Solar cell array with variable string length - Patents.com

Abstract

To provide a solar cell array including current flow path changing means for adapting to voltage change due to breakdown of the solar cell caused by radiation damage, and the like.SOLUTION: In a solar cell array consisting of one or more than one solar cells 14 attached to a substrate, the substrate includes one or more than one electrical connections 20 with the solar cells 14, and one or more than one switches 54 for changing the string length for one or more than one solar cells 14, by changing the current flow path between one or more than one solar cells 14 and one or more than one electrical connections 20.SELECTED DRAWING: Figure 15

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to solar cell panels, and more particularly to solar cell arrays having variable string lengths. [Background technology]

[0002] A typical space-capable solar cell panel assembly involves building a solar cell array consisting of long strings of solar cells. These strings can be of variable length, i.e. number of solar cells, and can be very long.

[0003] Conventional solar cell arrays are built with a fixed number of solar cells to generate a required output voltage. The fixed number of solar cells must be sized under the most difficult conditions, which are the hottest operating periods, including the highest doses of electron and proton radiation. In particular, existing solutions create strings that are sized for the worst-case environment.

[0004] For 100V operation, this could be up to 55 solar cells. At the start of a solar cell array, radiation damage is minimal and it could take up to 45 solar cells to reach 100V. Thus, at start-up, approximately 18% (10 / 55) of the solar cells are not producing usable power.

[0005] This will vary with operating temperature and the cumulative dose of high energy electrons and protons in the space environment. Most importantly, it is the voltage that changes during the life of the solar cell array.

[0006] Therefore, what is needed is a means to accommodate changes to the operation of a solar cell array during its lifetime. Summary of the Invention

[0007] To overcome the limitations described above, as well as others that will become apparent upon reading and understanding this specification, the present disclosure describes a solar cell array consisting of one or more solar cells attached to a substrate, the substrate including one or more electrical connections to the solar cells, and the substrate including one or more switches for changing the string length of one or more of the solar cells by altering the current flow path between one or more of the solar cells and one or more of the electrical connections.

[0008] When at least one of the solar cells having one or more trimmed corners is attached to the substrate, an area of ​​the substrate remains exposed, and the area of ​​the substrate that remains exposed includes at least one of the switches. At least one of the solar cells is attached to the substrate such that corner regions defined by the trimmed corners of adjacent ones of the at least one of the solar cells are aligned, thereby exposing an area of ​​the substrate. At least one of the switches is located within the corner region defined by the trimmed corner adjacent to the at least one of the solar cells.

[0009] A switch varies the length of one or more strings of the solar cells in response to a control signal, the switch varying the string length to allow for series connection between multiple strings and reconfigurability of the output, the switch being a single-pole single-throw (SPST) switch or a dual-pole single-throw (DPST) switch.

[0010] The substrate includes one or more traces connected to switches for making electrical connections between the solar cells.

[0011] Reference is now made to the drawings, in which like reference numerals represent corresponding parts throughout. [Brief description of the drawings]

[0012] [Figure 1] 1 shows a conventional structure of a solar cell panel. [Diagram 2] 1 shows a conventional structure of a solar cell panel. [Diagram 3] 1A and 1B show an improved structure of a solar cell panel according to one embodiment. [Figure 4] 1A and 1B show alternative structures of a solar cell panel according to one example. [Diagram 5] 5 illustrates a front view of an exemplary solar cell that may be used in the improved solar cell panels of FIGS. 3 and 4. [Figure 6] 6 illustrates a backside of the exemplary solar cell of FIG. 5. [Figure 7] 1 shows cells arranged in a two-dimensional (2D) grid of an array, according to one example. [Figure 8] 1 shows an example of an array in which one or more bypass diodes are added to the exposed areas of the substrate in the corner regions. [Figure 9] An example is shown in which a bypass diode is attached to the backside of the cell, with the interconnect or contact for the bypass diode extending into the corner region between the front and back contacts. [Figure 10] FIG. 10 shows a front view of the example of FIG. 9, in which the interconnects or contacts for the bypass diodes extend into the corner region between the front and back contacts. [Figure 11] 11 shows the cells of Figures 9 and 10 arranged in a 2D grid array and attached to a substrate, with bypass diodes attached to the backside of the cells and contacts for the bypass diodes extending into the corner regions of the cells. [Figure 12] 1 illustrates an upward / downward series connection between cells of an array according to one embodiment. [Figure 13] 1 illustrates left / right series connections between cells of an array according to one embodiment. [Figure 14] A shows an open switch, while B, C and D show three different configurations with one, two and one switch closed, respectively. [Figure 15]A corner connection layout with single-pole, single-throw (SPST) switches is shown. [Figure 16] 1 shows an implementation of a switch for varying the length of a string of solar cells. [Figure 17] FIG. 17 is a layout showing how short segments of solar cells can be joined into longer strings. [Figure 18] 1 illustrates switching of solar cells to change the length of the string. [Figure 19] 1 shows a reconfigurable array of solar cells. [Figure 20] A shows how multiple partial strings are coupled together to provide the required string length and output voltage, and B shows groups of solar cells each split into two portions, with one portion from each group of solar cells being coupled together to provide the required string length. [Figure 21] 1 shows the layout of a reconfigurable solar cell made of three flex sheets, each with two sections. [Figure 22] 22 shows how switches can be used to reconfigure the solar cell of FIG. 21. [Figure 23] According to one example, a method for manufacturing a solar cell, a solar cell panel, and / or a satellite is described. [Figure 24] 1 shows the resulting satellite having a solar cell panel made of solar cells, according to one example. [Diagram 25] 1 is a diagram of a solar cell panel in the form of a functional block diagram, according to one example. [Figure 26] 14A through 14E show experimental results in which a solar cell array using a flex circuit board based on the corner conductor design was constructed to demonstrate reconfiguration of the string length of the array. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] In the following description, references are made to the accompanying drawings that form a part hereof, and which are shown for the purpose of illustrating specific examples in which the present disclosure may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present disclosure.

[0014] An emerging approach to the design of solar cell arrays, for example for spaceflight power applications, is based on electrical connections between the solar cells in the array.

