Protection of space solar cells in a string arrangement
The novel rear-side integration of string protection diodes with a metal strip and separate covers addresses the challenges of repairability and heat dissipation in space solar cells, improving reliability and reducing costs while maintaining efficiency.
Patent Information
- Application Number
- DE102023002227
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-06-01
- Publication Date
- 2025-07-31
- Estimated Expiration
- 2043-06-01
AI Technical Summary
Existing space solar cell designs face challenges in repairability, reliability, and heat dissipation due to the integration of string protection diodes on the front side, leading to increased complexity and weight, which complicates maintenance and reduces efficiency under intense solar radiation.
A novel arrangement of string protection diodes on the rear side of space solar cells, integrated with a metal strip and separate covers, allowing for easy replacement and improved heat dissipation through radiant cooling, reducing production costs and increasing reliability.
The solution enhances the reliability and reduces production costs by simplifying the interconnection process, enabling efficient heat dissipation and maintaining performance under intense solar radiation without increasing weight.
Smart Images
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Abstract
Description
[0001] Due to the high efficiency requirements, solar cells for space applications are designed as so-called III-V multi-junction solar cells, i.e., with multiple p / n junctions connected in series. Currently, at least three stacked p / n junctions are monolithically integrated. In III-V multi-junction solar cells, the bottom p / n junction is generally formed by a germanium substrate cell.
[0002] In contrast to solar cells for terrestrial applications, which are almost exclusively single-cell silicon solar cells constructed in large, rectangular, rigid modules, space solar cells are subject to entirely different requirements. Important requirements for space solar cells include, among other things, the lowest possible weight, an efficiency above 30%, very high reliability and robustness over a wide temperature range, resistance to shocks and also to high doses of proton and electron radiation. Since heat dissipation—i.e., cooling of electrical components—is only possible in the form of radiation in the vacuum of space, heat dissipation from electrical components is considerably more complex than in terrestrial applications.
[0003] As a result, the manufacturing and assembly technology for space solar cell modules, i.e. the type of panels, developed completely separately and differently from the manufacturing and assembly technology of terrestrial solar cell modules.
[0004] For example, space solar cells, after being thinned to a thickness of less than 150 µm, are arranged one after the other in individual rows, also known as strings. The space solar cells are welded together along the string using special, equally lightweight and flexible metal connectors, thereby connecting them electrically in series. The strings are flexible along their length and are arranged on ultralight, carbon-fiber-reinforced rigid panels or on thin, flexible carrier films.
[0005] A panel generally comprises several strands. On a panel, several strands are interconnected in series and / or parallel using flexible cables on the back of the respective panel. For this purpose, the panel has a cable harness on the back. Furthermore, other electrical components are located on the back of the panel.
[0006] In contrast to the aforementioned designs for space solar cells, terrestrial solar cells are rigidly mounted on a mechanically rigid, heavy, and stable carrier plate and covered with a rigid, particularly hail-resistant glass plate. The glass plate is arranged on a surrounding frame for exactly one panel at a time, with each panel sealed against environmental influences by means of the frame and an adhesive, particularly silicone.
[0007] The total weight of a terrestrial solar cell panel is many orders of magnitude higher than an ultralight space solar cell panel. Furthermore, in terrestrial applications, defective panels are easy to replace. Therefore, a terrestrial solar cell panel requires only a few protection diodes.
[0008] In contrast, in the panels for space, each of the space solar cells has its own bypass diode so that if one space solar cell fails, not all of the space solar cells in the respective string fail, i.e. the entire string does not fail.
[0009] In most cases, the associated bypass diodes are located in one of the two cropped corners of a space solar cell. Each bypass diode is directly connected to the respective space solar cell via a metal connector. For reliability reasons, the connectors are always welded.
[0010] To protect the space solar cells from space radiation, the front sides of each of the space solar cells and the bypass diode located in the corner are protected from short-wave UV light by a separate, very thin cover glass.
[0011] The ultra-thin cover glasses are each less than 0.2 mm thick and are bonded to the front of the space solar cell using an adhesive. The bypass diodes arranged in the cropped corners are covered by the cover glass of the associated space solar cells. In other words, the bypass diodes do not have their own separate cover glass.
[0012] A disadvantage of the above-mentioned arrangement is that in the event of a fault in the pair consisting of a space solar cell and the associated bypass diode, individual parts of a pair can only be replaced with great effort.
[0013] If the space solar cells are already arranged on the string, replacing a defective part of the string is even more complex, resulting in the entire string being defective and being replaced with a different string. In other words, repair or rework is not economically viable.
[0014] An array of space solar cells is known from DE 10 2004 044 061 A1. The space solar cells are designed in the form of a string. As explained above, each of the space solar cells has a bypass diode arranged in the corner of the space solar cell. The bypass diode is electrically connected in antiparallel with the respective space solar cell and protected by the common cover glass.
[0015] In addition to the respective bypass diodes, each string of space solar cells contains one or more packaged or encapsulated string protection diodes (i.e., encased in molding compound). The function of the string protection diode is to suppress currents in a direction opposite to normal operation (i.e., in a reverse direction), thereby reducing power losses.
