Solar panels using back-contact solar cells

Abstract

A solar panel comprising a transparent plate, a solar cell of back contact type attached to said transparent plate, a back contact foil (302) electrically and mechanically connected to said solar cell and comprising a metallization pattern facing said solar cell, and a laminate (202) attached to said back contact foil, characterized in that said back contact foil presents one or more flaps (104, 304), the ends of which are further away from said transparent plate than from said laminate. The back contact foil is embedded in an encapsulant. Adding a flap to the back contact foil allows the ends of the flap to extend outside the encapsulant. This allows for example the use of a connector to electrically contact the ends of the flaps.

Description

[Technical field]

[0001] The present invention relates to a solar panel comprising a transparent panel, a back-contact solar cell attached to the transparent panel, a back-contact foil electrically and mechanically connected to the solar cell and comprising a metallization pattern facing the solar cell, and a laminate attached to the back-contact foil.

[0002] The invention further relates to a vehicle, yacht or boat equipped with such a panel. [Background technology]

[0003] Solar energy is generally produced by solar cells, such as silicon solar cells. While previous technologies used metal electrodes on both sides, modern solar cells, so-called back-connected cells, show electrodes on only one side. The light-receiving side of these cells is now completely free of metal traces, thus increasing the surface of photosensitive silicon.

[0004] These back-connected cells can be interconnected (serialized, parallelized) using a back-contact foil, which is a polymer film (typically PET) covered with a patterned metallization layer, typically a copper layer. The back-contact foil is thus similar to a flexible printed circuit board. Electrical contact with the back-contact cells is typically made by a conductive adhesive or paste that cures at high temperature.

[0005] Solar panels are used not only as static, flat solar panels installed as solar cells between a glass plate and a metal mounting structure, but also as, for example, roofs and bonnets of solar cars, such as the Lightyear One sold by Atlas Technologies (Hermond, The Netherlands). Preferably, such cars should be light in weight to reduce the power used per kilometer, and the area of ​​the solar panels should be as large as possible to optimize the amount of electricity generated by the solar cells. The use of complete bonnets, roofs and trunks is therefore essential. Generally, the bonnets (as well as the roofs and trunks) comprise glass plates that are at least locally curved in two directions, and which encapsulate photovoltaic devices in the form of solar cells, as described, for example, in WO 2020 / 064474. It should also be noted that the use of polycarbonate plates is also well known.

[0006] For additional strength, a laminate, preferably a composite laminate as described in NL 2026972, is used to support the side opposite the transparent panel. Another demand is that the vehicle is safe and sturdy enough. In particular the bonnet of the vehicle must be able to withstand impacts with pedestrians. The composite laminate strengthens the panel and the glass is attached to the laminate via an encapsulant such as EVA (Ethylene Vinyl Acetate), so that if the glass breaks, all the fragments stay together (bonded to the laminate) and thus reduce damage to e.g. pedestrians.

[0007] All the previously mentioned elements are bonded together with an encapsulant such as EVA. The bonding is done by cross-linking the encapsulant at high temperatures, for example 120°C to 140°C. At this temperature the conductive adhesive also forms a bond between the solar cell and the back contact foil. It should be noted that all bonding can be done in one session or in several sessions.

[0008] To make contact with the solar panel, current wires are soldered to the copper layer of the back contact foil. Soldering to the copper layer carries the risk of melting the PET and thus damaging the back contact foil. Other types of connections, such as gluing, are preferred. However, this has the drawback that stresses lead to cracks in the connection. Also, connectors are hardly usable, since they would be embedded in the encapsulant. Moreover, such connectors would cause undesirable height differences in the encapsulant. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention is intended to avoid or at least mitigate these disadvantages. [Means for solving the problem]

[0010] For that purpose, the panel according to the invention is characterized in that the back contact foil exhibits one or more flaps, the ends of which are further away from the transparent plate than from the laminate.

[0011] The ends of the flap protrude away from the transparent plate and out of the encapsulant so that connection using point welding, laser welding, soldering or connectors can be used after sealing (curing) the solar plate.

[0012] In one embodiment, the panel is locally curved in at least two directions.

[0013] Solar panels are used not only as static, flat solar panels, where the solar cells are placed between a glass plate and a metal mounting structure, but also as roofs or bonnets for example on solar cars, such as the Lightyear One sold by Atlas Technologies (Hermond, The Netherlands). Curved panels are also used in building integrated photovoltaic systems (BIPS).

[0014] In another embodiment, the transparent plate is a glass plate or a polycarbonate plate.

[0015] The transparent plate (transparent to infrared and visible light) is preferably made of glass or, for a cheaper solution, PC (polycarbonate). The reason that the plate must also be transparent to infrared is that highly efficient solar cells, for example silicon solar cells, derive part of their power from photons in the infrared spectrum.

[0016] In yet another embodiment, the laminate includes one or more glass fiber layers and / or one or more carbon fiber layers.

[0017] By using a laminate containing one or more glass fibre layers and / or one or more carbon fibre layers it is possible to create a laminate with a thermal expansion coefficient close to that of glass and therefore avoid stress build-up, as described in NL 2026972 A1.