[0015] These new approaches rearrange the components of a solar cell and the arrangement of solar cells within an array. Instead of connecting the solar cells into long linear strings and then assembling them on a substrate, the solar cells are individually attached to the substrate such that the corner regions of adjacent cells are aligned on the substrate, exposing an area of ​​the substrate. Electrical connections between the cells are made by corner conductors formed in these corner regions on or within the substrate. As a result, this approach presents a solar cell array design based on individual cells.

[0016] Thus, a single laydown process and layout can be used to manufacture the solar cell array. Current flow between the solar cells is assisted by conductors embedded in the substrate. These electrical connections define the specific characteristics of the solar cell array, such as its dimensions, stayout areas, and circuit terminations. This approach simplifies manufacturing, enables automation, and reduces costs and delivery times.

[0017] 1 and 2 show a conventional structure of a solar cell panel 10, including a substrate 12, a plurality of solar cells 14 arranged in an array, and electrical connectors 16 between the solar cells 14. A half-sized solar cell 14 is shown in FIG. 1, and a full-sized solar cell 14 is shown in FIG. 2. The space solar cells 14 are made from a circular germanium (Ge) substrate starting material. These are later processed into a quasi-rectangular shape for more dense loading on the solar cell panel 10. The wafer is often diced into one or two solar cells 14, which are referred to herein as half-sized or full-sized solar cells 14. Electrical connectors 16 that electrically connect the solar cells 14 are made along the long parallel edges between the solar cells 14. Strings of connected solar cells 14 can be constructed to have any number of solar cell 14 lengths, so these series connections (cell-to-cell) are completed without being attached to a substrate. Once completed, the strings of solar cells 14 are applied to and attached to a substrate 12.

[0018] 2, wires 18 are attached to the ends of the strings of solar cells 14 either to electrically connect the strings to other strings or to terminate the wires into a circuit where the current in the array of solar cells 14 is cut off. The string-to-string and circuit termination connections are typically made on the substrate 12, typically using wires 18. However, some solar cell panels 10 use printed circuit board (PCB) type material with conductors inlaid therein.

[0019] 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 on the layout of the solar cells 14, resulting in regions where the solar cells 14 are parallel or anti-parallel, aligned or misaligned.

[0020] Figures 3A and 3B show an improved arrangement and structure of solar cell panel 10a according to one embodiment, with Figure 3B being an enlarged view of the detail within the dashed circle in Figure 3A. In Figures 5 through 13, various components of solar cell panel 10a are shown and described in more detail.

[0021] The solar cell panel 10a includes a substrate 12 for the solar cells 14 having one or more corner conductors 20 thereon. In one embodiment, the substrate 12 is a multi-layer substrate 12 consisting of one or more Kapton® (polyimide) layers separating one or more patterned metal layers. The substrate 12 may be attached to a large rigid substrate 10a similar to conventional assembly. Alternatively, the substrate 12 may be attached to a lighter, thinner frame or panel 10a for mounting or deployment.

[0022] A plurality of solar cells 14 are attached to substrate 12 in a two-dimensional (2-D) grid of array 22. In this example, array 22 is comprised of 96 solar cells 14 arranged in 4 columns by 24 rows, although it is recognized that any number of solar cells 14 may be used in different embodiments.

[0023] The solar cells 14 have trimmed corners 24 that define corner regions 26, as indicated by the dashed circles. The solar cells 14 are attached to the substrate 12 such that the corner regions 26 of adjacent solar cells 14 are aligned, thereby exposing an area 28 of the substrate 12. The exposed area 28 of the substrate 12 includes one or more corner conductors 20, and one or more electrical connections are made between the solar cells 14 and the corner conductors 20 within the corner regions 26 created by the trimmed corners 24 of the solar cells 14.

[0024] In this embodiment, corner conductors 20 are conductive paths attached to, printed on, embedded within, or deposited on substrate 12 before and / or after solar cells 14 are attached to substrate 12 to facilitate connections between adjacent solar cells 14. The connections between the solar cells 14 and corner conductors 20 are made after the solar cells 14 are attached to substrate 12.

[0025] In one embodiment, four adjacent solar cells 14 are aligned on the substrate 12 such that the four trimmed corners 24, one from each solar cell 14, come together at corner regions 26. The solar cells 14 are then individually attached to the substrate 12. At this point, the solar cells 14 rest on the corner conductors 20, and electrical connections are made between the solar cells 14 and the corner conductors 20.

[0026] The solar cells 14 may be attached to the substrate 12 as a CIC (cell, interconnect, cover glass) unit. Alternatively, uncoated solar cells 14 may be assembled on the substrate 12, and then interconnects may be attached to the solar cells 14, followed by a cover glass for a single solar cell 14, a cover glass for a multi-cell solar cell 14, a multi-cell polymer cover sheet, or a spray-on encapsulant. This assembly protects the solar cells 14 from damage that could limit their performance.

[0027] 4A and 4B show an alternative structure of solar cell panel 10a, according to one example, with FIG. 4B being an expanded detail view of the dashed circle in FIG. 4A. In this example, only a few corner conductors 20 are printed on or embedded into substrate 12. Instead, most of the corner conductors 20 are contained within a power routing module (PRM) 30 that is attached to substrate 12.

[0028] FIG. 5 shows a front view of an exemplary solar cell 14 that may be used in the improved solar cell panel 10a of FIGS. 3A-B and 4A-B. The solar cell 14, which is a CIC unit, is a half-size solar cell 14. (A full-size solar cell 14 could also be used.)

[0029] As indicated by the dashed circle, the solar cell 14 is fabricated with at least one trimmed corner 24 that defines a corner region 26 that includes at least one contact 32, 34 that makes an electrical connection with the solar cell 14. In the embodiment shown in Figure 5, the solar cell 14 has two trimmed corners 24, each of which has a front contact 32 on the front side of the solar cell 14 and a back contact 34 on the back side of the solar cell 14, with the contacts 32 and 34 extending into the corner region 26. (A full-sized solar cell 14 has four trimmed corners 24, each of which has one front contact 32 and one back contact 34.)

[0030] The trimmed corners 24 encourage the use of circular wafers as the starting material for the solar cells 14. In a conventional panel 10, these trimmed corners 24 result in unused space on the panel 10 after the solar cells 14 are attached to the substrate 12. However, the new approach described in this disclosure utilizes this unused space. Specifically, the metal foil interconnects, including the corner conductors 20, front contacts 32, and back contacts 34, are moved to the corner regions 26. In contrast, existing CICs have the interconnects attached to the front of the solar cells 14 and are connected to the back (where splicing occurs) during string fabrication.

