Method for manufacturing an encapsulation layer used to encapsulate photovoltaic cells in a photovoltaic module.

Abstract

The invention relates to a method for manufacturing an encapsulation layer used to encapsulate photovoltaic cells housed in a photovoltaic module. This method consists of: using a strip of encapsulation film, said strip extending along a plane; creating several parallel slits through said strip, along a first direction; and stretching the strip in its plane and along a second direction perpendicular to the first direction of the slits to create a lattice structure forming said encapsulation layer. Figure to be published with the abbreviation: Figure 2C

Description

Title of the invention: Method for manufacturing an encapsulation layer used to encapsulate photovoltaic cells of a photovoltaic module. Technical field of the invention

[0001] The present invention relates to a method for manufacturing an encapsulation layer used to encapsulate the photovoltaic cells of a photovoltaic module. The invention also relates to the encapsulation layer obtained by the method, as well as the photovoltaic module including such an encapsulation layer and the method for manufacturing this photovoltaic module. Prior art

[0002] Typically, a photovoltaic module takes the form of a panel composed of three main layers superimposed and fixed together: - A first layer, called the back layer (commonly called "backsheet"), forming a first protective element on the back face; - A second layer, called the intermediate layer; this intermediate layer includes the photovoltaic cells, the electrical connections between the cells and an encapsulation envelope arranged around the photovoltaic cells; - A third layer, called the front layer, forming a second protective element on the front face; this front layer is often made of glass or made of a transparent polymer to allow light rays to pass through;

[0003] The encapsulation envelope is classically composed of two layers of a polymer material, positioned on either side of the photovoltaic cells.

[0004] During a rolling operation, the two encapsulation layers melt to form, after the rolling operation, only one solidified assembly in which the photovoltaic cells are embedded.

[0005] Recently, for certain applications, the idea has emerged of creating particularly lightweight photovoltaic modules. In these applications, the requirements in terms of mechanical robustness and module reliability are reduced, and the encapsulation can be minimal in order to optimize the mass and cost of the final system. The idea is to integrate a minimum amount of material on the encapsulation side, while maintaining its operational functionality, at least for a certain period. For some applications, the photovoltaic module could even be single-use and considered disposable.

[0006] The aim of the invention is to propose a solution for creating a photovoltaic module encapsulation layer that is particularly lightweight, in order to ultimately obtain photovoltaic modules that are themselves lightweight, inexpensive and possibly single-use. Description of the invention

[0007] This objective is achieved by a method for manufacturing an encapsulation layer used to encapsulate photovoltaic cells housed in a photovoltaic module, this method consisting of: - Use a strip of encapsulation film, said strip extending along a plane, - Create several parallel slits across the said strip, following a first direction, - Stretch the strip in its plane and along a second direction perpendicular to the first direction of the slits to create a lattice structure forming said encapsulation layer.

[0008] According to an advantageous embodiment, the slots are created without material removal. As a result, manufacturing is simpler and limits material waste.

[0009] According to one particular feature, the slots are created along several parallel alignments to each other and to the first direction, each alignment comprising several slots, the alignments being separated from each other by a non-zero distance, along said second direction. This principle makes it possible to create the lattice.

[0010] According to another feature, the process consists of creating more than two alignments of slots, the distance separating two successive alignments being constant, forming a determined pitch.

[0011] According to another feature, the alignments of slots are arranged in a staggered pattern along the second direction.

[0012] According to another feature, the slots in the same alignment are identical.

[0013] According to another feature, the slots of all the alignments are identical.

[0014] According to another feature, the encapsulation film is made of a material of polymer type.

[0015] According to another feature, the polymer material is chosen from acid copolymers, ionomers, poly(ethylene-vinyl acetate), vinyl acetals, polyurethanes, polyvinyl chlorides, polyethylenes, polyolefin elastomer copolymers, α-olefin copolymers and α-,[3-ethylenic carboxylic acid esters, silicone elastomers and / or epoxy resins.

[0016] The invention also relates to an encapsulation layer used in a photovoltaic module, said encapsulation layer being intended to cover the photovoltaic cells of the photovoltaic module, this encapsulation layer being manufactured according to the process as defined above.

[0017] Advantageously, the resulting lattice structure has a square mesh.

[0018] The invention also relates to a photovoltaic module comprising a back layer, a front layer and an intermediate layer, arranged between the front layer and the back layer, the intermediate layer comprising interconnected photovoltaic cells and an encapsulation envelope, said encapsulation envelope being formed from at least one encapsulation layer as defined above.