[0016] The string protection diodes are connected in series with the space solar cells of a string in a forward-biased (i.e., forward-biased) direction. In other words, when exposed to sunlight, the space solar cells arranged on the string generate a current of a few amperes, typically 1.5 A, with the entire current flowing through the forward-biased string protection diode.
[0017] In a reverse direction, voltages generally range between 10V and 100V, especially when, for example, one of the several interconnected strings is exposed to little or no sunlight, while one of the other strings is exposed to full sunlight. Current flow through the darkened strings is suppressed by the string protection diode, which is now reverse-biased.
[0018] For reasons of reliability and flexibility, one or more packaged string protection diodes are arranged on the back of the panel for each string in the designs currently in use and connected to the string on the front of the panel via flexible electrical cables. Due to this arrangement, the packaged string protection diodes on the back of the panel are protected from additional heat input from the sun, so heat dissipation is not problematic at higher current loads.
[0019] It should be noted that due to the lack of convection in space, passive cooling only occurs in the form of radiant heat, with only a small amount of energy being radiated at the maximum permissible temperatures of less than or equal to 170°C for the string protection diodes, which are usually designed as Si diodes.
[0020] For redundancy reasons and / or to reduce heat generation, several string protection diodes are often connected in parallel.
[0021] From US 2018 / 0062011 A1 in particular the Fig. 3a and Fig. 3b and Fig. 4a and Fig. 4b shows an integrated arrangement of string protection diodes arranged on the front side. One or more string protection diodes are integrated at the end of each string, similar to the integrated arrangement of the bypass diode, in a second corner of the space solar cell arranged at the end of the string. The second corner and the first corner are arranged on the same side of the space solar cell.
[0022] In this case, a back or front side of the string protection diode is electrically connected in series to the back or front side of the immediately adjacent space solar cell by means of another metallic connector. A second contact is formed on the top side of the string protection diode. The second contact is connected via another connector to a rectangular, continuous metallic contact section at the end of the space solar cell string. Similar to the bypass diode, the string protection diode is also bonded to the cover glass of the immediately adjacent space solar cell.
[0023] As already mentioned above, the string protection diodes are integrated with the respective space solar cell, corresponding to the bypass diode, i.e. the string protection diode is arranged together with the space solar cell on a plastic carrier film or on the panel.
[0024] This makes the production of strings much more complex, since the string protection diodes in particular have to be much larger and more powerful than the bypass diodes in order to cope with the current load of the entire string in the forward direction with the lowest possible electrical losses.
[0025] In other words, space in the corners of space solar cells is very limited. It has also been shown that a triangular design is impractical due to the additional effort required to saw the string protection diodes out of the Si fabrication substrate.
[0026] Furthermore, solar radiation is significantly more intense in space than on Earth. Cooling the string protection diodes under such intense solar radiation, especially in operating modes where high currents flow through them, is often insufficient. If the temperature of the Si string protection diodes rises to near 150°C, the electrical power loss in the string protection diodes increases further, which can lead to failure.
[0027] Furthermore, experts know that scrap rates also increase during string production. Precisely because of the high level of integration, repair (i.e., rework) for defects in the connection between the string protection diode and the space solar cell or for defects in the protection diodes is not feasible, both economically and due to the high reliability requirements.
[0028] Due to the disadvantages mentioned above for an integrated arrangement on the front of the panel, the above-described discrete arrangement of the string protection diodes on the back of the panels using flexible cables is used in the manufacture of space solar panels.
[0029] Such an embodiment is described in the Fig. 4. This shows a section of the back of a panel for space applications. The individual strands formed on the front of the panel are each interconnected via a multitude of flexible ELK cables on the back of printed circuit boards (PLT). The multitude of ELK cables are combined in the form of cable harnesses (KB). Individual packaged string protection diodes (SSD) are arranged on the larger PLT boards.
[0030] It is understood that one of the Fig. The usual setup shown in Figure 5 requires a certain amount of effort and causes some additional weight.
[0031] Against this background, the object of the invention is to provide a device that further develops the state of the art.
[0032] The object is achieved by a string arrangement of space solar cells having the features of patent claim 1. Advantageous embodiments of the invention are the subject of subclaims.
[0033] In the subject matter of the present invention, an arrangement for protecting space solar cells is provided, wherein at least a portion of the space solar cells are arranged in rows in the form of a string along an X-direction.
[0034] It is understood that longer strands formed in the X-direction, particularly due to the geometric requirements of the panels, can also be arranged in several rows, particularly adjacent to one another, and connected in series.
[0035] The string comprises at least two space solar cells arranged one after the other, wherein the space solar cells immediately adjacent along the X-direction are electrically connected in series with one another by means of one or more metallic connectors.
[0036] The space solar cells each have a receiving surface formed in an X-direction and a Y-direction.
[0037] Furthermore, the string has a front side and a back side, wherein the receiving surfaces of the space solar cells are formed on the front side of the string.