[0031] Current generated by the solar cells 14 is collected at the front of the solar cells 14 by a grid 36 of thin metal fingers 38 and wider metal bus bars 40 connected to either front contact 32. There is a trade-off between adding metal to the grid 36 to reduce the light entering the solar cells 14 and reduce the power output of the solar cells 14, and the reduced resistance of the additional metal. The bus bars 40 are low resistance conductors that carry high currents and also provide redundancy in case a front contact 32 is disconnected. Generally, optimization requires a short bus bar 40 that runs directly between the front contacts 32. Having the front contacts 32 in the trimmed corners 24 results in the bus bar 40 being away from the perimeter of the solar cells 14. This is accomplished while at the same time minimizing the length of the bus bar 40 and minimizing light shading. Additionally, this also shortens the fingers 38. This reduces the parasitic resistance in the grid 36 because the fingers 38 are shorter and therefore the total amount of current carried. This has led to a design in which the front contacts 32 and connecting busbars 40 are moved to provide shorter, thinner fingers 38 .

[0032] Figure 6 shows the back side of the example solar cell 14 of Figure 5. The back side of the solar cell 14 has a metal back layer 42 that connects to both back contacts 34.

[0033] 7 illustrates solar cells 14 arranged in a 2D grid in an array 22, according to one embodiment. The array 22 includes a plurality of solar cells 14 attached to a substrate 12 such that corner regions 26 of adjacent solar cells 14 are aligned, thereby exposing an area 28 of the substrate 12. Electrical connections (not shown) between the solar cells 14 are made in the exposed area 28 of the substrate 12 using front and back contacts 32, 34 of the solar cells 14 and corner conductors 20 (not shown) formed on or in the exposed area 28 of the substrate 12.

[0034] During assembly, the solar cells 14 are individually attached to the substrate 12. This assembly can occur 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 in the 2D grid of the array 22 on a temporary support surface and then transferred to the final support surface, i.e., the substrate 12.

[0035] 8 shows one embodiment of an array 22 in which one or more bypass diodes 44 have been added to exposed areas 28 in corner regions 26 of substrate 12 for use with one or more electrical connections. The bypass diodes 44 protect the solar cells 14 when they are unable to generate current, which may be due to being partially shaded, causing the solar cells 14 to become reverse biased. In one embodiment, the bypass diodes 44 are attached to the substrate 12 in the corner regions 26, separate from the solar cells 14.

[0036] FIG. 9 shows one embodiment in which a bypass diode 44 is attached to the back surface of the solar cell 14, with an interconnect or contact 46 for the bypass diode 44 connected to the back surface layer 42 and extending into the corner region 26 between the front contact 32 and the back contact 34.

[0037] FIG. 10 shows a front view of the embodiment of FIG. 9 in which an interconnect or contact 46 for a bypass diode 44 (not shown) extends into the corner region 26 between the front contact 32 and the back contact 34.

[0038] FIG. 11 shows the solar cells 14 of FIGS. 9 and 10 arranged in a 2D grid in an array 22 and attached to a substrate 12, but with bypass diodes 44 (not shown) attached to the backside of the solar cells 14, with contacts 46 for the bypass diodes 44 extending into the corner regions 26 of the solar cells 14.

[0039] One advantage of this approach is that the layouts shown in Figures 7, 8, and 11 are generalized layouts. In particular, these layouts can be repeated over any customer desired dimensions of panel 10a. This greatly simplifies the assembly, modification, testing, and inspection processes.

[0040] The placement of the solar cells 14 and bypass diodes 44 is conventional. Electrically connecting the solar cells 14 in series and terminating the strings is a significant customization for the end customer and is done separately from the layout. In the corner regions 26 of the solar cells 14, the front contacts 32 and back contacts 34 must be connected. This can be done in many combinations to route the current in the desired path.

[0041] Connections are made between the solar cells 14 and the corner conductors 20. A front contact 32 and a back contact 34 of the solar cells 14 are in each corner region 26 for attachment to the corner conductors 20. The interconnects for the front contact 32 and back contact 34 of each solar cell 14 are welded, soldered, or otherwise bonded to the corner conductors 20 to provide a conductive path 20, 32, 34 that routes electrical current to the exterior of the solar cell 14.

[0042] Corner conductors 20 can be used to provide any customization in electrical connections. Adjacent solar cells 14 can be electrically connected to pass current in an up / down or left / right direction as desired for a particular design. Current can also be routed around stayout areas if desired. The length and width of the solar cell array 22 can be configured as desired. Additionally, the width of the array 22 can vary along its length.

[0043] In one embodiment, the electrical connections are series connections that determine the flow of electrical current through the solar cells 14. This can be accomplished by the connection schemes shown in Figures 12 and 13, where Figure 12 shows up / down series connections 48 between the solar cells 14 of the array 22 and Figure 13 shows left / right series connections 50 between the solar cells 14 of the array 22. In both Figures 12 and 13, these series connections 48, 50 are electrical connections between the front and back contacts 32, 34 of the solar cells 14 and the bypass diodes 44, and these series connections are made using corner conductors 20 formed on or in the exposed areas 28 of the substrate 12. These series connections 48, 50 determine the flow of electrical current (power) through the solar cells 14 as indicated by arrows 52.

[0044] The corner conductors 20 between the solar cells 14 can be in a variety of forms. The corner conductors 20 could be completed using wires with electrical connections made at both ends that could be soldered, welded, conductive adhesive, or other processes. In addition to wires, metal foil connectors similar to interconnects could also be applied. Metal conductor paths or traces (not shown) could also be incorporated into the substrate 12.

[0045] In essence, this new approach attaches solar cells 14 individually to the 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 such that the trimmed corners 24 are aligned to abut the corner regions 26, thereby exposing areas 28 of the substrate 12. Electrical connections between the solar cells 14 are made within these corner regions 26 between the front and back contacts 32 of the solar cells 14, the bypass diodes 44, and the corner conductors 20 on or within the exposed areas 28 of the substrate 12, which conductive paths are used to create strings of solar cells 14 in series connections 48, 50 that comprise the circuit.

