FR2466865A1 - Mfg. panel of solar cells forming photoelectric battery - where cells are embedded in thermoplastic films welded together and located above laminate contg. reflecting metal foil - Google Patents

Abstract

An assembly of solar cells, which are connected together electrically and provided with output terminals, is located in cavities in a thermoplastic film (5), which can be welded to an upper, transparent thermoplastic foil (6) through which solar rays reach the active surfaces of the cells; and film (5) can also be welded to a lower thermoplastic foil (7). Foil (6) is covered by a transparent rigid element or pane (8), which can be welded to foil(6); whereas foil (7) is located above a flexible metal foil (10) resting on a polymer (11). The assembly is welded together; and pane (8) is pref. glass, whereas foils (5,6,7) are pref. polyvinyl-butyral; and foil (10) is pref. Al or an Al alloy. Polymer (11) is pref. PVC, and is pref. sepd. from foil (10) by a mesh fabric (12) made esp. from polyester-, polyamide-, glass-, carbon-, or boron- fibres. This battery has a lower cost than that described in an earlier RTC patent 2349959.

Description

 The present invention relates to a method of manufacturing a panel of solar cells forming a photoelectric battery and comprising a plurality of photocells connected together electrically and leading to connections of electrical outputs immersed in a laminate comprising in particular a first film of a first transparent thermoplastic substance, a central film of a thermoplastic substance which can be welded to said first substance, said film comprising recesses in which said solar cells are arranged, one active face facing said transparent film, a second film of a second weldable thermoplastic substance a the substance of said film, said method comprising in particular a welding phase during which heat is applied.

 The present invention also relates to a means of implementing this manufacture and the panels obtained by this method.

 We know that solar cells are generally used in batteries in the form of panels on which said photocells are fixed close to each other in a regular mosaic and are electrically connected in series, in parallel or, more often, in a series-parallel combination using flexible metal tabs for example.

 The problems which appear most often in the production of such panels concern either their efficiency, their heating, or the cost price of their production.

 In fact, it is important that a panel retains its qualities over time, which means that the surface condition of the semiconductor used, in particular silicon, remains stable and, for this, that the solar cells are protected vis-à-vis of the atmosphere. It is therefore necessary that the panel remains airtight, especially in air and humidity.

 It is also important that it can evacuate the fraction of energy which has not been transformed into electrical energy and which appears in thermal form, since a marked heating decreases the efficiency of the solar cells.

 Finally, the cost of solar panels of sufficient dimensions for the power supplied to be attractive is high.

This cost depends on the value of the semiconductor material used, that of the mechanical supports and, above all, the handling time due to the care to be taken in the production.

 Some types of solar panels have already appeared on the market. The Applicant has described in patent 2 349 959 a process for producing a panel comprising two external rigid sheets, at least one of which is transparent and inside which the solar cells are inserted into the recesses of a central film in a thermoplastic material disposed between two lateral thermoplastic elements, at least one of which is transparent, weldable, on the one hand, to said film and, on the other hand, to said rigid sheets. A treatment is carried out on this laminate comprising a hot bonding phase.

 This process which is much superior to what lton did previously has the main drawback of being expensive.

 The present invention overcomes this drawback, it takes into account the strength qualities of modern plastic materials.

 The present invention relates, in fact, to a method of manufacturing a panel of solar cells forming a photoelectric battery and comprising a plurality of photocells electrically connected to each other and leading to connections at all of electrical outputs immersed in a laminate. 'a first transparent thermoplastic substance, a central film of a thermoplastic substance which can be welded to said first substance, said film comprising recesses in which said solar cells are arranged, one active face being turned towards said transparent film, a second film of a second substance thermoplastic which can be welded to the substance of said film, said method comprising in particular a welding phase during which heat is applied, a method which is particularly remarkable in that said laminate comprises a single rigid element placed outside said first film, said element was ant transparent and weldable to said first film and in that said laminate comprises at least one flexible metal sheet disposed outside of said second film and weldable thereto and a layer of plastic material arranged outside said sheet and weldable to it.

