WO1997041605A1

WO1997041605A1 - Solar generator

Info

Publication number: WO1997041605A1
Application number: PCT/EP1997/002164
Authority: WO
Inventors: Julian SCHÜREN
Original assignee: Schueren Julian
Priority date: 1996-04-30
Filing date: 1997-04-26
Publication date: 1997-11-06
Also published as: DE19617220A1; AU2772797A

Abstract

A solar generator has a carrier, a plurality of plate-shaped solar cells (1) and electroconductive connectors (8) which interconnect the solar cells (1) in series. At least part of the solar cells (1) are arranged in a substantially rectilinear string. The connectors (8) which extend in the direction of the string lie over a substantial part of their length next to the solar cells (1).

Description

Solar generator

The present invention relates to a solar generator with the features of the preamble of claim 1.

Such solar generators are known from practice. Crystalline silicon solar cells deliver a voltage of around 0.5 V when irradiated with sunlight. In order to achieve a higher voltage, individual solar cells are combined to form solar modules, the solar cells being connected in series. The surface facing the light has a different polarity than the surface of the solar cell facing away from the light. For electrical series connection, two adjacent solar cells are connected via a connector in such a way that the underside of one solar cell is in electrical connection with the top of the other solar cell. The solar cells to be connected in series are arranged next to one another in solar generators or solar modules, so that an essentially straight row, a so-called string, results. Several strings are also arranged side by side in a solar module in order to be able to implement different dimensions. Each series connection can, for example, have as many solar cells include how they are required to achieve a useful voltage of 12 V, for example. Instead of a single solar cell, a plurality of solar cells can also be connected in parallel within a solar module or solar generator, which leads to a higher current yield and greater operational reliability in the event of the failure of a single cell. The solar cells arranged in strings are usually connected to one another in the region of their mutually facing end faces by an electrical conductor which extends approximately in a Z shape from the underside of one solar cell to the top of the other solar cell. These electrical connectors extend along the shortest distance between the two solar cells to be connected, which is approximately 2-4 mm.

In the case of smaller solar modules, the individual solar cells are occasionally also overlapped on top of one another in a shingle-like manner in the edge regions and soldered there directly. Finally, connections of solar cells are known in which the electrical connection of the surface facing the light is led around the edge to the side facing away from the light source. The electrical connection is then made from this downward contact of the first solar cell to the underside of the adjacent solar cell, again in the region of the shortest distance between the two adjacent solar cells.

The series-connected solar cells in a string are au in the known solar generators on a solid and stei¬ fen carrier, generally ei ^* .- glass plate: put and fixed there. This Glaspia :::, e generally also serves as a front cover and thus as protection against external mechanical and weather influences. In addition, the carrier plate is usually held in a rigid frame, so that a rigid solar generator results overall. The known solar generators are rela- tiv heavy, not flexible and limited in their application possibilities.

It is therefore an object of the invention to provide a solar generator which allows the use of plastics or metals as carrier materials.

This object is achieved by a solar generator with the features of claim 1.

Because the connectors running in the direction of the string lie alongside the cells over a substantial part of their longitudinal extent, on the one hand, with a flexible carrier material, these connectors can be arranged near the neutral fiber of the solar generator and are therefore only subject to ge slight tensile or compressive stresses when the carrier material is bent. On the other hand, the connectors lying next to the solar cells can be adapted in terms of their length and their coefficient of thermal expansion so that the thermal expansion of the carrier material is compensated for. It is advantageous if the part of the connector lying next to the cells corresponds to 0.5 to 2.0 times the length of the cells in the direction of the string.

Electrically conductive carrier materials can be used if electrical insulation, for example in the form of an insulating film, is provided between the connectors and the carrier. A simple manufacture of a solar generator according to the invention results if the plate-shaped cells each carry at least one connection element which is arranged on a flat side of the cell and which projects beyond the cell at least on an edge side. The connectors can then be contacted with the connection element by soldering or welding. Simple geometric relationships result when the two connection elements of a cell with different electrical polarities are approximately symmetrical are arranged with respect to the center of the flat side of this cell. It is also advantageous if the connector and the connection elements are elongated and adjoin one another in an obtuse angle.

