AT509905B1 - PHOTOVOLTAIC MODULE - Google Patents

Abstract

The invention relates to a photovoltaic module with a plurality of solar cells (1) having a solar radiation exposed front and a back, wherein a first solar cell (1) or a first group of solar cells (1) on its back with a front side of a first section an electrically conductive heat conductor (4) is connected, and at least one further solar cell (1) or a further group of solar cells (1) via its rear side to the front of another portion of the electrically conductive heat conductor (4) is connected, which electrically conductive heat conductor (4) via a thermally conductive, but electrically insulating layer (5) with a metallic base plate (6, 7) is connected, wherein the front of the first solar cell (1) or group of solar cells (1) with the front of the further portion of the electric conductive heat conductor (4) is electrically connected. According to the invention, the connection of the first solar cell (1) or group of solar cells (1) to the further section of the electrically conductive heat conductor (4) takes place with the aid of an electrical conductor (11) which, at its end regions, contacts the solar cell ( 1) and on the other hand to the other portion of the electrically conductive heat conductor (4) is fixed by ultrasonic bonding.

Description

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Description: The present invention relates to a photovoltaic module with a plurality of solar cells having a solar radiation exposed front side and a rear side, wherein a first solar cell or a first group of solar cells via its rear side with a front side of a first portion of an electrically conductive heat conductor is connected, and at least one further solar cell or another group of solar cells is connected via its rear side to the front side of another portion of the electrically conductive heat conductor, which electrically conductive heat conductor is connected via a thermally conductive, but electrically insulating layer with a metallic base plate, wherein the front side of the first solar cell or group of solar cells is electrically connected to the front side of the further section of the electrically conductive heat conductor, and a method for producing such a photovoltaic module.

The generation of electricity by photovoltaic is becoming increasingly important, since it is a completely emission-free, CO2 neuutraies and thus completely environmentally friendly process. Especially in tropical and subtropical desert areas, photovoltaics will be particularly advantageous because the average radiant power is much greater than in temperate latitudes and virtually unlimited space for the installation of modules is available. A known problem with the use of photovoltaic modules under these conditions is the fact that the efficiency of such devices decreases with increasing temperature. This is called the negative temperature coefficient. This plays an essential role, as it can come to temperatures of well over 100 ° C without efficient cooling to a heating of photovoltaic modules. At these temperatures, the lifetime of the modules is noticeably reduced.

From WO 2009/135238 A, a photovoltaic module is known in which this problem is taken into account that solar cells are connected via a heat-conducting but electrically insulating layer with a metal plate over which the radiant heat can be dissipated efficiently. This can basically be done by heat release to the ambient air, for example via cooling fins, but it is preferred to use a liquid cooling medium, such as water.

The electrical contacting of the individual solar cells in a conventional manner in that connecting wires are soldered on the one hand on the top and on the other hand on the underside of solar cells. A typical type of contacting is described in EP 2 141 747 A. This known solution has several disadvantages. On the one hand, due to the flux used during the soldering process, the solder joint damages the solar cell, which according to experience begins to degenerate in the area of the solder joint over time. This problem is exacerbated by the expected prohibition of solder with lead content. Another disadvantage is that the heat dissipation on the back of the solar cell must be made in consideration of the contact and therefore compromises must be made. In addition, the percentage of the total area of the photovoltaic module that is effectively available for the conversion of solar radiation is limited due to the areas required for the contacting.

From DE 30 10 566 A1, a solar cell solar thermal converter in thin-film technology is known, in which on a heat collector plate first an insulating film is applied. On this insulating film, numerous lower electrodes made of aluminum are arranged, on which amorphous silicon layers are deposited, which are finally covered by upper, transparent electrodes. The upper electrodes are respectively connected to the lower electrodes adjacent in one direction so that the solar cells made of amorphous silicon are connected in series. The transparent upper electrodes are made of indium tin oxide film unsuitable for large area applications.

The object of the present invention is to avoid these disadvantages and to provide a photo voltaic module which is durable and efficient with effective cooling. Another object of the present invention is to provide a method for producing such a photovoltaic module.

In particular, should be possible with the present invention, an efficient and commercially meaningful offshore use, i. that the modules are arranged floating in the sea. It can be both an arrangement in the shallow shallow water and on the high seas.

