Solar cell assembly
The solar cell assembly addresses power loss and cell damage from shading by sharing bypass diodes across series strings and integrating diodes within the module, enhancing power output and reducing costs.
Patent Information
- Application Number
- JP2025151428
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2013-07-05
- Filing Date
- 2025-09-11
- Publication Date
- 2025-12-03
AI Technical Summary
Solar cell modules experience complete power loss due to series connection when one cell is shaded, leading to potential destruction from reverse bias and hot spots, limited by the maximum number of bypass diodes per module.
A solar cell assembly design with shared bypass diodes across parallel series strings of solar cells, reducing the risk of reverse bias and hot spots by allowing current to bypass shaded cells, integrated bypass diodes within the module stack, and minimizing cross connectors.
Enhances power output and reduces manufacturing costs by minimizing resistive losses and module area, while preventing cell damage from shading, thus improving module efficiency and safety.
Smart Images
Figure 2025176136000001_ABST
Abstract
Description
[Technical Field]
[0001] FIELD OF THE INVENTION The present invention relates to solar cell assemblies and solar cell modules including such solar cell assemblies. [Background technology]
[0002] Solar cells are used to convert sunlight into electricity using the photovoltaic effect. As shown in Figure 1a, a solar cell module 100 based on crystalline silicon solar cells typically has dimensions of 15.6 x 15.6 cm that can be arranged in strings of six interconnected parallel solar cells. 2 Each string may contain 6 x 10 solar cells 104 of the same type. Each string may contain 10 or 12 monocrystalline or polycrystalline solar cells connected in series by copper ribbons 106. The strings may then be further connected in series by so-called cross connectors 105 so that all solar cells in the module are connected in series. Solar cell modules with identical configurations, for example 4 x 9, 6 x 8, or 6 x 12 solar cells, are also common.
[0003] Under normal operating conditions, all solar cells are exposed to light and can operate at their maximum power point of approximately 0.5V. Therefore, in a solar cell module with 6 x 10 solar cells, the total module voltage is approximately 30V. However, in certain situations, the module may be partially shaded. When a solar cell is shaded, the current it produces decreases proportionally to the illumination level. Due to the series connection, the solar cell with the lowest current determines the total current in the module. In situations where only one solar cell is shaded, this can result in a complete power loss of the entire module.
[0004] To avoid such complete power loss, so-called bypass diodes 101 may be incorporated into the module. The bypass diodes are connected in parallel with a certain number of solar cells. In the event of shading, only solar cells in parallel with the same bypass diode as the shaded solar cell may be affected by power loss. The number of bypass diodes per module is a compromise between the number of solar cells affected by partial shading and the cost of incorporating bypass diodes. Typically, two strings containing up to 20 solar cells are connected to one bypass diode. The bypass diodes may be located in a junction box 102, which serves as a fixture for the cables used to connect the module to adjacent modules. Figure 1b shows an electrical schematic of a typical module 100 with three bypass diodes 101 mounted in the junction box 102. The strings are connected to the junction box by cross connectors 103, and on the other side, the strings are connected in series with each other by cross connectors 105.
[0005] In a partial shading situation, when only one solar cell 104 is fully shaded, the bypass diode shorts out all of the solar cells connected in parallel with that diode. In this situation, the illuminated solar cells still operate at approximately 0.5-0.6 V, between their maximum power points and their open circuit voltages, while the shaded solar cells produce no voltage. Meanwhile, the combined voltage of the illuminated solar cells is 19 times that voltage, up to approximately 11.4 V, which is reverse biased to the shaded solar cells.
[0006] The diode characteristics of solar cells result in negligible reverse saturation current when a reverse bias voltage is applied. However, solar cells can only withstand a certain maximum reverse bias before avalanche breakdown of the diode occurs, which may cause rapid heat generation and ultimately lead to the destruction of the solar cell. Even before destruction, localized shunts or "hot spots" can lead to increased heat generation, which can damage the module's seal and even cause a fire.
