The disclosure is related generally to solar cell panels and more specifically to electrical connections made between solar cells in an array using corner conductors.
Generally, the fabrication process for solar cell arrays is highly manual and customizable. This is especially true for solar cell arrays that are spaceflight capable. There is a lack of automated means for manufacturing solar cell arrays, while preserving the ability for customization.
Typical spaceflight-capable solar cell panel assembly involves building long strings of solar cells. These strings are variable in length and can be very long, for example, up to and greater than 20 cells. Assembling such long, variable, and fragile materials is difficult, which has prevented automation of the assembly.
Existing solutions use solar cells assembled into CIC (cell, interconnect and coverglass) units. The CIC has metal foil interconnects connected to the front of the cell that extend in parallel from one side of the CIC. The CICs are located close to each other and the interconnects make connection to the bottom of an adjacent cell. Using these interconnects, the CICs are assembled into linear strings. These linear strings are built-up manually and then laid out to form a large solar cell array comprised of many strings of variable length.
Additionally, a bypass diode is used to protect the cells from reverse bias, when the cells become partially shadowed. The bypass diode generally connects the back contacts of two adjacent cells within the solar cell array.
Some small solar cell arrays attach solar cells to printed circuit board (PCBs) materials with embedded wiring. While this has some of the advantages sought for automated manufacturing, it is specific and limited in its design. As a result, they are not widely used in satellites.
When used in a satellite, the solar cell array is typically packaged as a panel. The dimensions of the panel are dictated by the needs of the satellite, including such constraints as needed power, as well as the size and shape necessary to pack and store the satellite in a launch vehicle.
Furthermore, the deployment of the panel often requires that some portions of the panel are used for the mechanical fixtures and the solar cell array must avoid these locations. In practice, the panel is generally rectangular, but its dimensions and aspect ratio vary greatly. The layout of the CICs and strings to fill this space must be highly customized for maximum power generation, which results in a fabrication process that is highly manual.
What is needed, then, is a means for promoting automated manufacturing of solar arrays, while preserving the ability for customization of solar cell arrays.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present disclosure describes a solar cell array comprised of at least one solar cell and a substrate for the solar cell. The solar cell has at least one cropped corner that defines a corner region, wherein the corner region includes at least one contact for making an electrical connection to the solar cell. The contact comprises a front contact on a front side of the solar cell and/or a back contact on a back side of the solar cell, wherein the contact extends into the corner region. The solar cell is attached to the substrate such that corner regions of adjacent solar cells are aligned, thereby exposing an area of the substrate where electrical connections between the solar cells are made. The electrical connections are up/down and/or left/right series connections that determine a flow of current through the cells.
Referring now to the drawings in which like reference numbers represent corresponding parts throughout:
In the following description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific example in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural changes may be made without departing from the scope of the present disclosure.
A new approach to the design of solar cell arrays, such as those used for spaceflight power applications, is based on electrical connections among the solar cells in the array.
This new approach rearranges the components of a solar cell and the arrangements of the solar cells in the array. Instead of having solar cells connected into long linear strings and then assembled onto a substrate, the solar cells are attached individually to a substrate, such that corner regions of adjacent cells are aligned on the substrate, thereby exposing an area of the substrate. Electrical connections between cells are made by corner conductors formed on or in the substrate in these corner regions. Consequently, this approach presents a solar cell array design based on individual cells.
Thus, a single laydown process and layout can be used in the fabrication of solar cell arrays. Current flow between solar cells will be assisted with conductors embedded in the substrate. These electrical connections define the specific characteristics of the solar cell array, such as its dimensions, stayout zones, and circuit terminations. This approach simplifies manufacturing, enables automation, and lowers costs and delivery times.
In
Adjacent strings of connected solar cells 14 can run parallel or anti-parallel. In addition, strings of connected solar cells 14 can be aligned or misaligned. There are many competing influences to the solar cell layout resulting in regions where cells are parallel or anti-parallel, aligned or misaligned.