 Such a method according to the invention has many advantages. In fact, since plastics are cheap, the cost savings are certain. Furthermore, the presence of the metal foil makes the product obtained perfectly waterproof and improves the thermal conductivity, which means that, on the one hand, the entire panel is well protected against atmospheric agents and that, on the other hand , the solar cells are better cooled. Finally, the panel obtained is less heavy, therefore more manageable and easier to install.

 Advantageously, said transparent rigid element is made of glass, the first thermoplastic substance and / or the central film and / or the second thermoplastic substance also being preferably a synthetic resin of the polyvinylbuty- # ral type.

 The qualities of stability to ultraviolet radiation and of weldability, in particular to glass, of polyvinyl butyral are known and have been tested by the Applicant.

 Preferably, the metal sheet is a laminar layer of aluminum or an aluminum-based alloy.

 This metal, in fact, can laminate to a thickness of a few hundredths of a millimeter which it presents great flexibility while still remaining perfectly waterproof.

 In addition, this metal is reflective, a characteristic which in this case is of great interest: in fact, the radiation having passed through the thickness of the panel without being absorbed in the vicinity of the semiconductor junction of the solar cells is then reflected by the aluminum sheet. or of aluminum alloy and pass through the photocells again and are at least partially converted into current at said junction.

 This leads to a significant improvement in the performance of the panel.

 Such an advantage is particularly advantageous for the reinjection of infrared radiation having passed through the solar panel. In fact, to avoid overheating of the solar cells due to these radiations, it may be useful to replace the uniform contact-making layer on the face of the solar cells opposite the active face, called the rear face, with a metal grid covering only part of the total surface of said rear face: under these conditions, said radiation then passes through the panel but the presence of the aluminum foil or aluminum alloy allows reinjection into the solar cells where they are at least partially converted while running. This advantage is particularly noticeable in the case where, for example, to allow better use of the total surface of the panel, it is made up of square solar cells.

 Preferably, the plastic layer can be made of polyvinyl chloride, a resistant material having the advantage, among other things, of being weldable to other plastic materials.

 Advantageously, the laminate also comprises, between the metal sheet and said plastic layer, a mesh network of drawn fibers constituting a task or net fabric.

 The purpose of the mesh network is to strengthen the resistance of the metal sheet, in particular the resistance to elongation, so as to avoid in said sheet the appearance of cracks, even microscopic, generated by large forces, cracks which would make said sheet permeable. In addition, this mesh network makes the whole of the second thermoplastic film, the metal sheet and the outer layer of plastic practically tear-resistant. In fact, the mesh network gives this assembly a toughness greater than that which a film layer of synthetic material can give it. The solar cells are therefore perfectly protected.

 Said mesh network can be obtained from a thermoplastic synthetic material, polyester or polyamide for example, or alternatively from glass, carbon or boron fibers.

 Advantageously, we can separate this process in two steps.

During a first step, first create, by 7 hot amna, a sub-assembly comprising at least the plastic layer, the metal foil and said second film and possibly the mesh network, then, at during a second step, there is placed against this sub-assembly thus laminated, said central film comprising in recesses the photoelectric cells joined in a network, said first film and said transparent rigid element and the assembly is carried out.

 This separation of the process into two stages is extremely advantageous; the use of the laminated sub-assembly and its installation are much simpler than those of a large number of free elements with respect to each other. We can manufacture the pre-laminated sub-assembly, and even have it manufactured outside. As it is flexible, it can be stored in a roll.

 The present invention also relates to a means for implementing the method according to the invention, characterized in that said means consists of a laminated sub-assembly, comprising at least one polyvinyl butyral film, an aluminum foil, a layer of plastic material, in particular a layer of polyvinyl chloride and, optionally, between the layer of aluminum and said layer of plastic material, a mesh network in particular made of drawn fibers.

The present invention further relates to solar panels produced by the method according to the invention and comprising a rigid and transparent element, a first film of a transparent thermoplastic substance, solar cells, one active face of which faces towards said transparent element and with flanks and rear side surrounded
of a thermoplastic substance welded to a metal sheet and, optionally between said metal sheet and said plastic layer, a mesh network of drawn fibers.

 The description which follows, with reference to the appended drawings, will make it clear how the invention can be implemented.