[0019] According to one particular feature, each mesh of the lattice structure of the encapsulation layer defines a central hollowed area, at least one photovoltaic cell of the photovoltaic module being positioned opposite a hollowed area of ​​each mesh of the lattice structure.

[0020] Advantageously, said encapsulation envelope is formed from a first encapsulation layer and a second encapsulation layer, the first encapsulation layer and / or the second encapsulation layer being as defined above.

[0021] According to another feature, the lattice structure of the first encapsulation layer is offset along the second direction relative to the lattice structure of the second encapsulation layer.

[0022] According to another feature, the lattice structure of the first encapsulation layer has a mesh identical to that of the lattice structure of the second encapsulation layer.

[0023] The invention relates to a method for manufacturing a photovoltaic module as defined above, this method comprising: - A manufacturing step for the first encapsulation layer according to the process as defined above, - A hot rolling step of the assembly formed by the front layer, said first encapsulation layer, said second encapsulation layer and the back layer.

[0024] According to one particular feature, the second encapsulation layer is also manufactured according to the process as defined above. Brief description of the figures

[0025] Other features and advantages will become apparent in the detailed description that follows, given in relation to the accompanying drawings, in which: - Figures IA and IB schematically represent a photovoltaic module, respectively in perspective and side view; - Figures 2A to 2D illustrate the steps in the manufacturing process of the invention; - Figures 3A to 3C show different details of the lattice structure obtained by the manufacturing process of the invention; - Fig. 4 shows an architecture with two superimposed lattice structures, each obtained according to the manufacturing process of the invention; - Fig. 5 shows a lattice structure obtained according to the manufacturing process of the invention, affixed to the photovoltaic cells of a photovoltaic module;

[0026] Detailed description of at least one embodiment

[0027] In the following description, the front face of the photovoltaic module M corresponds to a face of the module receiving the light rays and the rear face corresponds to the face which is opposite to the front face.

[0028] The photovoltaic module M typically has a rectangular external shape, with a length and width in two dimensions and a thickness, small compared to its length and width, in a third dimension. In the following description, the length of the module is defined along an X direction and the width of the module is defined along a Y direction.

[0029] In the following description, the terms rear and front are therefore to be considered by taking an axis perpendicular to the surface of the module and oriented from its rear face to its front face.

[0030] With reference to [Fig.1A] and [Fig.1B], in a known manner, a photovoltaic module M comprises several superimposed and assembled layers: - A first layer, called the back layer 1 (commonly called "backsheet"), forming a first protective element on the rear face; this back layer is usually made of a polymer-type material with one or more layers; - A second layer, called intermediate layer 2, inserted between the back layer 1 and the front layer 3 (described below), allowing the assembly of one side of the back layer 1 and the other side of the front layer 3; this intermediate layer 2 includes the photovoltaic cells 20, the electrical connectors 22 and an encapsulation envelope 21 arranged around the photovoltaic cells; - The front layer 3, forming a second protective element on the front face; this front layer 3 is usually made of glass or a transparent polymer;

[0031] It should be noted that in the attached figures, the photovoltaic module M is shown upside down, so that its rear face is located above and the front face is located below.

[0032] For readability purposes in the attached figures IA and IB, the different layers of the module are not shown to scale. For example, the back layer 1 can have a thickness of a few hundred pm (for example between 100pm and 500pm, typically around 350pm), the intermediate layer 2 can have a thickness of up to 1mm and the front layer 3 can have a thickness ranging from 100pm to 4mm, depending on the type of material used (glass, PMMA or PC polymer...).

[0033] The back layer 1 can in particular provide a gas and water impermeability function, an electrical protection / insulation function and a mechanical protection function.

[0034] In the intermediate layer 2, the encapsulating layer 21 is conventionally made of a polymer forming a material to which the back layer 1 can adhere on one side and the front layer 3 on the other, allowing the three layers to be joined together. The three layers can be joined together by hot rolling, so that the back layer 1 and the front layer 3 adhere to the encapsulating layer material, thus forming a single-piece stack.

[0035] In the intermediate layer 2, the photovoltaic cells 20 are connected to each other in series / parallel, forming several strings of cells. Electrical connection elements 22, for example made of copper, provide the electrical connections between the cells 20 in each string.

