EP2289111A2

EP2289111A2 - Light, rigid, self-supporting solar module and method for the production thereof

Info

Publication number: EP2289111A2
Application number: EP09761413A
Authority: EP
Inventors: Hubert Ehbing; Gunther Stollwerck; Dirk Wegener; Jens Krause; Elke Springer; Heike Schmidt; Frank Schauseil
Original assignee: Bayer MaterialScience AG
Current assignee: Bayer Intellectual Property GmbH
Priority date: 2008-06-12
Filing date: 2009-06-03
Publication date: 2011-03-02
Also published as: CN102067329A; WO2009149850A3; MX2010013465A; WO2009149850A2; CA2727413A1; AU2009256920A1; IL209544A0; JP2011523221A; DE102009014348A1; BRPI0915003A2; US20110155222A1; KR20110014198A

Abstract

The solar module according to the invention consists of a transparent adhesive layer (1), in which the solar cells (3) that are interconnected by cell connectors (2) are embedded. A transparent, UV stable, thin front layer (4), composed for example of a thin pane of glass, is located above said adhesive layer. The supporting sandwich element (5), consisting of a nucleic layer (6) and glass fibre layers (7) bonded by means of polyurethane is located on the rear face. Fastening elements (8) and an electric socket (9) are integrated into the supporting sandwich element. A barrier film (10), which prevents the entry of water and oxygen, adjoins the sandwich element. The solar module has peripheral edge protection (11) consisting of elastomeric polyurethane, which prevents the lateral penetration of water, dirt and oxygen. The invention also relates to a method for producing the solar module.

Description

Lightweight, rigid and self-supporting solar module and a method for its production

The present invention relates to a photovoltaic solar module and a method for its production.

Solar modules are components for direct generation of electricity from sunlight. Key factors for a cost-efficient generation of solar power are the efficiency of the solar cells used, as well as the manufacturing costs and the durability of the solar modules.

A solar module usually consists of a framed composite of glass, interconnected solar cells, an embedding material and a backside construction. The individual layers of the

Solar modules have to fulfill the following functions.

The front glass protects against mechanical and weather influences. It must have the highest transparency in order to minimize absorption losses in the optical spectral range of 300 nm to 1150 nm and thus efficiency losses of the silicon solar cells usually used for power generation. Usually hardened, low-iron white glass

(3 or 4 mm thick) whose transmittance in the above spectral range is 90 to 92%. Furthermore, the glass provides a significant contribution to the rigidity of the module.

The embedding material (usually EVA (ethyl vinyl acetate) films used) is used for bonding the entire module network. EVA melts during a lamination process at about 150 ⁰ C, flows into the interstices of the soldered solar cells and is thermally crosslinked. A

Formation of air bubbles, resulting in reflection losses, is avoided by lamination under vacuum.

The back of the module protects the solar cells and the embedding material from moisture and oxygen. In addition, it serves as mechanical protection against scratching etc. when mounting the solar modules and as electrical insulation. As rear construction, another glass or a composite foil can be used. Essentially, the variants PVF (polyvinyl fluoride) -PET (polyethylene terephthalate) PVF or PVF aluminum PVF are used.

The encapsulating materials used in solar module construction must in particular have good barrier properties against water vapor and oxygen. Water vapor or oxygen does not attack the solar cells themselves, but causes corrosion of the metal contacts and chemical degradation of the EVA embedding material. A destroyed solar cell contact leads to a complete failure of the module, since normally all solar cells in a module are electrically connected in series. A degradation of the EVA is shown by a the module, combined with a corresponding reduction in power through light absorption and a visual deterioration. Today, about 80% of all modules are encapsulated with one of the described composite foils on the back, and about 15% of the solar modules use front and back glass. In this case, as embedding material instead of EVA partially highly transparent, but only slowly (several hours) hardening casting resins

Commitment.

In order to achieve competitive electricity generation costs of solar power despite the relatively high investment costs, solar modules must achieve long operating times. Today's solar modules are therefore designed for a service life of 20 to 30 years. In addition to high weathering stability, high demands are placed on the thermal stability of the modules, whose temperature during operation can fluctuate cyclically between 80 ° C at full solar irradiation and temperatures below the freezing point. Accordingly, solar modules undergo extensive stability tests (standard tests to IEC 61215 and IEC 61730), which include weather tests (UV irradiation, damp heat, temperature change), but also hail impact tests and tests of electrical insulation capacity.

