Photovoltaic power generation system

Abstract

To provide a photovoltaic power generation system that uses a double-sided light-receiving solar cell module capable of increasing the amount of power generation on the entire photovoltaic power generation system.SOLUTION: A photovoltaic power generation system is configured from a plurality of solar cell modules 1 to 24 of double-sided light-receiving type. The photovoltaic power generation system is configured from two or more module groups formed by connecting in series a plurality of solar cell modules that are identical or similar in the amount of light incident on theirs back sides relative to the light incident on their front sides.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a photovoltaic power generation system in which a large number of bifacial solar cell modules are installed. [Background technology]

[0002] There are bifacial solar cell modules that can generate power by receiving light from the back side as well (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2005 / 074039 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the front side of the solar cell module in the solar power generation system is directly irradiated with sunlight, so that the amount of light incident on the solar cell module at any position is equal, but the back side is basically in the shade, and reflected light and scattered light are incident, so the amount of light incident on the back side coincides with the movement of the sun. Specifically, the amount of light incident is greater on the solar cell module arranged on the east side from morning to noon, the amount of light incident is greater on the solar cell module arranged on the west side from noon to evening, and the amount of light incident is greater on the solar cell module arranged on the south side during the day. In other words, the amount of light incident on the back side arranged in the direction of the sun at a given time is greater. Therefore, the amount of light incident differs depending on the position of the solar cell module, and the contribution of the back side to the output (power, power generation amount) generated by the solar cell module also differs depending on the position of the solar cell module. For this reason, when solar cell modules with different contributions on the back side are connected in series, the solar cell module with a smaller contribution lowers the performance of the module group, so there is an inconvenience that the output (power, power generation amount) of the entire solar power generation system cannot be increased.

[0005] In view of the above circumstances, an object of the present invention is to provide a photovoltaic power generation system using a bifacial solar cell module that can increase the amount of power generated by the entire photovoltaic power generation system. [Means for solving the problem]

[0006] The solar cell system of the present invention is a photovoltaic power generation system composed of multiple bifacial solar cell modules, and is composed of two or more module groups each consisting of multiple solar cell modules connected in series, each of which has the same or similar incident light on its back side relative to its front side.

[0007] According to this configuration, the output loss of the entire photovoltaic power generation system can be reduced compared to a case where a plurality of solar cell modules with significantly different incident light amounts are connected in series, and therefore the amount of power generated by the entire photovoltaic power generation system can be increased.

[0008] In the photovoltaic power generation system according to the present invention, among the plurality of solar cell modules, a plurality of solar cell modules located on the south side may be grouped into one module group.

[0009] As described above, by combining multiple solar cell modules located on the south side, where the amount of incident light is particularly high, into one module group, output loss can be kept small compared to when they are combined with solar cell modules facing in other directions, and the amount of power generated by the entire solar power generation system can be increased accordingly.

[0010] In the photovoltaic power generation system according to the present invention, of the plurality of solar cell modules, a plurality of solar cell modules located on the west side and a plurality of solar cell modules located on the east side may each be grouped into one module group.

[0011] According to the above configuration, the output loss generated in each of the module groups on the west side and the module groups on the east side can be kept small compared to when combined with solar cell modules in other directions, thereby increasing the amount of power generated by the entire solar power generation system. Effect of the Invention

[0012] According to the present invention, by connecting a plurality of solar cell modules having the same or similar incident amounts in series to form a solar power generation system using a bifacial solar cell module composed of at least two or more module groups, it is possible to provide a solar power generation system that can increase the overall power generation amount of a conventional solar power generation system even when a bifacial solar cell module is used. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a perspective view showing a state in which a solar cell module is installed on the upper surface of a roof. [Diagram 2] FIG. 2 is a vertical cross-sectional side view of the solar cell module. [Diagram 3] 1A and 1B are diagrams showing the solar cell module in an installed state, where FIG. 1A shows a connection method of a comparative example, and FIG. 1B shows a connection method of the present invention. [Figure 4] FIG. 1 is a block diagram of a method for constructing a solar cell system of the present invention. [Diagram 5] This figure shows what happens when the amount of incident light to one solar cell module decreases. (a) shows the same connection method as in Figure 3(b), and (b) shows the state in which the solar cell module with the decreased amount of incident light is reconnected to another group. [Figure 6] FIG. 1 is a schematic diagram showing a configuration in which solar cell modules are connected by switches. [Figure 7] FIG. 7 is a schematic diagram showing a state in which the connection of the solar cell module in FIG. 6 is changed by turning a switch on and off. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A solar power generation system according to an embodiment of the present invention will be described below with reference to the drawings.