Essential to the present invention is that the heat-conducting layer is used below the solar cells not only for heat transfer, but also for electrical contact. In this way it is possible to produce a full-surface connection of the individual solar cells with the base plate, without having to take account of Kontaktierungsdrähte or the like. It can thus be achieved an optimal thermal transition at the same time advantageous electrical properties.

It is particularly advantageous if the connection of the first solar cell or group of solar cells with the other portion of the electrically conductive heat conductor by means of an electrical conductor, which at its end on the one hand to the solar cell and on the other hand to the other portion of the electrically conductive Heat conductor is attached by ultrasonic bonding (US bonding). This technology involves making an electrical connection by ultrasound, which mechanically removes the surface oxide layer of aluminum, resulting in a durable and stable bond. It is particularly advantageous that it does not thermally stress the components due to the only minimally introduced heat and the use of flux and the like can be avoided. In this case, the so-called wedge method is particularly preferably used.

The preparation of the electrical connection of the individual solar cells can be favored in a particularly preferred manner that the heat-conducting layer protrudes on at least one side of the solar cells. This protruding portion is used for the attachment of the bonding wires.

Another particularly favorable embodiment of the present invention provides that the heat-conducting layer of aluminum and the heat-conducting, but electrically insulating layer of epoxy resins, in particular in the form of 2-component systems is made. In this way, the heat introduced by the solar radiation heat can be dissipated particularly efficient.

The effective area ratio of the individual solar cells can be particularly increased, that a plurality of individual contacts are connected to the front of the solar cell individually to the other portion of the heat-conducting layer. Solar cells are often designed so that a plurality of thin, mutually parallel individual contacts are arranged on the surface, which are connected by one or two perpendicular thereto extending collecting contacts. The contacting takes place by soldering of corresponding connecting wires to these collecting contacts (bus bars). Typically, the collection contacts consume about 2% -3% of the total area of a solar cell, which reduces the efficiency accordingly, since this area is not available for power generation. In the preferred embodiment, the collecting contact is now omitted and the individual contacts are provided directly with bonding to connect them with the heat-conducting layer of the adjacent solar cell (so-called finger-contacting). In this way, the area required for contacting can be reduced accordingly. In addition, it is possible in this way to provide special formats in non-rectangular form with high efficiency available.

Alternatively, it is possible to connect a connecting wire with a collecting contact on the front several times by ultrasonic bonding. As a result, a simplification is achieved in the production compared to the concept presented above, whereby it is possible due to the ultrasonic bonding method to use much narrower collecting contacts, so that the space requirement compared to conventional solutions can also be reduced.

Another particularly preferred embodiment provides that the solar cells are covered by a glass plate and that the space between the solar cell and the glass plate is filled with a two-component resin. In comparison to conventional layer structures with EVA films, a particularly dense, robust and long-lasting connection of the individual components can be achieved, which has particular advantages under harsh environmental conditions, for example when used in the area of seawater.

Furthermore, the present invention relates to a method for producing a photovoltaic module, in which on a metallic base plate, a heat-conducting, but electrically insulating layer, on a heat-conducting layer and thereon a solar cell are applied. According to the invention, this method is characterized in that the electrically conductive heat conductor is subdivided into a first section and at least one further section and that a solar cell at the first section of the electrically conductive heat conductor by means of an electrical conductor by ultrasonic bonding electrically with a front side of the further section the electrically conductive heat conductor is connected. There are several possibilities for the order of execution of the individual method steps. However, it is particularly preferred to provide the base plate with the heat-conducting, but electrically insulating layer, and to apply thereto a continuous heat-conducting layer in the form of a metal foil. Thereafter, this heat-conducting layer is preferably divided by etching or plasma process into a plurality of non-contiguous sections. On each of these sections, a solar cell or a group of solar cells is then adhesively bonded or ultrasonically connected. Thereafter, the contacting takes place by connecting the upper side of a solar cell to an adjacent section of the heat-conducting layer. Thereafter, the module is completed by applying the glass plate and potting the gap. This method is preferably carried out so that the base plate equipped with the solar cells is covered with a glass plate, the assembly thus obtained is evacuated and then the space between the base plate and the glass plate is filled with a two-component resin.