[0046] Solar cell array with variable string length - Patents.com A satellite power system requires power generated at a specific voltage produced by a number of series-connected solar cells 14. The voltage produced by each solar cell 14 varies mainly depending on the operating temperature, as well as the electron and proton bombardment history. The string is typically a fixed length of solar cells 14 and is designed to have enough solar cells 14 to reach the required voltage during operation. During many parts of the mission, the string is producing more voltage than required. Effectively, one or more solar cells 14 do not contribute power. This disclosure describes how to reconfigure the string length during operation so that power can be collected from each solar cell 14 throughout the mission. This results in the ability to produce strings that operate at a constant total output voltage and produce higher power from the solar cell array 22.

[0047] A conventional triple junction solar cell 14 produces a maximum power of approximately 1.2 A and 2.22 V. This will vary with operating temperature and the cumulative dose of high energy electrons and protons in the space environment.

[0048] The most important is the varying voltage. Power systems often collect current at a certain voltage known as the load voltage. From the satellite's beginning of life (BOL) to its end of life (EOL), the voltage can drop from 2.2V to 1.8V. To reach the load voltage, which can be from 20V to 100V, many solar cells 14 are connected in series and each solar cell 14 adds to the string voltage.

[0049] In one example, 45 solar cells 14 may be required at the BOL to have a maximum power point close to 100V, while at the EOL, 55 solar cells 14 may be required to have a maximum power point of 100V. Thus, the additional 10 solar cells 14 at the BOL do not contribute any power.

[0050] The string length can be reconfigured during operation by implementing switches in the solar cell array 22. Specifically, the solar cell array 22 is reconfigured to have a string length that produces a maximum power point close to the load voltage.

[0051] For example, a solar cell array 22 with 990 solar cells 14 can be split into many strings to power a 100V power system. To power at 100V at EOL, the solar cell array 22 would require 18 strings with a maximum power point of 100V, with 55 solar cells 14 each, requiring a long string. The power output would be 18 x 100V x 1.2A = 2160W. A conventional solar cell array with a fixed string length would provide this power at BOL and EOL. There may be some variation in current and fill factor due to illumination, but that is a secondary factor in this discussion.

[0052] Reconfiguring the string length would provide a much higher power level at the BOL. At the BOL, the solar cell array 22 could be reconfigured to use 22 strings, each with a length of 45 solar cells 14, to generate a maximum power point of 100V. The power output would be 22 x 100V x 1.2A = 2640W. This is 22% more power than the previous example. The solar cell array 22 could be reconfigured during the mission to change the string length from 45 to 55 solar cells 14. This would maintain the voltage at the maximum power point close to the load voltage of 100V, providing optimal power.

[0053] Reconfigurable array 22 may also be advantageous in interplanetary missions where radiation and operating temperatures vary widely, thereby changing the voltages on solar cells 14 .

[0054] In other applications, the load voltage may vary. For example, in the early stages of operation, a satellite may use electric propulsion to move into its orbital position. The electric propulsion system may prefer a higher load voltage compared to other stages of operation of the mission. Reconfigurability could be implemented to change the string length, and the maximum power point of the string could be changed to 160V or 200V or 300V for electric propulsion and 100V for other stages of the mission.

[0055] Reconfigurability requires that several switches be introduced into the solar cell array 22. Wiring these switches into a conventional solar cell array requires inserting end tabs between the solar cells and wiring and the switches. The switches would also require signal wires to communicate the desired state (open or closed). This requires significant effort, cost, and panel area. In addition, the extra connections increase the risk of developing problems. These costs and risks outweigh the benefits and preclude the building of reconfigurable arrays.

[0056] However, for a solar cell array 22 that uses a corner conductor 20 layout, the cost to implement the reconfigurable array 22 changes dramatically.

[0057] Figures 14A, 14B, 14C and 14D show switches 54 used to change the current flow path between the solar cells 14 and the electrical connections. In these figures, the switches 54 are single-pole single-throw (SPST) switches 54 packaged together in pairs, although other switches 54 may be used and the switches 54 may be packaged singly, in pairs, or as desired.

[0058] Each of the pair of SPST switches 54 may be controlled independently or together using one or more control signals (not shown). Figure 14A shows a pair of SPST switches 54 both open, Figure 14B shows a pair of SPST switches 54 with the left side open and the right side closed, Figure 14C shows a pair of SPST switches 54 both closed, and Figure 14D shows a pair of SPST switches 54 with the left side closed and the right side open.

[0059] 15 shows a layout in which the switches 54 are located in the corner region 26. A pair of SPST switches 54 in the top center of the corner region 26 connect the back contact 34 of the upper left solar cell 14 to either the string output line 56 or the bypass diode 4 4th grade and the next solar cell 14 at the bottom left Either in series . Photocurrent flows from the back contact 34 of the upper left solar cell 14 to the front contact 32 of the lower left solar cell 14. A pair of SPST switches 54 on the left side of the corner region 26 enable the front contact 32 of the lower left solar cell 14 to be connected in series with the back contact 34 of the upper left solar cell 14, and enable the front contact 32 of the lower left solar cell 14 to be connected to the string output wire 56.

[0060] These switches 54 allow the solar cells 14 to either have a series connection to another solar cell 14 or to be terminated to buried V+ or V- string output lines 56. Additionally, the switches 54 allow the solar cells 14 to be terminated with multiple connection paths. Similarly, the switches 54 can also have several connection paths, all following the logic described herein.

[0061] The connections between the solar cells 14 on the right side of the corner region 26 are a 180 degree mirror image of the connections between the solar cells 14 on the left side of the corner region 26. However, the configuration of the SPST switches 54 on the left side is reversed. On this left side, current flows from the back contact 34 of the bottom right solar cell 14 to the buried V+ string output line 56 at the end of the string. The front contact 32 of the top right solar cell 14 is connected to the V- string output line 56.

[0062] The electrical connections made in the corner regions 26 use a common layout of the solar cells 14, regardless of whether they have a series connection or a circuit output. No bus bars or wiring are required, saving labor and area of ​​the panel 10a. Furthermore, the layout of the electrical connections in the corner regions 26 takes advantage of the ability to include traces patterned on the substrate 12. A more or less complex wiring layout on the substrate 12 adds no or only minimal cost. The additional traces required by the switches 54 are easily constructed with little additional labor. This combination of properties makes it ideally suited for a reconfigurable solar cell array 22.

