WO2013000949A1

WO2013000949A1 - Component for a photovoltaic module, photovoltaic module comprising said component, and method for realizing a photovoltaic module

Info

Publication number: WO2013000949A1
Application number: PCT/EP2012/062447
Authority: WO
Inventors: Roberto Levi Acobas
Original assignee: Printgraph Waterless S.P.A.
Priority date: 2011-06-28
Filing date: 2012-06-27
Publication date: 2013-01-03
Also published as: ITMI20111179A1

Abstract

A photovoltaic module (1) comprising at least one photovoltaic cell (2) encapsulated between a front encapsulation layer (3) and a rear encapsulation layer (4), and a support layer (5) applied to the rear encapsulation layer (4), the front encapsulation layer (3) and rear encapsulation layer (4) being made of material comprising thermoplastic polyurethane, and the support layer (5) being made of material comprising extruded thermoplastic polyurethane having a tensile modulus higher than that of the rear encapsulation layer (4) and directly joined to the rear encapsulation layer (4) without the interposition of adhesive.

Description

COMPONENT FOR A PHOTOVOLTAIC MODULE, PHOTOVOLTAIC MODULE COMPRISING SAID COMPONENT, AND METHOD FOR REALIZING A PHOTOVOLTAIC MODULE

DESCRIPTION

The present invention relates to a component for a photovoltaic module, a photovoltaic module which incorporates said component, and a method for realizing a photovoltaic module.

A photovoltaic module can be schematically described as a multilayered structure incorporating the photovoltaic cells.

Schematically, in its simplest version, a photovoltaic module in general comprises, from the outside to the inside, an outer layer, a front layer for encapsulating the photovoltaic cells, the photovoltaic cells, a rear layer for encapsulating the photovoltaic cells, and a support layer.

The support layer must have excellent resistance to water, heat and, more in general, to atmospheric agents.

The support layer must moreover have good mechanical properties, it must be able to prevent the entry of humidity and it must possess good dielectric properties and, naturally, a good ability to adhere to the rear encapsulation layer.

As a support layer, glass or a metal (such as aluminium) can generally be used and wide use is also made of polymer-based support layers which are in turn multilayered and generally comprise fluorinated polymers, polyethylene terephthalate (PET) and ethylene vinyl acetate (EVA).

Some examples of polymer-based materials for support layers are: TPT (Tedlar®,PET, Tedlar®), KPK (Kynar®,PET, Kynar®), TPE (Tedlar®,PET, EVA) and KPE (Kynar®,PET, EVA). Tedlar® and Kynar®, in particular, are registered trademarks of fluoropolymers made respectively by DuPont and Arkema.

Those presented are only a few examples of support layers, given that a large variety of support layers for photovoltaic applications are commercially available. For example, in this type of application PEN (polyethylene naphthalate) and polycarbonate can also be used, and furthermore the structure of the support layer can include as said a further multilayering in which layers of aluminium are also present.

Though they are sufficiently effective, the structural complexity of these support layers necessarily leads to production difficulties and high costs.

Moreover, in many cases problems may arise due to the loss of adhesion at least between the support layer and the rear encapsulation layer.

The front and rear encapsulation layers must protect the cells from mechanical strains and humidity, isolate them electronically and have a suitable ability to adhere to the outer layer and support layer.

The polymer-based material most widely used at present for the realization of encapsulation layers is EVA.

Generally speaking, to assemble the photovoltaic module the EVA encapsulation layers are perimetrally welded to each other, with the interposition of the photovoltaic cells, during the lamination step, which usually takes place under a vacuum at a temperature of around 150°C with cycles that can reach 20-30 minutes.

Without doubt, the use of EVA as the material for the encapsulation layers has long ensured successful assembly of the photovoltaic module; however, it poses several problems, such as yellowing and deterioration of the material caused by aging, as well as extended production times due to the need to crosslink the material.

Among the possible replacement materials, at present there is great interest in the use of polyurethane, which displays better stability on aging and, as it does not require crosslinking, ensures a reduction in the length of the production process. If selected with suitable mechanical and physical-chemical properties, polyurethane can also be suitable for use in the support layer. The outer layer of a photovoltaic module, generally made of glass, has the task of protecting the photovoltaic cell while letting light pass through. In some constructions the outer layer also has a multilayered structure in which an outer polymer-based protective film is present.

