Method for manufacturing a photovoltaic module comprising a ferromagnetic element.

Abstract

Method for manufacturing a photovoltaic module comprising a ferromagnetic element. The invention relates to a method for manufacturing a photovoltaic module, comprising the following steps: a) placing a multilayer stack (1) between a mold (2) and a counter-mold (3), the multilayer stack comprising a ferromagnetic element (8, 13) and as components to be bonded: - at least two electrically insulating encapsulation sheets (4) comprising at least one polymer, - at least one photoelectric generator, preferably a photovoltaic cell (5), sandwiched between the encapsulation sheets, b) thermocompression of the multilayer stack comprising the following substeps: b1) application by the mold and the counter-mold of pressure against the multilayer stack, and,b2) heating the multilayer stack to a suitable temperature to bond the components of the multilayer stack together to form the photovoltaic module, the heating being carried out by electromagnetic induction by applying a magnetic field to at least the ferromagnetic element. Figure for the abbreviation: Fig. 1,

Description

Title of the invention: Method for manufacturing a photovoltaic module comprising a ferromagnetic element. Technical field

[0001] The present invention relates to the field of manufacturing a photovoltaic module and more particularly to a module of complex three-dimensional shape, in particular curved. Previous technique

[0002] In order to best preserve the undeveloped natural space, it is necessary, in order to deploy a large number of photovoltaic modules, to integrate them into existing surfaces, for example buildings, infrastructure, consumer goods and in the field of mobility (vehicles).

[0003] However, these integrations require that the shape and mass of the photovoltaic modules be adapted to the support intended to hold them. Furthermore, for each photovoltaic module, it is necessary to guarantee performance and durability that comply with current regulations and to reduce the corresponding environmental footprint in order to meet the "net zero carbon" objective by 2035.

[0004] Known photovoltaic modules generally comprise several photoelectric generators, preferably photovoltaic cells, capable of converting a light flux into an electric current, which are encapsulated in a laminate.

[0005] The laminate typically comprises: - a front face intended to be positioned facing the solar radiation incident on the photovoltaic cells and which is defined by a plate of thermally or chemically tempered glass, with a thickness greater than 0.1 mm, generally between 2 mm and 6 mm, - a multilayer back face, generally containing polyvinyl fluoride, for example marketed under the name TEDLAR©, - photovoltaic cells coated by two adhesion films, called encapsulation films, generally made of ethylene-vinyl acetate, arranged between the front and rear faces.

[0006] The photovoltaic module may further comprise an aluminum frame, which supports the laminate and a junction box that allows for the integration of bypass diode or MOSFET protection or an electronic circuit. The junction box also allows for the electrical connection of several photovoltaic modules together.

[0007] The implementation of a thick tempered glass front panel is however not compatible with applications where the lightness of the photovoltaic module is required.

[0008] To lighten the laminate, it may be considered to thin the tempered glass plate to a thickness of less than 2 mm, or to replace it with a polymer sheet, made for example of PVDF, ETFE, ECTFE, or FEP, or with a sheet of a composite material based on glass fibers immersed in an epoxy resin.

[0009] The laminate is obtained by a hot lamination process at a temperature of approximately 150 °C. However, the lamination process has several drawbacks. In particular, it requires that the heating and compression phase of the laminate and the subsequent cooling phase be carried out in separate devices. Furthermore, controlling the cooling rate after lamination is difficult, which complicates the implementation of this process with thermoplastic polymers that can crystallize, become whitish, diffuse light more, and exhibit lower transparency upon cooling. In addition, the laminate is generally heated using an oil circuit with a flash point of no more than 194 °C. The hot lamination process is therefore not suitable for shaping polymer materials for which forming temperatures above 180 °C are required.Finally, the hot lamination process only allows the manufacture of flat photovoltaic modules.

[0010] Furthermore, to produce modules with complex three-dimensional shapes, in relief, and in particular with one or more curves, it is known to implement processes such as bag molding, autoclave molding, resin transfer molding (RTM molding), and reaction injection molding (RIM molding). However, these processes require long implementation times, which makes them inefficient and industrially uncompetitive.

[0011] There is therefore a need for a process that overcomes the aforementioned drawbacks. In particular, there is a need for a process that allows for the rapid manufacture of a photovoltaic module. Specifically, there is a need for a process that can manufacture photovoltaic modules of both planar and complex three-dimensional shapes, said process being simple and quick to implement.

[0012] The object of the invention is to meet, at least in part, this need(s). Description of the invention

[0013] To this end, the invention relates to a method for manufacturing a photovoltaic module, comprising the following steps: a) implementation of a multilayer stack between a mold and a counter-mold, the multilayer stack comprising a ferromagnetic element, separate and movable relative to the mold and the counter-mold, and as components to be bonded: - at least two electrically insulating encapsulation sheets comprising at least one polymer, - at least one photoelectric generator, preferably a photovoltaic cell, sandwiched between the encapsulation sheets, b) thermocompression of the multilayer stack comprising the following sub-steps: bi) application by the mold and counter-mold of pressure against the multi-layer stack, and, b2) heating the multilayer stack to a suitable temperature to bond together the components to be bonded in the multilayer stack so as to form the photovoltaic module, the heating is achieved by electromagnetic induction by applying a magnetic field at least to the ferromagnetic element.

[0014] The present invention therefore essentially consists of a manufacturing process employing thermocompression, comprising the electromagnetic induction heating of a ferromagnetic element directly embedded in the multilayer stack comprising the components to be bonded to form the photovoltaic module. Consequently, the process according to the present invention heats the multilayer stack directly in situ, thereby eliminating some of the thermal insulation that slows heat penetration and thus accelerating the temperature rise of the entire multilayer stack.

[0015] It is thus possible to carry out step b) of the process according to the present invention in less than 5 minutes, step b) representing almost the entire execution time of the process according to the present invention. By way of comparison, a conventional lamination process according to the prior art for manufacturing a photovoltaic module takes between 10 and 15 minutes.