With 30% of the total costs, a relatively high proportion of the total costs for photovoltaic modules is attributable to module production. This large portion of module manufacturing is due to high material costs (e.g., backside multilayer film) and long process times, i. H. low productivity conditions. The individual layers of the modular composite described above are still frequently assembled and aligned by hand. In addition, the relatively slow lead

Melting of the EVA hot melt adhesive and the lamination of the module assembly at about 150 ⁰ C and under vacuum at cycle times of about 20 to 30 minutes per module.

Due to the relatively thick front glass pane, conventional solar modules also have a high weight, which in turn makes stable and expensive holding structures necessary. Also, the heat dissipation is solved unsatisfactory in today's solar modules. At full solar irradiation, the modules heat up to 80 ⁰ C, which leads to a temperature-related deterioration of the solar cell efficiency and thus ultimately to an increase in the cost of solar power.

In the prior art solar modules are mainly used with an aluminum frame. Although it is a light metal, but its weight makes a not insignificant contribution to the total weight. This is especially for larger modules

Disadvantage that requires elaborate holding and mounting structures.

In order to prevent the ingress of water and oxygen, said aluminum frames have an additional seal on their inner side facing the solar module. Furthermore disadvantageous added that aluminum frames are made of rectangular profiles and therefore is severely limited in terms of their shape.

In order to reduce the solar module weight, to avoid an additional sealing material and to increase the design freedom, US Pat. No. 4,830,038 and US Pat. No. 5,008,062 describe the attachment of a plastic frame around the relevant solar module, which is produced by the RIM process

(Reaction Injection Molding) is obtained.

Preferably, the polymeric material used is an elastomeric polyurethane. The said polyurethane should preferably have an E modulus in a range of 200 to 10,000 psi (corresponding to about 1.4 to 69.0 N / mm ² ).

To reinforce the frame, various possibilities are described in these two patents. Thus, reinforcing members of, for example, a polymeric material, steel, or aluminum may be incorporated into the frame when formed. Also, fillers can be incorporated into the frame material. These may be, for example, platelet-type fillers such as the mineral wollastonite or needle-like / fibrous fillers such as glass fibers.

Similarly, DE 37 37 183 Al also describes a method for producing the plastic frame of a solar module, wherein the Shore hardness of the material used is preferably adjusted so that a sufficient rigidity of the frame and an elastic receptacle of the solar generator is ensured.

The modules described above are erected by means of stand constructions or, for example, mounted on roof structures. They require a certain modulus rigidity, which is adversely affected by a (plastic) frame and the relatively heavy, about 3 to 4 mm thick front glass. In addition, the front screen already has a certain absorption due to its thickness, which in turn adversely affects the efficiency of the solar module.

Foil modules are the embedding of solar cells between two plastic films, possibly also between a front, translucent film and a flexible sheet (aluminum or stainless steel) on the back. For example, "UNIsolar ^® " film laminates consist of thin, thin-film silicon vapor-deposited on thin stainless steel sheet, embedded between two plastic sheets, which then have to be applied to a rigid support structure such as sheet roofs or roof elements

To be glued to metal sandwich composites. DE 10 2005 032 716 A1 describes a flexible solar module that subsequently has to be applied to a rigid support structure. The disadvantage here is the additional step, the subsequent bonding with a support structure. Due to the different coefficients of thermal expansion of the plastic frame and the glass occurred in the past again and again delamination of moisture penetration into the inner region of the solar module, which ultimately led to the destruction of the module.

It is therefore an object of the present invention to provide a solar module which avoids these disadvantages of the prior art.

The solar module should have the lowest possible basis weight and at the same time be as rigid as possible, so that no or only a very simple support or mounting structure is required and it can be handled easily. Furthermore, the solar module should have sufficient composite long-term stability to prevent delamination and / or moisture from entering.

This object has been achieved by the photovoltaic solar module according to the invention.