[0036] The encapsulation envelope may have a thickness of between 25pm and 2000pm, preferably between 50pm and 500pm, preferably between 100pm and 400pm.

[0037] The photovoltaic module M may include a frame (not shown), for example made of aluminum, arranged around the periphery of the stack to stiffen the module M. For the implementation of the invention described below, this frame, as well as the electrical junction box (not shown) generally fixed to the rear face of the module M, are first removed. The method of the invention is in fact more specifically dedicated to the treatment of the layer stack of the photovoltaic module M.

[0038] By the term “encapsulating”, “encapsulated” or “encapsulation”, it should be understood that the plurality of photovoltaic cells is arranged in a volume, for example hermetically sealed against liquids, at least partly formed by at least two layers of encapsulation material(s), joined together after lamination to form the encapsulation envelope 21.

[0039] Indeed, initially, that is, before any lamination operation, the encapsulation casing 21 consists of at least two encapsulation layers, between which the plurality of photovoltaic cells is encapsulated. However, in a less reliable and lower-cost configuration, it would be possible to use a single encapsulation layer, present on only one side. The photovoltaic cells 20 thus become embedded in this single encapsulation layer during the lamination step. In the following description, an advantageous embodiment with two encapsulation layers is described.

[0040] During the layer lamination operation, the encapsulation layers melt to form, after the lamination operation, only one solidified layer (or set) in which the photovoltaic cells are embedded.

[0041] The film used to manufacture the encapsulation layer can be made from at least one polymer material selected from: acid copolymers, ionomers, poly(ethylene-vinyl acetate) (EVA), vinyl acetals, such as polyvinyl butyrals (PVB), polyurethanes, polyvinyl chlorides, polyethylenes, such as linear low-density polyethylenes, polyolefin elastomer copolymers, α-olefin copolymers and α-,[3-ethylenic carboxylic acid esters such as ethylene-methyl acrylate copolymers and ethylene-butyl acrylate copolymers, silicone elastomers and / or epoxy resins.

[0042] The invention relates primarily to an encapsulation layer present in a photovoltaic module and to a particular method for manufacturing this encapsulation layer. The invention can be applied to the single encapsulation layer if the photovoltaic module has only one, to one of the two encapsulation layers, or to both encapsulation layers of the photovoltaic module.

[0043] With reference to figures 2A to 2D, this process comprises the steps described below.

[0044] El- [Fig.2A]: We start with a strip 4 of material from an encapsulation film. This strip 4 has a width d smaller than the final width D of the encapsulation layer and a length L at least equal to the final length of the encapsulation layer. The length L of the strip defines a first direction X and the width d of the strip 4 defines a second direction Y, perpendicular to the first direction X.

[0045] E2 - [Fig.2B]: Slots 40 are made through the strip 4, advantageously without material removal. It can also be specified that: - The 40 slots are made in the length of the strip (along X); - The 40 slots are advantageously all identical; - Each slot 40 has a determined length; - The slots 40 are made along several alignments A juxtaposed along the width of the band 4 (according to Y); - Each alignment has at least two slots; - The alignments A are advantageously spaced at a constant non-zero pitch, in the direction of the width of the band 4; - From one alignment to the other, the 40 slots are arranged in a staggered pattern, that is to say, they are offset along the length of the strip; From one alignment to the other, the offset is advantageously chosen by half a step; - In each alignment, the slots 40 are spaced at a constant pitch, in the direction of the length of the strip 4;

[0046] E3 - [Fig.2C]: Once the slots 40 have been made, the strip is mechanically stretched by pulling it along the second direction Y. Thanks to the presence of the slots 40, a lattice structure T is thus formed, the mesh 400 of which is created by the stretching of each slot 40. The mechanical stretching of the strip is carried out until a sufficient width D is obtained, at least equal to that of the encapsulation layer (along Y) that is desired (and which must correspond at least to the final width of the photovoltaic module).

[0047] E4 - [Fig. 2D]: The resulting encapsulation layer thus takes the form of a T-shaped lattice. For example, with identical slits 40 and staggered alignments A of slits spaced at a constant pitch, the T-shaped lattice has a constant mesh size 400. After stretching, this mesh size 400 takes the form of a rhombus and possibly a square, as in [Fig. 2D], if the stretching is sufficient and appropriate. The square configuration has the dual advantage of distributing the material homogeneously in both the X and Y directions.