[0016] Furthermore, by heating the multilayer stack directly in situ, the process according to the present invention reduces the amount of energy required to manufacture a photovoltaic module, since the energy needed for heating is directly invested in the multilayer stack and not in an external heating element. The process according to the present invention may thus require only 1 kWh / m² for its implementation, i.e., a power of 25 kW / m² for a duration of 5 minutes. By way of comparison, a conventional lamination process according to art Previously, the production of a photovoltaic module required between 3 and 4 kWh / m2.

[0017] Furthermore, the process according to the present invention is suitable for shaping polymer materials for which the shaping temperatures are above 180 °C.

[0018] The multilayer stack may have a planar or complex shape, including a curved shape. In particular, the multilayer stack may extend along one or more curved directions that differ from each other. It may have at least one surface with at least one raised relief and / or at least one recessed relief.

[0019] The ferromagnetic element can be part of the components to be linked in the multilayer stack during step a), and, be linked with the other components to be linked in the multilayer stack during step b).

[0020] Alternatively, the ferromagnetic element may not be part of the components to be bonded in the multilayer stack during step a), and may not be included in the photovoltaic module formed at the end of step b). If so, the ferromagnetic element may be extracted simultaneously with the extraction of the photovoltaic module from the interior space delimited by the mold and the counter-mold, which advantageously allows the production rate to be increased.

[0021] Unless otherwise stated, the pressures expressed in this description and in the claims are absolute. Mold and counter-mold

[0022] Preferably, the mold and / or counter-mold comprise an electrically insulating membrane extending opposite the multilayer stack when the latter is placed between the mold and the counter-mold. Preferably, the mold and the counter-mold each comprise such an electrically insulating membrane.

[0023] Preferably, the membrane of the mold and / or counter-mold has a thickness of between 1 and 10 mm, preferably between 3 and 6 mm.

[0024] Preferably, the membrane of the mold and / or counter-mold has a Young's modulus at 25 °C of less than 100 MPa, preferably less than 30 MPa.

[0025] Preferably, the membrane of the mold and / or counter-mold does not undergo plastic deformation during step b) of thermocompression.

[0026] Preferably, the membrane of the mold and / or counter-mold has a Young's modulus greater than 1 MPa at the temperature suitable for bonding together the components to be bonded of the multilayer stack.

[0027] Preferably, the mold and / or counter-mold membrane has a thermal conductivity of less than 2 W / mK, preferably less than 0.5 W / mK. Advantageously, the membrane also acts as a thermal insulator which minimizes heat transfers out of the interior space delimited by the mold and counter-mold and in which the multi-layer stack is housed.

[0028] Preferably, the membrane of the mold and / or counter-mold has an electrical resistivity greater than 100 mQ-cm, preferably greater than 100 MQ-cm.

[0029] Preferably, the membrane of the mold and / or counter-mold is made of silicone.

[0030] The counter-mold membrane can be adapted to conform to the shape of the mold face bearing against the multilayer stack. Alternatively, the face of the counter-mold bearing against the multilayer stack does not deform during the process and is of complementary shape with the face of the mold bearing against the multilayer stack.

[0031] The counter-mold can be made up of the electrically insulating membrane.

[0032] The mold may include at least one raised feature and / or at least one recessed feature against which the multilayer stack comes into contact during thermocompression. In particular, the mold may be shaped so that the photovoltaic module has at least one curve.

[0033] Preferably, the mold and / or counter-mold include at least one inductor, the magnetic field being generated during substep b2) by applying an electric current to the inductor.

[0034] Preferably, the electric current is alternating, preferably with a frequency between 20 and 30 kHz. Advantageously, the frequency of the electric current is sufficiently low so that the skin thickness, i.e., the depth of penetration of the magnetic field into the multilayer stack, is sufficiently small compared to the thickness of the ferromagnetic element, measured along the stacking direction of the multilayer stack. Advantageously, the frequency of the electric current is sufficiently high so that the skin effects occurring in the inductor(s) themselves are negligible.

[0035] Preferably, the electric current has a maximum intensity in the inductor(s) between 10 and 2000 A.

[0036] Preferably, the membrane of the mold and / or counter-mold is arranged between each inductor and the multilayer stack.

[0037] Preferably, the mold and / or the counter-mold comprise several inductors. Preferably, the mold comprises several inductors.

[0038] Preferably, the distance between two adjacent inductors being less than 20 cm.

[0039] Preferably, the mold and / or counter-mold comprise a circuit of Cooling. The cooling circuit can be carved directly into the mold and / or counter-mold. Alternatively, the mold and / or counter-mold can include tubes forming the cooling circuit.

[0040] Preferably, the mold and / or counter-mold have a relative magnetic permeability of less than 10 and even more preferably less than 2. Ferromagnetic element

[0041] The ferromagnetic element may have an electrical resistivity of less than 1 mQcm, preferably less than 0.1 mQ-cm.

[0042] The ferromagnetic element may have a thermal conductivity greater than 10 W / mK.

[0043] The ferromagnetic element may have a relative magnetic permeability greater than 1, preferably greater than 50.

[0044] The ferromagnetic element may comprise, or even be made of, iron or an iron-containing alloy, for example steel, in particular stainless steel, or cast iron.

[0045] Preferably, the ferromagnetic element is in the form of a plate, a continuous or perforated sheet, a film, a grid, a mesh, or an assembly of fibers or grains. The assembly of fibers or grains may include ferromagnetic fibers or grains integrated into a composite reinforcement or dispersed in at least one of the encapsulation sheets.

[0046] Preferably, the ferromagnetic element has a thickness, measured along the stacking direction of the multilayer stack, of between 10 pm and 5 mm, preferably between 0.15 mm and 1.5 mm.

[0047] The ferromagnetic element may be monolithic or discontinuous. Preferably, the ferromagnetic element is monolithic.

[0048] Preferably, the distance between the inductor and the ferromagnetic element is less than the distance between said inductor and the photoelectric generator.

[0049] Preferably, the distance between the inductor and the ferromagnetic element is less than 100 mm.

[0050] Preferably, the ferromagnetic element is arranged on the side of the photoelectric generator opposite the front face of the multilayer stack, the front face being the face of the multilayer stack intended, after obtaining the photovoltaic module, to be placed between the solar radiation source and the photoelectric generator.