A further advantage of the invention is that the distance between the electronic components can be minimized to each other for an electrical connection. Thus, the proportion of actively used surface of the panel can be better utilized. The example of a photovoltaic module with a panel size of 600 x 600 mm can cover up to 12% more surface area with active solar cells.

With a subsequently arranged on the back of the electrical components and the electrical components, continuously thermally conductive layer structure, the thermal energy is dissipated over the entire layer structure and the temperature in the electronic components, which would otherwise accumulate reduced. Using the example of photovoltaic modules can thus reduce the negative temperature coefficient expressed adverse effect of heating the photovoltaic cells on the production of electrical energy.

In the context of the invention, spaced-apart components or spaced-apart groups of components may be connected to a common electrically conductive heat conductor. In general, however, it is preferred that the electrically conductive heat conductor is structured in separate sections and that spaced-apart components or spaced-apart groups of components are each connected to a dedicated electrically conductive heat conductor. The last-mentioned variant has the advantage that structuring of the panel equipped with the components takes place by structuring the electrically conductive heat conductor. Using the example of a photovoltaic module with a panel size of 600 x 600 mm, which has hitherto provided electrical connection collection tapes occupying about 3% of the active surface of the solar cells, this has the effect that the cell efficiency of e.g. 17% can be increased to 20%.

In the context of the invention, the components may be connected directly to the electrically conductive heat conductor, for example by ultrasound. Alternatively, the components may be connected to the electrically conductive heat conductor via a thermally conductive connection layer, for example a thermal adhesive or a thermal compound.

In a particularly preferred embodiment, the electrically conductive heat conductor is a layer of copper or aluminum with a layer thickness of 10 pm to 70 pm.

In a further preferred embodiment of the invention, a stable heat conductor is arranged on the side facing away from the components of at least one electrically insulating layer. In particular, it can be provided that the stable heat conductor is a heat exchanger, which is preferably the last layer in the layer structure.

Two exemplary application areas in which the photovoltaic module according to the invention is used particularly advantageously, are an offshore use, e.g. a use outside of coastal waters, such as on the high seas, and for use in desert areas.

Further details, features and advantages of the invention will become apparent from the following description with reference to the accompanying drawings, in which preferred embodiments are shown.

1 shows in perspective a possible layer structure of a panel according to the invention in the form of a photovoltaic module, [0026] FIG. 2 shows a sectional view of a panel according to the invention

Example of a Photovoltaic Module, Fig. 3 is a perspective view of an inventive

Panels in the form of a photovoltaic module for offshore use, Fig. 4 and Fig. 5 is a schematic representation of an inventive

Fig. 6 shows a schematic representation of the layer structure, and Figs. 7, 8 and 9 show different variants of the rear side of a panel, [0031] 10 shows the view of a paneled panel from the front; and [0032] FIG. 11 shows a partial section through FIG. 10.

In Fig. 1, a layer structure of a panel is shown. This structure comprises a layer of electronic components 1, namely solar cells. Two transparent layers are provided on the front side of the electronic components 1, namely a layer of a transparent encapsulation 2 and a layer of thin solar glass 3.

In the embodiment as a photovoltaic module, the transparent potting 2 may be an optionally coated, profiled plastic part with reflective or mirror-reflecting properties, which is partially disposed in the space between adjacent solar cells or between adjacent groups of solar cells. When sun rays impinge on the potting 2, they are reflected by the profiling on the solar glass 3, whereupon part of the reflected rays is reflected back to the solar cells. Thus, a certain part of this solar radiation that would otherwise be lost and thus wasted, can be used.

On the back of the electronic components 1, a 30 pm thick layer of copper or aluminum is provided as an electrically conductive heat conductor 4. For the manufacture of the panel, the electrically conductive heat conductor 4 is either structured before the electronic component 4/13

1), or the electronic components 1 are mounted on the electrically conductive heat conductor 4 and then it is patterned.