[0038] Furthermore, the string has a first end and a second end, wherein the two ends each extend in the y-direction along one side of the space solar cell arranged at the ends of the string.
[0039] In a further development, the two ends of the strand can be opposite each other along a straight line formed in the Y direction.
[0040] Each space solar cell has a bypass diode connected to the respective space solar cell, wherein the space solar cells each have a thickness in a Z-direction between 30 µm and 300 µm or a thickness between 50 µm and 160 µm.
[0041] Furthermore, a protective arrangement is formed on the front side at at least one of the two ends along the y-direction, wherein the protective arrangement is electrically connected to the space solar cell arranged at the end of the string by means of one of the metallic connectors.
[0042] The protection arrangement comprises a first string protection diode arrangement and a metal strip and a second string protection diode arrangement. The metal strip has a first head end and an intermediate piece and a second head end.
[0043] The first string protection diode arrangement is connected in series in the y-direction to the first head-side end of the metal strip by means of one of the metallic connectors.
[0044] Furthermore, the second string protection diode arrangement is connected in series in the y-direction by means of one of the metallic connectors to the second head-side end of the metal strip.
[0045] The connectors each have two contact surfaces spaced apart from each other by a connecting piece.
[0046] The string protection diode arrangements comprise a plurality of string protection diodes formed as part of a DIE, wherein the DIE has a top side and a bottom side.
[0047] The string protection diodes arranged on the DIE are arranged in rows and / or columns.
[0048] On the top side of the DIE, two immediately adjacent string protection diodes are separated by a scribe frame area and have electrically separated front-side contacts.
[0049] The back of the DIE is metallized so that several or all string protection diodes have a common back contact.
[0050] The common back contact is connected to the metal strip or to the space solar cell arranged at the ends of the string.
[0051] One of the front contacts of the string protection diodes is connected to one of the space solar cells arranged at the ends of the string or to the metal strip.
[0052] It goes without saying that every DIE is unpackaged. In other words, the DIE is a semiconductor component that is not encapsulated in a molding compound or other plastic material.
[0053] Furthermore, each DIE has its own, i.e., separate, cover on its top side, which is glued to the top side of the DIE. The cover is only added in a build step in connection with the production of a strand. It is understood that the cover is flat and transparent. The cover is arranged exclusively on the top side of the DIE.
[0054] Furthermore, the protective arrangement is flat overall and has a thickness in a Z direction of less than 1 mm.
[0055] In the Y-direction, the extent of the entire protective arrangement is at least a factor of five greater than in the X-direction.
[0056] Surprisingly, it was found that integrating the string protection diodes using the present arrangement on the front side of the string is of considerable advantage.
[0057] In particular, one advantage of the protective arrangement is that the wiring effort on the back of the string or panel is significantly reduced.
[0058] The advantageous arrangement of the two strand protection arrangements in conjunction with the metal strip also allows the individual DIE to be replaced in the event of a manufacturing error without mechanically affecting the strand.
[0059] Another advantage is that each DIE has a plurality of individual string protection diodes, with only one of the string protection diodes being connected to each DIE by selecting one of the string protection diodes using the top side terminal.
[0060] It was also shown that the advantageous integration of the string protection diode arrangement in conjunction with the metal strip can reduce manufacturing costs and increase reliability.
[0061] Because the respective DIE of the string protection diode array has a large metallized backside contact area, and the backside contact area is directly connected to the metal strip or directly interconnected to the metal strip via a large-area connector, the DIEs and thus the string protection diode arrays do not overheat, even at maximum power and under direct sunlight. In other words, the large metallized backside of the DIE allows a large amount of heat to be radiated into space.
[0062] In addition to good thermal coupling, the high reflectance of the metal surface on the top side of the DIE is also important. The top sides of the individual string protection diodes have almost full-surface metallization due to the front-side contacts. The overall reflectance of the arrangement in the visible and infrared range is preferably above 80% or above 90%. It is advantageous if the cover layer is permeable to infrared radiation, i.e., transparent, so that the string protection diodes can dissipate heat by emitting radiation in the infrared range.
[0063] In one embodiment, the respective upper sides of the string protection diodes have a metallic layer covering more than 60% of the surface in order to reflect solar radiation or to effectively dissipate the heat of the component.
[0064] In one embodiment, the distance formed in the X-direction between the space solar cell arranged at the end of the string and the protection arrangement is in a range between 0.01 mm to 2.0 mm or in a range between 0.1 mm and 1 mm or in a range between 0.2 mm and 0.5 mm.
[0065] Furthermore, the receiving area of the space solar cell is between 4 cm 2 and 500 cm 2 or between 30 cm 2 and 350 cm 2 or between 70 cm 2 and 160 cm 2 .
[0066] It should be noted that the term "metallic connector" refers to a connector comprising or consisting of a metal. In particular, a metallic connector also encompasses a multilayer structure, for example, composed of one or more organic carrier layers, or of several metal layers and at least one organic carrier layer, or of several different metal layers and one or more organic carrier layers.
[0067] It is understood that the term “wired” refers to an electrical connection.