The solar cell panel 10a includes a substrate 12 having one or more corner conductors 20 thereon. In one example, the substrate 12 is a multi-layer substrate 12 comprised of one or more Kapton® (polyimide) layers separating one or more patterned metal layers. The substrate 12 may be mounted on a large rigid panel 10a similar to conventional assembles. Alternatively, substrate 12 can be mounted to a lighter more sparse frame or panel 10a for mounting or deployment.
A plurality of solar cells 14 arranged in an array 22 are attached to the substrate 12. In this example, the array 22 is comprised of ninety-six (96) cells 14 arranged in four (4) rows by twenty-four (24) columns, but it is recognized that any number of cells 14 may be used in different implementations.
The solar cells 14 have cropped corners 24 that define corner regions 26, as indicated by the dashed circle. The solar cells 14 are attached to the substrate 12, such that corner regions 26 of adjacent ones of the solar cells 14 are aligned, thereby exposing an area 28 of the substrate 12. The area 28 of the substrate 12 that is exposed includes one or more of the corner conductors 20, and one or more electrical connections between the solar cells 14 and the corner conductors 20 are made in the corner regions 26 resulting from the cropped corners 24 of the solar cells 14.
In this example, the corner conductors 20 are conductive paths attached to, printed on, or integrated with the substrate 12, before and/or after the cells 14 are attached to the substrate 12, which facilitate connections between adjacent solar cells 14. The connections between the cells 14 and the corner conductors 20 are made after the cells 14 have been attached to the substrate 12.
In one example, four adjacent cells 14 are aligned on the substrate 12, such that four cropped corners 24, one from each solar cell 14, are brought together at the corner regions 26. The solar cells 14 are then individually attached to the substrate 12, wherein the solar cells 14 are placed on top of the corner conductors 20 to make the electrical connection between the solar cells 14 and the corner conductors 20.
The solar cells 14 may be applied to the substrate 12 as CIC (cell, interconnect and coverglass) units. Alternatively, a bare solar cell 14 may be applied to the substrate 12, and the coverglass later applied to the front of the solar cell 14 with a transparent adhesive. This assembly protects the solar cells 14 from damage from space radiation that would limit performance.
The solar cell 14 is fabricated having at least one cropped corner 24 that defines a corner region 26, as indicated by the dashed circle, such that the corner region 26 resulting from the cropped corner 24 includes at least one contact 32, 34 for making an electrical connection to the solar cell 14. In the example of
The cropped corners 24 increase utilization of the round wafer starting materials for the solar cells 14. In conventional panels, these cropped corners 24 result in unused space on the panel 10 after the solar cells 14 are attached to the substrate 12. The new approach described in this disclosure, however, utilizes this unused space. Specifically, metal foil interconnects, comprising the corner conductors 20, front contacts 32 and back contacts 34, are moved to the corner regions 26. In contrast, existing CICs have interconnects attached to the solar cell 14 front side, and connect to the back side (where connections occur) during stringing.
The current generated by the solar cell 14 is collected on the front side of the solar cell 14 by a grid 36 of thin metal fingers 38 and wider metal bus bars 40 that are connected to both of the front contacts 32. There is a balance between the addition of metal in grid 36, which reduces the light entering the solar cell 14 and its output power, and the reduced resistance of having more metal. The bus bar 40 is a low resistance conductor that carries high currents and also provides redundancy should a front contact 32 become disconnected. Optimization generally desires a short bus bar 40 running directly between the front contacts 32. Having the front contact 32 in the cropped corner 24 results in moving the bus bar 40 away from the perimeter of the solar cell 14. This is achieved while simultaneously minimizing the bus bar 40 length and light obscuration. Additionally, the fingers 38 are now shorter. This reduces parasitic resistances in the grid 36, because the length of the fingers 38 is shorter and the total current carried is less. This produces a design preference where the front contacts 32 and connecting bus bar 40 is moved to provide shorter narrow fingers 38.
During assembly, the solar cells 14 are individually attached to the substrate 12. This assembly can be done directly on a support surface, i.e., the substrate 12, which can be either rigid or flexible. Alternatively, the solar cells 14 could be assembled into the 2D grid of the array 22 on a temporary support surface and then transferred to a final support surface, i.e., the substrate 12.