 Figure 1 is a partial top view of a solar cell panel obtained by the method according to the invention.

 Figure 2 shows a schematic section along the line II-II of this same panel.

 Figure 3 is a more detailed view of the laminate sub-assembly according to the invention.

 Figures 4 and 5 show two devices for producing solar panels from the method according to the invention.

 It should be noted that, in the figures, certain dimensions are increased or reduced in disproportionate and exaggerated ways, this in order to make the drawing clearer.

 In accordance with Figures 1 and 2, the panel 1 produced by the method according to the invention consists of solar cells 2 electrically connected to each other by the connection tabs 3 and to the outside by at least one connection tab 3a.

 These solar cells 2 are arranged in the recesses 4 of a thermoplastic film 5 which can advantageously be transparent.

Said film 5 is inserted between two thermoplastic films 6 and 7. The first film 6 which covers the anterior faces of the solar cells 2, called "active faces", because they are subjected to solar radiation, is therefore transparent and advantageously constituted by the same material as the film 5. It is covered, on its outer face, by a rigid element 8 also transparent.

 The second film 7 covers the rear faces, called rear faces, of solar cells 2, said rear faces generally being provided with a contact pad covering them at least partially.

 This film 7 is advantageously constituted by the material used for making the film 5 and the film 6. It represents the first layer of a laminated sub-assembly 9 according to the invention.

 In addition to this film ~ 7, said sub-assembly 9 successively comprises a metal sheet 10 and a layer of plastic material 11, said metal sheet 10 and the layer of plastic material 11 being advantageously separated by a loose fabric 12 intended on the one hand, to make the sub-assembly 9 practically tear-proof and, on the other hand, to stiffen it slightly.

 The rigid and transparent element 8 can be a plastic material, for example made of polymethyl methacrylate, glass or sub-stancesvitrocriStallines.

 Advantageously, the thermoplastic films 6 and 7 as well as the film 5 are formed from the same substance, this substance being for example a synthetic resin such as polyvinyl chloride, a polyolefin, an acrylic resin, a silane or, preferably, the polyvinylbutyral.

 The metal sheet 10 having to be reflective, a metal such as aluminum or an aluminum-based alloy is chosen.

In this case, it is advantageous, for reasons of adhesion, to produce the plastic layer 11 in polyvinyl chloride.

 As shown in FIG. 3, the loose fabric 12 advantageously consists of a network with wide mesh of drawn fibers 13.

 During the rolling operation of the sub-assembly 9, said fibers 13 penetrate into the plastic layer 11 and are fixed to the latter; they also penetrate into the metal sheet 10 of small thickness and formed of a relatively malleable material.

 Said fibers 13 can be synthetic polyester or polyamide fibers, or also glass, carbon or boron fibers; they will advantageously be made of a material known commercially under the name of "nylon".

 The various plastic films or layers advantageously have a thickness of between 0.03 mm and 1.5 mm.

 To obtain the solar cell panel described above, it is preferable to divide the implementation of the method into two stages.

 The first step consists in creating the laminated sub-assembly 9 then, in the second step, there is on said sub-assembly the active portion of the panel made up of solar cells inserted in a thermoplastic film, then a thermoplastic film and the transparent rigid element. .

 With regard to the production of the laminated sub-assembly, it has been noted that the optimum forming temperature for plastics is around 2000 ° C., the temperature in the vicinity of which the material used for the production of the metal sheet also has good forming characteristics.

 The rolling of said subassembly is obtained by the methods commonly used in the production of plastic plastic laminates. These methods may include the use of adhesives, but in general, mechanical welding, called heat welding, is preferred at a temperature and pressure suitably determined. However, if an adhesive is required to bond the plastic-metal interfaces, an epoxy resin will advantageously be chosen.

 To facilitate welding with or without adhesive, pressure is advantageously applied which can be exerted by any suitable means, rollers, oil, compressed gas, ntc. This pressing operation can be carried out during the thermal phase and in particular at the end of the latter.

 During the laminate laminating operation, it is necessary to eliminate the gases occluded in and between the different layers: this is why a coarse vacuum or, more precisely, a subatmospheric pressure is applied during at least part of the treatments. . This rough vacuum can be applied before the thermal phase and / or during it, in particular at its beginning.