[0068] In a further development, the electrical connection between the respective contacted string protection diode and the first contact surface of the connector and / or the electrical connection between the second contact surface and the metal strip or the space solar cell is each formed in a materially bonded manner.
[0069] In another embodiment, the contact resistance in the electrical connection is below 10 ohms or below 5 ohms or below 1 ohm.
[0070] Because a string contains a larger number of space solar cells, the electrical performance of the string protection diode must be matched to the electrical specifications of the space solar cell string. In other words, the current carrying capacity of the string protection diodes is at least 50% higher than the maximum current of the string under full solar irradiation and generally amounts to a few amperes.
[0071] Preferably, the current carrying capacity of the individual string protection diode is in a range between 100 mA and 10 A or between 1 A and 5 A.
[0072] In the string protection diode arrangement, the DIE is preferably formed from silicon or GaAs. In other words, the DIE comprises a silicon or GaAs substrate with a common backside metallization and string protection diodes formed on the front side, each separated by the scribe frame.
[0073] An advantage of GaAs over Si-silicon is that the voltage drop in the forward direction is lower.
[0074] In a further development, “Kovar” material is used as a connector and / or as a metal strip.
[0075] In one embodiment, the connector and / or the metal strip preferably comprises more than 50% iron and preferably more than 20% cobalt and preferably more than 10% nickel.
[0076] In another embodiment, an “Invar” connector is used as the connector.
[0077] In a further development, the connector and / or the metal strip comprises or consists of pure silver and / or comprises molybdenum, wherein the molybdenum is preferably coated with silver on one side or both sides.
[0078] To ensure a reliable electrical and mechanical connection, the connectors preferably feature metal tabs. In particular, the metal tabs are designed for welding processes.
[0079] In a further development, the connectors of the protective arrangement are welded to exactly one end of the strand multiple times, i.e., between two and six times. It is understood that the welds are spaced apart from each other in the Y direction.
[0080] In another development, the contact surfaces or the contact lugs of the connectors at one end of the strand are welded to the space solar cell and / or the bypass diode arranged at the end at exactly two contact points spaced apart from one another in the y-direction.
[0081] The distance between the two contact points in the y-direction is a multiple of the distance between the respective contact point and the edge of the space solar cell formed along the x-direction.
[0082] In other words, the two welding points for the connection to the string protection diodes are located near the respective outer edge of the string formed in the x-direction.
[0083] In one embodiment, each string protection diode comprises at least two string protection diodes electrically connected in parallel. The two parallel-connected string protection diodes are preferably arranged parallel to each other in the x-direction and spaced apart from each other in the y-direction. One advantage is that the parallel connection provides simple redundancy in the event of one of the string protection diodes failing.
[0084] In a further development, exactly four string protection diodes are arranged per string, i.e., connected to the string. Two of the string protection diodes are connected in series and form two parallel branches, with the two nodes of the branches being directly connected to each other, i.e., short-circuited.
[0085] An advantage despite the slightly higher resistance of the series connection in the forward direction is that due to the increased, ie more than twice, redundancy, even if more than one string protection diode fails, the respective string is still protected by one or more string protection diodes in the reverse direction.
[0086] In a further development, two string protection diodes connected in parallel are formed at both ends. This creates a series circuit consisting of the string protection diode, the space solar cells of the string or the bypass diodes, and the string protection diode.
[0087] One advantage is that the more than double redundancy further increases reliability compared to the design with only two string protection diodes. Preferably, the string protection diodes have the same electrical data or, to a first approximation, almost the same electrical data.
[0088] In another embodiment, instead of a single string protection diode, two string protection diodes are connected in series. In a further development, one or both of the series-connected string protection diodes are formed from a combination of series and parallel-connected string protection diodes. One advantage is that the serial connection in the reverse direction makes it easy to achieve a higher blocking voltage.
[0089] In one embodiment, the string protection diode is made of silicon or GaAs.
[0090] In another embodiment, the string protection diode has a blocking voltage range between 10 V and 1000 V, or between 30 V and 600 V or between 80 V and 300 V or between 10 V and 300 V.
[0091] In one embodiment, the string protection diode has a current range between 0.1 A and 5 A or between 0.5 A and 2 A.
[0092] In one embodiment, the string comprises exclusively III-V multi-junction space solar cells.
[0093] In another embodiment, at least two and at most twenty III-V multi-junction space solar cells are electrically connected in series on a string.
[0094] In a further development, the serial connection of the space solar cells comprises or consists of five space solar cells or ten space solar cells or twenty space solar cells.
[0095] In another embodiment, the serial connection comprises or consists of a total of no more than forty or no more than one hundred space solar cells connected in series.
[0096] In a further development, the serially connected space solar cells are distributed across at least two or three strings. The serially connected space solar cells are distributed across a maximum of ten strings.
[0097] In one embodiment, a strand, hereinafter also referred to as the overall strand, is divided into several directly adjacent sections, wherein the sections are connected in series with each other and the first end is then no longer opposite the second end in the X direction. It is understood that the two sections are preferably arranged parallel to each other and spaced apart from each other in the Y direction. It should also be noted that the two sections of the overall strand may be of equal length or not of equal length.
