Lightweight and flexible photovoltaic module comprising a front layer consisting of a polymer and a rear layer consisting of a composite material

Abstract

The invention relates to a lightweight photovoltaic module (1) comprising: a transparent first layer (2) forming the front face, photovoltaic cells (4), an assembly (3) encapsulating the photovoltaic cells (4), and a second layer (5), the encapsulating assembly (3) and the photovoltaic cells (4) being arranged between the first (2) and the second (5) layer. The invention is characterised in that the first layer (2) comprises a polymer material and has a thickness (e2) of less than 50 μm, in that the second layer (5) comprises at least one composite material of the prepreg type containing polymer resin and fibres and has a areal weight of less than 150 g/m.sup.2, and in that the encapsulating assembly (3) has a maximum thickness (e3) of less than 150 μm.

Claims

1. A photovoltaic module, comprising: a first transparent layer forming a front face of the photovoltaic module, for receiving a luminous flux; a plurality of photovoltaic cells disposed side by side and electrically connected to each other; an encapsulant assembly encapsulating the plurality of photovoltaic cells, a second layer, wherein the encapsulant assembly and the plurality of photovoltaic cells is located between the first and second layers, and the first transparent layer comprises at least one polymeric material and has a thickness lower than 50 μm; and an additional layer forming a rear face of the photovoltaic module, the second layer being located between the additional layer and the encapsulant assembly, wherein the second layer comprises at least one polymeric resin and fibers based-pre-preg-type composite material having a weight per unit area lower than 150 g/m.sup.2, the encapsulant assembly has a maximum thickness lower than 150 μm, the additional layer consists of a same material as that making up the first layer forming the front face of the photovoltaic module, the additional layer has a thickness lower than or equal to that of the first layer, the second laver includes a plurality of holes, each hole is circular and formed under a center of a corresponding one of the photovoltaic cells, and a material of the first transparent layer and a material of the additional layer are each a fluoropolymer material.

2. The module according to claim 1, wherein said at least one pre-preg-type composite material has a polymeric resin impregnation rate between 30 and 70 mass %.

3. The module according to claim 1, wherein said at least one material composite of the second layer is a polymeric resin and fibers based pre-preg, the polymer being selected from polyester, epoxy, and/or acrylic, and the fibers being selected from glass, carbon, and/or aramid fibers.

4. The module according to claim 1, wherein the module has a weight per unit area lower than 1 kg/m.sup.2.

5. The module according to claim 1, wherein the encapsulant assembly has a maximum thickness between 20 μm and 100 μm.

6. The module according to claim 1, wherein the encapsulant assembly is formed by at least one layer comprising at least one polymer type encapsulation material selected from: acid copolymers, ionomers, poly(ethylene-vinyl acetate), vinyl acetals, polyvinylbutyrals, polyurethanes, polyvinyl chlorides, polyethylenes, low density linear polyethylenes, copolymer elastomer polyolefins, α-olefin and α,β-ethylenic carboxylic acid ester copolymers, ethylene-methyl acrylate copolymers, ethylene-butyl acrylate copolymers, silicone elastomers, and epoxy resins.

7. The module according to claim 1, wherein the photovoltaic cells are selected from: single crystal-based or multi crystalline-based homojunction or heterojunction photovoltaic cells, IBC-type photovoltaic cells, and photovoltaic cells comprising at least one material from amorphous silicon, microcrystalline silicon, cadmium telluride, copper-indium selenide and copper-indium/gallium diselenide.

8. The module according to claim 1, wherein the photovoltaic cells have a thickness between 1 and 300 μm.

9. The module according to claim 1, wherein the additional layer consists of the same material as that making up the first layer forming the front face of the photovoltaic module, the material being ethylene chlorotrifluoroethylene.

10. A method for making a photovoltaic module according to claim 1, the method comprising: hot laminating the constituent layers of the photovoltaic module, at a temperature between 130° C. and 170° C., for a time period of the lamination cycle of at least 10 minutes.

11. The method according to claim 10, further comprising laminating the constituent layers of the photovoltaic module between two anti-adhesive damping layers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention can be better understood upon reading the following detailed description, of examples of non-limiting implementation thereof, as well as upon examining schematic and partial figures, of the appended drawing, in which:

(2) FIG. 1 represents, in a cross-section view, a conventional example of photovoltaic module including crystalline photovoltaic cells,

(3) FIG. 1A represents an alternative embodiment of the example of FIG. 1 in which photovoltaic cells are of the IBC-type,

(4) FIG. 2 represents, in an exploded view, the photovoltaic module of FIG. 1,

(5) FIG. 3 illustrates, in a cross-section exploded view, an example of embodiment of a photovoltaic module in accordance with the invention,

(6) FIG. 4 illustrates, in a cross-section exploded view, a configuration of a photovoltaic module in accordance with the invention during a step of manufacturing the module,

(7) FIG. 5 illustrates, in a partial bottom view, an alternative embodiment of the second layer of a photovoltaic module in accordance with the invention, and

(8) FIG. 6 illustrates, in a cross-section exploded view, an alternative embodiment in accordance with the invention of the photovoltaic module of FIG. 3.