The connectors can be brought very close to the carrier material and, if necessary, can be attached to the carrier material in a flexible manner if the connection elements are at least partially designed as a U-shaped clamp which surround the cells on the edge and which on the carrier wear a connection lug on the opposite side. The connectors can then be designed in a band-like and straight manner, in particular between the connection elements, which is advantageous for a simple, flexible and nevertheless relatively short electrical connection.

Particularly good options for the flexible configuration of the interconnected solar cells of a string arise if a number of cells are arranged next to one another on the carrier in a longitudinal direction with a center spacing A, the connectors having a length L in the longitudinal direction and the connecting elements in a transverse direction to run. Good conditions with regard to the resistance to temperature changes of the solar generator result if the thermal expansion coefficient W _{τ of} the support and the thermal expansion coefficient W _{v of} the connectors behave as 0.5 W _τ <W _v <2.0 W _τ .

The material stresses due to temperature fluctuations are compensated particularly well if the length 1 of the connector to the center distance a of the cells is like the coefficient of thermal expansion W _{τ of} the support to the coefficient of thermal expansion W _{v of} the connector.

Exemplary embodiments of the present invention are shown in the drawing. Show it: 1 shows two solar cells which are connected according to the invention in a row;

Figure 2 shows the arrangement of Figure 1 m a side view.

3 shows another connection possibility for solar cells according to FIG. 1 with contact elements guided around the side edges;

Fig. 4 shows a series connection of 4 solar cells, the

Connector and the connecting elements are in one piece; such as

5 shows a series connection of 6 solar cells to form a solar generator, which are arranged on a film printed with conductor tracks.

FIG. 1 shows a top view of its illuminated side of two plate-shaped solar cells 1, which are arranged in a common plane and which each have a long narrow side 2 or 3 opposite one another. On their visible surface 4, which faces the light source during operation, the solar cells 1 each have a connecting element 5 which runs parallel to the long narrow sides 2 and 3 and which has negative polarity when using positively predoped solar cell material. A corresponding connecting element 6 with a positive polarity during operation is provided on the surface facing away from the light source and not visible in FIG. 1. Finally, the solar cells 1 each have two short narrow sides 7, which are exceeded by the connecting elements 5 and 6.

For the electrical series connection of the two solar cells shown in FIG. 1, two connectors 8 are used, which run from the connecting element 5 of one solar cell 1 to the connecting element 6 of the other solar cell 1 and are connected to these End elements are connected in an electrically conductive manner, that is to say are welded or soldered, for example.

2 shows the connection of the two solar cells 1 according to FIG. 1 in a side view. It can be seen that the connection elements 5 are arranged on the surface 4 of the solar cells 1, while the connection elements 6 are located on the opposite surface, here designated 11. The connecting element 8 runs essentially rectilinearly from the connecting element 5 to the connecting element 6. However, it can also initially run horizontally in the plane of the connecting elements 6 and then be angled upward to the connecting element 5 at the height of the connecting element 5.

Another exemplary embodiment of the present invention is shown in FIG. Here, the connecting elements 5 are angled downward in the area in which they protrude the solar cells 1 over the short narrow sides 7 and folded in a U-shape. These connection elements 5, which are designed in the manner of wrap-around contacts, allow the connector 8 to be arranged in a straight line between the connection element 5 and its wrap-around contact and the adjacent connection element 6 of opposite polarity of the next solar cell.

FIG. 4 shows an embodiment of the present invention, in which the connection of the individual solar cells 1 takes place via a metallic support structure which can be manufactured and handled by machine.