The invention relates to a solar module with a structure structure

a) a transparent light-emitting layer A) in the form of a glass pane or a plastic layer,

b) an adhesive layer B) as an intermediate layer and solar cells embedded therein,

c) a sandwich element C) comprising at least one core layer and at least one outer layer located on each side of the core layer, optionally with attachment and electrical connection elements.

It has surprisingly been found that a photovoltaic solar module with such a structure structure combines the desired properties in itself.

Due to its sufficiently high bending stiffness, such a construction has sufficiently high stability. Due to this sufficiently high rigidity, the solar module is easy to handle and does not bend even after a long time (for example, with a spaced attachment to non-vertical surfaces).

In addition, the difference of the coefficient of thermal expansion of the sandwich element C) compared to that of the transparent layer A) and that of the solar cells is very small, so that mechanical stresses hardly occur and the risk of delamination is very low.

The sandwich element C) of the solar module according to the invention further serves to seal the solar module against external influences. With an additional barrier layer, for example in the form of a barrier film, this seal can be additionally optimized. It is preferably applied directly in the production of the sandwich element and can be located both on the side facing away from the adhesive layer of the sandwich element and between the adhesive layer and sandwich element. The barrier film can be inserted, for example, in the pressing tool before the sandwich element is inserted. The barrier layer can also be produced by InMold coating by spraying the barrier layer into the pressing tool before inserting the sandwich element. Alternatively, the barrier film can also be subsequently glued to the sandwich element. A subsequent encapsulation of the sandwich element with a barrier layer is also possible.

In addition, via the sandwich element C), the attachment of the solar module to the respective substrate (for example, house roofs or walls) done. The solar module therefore preferably has in the sandwich element already integrated fastening means, recesses and / or holes, via which an attachment to the respective substrate can take place. Furthermore, the sandwich element preferably receives the electrical connection elements, so that subsequent attachment, e.g. can be omitted from junction boxes.

The sandwich element C) is preferably based on polyurethane (PUR), since in this case particularly high bending stiffnesses are obtained. Such a sandwich element C) consists of a core layer and on both sides of the core layer arranged fiber layers, which are impregnated with a polyurethane resin. For the production of the sandwich element with the mentioned structure, the known methods come into question: NafpurTec method, LFI / FipurTec method or

Interwet process, CSM process and lamination process.

The polyurethane resin used can be obtained by reacting

1) at least one polyisocyanate,

2) at least one polyol component having an average OH number of 300 to 700 and containing at least one short-chain and one long-chain polyol, the starting polyols having a functionality of 2 to 6,

3) water,

4) activators,

5) stabilizers,

6) optionally auxiliaries, separating agents and / or additives. AIs long-chain polyols are preferably suitable polyols having at least two to not more than six isocyanate-reactive H atoms; Polyester polyols and polyether polyols which have OH numbers of from 5 to 100, preferably from 20 to 70, particularly preferably from 28 to 56, are preferably used.

Preferred short-chain polyols are those which have OH numbers of from 150 to 2,000

250 to 1500, more preferably from 300 to 1100 have.

According to the invention, preference is given to using higher-nuclear isocyanates of the diphenylmethane diisocyanate series (pMDI types), their prepolymers or mixtures of these components.

Water is used in amounts of 0 to 3.0, preferably 0 to 2.0 parts by weight per 100 parts by weight of polyol formulation (components 2) to 6)).

For catalysis, the usual activators for the blowing and crosslinking reaction, e.g. Amines or metal salts used.

Suitable foam stabilizers are preferably polyether siloxanes, preferably water-soluble components. The stabilizers are usually used in amounts of from 0.01 to 5 parts by weight, based on 100 parts by weight of the polyol formulation (components 2) to 6)).

The reaction mixture for the preparation of the polyurethane resin can optionally be added to auxiliaries, release agents and additives, for example surface-active additives, such as. Emulsifiers, flame retardants, nucleating agents, antioxidants, lubricants and mold release agents, dyes, dispersants, blowing agents and pigments.

The components are reacted in amounts such that the equivalence ratio of the NCO groups of the polyisocyanates 1) to the sum of the isocyanate-reactive hydrogens of components 2) and 3) and optionally 4), 5) and 6) 0.8: 1 to 1.4: 1, preferably 0.9: 1 to 1.3: 1.