[0098] The receiving surfaces of the space solar cells are designed exclusively parallel to the X-direction and the Y-direction. In other words, the receiving surfaces are preferably located in an XY plane.
[0099] In a further development, the connectors have a first contact surface and a second contact surface, wherein one of the two contact surfaces is connected to the full-surface metal contact on the underside or to one of the metal contacts on the top side of one of the string protection diodes and the other of the two contact surfaces is connected to the metal strip.
[0100] In one embodiment, the two contact surfaces of the connectors are designed identically or differently. In another embodiment, at least one of the two contact surfaces or both contact surfaces of the connectors each have one or more contact lugs.
[0101] In a further development, the connecting piece between the two contact surfaces is designed in a meandering shape in at least some of the connectors in order to mechanically decouple the two contact surfaces from each other.
[0102] The term meandering here makes it clear that in the case of the connectors, the connecting piece has a greater extension transverse to a straight line that connects the two contact surfaces than in the direction of the straight line and optionally has several bulges and recesses transverse to the direction of the straight line.
[0103] In other words, in some designs of the connector, the connecting piece resembles the shape of a meander.
[0104] In a further development, the two contact surfaces of the connectors are each flat and have a thickness in the Z direction of between 0.01 mm and 0.7 mm. Preferably, the thickness of the contact surfaces is constant across the entire length.
[0105] In a further development, the connectors have a rectangular surface, wherein the long side of the rectangular surface has an extension that is at least a factor of 5 larger than the short side.
[0106] In another development, all space solar cells of the string each have a bypass diode, wherein the bypass diode is directly connected to the respective space solar cell.
[0107] In a further development, one of the string protection diodes of one of the two string protection arrangements formed at one end of the string is directly connected to the bypass diode of the space solar cell arranged at one of the two ends.
[0108] In one embodiment, a protective arrangement is provided at both ends of the line. One advantage of this is that it increases redundancy.
[0109] In a further development, when light falls on the front of the space solar cells, the current flows exclusively through the contacted string protection diodes and the metal strip to the connecting cable.
[0110] In a further development, the contact lugs have a thickness between 0.01 mm and 0.5 mm or between 0.02 mm and 0.2 mm.
[0111] In one embodiment, the cover of the DIE has a high transmission in the infrared range or is transparent in the infrared in order to reflect the thermal radiation or not to suppress the radiation of heat from the string protection diode.
[0112] In another embodiment, the protective arrangement is formed directly at one of the two ends, wherein the distance in the X-direction between the protective arrangement and the space solar cell connected to the protective arrangement is in a range between 10 µm and 10 mm or in a range between 100 µm and 2 mm.
[0113] In a further development, cooling for the string protection diodes or the DIE is formed by means of the metal strips and / or the connecting line and / or the metallized underside of the DIEs.
[0114] The invention will be explained in more detail below with reference to the drawings. Similar parts are labeled with identical designations. The illustrated embodiments are highly schematic, ie the distances and the lateral and vertical extensions are not to scale and, unless otherwise stated, do not have any deducible geometric relationships to one another. Fig. 1a various designs of a string of space solar cells with a protective arrangement formed at both ends, each connected to one of the space solar cells arranged at the respective end, Fig. 2a - 2e show detailed views of, among others, the front, side and back of the protective arrangement connected to a space solar cell, Fig. 3a - 3f various detailed views of the protection arrangement and the connectors with string protection diode arrangement, Fig. 4 a plan view of the top side of a DIE with several string protection diodes electrically separated by a scribe frame, Fig. 5 is a plan view of a discrete embodiment of string protection diodes on the back of a prior art panel.
[0115] The illustration of the Fig. 1a shows an embodiment of a string STRA of space solar cells WSZ with a protective arrangement SA formed at both ends, wherein the respective protective arrangement SA is connected to one of the space solar cells WSZ arranged at the respective end.
[0116] The protective arrangement SA is flat overall and has a thickness in a Z direction of less than 1 mm.
[0117] The extent of the entire protective arrangement SA is at least a factor of five greater in the Y direction than in the X direction.
[0118] One of the two ends of the protective arrangement WSZ is designed as a positive voltage pole + and the other end as a negative voltage pole -.
[0119] It is understood, however, that in an embodiment not shown, only one protective arrangement SA is formed either at the end with the positive voltage pole + or at the end with the negative voltage pole -.
[0120] In this case, the space solar cells (WSZ) are arranged sequentially in the form of a string (STRA) extending in an X-direction. The STRA string comprises a total of five space solar cells (WSZ). Each of the five space solar cells (WSZ) is protected by its own cover glass (DGS) on its upper surface.
[0121] Two space solar cells WSZ that are immediately adjacent in the X-direction are electrically connected in series with each other using exactly two metallic connectors VB1.
[0122] The space solar cells WSZ each have a receiving surface arranged in an X-direction and a Y-direction.
[0123] The STRA strand has a front side and a back side, with the front side being shown in the top view shown.