DE20220444 discloses a photovoltaic module construction in which there is provided a layer of special adhesive thermoplastic polyurethane which encapsulates the photovoltaic cells and is bonded to a rear support layer and a front layer exposed to solar radiation. Said document furnishes a solution for the technical problem of the delamination of the layers by providing, for the encapsulating layer, a special adhesive material made of TPU which is suitable for being joined both to the front layer and rear layer, while in order to lend the necessary structural rigidity it proposes increasing the thickness of the layers or providing additional reinforcement layers or support layers with multiple walls. The technical task the present invention has set itself is therefore to realize a photovoltaic module and provide a method for the realization thereof, which allows the aforementioned technical drawbacks of the prior art to be eliminated. Within the scope of this technical task, one object of the invention is to realize a photovoltaic module with a multilayer structure that exhibits improved resistance to debonding.

Another object of the invention is to realize a photovoltaic module with a multilayer structure that is extremely simple, functional, resistant and long-lasting. Another object of the invention is to realize a simple, economical and highly productive method for realizing a photovoltaic module with a multilayer structure. The technical task, as well as these and other objects according to the present invention are achieved by realizing a photovoltaic module of the type comprising at least one photovoltaic cell encapsulated between a front encapsulation layer and a rear encapsulation layer, and a support layer applied to the rear encapsulation layer, characterized in that said front encapsulation layer and said rear encapsulation layer are made of material comprising thermoplastic polyurethane, and in that said support layer is made of material comprising extruded thermoplastic polyurethane, has a tensile modulus higher than that of said rear encapsulation layer, and is directly joined to said rear encapsulation layer without the interposition of adhesive.

The present invention confronts the technical problem of furnishing an alternative construction for a photovoltaic module suitable for imparting the necessary structural rigidity and resistance to debonding and, unlike DE20220444, resolves it by providing a thermoplastic polyurethane -based material for the front encapsulation layer, rear encapsulation layer and support layer so that they exhibit an intrinsic physical-chemical affinity for reciprocal bonding, which can consequently also be direct without the interposition of an adhesive, and by providing for an elastic modulus for the support layer that is greater than that of the rear encapsulation layer so as to impart the necessary structural rigidity.

The present invention also discloses a method for realizing a photovoltaic module, characterized in that a front encapsulation layer made of material comprising thermoplastic polyurethane for at least one photovoltaic cell, a rear encapsulation layer made of material comprising thermoplastic polyurethane for said at least one photovoltaic cell and a support layer made of extruded material comprising thermoplastic polyurethane having a tensile modulus higher than that of the rear encapsulation layer are realized, said at least one photovoltaic cell is encapsulated by joining together perimeter strips of the front and rear encapsulation layers which circumscribe said at least one solar cell, and the support layer and the rear encapsulation layer are directly joined to each other without the interposition of adhesive.

Finally, the present invention discloses a multilayer component for a photovoltaic module, characterized in that it comprises a front encapsulation layer for at least one photovoltaic cell, a rear encapsulation layer for said at least one photovoltaic cell, and an extruded support layer directly applied to the rear encapsulation layer without the interposition of adhesive, said front encapsulation layer, said rear encapsulation layer and said support layer being made of material comprising thermoplastic polyurethane, said support layer being made of thermoplastic polyurethane having a tensile modulus higher than that of said rear encapsulation layer.

One of the salient aspects of the invention consists in the fact that the extruded thermoplastic polyurethane used for the support layer has a Shore-D hardness advantageously greater than 75 so as to be able to perform the function it is intended for.

The extrusion of a thermoplastic polyurethane layer having such a hardness serves to overcome a technical disadvantage which would impose other production techniques such as, for example, injection moulding.

The adoption, not obvious, of a flat film extrusion (cast process) or calendaring process to form a thermoplastic polyurethane layer with a high degree of hardness advantageously makes it possible to have a continuous production system and a faster photovoltaic module production process without the need to modify the present equipment.

Other features of the present invention are defined, moreover, in the subsequent claims.