[0018] In another embodiment, the connector is clamped to the flap.

[0019] By clamping the connector onto the flap, a secure connection can be made between the copper of the back contact foil and the wire ends of the connector.

[0020] In a further embodiment, the metallization of the flap is used to make a removable connection with the connector.

[0021] The connection may be a fixed connection or a removable connection, which is particularly useful for building integrated photovoltaic systems (BIPS) where the components are replaceable, e.g. roof tiles.

[0022] In another embodiment, the flaps are folded over the laminate.

[0023] In this embodiment, the metallization is furthest from the transparent plate, making it visible. If a back contact foil is used, this allows for easier soldering, which is difficult when using PET, but a more flexible foil would be used.

[0024] Because PET is fairly stiff, localized heating may be required to form (deform) it, however, other, more flexible materials may in some cases be usable without localized heating as well.

[0025] In yet another embodiment, a wire or bus bar is soldered to the metallization of the flap.

[0026] Here, a non-removable connection is made using solder to the metallization (copper) of the back contact foil, which can be soldered before the subsequent curing of the encapsulant.

[0027] In yet another embodiment, the laminate exhibits recesses. These recesses can prevent the fibers from scratching the back contact foil. In various of the present embodiments, the laminate exhibits recesses to prevent the fibers from scratching the back contact foil.

[0028] If the laminate contains glass or carbon fibres, the fibres may damage the back contact foil when they extend at the edge of the laminate. This is particularly harmful when carbon fibres are involved, as they are electrically conductive and may cause short circuits. By producing a laminate with a recess, the edge of the laminate is spaced, for example a centimetre away from the position where the back contact foil bends, and the possibility of damage and therefore short circuits is significantly reduced. Thus, optionally in this embodiment, at the position of the recess, the edge of the laminate is spaced away from the position where the back contact foil bends, i.e. the fold line where the flap is folded.

[0029] In yet another embodiment, a layer of encapsulant adheres the solar cell to a transparent plate.

[0030] The encapsulant, typically a cured elastomeric polymer, adheres the solar cell to the transparent plate.

[0031] In a further embodiment, the encapsulant is EVA.

[0032] EVA (a copolymer of ethylene and vinyl acetate) is well known for being transparent, UV resistant, and suitable for use as an encapsulant. Its curing temperature is 120°C to 140°C.

[0033] In one aspect, a vehicle is equipped with any of the solar panels described above.

[0034] Solar panels can be used in so-called solar cars, where part of the propulsion force is generated by solar cells, or in vehicles in which the solar panels generate at least part of the energy required for auxiliary functions such as audio, air conditioning, etc.

[0035] In another embodiment, the panel is at least a portion of at least one of a hood, a roof, and a trunk of a vehicle.

[0036] The roof, trunk and hood are the most efficient locations for generating solar energy, however, it is also well known to use the side panels.

[0037] In another aspect, a yacht or boat is equipped with any of the solar panels described above.

[0038] The present invention will now be described with reference to the drawings, in which like reference numbers indicate corresponding features. [Brief description of the drawings]

[0039] [Figure 1]FIG. 1 is a schematic bottom view of a back contact foil according to the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the sandwiching of the back contact foil and the laminate in the present invention. [Diagram 3] FIG. 3 shows a schematic cross-sectional view of a solar panel. [Figure 4] FIG. 4 is a schematic diagram showing another embodiment of the back contact foil according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] FIG. 1 shows a schematic bottom view of a back contact foil 102 according to the present invention, ie, the side furthest away from the transparent plate.

[0041] The back-contact foil (BCF) 102 is a substrate film, e.g. PET, with a roughly rectangular shape and a patterned conductive layer on top, typically a copper layer 50-100 μm thick. The foil presents a flap 104 that can be folded downwards (away from the transparent plate) along a fold line 106. The flap may comprise one copper track or may comprise multiple tracks.

[0042] It should be noted that substrates other than PET can be used, such as polyimide or polyester film. The conductive layer is typically copper, although aluminum, nickel, gold, silver, etc. (in alloys) are also known to be used.

[0043] FIG. 2 is a schematic diagram showing the sandwiching of the back contact foil 102 and the laminate 202 in the present invention.

[0044] 2 shows a view from the bottom, where the laminate 202 is placed on the BCF 102. The flap 104 is folded downwards (towards the reader). The laminate 202 shows a recess 204 to locally increase the distance between the BCF and the laminate, thereby avoiding any of the fibres of the laminate (glass fibre or carbon fibre) puncturing the flap of the BCF. This could cause other problems, as the carbon fibres in particular are electrically conductive and could thus cause short circuits.

[0045] 3 shows a cross section of a solar panel 100 having a transparent plate 401, a back-contact solar cell 301 attached to the transparent plate 401, a back contact foil 102 electrically and mechanically connected to the solar cell 301 and with a metallization pattern facing the solar cell 301, and a laminate 202 attached to the back contact foil 102. The back contact foil 102 shows a flap 104, the end of which is further away from the transparent plate 401 than from the laminate 202.