In particular, in the embodiment of the panel in the form of a photovoltaic module is to be noted that not only the thermal energy is to be considered physical size but always also the electrical energy. Therefore, a heat-conducting layer 5 made of an electrically insulating material (dielectric) is provided on the rear side of the electrically conductive heat conductor 4. The layer 5 is selected to be electrically insulating so that a breakdown of a certain voltage is effectively prevented. As is known from WO 2009/135 238, the heat-conducting layer 5 made of an electrically insulating material may be designed to be electrically insulating in the high-voltage or low-voltage range, the photovoltaic module optionally being galvanically isolated from the mains voltage of the power supply by means of a DC / DC converter can be.

As the last layer, the structure has a stable heat conductor 6, which provides the necessary mechanical stability. The stable heat conductor 6 may be a single layer of stainless steel or a heat exchanger 7 having a refrigerant inlet 8 and a refrigerant outlet 9. The heat exchanger 7 may be used to remove and transfer the heat, e.g. be coupled with a cooling circuit of a heat pump.

FIG. 2 shows a detail of a layer structure of a panel according to the invention using the example of a photovoltaic module P, wherein this layer structure can be transferred equally to a luminaire or a computer control. The solar cells are not directly connected to the copper or aluminum layer as an electrically conductive heat conductor 4 but via a thermal adhesive as a heat-conducting compound layer 10. The solar cells are not directly adjacent to each other but are spaced from each other. In the space between the solar cells, the electrically conductive heat conductor 4 partially forms the surface of the photovoltaic module P. The electrically conductive heat conductor 4 is structured in separate sections, wherein the spaced-apart solar cells are each connected to an associated electrically conductive heat conductor 4. For the electrical connection between two adjacent solar cells (each of which forms a pair of solar cells) an attached by bonding electrical conductor 11 is provided, each connecting the front of a solar cell with the other solar cell associated region of the electrically conductive heat conductor 4. The electrically conductive heat conductor 4 thus serves as a thermally active circuit board. In order to prevent the breakdown of the voltage, the heat-conducting layer 5 of electrically insulating material is arranged on the electrically conductive heat conductor 4. The last layer is the stable heat conductor 6.

In Fig. 3 panels according to the invention are shown using the example of a photovoltaic module P for offshore use. For this purpose, a plurality of photovoltaic modules P are mounted on a raft of the exemplary size of 10 x 10 m. The raft floats by means of floats 12 on the (sea) water surface 13. The cooling takes place directly over sea water, the sea water inlet 8 is connected to an underwater pump 14. On one side of the raft, a collecting line for the sea water inlet 8 may be provided, whereas a collecting line for the sea water spout is provided on another side of the raft. With the panels according to the invention in the form of photovoltaic modules, an electrical power of about 25 kW can be generated.

An advantage of this embodiment is that the cooling water reservoir is inexhaustible, with no additional thermal energy is released into the sea. In addition, the energy expenditure for the cooling is minimal, since the pumping capacity per raft with the exemplary size of 100 m2 is about 500 W.

FIGS. 4 and 5 show a panel according to the invention with nine photovoltaic modules P and an underground water tank 15 for use in the desert. During the day (FIG. 4), the thermal energy from the sun is collected by the photovoltaic modules P and transmitted to the water tank 15. With the continuous thermally conductive layer structure, the photovoltaic modules P are cooled, bringing their electrical 5/13

IsterreidBäCses AT509 905B1 2013-10-15

Performance is increased. The night mode (Fig. 5) provides that the thermal energy accumulated during the day is given back to the environment, whereby the day and night temperature jump (the temperature can fall below 0 ° C at night) is also used. A closed water cycle provides the photovoltaic modules with cool water in the morning.

The particular advantage of this embodiment is that the desert area can be used. In principle, a lot of solar energy can be converted into electrical energy in this application area, although the great heat has a negative effect on the electrical power of the photovoltaic modules P. This reduces the electrical power at approx. 90 ° C by approx. 40 - 50%. However, according to the invention, the thermal energy can be dissipated particularly well, wherein, moreover, the overall efficiency is increased.

Fig. 6 shows the layer structure of an embodiment of the invention. The back side is formed by the layer 6, which is made of stainless steel and forms the above-discussed stable heat conductor. In addition, the electrically insulating, heat-conducting layer 5, the so-called dielectric is arranged. The main aspects of the selection are dielectric strength at overvoltages of more than 80 kV / mm and a strain behavior adapted to layer 6. The thermal conductivity should be greater than 1 W / mK. In addition, the heat conductor 4 is arranged, which is already divided into individual, mutually electrically insulated sections. About a conductive adhesive 10, the connection to the individual solar cell 1 is produced. Optionally, a reflective layer, not shown here, may be provided between heat conductor 4 and conductive adhesive 10 in order to increase the efficiency.