[0124] In this case, the receiving surfaces of the space solar cells WSZ are formed on the front side of the string STRA.
[0125] The string STRA has a first end and a second end opposite the first end, wherein the two ends each extend in the y-direction along one side of the space solar cell WSZ arranged at the ends of the string.
[0126] In this case, each of the space solar cells WSZ has a bypass diode SD connected to the respective space solar cell WSZ. The bypass diodes SD are each arranged in a corner of the associated space solar cell WSZ and are connected by two connectors VB1, VB2 to the space solar cell WSZ immediately adjacent in the X direction and to the space solar cell WSZ immediately adjacent in the Y direction.
[0127] It is understood that the bypass diode SD and the space solar cell WSZ assigned in the X-direction are covered by a single cover glass DGS.
[0128] The space solar cells WSZ each have a thickness in a Z-direction between 30 µm and 300 µm or a thickness between 50 µm and 160 µm.
[0129] The protective arrangements SA arranged on the front side of the strand STRA are each formed along the y-direction.
[0130] The protective arrangements SA are electrically connected to the space solar cells WSZ arranged at both ends of the string STRA by means of several metallic connectors.
[0131] The protection arrangement SA comprises a first string protection diode arrangement DGDS and a metal strip BUB, and a second string protection diode arrangement DGDS. Furthermore, it is preferred to form contact lugs with contact surfaces K1 on the metal strip, wherein the contact lugs and the metal strips are generally formed integrally.
[0132] The metal strip BUB has a first head-side end and an intermediate piece and a second head-side end.
[0133] In the embodiment shown in the Fig. 1a, also referred to as the first alternative, the first string protection diode arrangement DGDS is connected in series in the y-direction by means of one of the metallic connectors VB1 to the first head-side end of the metal strip BUB.
[0134] Furthermore, the second string protection diode arrangement DGDS is also connected in series in the y-direction by means of one of the metallic connectors VB1 to the second head-side end of the metal strip BUB.
[0135] Each of the two string protection diode arrangements DGDS comprises a first string protection diode DS1, a second string protection diode DS2, and a third string protection diode DS3. The string protection diodes DS1-DS3 are arranged together on a DIE D (not shown), with two immediately adjacent string protection diodes DS1-DS3 being electrically separated from each other on the top side of the DIE D by a scribe frame RR. In this case, the string protection diodes DS1-DS3 are each arranged in a row.
[0136] The connectors VB1 each have two contact surfaces - not shown - spaced from each other by a connecting piece.
[0137] With the protection arrangement SA connected to the end where the positive potential + is applied, the two string protection diode arrangements DSGS are each connected to the space solar cell WSZ via one of the connectors VB1 formed in the X direction. In other words, the two branches of the string protection diode arrangements DGDS are parallel to each other, thus creating redundancy.
[0138] The metal strip BUB has two contact lugs K1 for connecting a flexible cable (not shown).
[0139] It should be noted that in each of the two branches, the flexible cable (not shown) is connected in series via the contact lugs K1 to the metal strip BUB and the string protection diode arrangements DGDS and the space solar cell WSZ.
[0140] In the case of the protection arrangement SA, connected to the end at which the negative potential is applied, the two electrically contacted string protection diodes DS1-DS3 of the string protection diode arrangements DSGS are each connected by means of one of the connectors VB1 in the negative X direction with one of the respective contact lugs K1 with a flexible cable (not shown).
[0141] In addition, one of the string protection diodes DS1 - DS3 of DIE D of one of the string protection diode arrays DGDS is connected to the bypass diode of the space solar cell WSZ via one of the connectors VB1. In this case, the metal strip BUB is connected to the space solar cell WSZ formed at the end of the string STRA via two further connectors VB1.
[0142] Furthermore, the contacted string protection diode DS1 - DS3 of the first string protection diode arrangement DGDS and the contacted string protection diode DS1 - DS3 of the second string protection diode arrangement DGDS are also connected in series in the y-direction by means of one of the metallic connectors VB1 to the first and second head-side ends of the metal strip BUB.
[0143] Here, too, the two branches of the string protection diode arrangements DGDS are connected in parallel to each other and thus form a redundancy.
[0144] It should be noted that in each of the two branches, the space solar cell WSZ is connected in series via the metal strip BUB with the string protection diode arrangements DGDS and the flexible connecting cables.
[0145] The first string protection diode arrangement DGDS is alternatively arranged at the first head-side end, to which the positive potential + is applied, directly without connector VB1 on the metal strip BUB. This allows, compared to the embodiment shown in the Fig. 1a, save two connectors VB1.
[0146] Alternatively, the second string protection diode arrangement DGDS is arranged at the second head end directly on the metal strip BUB.
[0147] In the Fig. In the arrangement shown in Figure 1a, the two string protection diode arrangements DGDS are each electrically connected in series in the X direction with the space solar cell WSZ arranged at the end of the string STRA by means of one of the metallic connectors VB1.