[0063] A pair of SPST switches 54 may be operated such that one SPST switch 54 is closed while the other SPST switch 54 is open, which could be implemented using a double-pole single-throw (DPST) switch 54. Additionally, a pair of SPST or DPST switches 54 could be implemented with one or more control signals. These SPST or DPST switches 54 could be electromechanical or microelectromechanical system (MEMS) relays in which a solid conductor is mechanically bent to make and break a conductive path. Field effect transistor devices are another available switch 54 constructed from silicon (Si), silicon carbide (SiC), or gallium nitride (GaN).

[0064] FIG. 16 shows a group 58 of solar cells 14 labeled 1 through 15. This group 58 can be split into two strings. Between the solar cells 14 labeled 11 and the solar cells 14 labeled 15, there are eight switches 54 in series that control the length of each of the two strings, and there is a ninth switch 54 coupled between the solar cell 14 labeled 15 and the outputs V1+ and V2+. The switches 54 can make the length of the first string between solar cells 14 11 through 15, and the length of the second string between solar cells 14 0 through 4. There are four fixed output lines, the outputs of the first string are V1- and V1+, and the outputs of the second string are V2- and V2+.

[0065] V1- is always set from the beginning of the string before the solar cell 14 labeled 1. V1+ can be at any point after the solar cell 14 labeled 11 to after the solar cell 14 labeled 15, and can be in the configuration at end of life (EOL) when the voltage of the solar cell 14 drops. As depicted, V1+ terminates after the solar cell 14 labeled 13, and V2+ always terminates after the solar cell 14 labeled 15. As depicted, V2- terminates before the solar cell 14 labeled 14.

[0066] This solar cell array 22 allows the first string to be reconfigured to have the required string length and optimize the operating voltage. The second string will have a lower voltage output. Multiple copies of the second string using other groups 58 may need to be connected in series to reach the load voltage.

[0067] FIG. 17 is a layout showing how strings are combined for a desired voltage output, showing 14 groups 58 of solar cells 14. Each group 58 consists of the solar cells 14 and switches 54 shown in FIG. 16. The first string of solar cells 14 in each group 58 produces the desired voltage from 11 to 15 solar cells 14 connected to outputs V1, V2, ..., V14. The second string of solar cells 14 in each group 58 produces the desired voltage from 0 to 4 solar cells 14 connected to outputs Va, Vb, ..., Vn.

[0068] The layout of FIG. 17 shows two stages of groups 58 with an additional switch 54 between the stages for connecting a second string from each of the groups 58. In this example, the string output Va- terminates directly to V15-. Va+ is connected to Vb- via two pairs of switches 54. The same happens between Vb+ and Vc- and continues across the groups 58. As shown, the switches 54 allow a series connection from Va to Vg. In this example, the first string of each group 58 is 13 solar cells 14 long and the second string is 2 solar cells 14 long. The combination of the segments that output Va to Vg is a string 14 solar cells 14 long. These are 14 solar cells 14 long and combine for an output V15 that generates enough voltage to be utilized by the system.

[0069] Between Vg+ and Vh-, the output is terminated with switches 54a. These termination switches 54a indicate the change of state of the switch elements 54. The termination switches 54 terminate Vg+ to V15+ and Vh- to V16-. Vh to Vn are then connected in series to create another string of 14 solar cells 14. Vn+ is connected to V16+.

[0070] As a result, FIG. 16 shows how groups 58 of solar cells 14 can be reconfigured between long first strings having a desired voltage output and short second strings that are a fraction of the desired voltage, while FIG. 17 shows how these short second strings can be combined to produce the desired voltage.

[0071] The string length and layout can be modified as needed. This disclosure focuses on the switching topology. It would take extensive manual effort to implement this wiring and turn on the switches of a conventional solar cell array. The solar cell array 22 of the present disclosure can accommodate complex wiring with minimal overhead because the buried traces are patterned into the substrate 12, allowing the complexity of the reconfigurable solar cell array 22 to be achieved.

[0072] There are many configurations in which the solar cells 14 could be switched to change the length of the string. Figure 16 shows a group 58 of 15 solar cells 14 where the string length can be changed by a single solar cell 14. It may be advantageous to switch out a particular group 58 of solar cells 14.

[0073] One such combination is shown in Figure 18. Figure 18 shows a solar cell array 22 having 24 solar cells 14 arranged in 4 columns and 6 rows. The solar cells 14 are labeled 1 through 24 and are connected in series by lines 60 along the sides (and tops) of the solar cells 14.

[0074] There are also traces 62 that run to the left and right sides of the flex circuit board 12. These traces 62 are buried under and electrically isolated from the solar cells 14 and are intended as string termination outputs. The traces 62 are accessible at the corner regions 26 between the solar cells 14, allowing any solar cell 14 to easily access the output lines 56.

[0075] Two of the buried traces 62 are labeled as A and B. These traces 62 may be accessed by the solar cells 14 labeled as 3, 4, 5, 6, 11, 12, 13, 14, 19, 20, 21, and 22. This is a typical configuration described for a solar cell array 22 consisting of solar cells 14 connected to corner regions 26. This is beneficial for a solar cell array 22 that is reconfigurable.

[0076] FIG. 19 shows how this can be used in a reconfigurable solar cell array 22. Here, the 24 solar cells 14 are shown smaller, providing more space to draw the wiring and switching connections. The geometry shown is well suited for the use of electrical connections in the corner regions 26. Between the solar cells 14 labeled as 11-12, 13-14, 19-20, 21-22, and the solar cell 14 labeled as 24, there are switches 54 similar to those in FIG. 16. These switches 54 could be implemented in the corner regions 26 as in FIG. 15, located between the solar cells 14 in the same column position. As shown in FIG. 16, there are two string outputs, V1 for the first string and V2 for the second string. V2- and V1+ are accessed by each switch 54. To enable this switching, only a single trace 62 for V1+ and V2- is needed running under the solar cells 14.

[0077] Traces 64 are deposited on the surface of substrate 12, with V1+ and V2- traces 62 buried to pass under surface traces 64. Composite vertical lines 66 indicate interconnects connecting switches 54 to buried traces 62, with switches 54 set so that the first string is thirteen solar cells 14 long and the second string is eleven solar cells 14 long.