[0007] Therefore, the maximum applied reverse bias voltage should not exceed the breakdown voltage, which is typically about 13 V. The exact breakdown voltage depends on the wafer material and the solar cell design. For a given open-circuit voltage of a solar cell, the breakdown voltage limits the number of solar cells that can be connected to one bypass diode.
[0008] The above figures show that the number of solar cells per bypass diode is already approaching the maximum within a typical module layout with cross connectors and junction boxes on the narrow side of the module.
[0009] An approach to increasing the module's output power is to reduce the length of the solar cells in the direction where they are interconnected by ribbons 106, which is typically achieved by cutting the solar cells in half. This effectively reduces the resistive losses, which have a parabolic dependence on cell length. This approach can improve power output by approximately 2%. However, it doubles the number of solar cells in each string, and also doubles the number of solar cells per bypass diode.
[0010] Another approach is to use solar cells cut in half and use one bypass diode per string, by incorporating a connector ribbon to connect one end of the string to the junction box on the other side. The drawbacks of this solution are that there is approximately a 0.5% power loss in the connector ribbon, and the substantial additional cost of the ribbon, as well as the need to provide multiple backsheet layers where the ribbon is placed to avoid shunting.
[0011] Therefore, it is desirable to have an optimal solar cell configuration in a solar cell module so as not to exceed the maximum reverse breakdown voltage and to avoid the use of excessively long connector ribbons. Summary of the Invention
[0012] A solar cell assembly is presented. The solar cell assembly includes one or more solar cell units connected in series. The solar cell unit includes a first series string of solar cells and a second series string of solar cells connected in parallel. Each of the first and second series strings of solar cells includes a plurality of solar cells connected in series. The solar cell assembly also includes a bypass diode connected to each solar cell unit, the bypass diode being connected in parallel to each of the first series string of solar cells and the second series string of solar cells. In other words, the bypass diode may be interpreted as being shared between the first and second series strings of solar cells in each solar cell unit.
[0013] Objectives, advantages, and features of the invention disclosed herein will become apparent with reference to the following description and accompanying drawings. Furthermore, it should be understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations. [Brief explanation of the drawings]
[0014] BRIEF DESCRIPTION OF THE DRAWINGS In the following drawings, the same reference numerals generally refer to the same or similar parts throughout the different views. Also, the drawings are merely schematic and not necessarily to scale, with the emphasis generally being placed upon illustrating the principles of the invention. In the following description, various embodiments are described with reference to the following drawings: [Figure 1a] 1 shows the layout of a solar cell module. [Figure 1b] 1 shows the layout of a solar cell module. [Figure 2a] 1 illustrates one embodiment of a solar cell assembly layout and corresponding electrical schematic. [Figure 2b] 1 illustrates one embodiment of a solar cell assembly layout and corresponding electrical schematic. [Figure 3a] 10 illustrates another embodiment of a solar cell assembly layout and corresponding electrical schematic. [Figure 3b] 10 illustrates another embodiment of a solar cell assembly layout and corresponding electrical schematic. [Figure 4a] 10 illustrates yet another embodiment of a solar cell assembly layout and corresponding electrical schematic. [Figure 4b] 10 illustrates yet another embodiment of a solar cell assembly layout and corresponding electrical schematic. [Figure 5] 1 illustrates an embodiment of a junction box. [Figure 6a] 1 illustrates one embodiment of a bypass diode. [Figure 6b] 1 illustrates one embodiment of a bypass diode. DETAILED DESCRIPTION OF THE INVENTION
[0015] Embodiments relate generally to devices, for example, devices for converting light energy into electrical energy. In particular, the device may be a solar cell element or a solar cell module including multiple solar cell elements.
[0016] FIG. 2a illustrates one embodiment of a solar cell assembly layout 200, and FIG. 2b illustrates a corresponding electrical schematic. In one embodiment, the solar cell assembly is a solar cell module. In another embodiment, the solar cell assembly is part of a solar cell module. The solar cell assembly may include solar cells 204, which may be arranged in one or more solar cell units. As shown in FIG. 2a, the solar cell assembly 200 includes three solar cell units, e.g., a first solar cell unit 211, a second solar cell unit 212, and a third solar cell unit 213. Solar cell assemblies including other numbers of solar cell units may also be useful.