[0051] According to a first embodiment, the ferromagnetic element can be arranged on the surface of the multilayer stack so as to form the outer face, referred to as the back face, of the multilayer stack opposite the front face. The ferromagnetic element thus serves as structural reinforcement for the photovoltaic module after fabrication. It can also serve as a magnetic fastening element for securing the photovoltaic module after fabrication. Preferably, the ferromagnetic element is in the form of a continuous sheet or plate, for example, a body panel.

[0052] According to a second embodiment, the multilayer stack can comprise several photoelectric generators, preferably being photovoltaic cells, and the ferromagnetic element can be arranged between the encapsulation sheets and between the photoelectric generators, preferably so as to electrically connect the photoelectric generators to each other.

[0053] According to a third embodiment, the multilayer stack may include, as a bonding component, a back-face sheet arranged on the surface of the multilayer stack so as to form the outer face, referred to as the back face, of the multilayer stack opposite the front face, the ferromagnetic element being sandwiched between the back-face sheet and one of the encapsulation sheets. The ferromagnetic element thus serves as structural reinforcement of the photovoltaic module after fabrication. Preferably, the ferromagnetic element is in the form of a perforated sheet, a grid, or a mesh. Preferably, the back-face sheet comprises at least one polymer, for example, polyethylene terephthalate, a single-layer or multi-layer polyamide, or a fluoropolymer such as ethylene tetrafluoroethylene, ethylene chlorotrifluoroethylene, or polytetrafluoroethylene. Sheets of the multilayer stack

[0054] Preferably, the encapsulation sheets have a thickness, measured along the stacking direction of the multilayer stack, of between 50 and 1500 pm.

[0055] Preferably, the polymer contained within the encapsulation sheets is thermoplastic, for example, polyolefin, polyurethane, or an ionomer. The polymer may be the same for each of the encapsulation sheets or may differ between two encapsulation sheets. At the end of the process, the constituent materials of the encapsulation sheets may have melted and then solidified to form an encapsulating assembly within the photovoltaic module in which the photoelectric generator(s) are embedded.

[0056] Preferably, the multilayer stack comprises several photoelectric generators, preferably photovoltaic cells, electrically connected to each other. Preferably, the photoelectric generators are arranged in a regular pattern along at least one direction in a plane normal to the stacking direction of the multilayer stack.

[0057] Preferably, the photoelectric generator(s) have a thickness, measured along the stacking direction of the multilayer stack, of between 0.5 and 300 pm.

[0058] Preferably, the photoelectric generator(s) are arranged above the ferromagnetic element. The term "above" is defined with reference to the gravitational force.

[0059] Preferably, the multilayer stack also includes, as a bonding component, a front-facing sheet arranged on the surface of the multilayer stack so as to form the external face, referred to as the front face, of the multilayer stack intended, after obtaining the photovoltaic module, to be positioned between the solar radiation source and the photoelectric generator. Thus, the front-facing sheet serves as a protective layer. Preferably, the front-facing sheet comprises at least one polymer, for example, polyethylene terephthalate, cyclic olefin copolymer, polymethyl methacrylate, polycarbonate, polyamide, polyurethane, styrene-acrylonitrile copolymer, polyvinyl chloride, polystyrene, or a fluoropolymer such as ethylene tetrafluoroethylene, ethylene chlorotrifluoroethylene, or polytetrafluoroethylene.

[0060] Preferably, the ferromagnetic element is arranged on the side of the photoelectric generator opposite to that arranged opposite the front face sheet.

[0061] Furthermore, the multilayer stack may have a planar or complex shape, including a curved shape. In particular, the multilayer stack may extend along one or more curved directions that differ from each other. It may have at least one surface with at least one raised relief and / or at least one recessed relief. Vacuum sealing

[0062] Preferably, step b) of thermocompression also includes a substep b3) of evacuating the internal space delimited by the mold and the counter-mold, in which the multilayer stack is housed. Evacuating the air prevents gas bubbles from being trapped between the components to be bonded in the multilayer stack, which degrade the properties of the photovoltaic module by facilitating moisture penetration and / or acting as a delamination initiation zone between the components to be bonded.

[0063] Preferably, said internal space is brought to a residual vacuum pressure of less than 1000 Pa, preferably less than 300 Pa, or even less than or equal to 100 Pa.

[0064] Preferably, the residual vacuum pressure in the internal space is reached before the temperature of the encapsulating sheets reaches the melting temperature of the materials. Typically, preferably before the temperature reaches 80°C, and even more preferably before 50°C. This allows the gas contained between the components to be bonded in the multilayer stack to be evacuated from the internal space before the encapsulating sheets melt due to their temperature. The temperature of the encapsulating sheets is, for example, determined from a measurement carried out using a calibration multilayer stack equipped with a thermocouple placed in contact with the encapsulating sheets and which has been subjected prior to step b) of thermocompression, or from the result of a thermal modeling of the thermocompression of the multilayer stacking, for example by the finite element method.

[0065] Preferably, the residual vacuum pressure in the internal space is reached before the application of pressure by the mold and counter-mold, in order to avoid the formation of gas bubbles trapped in the photovoltaic module and / or to reduce the risk of damage to the photoelectric generator(s).

[0066] Preferably, the time required to lower the pressure in the internal space from atmospheric pressure to residual vacuum pressure is less than 3 min, even more preferably less than 1 min.

[0067] Preferably, the mold and counter-mold are arranged in a sealed chamber during at least part of step b), and substep b3) also includes evacuating said chamber. Preferably, said chamber is maintained at a residual vacuum pressure of less than 1000 Pa, preferably less than 300 Pa, or even less than or equal to 100 Pa.

[0068] Preferably, the residual vacuum pressure in the chamber is reached before the application of pressure by the mold and counter-mold, then a break in the vacuum in the chamber is achieved when the application of pressure by the mold and counter-mold.

[0069] Preferably, the time required to lower the pressure in the chamber from atmospheric pressure to the residual vacuum pressure is less than 2 minutes. Heating

[0070] Substep b2) of heating the multilayer stack can be initiated before, concurrently or after substep b3).