 Figures 4 and 5 show two devices for assembling the various elements constituting a solar panel.

It goes without saying that such devices can also be used for the production of the previously mentioned laminated sub-assembly.

 FIG. 4 represents an enclosure 20, an autoclave for example, in which, on the one hand, the glass plate 21, the first thermoplastic film 22 and the film 23 in which the solar cells 24 are inserted, are then arranged, d on the other hand, the second film 257 the metal sheet 26, the loose fabric 27 and the plastic layer 28 forming the sub-assembly 29.

 The assembly 30 thus formed is placed on the seat 31, which can be a series of rollers facilitating translation and it can be heated using the ramps shown at 32 and 33.

 The tubing 34 passing through a wall of the enclosure 20 makes it possible to bring gas into it or to evacuate it.

 At the periphery of the assembly 30 and resting on it, is disposed a chamber 35 connected to at least one tube 36 through which gas can be introduced or evacuated. This chamber can, for example, be a flexible pocket in which a vacuum is created: this pocket then has a homeomorphic shape with a hollow ring in which a bleeding has been practiced. The edges of this groove are supported at the periphery of the assembly 30 optionally by means of seals, not shown in the figure, which provide sealing.

 The first stage in the assembly of the panel consists first of all in creating, via the tubing 34, a coarse vacuum in the enclosure 20 and, via the tubing 36, a coarse vacuum in the chamber 35 corresponding to a pressure different from that existing in said enclosure 20 and one then begins to gradually increase the temperature. For example, the enclosure 20 is subjected to a pressure of less than 1000 pascals, 400 in particular, the chamber 35 being brought to a pressure of the order of 2000 pascals and the temperature is increased by 60 C / min.

 In order to eliminate the occluded gases, the assembly is kept for a time at a temperature tl lower than the welding temperature.

 The pressure in the enclosure 20 is then increased while maintaining the vacuum in the chamber 35 and the heating temperature is also increased.

 If the central film and the thermoplastic films are made of polyvinyl butyral, the temperature t 1 is of the order of 600 C, the pressure in the enclosure 20 can be raised to atmospheric pressure and the heating temperature is gradually increased to 1000 C, then 1200 C, 1400 C, etc. It is preferable not to exceed the temperature ~ of 2000 C. From 1000 C, the vacuum was broken in the chamber 36. When the necessary temperature is reached, the assembly is then gradually cooled.

 FIG. 5 represents another form of implementation of the method. The assembly 40, consisting of the glass sheet 41, the thermoplastic films 42 and 43, the central film 44, the solar cells 45 which are inserted therein, the metal sheet 46 and the plastic layer 47 with its mesh network 48, is introduced by means of rollers 49 into the enclosure 50 closed at its ends by the removable partitions 51a and 51b.

 The assembly can be heated by elements 52, 53a, 53b, and the enclosure can be put under rough vacuum by means of the tube 54.

 On the assembly 40 is supported a press 55 controlled by the axis 56.

 First, a coarse vacuum is created in enclosure 50 which is brought to a value of less than 1000 pascals, then the temperature is raised to 600 ° C. and then 800 ° C.

 At this time the press 55 is lowered on the assembly 40 by the action of the axis 56 and, under its action, the welding begins while the temperature rises. Before the temperature reached its maximum, the press 55 was reassembled.

 The last operation consists in gradually cooling the assembly in a neighboring box 57-.

Claims (26)

