Patent Application
20140332050
The invention relates to a solar cell string, a method, and a device for connecting solar cells in a solar cell string. The invention is suitable in particular for connecting so-called back-surface solar cells, which are distinguished in that the contact zones, i.e. the p-doped and n-doped regions, are located on the same side of the solar cell.
It is therefore the objective of the invention to create a solar cell string of the type specified above, which can be operated more energy efficiently. In particular, the connections of the solar cells should be distinguished by low ohmic losses. The efficiency of a solar module comprising one or more solar strings of this type should be optimized.
This objective is attained by a solar cell string having numerous solar cells disposed in a row along a longitudinal direction and preferably connected by means of contact elements formed by a metal strip (e.g. of copper). A contact element of this type connects, in each case, two adjacent solar cells to one another. At least for the contact regions having the n-poles, or the n-doped zone, respectively, the solar cells are provided with the insulating material, which, in each case, exhibits a hole, by means of which the contact element is in contact with the solar cells. The insulating material can be a strip extending in the longitudinal direction. By way of example, a preferably one-sided adhesive insulating strip can be used for the insulation, consisting of a plastic material that does not conduct, or only slightly conducts, electricity. An adhesive strip of this type can be readily attached to the solar cells by being pressed against the surface of the solar cell. Of course, other means of attaching the insulation strips to the solar cells are also conceivable. Solder resist, for example, may also be considered for the insulating material, which is applied to the solar cells by means of screen printing. Instead of one or more insulating strips, for example, the solar cells could accordingly be provided with strips of solder resist having basically the same dimensions. Insulating material can, however, also be applied to the solar cells in another coating process or by other means. If the solar cells have numerous rows of n-poles, then the solar cells can be provided, preferably, with a corresponding number of insulating strips applied thereto. Because, in order to create the contact between the contact element and the solar cells, the contact received in the at least one hole has an indentation, numerous advantages are realized. Because of the contact element provided with indentations, wider contact elements can be used, as a result of which the transmission capacity can be significantly increased due to reduced ohmic losses. Thus, the efficiency of a solar module made of solar cell strings of this type can be improved. Depending on the design of the indentation, it is also possible to obtain an improved contact between the contact element and the solar cells.
If the contact element is, for example, a metal strip, it may be advantageous if the indentation is a cup-like indentation, preferably created by means of a deep-drawing or stamping process, in the metal strip. Cup-shaped indentations of this type can be easily produced.
In order to create an advantageous contact surface on the surface of the solar cells, the indentations can exhibit a flat bottom.
The hole, and/or the indentation allocated to the hole can be circular when seen from above. By way of example, a basically complementary circular indentation is particularly preferably allocated to a hole in the form of a circular hole. Of course, other hole shapes and indentation shapes are also conceivable. The holes could, for example, be oval. Polygonal hole shapes and indentation shapes can also be considered. It is particularly advantageous if the holes and indentations have the same shape, wherein, normally, the indentation should be smaller than the hole. As long as the indentation fits into the hole, different shapes could also be considered.
If the contact element, when seen from above, overlaps the at least one hole, i.e. if the respective contact element is wider than the hole when seen from above, then a particularly energy efficient solar cell string is obtained.
The assembly can be further optimized if the contact element is at least 25%, preferably at least 50%, and particularly preferably approx. 100%, wider than the diameter of the at least one hole. For certain applications, the solar cells of the solar cell strings can be furnished with even wider contact elements.
For mechanically stable connections, the respective contact elements can exhibit at least one flat section in the region of an indentation, which lies on the insulating material. The indentation is elevated with respect to the specified flat section. The depth of the indentation would then correspond to the thickness of the insulating material. Theoretically, it would also be possible to provide deeper indentations (the depth of the indentation is greater than the thickness of the insulating material), resulting in a spacing, or gap, respectively, between the solar cell surface and the flat section of the insulating material.
The respective contact element can exhibit at least two flat sections, which are connected by an exposed bridging section at a spacing to the solar cells. The contact element has two corresponding indentations accordingly, preferably elevated in relation to the flat sections.