Additional features and advantages of the invention will be more apparent from the description of a preferred, but not exclusive, embodiment of the photovoltaic module according to the invention, illustrated by way of non-restrictive example in the appended drawing, in which:

figure 1 schematically shows the multilayer structure of the photovoltaic module. With reference to the cited figure, a photovoltaic module indicated overall with the reference number 1 is shown. The photovoltaic module 1 in the minimum configuration comprises one or more interconnected photovoltaic cells 2, a front encapsulation layer 3 for the photovoltaic cells 2, a rear encapsulation layer 4 for the photovoltaic cells 2, and an extruded support layer 5 applied to the rear encapsulation layer 4.

In the version illustrated and described there is also present an outer layer 6, whose function, in other versions of the photovoltaic module not shown, can be performed directly by the front encapsulation layer.

Advantageously, the rear encapsulation layer 4 and support layer 5 are made of material comprising thermoplastic polyurethane so as to exhibit an intrinsic chemical compatibility for reciprocal adhesion.

In particular, the support layer 5 is made of thermoplastic polyurethane characterized by a tensile modulus that is higher than that of the rear encapsulation layer 4.

Preferably, the thermoplastic polyurethane of both the rear encapsulation layer 4 and the support layer 5 is aliphatic based.

Preferably, the front encapsulation layer 3 is likewise made of material comprising thermoplastic polyurethane so as to exhibit an intrinsic chemical compatibility with the rear encapsulation layer 4 for reciprocal adhesion.

In particular, the front encapsulation layer 3 and rear encapsulation layer 4 are made of the same material.

In practice it has shown to be convenient to provide a Shore-D hardness greater than 75 for the support layer 5, preferably E-modulus 2100 MPa +/- 30% according to the IS0527-2/1A/1 test method.

For the rear encapsulation layer 4, in contrast, it has shown in practice to be convenient to provide for a Shore-D hardness of less than 70.

The thermoplastic polyurethane used at least for the rear encapsulation layer 4 and in particular also for the front encapsulation layer 3 preferably has good light transmission, in the range of 350nm to 1150nm. The front and rear encapsulation layers 3 and 4 naturally project beyond the perimeter profile of the layer of photovoltaic cells 2 so that they can be joined to each other by direct contact along their perimeter strips 8, which circumscribe the layer composed by the photovoltaic cells 2.

The method for realizing the photovoltaic module 1 preliminarily provides for the realization of a component 7 formed by bonding the support layer 5 with the rear encapsulation layer 4.

Subsequently, the layer of photovoltaic cells 2 is interposed and incorporated between the front encapsulation layer 3 and the rear encapsulation layer 4, which as noted above are reciprocally joined along their perimeter strips 8.

The photovoltaic module 1 is then completed with the application of the outer layer 6, which, alternatively, can also be preassembled with the front encapsulation layer 3.

In a first preferred embodiment of the component 7 the rear encapsulation layer 4 and the support layer 5 are produced by extrusion followed by continuous hot bonding.

In a second preferred embodiment of the component 7 the rear encapsulation layer 4 and the support layer 5 are extruded one on top of the other successively.

In a third preferred embodiment of the component 7 the rear encapsulation layer 4 and the support layer 5 are coextruded.

Preferably, in order to have a continuous production system and a continuous photovoltaic module production process, in addition to the support layer and the rear encapsulation layer, the front encapsulation layer, too, is produced by extrusion.

A non-restrictive example of a process for realizing the component 7 could be the following.

A support layer 5 made of aliphatic polyurethane produced by Lubrizol and characterized by a high tensile modulus is obtained by extrusion in a thickness of 350 μιη. Subsequently, one side of said support layer 5 is used as a support for the extrusion of a 0.45 mm thick rear encapsulation layer 4 of softer aliphatic polyurethane Estane AG-8451, again produced by Lubrizol.

With the present invention it is thus possible to exploit the intrinsic chemical compatibility between the support layer 5 and the rear encapsulating layer 4 in order to ensure that the problems of adhesion between the two layers are overcome while avoiding specific treatments. Furthermore, it is possible to speed up the normal photovoltaic module production process by bonding, in a previous step and in a continuous manner, the rear encapsulation layer with the rear support layer. More generally speaking, within the scope of the invention it is also possible to envisage the use of additives of varying nature depending upon the specific applicative need, so as to improve the physical-chemical properties, particularly the optical properties, of the layers, or to improve the processability thereof; in the case of the support layer, moreover, it is possible to add organic and/or inorganic fillers to the polyurethane used in order to obtain the mechanical properties suited to its use.