[0017] In one embodiment, a solar cell unit includes a first series string of solar cells and a second series string of solar cells. For example, a first solar cell unit 211 may include a first series string of solar cells 221 and a second series string of solar cells 222. Within each series string of solar cells, multiple solar cells may be connected in series. For example, for a solar cell assembly in the form of a 6x10 solar cell module, the first series string of solar cells may have dimensions of 15.6x15.6 cm. 2 The solar cell series may also include other numbers of solar cells, for example, a 6x12 solar cell module having dimensions of 15.6x15.6 cm. 2 It would also be useful to include 12 solar cells of this type. In another embodiment, the solar cell unit includes solar cells cut into multiple sections. For example, as shown in FIG. 2a, the solar cells are cut in half and connected in series with each other within each solar cell series. By cutting the solar cells in half, the resistive losses, which depend parabolically on the length of the solar cell, can be effectively reduced. Power output can be improved by approximately 2%.
[0018] In one embodiment, the first and second series solar cells in the same solar cell unit share the same bypass diode. The bypass diode may include a semiconductor material, such as silicon, attached to two terminals. The bypass diode may be used to avoid the destructive effects of hot spot heating. In one embodiment, the bypass diode is connected in parallel with the solar cell or group of solar cells connected in series, but in reverse polarity. In normal operation, each solar cell in the group may be forward biased and the bypass diode may be reverse biased. However, when a portion of the group of solar cells is shaded, the bypass diode is forward biased, allowing current generated by the unshaded portion to flow through the bypass diode, thereby avoiding the high resistance of the shaded portion and preventing hot spot heating.
[0019] For example, the first and second series solar cells 221 and 222 in the first solar cell unit may share a first bypass diode 2011. In one embodiment, the first series solar cell is connected in parallel with a second series solar cell, which may have substantially the same open-circuit voltage Voc as the first series solar cell. More specifically, the first and second series solar cells may be mirror images of each other with respect to the first bypass diode. Other configurations of the first and second series solar cells in a solar cell unit that achieve the same Voc may also be useful. In one embodiment, the first bypass diode, the first series solar cell, and the second series solar cell are connected in parallel with each other. In one embodiment, the cathode of the first bypass diode may be connected to the positive node of both the first and second series solar cell, and the anode of the first bypass diode may be connected to the negative node of both the first and second series solar cell. The configurations of the first and second series solar cell and bypass diode in the other solar cell units may be similar to that in the first solar cell unit.
[0020] In one embodiment, the solar cell series is connected to the bypass diodes through a cross connector 203. The cross connector may be made of a conductive material such as a metal including, for example, copper, aluminum, silver, or alloys thereof. For example, the cross connector may be copper ribbon. Other types of conductive materials may also be used for the cross connector.
[0021] In one embodiment, the solar cells in the solar cell series are arranged in one or more strings connected in series. For example, a solar cell having dimensions of 15.6 x 15.6 cm 2 For a solar cell assembly having 6 x 10 solar cells of 15.6 x 7.8 cm, the first solar cell series in the first solar cell unit may include two strings, each string including five solar cells connected in series. Strings with other numbers of solar cells and other dimensions may also be useful. For example, as shown in Figure 2a, a solar cell assembly having dimensions of 15.6 x 7.8 cm may be used. 2 For a solar cell assembly having 6 x 20 solar cells cut in half, the first solar cell series in the first solar cell unit may include two strings, each string may include 10 solar cells cut in half connected in series. The two strings in the first solar cell series may be connected in series by a cross connector 205.