One advantage of this approach is that the layouts illustrated in
Following solar cell 14 and diode 44 placement, there is another step where customization is accomplished. The front contacts 32 and back contacts 34 in the corner regions 26 of the solar cells 14 must be connected. This can be done in many combinations in order to route current through a desired path.
After attaching solar cells 14 to the substrate 12, connections are made between the solar cells 14 and the corner conductors 20. Front and back contacts 32, 34 of the solar cells 14 are present in each corner region 26 for attachment to the corner conductors 20. Interconnects for the front and back contacts 32, 34 of each of the solar cells 14 are welded, soldered, or otherwise bonded onto the corner conductors 20 to provide a conductive path 20, 32, 34 for routing current out of the solar cells 14.
Using the corner conductors 20, any customization can be made in the electrical connections. Adjacent solar cells 14 can be electrically connected to flow current in up/down or left/right directions as desired by the specific design. Current flow can also be routed around stay-out zones as needed. The length or width of the solar cell array 22 can be set as desired. Also, the width can vary over the length of the array 22.
This may be accomplished by the connection schemes shown in
The corner conductors 20 between solar cells 14 can be in many forms. They could be accomplished using wires that have electrical connections made on both ends, which could be from soldering, welding, conducting adhesive, or other process. In addition to wires, metal foil connectors, similar to the interconnects could be applied. Metal conductive paths or traces (not shown) can also be integrated with the substrate 12.
In summary, this new approach attaches the solar cells 14 individually to a substrate 12 such that the corner regions 26 of two, three or four adjacent solar cells 14 are aligned on the substrate 12. The solar cells 14 can be laid out so that the cropped corners 24 are aligned and the corner regions 26 are adjacent, thereby exposing an area of the substrate 12. Electrical connections between solar cells 14 are made in these corner regions 26 between front contacts 32 and back contacts 34 on the solar cells 14, bypass diodes 44, and corner conductors 20 on or in the exposed area 28 of the substrate 12, wherein these conductive paths are used to create a string of cells in a series connection 48, 50 comprising a circuit.
Examples of the disclosure may be described in the context of a method 54 of fabricating a solar cell, solar cell panel and/or satellite, comprising steps 56-68, as shown in
As illustrated in
Each of the processes of method 54 may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include without limitation any number of solar cell, solar cell panel, satellite or spacecraft manufacturers and major-system subcontractors; a third party may include without limitation any number of venders, subcontractors, and suppliers; and an operator may be a satellite company, military entity, service organization, and so on.
As shown in
At least one of the solar cells 14 has at least one cropped corner 24 that defines a corner region 26, such that an area 28 of the substrate 12 remains exposed when the solar cell 14 is attached to the substrate 12. When a plurality of solar cells 14 are attached to the substrate 12, the corner regions 26 of adjacent ones of the solar cells 14 are aligned, thereby exposing the area 28 of the substrate 12.
The area 28 of the substrate 12 that remains exposed includes one or more corner conductors 20 attached to, printed on, or integrated with the substrate 12, and one or more electrical connections between the solar cells 14 and the corner conductors 20 are made in a corner region 26 resulting from the cropped corner 24 of the at least one of the solar cells 14.
The corner region 26 resulting from the cropped corner 24 includes at least one contact, for example, a front contact 32 on a front side of the solar cell 14 and/or a back contact 34 on a back side of the solar cell 14, for making the electrical connections between the corner conductors 20 and the solar cell 14. The electrical connections may comprise up/down or left/right series connections that determine a flow of power through the solar cells 14, and may include one or more bypass diodes 44.
The description of the examples set forth above has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the examples described. Many alternatives, modifications and variations may be used in place of the specific elements described above.
To facilitate the electrical connections, it can be advantageous to have corner conductors 20 fabricated onto or within the substrate 12 before the solar cells 14 are attached. This would be somewhat similar to a PCB where thin metal traces are present. In addition, multiple current pathways can be built into the corner conductors 20. Moreover, one or more conductive jumpers (not shown) may be added to the corner conductors 20 to determine which pathways are used. Alternatively, one or more conductive pathways may be removed from the corner regions to facilitate the determination of the current pathways between solar cells 14.