- CLAIMS  1.- Method of manufacturing a solar cell panel fcrmant a photoelectric battery and comprising a pl # ra # t of photocells connected together electrically and leading to electrical output connections immersed in a laminate comprising in particular a first film of a first transparent thermoplastic substance, a central film in a thermoplastic substance weldable to said first substance, said film comprising recesses in which said solar cells are arranged, one active face being turned towards said transparent film, a second film of a second weldable thermoplastic substance to the substance of said film, said method comprising a welding phase during which heat is applied, characterized in that said laminate comprises a single rigid element placed outside said first film, said element being transparent and weldable to said first film and in that q ue said laminate comprises at least one flexible metal sheet disposed outside of said second film and weldable thereto and a plastic layer disposed outside of said sheet and weldable thereto.  2.- Method according to claim 1, characterized in that said rigid and transparent material is glass.  3.- Method according to any one of claims 1 and 2, characterized in that said first thermoplastic substance is p # olyvinylbutyral.  4.- Method according to any one of claims 1 to 3, characterized in that said film is polyvinyl butyral.  5.- Method according to any one of claims 1 to 4, characterized in that said second film is polylrin 1-butyral.  6.- Method according to any one of claims 1 to 5, characterized in that said metal sheet is aluminum: .i- nium.  7.- Method according to any one of claims 1 to 5, characterized in that said metal sheet is made of an aluminum-based alloy.  8.- Method according to any one of claims l to ~, characterized in that said weldable plastic layer is polyvinyl chloride.  9.- Method according to any one of claims 1 to 8, characterized in that said laminate also comprises between said metal and said cuckold, a mesh network of drawn fibers.  10.- Method according to claim 9, characterized in that said mesh network is mainly made of a thermoplastic synthetic material.  11.- Method according to claim 10, characterized in that the synthetic material constituting the mesh network is a polyester.  12.- Method according to claim 10, characterized in that the synthetic material constituting the mesh network is a polyamide.  13.- Method according to claim 9, characterized in that said mesh network is mainly made of glass fibers.  14.- Method according to claim 9, characterized in that said mesh network is mainly made of fibers of a material chosen from a series comprising in particular carbon and boron.  15. Method according to any one of claims 1 to 14, characterized in that, during a first step, a subassembly comprising at least the plastic layer is created by hot rolling, the metal sheet and said second film, then in that during a second step, there is disposed against this sub-assembly thus laminated, said central film comprising in recesses the photoelectric cells joined in a network, said first film and said element rigid transparent and in this way performs the welding of the whole.  16.- Method according to claim 15, characterized in that the sub-assembly is laminated in an enclosure in which a vacuum has been previously created of a value less than 1000 pascals, said in # enclosure is then gradually brought to a temperature at most equal to 2000 C and normal atmospheric pressure before being cooled slowly.  17.- Method according to claim 15, characterized in that the welding of the laminated sub-assembly with the central film; the first film and the transparent rigid element is made in an enclosure in which a vacuum has been previously created of a value of less than 1000 pascals, said enclosure, gradually brought to a temperature at most equal to 2000 C and to atmospheric pressure normal, then being cooled slowly.  18.- Means for implementing the method according to one of claims 15 to 17, characterized in that it is constituted by a laminate comprising a polyvinyl butyral film, an aluminum foil, a layer of polyvinyl chloride .  19.- Means according to claim 18, characterized in that it comprises, between the aluminum layer and the polyvinyl chloride layer, a mesh network of drawn thermoplastic fibers.  20.- Means according to claim 18, characterized in that it comprises, between the aluminum layer and the polyvinyl chloride layer, a mesh network of drawn glass fibers.  21. Means according to claim 18, characterized in that it comprises, between the aluminum layer and the polyvinyl chloride layer, a mesh network of drawn fibers of a material chosen from a series comprising in particular carbon and the # bore.  22.- Solar panel characterized in that it comprises a rigid and transparent element, cells of which an active face is turned towards said transparent element and whose sides and rear face are surrounded by a thermoplastic substance welded to a sheet of metal, itself welded to at least one layer of plastic material and in that it is produced by the method according to one of claims 1 to 17.  23. Solar panel according to claim 22, characterized in that it comprises, between said metal sheet and said plastic layer, a mesh network of drawn thermoplastic fibers.  24.- solar panel according to claim 22, characterized in that it comprises, between said metal sheet and said plastic layer, a mesh network of glass fibers.  25.- solar panel according to claim 22, characterized in that it comprises, between said metal sheet and said layer of plastic material, a mesh network of fibers of a material chosen from a series comprising in particular carbon and boron .  26.- Solar panel according to one of claims 22 25, characterized in that said rigid and transparent element is glass, the thermoplastic substances in polyvinylbutyral, the metal sheet in aluminum and the plastic layer in polyvinyl chloride.