[0022] Other solar cell units in the solar cell assembly may have solar cell configurations similar to that of the first solar cell unit. In one embodiment, solar cell units are connected in series with each other if they generate substantially the same output current as each other. In one embodiment, the cross connectors 203 of some or all solar cell units in the assembly are combined into one central cross connector assembly, positioned substantially within the centerline of the solar cell assembly / module, as shown in FIG. 2a. Due to the symmetry of the solar cell assembly, this will not cause any difference in electrical device structure. Therefore, compared to a typical solar cell assembly / module layout, only a small amount of additional cross connectors are required, and the additional area required for cross connectors 203 and 205 is minimized. During manufacturing, it is important that the area of the module does not increase, thereby allowing the same equipment used to manufacture typical modules to be used. Furthermore, module efficiency, which is module power normalized to module area and nominal irradiance power, will not be sacrificed.
[0023] For example, if all solar cells in the first solar cell unit 211 are operating normally and supplying sufficient current to the load, the first bypass diode 2011 connected to the first solar cell unit 211 may be reverse-biased, and all solar cells in the first solar cell unit 211 will operate near their maximum power point (MPP). However, if a portion of the first solar cell unit is no longer able to generate sufficient current for the load—for example, if a portion of the first solar cell series is shaded or even damaged—the shaded or damaged portion may be reverse-biased, and the parallel-connected first bypass diode 2011 may be forward-biased to conduct current. The shaded or damaged first solar cell series may not be able to contribute to the power output of the assembly, while the unshaded or undamaged second solar cell series may still contribute to the power output of the assembly to a smaller extent. This embodiment may perform better than a typical solar cell module configuration in which all solar cells connected in parallel to the bypass diode do not contribute power when the bypass diode is forward-biased.
[0024] For example, for a solar cell assembly containing 6 x 20 halved solar cells, 10 halved solar cells are connected in series in a string, as shown in Figure 2a. The solar cell assembly is divided into three solar cell units, each with one bypass diode. This configuration allows for 40 solar cells per bypass diode without the maximum applied reverse bias voltage exceeding the breakdown voltage. This reduces the risk of solar cell "hot spots" or breakdown.
[0025] In one embodiment, the bypass diodes are housed in one or more junction boxes. Figure 5 shows one embodiment of a junction box 550. The junction box may include at least one bypass diode 501. The junction box may also include input terminals 503 for electrically connecting to each solar cell string and output terminals 505 for connecting to an external device, such as a power conditioner. In one embodiment, the junction box collects power from both solar cell series in some or all of the solar cell units and outputs the power to the external device.
[0026] In one embodiment, as shown in FIG. 2a, all of the bypass diodes in a solar cell assembly are mounted in a single junction box. In another embodiment, multiple junction boxes are used, each housing a subset of the bypass diodes connected to a solar cell unit. For example, the same number of junction boxes may be used as there are bypass diodes, with each junction box housing one bypass diode. As an example, three junction boxes may be used to house three bypass diodes, with each junction box housing one bypass diode. Other numbers of junction boxes may also be used. For example, two junction boxes may be used, with the first junction box housing two bypass diodes and the second junction box housing one bypass diode.
[0027] In one embodiment, the junction box is positioned on the backside of the solar cell assembly. The junction box may be positioned substantially within the centerline of the backside of the solar cell assembly. For example, for a solar cell assembly / module that includes a single junction box that houses all of the bypass diodes, the junction box may be positioned substantially in the center of the backside of the solar cell assembly / module. For a solar cell assembly / module that includes multiple junction boxes, the junction boxes may be positioned substantially within the centerline of the backside of the solar cell assembly, or may be positioned substantially equidistant from each other or from the edges of the assembly / module. Other junction box placements that minimize the amount of cross connectors may also be useful.
[0028] In yet another embodiment, a subset or all of the bypass diodes in a solar cell assembly include integrated bypass diodes integrated into the solar cell assembly / module stack instead of being housed in a junction box. In one embodiment, a combination of a junction box and integrated bypass diodes is used. For example, for a solar cell assembly including three bypass diodes, a combination of a junction box and integrated bypass diodes may be used. More specifically, the second bypass diode may be an integrated bypass diode integrated into the solar cell assembly / module stack, and the first and third bypass diodes may be housed in a junction box with cross connectors for connecting to external devices or other assemblies / modules. The second bypass diode may be located substantially in the center of the assembly / module, and the first and third bypass diodes may be located near the edges of the assembly / module.