[0071] Preferably, the temperatures of the mold, counter-mold and multilayer stack are below 50 °C, preferably below 30 °C, prior to the placement of the multilayer stack between the mold and the counter-mold.

[0072] Preferably, the heating includes a phase of raising the temperature of the ferromagnetic element to a holding temperature, followed by a phase of holding the temperature of the ferromagnetic element at the holding temperature.

[0073] Preferably, the rate of temperature rise of the ferromagnetic element during the rise phase is between 5 °C / min and 100 °C / min.

[0074] Preferably, the lifting phase is carried out at least partially during step b3) of vacuuming. Preferably, the lifting phase is initiated after step b3) of vacuuming has been initiated.

[0075] Preferably, the lifting phase has a duration of less than 15 min.

[0076] Preferably, the holding temperature is above 100°C, or even above 140°C.

[0077] Preferably, the maintenance phase has a duration of between 0 and 20 min.

[0078] The mold and / or counter-mold may include a heating plate that is heated during substep b2) so as to heat the multilayer stack by thermal conduction. The heating in substep b2) thus combines induction heating of the ferromagnetic element with heating by thermal conduction. This is particularly advantageous when the ferromagnetic element is arranged between the encapsulation sheets. Pressure application

[0079] Preferably, substep bi) of applying pressure through the mold and counter-mold is carried out after substep b2) of heating the multilayer stack has been initiated.

[0080] Preferably, substep bi) of applying pressure by the mold and counter-mold is initiated after the temperature of the encapsulation sheets is above 50 °C. Substep bi) of applying pressure by the mold and counter-mold can be initiated during the lifting phase of substep b2) or during the holding phase of substep b2).

[0081] Preferably, substep bi) of applying pressure by the mold and counter-mold is carried out at least in part during the holding phase of substep b2). Preferably, the holding phase of substep b2) is completed before the end of substep bi) of applying pressure by the mold and counter-mold.

[0082] Preferably, the pressure applied by the mold and the counter-mold during substep bi) is between 10 and 3000 kPa.

[0083] Preferably, substep bi) has a duration of between 0 and 34 min, or even between 0 and 5 min. Cooling

[0084] Preferably, step b) includes a substep b4) for cooling the photovoltaic module, substep b4) being subsequent to substep b2).

[0085] Preferably, the photovoltaic mold is cooled between the mold and the counter-mold, and preferably in contact with the mold and the counter-mold. Advantageously, the entire thermocompression step (b) can thus be carried out within the same device. This makes the process according to the invention simpler to implement, since step (b) is performed in a single cycle, and more efficient than a prior art lamination process that requires separate equipment to heat and cool the photovoltaic module.

[0086] Preferably, substep b4) of cooling is carried out at least partially during substep bi) of applying pressure by the mold and counter-mold. This prevents the photovoltaic module from deforming during cooling. Preferably, substep bi) of applying pressure by the mold and counter-mold continues at least until the temperature of the photovoltaic module is below 60 °C.

[0087] Preferably, substep b4) of cooling includes circulating a cooling fluid in the cooling circuit of the mold and / or counter-mold.

[0088] Preferably, the cooling rate of the photovoltaic module during substep b4) is between -2 °C / min and -100 °C / min.

[0089] Preferably, step b) is followed by step c) of extracting the photovoltaic module from the interior space delimited by the mold and counter-mold. Brief description of the drawings

[0090] Other advantages and features will become clearer upon reading the detailed description, given by way of illustration and not limitation, with reference to the following figures:

[0091] [Fig-1] [Fig.1] is a schematic cross-sectional view of the installation of a multi-layer stacking between a mold and a counter-mold according to a first example of embodiment of step a) of the process according to the present invention;

[0092] [Fig.2] [Fig.2] is a schematic cross-sectional view of the placement of a multilayer stack between a mold and a counter-mold according to a second embodiment of step a) of the process according to the present invention;

[0093] [Fig.3] [Fig.3] is a graph representing the evolution over time of the temperatures of the different components of the multilayer stack during substep b2) of heating of a first example of implementation of the process according to the present invention;

[0094] [Fig.4] [Fig.4] is a graph representing the evolutions, as a function of the thickness of the ferromagnetic element, of the rate of rise of the average temperature of the multilayer stack during substep b2) of a first example of implementation of the process according to the present invention and of the temperature differences between the ferromagnetic element and the front face sheet at the end of the rise phase and at the end of the holding phase for said first example;

[0095] [Fig. 5] [Fig. 5] is a graph representing the evolution, as a function of the thickness of the encapsulation sheets, of the rate of rise of the average temperature of the multilayer stack during substep b2) of a first example of implementation of the process according to the present invention and the differences in temperature between the ferromagnetic element and the front face foil at the end of the lifting phase and at the end of the holding phase for said first example;

[0096] [Fig. 6] [Fig. 6] is a graph representing the evolution of the characteristic time of approximation depending on the thickness of the encapsulation sheets, for a first example of implementation of the process according to the invention;

[0097] [Fig.7] [Fig.7] is a graph representing the changes, as a function of the current power applied to the inductors, the rate of rise of the average temperature of the multilayer stack during substep b2) of a first example of implementation of the process according to the present invention and the temperature differences between the ferromagnetic element and the front face foil at the end of the rise phase and at the end of the holding phase for said first example;

[0098] [Fig.8] [Fig.8] is a graph representing the changes over time in temperatures of the different components of the multilayer stack during substep b2) of heating of a second example of implementation of the process according to the present invention;

[0099] [Fig.9] [Fig.9] is a graph representing the changes over time temperatures of the different components of the multilayer stack during a lamination process. Detailed description

[0100] For reasons of clarity, the different elements of the figures are represented to a free scale, the actual dimensions of the different parts not necessarily being respected.

[0101] Figure 1 illustrates an example of implementing step a) of the process according to the present invention. A multilayer stack 1 is placed between a mold 2 and a counter-mold 3.