For example, rigid foams, preferably polyurethane (PUR) or polystyrene foams, Balsahölzer, corrugated sheets, spacers (for example, from large-pored open plastic foams), honeycomb structures, such as metals, impregnated papers or plastics, or from the state The technique (eg Klein, B., lightweight construction, Verlag Vieweg, Braunschweig / Wiesbaden, 2000, page 186 ff) known sandwich core materials are used. Also particularly preferred are moldable, in particular thermoformable, rigid foams (eg rigid polyurethane foams) and honeycomb structures which enable a curved or a three-dimensional shaping of the solar module to be produced. Furthermore, especially hard foams with good insulating properties are preferred. The Element C), in particular the core layer also serves for the isolation, in particular the thermal insulation.

As fiber material for the fiber layers, glass fiber mats, glass fiber mats, Glasfaserwirrlagen, glass fiber fabric, cut or ground glass or mineral fibers, natural fiber mats and knitted fabrics, cut natural fibers, as well as fiber mats, nonwovens and -wirirke based on

Polymer, carbon or aramid fibers and their mixture can be used.

The production of the sandwich elements C) can be carried out so that first of all a fibrous layer is applied to the core layer on both sides, which is acted upon by the polyurethane starting components 1) to 6). Alternatively, the fiber reinforcing material can also be incorporated with the polyurethane raw materials 1) to 6) by suitable mixing head technology. The thus prepared blank from the three layers is transferred to a mold and the mold is closed. The reaction of the PUR components bonds the individual layers together.

The sandwich element C) is characterized by a low basis weight of 1500 to 4000 g / m ² and a high flexural strength of 0.5 to 5 × 10 ⁶ N / mm ² (based on 10 mm sample width).

In particular, the sandwich element in comparison to other supporting structures made of plastics or metals, such as plastic blends (polycarbonate / acrylonitrile-butadiene-styrene, polyphenylene oxide / polyamide), sheet-molding compound (SMC) or aluminum and steel sheet at comparable bending stiffness significantly lower basis weights ,

The transparent layer A) may consist of the following materials: glass, polycarbonate, polyester, polymethyl methacrylate, polyvinyl chloride, fluorine-containing polymers, epoxies, thermoplastic polyurethanes or any combination of these materials. Furthermore, it is also possible to use transparent polyurethanes based on aliphatic isocyanates. As Isocyante HDI (hexamethylene diisocyanate), EPDI (isophorone diisocyanate) and / or H 12-MDI (saturated Methylendiphenyldiisocyanat) are used. Come as a polyol component

Polyether and / or polyester polyols for use and chain extenders, preferably aliphatic systems are used.

The layer A) can be designed as a plate, film or composite film. On the transparent layer A) may preferably be applied a transparent protective layer, for example in the form of a lacquer or a plasma layer. By such a measure, the transparent layer A) could be set softer, whereby voltages in the module can be further reduced. Protection against external influences would take over the additional protective layer.

The adhesive layer B) has the following properties: high transparency in the range of 350 nm to 1 150 nm, good adhesion to silicon and to the material of the transparent layer A) and to the sandwich element C). The adhesive layer may consist of one or more adhesive films, which are laminated to the layer A) and / or the sandwich element.

The adhesive layer B) is soft to compensate for the stresses caused by the different thermal expansion coefficients of transparent layer A), solar cells and sandwich element C). The adhesive layer B) is preferably made of a thermoplastic polyurethane, which may optionally be colored.

The coefficient of thermal expansion of sandwich element C) is preferably 10 to 20 × 10 ^-6 K ^-1 , depending on the sandwich composition and fiber reinforcement.

The solar module preferably has a circumferential polyurethane frame, which can be retrofitted by RIM, R-RIM, S-RIM, RTM, spraying or casting.