In particular, a positive electrical connection 20 and a negative electrical connection 21 with a relatively large cross section are provided, between which the solar cells 1 are arranged. Essentially ^¬ chen U-shaped segments 22 and 23 are integrally formed on the connections 20 and 21, respectively Have two short legs 25 at right angles to the connections 20 and 21 and parallel to the short narrow sides 7 of the solar cells 1. Between the two legs 25, parallel to the connections 20 and 21 and parallel to the long narrow sides 2 and 3 of the solar cells 1, the connecting elements 5 and 6 connected in one piece to the legs 25 extend. The connecting elements 5 and 6 are electrical lei¬ tend connected to the solar cells 1, which are directly adjacent to the terminals 20 and 21. Between these two solar cells 1 there are two further solar cells which are electrically connected in series with the solar cells mentioned. For the electrical series connection of these solar cells, annular, integral connectors 27 with a rectangular shape are provided, each of which is aligned with its short sides parallel to the short legs 25 and with its long sides parallel to the connection elements 5 and 6, respectively. The long sides of the annular element 27 form the connection elements of the solar cells 1 and are electrically contacted on opposite sides of two adjacent solar cells, so that these are electrically connected to one another via the short legs and the connection elements of these annular elements 27. A simple, automatable possibility of producing such solar generators results if the short legs 25 of the U-shaped connection elements and the short legs of the ring-shaped elements 27 are initially connected to one another in a straight line. Such a connection structure can be produced from a sheet metal in a simple manner by punching out rectangular areas. The result is a ladder-like structure which comprises a continuous connection arranged vertically between the connections 20 and 21 and intermediate, transversely arranged connection elements 5 and 6 respectively. These connection elements 5 and 6 can then be bent slightly apart, so that the solar cells 1 are inserted between the connection elements 5 and 6 and electrically connected there. can be clocked. Then, for the electrical separation of the connection elements of positive and negative polarity from each other, approximately square areas are punched out, one of which is designated by way of example with 28 in FIG. In this way, the individual connecting elements 27 are separated from the connections 20 and 21 and from one another, so that an electrical series connection is produced. Several solar cells connected in series, which together form a string, can also be connected in parallel. For this purpose, corresponding arrangements of solar cells are simply to be arranged next to one another between the connections 20 and 21. A short leg 29 provided for this purpose and only partially shown is indicated at the connections 20 and 21.

Finally, FIG. 5 shows an embodiment of the present invention, in which six solar cells 1 are connected in series, the carrier material being a flexible film 30 and electrical connections 31 being printed on the film.

The individual solar cells 1 are provided with the connection elements 5 and 6 on opposite sides, as is already shown in FIGS. 1 to 3. The connecting elements 31, each running parallel to the short narrow sides 7 of the solar cells 1, are printed onto the carrier film 30 as electrical conductor tracks using thick-film technology. For example, an electrically conductive, printable paste m, which can be soldered or welded, is used. The connectors 31 are arranged in a straight line, each interrupted at the points at which the connecting elements 5 and 6 are electrically contacted with the connectors 31. The connection of the connection element 5 of a solar cell 1 arranged at the top with the connector 31 lying in the plane below, which is printed on the film 30, is facilitated in that the connection element 5 except for the plane of the film 30 is angled down and therefore forms a step in the region of the short narrow side 7.

The electrical taps of the solar generator according to FIG. 5 are not shown in FIG. 5, but they are arranged in an obvious manner at the respective ends of the connecting elements 31. In order to protect the arrangement according to FIG. 5 against damage and environmental influences, provision is made to seal the entire arrangement in a sealing film which is permeable to the part of the optical spectrum of interest, which leads to a hermetic seal of the solar generator. Due to its flexibility, the solar generator shown can then be glued onto the surface of, for example, mobile homes or sailing boats.

The mechanical load on the solar generators according to the invention when the individual solar cells 1 are angled toward one another is kept low by the fact that the connectors 8 between the connection elements 5 and 6 are located laterally next to the solar cells and have good flexibility due to their relatively large free length exhibit.