[0102] The multilayer stack 1 comprises two encapsulation sheets 4 sandwiching a plurality of coplanar photovoltaic cells 5 electrically connected to each other to form a skeleton, also known as a "string" 6. The encapsulation sheets 4 are electrically insulating and comprise at least one polymer. The encapsulation sheets 4 are intended to form, after melting and solidification, an encapsulating assembly within the photovoltaic module once manufactured, the photovoltaic cells 5 being embedded in said encapsulating assembly.

[0103] The multilayer stack 1 also includes a front face sheet 7 comprising at least one polymer and a ferromagnetic element 8, in the form of a plate, forming the rear face of the multilayer stack 1. The front face sheet before 7 and the ferromagnetic element 8 sandwich all the other components to be linked in the multilayer stack 1.

[0104] The mold 2 comprises a body 9 whose face intended to be in contact with the multilayer stack 1, and in particular with the ferromagnetic element 8, is covered by an electrically and thermally insulating membrane 10.

[0105] The mold 2 also includes inductors 11 housed in the body 9. The inductors 11 are arranged regularly along the membrane 10. Each inductor has a linear shape and extends parallel to the other inductors 11. The inductors 11 are substantially equidistant from the face of the membrane 10 opposite the multilayer stack 1. Advantageously, the distribution and arrangement of the inductors 11 reduce the variations in space of the magnetic field generated by said inductors 11 and thus increase the homogeneity of the power injected into the ferromagnetic element 8 during heating in step b) of the process.

[0106] The mold 2 also includes a cooling circuit 12 in which a cooling fluid is intended to circulate during the cooling of step b) of the process according to the invention.

[0107] The counter-mold 3 consists of a thermally, and possibly also electrically, insulating membrane intended to be in contact with the multilayer stack 1, and in particular with the front face sheet 7. The membrane constituting the counter-mold 3 is able to conform to the shape of the face of the mold 2 which rests against the multilayer stack 1.

[0108] Figure 2 illustrates another example of implementing step a) of the method according to the present invention. The multilayer stack 1 of this other example differs from that illustrated in Figure 1 in that the ferromagnetic element no longer forms the rear face of said multilayer stack 1 but is sandwiched between the encapsulation sheets 4 and arranged between the photovoltaic cells 5. In particular, the ferromagnetic element 13 can then be used as a means of electrically connecting at least some or all of the photovoltaic cells 5 to one another. In particular, the ferromagnetic element 13 constitutes at least some, or even all, of the electrically connecting means of the string 6.

[0109] The multilayer stack 1 illustrated in [Fig. 2] also includes a back face sheet 14 comprising at least one polymer. The front face sheet 7 and the back face sheet 14 sandwich all the other components to be bonded in the multilayer stack 1.

[0110] The counter-mold 3 illustrated in [Fig.2] differs from that illustrated in [Fig.1] in that it comprises a body 15 whose face opposite the multilayer stack 1 is covered by an electrically and thermally insulating membrane 16.

[0111] The counter-mold 3 also includes inductors 17 housed in the body 15. The inductors 17 are arranged regularly along the membrane 16. Each inductor 17 has a linear shape and extends parallel to the other inductors 17. The inductors 17 are substantially the same distance from the face of the membrane 16 opposite the multilayer stack 1. Advantageously, the distribution and arrangement of the inductors 17 reduce the variations in space of the magnetic field generated by said inductors 17 and thus increase the homogeneity of the power injected into the ferromagnetic element 13 during the heating of step b) of the process.

[0112] The counter-mold 3 also includes a cooling circuit 18 in which a cooling fluid is intended to circulate during the cooling of step b) of the process according to the invention.

[0113] For each of the examples illustrated in Figures 1 and 2, step a) is followed by a step b) of thermocompression of the multilayer stack 1. Step b) includes the application by the mold 2 and the counter-mold 3 of pressure against the multilayer stack 1, during a substep bi). Step b) also includes the substep b2) of heating the multilayer stack 1 to a suitable temperature to bond together the components to be bonded of the multilayer stack 1 so as to form a photovoltaic module.

[0114] Step b) also includes a substep b3) of evacuating the internal space delimited by the mold 2 and the counter-mold 3 and in which the multilayer stack 1 is housed. During step b), the mold 2 and the counter-mold 3 may be housed in a sealed chamber, and substep b3) may include evacuating said chamber.

[0115] Preferably, substep b3) and substep b2) are configured so that the internal space and chamber are brought to a residual vacuum pressure of less than 1000 Pa before the temperature of the encapsulation sheets 4 is at least 50 °C.

[0116] Substep b2) includes a phase of raising the temperature of the ferromagnetic element 8 or 13 to a holding temperature, followed by a phase of holding the temperature of the ferromagnetic element 8 or 13 at the holding temperature.

[0117] Preferably, substep b2) is initiated prior to substep bi). In particular, substep bi) of applying pressure by the mold 2 and the counter-mold 3 is initiated after the temperature of the encapsulation sheets 4 is greater than 80°C.

[0118] Simultaneously or prior to the initiation of substep bi), the pressure outside the chamber can be lowered partially or completely, i.e. the pressure can be reduced to 10 kPa.

[0119] The temperature and pressure applied by the mold 2 and the counter-mold 3 are maintained together for a suitable set time so that the components to be bonded, which form the multilayer stack 1, are irreversibly bonded to obtain the photovoltaic module. Then, the vacuum in the internal space is completely broken, i.e., the pressure is reduced to around 105 Pa.

[0120] Next, step b) includes a substep b4) of cooling the photovoltaic module obtained at the end of substep b2) and during substep bi). The cooling substep b4) includes the circulation of a cooling fluid in the cooling circuit 12 of the mold 2 and / or the cooling circuit 18 of the counter-mold 3.

[0121] During substep b4), the mold 2 and the counter-mold 3 continue to apply pressure to the photovoltaic module until the temperature of the photovoltaic module is below 60°C. The photovoltaic module can then be extracted from between the mold 2 and the counter-mold 3, during a step c). Example 1

[0122] A first example of a simulation of the implementation of the process according to the present invention for manufacturing a photovoltaic module is detailed below.

