DE102008012286A1 - Solar module i.e. photovoltaic component, for directly generating electrical current from sunlight, has plastic carrier providing metallic electrical connecting structure for electrical connection to solar cell arrangement - Google Patents

Abstract

The module has a planar solar cell arrangement comprising a rear construction and a radiation-transparent front disk at its back and front sides, respectively. A casting compound surrounds the arrangement. The construction is formed as a separate module in form of a plastic carrier (1). The carrier provides a metallic electrical connecting structure (2) for electrical connection to the arrangement such that a portion of the structure is completely surrounded by a plastic carrier material and another portion of the structure has a free contact region facing the arrangement. The carrier contains filling material such as metal powder, chalkstone, glass flat blank and silicate. The front disk is made of glass, glass ceramic or polymethyl methacrylate based plastic.

Description

Technical area

The The invention relates to a solar module and a method for Production of a solar module with a flat design Solar cell arrangement, on the back of a back construction and at the front a radiation-transparent front window are provided, as well as with a the back construction and bonding the windscreen and the solar cell assembly between Rear construction and windscreen surrounding embedding material.

State of the art

solar Panels are photovoltaic devices for direct generation of electricity from sunlight. Key factors for a cost-efficient Generation of solar power are the manufacturing costs and the durability the solar modules.

Solar modules usually consist of a composite of a windshield, the interconnected solar cells, which are enclosed by an embedding material, and a rear side construction. A common variant of solar modules is still provided for handling and later mounting with aluminum profiles, which are circumferentially mounted as a frame and sometimes supportive as bracing. The individual elements of a solar module have to fulfill the following functions:
The windscreen, usually made of glass, about 3-4 mm thick, serves to protect against mechanical and weathering and provides part of the mechanical stability of the module. It must be highly transparent, preferably made of white glass with 90-92% transmittance in the upper spectral range, to minimize absorption losses in the optical spectral range of about 300 nm to 1500 nm and thus to maximize the efficiency of the silicon solar cells commonly used.

The Embedding material, often for this ethylene-vinyl acetate films or short EVA films used, is used for embedding the interconnected Cells and the bonding of the entire module network. such Embeddings, however, are not capable of mechanical stress to transfer, an aspect, which will be discussed later becomes.

On the back of the module is used to protect the solar cells and of the embedding material from moisture and oxygen, as mechanical Protection and as electrical insulation a composite foil, mostly existing made of polyvinyl fluoride (PVF) and polyethylene terephthalate (PET) or made of PVF and aluminum. In some cases also on the back as on the front a glass pane used.

A Common embedment technology is vacuum lamination because of the vacuum during lamination, the formation of air bubbles is largely avoided. EVA melts during lamination at about 150 ° C, flows around the interconnected solar cells and is thermally crosslinked.

The The encapsulation or embedding materials used should be included have good barrier properties against water vapor and oxygen, especially due to water vapor or oxygen damage caused by corrosion occur on metal contacts and it comes to the degradation of the EVA material. Thus, the front and back of the solar module should be have high weathering stability and the embedded Solar cells by barrier effect z. B. against water vapor and oxygen protect against corrosion.

in principle need solar modules for their use, eg. B. on Rooftops, high mechanical stability, in particular a high flexural strength and bending strength, around the possible loads in operation, z. B. wind and snow loads, harmless to be able to bear. The mechanical stability known solar modules can by its back, its Front and / or other additional supports, z. B. in the form of aluminum frame, aluminum struts, a stable support structure, which allows bending of the module under Load prevented, guaranteed.

About that In addition, solar modules should reach very long operating times, to ensure profitability. Today usual Requirements for the lifetime of the solar modules are at least 25 Years, rising. In operation, the solar modules are subject high mechanical loads, eg. Due to wind and snow loads, as well as by cyclically occurring temperature fluctuations, that of 80 ° C in full sunlight until below freezing can lie.