Another aspect of the invention relates to a method for connecting solar cells, and in particular, for connecting back-surface solar cells in a solar cell string, in particular, the solar cell string described above. The method comprises the following steps: a prefabricated insulating material in the form of an insulating strip, provided at least in sections with holes, is applied to the solar cells. By way of example, insulating strips provided with holes are used for this. These insulating strips are placed on the solar cells such that the holes leave the n-contact zones exposed. In a next step, the contact elements are produced, in that indentations are formed, by means of a deep-drawing or stamping process, in metal strips. Subsequently, the contact elements created in this manner can be applied to the solar cells, wherein the indentations are placed in the respective holes during the application process.
Another aspect of the invention relates to device for creating an electrical connection between the solar cells by means of contact elements, preferably for executing the method described above. The device comprises an application unit for applying insulating material provided with holes to the solar cells, and a stamping or deep-drawing unit having at least one die stamp for creating indentations aligned with the holes in contact elements formed from metal strips.
A respective contact element can have numerous indentations. In order for the indentations to be able to be created in a single step, it can be advantageous if the stamping or deep-drawing unit exhibits numerous die stamps. It is of course also conceivable for the indentations to be created using only one die stamp for each contact element.
The die stamp, or die stamps, can be designed as knob-like projections, by means of which, in a particularly simple manner, cup-shaped indentations can be formed in a metal strip.
Further individual features and advantages of the invention can be derived from the following description of an embodiment example and from the drawings. Shown are:
The following detailed description and appended drawings describe and illustrate various exemplary embodiments of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical.
In order to establish the contact to the respective n-doped contact zone 10, the contact element 3 has a cup-shaped indentation 6, which can be easily created by means of a deep-drawing or stamping process, using a die stamp for example. The contact element 3 is made of a metal strip having a width B, which is shaped by means of cutting and a folding process, or some other shaping process. As a result of this shaping, mechanical tension relief structures are created. These mechanical tension relief structures can prevent, or at least reduce, undesired, thermally influenced expansions or warpings of the solar cells occurring during the creation of the of the contact as a result of, e.g. soldering or welding. Copper strips, for example, can be used for the contact elements, which have been plated with tin (solder coated) or with silver. Other materials, however, are also conceivable (such as aluminum). The deep-drawing or stamping for creating the indentations can occur prior to, during, or after the creation of the tension relief structures. As a rule, each insulating strip, allocated in each case to one solar cell, has numerous holes, wherein each hole is allocated to one n-doped contact zone. Accordingly, the associated contact element also has numerous indentations 6, corresponding to the number of holes. Analogous to the overall assembly shown in
The indentation 6 has a flat bottom 7, for creating an electrically advantageous contact surface. Both the hole 5, as well as the indentation 6 allocated to the hole, are circular when seen from above. The cup diameter D is somewhat smaller than the hole diameter d, such that, on one hand, a simple insertion of the indentation in the hole, and a secure electrical connection (e.g. by means of soldering, gluing, and/or welding) is ensured. In contrast to the known solution, shown in
In terms of the device 30 for connecting a plurality of back-surface solar cells to form a solar cell string, the invention is distinguished in that it has a contact element supply 31 providing the contact elements 3 to a stamping or deep-drawing unit 32, with which indentations 6 can be incorporated in the contact elements made of metal strips. The device 30 can also comprise a solar cell supply 33 providing individual solar cells 2 to an application unit 34, for applying the insulating material 4, preferably in the form of an insulating strip from an insulating material supply 35, on the solar cells. The insulating strip 4 can already be provided with the holes 5, which are created in a prefabrication procedure. It is also conceivable that the device 30 specified above also comprises a means for creating the holes (e.g. a hole station 36) in the insulating strip. The solar cells 2 furnished with the contact elements 3 can pass through a soldering station 37 having a pre-heating zone, in which the electrical contacts are created to form the solar cell string. A cooling region 38 for the solar cell string can be incorporated downstream of the soldering station 37.
In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiment. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 13167080.4 | May 2013 | EP | regional |