[0123] For this simulation, the inventors chose a multilayer stack 1 composed of the following components to be bonded: - a front face sheet 7 made of polyethylene terephthalate (PET) with a thickness of 0.3 mm; - two encapsulation sheets 4 in polyolefin (TPO) with a thickness of 0.6 mm each; - a silicon layer, corresponding for the simulation to a string 6 of the photovoltaic cells 5, with a thickness of 0.2 mm; - a steel plate, forming the ferromagnetic element 8 and the back face sheet of the multilayer stack 1, with a thickness of 1 mm.

[0124] For this simulation, the inventors considered that the mold 2 and the counter-mold 3 each comprised a membrane 10, respectively 16, thermally and electrically insulating, each membrane 10, respectively 16, was made of silicone with a thickness of 5 mm.

[0125] The following table summarizes the properties of the materials used for this simulation:

[0126] [Tables 1] Material Density ρ (kg / m³) Specific heat capacity Cp (J / kg / K) Thermal conductivity X (W / m / K) Silicone 1150 1590 0.23 PET 1380 1140 0.26 TPO 1020 1390 0.20 Silicon 2600 700 140 Steel 7800 440 45 Glass 2600 720 1

[0127] The inventors used the following formula to calculate the power dissipated, P diS, by the ferromagnetic element 8 during substep b2) of electromagnetic induction heating:

[0128] [Math.l] Pdis*

[0129] where:

[0130] [Math.2] 6 = J..............'

[0131] with o the electrical conductivity of the material, qo the magnetic permeability of free space, pr the relative magnetic permeability of the material, / the frequency of the magnetic field, 1 the maximum intensity of the alternating current supplying the inductors 11 generating the magnetic field and x the depth of the ferromagnetic element 8 which varies between 0 and a thickness equal to 1 mm.

[0132] In order to determine the proportionality factor of formula [Math 1], the inventors empirically measured a surface power dissipation P of 125 kW / m² for a steel plate corresponding to that chosen for the simulation, for a frequency of 25 kHz and a maximum current of 300 A. By performing the calculation of formula [Math 1], with an electrical conductivity of 10⁶ S / m and a relative magnetic permeability of 100, the inventors determined that the proportionality factor was 1 / 700. This factor will be used for the remainder of the simulation.

[0133] For the simulation, the inventors considered a heat transfer coefficient of 10 W / m² / K, and a heating substep b2) comprising a phase of raising the temperature of the ferromagnetic element 8 to a holding temperature of 200 °C, followed by a phase of holding the temperature of the ferromagnetic element 8 at the holding temperature. The heating phase was simulated with induction heating of the ferromagnetic element 8 by generating a magnetic field by supplying the inductors 11 with an alternating current of frequency equal to 25 kHz and maximum intensity equal to 300 A.

[0134] The simulation results are illustrated in [Fig. 3]. Curve 19 represents the temperature evolution of the ferromagnetic element 8 over time. Curve 20 represents the temperature evolution of the encapsulation sheet 4 adjacent to the ferromagnetic element 8 over time. Curve 21 represents the temperature evolution of the string 6 over time. Curve 22 represents the temperature evolution of the encapsulation sheet 4 furthest from the ferromagnetic element 8 over time. Curve 23 represents the temperature evolution of the front face sheet 7 over time. Curve 24 represents the temperature evolution of the membrane 10 of the mold 2 over time. Curve 25 represents the temperature evolution of the membrane 16 of the counter-mold 3 over time.

[0135] The inventors also carried out empirical measurements under conditions similar to those chosen for the simulation and obtained similar results.

[0136] The inventors obtained an average temperature rise rate of the multilayer stack 1 of 18 K / min. The same rate was empirically measured, thereby validating the model used for the simulation. The inventors then calculated the evolution of said average temperature rise rate of the multilayer stack 1 as a function of the thickness of the ferromagnetic element 8. This evolution is represented by curve 26 in [Fig. 4].

[0137] Although the rate of rise of the average temperature of the multilayer stack 1 depends significantly on the thickness of the ferromagnetic element 8, curve 26 shows that, in all cases, said rate is sufficiently high for the thermocompression of the multilayer stack 1. Thus, a small thickness of the ferromagnetic element 8 is quite conceivable, which makes it possible to reduce the weight of the photovoltaic module manufactured.

[0138] The inventors also calculated the evolution, as a function of the thickness of the ferromagnetic element 8, of the temperature difference between the ferromagnetic element 8 and the front face sheet 7 at the end of the lifting phase, represented by curve 27 in [Fig.4], and at the end of the holding phase, represented by curve 28 in [Fig.4].

[0139] As can be seen in [Fig. 3], heat diffusion occurs beyond the temperature rise phase of the ferromagnetic element 8. During the temperature maintenance phase of the ferromagnetic element 8, the temperatures the other components of the multilayer stack 1 approach the maintenance temperature according to a formula of the form:

[0140] [Math.3] A+Be*

[0141] where r is called the characteristic approach time.

[0142] This characteristic approach time r was measured at 240 s for this simulation. By varying the thickness of the different components of the multilayer stack 1 and of the membranes 10 and 16 during the simulations, the inventors found that this characteristic approach time r depends very little on the thickness of the ferromagnetic element but depends strongly on the thickness of the membranes 10 and 16, and on the thickness of the encapsulation sheets 4. As the thickness of the membranes 10 and 16 decreases, the characteristic approach time r decreases, but the temperatures between the different components of the multilayer stack 1 are not as homogeneous. As the thickness of the encapsulation sheets 4 increases, the characteristic approach time r increases.

[0143] These results are illustrated in [Fig. 5], which shows curve 29 representing the evolution of the rate of increase of the average temperature of the multilayer stack 1 as a function of the thickness of the encapsulation sheets 4, and curves 30 and 31 representing the evolution, as a function of the thickness of the encapsulation sheets 4, of the temperature difference between the ferromagnetic element 8 and the front face sheet 7 at the end of the heating phase and at the end of the holding phase, respectively. Figure 6 also illustrates the evolution of the characteristic approach time r as a function of the thickness of the encapsulation sheets 4.