[0015] As shown in Figures 3(a) and (b), the solar power generation system is composed of bifacial solar cell modules 1-24. Specifically, the solar power generation system is configured in a rectangular shape with six columns vertically and four rows horizontally, totaling 24 solar cell modules 1-24. It is preferable to install at least six solar cell modules vertically and horizontally, but the number of solar cell modules and the shape of the solar power generation system can be freely changed.

[0016] The solar cell modules 1 to 24 have the same structure. For example, the solar cell module 1 includes a light-receiving surface (front surface) side transparent protective member 25 and a back surface side transparent protective member 26 as shown in FIG. 2. A plurality of double-sided light-receiving solar cell cells 27 are arranged between the light-receiving surface side transparent protective member 25 and the back surface side transparent protective member 26, and are sealed with a sealing material 28. As the light-receiving surface side transparent protective member 25, a transparent base material such as a glass plate, an acrylic plate, a polycarbonate plate, etc. is used. As the back surface side transparent protective member 26, a glass plate, an acrylic plate, a polycarbonate plate, a transparent resin sheet, a transparent resin film, etc. are used. The sealing material 28 is composed of ethylene-vinyl acetate copolymer (EVA), polyolefin (PO), PVB (polyvinyl butyral), ionomer, etc. Adjacent solar cell cells in FIG. 2 are electrically connected by wiring material not shown, and are connected to a terminal box not shown.

[0017] The light transmitted through the light receiving surface (front surface) side transparent protective member 25 is received by the front surface side of the solar cell 27, but the amount of light incident on the front surface side of the solar cell 27 does not vary greatly depending on the installation position of the solar cell 27. On the other hand, the back surface side of the solar cell 27 receives reflected light and scattered light, but the reflected light and scattered light hit the back surface side depending on the position of the sun, so the amount of light incident on the back surface relative to the front surface varies greatly depending on the installation position of the solar cell 27. This is because, for example, when the solar cell modules 1 to 24 are installed in a tilted state on a roof, the light irradiated to the back surface side of the solar cell modules 1 to 24 is reflected light and scattered light reflected from the roof, so the amount of light incident varies greatly depending on the installation surface, and the amount of light incident on the back surface side of the solar cell modules 8 to 11, 14 to 17 located inside the solar cell modules 1 to 7, 12, 13, 18 to 24 located on the outer periphery is even smaller. 3(a) and (b) show the actually measured amount of light incident on the back surface of each solar cell module 1, expressed as the incidence rate (%) of the back surface to the front surface. Note that this incidence rate is calculated based on the amount of light on the front side and the amount of light on the back side measured during the time when sunlight is irradiating the module.

[0018] In Figures 3(a) and (b), the solar cell modules 1 to 6 in a horizontal row on the south side have higher incidence rates (%) than the other modules, with incidence rates (%) of 7% and 5%. The solar cell modules 6, 12, 18, and 24 on the east side and the solar cell modules 1, 7, 13, and 19 on the west side have the second highest incidence rates (%) of 7% and 4%. The solar cell modules 19 to 24 on the north side have the third highest incidence rates (%) of 4% and 3%. The eight solar cell modules 8 to 11, and 14 to 17 arranged on the inside of the outer periphery have the lowest incidence rates (%) of 2%.

[0019] However, when modules with different back surface contributions are connected in series, the solar cell module with a lower incidence rate (small contribution) lowers the performance of the module group, so the greater the difference in the amount of incidence, the greater the output loss of the entire solar power generation system, and the output of the entire solar power generation system cannot be increased. Therefore, in the present invention, solar cell modules with the same or similar incidence rates among multiple solar cell modules are connected in series to configure at least two or more module groups (four module groups from the first module group to the fourth module group in FIG. 3(b)), thereby suppressing the output loss of the entire solar cell system and increasing the output of the entire solar power generation system. The term "same or similar" means that the difference in incidence rate does not exceed 2%, in other words, the difference in incidence rate is 2% or less, and it is preferable to configure the module group so that the difference is within this range. When actually assembling the module group, it is preferable that the difference in incidence rate does not exceed 2%.