(9) Throughout these figures, identical references can refer to identical or analogous elements.

(10) Moreover, the different parts represented in the figures are not necessarily drawn to a uniform scale, to make figures more legible.

DETAILED DISCLOSURE OF PARTICULAR EMBODIMENTS

(11) FIGS. 1 and 2 have already been described in the part relating to the state of prior art.

(12) FIGS. 3 and 4 illustrate, in cross-section and exploded views, embodiments of photovoltaic modules 1 in accordance with the invention.

(13) It is here considered that the photovoltaic cells 4, interconnected by welded tinned copper strips, are “crystalline” cells, that is they include single crystal or multi-crystalline silicon, and that they have a thickness between 1 and 250 μm.

(14) Moreover, the encapsulant assembly 3 is selected to be made from two layers of ionomer between which the photovoltaic cells 4 are disposed, each layer having a thickness lower than 50 μm.

(15) Advantageously, the invention provides a specific choice for materials forming the front and rear faces of the photovoltaic module 1, so as to obtain an ultra-light photovoltaic module 1, with a weight per unit area lower than 1 kg/m.sup.2, and preferentially lower than 0.8 kg/m.sup.2, or even 0.6 kg/m.sup.2.

(16) Of course, these choices are in no way limitating.

(17) FIG. 3 is first referred to, which illustrates, in a cross-section exploded view, an example of embodiment of a photovoltaic module 1 in accordance with the invention.

(18) It is to be noted that FIG. 3 corresponds to an exploded view of the photovoltaic module 1 before the lamination step of the method according to the invention. Once the lamination step is performed, ensuring hot vacuum pressing, the different layers are in fact superimposed over each other.

(19) The photovoltaic module 1 thus includes a first layer 2 of a film of at least one polymeric material, with a thickness e2 lower than 50 μm, forming the front face of the photovoltaic module 1 and for receiving a luminous flux, a plurality of photovoltaic cells 4 disposed side by side and electrically connected to each other, and an assembly 3 encapsulating the plurality of photovoltaic cells 4.

(20) The polymeric material of the first layer 2 can be selected from: polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyamide (PA), a fluorinated polymer, especially polyvinyl fluoride (PVF) or polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene (ETFE), ethylene chlorotrifluoroethylene (ECTFE), polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE) and/or fluorinated ethylene propylene (FEP).

(21) Furthermore, whereas the rear face of a traditional photovoltaic module conventionally consists of a polymer multi-layer stack of the Tedlar®/polyethylene terephthalate (PET)/Tedlar® (or TPT) type with a thickness in the order of 300 μm, the photovoltaic module 1 includes a second layer 5 forming the rear face of the photovoltaic module 1, consisting of a polymer/continuous fibres pre-preg-type composite material with a total base weight lower than 150 g/m.sup.2. Moreover, the cloth weft of the pre-preg has a thickness lower than 50 μm, and the polymeric resin impregnation rate is between 30 and 70 mass %.

(22) The composite material of the second layer 5 can be a polymeric resin and fibres based pre-preg, the polymer being selected from polyester, epoxy and/or acrylic, and the fibres being selected from glass, carbon and/or aramid fibres.

(23) The second layer 5 can have a thickness e5 between 50 μm and 80 μm.

(24) Furthermore, the encapsulant assembly 3 has a total thickness e3 which is lower than 150 μm, and preferentially between 20 and 100 μm.

(25) The encapsulant assembly 3 can be made from at least one polymeric material selected from: acid copolymers, ionomers, poly(ethylene-vinyl acetate) (EVA), vinyl acetals, such as polyvinylbutyrals (PVB), polyurethanes, polyvinyl chlorides, polyethylenes, such as low density linear polyethylenes, copolymer elastomer polyolefins, α-olefin and α,β-ethylenic carboxylic acid ester copolymers, such as ethylene-methyl acrylate copolymers and ethylene-butyl acrylate copolymers, silicone elastomers and/or epoxy resins. It can especially be made from two polymer layers 3a and 3b, especially two poly(ethylene-vinyl acetate) (EVA) layers, between which the photovoltaic cells 4 are disposed. Each layer 3a, 3b can have a thickness e3a, e3b lower than 50 μm.

(26) Furthermore, the photovoltaic cells 4 can be selected from: single-crystal (c-Si) and/or multi-crystalline (mc-Si)-based homojunction or heterojunction photovoltaic cells, and/or IBC-type photovoltaic cells, and/or photovoltaic cells comprising at least one material from amorphous silicon (a-Si), microcrystalline silicon (μC-Si), cadmium telluride (CdTe), copper-indium selenide (CIS) and copper-indium/gallium diselenide (CIGS). Their thickness is between 1 and 300 μm, and especially between 1 and 200 μm.

(27) Making the photovoltaic module 1 is performed in a single step of hot laminating, at a temperature between 130° C. and 170° C., and especially in the order of 150° C., and for a time period of the lamination cycle of at least 10 minutes, and especially between 10 and 20 minutes, the constituent layers 2, 3, 4, 5 forming the stack of the photovoltaic module 1.