[0078] The V1 string can have a length of 11, 13, 19, 21, or 24 solar cells 14. This is accomplished by the buried traces 62 that run between the solar cells 14 in stages 3 and 4. These connections to the output lines could be moved up a stage to be between the solar cells in stages 2 and 3. This would result in string lengths of 10, 14, 18, 22, or 24. These different combinations would result from a four stage solar cell array 22, with the output lines running between two stages. Additional output lines could be added between the other stages to allow more switching points and more control of the string length. However, this complexity would require crossing the buried traces 62 and additional effort.

[0079] This layout is easy to manufacture because there are no traces crossing each other on the same layer, i.e., no crossing solid traces or crossing dashed traces. If these traces crossed, another metal layer and vias would be required, raising concerns about lifetime in space environments. This configuration of corner-connected solar cell arrays 22 with buried traces 62 in substrate 12 allows for a very simple connection path.

[0080] 16 and 17 were based on a group 58 of solar cells 14 split into a first string of full voltage and a second string of partial voltage. The second strings of the group 58 are then connected together to build the required voltage.

[0081] A related approach is shown in Figures 20A and 20B. Figure 20A includes multiple groups 58 of solar cells 14, each having the same configuration as that shown in Figures 16 and 17. Each group 58 includes first and second strings 68a, 68b, where the first string 68a is a full voltage string and the second string 68b is a partial voltage string, and the second string 68b of multiple partial voltages across the multiple groups 58 are connected together to provide the required string length and output voltage.

[0082] 20B shows that each group 58 is split into two strings 68a, 68b of different lengths, and the first and second strings 68a, 68b from each group 58 are connected together to provide the required string length. Specifically, the first string 68a of the first group 58 is a full voltage string, the second string 68b of the first group 58 is a partial voltage string that combines with the first string 68a of the second group 58 to generate a full voltage string, the second string 68b of the second group 58 is a partial voltage string that combines with the first string 68a of the third group 58 to form a full voltage string, and the second string 68b of the third group 58 is a full voltage string.

[0083] Although the example shown has only two strings 68a, 68b, these groups 58 could include a greater or lesser number of strings. Specifically, a group 58 could be made up of 1, 2, 3, 4, etc. full voltage strings, and 0, 1, or possibly multiple partial voltage strings.

[0084] 16-20 focused on reconfiguration by changing the string length with a small number of solar cells 14 to control the output voltage. This is beneficial because the voltage of individual solar cells 14 will change during the mission due to exposure to space radiation and changes in operating temperature.

[0085] Figures 21 and 22 apply reconfigurability to larger changes in string length, which would be for applications where large changes in output voltage are desired.

[0086] For example, during satellite operation, the solar cell array 22 is typically charging a set of batteries and the load voltage may be 100 V or less. However, during a mission phase, the satellite uses electric propulsion to change its orbital position and the load voltage may be 160 V, 200 V, 300 V, or other. It may be desirable for the solar cell array 22 to output desired voltages for different operations.

[0087] Another configuration is due to an interplanetary mission, where the solar cell array 22 may get very hot or very cold as the distance to the Sun changes. Alternatively, the temperature of the solar cell array 22 could change dramatically if the vehicle environment changes, such as if landing on an asteroid or other object or planet. These temperature changes change the voltage generated by the solar cells 14 and the required length of the string, which can be dramatic.

[0088] FIG. 21 shows the solar cell 14 layout of three flex sheet substrates 12, 12b, 12c. Each substrate 12a, 12b, 12c has a 3 (horizontal) by 27 (vertical) grid of solar cells 14. The bottom portion 12d of each substrate 12a, 12b, 12c has 58 solar cells 14 generating 100V. The top portion 12e of each substrate 12a, 12b, 12c has 19, 19, and 20 solar cells 14, respectively, for a total of 58 solar cells 14. There are some solar cell 14 positions that do not include a solar cell 14, as illustrated by the rectangular elements 70 filled with diagonal lines. The squiggly lines 72 generally show how the solar cells 14 in each portion 12d, 12e of each substrate 12a, 12b, 12c are connected in series in a string. There are eight pairs of SPST switches 54, shown as triangles, and the switches 54 can be reconfigured so that each of the lower portions 12d is a single string and the upper portions 12e of each board 12a, 12b, 12c are series connected together in a single string. In this configuration, all solar cells 14 are in series connected strings with 58 solar cells 14. This is a configuration that will produce 100V for a typical geosynchronous (GEO) near-earth environment after 10 years of radiation causing voltage loss.

[0089] Figure 22 shows how the layout of Figure 21 can be reconfigured using switches 54. When connected in series, the lower and upper portions 12d and 12e of each board 12a, 12b, 12c contain strings that are 77 (58+19), 77 (58+19) and 78 (58+20) solar cells 14 long, respectively. The strings will generate 132V, 132V and 134V, respectively, under GEO conditions. Alternatively, in high temperature environments, a 100V output can be maintained.

[0090] In conclusion, this description includes adding switches 54 and wiring to the solar cell array 22 to achieve reconfigurability. The application of switches and wiring to a conventional solar cell array would be extremely complicated and expensive. What currently enables a reconfigurable solar cell array 22 is the use of wiring traces in the substrate 12 instead of conventional wires. Reconfigurability requires wiring many or all solar cells 14 in parallel, whereas conventional wiring only has a start and end connection. The traces in the substrate 12 can have many connections made to them at any point down the length of the trace. Thus, the traces can be routed under the solar cells 14, providing circuit output lines for all the solar cells 14 very easily. Furthermore, the front contacts 32 and back contacts 34 of the solar cells 14 are available in the corner regions 26. To achieve reconfigurability without consuming area of ​​the panel 10a, the switches 54 can be added. The diagram and description show how reconfigurability changes the number of solar cells 14 in a string and the resulting output voltage at the solar cell 14 level. Alternatively, reconfigurability can be achieved by connecting strings together to build voltages into larger blocks.

[0091] In a conventional solar cell array, adding a switch would require end tabs, wires, switches, and circuit wiring. These components would have to be between any two solar cells that could be reconfigured. In addition to the labor, these components would take up significant panel area, thereby reducing power production.

[0092] manufacturing An embodiment of the present disclosure is described in the context of a method 74 for manufacturing a solar cell 14, a solar cell panel 10a, and / or a satellite, including steps 76-88 shown in FIG. 23, and the resulting satellite 90 having a solar cell panel 10a made of solar cells 14 is shown in FIG. 24.