[0029] 6a-6b show one embodiment of an integrated bypass diode unit 650 integrated within a laminate. In one embodiment, the integrated bypass diode unit includes an integrated bypass diode 601 and two cross connectors 605 for connecting to adjacent bypass diodes or external terminals. The cross connectors may include corrugation structures 655 as stress relief to prevent cracking due to electrical or mechanical overstress in the integrated bypass diode and the mechanical connection between the integrated bypass diode and the cross connector. Other stress relief structures may also be incorporated within the integrated bypass diode unit.
[0030] As shown in Figures 3a-3b, all of the bypass diodes in a solar cell assembly can be integrated bypass diodes. Figure 3a shows another embodiment of a solar cell assembly layout 300, and Figure 3b shows the corresponding electrical schematic. The features of this embodiment are similar to those described in Figures 2a-2b and will not be described in detail. In this embodiment, all of the bypass diodes 301 connected to the solar cell unit include integrated bypass diodes integrated within the stack of the solar cell assembly / module. In such a case, two integrated bypass diodes near the ends of the module can be connected to two external terminals 302, respectively, for connection to external devices or other assemblies / modules. The two external terminals can be located in two terminal boxes.
[0031] This approach can have the advantage of reducing the length of the cross connectors, thereby reducing electrical losses within them and thereby increasing the power output of the module. In addition to higher power output, the module area is also reduced, further increasing module efficiency. This approach effectively reduces module manufacturing costs by requiring fewer cross connectors, cheaper connector terminals, and less potting material. The connector terminals and cables can be located near the module edges, facilitating module connection within the photovoltaic array. Compared to the solution of incorporating a junction box, as shown in Figure 2a, the cables can be shorter. This reduces resistive losses and costs within the cables and allows for easier handling during module installation. Instead of cable connectors, connector plugs can be integrated into the side of the module frame to further reduce resistive losses.
[0032] FIG. 4a shows one embodiment of a solar cell module 400, and FIG. 4b shows a corresponding electrical schematic. Features in this embodiment are similar to those described in FIGS. 3a-3b and will not be described in detail. In one embodiment, the solar cell module includes a first solar cell assembly 431 and a second solar cell assembly 432. The first solar cell assembly 431 has dimensions of 15.6 x 3.9 cm. 2 The solar cell has dimensions of 15.6 x 15.6 cm 2 The first solar cell assembly may be obtained by cutting a solar cell of 15.6×3.9 cm into quarters. The first solar cell assembly may include one or more solar cell units 412 having a first solar cell series 421 and a second solar cell series 422. Within a solar cell series, multiple solar cells may be connected in series. For example, 2 For a solar cell assembly having 6 x 20 solar cells of 15.6 x 3.9 cm, the first solar cell series may include 20 such solar cells. The first solar cell series may also include other numbers of solar cells, for example, a solar cell assembly having dimensions of 15.6 x 3.9 cm. 2 For a solar cell assembly with 6 x 24 solar cells, the dimensions are 15.6 x 3.9 cm 2 The solar cell unit may include 24 solar cells of the same type. The configuration of the solar cell unit may be similar to that described in FIGS. 2a-2b and 3a-3b. For example, first and second series solar cell strings having substantially the same Voc may be connected in parallel and may share a first bypass diode 401. More specifically, the first and second series solar cell strings may be mirror images of each other with respect to the first bypass diode 401. In one embodiment, the solar cell strings are connected to the first bypass diode via cross connectors 403. The cross connectors 403 of some or all of the solar cell units in the first solar cell assembly may be combined into a central cross connector assembly and may be positioned substantially within the centerline of the first solar cell assembly. In one embodiment, connector terminals 406 are used to connect to the cross connectors or central cross connector assembly.
[0033] The configuration of bypass diodes and cross connectors included in the solar cell assembly of Figures 4a-4b may be similar to those shown in Figures 2a-2b and 3a-3b.
