DE212011100108U1 - Photovoltaic module - Google Patents

Abstract

A photovoltaic module having a plurality of solar cells (1) having a solar radiation exposed front side and a rear side, wherein a first solar cell (1) or a first group of solar cells (1) via its rear side with a front side of a first portion of 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) is connected to a base plate (6, 7), the front side of the first solar cell (1) or group of solar cells (1) being connected to the front side of the further section of the electrically conductive heat conductor (4) is electrically connected, characterized in that the connection of the first solar cell (1) or group of solar cells (1 ) takes place with the further portion of the electrically conductive heat conductor (4) by wedge bonding.

Description

The present invention relates to a photovoltaic module having 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 is connected via its rear side to a front side of a first portion of an electrically conductive heat conductor, and at least one further solar cell or a further group of solar cells is connected via its rear side to the front side of a further section of the electrically conductive heat conductor, which electrically conductive heat conductor is connected to a metallic and / or non-metallic base plate via a thermally conductive but electrically insulating layer, 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.

The generation of electric power by photovoltaic is becoming increasingly important, since it is a completely emission-free, CO ₂ -neutral 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 the 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 is carried out 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 way of contacting is in the EP 2 141 747 A described. 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 the DE 30 10 566 A1 a solar cell converter having several solar cells in thin-film technology is known, in which an insulating film is first applied to a heat collector plate. 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 photovoltaic module which is durable and efficient with effective cooling.

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

It is essential to the present invention that the heat-conducting layer underneath the solar cells is used not only for heat transfer but also for electrical contacting. 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 wedge bonding) takes place. 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.

In particular, it is provided that the connection of the first solar cell or group of solar cells with the further portion of the electrically conductive heat conductor by means of a bonding wire or bonding tape, which at its end by wedge bonding to the solar cell or its Ableitelektrode on the one hand and the another portion of the electrically conductive heat conductor on the other hand is fixed by ultrasonic bonding.

The production of the electrical connection of the individual solar cells can be favored in a particularly preferred manner in that the heat-conducting layer protrudes on at least one side over the solar cells. This protruding portion is used for attaching the contacting wires or tapes.

Another particularly preferred embodiment of the present invention provides that the heat-conductive 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 fraction of the individual solar cells can be increased in particular by connecting a plurality of individual contacts on the front side of the solar cells individually to the further section of the heat-conducting layer. Solar cells are often designed so that on the surface of a plurality of thin, mutually parallel individual contacts are arranged, which are connected by one, two or more perpendicular thereto collecting contacts (busbar). The contacting takes place by soldering of corresponding connecting wires to these collecting contacts (bus bars). Typically, the collection contacts cover relatively large active areas 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 repeatedly bond a bonding wire to a collecting contact on the front side by ultrasonic bonding. As a result, a simplification is achieved in the production compared to the concept presented above, wherein it is possible due to the Ultraschallbondingverfahrens to use significantly 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. Compared to conventional layer structures with thermoplastics (eg EVA films, a particularly dense, robust and durable connection of the individual components can be achieved here, which has particular advantages under harsh environmental conditions, for example when used in the area of seawater.

To produce a photovoltaic module, a heat-conducting, but electrically insulating layer is applied to a metallic or non-metallic base plate, thereupon a heat-conducting layer and thereon solar cells. In this case, the heat-conducting layer is subdivided into a first section and at least one further section, and a solar cell at the first section of the heat-conducting layer is electrically connected by US bonding to a front side of the further section of the heat-conducting layer. There are several possibilities for the sequence of execution of the individual 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 subdivided by etching, laser cutting or milling into a plurality of non-contiguous sections. On each of these sections, a solar cell or a group of solar cells is subsequently glued over the entire surface and connected with wedge technology. Thereafter, the contacting takes place by each of the top of a solar cell with an adjacent portion of the electric conductive layer is connected. 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 gap, which is defined for example with spacers, filled between the base plate and glass plate with a two-component resin.

Another advantage of the invention is that the distance of the electronic components to one another for an electrical connection can be minimized. Thus, the proportion of actively used surface of the panel can be better utilized.

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

In the context of the invention, spaced-apart components or groups of components spaced apart from one another 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.

In the context of the invention, the components can 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 corresponding layer thicknesses.