[0093] 23, during the pre-production phase, an exemplary method 74 may include specification and design 76 of the solar cell 14, solar cell panel 10a, and / or satellite 90, and sourcing 78 of materials therefor. During the production phase, component and subassembly manufacturing 80 of the solar cell 14, solar cell panel 10a, and / or satellite 90, and system integration 82, may occur, which includes manufacturing the solar cell 14, solar cell panel 10a, and / or satellite 90. The solar cell 14, solar cell panel 10a, and / or satellite 90 may then undergo certification and delivery 84 for placement in service 86. The solar cell 14, solar cell panel 10a, and / or satellite 90 may also be scheduled for maintenance and upkeep 88 (including modification, reconfiguration, refurbishment, etc.) prior to launch.

[0094] Each step of method 74 may be performed or carried out by a system integrator, a third party, and / or an operator (e.g., a customer). For purposes of this specification, a system integrator may include, but is not limited to, any number of manufacturers and subcontractors of primary systems of solar cells, solar cell panels, satellites, or spacecraft, a third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers, and an operator may be a satellite communications company, a military organization, a service organization, etc.

[0095] 24, a satellite 90 produced by the exemplary method 74 may include a system 92, a body 94, a solar cell panel 10a made up of solar cells 14, and one or more antennas 96. Examples of systems 92 included in the satellite 90 include, but are not limited to, one or more of a propulsion system 98, an electrical system 100, a communication system 102, and a power system 104. Any number of other systems 92 may also be included.

[0096] 25 is an illustration of a solar cell panel 10a in the form of a functional block diagram, according to one embodiment. The solar cell panel 10a comprises a solar cell array 22, which comprises one or more solar cells 14 individually mounted on a substrate 12. Each solar cell 14 absorbs light 106 from a light source 108 and produces an electrical output 110 in response.

[0097] At least one of the solar cells 14 has at least one trimmed 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 multiple solar cells 14 are attached to the substrate 12, the corner regions 26 of adjacent ones of the solar cells 14 are aligned such that the area 28 of the substrate 12 is exposed.

[0098] The area 28 of the substrate 12 that is left exposed includes one or more corner conductors 20 that are attached to, printed on, or embedded in the substrate 12, and one or more electrical connections between the solar cells 14 and the corner conductors 20 are made within a corner region 26 created by a trimmed corner portion 24 of at least one of the solar cells 14.

[0099] The corner region 26 created by the trimmed corner 24 includes at least one contact, such as a front contact 32 on the front side of the solar cell 14 and / or a back contact 34 on the back side of the solar cell 14, for making an electrical connection between the corner conductor 20 and the solar cell 14. The electrical connection includes an up / down and / or left / right series connection that determines the flow of power through the solar cell 14 and may include one or more bypass diodes 44.

[0100] The area 28 of the substrate 12 that remains exposed includes at least one switch 54 located in the corner area 26 defined by the trimmed corner 24 adjacent the solar cell 14 for altering the current flow path between the solar cell 14 and the electrical connection. The substrate 12 includes one or more traces connected to the switch 54 for making the electrical connection between the solar cells 14.

[0101] The switches 54 are responsive to control signals to reconfigure the string lengths for the electrical connections between the solar cells 14. The switches 54 also reconfigure the connections between the strings, allowing for series connections between the strings and reconfigurability of the outputs. The switches 54 may be single-pole, single-throw (SPST) or double-pole, single-throw (DPST) switches and may be provided singly, in pairs, or packaged as desired.

[0102] Experimental Results To demonstrate the reconfiguration of the string length of the array, a solar cell array was constructed using a flex circuit board based on the corner conductor design.

[0103] FIG. 26A is an image of a demonstration solar cell array consisting of 12 solar cells arranged in three rows with four solar cells in each row. Electrical connections are made in the corner areas to provide either series connection or string termination. Current flow or conductive paths were selected by welding metal foil jumpers in place. In place of metal jumpers, pairs of wires were added in some places that extend beyond the perimeter of the solar cell array.

[0104] FIG. 26B is an image showing a close-up of one of the corner regions showing the electrical connections between the front contact, back contact, bypass diode, and solar cell.

[0105] Figure 26C is a version of Figure 26B with an electrical connection between the top left solar cell and the bottom left solar cell shown by a dark line drawn on the conductive paths. One conductive path connects the back contact of the top left solar cell to the front contact of the bottom left solar cell, allowing current to flow downward. Another conductive path connects the back contact of the bottom left solar cell through a bypass diode.

[0106] The electrical connection between the top right solar cell and the bottom right solar cell is rotated 180 degrees compared to the electrical connection between the top left solar cell and the bottom left solar cell, so that current flows from the bottom right solar cell to the top right solar cell.

[0107] The jumpers are arranged for series connection, and by changing the position of the jumpers, the current flow can be terminated within the buried traces.

[0108] Figure 26D is an image of another corner area where wires have been added instead of jumpers. The wires could be shorted together to act like a jumper, or separated to act as if there was no jumper.

[0109] In this demonstration, the configuration of a solar cell array with 12 solar cells can be changed from two strings of six solar cells to three strings of four solar cells using jumpers or wires.

[0110] 26E is a graph of photocurrent-voltage (LIV) measurements of a solar cell array under AM0 (air mass coefficient for zero atmosphere) illumination, with measurements taken in a configuration of two strings of six solar cells and three strings of four solar cells. The change in voltage confirms the change in string length.