[0144] The inventors also calculated the evolution of the rate of increase of the average temperature of the multilayer stack 1 as a function of the current applied to the inductors 11, illustrated by curve 32 in [Fig. 7]. The thickness of the ferromagnetic element 8 for these calculations was 1 mm and the thickness of the encapsulation sheets 4 for these calculations was 0.6 mm. Curves 33 and 34 represent the evolution, as a function of the current applied to the inductors 11, of the temperature difference between the ferromagnetic element 8 and the front-facing sheet 7 at the end of the heating phase and at the end of the holding phase, respectively.

[0145] As can be seen from [Fig. 7], a reduction in the applied current power would require only a slight increase in the total duration of heating substep b2) or a slight increase in the temperature lag between the ferromagnetic element 8 and the front face sheet 7. Advantageously, a reduction in the applied current power reduces the stresses on the mold 2, the counter-mold 3 and the current generator supplying the inductors 11, thus reducing the implementation cost of the process according to the present invention. Furthermore, this extends the time window during which the various substeps bi), b2), and b3) of the process can be carried out simultaneously.

[0146] The inventors' simulations have shown that the characteristic approach time r does not depend on the current power applied to the inductors 11.

[0147] Based on the results of the first example, the inventors estimate that the time required to carry out step b) of the process according to the present invention can be less than 5 min, with a current power applied to the inductors 11 equal to 25 kW / m2. Under these conditions, the encapsulation sheets 4 would reach a temperature greater than 150 °C within one minute of the initiation of heating substep b2). Example 2

[0148] A second example is detailed below, comparing the implementation of the process of the present invention to a lamination process for obtaining a photovoltaic module.

[0149] For this second example, the inventors chose a multilayer stack 1 formed from the following components to be bonded: - a front face sheet 7 made of glass with a thickness of 3.2 mm; - two encapsulation sheets 4 in polyolefin (TPO) with a thickness of 0.6 mm each; - a silicon layer, corresponding for the simulation to string 6 of photovoltaic cells 5, with a thickness of 0.2 mm; - a steel plate, forming the ferromagnetic element 8 and the back face sheet of the multilayer stack 1, with a thickness of 1 mm.

[0150] The properties of the aforementioned materials are given in Table 1. The chosen holding temperature was 180 °C. In the case of the implementation of the process according to the present invention, the mold 2 and the counter-mold 3 each comprised a membrane 10, respectively 16, as described for Example 1. In the case of the implementation of the lamination process, the laminator plate was made of steel with a thickness of 20 mm and rested against the front face sheet 7, a silicone membrane being arranged against the steel plate forming the back face sheet.

[0151] Figures 8 and 9 illustrate the temperature evolution curves of each of the components of the multilayer stack 1 during the process according to the present invention, respectively during the lamination process.

[0152] Curve 35 represents the temperature evolution of the ferromagnetic element 8 during step b) of the process according to the present invention. Curve 36 represents Curve 37 represents the temperature evolution of the encapsulation sheet 4 adjacent to the ferromagnetic element 8 during step b) of the process according to the present invention. Curve 38 represents the temperature evolution of the encapsulation sheet 4 furthest from the ferromagnetic element 8 during step b) of the process according to the present invention. Curve 39 represents the temperature evolution of the front face sheet 7 during step b) of the process according to the present invention. Curve 40 represents the temperature evolution of the membrane 10 of the mold 2 during step b) of the process according to the present invention. Curve 41 represents the temperature evolution of the membrane 16 of the counter-mold 3 during step b) of the process according to the present invention.

[0153] Curve 42 represents the temperature evolution of the laminator plate during the lamination process. Curve 43 represents the temperature evolution of the front face sheet 7 during the lamination process. Curve 44 represents the temperature evolution of the encapsulation sheet 4 furthest from the steel plate during the lamination process. Curve 45 represents the temperature evolution of the string 6 during the lamination process. Curve 46 represents the temperature evolution of the encapsulation sheet 4 adjacent to the steel plate during the lamination process. Curve 47 represents the temperature evolution of the steel plate during the lamination process. Curve 48 represents the temperature evolution of the membrane positioned against the steel plate during the lamination process.

[0154] Figures 8 and 9 show that the process according to the present invention heats the multilayer stack 1 directly in its natural state, which avoids some of the thermal insulation slowing down the penetration of heat and thus accelerates the temperature rise of the entire multilayer stack 1, compared to a lamination process. Example 3

[0155] A third example of implementation of the process according to the present invention is detailed below, in which the ferromagnetic element is not part of the components to be linked in the multilayer stack, and is not included in the photovoltaic module formed at the end of step b).

[0156] The back face sheet 14 was first prepared by thermocompression of a multilayer structure between the mold 2 and the counter-mold 3, with a ferromagnetic element arranged between the mold 2 and the counter-mold 3, being separate and movable with respect to the mold 2 and the counter-mold 3. The multilayer structure was formed by the superposition of the following sheets one on top of the other.

[0157] A first sheet was obtained from a blank consisting of three plies, each made of a non-woven carbon fiber material with a surface mass of 300 g / m2 and pre-impregnated with polypropylene. The blank was shaped against the mold 2 and the counter-mold 3, with a ferromagnetic element arranged between the mold 2 and the counter-mold 3, being separate and movable relative to the mold 2 and the counter-mold 3, by thermocompression, with an application of a pressure of 700 kPa, heating of the ferromagnetic element to a set temperature of 220 °C reached in 1 minute and 40 seconds, holding at the set temperature for 4 minutes and cooling for 1 minute and 30 seconds to a temperature of 30 °C. The pressure applied by mold 2 and counter-mold 3 was then removed and the first shaped sheet was extracted from between mold 2 and counter-mold 3.

[0158] A second sheet was obtained from a blank consisting of a fold made of a carbon fiber fabric with a surface mass of 200 g / m2 and two polypropylene felts, each with a thickness of 45 pm, on either side of the fabric. A transparent polyolefin film with a thickness between 25 pm and 60 pm (with a surface mass between 23 and 55 g / m2) was placed on the side of the mold 2 to improve the subsequent adhesion of the back face sheet 14. The blank was formed against the mold 2 and the counter-mold 3, with a ferromagnetic element arranged between the mold 2 and the counter-mold 3, being separate and movable with respect to the mold 2 and the counter-mold 3, by thermocompression under the same operating conditions as the first sheet, except that the set temperature was 230 °C.