[0148] It should be noted that in this case, the string protection diode arrays (DGDS) each have their own cover in the form of a cover glass. It goes without saying that the cover is glued to each individual string protection diode array (DGDS).
[0149] In the illustrations of the Fig. 2a - 2e show detailed views of, among others, the front, side and back of the protective arrangement SA connected to a space solar cell WSZ.
[0150] In detail, the Fig. 2b a side view, the Fig. 2c a top view of the back and the Fig. 2 c a perspective view of the arrangement of the Fig. 2a.
[0151] The Fig. Figure 2e shows a detailed side view of a string protection diode arrangement DGDS.
[0152] In the following, only the differences to the previous embodiments are explained.
[0153] The Fig. Figure 2a shows a top view of the front side of one of the space solar cells (WSZ) covered with a cover glass (DGS). At one of the two ends, the edge of the space solar cell (WSZ) formed in the Y direction, the contact tabs of a total of three of the VB1 connectors are visible for serial connection with a neighboring space solar cell (not shown).
[0154] The connectors VB1 have a first contact surface and a second contact surface. One of the two contact surfaces of each of the three connectors is welded to the top of the space solar cell WSZ. The other contact surface is intended for connection to another space solar cell WSZ. In this case, the two contact surfaces are identical.
[0155] Both contact surfaces have multiple contact lugs. The connecting pieces between the two contact surfaces of the VB1 connectors are designed in a meandering shape to mechanically decouple the two contact surfaces from each other.
[0156] On the opposite long edge of the space solar cell WSZ, the protection assembly SA is formed, comprising the two string protection diode arrays DGDS, protected by a cover glass layer, and the metal strip BUB. It is understood that the cover glass is transparent in the infrared range.
[0157] A total of three contact lugs K1 are provided on the metal strip BUB for connecting the flexible cables.
[0158] In the side view of the Fig. Figure 2b shows the thinness of the strand STRA, which is less than one millimeter. Furthermore, a step is formed between the metal strip BUB and the contact lugs K1.
[0159] From the rear view of the Fig. 2c shows that the bypass diode SD is connected to the underside of the space solar cell WSZ via a wide connector VB2. Furthermore, the protection devices SA are connected at the opposite edge via the contact surfaces of the connectors VB1. Furthermore, the DIE D with the three string protection diodes DS1 - DS3 is shown at both ends of the metal strip. In this case, only the first string protection diode DS1 is connected to the string STRA.
[0160] From the presentation of the Fig. Figure 2e shows that one of the two contact surfaces of connector VB1 is connected to the top surface of the top surface of the DIE D and is covered by the cover glass. Furthermore, connector VB1 has a step between the two contact surfaces.
[0161] In the illustrations of the Fig. Figures 3a - 3f show detailed views of the SA protection arrangement and the VB1 connectors, as well as the structure of the DGDS string protection diodes. Only the differences from the previous figures are explained below.
[0162] It can be seen that the contact surfaces of the VB1 connectors each have exactly three contact lugs. The side view of the Fig. 3b that the protective arrangement SA is very thin in the Z-direction and preferably has a thickness of less than 1 mm.
[0163] In the enlarged section of the Fig. Figure 3d shows that on one side of the string protection diode DGDS a cover glass DG is arranged on the top side of the DIE D using an adhesive KL.
[0164] In the illustration of the Fig. 4 shows a plan view of the top side of a DIE D with several string protection diodes DS1 - DS6 electrically separated by the scribe frame RR.
[0165] In contrast to the previous arrangements, the DIE D now contains a total of six string protection diodes DS1 - DS6, arranged in two rows. The DIE has a rectangular shape.
[0166] The underside (not shown) is again metallized over its entire surface and connected via one of the VB1 connectors. On the top side, only the second string protection diode DS2 is connected via one of the VB1 connectors.