[0111] Additionally, the disclosure includes embodiments according to the following provisions: Clause 1. A solar cell array including one or more solar cells mounted on a substrate, the substrate including one or more electrical connections to the solar cells, the substrate including one or more switches for changing a string length of one or more of the solar cells by changing a current flow path between one or more of the solar cells and one or more of the electrical connections. Clause 2. The solar cell array of clause 1, wherein when at least one of the solar cells having one or more trimmed corners is attached to the substrate, an area of ​​the substrate remains exposed, and the area of ​​the substrate that remains exposed includes at least one of the switches. Clause 3. The solar cell array of clause 2, wherein at least one of the solar cells is attached to the substrate such that corner regions defined by trimmed corners of at least one adjacent one of the solar cells are aligned, thereby exposing an area of ​​the substrate. Clause 4. A solar cell array as described in any one of clauses 1 to 3, wherein at least one of the switches is located within a corner region defined by a trimmed corner adjacent to at least one of the solar cells. Clause 5. A solar cell array as described in any one of clauses 1 to 4, wherein the switch varies the string length of one or more of the solar cells in response to one or more control signals. Clause 6. The solar cell array of any one of clauses 1 to 5, wherein a switch varies the string length to allow series connection between multiple strings and reconfigurability of the output. Clause 7. The solar cell array of any one of clauses 1 to 6, wherein a switch combines two or more strings of solar cells for a desired voltage output in response to one or more control signals. Clause 8. The solar cell array of any one of clauses 1 to 7, wherein the switch is a single-pole, single-throw (SPST) switch. Clause 9. The solar cell array of any one of clauses 1 to 8, wherein the switch is a double-pole single-throw (DPST) switch. Clause 10. A solar cell array as defined in any one of clauses 1 to 9, wherein the substrate includes one or more traces connected to switches for making electrical connections between the solar cells. Clause 11. A method for manufacturing a solar cell array comprising attaching one or more solar cells to a substrate, the substrate including one or more electrical connections to the solar cells, the substrate including one or more switches for changing a string length of one or more of the solar cells by changing a current flow path between one or more of the solar cells and one or more of the electrical connections. Clause 12. The method of clause 11, wherein when at least one of the solar cells having one or more trimmed corners is attached to the substrate, an area of ​​the substrate remains exposed, and the area of ​​the substrate that remains exposed includes at least one of the switches. Clause 13. The method of clause 12, wherein at least one of the solar cells is attached to the substrate such that corner regions defined by trimmed corners of at least one adjacent one of the solar cells are aligned, thereby exposing an area of ​​the substrate. Clause 14. The method of any one of clauses 11 to 13, wherein at least one of the switches is located within a corner region defined by a trimmed corner adjacent at least one of the solar cells. Clause 15. The method of any one of clauses 11 to 14, wherein the switch varies the string length of one or more of the solar cells in response to the one or more control signals. Clause 16. The method of any one of clauses 11 to 15, wherein the switch varies the string length to allow series connection between multiple strings and reconfigurability of the outputs. Clause 17. The method of any one of clauses 11 to 16, wherein a switch combines two or more strings of solar cells for a desired voltage output in response to one or more control signals. Clause 18. The method of any one of clauses 11 to 17, wherein the switch is a single-pole, single-throw (SPST) switch. Clause 19. The method of any one of clauses 11 to 18, wherein the switch is a double-pole single-throw (DPST) switch. Clause 20. The method of any one of clauses 11 to 19, wherein the substrate includes one or more traces connected to switches for making electrical connections between the solar cells. Clause 21. A method including actuating one or more switches in one or more electrical connections to one or more solar cells to change a string length of one or more of the solar cells by changing a current flow path between the one or more of the solar cells and one or more of the electrical connections.

[0112] conclusion The description of the above embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive or to be limited to the embodiments described. Many alternatives, modifications, and variations may be used in place of the specific elements described above.

Claims

1. A solar cell array, the solar cell array comprising: A solar cell (14) attached to a substrate (12) and having a front surface and a back surface; the substrate includes an electrical connection (20) to the solar cell; the substrate includes a switch (54) for changing a length of the string of solar cells by changing a current flow path between the solar cells and the electrical connections; When the solar cell (14) having trimmed corners (24) is attached to the substrate, an area (28) of the substrate (12) remains exposed; the switch connects one of the solar cells to either a string output line or a bypass diode (44) and one of the solar cells and an adjacent solar cell; at least one of the solar cells (14) is attached to the substrate (12) such that corner regions (26) defined by the trimmed corners (24) of adjacent solar cells (14) are aligned to expose the area (28) of the substrate; the bypass diode (44) is attached to the exposed area (28) of the substrate or the bypass diode (44) is attached to the backside of the solar cell (14) adjacent the trimmed corner.

2. The solar cell array of claim 1 , wherein the switch (54) varies the string length of the solar cells (14) in response to a control signal.

3. 3. The solar cell array of claim 1 or 2, wherein the switch varies the string length to allow series connection between multiple strings and output reconfigurability.

4. The solar cell array of any one of claims 1 to 3, wherein the switches (54) combine two or more strings of the solar cells (14) for a desired voltage output in response to a control signal.

5. The solar cell array of any one of claims 1 to 4, wherein the switch (54) is a single-pole, single-throw (SPST) switch.

6. The solar cell array of any one of claims 1 to 4, wherein the switch (54) is a double-pole single-throw (DPST) switch.

7. The solar cell array of any one of claims 1 to 6, wherein the substrate (12) includes traces connected to the switches to make the electrical connections between the solar cells (14).

8. A method of operating a solar cell array according to any one of claims 1 to 7, comprising the steps of: activating the switch (54) in the electrical connection (20) to the solar cell (14) to change the string length of the solar cell by changing the current flow path between the solar cell and the electrical connection. The method includes:

9. 1. A method for manufacturing a solar cell array, the method comprising: Attaching a solar cell having a front surface and a back surface to a substrate Including, the substrate includes an electrical connection to the solar cell; the substrate includes a switch for changing a string length of the solar cells by changing a current flow path between the solar cells and the electrical connections; an area of ​​the substrate is left exposed when the solar cell having trimmed corners is attached to the substrate; the switch connects one of the solar cells to either a string output line or a bypass diode and one of the solar cells and an adjacent solar cell; the solar cells are attached to the substrate such that corner regions defined by the trimmed corners of adjacent solar cells are aligned to expose the area of ​​the substrate; The method wherein the bypass diode is attached to the exposed area of ​​the substrate or the bypass diode is attached to the backside of the solar cell adjacent the trimmed corner.

10. The method of claim 9 , wherein the switch varies the string length of the solar cells in response to a control signal.

11. 11. The method of claim 9 or 10, wherein the switch varies the string length to allow series connection between multiple strings and output reconfigurability.

12. 12. The method of any one of claims 9 to 11, wherein the switches combine two or more strings of the solar cells for a desired voltage output in response to a control signal.

13. 13. The method of any one of claims 9 to 12, wherein the switch is a single-pole, single-throw (SPST) switch.

14. 13. The method of claim 9, wherein the switch is a double-pole single-throw (DPST) switch.

15. 15. The method of any one of claims 9 to 14, wherein the substrate includes traces connected to the switch for making the electrical connections between the solar cells.

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