[0048] As indicated above, the layer obtained, after mechanical stretching of the initial film strip, can be used to form the single encapsulation layer of a photovoltaic module, or one and / or the other of the two encapsulation layers positioned on either side of the photovoltaic cells 20, before the lamination step.

[0049] To create a T-shaped truss according to the principle of the invention, several parameters must be chosen: The width d of the encapsulation film strip 4 initially used to obtain the desired final 400 mesh and obtain a final encapsulation layer of sufficient width D; The number n of meshes required to obtain the final width D of the encapsulation layer of the photovoltaic module; The length of each slot is 40; The constant step existing between two successive alignments A;

[0050] Figure 3A shows an example of the realization of a 400 square mesh, having the following parameters: a corresponds to the length of the side of the square mesh that we wish to obtain; a' corresponds to the length of the half-diagonal of the square mesh that we wish to obtain, in the direction of the length of the strip (along X); 1 corresponds to the length of half the diagonal of the square mesh that we wish to obtain, in the direction of the width of the strip (along Y); Bandwidth#:

[0051] In conjunction with [Fig. 3B], to determine the width d of the band 4 to be used initially, it is necessary to know the lightening factor F that is desired for the final encapsulation layer. This lightening factor F corresponds, for a final 400 mesh of square shape, to:

[0052]

[0053] - d " a In which: F corresponds to the desired relief factor; D corresponds to the desired final width of the encapsulation layer; d corresponds to the width of the encapsulation film strip 4 used initially, before stretching; a corresponds to the length of the side of the 400 square mesh that we want to obtain; a' corresponds to the length of the half-diagonal of the square mesh that we wish to obtain, in the direction of the length of the strip (along X);

[0054] As a reminder, with reference to [Fig.3A], for a square mesh, we have:

[0055] a2 = 212

[0056] In which: 1 corresponds to the length of half the diagonal of the square mesh that we wish to obtain, in the direction of the width of the strip;

[0057]

[0058] In a square mesh, we have: a=^ ela ' = l

[0059] For a square mesh, the lightening factor is therefore expressed as follows:

[0060]

[0061] Depending on the chosen lightening factor F, the initial width d required to obtain the encapsulation layer of width D having the shape of a T-shaped lattice with a 400 square mesh of side a can be deduced. The number of stitches#:

[0062] By choosing a square mesh, we have the following expression:

[0063] Dd = n*21

[0064] In which: n corresponds to the number of stitches we want to obtain; 1 corresponds to the length of half the diagonal of the mesh in the direction of the width of the band and therefore corresponds to the level of stretching that will be applied to the band;

[0065] And we can thus deduce:

[0066] , _ W 1 ~ 2n The length of each slit (figure 3C)#:

[0067] In connection with [Fig.3C], in the case of a square mesh, the length of each slit corresponds to twice the length of the side of the square mesh, i.e. to 2*a.

[0068] As indicated above, we have: a _

[0069] The step between two successive alignments ([Fig.3C]):

[0070] In conjunction with [Fig. 3C], this pitch corresponds to 2e and is a function of the total width D of the encapsulation layer obtained after stretching and the number n of meshes in the lattice T obtained. It is thus governed by the following relationship:

[0071]

[0072] In which: e corresponds to the constant step existing between two successive alignments; D corresponds to the width of the encapsulation layer; n corresponds to the total number of meshes in the lattice T;

[0073] In simplified terms, the encapsulation layer has been described with a T-lattice with a 400 square mesh. This architecture allows for a uniform distribution of material in both directions X, Y of the plane of the encapsulation layer after stretching.

[0074] However, the principle can be applied to any other mesh shape, rhombus, hexagon,... The demonstration can be generalized to any other mesh shape (rhombus or other) but in this case the material will be distributed according to a preferred direction, which can prove interesting if one wishes to reinforce the mechanical structure in the chosen direction. When arranging the encapsulation layer on the photovoltaic cells 20, the positioning of the meshes relative to the photovoltaic cells 20 can be done to leave a hollow area without encapsulating material and sufficient to perform a re-establishment of contact; this principle is illustrated by [Fig.5]; In the case where the final encapsulation layer needs to be continuous, the lamination recipe will be adjusted to allow for an extended material lamination time (typically an extended temperature hold); It should be noted that the front face of the photovoltaic module can be placed downwards, towards a flat and rigid heating plate of the laminator, which will promote the good distribution of the encapsulation layer on the surface, in order to form a single continuous layer; Once stretched, the T-lattice structure may tend to return to its initial position. Thermal relaxation of the stretched structure can be incorporated before rolling the final stack (thermal storage in the stretched position, or pre-rolling). The use of two superimposed meshes as described in [Fig.4] allows, with a constant quantity of material, for the material to be initially pre-distributed on a mesh twice as fine, which can facilitate the finishing of the encapsulant during the lamination step and allow a continuous layer to be obtained. In the latter case, two meshes with different appearances, textures, colors or visual patterns can be used to obtain a specific visual result after shaping and lamination (example aesthetic PV module, "semi-colored" module, or camouflage type pattern).