(28) However, given the small thickness of the encapsulant assembly 3, it is desirable to be able to laminate this stack between two anti-adhesive damping sheets; compatible with the hot lamination method; in order to avoid any breakage of the photovoltaic cells during the pressing step, this breakage being related to excessive thickness of copper strips on the photovoltaic cells 4.

(29) Thus, FIG. 4 represents a configuration analogous to that of FIG. 3 of a photovoltaic module 1 but with the presence of two anti-adhesive damping layers 8 on either side of the stack to avoid any breakage of the photovoltaic cells 4.

(30) Furthermore, FIG. 5 illustrates, in a partial bottom view, an alternative embodiment of the second layer 5 of a photovoltaic module 1 in accordance with the invention.

(31) This alternative illustrates the fact that the second layer 5, as a pre-preg, can be discontinuous so as to further decrease the weight per unit area related to this layer 5 while keeping the mechanical properties of the photovoltaic module 1.

(32) Thus, the second layer 5 includes stock removal parts forming holes 9 located at the photovoltaic cells 4. This stock removal is made under the photovoltaic cells 4, represented in dotted lines, which correspond to zones where mechanical strength is already ensured by these cells 4. In other words, the material of the pre-preg formed by the second layer 5 is removed under the cells 4 but kept between the cells 4 and on the edges of the layer 5.

Examples of Particular Embodiments

(33) Two examples of particular embodiments A and B of photovoltaic modules 1 in accordance to the invention will now be described.

(34) Both examples A and B have been made with the same encapsulation materials but with different photovoltaic cells: in the first example A, the photovoltaic cells 4 comprise 24 amorphous single-crystal silicon based heterojunction cells with a thickness in the order of 115 μm.

(35) In the second example B, the photovoltaic cells 4 comprise 30 IBC-type cells with a thickness in the order of 160 μm.

(36) Furthermore, for these two examples A and B, the constituent layers are the following ones: the first layer 2 forming the front face is an ECT 025 type ethylene chlorotrifluoroethylene (ECTFE) film from the Rayotec company, with a thickness in the order of 25 μm.

(37) The encapsulant layers 3a and 3b are films of ionomer obtained from the Jurasol series marketed by the Juraplast company, with a thickness in the order of 50 μm.

(38) The second layer 5 forming the rear face is a pre-preg composite film of the epoxy resin impregnated glass cloth type such as Hexply M77 from the Hexcel company.

(39) For each example A and B, the photovoltaic module is implemented in a single hot vacuum lamination step. During this step, it is desirable to properly cure the rear face formed by the second layer 5 in order to obtain desired mechanical properties. Thus, the hot lamination program has been optimised (temperature, pressure, time period, . . . ) in order to obtain sufficient curing of the composite material without any visual defect, nor breakage of the photovoltaic cells 4. This cross-linking is checked by measuring glass transition through Differential Scanning Calorimetry (DSC).

(40) Moreover, as previously described with reference to FIG. 4, in order to avoid breakage of the photovoltaic cells 4, the photovoltaic module 1 is laminated between two anti-adhesive damping sheets 8, with a thickness in the order of 0.50 mm.

(41) For both examples of embodiments A and B, photovoltaic modules 1 with a weight per unit area of less than 800 g/m.sup.2 and a light output of more than 180 W/m.sup.2 are advantageously obtained.

(42) Furthermore, advantageously, for these two embodiments A and B, electroluminescence imaging after implementation showed no degradation in the photovoltaic cells 4, even after flexure or bending of less than 50 cm, which thus confirmed the compatibility of the new materials used with a conventional hot lamination method for the manufacture of photovoltaic modules 1. The electrical performance of the photovoltaic modules 1 is identical, or even better, than its equivalents in the standard configuration by virtue of the better optical transparency of the materials used.

(43) In addition, accelerated ageing resistances in a thermal cycling chamber according to the terrestrial standard IEC 61215 have been demonstrated over more than 600 cycles.

(44) In addition, FIG. 6 shows an alternative embodiment in accordance with the invention to the photovoltaic module 1 of FIG. 3.

(45) This module in FIG. 6 can include all the characteristics described above, in particular those in connection with FIG. 3 to 5, which will therefore not be described again.

(46) However, in this example, the photovoltaic module 1 has an additional layer 10 forming the back side of the photovoltaic module 1, with the second layer 5 located between the additional layer 10 and the encapsulant assembly 3.

(47) This additional layer 10 is made of the same material as the first layer 2 forming the front side of the photovoltaic module 1. Advantageously, this material corresponds to ethylene chlorotrifluoroethylene (ECTFE), also known as Halar®.

(48) In addition, the additional layer 10 has a thickness which in this example in FIG. 6 is less than or equal to the thickness e2 of the first layer 2. The additional layer 10 advantageously provides an advantageous dielectric insulation to the module 1.

(49) Of course, the invention is not limited to the exemplary embodiments just described. Various modifications can be made thereto by those skilled in the art.