Another object of the invention is a method for producing the solar modules according to the invention, characterized in that

i) a sandwich element C) comprising at least one core layer and at least one outer layer located on each side of the core layer and optionally with

Mounting and electrical connection elements is presented,

ii) an adhesive layer B) in the form of a plastic film or as a mass is applied to the sandwich element C),

iii) the solar cells are placed on the adhesive layer B) or embedded in the adhesive layer B) or a solar film is applied to the adhesive layer B),

iv) a transparent plastic film optionally having an adhesive layer B), and / or a transparent layer A) is applied to the solar cells,

v) if appropriate, the abovementioned layer structure is optionally pressed in with the effect of temperature and / or optionally under application of a vacuum.

The sandwich element C) can be presented either as a finished pressed or bonded sandwich element or as a non-bonded sandwich element in which the layers have not yet been pressed or joined.

The method can also be carried out by initially introducing the transparent layer A) (eg a plastic film). Subsequently, an adhesive layer B) in the form of a Plastic film or as a mass applied to the layer A). The solar cells or the solar film are placed on the adhesive layer B) or embedded in the adhesive layer B). Subsequently, a sandwich element C), which optionally has an adhesive layer B), is applied. Preferably, then optionally pressed under the influence of temperature.

The method can also be carried out so that initially a finished film module from the

Layers A) and B), which already has the solar cells or the solar layer, is presented in a pressing tool. Preferably, this film module has an adhesive layer B), preferably of thermoplastic polyurethane, on the side facing the sandwich element to be applied.

Alternatively, a not yet connected film module can be submitted by initially a transparent layer A) is submitted. Subsequently, an adhesive layer B) in the form of a plastic film or as a mass on the transparent layer A) is applied. Subsequently, the solar cells or the solar film are placed on the adhesive layer B) or embedded in the adhesive layer B). Subsequently, if necessary, a further adhesive layer B) - preferably applied from a thermoplastic polyurethane.

On the presented, finished connected film module or on the only presented, not yet connected film module then also preferably not yet pressed sandwich element (preferably a PUR sandwich) is placed. Subsequently, if necessary, the mixture is compressed while increasing the temperature. The pressing process hardens the sandwich element and connects it to the film module in the same work step. Will not be connected

Submitted film module, the pressing operation is used simultaneously to connect the laminate layers with each other.

In addition, additional functional layers and elements can be inserted before the pressing process and connected to the solar module by the pressing process. For example, between the layer B) and the sandwich element C) a barrier foil against oxygen and moisture (e.g.

PVF (polyvinyl fluoride) -PET (polyethylene terephthalate) PVF or PVF aluminum PVF composite films). Optionally, these barrier films in turn have an adhesive layer for good adhesion to the sandwich element C). Alternatively, these barrier films can also be attached to the rear side (the side facing away from the light) of the sandwich element C). Furthermore, there is the possibility of improving the thermal insulation, on the back of the sandwich element C) to install an additional insulation layer, for example, a rigid polyurethane foam.

In a further embodiment, in the production of the sandwich element C) media lines can be pressed with. These lines can be made of plastic or plastic Copper exist. Preferably, these lines are placed close to the layer B) and can be used for cooling the solar module via a heat dissipating medium (eg water). By an internal cooling of the solar module, the electrical efficiency can be increased.

The solar modules according to the invention generate electricity and at the same time act as an insulating layer, so that they can also be used well as a roofing. They are very light and stiff at the same time. By pressing, they can also be converted into three-dimensional structures, so that they can be well adapted to vogegebene roof structures.

Reference to the following Figure 1, the invention is further exemplified. In FIG. 1, the arrangement consists of a transparent adhesive layer 1, in which the cell connectors 2 are connected

Solar cells 3 are embedded. Above it is a transparent, UV-stable, thin front layer 4, consisting for example of a thin glass pane. On the back side there is the load-bearing sandwich element 5, consisting of a core layer 6 and glass fiber layers 7 bonded by polyurethane. Fastening elements 8 and an electrical junction box 9 are integrated into the load-bearing sandwich element. The sandwich element is followed by a barrier film 10, which prevents the entry of water and oxygen. The solar module has a circumferential edge protection 11 made of elastomeric polyurethane, which prevents lateral penetration of water, dirt and oxygen.

example

It was a solar module made of the following individual components. The front layer used was a 125 μm thick polycarbonate film (type ^Makrofol® DE 1-4 from Bayer MaterialScience AG, Leverkusen). Two 480 .mu.m thick EVA films were used (type Vista ^® from Solar Etimex, Rottenacker) as an adhesive layer. As a sandwich element Baypreg ^® sandwich was used.