Claims

Demands

1. A method for manufacturing an encapsulation layer used to encapsulate photovoltaic cells housed in a photovoltaic module, said method consisting of: - Using a strip (4) of an encapsulation film, said strip (4) extending along a plane, - Creating several parallel slits (40) through said strip (4), along a first direction (X), - Stretching the strip (4) in its plane and along a second direction (Y) perpendicular to the first direction (X) of the slits to create a lattice structure (T) forming said encapsulation layer.

2. Method according to claim 1, characterized in that the slots (40) are created without material removal.

3. A method according to claim 1 or 2, characterized in that the slots (40) are created along several alignments (A) parallel to each other and to the first direction (X), each alignment (A) comprising several slots, the alignments being separated from each other by a non-zero distance, along said second direction (Y).

4. A method according to claim 3, characterized in that it consists of creating more than two alignments (A) of slots and in that the distance separating two successive alignments is constant, forming a determined pitch.

5. Method according to claim 4, characterized in that the slot alignments are arranged in a staggered pattern along the second direction (Y).

6. A method according to any one of claims 3 to 5, characterized in that the slots (40) of the same alignment are identical.

7. A method according to any one of claims 3 to 6, characterized in that the slots (40) of all alignments are identical.

8. A method according to any one of claims 1 to 7, characterized in that the encapsulation film is made of a polymer-type material.

9. A process according to claim 8, characterized in that the polymer material is selected from acid copolymers, ionomers, poly(ethylene-vinyl acetate), vinyl acetals, polyurethanes, polyvinyl chlorides, polyethylenes, polyolefin elastomer copolymers, a- copolymers olefins and α-,[3- ethylenic carboxylic acid esters, silicone elastomers and / or epoxy resins.

10. Encapsulation layer used in a photovoltaic module, said encapsulation layer being intended to cover the photovoltaic cells (20) of the photovoltaic module (M), characterized in that the encapsulation layer is manufactured according to the process as defined in any one of claims 1 to 9.

11. Encapsulation layer according to claim 10, characterized in that the resulting lattice structure (T) has a square mesh (400).

12. Photovoltaic module comprising a back layer, a front layer and an intermediate layer (2), arranged between the front layer and the back layer, the intermediate layer comprising interconnected photovoltaic cells (20) and an encapsulation envelope (21), said encapsulation envelope being formed from at least one encapsulation layer, characterized in that said at least one encapsulation layer is as defined in claim 10 or 11.

13. Photovoltaic module according to claim 12, characterized in that each mesh (400) of the lattice structure formed by said at least one encapsulation layer defines a central hollowed area and in that at least one photovoltaic cell (20) of the photovoltaic module is positioned opposite a hollowed area of ​​each mesh (400) of the lattice structure.

14. Photovoltaic module according to claim 12 or 13, characterized in that said encapsulation envelope is formed from a first encapsulation layer and a second encapsulation layer, and in that the first encapsulation layer and / or the second encapsulation layer is as defined in claim 10 or 11.

15. Module according to claim 14, characterized in that the lattice structure (T1) of the first encapsulation layer is offset along the second direction relative to the lattice structure (T2) of the second encapsulation layer.

16. Module according to claim 15, characterized in that the lattice structure (T1) of the first encapsulation layer has a mesh identical to that of the lattice structure (T2) of the second encapsulation layer.

17. A method for manufacturing a photovoltaic module as defined in any one of claims 14 to 16, characterized in that it comprises: - A manufacturing step of the first encapsulation layer according to the manufacturing process as defined in any one of claims 1 to 9, - A hot rolling step of the assembly formed by the front layer, said first encapsulation layer, said second encapsulation layer and the back layer.

18. A manufacturing process according to claim 17, characterized in that the second encapsulation layer is also manufactured according to the process as defined in any one of claims 1 to 9.

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