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, for. As an off-shore use, such as on the high seas and 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. Show it:

1 in perspective, a possible layer structure of a panel according to the invention in the form of a photovoltaic module;

2 a sectional view of a panel according to the invention using the example of a photovoltaic module;

3 a perspective view of a panel according to the invention in the form of a photovoltaic module for offshore use;

4 and 5 a schematic representation of a panel according to the invention in the form of a photovoltaic module for use in a desert;

6 a schematic representation of the layer structure;

7 . 8th and 9 different variants of the back of a panel;

10 the view of a paneled panel from the front;

11 a partial section through 10 ; such as

12 and 13 a detailed sectional view and a plan view of the bond produced by wedge bonding using a bonding wire or bonding ribbon.

In 1 a layer structure of a panel is shown. This structure comprises a layer of electronic components 1 , namely solar cells. On the front of the electronic components 1 two transparent layers are provided, namely a layer of a transparent potting 2 and a layer of thin solar glass 3 ,

In the embodiment as a photovoltaic module, the transparent potting 2 an optionally coated, profiled plastic part with reflective or mirror-reflecting properties, which is partially arranged in the space between adjacent solar cells or between adjacent groups of solar cells. When sunbeams on the potting 2 These are obtained by profiling on the solar glass 3 reflected, whereupon a portion 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 is a 30 micron thick layer of copper or aluminum as an electrically conductive heat conductor 4 intended. To produce the panel, the electrically conductive heat conductor 4 either structured before the electronic components 1 be mounted on it, or the electronic components 1 be on the electrically conductive heat conductor 4 attached and then this is structured.

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, at the back of the electrically conductive heat conductor 4 a heat-conducting layer 5 made of an electrically insulating material (dielectric). The layer 5 is chosen so electrically insulating that a strike through a certain voltage is effectively prevented. The heat-conducting layer 5 made of an electrically insulating material can as from WO 2009/135238 be known in the high-voltage or low-voltage electrically insulating, wherein the photovoltaic module may optionally be electrically isolated from the mains voltage of the power supply by means of a DC / DC converter.

As the last layer, the structure has a stable heat conductor 6 on, which provides the necessary mechanical stability. The stable heat conductor 6 may be a simple layer of stainless steel or glass, for example, or a heat exchanger 7 with a brine inlet 8th and a brine spout 9 , The heat exchanger 7 can for discharging and transferring the heat z. B. be coupled with a refrigeration cycle of a heat pump.

In 2 is a section of a layer structure of an inventive panel on the example of a photovoltaic module P can be seen, this layer structure is equally applicable to a lamp or a computer control. The solar cells are not directly with the copper or aluminum layer as an electrically conductive heat conductor 4 but connected 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 forms the electrically conductive heat conductor 4 partly the surface of the photovoltaic module P. The electrically conductive heat conductor 4 is structured into separate sections, with the spaced-apart solar cells 1 each with an associated portion of the electrically conductive heat conductor 4 are connected. For the electrical connection between two adjacent solar cells (these each form a pair of solar cells) is an attached by US bonding electrical conductor 11 provided, in each case the front side of a solar cell with the other solar cell associated region of the electrically conductive heat conductor 4 connects (see detail according to 12 and 13 ). The electrically conductive heat conductor 4 thus serves as a thermally active circuit board. To prevent the breakdown of the voltage is to the electrically conductive heat conductor 4 the heat-conducting layer 5 arranged of electrically insulating material. The last layer is the stable heat conductor 6 ,

In 3 panels of 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 × 10 m. The raft floats by floats 12 on the (sea) water surface 13 , The cooling is done directly or indirectly via seawater, the seawater inlet 8th with an underwater pump 14 connected is. On one side of the raft can be a collecting pipe for the sea water inlet 8th be provided, whereas a manifold for the sea water spout is provided on another side of the raft.

An advantage of this embodiment is that the cooling water reservoir is inexhaustible, with no additional thermal energy being released into the sea. In addition, the energy required for cooling is minimal, since the pump power per raft with the exemplary size of 100 m ² is about 500 W.

In the 4 and 5 is a panel according to the invention with nine photovoltaic modules P and an underground water tank 15 shown for use in the desert. During the day ( 4 ), the thermal energy from the sun is collected by the photovoltaic modules P and into the water tank 15 transfer. With the continuous thermally conductive layer structure, the photovoltaic modules P are cooled, whereby their electrical power is increased. Night operation ( 5 ) provides that the thermal energy accumulated during the day is released to the environment again, whereby the day and night temperature jump (the temperature can fall at night below 0 ° C) is 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. Cooling compensates for this effect.