[0034] In one embodiment, as shown in Figures 4a-4b, two solar cell assemblies are included in a solar cell module. Other numbers of solar cell assemblies may also be included in a solar cell module depending on the requirements and configuration of the solar cells and module. The solar cell assemblies in a solar cell module may be connected to each other by a single connector, which connects a first end of the solar cell assembly to a second connector, which connects a second end of the solar cell assembly. This design may be more resistant to shading than typical solar cell module designs.
[0035] The present invention may be embodied in other specific forms without departing from the scope of the present invention. The foregoing embodiments, therefore, are to be considered in all respects as illustrative and not limiting of the invention described herein. The scope of the present invention is, therefore, indicated by the appended claims rather than the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.
[0036] Terms such as "about" used in conjunction with a particular distance or size should be interpreted as not excluding minor deviations from the particular distance or size, and may include, for example, deviations of up to 20%. Further, terms such as "substantially parallel" or "substantially perpendicular" should be interpreted as not excluding minor deviations from the particular orientation, and may include, for example, deviations of up to 20°.
[0037] Finally, it should be noted that the term "comprising" does not exclude other elements or steps, and that the singular does not exclude a plurality. Also, elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.
Claims
1. a first solar cell unit; a second solar cell unit connected in series to the first solar cell unit; a third solar cell unit connected in series to the first solar cell unit and the second solar cell unit; 1. A solar cell assembly having: The first solar cell unit is a first solar cell series body including a plurality of solar cells connected in series; a second solar cell series body including a plurality of solar cells connected in series and connected in parallel to the first solar cell series body; a first bypass diode connected in parallel to the first solar cell series body and the second solar cell series body; a first connection box that houses the first bypass diode; The second solar cell unit is a third solar cell series body including a plurality of solar cells connected in series; a fourth solar cell series body including a plurality of solar cells connected in series and connected in parallel to the third solar cell series body; a second bypass diode connected in parallel to the third solar cell series body and the fourth solar cell series body; a second connection box that houses the second bypass diode; The third solar cell unit is a fifth solar cell series body including a plurality of solar cells connected in series; a sixth solar cell series body including a plurality of solar cells connected in series and connected in parallel to the fifth solar cell series body; a third bypass diode connected in parallel to the fifth solar cell series body and the sixth solar cell series body; a third connection box that houses the third bypass diode; the first junction box, the second junction box, and the third junction box are disposed on a centerline of the solar cell assembly; and A solar cell assembly, characterized in that the third junction box is positioned in the center of the solar cell assembly, and the first and second junction boxes are positioned closer to the ends of the solar cell assembly than the third junction box.
2. 2. The solar cell assembly of claim 1, wherein the first series string of solar cells has the same open circuit voltage Voc as the second series string of solar cells in the first solar cell unit.
3. 3. The solar cell assembly according to claim 1, wherein the first series string of solar cells and the second series string of solar cells are mirror images of each other with respect to the first bypass diode of the first solar cell unit, and the third series string of solar cells and the fourth series string of solar cells are mirror images of each other with respect to the second bypass diode of the second solar cell unit.
4. 4. The solar cell assembly according to claim 1, wherein the first series array of solar cells and the second series array of solar cells each include the same number of solar cells.
5. 5. The solar cell assembly according to claim 1, wherein the first series string of solar cells and the second series string of solar cells are connected in parallel to the first bypass diode via a first cross connector, the third series string of solar cells and the fourth series string of solar cells are connected in parallel to the second bypass diode via a second cross connector, and the fifth series string of solar cells and the sixth series string of solar cells are connected in parallel to the third bypass diode via a third cross connector.
6. 6. The solar cell assembly of claim 5, wherein the first, second, and third cross connectors are positioned as one central cross connector at a centerline of the solar cell assembly.
7. 7. The solar cell assembly of claim 5, wherein the third cross connector has a corrugated structure for stress relief to prevent cracks due to electrical or mechanical overstress in the third bypass diode and in the mechanical connection between the third bypass diode and the third cross connector.