Height Material and production costs, for example due to special front glass, special composite film for the back, vacuum lamination, Aluminum frames etc., the necessary manual work, eg. Soldering the electrical cables, mounting and contacting the junction boxes, and the relatively long process times, eg. B. for the lamination and crosslinking of the EVA to a comparatively high proportion of the cost of the Modular construction of the total costs in the double-digit percentage range.

Due to the relatively thick front glass pane, conventional solar modules also have a high weight, in turn, stable and expensive holding rungskonstruktionen required.

One Another important point is the heat dissipation. At full Solar irradiation heat the modules up to 80 ° C on what a reduction in the efficiency of solar cells for Episode has.

Although there are various proposals to reduce the manufacturing cost of solar modules through lower-cost components and manufacturing processes, but these proposals are not really targeted. Significant for the invention are next to possible others the patent EP 000000325369 A2 (Abbr. EP) and the published patent application DE 10101 770 A1 Bayer AG (abbreviation DE).

In EP 325369 A2 describes a photovoltaic module based on embedding a "photovoltaic panel" in a reactive elastomer. The photovoltaic panel consists of a combination of a layer of transparent material, an array of interconnected photovoltaic cells, and a backside layer that does not provide mechanical stability.

In DE 10 101 770 A1 describes a solar module in which the solar cells are completely encapsulated by a polyurethane material, either of the same or of two different polyurethane materials. The transparent polyurethane is elastomer-like soft, so that its bending stiffness is negligible. This results in only a low flexural rigidity of the entire solar module.

Another described variant of a solar module is that in which the solar cells are fixed on a serving as a module back molding on which then a transparent polyurethane is sprayed. In this variant, a higher flexural rigidity of the solar module can be achieved by using a flexurally rigid molded part as module rear side, for example a glass fiber reinforced polycarbonate. Basically, for solar modules that have high mechanical stability, a module with an area of about 1.40 m ^2, without any additional support, such as aluminum frames, aluminum braces, a stable support structure that prevents flexing of the module under load, etc ., ie, self-supporting, withstands all mechanical stress tests specified in the relevant standards.

Around this for a solar module with high mechanical stability To achieve defined requirements, the backside needs to be of the solar module are made relatively thick what with a poor heat dissipation and a higher Weight of the solar module goes along.

Presentation of the invention

The object of the invention is the development of solar modules with high mechanical stability, in particular high bending stiffness and bending strength, so that z. B. a module of this type with an area of about 1.40 m ² without further additional support such as aluminum frame, aluminum struts, a stable support structure that prevents bending of the module under load, etc., so only by itself, all in the relevant mechanical stress tests, based on photoactive elements. The solar module should be particularly cost-effective, robust against external influences, long life and ensure high efficiency even at high solar radiation temperatures. Furthermore, it is a method for cost-effective production of such a solar module specify.

The The object underlying the invention is defined by the claim 1 solved. A solution according to The method is the subject of claim 14. The idea of the invention advantageous further-forming features are the subject of the dependent claims and the further description with reference to the embodiments refer to.

One Solvent-based solar module with a flat surface trained solar cell array, at the back a back construction and at the front one radiation-transparent windscreen are provided, and with a the solar cell assembly between the back construction and the windscreen surrounding embedding material, stands out by the fact that the rear construction as a separate, Stable, lightweight module, by injection molding, injection-compression molding or pressed plastic carrier is that the windscreen with its plastic carrier facing surface over the entire surface by means of a solidifying and mechanical loads transferable potting compound with the plastic carrier connected to the solar cell array between the windscreen and the plastic carrier encloses.