The stress caused by thermal influences, namely by different thermal expansion of the various materials used, can be almost completely compensated in the following way. The geometric center points of the individual solar cells 1 are designated by M in FIG. Approximately in the area of the center points M, the solar cells 1 are glued to the underlying carrier material. The center points M have a linear distance a in the direction of the string from one another. The connectors 8 arranged outside the solar cells 1 run parallel to the direction of the shortest distance a, that is to say in the string direction, and have the length 1. The length 1 can be, for example, 90% of the center distance a. If a carrier material is selected that has a coefficient of thermal expansion W _τ , it will be removed ^■ The center points M when the carrier material is heated by a »ΔT * W _τ away from each other. If no thermal stresses are to occur in the area of the connector 8 or the connection elements 5 or 6, the thermal expansion of the connection elements 8 must absorb this thermal expansion between the center distances M. For this purpose it can be assumed that the thermal expansion of the solar cell material (crystalline silicon) is low, for example in the case of a metallic support or a plastic support. For this purpose, the thermal expansion W _{v of} the connector 8 must be greater than the thermal expansion W _{τ of} the carrier material if the connector 8 is shorter than the center distance a. If the center distance a is smaller than the length 1 of the connector 8 measured parallel to a, then the thermal expansion W _{v of} the connector 8 is selected to be smaller than the thermal expansion W _{τ of} the carrier material. Almost complete compensation results if the relationship 1 * W _V = a »W _τ applies.

Claims

claims

1. Solar generator with a support, with a number of plate-shaped cells (1) and with electrically conductive connectors (8) which connect the cells (1) to one another in an electrical series circuit, at least a part of the cells (1) is arranged as an essentially straight-line string, characterized in that the connectors (8) running in the direction of the string lie along a substantial part of their longitudinal extension next to the cells (1).

2. Solar generator according to claim 1, characterized in that the adjacent to the cells (1) part of the connector

(8) 0.5 to 2.0 times the length of the cells (1) in the direction of the string.

3. Solar generator according to one of the preceding claims, characterized in that electrical insulation, for example an insulating film, is provided between the connectors (8) and the carrier.

4. Solar generator according to one of the preceding claims, characterized in that the plate-shaped cells

(1) each carry at least one connection element (5, 6) which is arranged on a flat side (2, 3) of the cell (1) and which projects beyond the cell at least on one edge side.

5. Solar generator according to one of the preceding claims, characterized in that each cell (1) to the opposite flat sides (2, 3) each carry a connecting element (5, 6).

6. Solar generator according to one of the preceding claims, characterized in that the two connection elements

(5, 6) of a cell (1) with different electrical polarity are arranged approximately symmetrically with respect to the center (M) of the flat side (2, 3) of this cell (1).

7. Solar generator according to one of the preceding claims, characterized in that the connectors (8) and the connecting elements (5, 6) are elongated and adjoin one another at an obtuse angle.

8. Solar generator according to one of the preceding claims, characterized in that the connection elements are at least at least partially designed as a U-shaped bracket (22, 23) which encompass the cells (1) on the edge side and one on the side facing the carrier Wear connection lug.

9. Solar generator according to one of the preceding claims, characterized in that the connectors (8) between the connecting elements (5, 6) are band-shaped and straight.

10. Solar generator according to one of the preceding claims, characterized in that a number of cells (1) are arranged in a longitudinal direction with a center distance a alongside one another on the carrier, the connectors (8) having a length 1 in the longitudinal direction and Connection elements (5, 6) run in a transverse direction.

11. Solar generator according to one of the preceding claims, characterized in that the thermal expansion ^¬ coefficient W _{t of} the carrier (4) and the thermal expansion coefficient W _{v of} the connectors (8) behave as 0.5 W, <W _v <2.0 W ,.

12. Solar generator according to one of the preceding claims, characterized in that the length 1 of the connector (8) to the center distance a of the cells (1) behaves like the coefficient of thermal expansion W _{t of} the carrier (4) to the coefficient of thermal expansion W _v Connector (8).