[0020] As shown in FIG. 3(b), the first module group (white area) is composed of six solar cell modules 1-6 arranged in a horizontal row in the left-right direction on the south side. The incidence rate (%) of the two solar cell modules 1 and 6 at both ends in the left-right direction is the highest at 7%, and the incidence rate (%) of the four solar cell modules 2-5 located between the two solar cell modules 1 and 6 at both ends is the second highest at 5%. Therefore, the solar cell modules 2-5 on the side with the lower incidence rate (small contribution) lower the performance of the module group, so that in this first module group, the output is equivalent to that of the six solar cell modules 1-6 with an incidence rate (%) of 5%.

[0021] The second module group (diagonal lined area on the left side) is composed of a total of four solar cell modules, excluding the solar cell module 1 located at one end in the left-right direction on the south side (left end in FIG. 3(b)), three solar cell modules 7, 13, 19 arranged vertically in a vertical row on the west side, and one solar cell module 20 adjacent to the solar cell module 19 located at one end in the left-right direction on the north side (left end in FIG. 3(b)). The incidence rate (%) of the three solar cell modules 7, 13, 19 is 4%, and the incidence rate (%) of the remaining solar cell module 20 is 3%. Therefore, the solar cell module 20 with a small amount of incidence (small contribution) lowers the performance of the module group, so that in this second module group, the output is equivalent to that of the four solar cell modules 7, 13, 19, 20 with an incidence rate (%) of 3%.

[0022] The third module group (diagonal lined area on the right side) is composed of three solar cell modules 12, 18, 24 arranged vertically in a vertical line on the east side, excluding the solar cell module 6 located at the other left-right end on the south side (the right end in FIG. 3(b)), and one solar cell module 23 adjacent to the solar cell module 24 located at the other left-right end on the north side (the right end in FIG. 3(b)). The incidence rate (%) of the three solar cell modules 12, 18, 24 is 4%, and the incidence rate (%) of the remaining solar cell module 23 is 3%. Therefore, the solar cell module 23 with a small amount of incidence (small contribution) lowers the performance of the module group, so that the output of this third module group is the same as that of the second module group, that is, four solar cell modules 12, 18, 23, 24 with an incidence rate (%) of 3%.

[0023] The fourth module group (part marked with dots) is composed of eight solar cell modules 8-11, 14-17 located inside two solar cell modules 21, 22 located in the center in the left-right direction on the north side and sixteen solar cell modules 1-7, 12, 13, 18-24 located on the outer periphery. The incidence rate (%) of the two solar cell modules 21, 22 is 3%, and the incidence rate (%) of the remaining eight solar cell modules 8-11, 14-17 is 2%. Therefore, the solar cell modules 8-11, 14-17, which have a small amount of incidence (small contribution), lower the performance of the module group, so in this fourth module group, the output is the equivalent of ten solar cell modules 8-11, 14-17, 21, 22, which have the lowest incidence rate (%) of 2%.

[0024] In contrast, a comparative example is shown in Fig. 3(a). In this comparative example, the connection is made without considering the amount of light incident on the back surface. Specifically, three module groups, a first module group to a third module group, are configured by connecting in series so as to obtain an output voltage that matches the input voltage of each of a plurality of input parts provided in the power conditioner.

[0025] The first module group (white area) consists of four rows of solar cell modules arranged in the left-right direction, with the first row consisting of six solar cell modules 1-6 located on the south side and the second row above them consisting of four solar cell modules 7-10 connected in series, for a total of 10 solar cell modules 1-10.

[0026] The second module group (shaded area) is composed of a total of 10 solar cell modules 11-20 connected in series: two solar cell modules 11, 12 on the east side of the second row, six solar cell modules 13-18 on the third row, and two solar cell modules 19, 20 on the west side of the fourth row.

[0027] The third module group (the portion marked with dots) is configured by connecting in series four solar cell modules 21 to 24 on the north side of the fourth row.