The solar module consists in a particularly preferred embodiment of a produced by injection molding, injection compression or compression lightweight, mechanically stable plastic carrier on the back, a transparent windshield, z. Example of glass, glass ceramic or a transparent plastic, for. B. on the basis of PMMA, on the front, the interconnected and contacted solar cells in the space between windscreen and plastic carrier and a plastic carrier and the front glass bonding, the gap between the plastic carrier and front glass bubble-free filling adhesive layer, which at the same time the Solar cells and the contact system encapsulated.

considered If you use a solar module mechanically as a plate, so does the flexural rigidity with the cube of the plate thickness too. The thickness of the solar module adds up from the thickness of the plastic carrier, the Thickness of the windscreen and the thickness of the adhesive layer between windscreen and plastic carrier. The plastic carrier supplies a part of the mechanical stability of the solar module. The windscreen is made of a material with a significant Flexural strength. So z. B. PMMA at the same thickness and about same density by about a factor of 10 higher bending stiffness as a transparent polyurethane. Through the full-surface bonding of Windscreen and plastic carrier through the adhesive layer also carries the rigid windscreen with the mechanical Stability of the solar module at. This has the consequence that the plastic backing on the back clearly can be made thinner than if the front (as in the case of polyurethane) not to stability which in turn would bring significant benefits in the Heat dissipation and in weight - the density of Polyurethane and PMMA are about the same - as a result.

One Another advantage of the direct bonding of windscreen and plastic carrier is that by gluing the solar cells containing Adhesive layer between windscreen and plastic carrier closer to the neutral bending line or neutral fiber, resulting in lower mechanical stresses in the adhesive layer and thus also in the solar cells leads and due to the lower Load levels can expect a much longer life.

When Another advantage may be mentioned that due to the lower mechanical Tensions in the neutral bending line not only elastic bonds, but also structural bonds with less soft, non-elastomeric Adhesives can be used, which in turn is too obvious higher bending stiffness and bending strength leads.

By the shaping of the plastic carrier by injection molding, Injection molding or pressing takes place with its production the usual low for these technologies Cycle times ranging from a few minutes to less than a minute. Suitable materials for the plastic carrier are z. PBT, PET, PA, PMMA, PC, PP or biopolymers such as PLA or PLA copolymers, preferably with reinforcing fibers, e.g. As glass fibers or carbon fibers or other reinforcing fibers or fillers or mixtures of the above, for improvement the mechanical properties, in particular the rigidity and Strength. The incorporation of the aforementioned fibers is carried out with known in the art compounding technologies, either in one the shaping upstream separate process step or inline in the same process step as the molding with the injection molding compounding technology.

Of the Plastic for the wearer can be additionally with be equipped with a filler, the thermal conductivity increased, z. As metallic fibers or powdered Copper. Furthermore, he can use a filler for reduction the thermal expansion of the unfilled polymer such as Chalk, glass slides or silicates equipped become. The incorporation of the aforementioned fillers takes place with compounding technologies known to those skilled in the art, either in one of the shaping upstream separate process step or inline in the same process step as the molding with the injection molding compounding technology.

In an advantageous embodiment can in the plastic carrier in the process of molding by injection molding, injection-compression molding or pressing the electrical leads from the contacts for the electrical contacting of the solra cells to the junction box be integrated for the external connections, z. B. by introducing the metallic conductors in the cavity for the plastic carrier before the injection process or by a 3D MID process (MID = Molded Interconnected Devices). The injection-molded for the integration of the interconnects Plastic parts suitable technologies are in plastics processing known.

in the Process of molding for the plastic carrier can also be formed with the junction box, z. B. from the same plastic the carrier, or using the Multi-component injection molding from another plastic. The for the Forming the junction box and sealing the cable from the Solar cells for junction box required mold and injection molding technologies are known in plastics processing.

On the front side facing the plastic carrier Additional layers can be applied, for. Legs IR-reflecting plastic layer for better use of the incident light for increasing the efficiency or as barrier layers. The layers may be on the support either after shaping or in the process of molding in the tool with in the plastic processing known technologies are applied z. As the in-mold coating or a spray application or flooding with a reactive polymer in the tool or by inserting and injecting of foils in the mold before injecting the plastic for the carrier.

