further encloses the openings  124 . The portion of the terminal wires  109  extending from the inner seal wall  118  may be coated with a protective shield  130  made of a high dielectric strength and moisture resistant material. One end of the protective shield may be embedded into the inner seal wall  118 , and the other end may extend into the junction box  106 . The protective shield  130  may be formed and applied as a shrink tube and may be placed through the opening  128  in a tightly fitting manner to further minimize any moisture leakage inside the auxiliary housing  104 A. Exemplary materials for the protective shield  130  may be the following materials: polyethylene terephthalate (PET), which is available under the commercial names Mylar, Melinex, heat shrink Mylar; polyimide (Kapton); polyolefins (EPS 300); and polyethylene napthalate (PEN). 
         [0040]    As shown in  FIG. 3  the intersection  115  between the first and second sections  114 A,  114 B may be located over the inner seal wall  118 . However there may be other insulating and moisture resistant layers between top of the inner seal wall  118  and the intersection  115  if the first and second sections made of separate pieces. 
         [0041]    As shown in  FIG. 4 , an insulating film  132 , used with the inner seal wall  118 , mechanically and electrically supports the second section  114 B, when the top flexible protective sheet  114  is comprised of two different pieces and when only the edge of the first section  114 A is placed on the inner seal wall  118 . The insulating film  132  may include a high dielectric PET layer and adhesives on both sides to improve adhesion to the materials in contact. The dielectric constant of PET is equal or greater than 11 kV/mil and it preserves its electrical properties even with moisture penetration. There will be a potential difference between the live wires and the water that penetrates through the intersection  115  during a rainy season. This potential difference can be up to 1000 V DC. The material used as the insulating film  132  must be tested against partial discharge tests as not every material can withstand the 1000 V partial discharge tests without compromising its insulating electrical properties. EPE film from Madico Inc. of Woburn, Mass. is one of these materials that is available commercially. PET thickness may vary from 2 mil to 5 mil and adhesive thickness may be 2 to 4 mil on both sides. In this configuration, the insulating film  132  prevents any water leakage and electrical leakage through the intersection  115 . The intersection  115  may open up and widen during installation or due to temperature cycling on the field, and rubbery edge seal under the intersection  115  may break apart exposing the live wires to the water and moisture penetration. With the high dielectric strength insulating film  132  in place, there will be no electrical leakage from wires to the water and moisture penetrated through openings. The insulating film  132  also provides mechanical support for the junction box pocket as the intersection  115  is weak for any bending stress. 
         [0042]      FIGS. 5 and 6  illustrate alternative locations for the junction box. As shown in  FIG. 5 , in a flexible solar panel  200  comprising a module  202 , auxiliary unit  204  and a junction box  206 , the junction box  206  may be attached to a side of the auxiliary unit. The solar panel  200  includes: a flexible top protective sheet  214  including a first section  214 A which is transparent, and a second section  214 B; and a flexible bottom protective sheet  212 . In this embodiment, the junction box is attached to the outer surfaces of flexible bottom protective sheet  212  and the second section  214 B of the flexible top protective sheet that may include the same material, as described in the above embodiments. As shown in  FIG. 6 , in a flexible solar panel  300  comprising a module  302 , auxiliary unit  304  and a junction box  306 , the junction box  306  may be attached to the bottom of the auxiliary unit  304 . The solar panel  300  includes: a flexible top protective sheet  314  including a first section  314 A, which is transparent, and a second section  314 B; and a flexible bottom protective sheet  312 . In this embodiment, the junction box  306  is attached to the outer surface of flexible bottom protective sheet  312 . 
         [0043]    Although aspects and advantages of the present inventions are described herein with respect to certain preferred embodiments, modifications of the preferred embodiments will be apparent to those skilled in the art. The scope of the present invention should not be limited to the foregoing discussion but should be defined by the appended claims.