For this purpose, first a paper honeycomb of the type Testliner 2 (A-wave, Wackenicke 4.9-5.1 mm from Wabenfarbik, Chemnitz) on both sides with a random fiber mat type M 123 with a weight per unit area of 300 g / m ² (the company Vetrotex , Herzogenrath). 300 g / m ^{2 of} a reactive polyurethane system were then sprayed on both sides with a high-pressure processing machine on both sides. It became a polyurethane system of Bayer

Used Material Science AG, Leverkusen consisting of a polyol (Baypreg ^® VP.PU 01 IF 13) and an isocyanate (Desmodur ^® VP.PU 08IF01) in a mixing ratio of 100 to 235.7 (code 129). The structure of the paper honeycomb and the polyurethane fiber-coated random fiber mats was pressed in a tempered at 130 ⁰ C tool 90 seconds to a 10 mm thick Baypreg ^® -Sandwich composite.

The individual components in the order polycarbonate film, EVA film, 4 silicon solar cells, EVA film and finally the Baypreg ^® sandwich were combined into a laminate and in a vacuum laminator (NPC, Tokyo, Japan) at 150 ⁰ C for 6 minutes evacuated and then pressed for 7 minutes at 1 bar pressure to a solar module.

The solar module thus produced was in a solar simulator under a standard spectrum

(AM l, 5g conditions). The un-weathered module had an efficiency of 13.4% (+/- 0.5%). Subsequently, in accordance with IEC 61215, a climate change test was carried out with the module. 302 cycles were cycled (between -40 ⁰ C and + 85 ° C). After this weathering, the efficiency measured in the solar simulator was 12.8% (+/- 0.5%).

Claims

claims

1. Solar module constructed from

b) an adhesive layer B) as an intermediate layer with solar cells embedded therein,

c) a sandwich element C) comprising at least one core layer and at least one outer layer located on each side of the core layer and optionally with fastening and electrical connection elements.

2. Solar module according to claim 1, characterized in that the layer structure comprises a frame made of plastic.

3. A process for the production of solar modules according to claim 1, characterized in that

i) a sandwich element C) of at least one core layer and at least one outer layer located on each side of the core layer and optionally with fastening and electrical connection elements is presented,

iii) the solar cells are placed on the adhesive layer B) or embedded in the adhesive layer B) or a solar film is applied,

iv) a transparent plastic film A), which optionally has an adhesive layer B), and / or a transparent layer A) is applied to the solar cells,

v) optionally the above-mentioned layer structure is optionally pressed under the influence of temperature and / or optionally under application of a vacuum.

4. A process for the production of solar modules according to claim 1, characterized in that

i) a transparent plastic film A), optionally having an adhesive layer B), and / or a transparent layer A) is introduced, ii) an adhesive layer B) in the form of a plastic film or as a mass is applied to the layer A),

iv) a sandwich element C) of at least one core layer and at least one outer layer located on each side of the core layer is applied to the solar cells,

5. A process for the production of solar modules according to claim 1, characterized in that

i) a prefabricated film module from the layers A) and B), which already has the solar cells or the solar layer, is presented in a pressing tool,

ii) a sandwich element C), which preferably has not yet been pressed, onto the

Side of the film module is applied, which has the adhesive layer,

iii) is optionally pressed under the influence of heat and / or optionally under application of a vacuum.

6. A process for the production of solar modules according to claim 1, characterized in that

i) a not yet connected film module is presented, wherein first the layer A) is inserted into the pressing tool, then an adhesive layer B) is applied and then the solar cells or the solar film applied or embedded in the adhesive layer B)

ii) optionally a further adhesive layer B) is applied,

iii) a sandwich element C), which is preferably not yet pressed, is placed on the side of the film module which has the adhesive layer,

iv) is optionally pressed under the influence of heat and / or optionally under application of a vacuum.

7. Use of the solar modules according to claim 1 as a roofing and roof insulation material.