In a preferred embodiment ent holds the plastic support fasteners for later assembly, which can be inserted as inserts (inserts) in the mold cavity and in this way can be integrated into the carrier non-positively in the shaping. The fasteners are positioned in a mold in the tool at the appropriate locations prior to encapsulation in a manner familiar to those skilled in the art. The technologies required for inserts are well known in plastics processing.

To The production of the plastic carrier, the solar cells placed on the carrier and their connections with the contact points of the integrated in the carrier leads connected to the junction box. The solar cells can before unbound or already applied to the carrier be partially interconnected, z. B. in wafer-based cells in the form of strings, or fully interconnected, e.g. B. as interconnected Thin-film module or wafer-based cells as prefabricated Film with the contacted, contacted solar cells, the Channels for the interconnection of the individual cells with each other contains.

In an advantageous embodiment of the plastic carrier a border at the places where the cells are placed for each cell that allows for fixation of the cells. It can either be a depression into which the cells be inserted, or a small increase at the edges every cell. In addition, the surface of the carrier at the points where the cells rest on the support, structured so that the cells are not flat on the carrier so as to later during the introduction of the adhesive in the space between disc and carrier for their bonding the complete flow around the To ensure cells.

The Connection of the electrical connections of the solar cell array with the contacts on the plastic carrier and the supply lines to the junction box for the external connections is carried out by joining techniques known to the person skilled in the art, such as soldering, Wire bonding or other common technologies.

alternative can the electrical connection of the electrical connections the solar cells with the contacts on the plastic carrier be prepared by conductive adhesives. In this Case forms the glue, which initially on the contacts is applied to the plastic carrier and after the Contacting with the electrical connections of the photoactive Elements hardens, the solder. With conductive adhesives can be wafer-based, unlocked back-contact Solar cells without further wiring directly to the contacts be contacted to the carrier, so that the individual solar cells through the absence of further wiring is arranged closer together and so the yield per area can be increased can.

On the front of the solar module is the windscreen. The Thickness of the windscreen is in the range between a few tenths Millimeters and a few millimeters. The windscreen is preferably from a transparent plastic, z. B. based on PMMA.

at Thin-film cells, usually already on a disk, z. Example of glass, plastic, glass ceramic or ceramic, deposited This disc is the windscreen of the module.

In An advantageous embodiment can reduce the reflected portion of the incident light to those skilled in the art known antireflection layers or texturing on the irradiated light facing surface of the disc applied become.

In an advantageous embodiment, the windscreen for Increasing the photon yield even with fillers be provided that the wavelength of the radiating Convert light and in this way the quantum efficiency in the Increase wavelength range in which the photoactive cells have their greatest efficiency.

Of the The space between the disc and the carrier becomes bubble-free filled with a polymer, on the one hand the windscreen glued to the carrier and the other in the space between carrier and windscreen located photoactive Protects cells and the contact and interconnect system from media influence. In the case of wafer-based cells, it is preferably a highly transparent, elastic polymer. The thickness of the gap is in the range of a few tenths of a millimeter to a few millimeters.

For the long-term stability of the invention Solar modules are due to changing temperatures and different Expansion coefficients of the materials used thermal Tensions of particular importance. These voltages can to defects in the solar cells or on the contact and track system, Delamination between the plastic carrier and the adhesive layer or adhesive layer and windscreen and destroying the Lead module composite. By using an elastic Polymers of the adhesive layer become temperature-induced mechanical Tensions in the area between windscreen and carrier largely reduced.

By using one with low viscosities, e.g. B. at room temperature in the range less than 1000 mPas and below, processable plastic encapsulation, e.g. B. as a reactive system or as a dispersion, thinnest column of a few microns can be filled pore-free.