[0046] In this embodiment, the flap 104 is folded along the fold line 106 away from the transparent plate 401. The fold line 106 is shown as a sharp crease. In practice, it may be folded more gradually. The laminate 202 exhibits a recess 204 to locally increase the distance between the BCF 102 and the laminate 202, at least at the location of the fold line 106 of the flap 104, thereby avoiding any of the fibres of the laminate (glass fibre or carbon fibre) from puncturing the flap 104 of the BCF 102. At the location of the recess 204, the periphery of the laminate 202 is therefore at a distance from the respective fold line 106, as also shown in FIG. 2.

[0047] The recesses 204 may be formed in the laminate 202 during manufacture of the laminate 202 or may be formed after manufacture, for example, by cutting the recesses 204 into the laminate 202 .

[0048] Although the solar panel 100 in FIG. 3 is flat, in alternative embodiments, the solar panel 100 may be curved in one or more directions.

[0049] FIG. 4 shows a schematic diagram of an alternative form of the back contact foil according to the present invention.

[0050] Here, flap 304 does not extend from BCF 302, but is placed parallel to the side of the BCF. As a result, the flap does not have to fold as sharply, e.g. the stiffness of the PET is less critical. A slight bend starts at line 306 and extends to the end of flap 304. The end of the flap is preferably more or less parallel to BCF 302 and the laminate (not shown in this view) onto which the connector can be clamped.

[0051] It should be noted that although in Figures 1, 2, 3 and 4 the flaps are formed on two opposite sides of the BCF, the flaps may be formed on one, two or three of the four sides and do not have to face each other.

[0052] BCFs are not only metallized on one side (which is usually the case), but also double-sided metallization is known, which allows the use of connectors for double-sided metallization.

[0053] It is most convenient to locate the flaps at the periphery of the BCF, but even flaps located in the center of the BCF are conceivable, although this would mean cutting into the laminate.

[0054] The different elements of the solar panel are encapsulated by a hardened layer of encapsulant such as EVA. The transparent plates can be plates (flat or curved) of glass, polycarbonate, coated polycarbonate, Plexiglas, acrylic, etc.

[0055] The electrical contact between the electrodes of the solar cell and the BCF is for example made by means of a (curable) conductive adhesive or by soldering, although it is also known to use laser welding.

[0056] Electrical contact between the flap and the wires and / or bus bars is typically made by a (curable) conductive adhesive, soldering or connectors, but may also be made by spot welding, laser welding and other techniques.

[0057] Many types of solar cells are known, most based on silicon (monocrystalline and polycrystalline), but PV cells constructed from gallium, cadmium telluride, copper indium diselenide, perovskites, multi-junction types, etc. are also known, with many others expected to follow. [Explanation of symbols]

[0058] Back Contact Foil (BCF) 102,302 Flap 104,304 Fold line 106 Laminate 202 Solar Panel 100 Transparent Plate 401 Back-contact type solar cell 301 Recess 204 line 306

Claims

1. Transparent plate, a back-contact solar cell attached to the transparent plate; a back contact foil (102, 302) electrically and mechanically connected to the solar cell and having a metallization pattern facing the solar cell; and A solar panel comprising a laminate (202) attached to said back contact foil, Solar panel, characterized in that said back contact foil exhibits one or more flaps (104, 304), the ends of which are further away from said transparent plate than from said laminate.

2. 10. The solar panel of claim 1, wherein the solar panel is curved in at least two directions locally.

3. 3. The solar panel according to claim 1, wherein the transparent plate is a glass plate or a polycarbonate plate.

4. 10. The solar panel of claim 1, wherein the laminate (202) comprises one or more glass fiber layers and / or one or more carbon fiber layers.

5. 2. The solar panel of claim 1, wherein a connector is clamped onto the flap (104, 304).

6. 2. The solar panel of claim 1, wherein the metallization of the flap (104, 304) is used to contact a connector.

7. 7. The solar panel of claim 6, wherein the metallization of the flap (104, 304) is used to make a detachable connection with the connector.

8. The solar panel of claim 1 , wherein the flap (104, 304) is folded over the laminate.

9. 2. The solar panel of claim 1, wherein wires or bus bars are soldered to the metallization of the flap (104, 304).

10. 2. The solar panel of claim 1, wherein the laminate (202) exhibits recesses (204) to prevent fibers from damaging the back contact foil (102, 302).

11. 9. The solar panel of claim 8, wherein each of the flaps (104, 304) is folded at a fold line (106), the laminate has a recess (204), and at the location of the recess, a peripheral edge of the laminate is positioned at a distance from each of the fold lines (106).

12. The solar panel of claim 1, wherein the laminate (202) exhibits a recess (204).

13. 10. The solar panel of claim 1, wherein a layer of encapsulant adheres the solar cells to the transparent plate.

14. 14. The solar panel of claim 13, wherein the encapsulant is EVA.

15. A vehicle comprising the solar panel of claim 1.

16. 16. The vehicle of claim 15, wherein at least a portion of at least one of a hood, a roof, and a trunk of the vehicle is the solar panel.

17. A yacht or boat equipped with a solar panel according to claim 1.

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