Claims
[1] Protection of a space solar cell (SSC) array in a string array (STRA), where - at least part of the array of space solar cells (WSZ) is arranged one after the other in the form of the string (STRA) extending in an X-direction, - the string (STRA) comprises at least two space solar cells (SSCs), - two space solar cells (WSZ) immediately adjacent in the X-direction are electrically connected in series by means of one or more metallic connectors (VB1), - the space solar cells (WSZ) each have a receiving surface arranged in the X-direction and in a Y-direction, - the string (STRA) has a front side and a back side, wherein the receiving surfaces of the space solar cells (WSZ) are formed on the front side of the string (STRA), - the string (STRA) has a first end and a second end, the two ends each extending in the y-direction along one side of the space solar cell (WSZ) arranged at the ends of the string (STRA), - each space solar cell (WSZ) has a bypass diode (SD) connected to the respective space solar cell (WSZ), - the space solar cells (SSCs) each have a thickness in a Z-direction of between 30 µm and 300 µm or a thickness of between 50 µm and 160 µm, where - a protection arrangement (SA) is formed on the front side at at least one of the two ends along the y-direction, and the protection arrangement (SA) is electrically connected to the space solar cell (WSZ) of the string (STRA) arranged at the end by means of one of the metallic connectors (VB1), wherein the protection arrangement (SA) comprises a first string protection diode arrangement (DGDS) and a metal strip and a second string protection diode arrangement (DGDS), - the metal strip (BUB) has a first head-side end and an intermediate piece and a second head-side end, - the first string protection diode arrangement (DGDS) is connected in series in the y-direction by means of one of the metallic connectors to the first head-side end of the metal strip (BUB), and - the second string protection diode arrangement (DGDS) is connected in series in the y-direction by means of one of the metallic connectors (VB1) to the second head-side end of the metal strip (BUB), - the connectors (VB1) each have two contact surfaces spaced apart from each other by a connecting piece, the string protection diode arrangement (DGDS) comprises a plurality of string protection diodes (DS1-DS6) formed as part of a DIE (D), the DIE (D) having a top side and a bottom side, and the string protection diodes (DS1 -DS6) arranged on the DIE (D) are arranged in series and / or columns, whereby on the top side of the DIE (D), two immediately adjacent string protection diodes (DS1-DS6) are separated by a scribe frame area and have electrically separated front-side contacts, and the back of the DIE (D) is metallized so that several or all string protection diodes (DS1-DS6) have a common back contact, and the common back contact is connected to the metal strip (BUB) or to the space solar cell (WSZ) arranged at the ends of the string (STRA), and one of the front contacts of the string protection diodes (DS1-DS6) is connected to one of the space solar cells arranged at the ends of the string (STRA) or to the metal strip (BUB), - each DIE (D) is unpackaged and has its own cover on the top side, the cover being glued to the top side of the DIE (D), - the protective arrangement (SA) is flat overall and has a thickness of less than 1 mm in a Z direction, - the extent of the entire protective arrangement (SA) in the Y direction is at least a factor of five greater than the extent in the X direction. [2] Protection of an array of space solar cells (WSZ) according to claim 1, characterized by that the connectors (VB1) have a first contact surface and a second contact surface, wherein one of the two contact surfaces of connectors is connected to a metal contact on the rear side or to one of metal contacts on the front side of one of the string protection diodes (DS1-DS6) and the other of the two contact surfaces is connected to the metal strip. [3] Protection of an array of space solar cells (SSC) according to claim 1 or claim 2, characterized by that the two contact surfaces of the connectors (VB1) are of the same or different design. [4] Protection of an array of space solar cells (WSZ) according to any one of the preceding claims, characterized by that in the connectors (VB1) at least one of the two contact surfaces or both contact surfaces each have one contact lug or several contact lugs. [5] Protection of an array of space solar cells (WSZ) according to any one of the preceding claims, characterized by that in the connectors (VB1) the connecting piece between the two contact surfaces is designed in a meandering shape in order to mechanically decouple the two contact surfaces from each other. [6] Protection of an array of space solar cells (WSZ) according to any one of the preceding claims, characterized by that the two contact surfaces of the connectors (VB1) are each flat and each have a thickness in the Z direction of between 0.01 mm and 0.7 mm. [7] Protection of an array of space solar cells (SSC) according to any one of the preceding claims, characterized by that the connectors (VB1) have a rectangular surface and the long side of the rectangular surface has an extension at least a factor of 5 greater than the short side. [8] Protection of an array of space solar cells (SSC) according to any one of the preceding claims, characterized by that all space solar cells (WSZ) of the string (STRA) each have a bypass diode and the bypass diode (SD) is directly connected to the respective space solar cell (WSZ). [9] Protection of an array of space solar cells (WSZ) according to any one of the preceding claims, characterized by that one of the two contacted string protection diode arrangements (DGDS) is directly connected to the bypass diode (SD) of the space solar cell (WSZ) arranged at one of the two ends. [10] Protection of an array of space solar cells (WSZ) according to any one of the preceding claims, characterized by that a protective arrangement (SA) is formed at both ends of the strand. [11] Protection of an array of space solar cells (WSZ) according to any one of the preceding claims, characterized bythat when light hits the front of the space solar cells (WSZ), the current flows exclusively through the contacted string protection diode (DS1-DS6) and the metal strip (BUB) to a connecting line. [12] Protection of an array of space solar cells (WSZ) according to claim 4, characterized by that the contact lugs have a thickness between 0.01 mm and 0.5 mm or between 0.02 mm and 0.2 mm. [13] Protection of an array of space solar cells (WSZ) according to any one of the preceding claims, characterized by that the cover of the DIE (D) is transparent in the infrared to reflect solar radiation and / or the cover is designed as a cover glass. [14] Protection of an array of space solar cells (WSZ) according to any one of the preceding claims, characterized bythat the protective arrangement (SA) is formed directly at one of the two ends and the distance in the X-direction between the protective arrangement (SA) and the space solar cell (WSZ) connected to the protective arrangement (SA) is in a range between 10 µm and 10 mm or in a range between 100 µm and 2 mm. [15] Protection of an array of space solar cells (WSZ) according to any one of the preceding claims, characterized by that cooling for the string protection diodes (DS1-DS6) is provided by means of the metal strips and / or the metallized back of the DIEs.
Citation Information
Patent Citations
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