The Polymer of the plastic encapsulation can either be first on the carrier applied with the electrically contacted solar cells and then the Windscreen are placed. For the order of the polymer the plastic encapsulation on the carrier is suitable for. B. a pressureless casting process. The appropriate technologies are known in the art.

through Fixation aids, z. B. a tool, but can also first the windscreen in its final position above the carrier fixed and then the polymer of the plastic encapsulation in the gap be introduced between the windscreen and the carrier. Therefor can handle both high pressure and low pressure processes be used. The corresponding technologies are the specialist known.

When Polymers of the plastic encapsulation are transparent polyurethane systems, for example, aliphatic polyisocyanates, native polyurea systems, Casting silicones, native epoxides, plastisols.

Brief description of the invention

The Invention will hereinafter be understood without limitation of the general Erfindungsgedankenens with reference to embodiments below Reference to the drawings described by way of example. Show it:

1a -E Sequenzbilddartstellung for the production of a solar module

Ways of carrying out the invention, commercial usability

In the 1a to manufacturing steps for cost-effective production of a solar module are shown.

In 1a is the plastic carrier 1 represented, which is made by means of an injection molding or injection-compression molding method or by means of a pressing process of a plastic material. Inside the plastic carrier 1 is at the same time an electrical connection structure 2 provided for the subsequent electrical contacting of the solar cell array. The back has the plastic carrier 1 over rib-like struts 1' , which serve on the one hand for stabilization and for fixing the solar module. The electrical connection structure 2 has the back to the plastic carrier 1 a central junction box 2 via which the completed solar module can be connected to an external control and supply unit.

In the production step according to 1b becomes a series ("string") interconnected 4 solar cells 3 on the front of the plastic carrier 1 placed in position and in the process step according to 1c by means of electrical connections 5 with the electric, in the plastic carrier 1 integrated connection structure 2 connected. Not shown in detail on the front of the plastic carrier 1 formed, plastic receiving structures, in which the over the frame 4 connected solar cells 3 can be fitted so that the solar cells 3 in a predefined position relative to the plastic carrier 1 can be brought to the plant.

In the production step according to 1d is a radiation-transparent, preferably made of PMMA material windscreen 6 on the solar cell array 3 . 4 Applied, leaving a gap between the windscreen 6 and the plastic carrier 1 that forms in the in 1f illustrated manufacturing step with a potting compound 7 is completed completely. The potting compound 7 serves in the form of an adhesive layer through which the windscreen 6 with the plastic carrier 7 intimately connected so that the potting compound 7 is able to transmit mechanical loads accordingly. The potting compound 7 encloses at the same time the internal solar cell arrangement 3 + 4 Hermetically complete, ie, the side edges of the solar cell array are with the potting compound 7 enclosed.

The solar module designed in accordance with the solution thus has the following advantages:
By the construction of the solar module from a separate carrier and a separate front glass, which are glued together by an embedding material with each other, both contribute to the flexural rigidity.

For The plastic carrier can be injection-molded used thermoplastics and this with a high Flexural strength and flexural strength are formed.

The Windscreen is made of a radiation-transparent material, preferably made of plastic based on PMMA, the proven Way high long-term UV stability, low density and has a high flexural rigidity.

The windscreen and the plastic carrier with the solar cell assembly therebetween are glued together by means of a low-stress casting process, so that a high long-term resistance even under changing A conditions with regard to temperature fluctuations and mechanical loads.

The Production time of the production of the solution according to Solar module can by appropriate decoupling of the production Significantly shortened from front and plastic carrier side become.