6 shows the layer structure of an embodiment of the invention. The back is through the layer 6 formed of stainless steel and forming the above-discussed stable heat conductor. Above that is the electrically insulating, heat-conducting layer 5 , the so-called dielectric arranged. Key considerations in choosing are sufficient dielectric strength overvoltages, one of the layer 6 adapted expansion behavior and a very good thermal conductivity. Above is the electrically conductive heat conductor 4 arranged, which is already divided into individual, mutually electrically isolated sections. About a conductive adhesive 10 becomes the connection to the individual solar cells 1 produced. Optionally, between heat conductor 4 and conductive adhesive 10 a reflection layer not shown here may be provided to increase the efficiency.

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

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

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

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.

10 shows one here in general 20 designated module, that of a frame 21 edged in at the corners 25 is tightly welded.

11 shows the structure of 10 in detail. The layer flanged at the edge 6 forms the frame 20 where the edge 22 to the surface 26 of the module 20 , ie the solar glass 17 bent over. The permanently tight connection is ensured by an elastic seal 23 ensured that is trapped in between. In this way, a seawater resistant design can be achieved.

The 12 and 13 show a detailed sectional view and a plan view of the bond produced by ultrasonic bonding using a thin bonding wire or bonding ribbon 11 which or which at its end regions by wedge bonding to the solar cell 1 or their discharge electrode 1a on the one hand and the adjacent, further section of the electrically conductive heat conductor 4 on the other hand, each secured by ultrasonic bonding. For a better overview, the solar-side solar glass and the transparent potting compound were omitted here.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2009/135238 A [0003]
• EP 2141747 A [0004]
• DE 3010566 A1 [0005]
• WO 2009/135238 [0037]

Claims (9)

Photovoltaic module with several solar cells ( 1 ) having a solar radiation exposed front side and a rear side, wherein a first solar cell ( 1 ) or a first group of solar cells ( 1 ) via its rear side with a front side of a first section of an electrically conductive heat conductor ( 4 ), and at least one further solar cell ( 1 ) or another group of solar cells ( 1 ) via its rear side with the front side of a further section of the electrically conductive heat conductor ( 4 ), which electrically conductive heat conductor ( 4 ) via a heat-conducting, but electrically insulating layer ( 5 ) with a base plate ( 6 . 7 ), the front side of the first solar cells ( 1 ) or group of solar cells ( 1 ) with the front of the further portion of the electrically conductive heat conductor ( 4 ) is electrically connected, characterized in that the connection of the first solar cell ( 1 ) or group of solar cells ( 1 ) with the further portion of the electrically conductive heat conductor ( 4 ) by wedge bonding. Photovoltaic module according to claim 1, characterized in that the connection 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 a bonding wire or bonding tape ( 11 ), which at its end regions by wedge bonding to the solar cell ( 1 ) or its lead-off electrode ( 1a ) on the one hand and the further portion of the electrically conductive heat conductor ( 4 ) is attached on the other hand by ultrasonic bonding. Photovoltaic module according to claim 1 or 2, characterized in that the electrically suffering heat conductor ( 4 ) has a flat rear side. Photovoltaic module according to one of claims 1 to 3, characterized in that the electrically suffering heat conductor ( 4 ) on at least one side over the solar cells ( 1 ). Photovoltaic module according to one of claims 1 to 4, characterized in that the electrically-suffering heat conductor ( 4 ) consists of aluminum or copper. Photovoltaic module according to one of claims 1 to 5, characterized in that the heat-conducting, but electrically insulating layer ( 5 ) is made of epoxy resin, preferably of epoxy resin. Photovoltaic module according to one of claims 1 to 6, characterized in that a plurality of individual contacts on the front side of the solar cells ( 1 ) individually with the further portion of the electrically conductive heat conductor ( 4 ) are connected. Photovoltaic module according to one of claims 1 to 7, 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. Photovoltaic module according to one of claims 1 to 8, characterized in that the solar cells ( 1 ) are covered by a glass plate and that the space between the solar cells ( 1 ) and the glass plate is filled with a 2-component resin.

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