[0028] Looking at the first to third module groups in Fig. 3(a), the first module group has incidence rates of 7%, 5%, 4% and 2%. In this case, the module group includes a solar cell module with the highest incidence rate of 7%, but also includes a solar cell module with the lowest incidence rate of 2%. Therefore, solar cell modules 8, 9 and 10, which have a small amount of incidence (small contribution), lower the performance of the module group, so that the first module group has an output equivalent to that of 10 solar cell modules 1 to 10, which have the lowest incidence rate (%) of 2%.

[0029] In addition, the second module group has incidence rates of 4%, 3%, and 2%. In this case, the module group includes solar cell modules with a high incidence rate of 4%, but solar cell modules with the lowest incidence rate of 2%. Therefore, solar cell modules 11, 14-17, which have a small amount of incidence (small contribution), lower the performance of the module group, and the second module group has an output equivalent to that of 10 solar cell modules 11-20, which have the lowest incidence rate (%) of 2%.

[0030] In addition, the third module group has an incidence rate of 4% and 3%. In this case, the module group includes solar cell modules with a high incidence rate of 4%, but solar cell modules with a low incidence rate of 3%. Therefore, solar cell modules 21-23, which have a small amount of incidence (small contribution), lower the performance of the module group, and the third module group has an output equivalent to that of four solar cell modules 21-24, which have a low incidence rate (%) of 3%.

[0031] Therefore, Figure 3(b) of the present invention includes a first module group which has the output of six solar cell modules 1 to 6 with an incidence rate (%) of 5%, a second module group which has the output of four solar cell modules 7, 13, 19, and 20 with an incidence rate (%) of 3%, a third module group which has the output of four solar cell modules 12, 18, 23, and 24 with the same incidence rate (%) of 3% as the second module group, and a fourth module group which has the output of ten solar cell modules 8 to 11, 14 to 17, 21, and 22 with the lowest incidence rate (%) of 2%. In contrast, Figure 3(a) of the comparative example includes a first module group which has an output of 10 solar cell modules 1-10 with the lowest incidence rate (%) of 2%, a second module group which has an output of 10 solar cell modules 11-20 with the lowest incidence rate (%) of 2%, and a third module group which has an output of 4 solar cell modules 21-24 with a low incidence rate (%) of 3%, and it is clear that the connection (module grouping) of the present invention can increase the output (power, power generation) of the solar cell modules.

[0032] The present invention also provides a method for constructing a solar cell system, which includes five steps, namely, an installation step 29, a connection step 30, an indexing step 31, a determination step 32, and a reconnection step 33, as shown in Fig. 4. This method for constructing a solar cell system is performed by a system constituted by a computer.

[0033] The installation step 29 is a step of installing a large number of bifacial solar cell modules (24 in this embodiment). The connection step 30 is a step of serially connecting a plurality of solar cell modules (determined by the allowable voltage of each input section of the power conditioner) having similar incidence rates (or the same incidence rates) among a large number of solar cell modules having different incidence rates of light on the back side relative to the front side depending on the installation surface of the solar cell module. In this embodiment, a total of four module groups are formed by connecting in the connection step 30, but any number of module groups may be formed, such as two, three, or five or more. The connection of the solar cell modules is not limited to that shown in FIG. 3(b). In addition, the incidence rates being similar are preferably such that the difference between the incidence rates is 2% or less, but may be 3% or less. In addition, a detection step (not shown) is provided for detecting the output value of the solar power generation system at the time when the plurality of solar cell modules are connected in the connection step 30 to form one module group.

[0034] The identification process 31 is a process in which the output value of the solar cell system (total output value of the 24 solar cell modules) is detected in the detection process, and when the detected output value is equal to or less than a preset output value, the shape of the current-voltage (IV) curve for each solar cell module is measured and confirmed to identify a solar cell module having a current variation in comparison with other solar cell modules in the configured module group. A solar cell module having a current variation is a solar cell module that is an obstacle to increasing the power generation amount of the entire solar power generation system.

[0035] The determination step 32 is a step of determining whether or not the output value of the solar cell system will be improved by switching the solar cell module having the current variation identified in the identification step 31 from the module group to which the solar cell module is connected to another module group. The reconnection step 33 is a step of actually performing the reconnection when it is determined in the determination step 32 that the output value of the solar cell system will be improved by switching the connections. Then, by actually performing the reconnection in the reconnection step 33, it becomes possible to improve the output of each module group.