1

Plastic carrier

1'

rib lines

2

electrical terminal structure

2 '

junction box

3

solar cells

4

frame elements

5

electrical connecting structure

6

windscreen

7

potting compound

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - EP 000000325369 A2 [0013]
• - DE 10101770 A1 [0013, 0015]
• - EP 325369 A2 [0014]

Claims (18)

Solar module with a flat design solar cell array, on the back of a back construction and at the front of a radiation-transparent front panel are provided, as well as with a solar cell assembly between the rear construction and windscreen surrounding embedding material, characterized in that the back construction as a separate module, by injection molding, injection molding or Pressed plastic carrier is that the front window with its plastic carrier surface facing the entire surface by means of a solidifying and mechanical loads transferable, potting compound is connected to the plastic carrier, which encloses the solar cell assembly between the windscreen and the plastic substrate. Solar module according to claim 1, characterized that the front glass is made of glass, glass ceramic, or of a transparent Plastic, preferably a PMMA-based plastic exists. Solar module according to claim 1 or 2, characterized that the solar cell assembly between the windscreen and the Plastic carrier along or near the area of itself at bending of the solar module adjusting neutral bending plane is arranged. Solar module according to one of claims 1 to 3, characterized in that the plastic carrier a commodity or engineering plastic is made, preferably PBT, PET, PA, PMMA, PC, PP, biopolymers, especially PLA, PLA copolymers. Solar module according to one of claims 1 to 4, characterized in that the plastic carrier a having fiber reinforced plastic. Solar module according to one of claims 1 to 5, characterized in that the plastic carrier fillers contains, such as metal powder, chalk, glass flakes, Silicates. Solar module according to one of claims 1 to 6, characterized in that the plastic carrier a integrated in the plastic carrier, electrical connection structure for an electrical connection to the solar cell array provides. Solar module according to claim 7, characterized that an electrical connection between the solar cell array and the plastic carrier side provided, electrical Connection structure by direct electrical contact and / or by means electrical conductive adhesive takes place. Solar module according to one of claims 1 to 8, characterized in that the plastic carrier the solar cell array side facing a recording and Has fixing structure for the solar cell assembly. Solar module according to one of claims 1 to 9, characterized in that the windshield a disc thickness between a few tenths of a millimeter and a few millimeters. Solar module according to one of claims 1 to 10, characterized in that facing away from the solar module on the Surface of the windscreen applied an antireflection coating is. Solar module according to one of claims 1 to 11, characterized in that the windscreen the wavelength the incident on the windscreen radiation converting substances contains such that the converted in wavelength Radiation higher efficiency in the solar cell array scored as the unconverted radiation. Solar module according to one of claims 1 to 12, characterized in that the solar cell array is a thin film solar cell with a radiative transparent topcoat, and that the topcoat the solar cell assembly serves as a windscreen, at least in Near-surface surface area of the radiation-transparent Encapsulant is enclosed and a load transferring Connects to the plastic carrier produces. Process for producing a solar module according to one of claims 1 to 13, characterized, that the back construction as a separate module, using Injection molding, injection-compression molding or pressing in the form a plastic carrier is produced, that the Windscreen in the form of a radiation-transparent disk module provided, that the plastic carrier with an electrical connection structure is provided or the electrical connection structure already during the production of the plastic carrier by injection molding, injection compression molding or Pressing is integrated into the plastic carrier, that the solar cell assembly with the electrical connection structure connected and positioned relative to the plastic carrier becomes, that the windscreen relative to the solar cell array is placed and with this and the plastic carrier includes a space which subsequently becomes more solidifiable Casting compound is poured or that with the potting compound first the solar cell arrangement resting on the plastic carrier potted and then applied the front panel becomes. Method according to claim 14, characterized in that that on a solar cell array facing surface the plastic carrier applied an IR-reflective layer becomes. Method according to claim 14 or 15, characterized in that the electrical connection of the solar cell arrangement with the Plastic carrier side electrical connection structure by soldering, wire bonding or by using electrical Conductive adhesives takes place. Method according to one of claims 16 to 16, characterized in that the potting compound is an elastic polymer, such as transparent polyurethanes, aliphatic polyisocyanates, native Polyuronic systems, casting silicones, native epoxies or plastisols, is used. Method according to one of claims 14 to 17, characterized in that as Vergussmasse a strahlungsstransparentes Polymer is used.