The component for a photovoltaic module, the photovoltaic module and the method for the realization thereof thus conceived are susceptible of numerous modifications and variations, all falling within the scope of the inventive concept; moreover, all the details may be replaced with other technically equivalent elements.

In practice, the materials used, as well as the dimensions, can be any whatsoever according to need and the state of the art.

Claims

1. A photovoltaic module (1) of the type comprising at least one photovoltaic cell (2) encapsulated between a front encapsulation layer (3) and a rear encapsulation layer (4) , and a support layer (5) applied to the rear encapsulation layer (4), characterized in that said front encapsulation layer (3) and said rear encapsulation layer (4) are made of material comprising thermoplastic polyurethane, and in that said support layer (5) is made of material comprising extruded thermoplastic polyurethane, has a tensile modulus higher than that of said rear encapsulation layer (4), and is directly joined to said rear encapsulation layer (4) without the interposition of adhesive.

2. The photovoltaic module (1) according to the preceding claim, characterized in that the extruded thermoplastic polyurethane used for the support layer (5) has Shore-D hardness greater than 75.

3. The photovoltaic module (1) according to either of the preceding claims, characterized in that said thermoplastic polyurethane of said rear encapsulation layer (4) and of said support layer (5) is aliphatic based.

4. The photovoltaic module (1) according to any of the preceding claims, characterized in that it comprises an external layer (6) applied to the front encapsulation layer (3).

5. The photovoltaic module (1) according to any of the preceding claims, characterized in that the front and rear encapsulation layers (3, 4) are made of the same material.

6. The photovoltaic module (1) according to any of the preceding claims, characterized in that the support layer (5) has an E-modulus of 2100 MPa +/- 30% according to the IS0527-2/1 A/1 test method.

7. The photovoltaic module (1) according to any of the preceding claims, characterized in that the thermoplastic polyurethane used for the rear encapsulation layer (4) has a Shore-D hardness of less than 70.

8. The photovoltaic module (1) according to any of the preceding claims, characterized in that the thermoplastic polyurethane used at least for the rear encapsulation layer (4) has a light transmission within a wavelength range of 350nm to 1150nm.

9. The photovoltaic module (1) according to any of the preceding claims, characterized in that the polyurethane used in the support layer (5) is additioned with organic and/or inorganic fillers to obtain the mechanical properties suited to its use.

10. The photovoltaic module (1) according to any of the preceding claims, characterized in that the support layer (5) and/or the rear encapsulation layer (4) have additives of a different nature depending upon the specific applicative need, so as to improve their physical-chemical properties, particularly the optical properties.

11. A method for realizing a photovoltaic module (1), characterized in that a front encapsulation layer (3) made of material comprising thermoplastic polyurethane for at least one photovoltaic cell (2), a rear encapsulation layer (4) made of material comprising thermoplastic polyurethane for said at least one photovoltaic cell (2) and a support layer (5) made of material comprising extruded thermoplastic polyurethane having a tensile modulus higher than that of the rear encapsulation layer (4) are realized, said at least one photovoltaic cell (2) is encapsulated by joining together perimeter strips (8) of the front and rear encapsulation layers (3, 4) which circumscribe said at least one solar cell (2), and the support layer (5) and the rear encapsulation layer (4) are directly joined to each other without the interposition of adhesive.

12. The method for realizing a photovoltaic module (1) according to the preceding claim, characterized in that said rear encapsulation layer (4) and said support layer (5) are produced by extrusion followed by continuous hot bonding.

13. The method for realizing a photovoltaic module (1) according to claim 11, characterized in that said rear encapsulation layer (4) and said support layer (5) are extruded one on top of the other successively.

14. The method for realizing a photovoltaic module (1) according to claim 11, characterized in that said rear encapsulation layer (4) and said support layer (5) are coextruded.

15. A multilayer component (7) for a photovoltaic module (1), characterized in that it comprises a front encapsulation layer (3) for at least one photovoltaic cell (2), a rear encapsulation layer (4) for said at least one photovoltaic cell (2), and a support layer (5) directly applied to the rear encapsulation layer (4) without the interposition of adhesive, said front encapsulation layer (3), said rear encapsulation layer (4) and said support layer (5) being made of material comprising thermoplastic polyurethane, said support layer (5) being made of extruded thermoplastic polyurethane having a tensile modulus higher than that of said rear encapsulation layer (4).