Preferably, the substrate 12 includes conductive paths throughout, including conductive paths on its surface (e.g., the corner conductors 20), beneath its surface and beneath the plane of the solar cells 14 (not shown), or both on its surface and beneath its surface. The conductive paths, such as the corner conductors 20, are electrically insulated from the solar cells 14. In addition, the corner conductors 20 provide access to one or more of other conductive paths of the substrate 12. As a result, this design would virtually eliminate any manual wiring on the panel 10a.
It is desirable to have the greatest area possible on the panel 10a dedicated to the solar cells 14 and have small corner regions. However, a desire to provide all possible permutations of cell-to-cell connections in the corner regions will motivate for large corner regions. Balancing these competing interest will depend on the design.
Competition between interests can be avoided by using the power routing module (PRM) 30. The PRM 30 can embody some or all of the corner conductors 20 between the solar cells 14 and can be applied to the corner region. Different versions of the PRM 30 facilitate purpose-made wiring. Moreover, the PRM 30 can shrink the size of the corner region 26, while providing for the needed variation in conducting pathways, as compared to having the conductive paths on the substrate 12.
Printing corner conductors 20 directly into the corner region 26 is another approach to make purpose-made wiring. This requires less conducting pathway options and can be smaller.
Another variation is the possibility of adding a multiplexing switch module (not shown) into the corner regions 26. The multiplexing switch module could be integrated into the substrate 12 or the PRM 30. The multiplexing switch module would be programmed to make the desired electrical pathways between the solar cells 14 and the corner conductors 20.
For example, the multiplexing switch module could be programmed once and “burned in,” or could be addressable and altered during operation. When burned-in, the multiplexing switch module may be programmed through a temporary external connection. There may also be additional conductors in the substrate 12 that address and program the operation of all of the multiplexing switch modules that may be installed across the panel 10a. In addition, a multiplexing switch module that can be addressed and operate while in orbit will have great advantages.
The assembly of the solar cells 14 in arrays in this manner will greatly simplify manufacturing and enable automation while preserving the ability for customization. The key is that the electrical connections between adjacent solar cells 14 is completed on the substrate 12 using the corner conductors 20. Thus, the panel 10a layout and manufacturing of the layout is independent of the final design and can be common for virtually any design.
This application claims the benefit under 35 U.S.C. Section 119(e) of the following co-pending and commonly-assigned applications: U.S. Provisional Application Ser. No. 62/394,636, filed on Sep. 14, 2016, by Eric Rehder, entitled “SOLAR CELL ARRAY CONNECTIONS,” attorneys' docket number 16-0878-US-PSP (G&C 147.211-US-P1); U.S. Provisional Application Ser. No. 62/394,616, filed on Sep. 14, 2016, by Eric Rehder, entitled “CORNER CONNECTORS FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-0435-US-PSP (G&C 147.212-US-P1); U.S. Provisional Application Ser. No. 62/394,623, filed on Sep. 14, 2016, by Eric Rehder, entitled “PREFABRICATED CONDUCTORS ON A SUBSTRATE TO FACILITATE CORNER CONNECTIONS FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-0436-US-PSP (G&C 147.213-US-P1); U.S. Provisional Application Ser. No. 62/394,627, filed on Sep. 14, 2016, by Eric Rehder, entitled “SELECT CURRENT PATHWAYS IN A SOLAR ARRAY,” attorneys' docket number 16-0437-US-PSP (G&C 147.214-US-P1); U.S. Provisional Application Ser. No. 62/394,629, filed on Sep. 14, 2016, by Eric Rehder, entitled “MULTILAYER CONDUCTORS IN A SOLAR ARRAY,” attorneys' docket