A transparent potting layer 16 and a solar glass 17 cover the module upwards.

Fig. 7 shows the back of a variant with cooling fins 18 on the layer 6 to improve the air cooling.

Fig. 8 shows the back of a variant with a pipe system 19 on the layer 6 for water cooling.

Fig. 9 shows the back of a variant with cooling fins 18 on a pipe system 19 for air cooling with simultaneous or alternative water cooling.

Fig. 10 shows a module, generally designated 20, enclosed by a frame 21 which is tightly welded at the corners at 25.

Fig. 11 shows the structure of Fig. 10 in detail. The edge-curled layer 6 forms the frame 21, with the edge 22 facing the surface 26 of the module 20, i. of the solar glass 17 is bent out. The permanently sealed connection is ensured by a resilient seal 23 which is clamped therebetween. In this way, a seawater resistant design can be achieved. 6.13

Claims (11)

1. A photovoltaic module with a plurality of solar cells (1) having a solar radiation exposed front side and a back side, wherein a first solar cell (1) or a first group of solar cells (1) on its back is connected to a front side of a first portion of an electrically conductive heat conductor (4), and at least one further solar cell (1) or a further group of solar cells (1) connected via its rear side to the front side of another portion of the electrically conductive heat conductor (4) is, which electrically conductive heat conductor (4) via a thermally conductive, but electrically insulating layer (5) with a metallic base plate (6, 7) is connected, wherein the front of the first solar cell (1) or group of solar cells (1) with the Front side of the further portion of the electrically conductive heat conductor (4) is electrically connected, characterized in that the Verbindun g of the first solar cell (1) or group of solar cells (1) with the further portion of the electrically conductive heat conductor (4) by means of an electrical conductor (11), which at its end regions on the one hand to the solar cell (1) and on the other another portion of the electrically conductive heat conductor (4) is fixed by ultrasonic bonding. 2. Photovoltaic module according to claim 1, characterized in that the electrically conductive heat conductor (4) has a flat rear side. 3. Photovoltaic module according to one of claims 1 to 2, characterized in that the electrically conductive heat conductor (4) on at least one side beyond the solar cells (1) protrudes. 4. Photovoltaic module according to one of claims 1 to 3, characterized in that the electrically conductive heat conductor (4) consists of aluminum or copper. 5. Photovoltaic module according to one of claims 1 to 4, characterized in that the heat-conducting, but electrically insulating layer (5) is made of epoxy resin, preferably as a 2-component system. 6. Photovoltaic module according to one of claims 1 to 5, characterized in that a plurality of individual contacts on the front side of the solar cells (1) are individually connected to the further portion of the electrically conductive heat conductor (4). 7. Photovoltaic module according to one of claims 1 to 6, characterized in that a connecting wire with a collecting contact on the front side of the solar cells (1) is repeatedly connected by US bonding. 8. Photovoltaic module according to one of claims 1 to 7, characterized in that the solar cells (1) are covered by a glass plate and that the space between the solar cell (1) and the glass plate is filled with a 2-component resin. 9. A method for producing a photovoltaic module, in which on a metallic base plate (6, 7), a thermally conductive, but electrically insulating layer (5), thereon an electrically conductive heat conductor (4) and then solar cells (1) are applied, characterized in that the electrically conductive heat conductor (4) is subdivided into a first section and at least one further section and that a solar cell (1) is ultrasonically bonded to the first section of the electrically conductive heat conductor (4) by means of an electrical conductor (11) is electrically connected to a front side of the further portion of the electrically conductive heat conductor (4). 10. The method according to claim 9, characterized in that the subdivision of the electrically conductive heat conductor (4) is effected by etching. 11. The method according to claim 9 or 10, characterized in that the solar cells (1) populated base plate (6, 7) with a glass plate (3, 17) is covered, the assembly thus obtained is evacuated and then the space between the base plate and glass plate is filled with a 2-component resin. 4 sheets of drawings 7/13