[0159] The back face sheet 14 was then formed by stacking the first and second sheets one on top of the other. The first sheet was positioned opposite the mold 2 and the second sheet opposite the counter-mold 3. The multilayer structure was formed against the mold and the counter-mold 3, with a ferromagnetic element arranged between the mold 2 and the counter-mold 3, being separate and movable with respect to the mold 2 and the counter-mold 3, by thermocompression under the same operating conditions as the second sheet.

[0160] A multilayer stack 1 was then prepared by superimposing at least one ferromagnetic element with components to be bonded stacked in the following order: - a front face sheet 7 made of a polyethylene terephthalate-based film with a thickness of 0.28 mm, - two encapsulation sheets 4, each with a thickness of 600 µm, made of a thermoplastic encapsulant having a Young's modulus of 18 MPa, - photovoltaic cells 5, each with a thickness between 0.14 mm and 0.18 mm and electrically connected to each other by interconnecting ribbons with a thickness between 0.1 mm and 0.3 mm, - an encapsulation sheet 4 with a thickness of 600 pm, made of a thermoplastic encapsulant having a Young's modulus of 18 MPa, and - the back face sheet 14 described above.

[0161] The multilayer stack 1 was arranged between the mold 2 and the counter-mold 3, with the front face sheet 7 facing the inner face of the mold 2.

[0162] The multilayer stack 1 underwent thermocompression as described above. The multilayer stack 1 was first evacuated in the internal space to a residual vacuum pressure of less than 1 kPa for 3 minutes and 10 seconds. The ferromagnetic element was heated from approximately 30 °C to a set temperature of 170 °C for 1 minute and 17 seconds and then held at the set temperature for 5 minutes. A pressure of 350 kPa was applied by the mold 2 and the counter-mold 3 for 3 minutes and 10 seconds after the start of heating the ferromagnetic element. The ferromagnetic element was then cooled for 1 minute and 30 seconds. The pressure applied by the mold 2 and the counter-mold 3 was then removed and the ferromagnetic element and the photovoltaic module thus manufactured were extracted from between the mold 2 and the counter-mold.

[0163] Other variants and improvements may be envisaged without departing from the scope of the invention as defined by the following claims.

Claims

Demands

1. A method for manufacturing a photovoltaic module, comprising the following steps: a) placing a multilayer stack (1) between a mold (2) and a counter-mold (3), the multilayer stack comprising a ferromagnetic element (8, 13), separate and movable relative to the mold and the counter-mold, and as components to be bonded: - at least two electrically insulating encapsulation sheets (4) comprising at least one polymer, - at least one photoelectric generator, preferably a photovoltaic cell (5), sandwiched between the encapsulation sheets, b) thermocompression of the multilayer stack comprising the following substeps: bi) applying pressure by the mold and the counter-mold against the multilayer stack, and, b2) heating the multilayer stack to a suitable temperature to bond together the components to be bonded of the multilayer stack so as to form the photovoltaic module,The heating is achieved by electromagnetic induction by applying at least one magnetic field to the ferromagnetic element.

2. Method according to the preceding claim, the mold and / or counter-mold comprising an electrically insulating membrane (10, 16) extending opposite the multilayer stack, when the latter is placed between the mold and the counter-mold.

3. Method according to the preceding claim, the membrane of the mold and / or counter-mold having a thermal conductivity of less than 2 W / mK, preferably less than 0.5 W / mK.

4. A method according to any one of the preceding claims, the mold and / or counter-mold comprising at least one inductor (11, 17), the magnetic field being generated during substep b2) by applying an electric current to the inductor.

5. Method according to the preceding claim, the electric current being alternating, preferably with a frequency between 20 and 30 kHz.

6. Method according to claim 4 or 5, the distance between the inductor and the ferromagnetic element being less than the distance between said inductor and the photoelectric generator.

7. A method according to any one of the preceding claims, the ferromagnetic element having a thermal conductivity greater than 10W / mK.

8. A method according to any one of the preceding claims, the ferromagnetic element having a relative magnetic permeability greater than 1, preferably greater than 50.

9. A method according to any one of the preceding claims, the ferromagnetic element comprising iron or an alloy containing iron, for example steel, in particular stainless steel, or cast iron.

10. A method according to any one of the preceding claims, the ferromagnetic element being in the form of a plate (8), a continuous or perforated sheet, a film, a grid, a net or an assembly of fibers or grains.

11. A method according to any one of the preceding claims, the ferromagnetic element being part of the components to be bonded of the multilayer stack in step a), and being bonded with the other components to be bonded of the multilayer stack in step b).

12. Method according to the preceding claim, the ferromagnetic element (8) being arranged on the surface of the multilayer stack so as to form the external face, referred to as the back face, of the multilayer stack opposite the external face, referred to as the front face, of the multilayer stack intended after obtaining the photovoltaic module to be disposed between the solar radiation source and the photoelectric generator.

13. Method according to claim 11, the multilayer stack comprising several photoelectric generators, preferably being photovoltaic cells, and the ferromagnetic element (13) being arranged between the encapsulation sheets and between the photoelectric generators, preferably so as to electrically connect the photoelectric generators to each other.

14. A method according to any one of the preceding claims, the thermocompression step (b) also comprising a substep (b3) of evacuating the internal space delimited by the mold and counter-mold and in which the multilayer stack is housed, of preferably, said interior space being brought to a residual vacuum pressure of less than 1000 Pa, preferably less than 300 Pa, or even less than or equal to 100 Pa.

15. A method according to any one of the preceding claims, the heating comprising a phase of raising the temperature of the ferromagnetic element to a holding temperature, followed by a phase of holding the temperature of the ferromagnetic element at the holding temperature, the holding temperature preferably being greater than 100°C, or even greater than 140°C.