number 16-0438-US-PSP (G&C 147.215-US-P1); U.S. Provisional Application Ser. No. 62/394,632, filed on Sep. 14, 2016, by Eric Rehder, entitled “REWORK AND REPAIR OF COMPONENTS IN A SOLAR ARRAY,” attorneys' docket number 16-0439-US-PSP (G&C 147.216-US-P1); U.S. Provisional Application Ser. No. 62/394,649, filed on Sep. 14, 2016, by Eric Rehder, entitled “POWER ROUTING MODULE FOR A SOLAR ARRAY,” attorneys' docket number 16-0440-US-PSP (G&C 147.217-US-P1); U.S. Provisional Application Ser. No. 62/394,666, filed on Sep. 14, 2016, by Eric Rehder, entitled “POWER ROUTING MODULE WITH A SWITCHING MATRIX FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-0441-US-PSP (G&C 147.218-US-P1); U.S. Provisional Application Ser. No. 62/394,667, filed on Sep. 14, 2016, by Eric Rehder, entitled “NANO-METAL CONNECTIONS FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-0442-US-PSP (G&C 147.219-US-P1); U.S. Provisional Application Ser. No. 62/394,371, filed on Sep. 14, 2016, by Eric Rehder, entitled “BACK CONTACTS FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-0443-US-PSP (G&C 147.220-US-P1); U.S. Provisional Application Ser. No. 62/394,641, filed on Sep. 14, 2016, by Eric Rehder, entitled “PRINTED CONDUCTORS IN A SOLAR CELL ARRAY,” attorneys' docket number 16-0614-US-PSP (G&C 147.228-US-P1); and U.S. Provisional Application Ser. No. 62/394,672, filed on Sep. 14, 2016, by Eric Rehder, Philip Chiu, Tom Crocker and Daniel Law, entitled “SOLAR CELLS FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-2067-US-PSP (G&C 147.229-US-P1); all of which applications are incorporated by reference herein. This application claims the benefit under 35 U.S.C. Section 120 of the following co-pending and commonly-assigned applications: U.S. Utility application Ser. No. ______, filed on same date herewith, by Eric Rehder, entitled “PREFABRICATED CONDUCTORS ON A SUBSTRATE TO FACILITATE CORNER CONNECTIONS FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-0436-US-NP (G&C 147.213-US-U1); U.S. Utility application Ser. No. ______, filed on same date herewith, by Eric Rehder, entitled “REWORK AND REPAIR OF COMPONENTS IN A SOLAR ARRAY,” attorneys' docket number 16-0439-US-NP (G&C 147.216-US-U1); U.S. Utility application Ser. No. ______, filed on same date herewith, by Eric Rehder, entitled “POWER ROUTING MODULE FOR A SOLAR ARRAY,” attorneys' docket number 16-0440-US-NP (G&C 147.217-US-U1); U.S. Utility application Ser. No. ______, filed on same date herewith, by Eric Rehder, entitled “POWER ROUTING MODULE WITH A SWITCHING MATRIX FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-0441-US-NP (G&C 147.218-US-U1); U.S. Utility application Ser. No. ______, filed on same date herewith, by Eric Rehder, entitled “NANO-METAL CONNECTIONS FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-0442-US-NP (G&C 147.219-US-U1); and U.S. Utility application Ser. No. ______, filed on same date herewith, by Eric Rehder, Philip Chiu, Tom Crocker, Daniel Law and Dale Waterman, entitled “SOLAR CELLS FOR A SOLAR CELL ARRAY,” attorneys' docket number 16-2067-US-NP (G&C 147.229-US-U1); all of which applications claim the benefit under 35 U.S.C. Section 119(e) of the co-pending and commonly-assigned provisional applications listed above: 62/394,636; 62/394,616; 62/394,623; 62/239,627; 62/394,629; 62/394,632; 62/394,649; 62/934,666; 62/394,667; 62/694,371; 62/394,641; and 62/394,672; and all of which applications are incorporated by reference herein.
This invention was made with government support under Contract No. FA9453-09C-0373 awarded by the Air Force Research Laboratory (AFRL). The government has certain rights in this invention.
| Number | Date | Country | |
|---|---|---|---|
| 62394636 | Sep 2016 | US | |
| 62394616 | Sep 2016 | US | |
| 62394623 | Sep 2016 | US | |
| 62394627 | Sep 2016 | US | |
| 62394629 | Sep 2016 | US | |
| 62394632 | Sep 2016 | US | |
| 62394649 | Sep 2016 | US | |
| 62394666 | Sep 2016 | US | |
| 62394667 | Sep 2016 | US | |
| 62394371 | Sep 2016 | US | |
| 62394641 | Sep 2016 | US | |
| 62394672 | Sep 2016 | US |