[0036] The occurrence of solar cell modules with the current variation may occur when the incidence rate is confirmed in advance by an experiment and the module grouping of the solar cell modules is determined, but the incidence rate differs depending on the location where the solar cell modules are installed (for example, differences in the amount of light reflection). For example, the incidence rate of the third solar cell module from the left among the six solar cell modules 1 to 6 on the south side shown in FIG. 5(a) has dropped from 5% (see FIGS. 3(a) and (b)) to 3%. In this case, in this first module group (white portion), the output of the six solar cell modules 1 to 6 with an incidence rate (%) of 3% is obtained, and there is clearly a drop in the output of the solar cell modules 1 to 6 in the first module group.

[0037] Therefore, when a solar cell module having a current variation is identified in the identification step 31, if the computer determines in the determination step 32 that the output value of the solar cell system will be improved by switching the solar cell module having a current variation from the module group to which the solar cell module is connected to another module group, the computer actually performs the switching in the reconnection step 33. Since the incidence rate has dropped from 5% to 3%, it is determined to perform the switching as shown in FIG. 5(b). In other words, the switching is performed so that the difference in incidence rate is 2% or less. The first module group (white portion) shown in FIG. 5(b) is five solar cell modules 1, 2, 4, 5, and 6, and the fourth module group (dotted portion) is the fourth module group (dotted portion) shown in FIG. 3(b) plus the solar cell module 3 whose incidence rate has dropped to 3%. 5(b) has an output of 5% of the five solar cell modules 1, 2, 4, 5, and 6, and the fourth module group has an output of 2% of the eleven solar cell modules 3, 8-11, 14-17, 21, and 22, suppressing a decrease in the output of the solar power generation system and increasing the amount of power generation (output) of the entire solar power generation system. The above judgment may be made by a control unit (not shown) provided in a computer, or may be made by a human.

[0038] In FIG. 1, a solar cell module 1 is installed in an inclined state on a stand consisting of an H-shaped steel 35 that is long on the top surface of a roof 34 in the direction in which the solar cell modules are arranged side by side (the direction penetrating the drawing), and a U-shaped channel member 36 that is provided on the top surface of the H-shaped steel 35 in a direction perpendicular to the length direction of the H-shaped steel 35 and has one open side in the left-right direction. A male connector 37A is attached to the tip of a cable 38 of this solar cell module 1, and a female connector 37B is attached to the tip of a cable 39 of another module (not shown). By attaching and detaching the male connector 37A and the female connector 37B, the solar cell modules can be connected and disconnected from each other. Since the connector consisting of the male connector 37A and the female connector 37B is arranged in the channel member 36 that is easy to see from the side, the connector can be found immediately, and the above-mentioned reconnection work can be performed quickly. In addition, a base material (not shown) for increasing the reflectance of light may be provided on the installation surface (the top surface of the roof 34 in FIG. 1) that faces the back surface of the solar cell module. By providing such a base material, the difference in the incidence rate between the solar cell modules on the back surface of the solar cell module can be reduced, which is preferable. Note that the solar cell modules are connected to each other by connecting the positive and negative sides, but in Figure 1, only one side is shown and the other side is omitted.

[0039] Incidentally, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the spirit and scope of the present invention.

[0040] In the above embodiment, the solar cell modules are switched by a connector, but may be switched by turning a switch ON and OFF. Specifically, as shown in FIG. 6, three solar cell modules each of the nine first to ninth solar cell modules 1 to 9, that is, the first to third solar cell modules 1 to 3, the fourth to sixth solar cell modules 4 to 6, and the seventh to ninth solar cell modules 7 to 9 are connected in series to three module groups (the first module group, the second module group, and the third module group from the left side of the drawing), and the positive and negative poles of each module group are connected to the positive and negative terminals of three input systems (the first system to the third system) provided in the power conditioner. In FIG. 6, it is assumed that the solar cell module having current variation in the above-mentioned indexing process 31 is determined to be the first solar cell module 1 at the left end of the first module group, the incidence rate of the first solar cell module 1 is determined to be 2%, and the incidence rates of the other two second and third solar cell modules 2 and 3 of the first module group are determined to be 5%. In this case, the difference in incidence rate is 3%. In contrast, in the second module group, the incidence rates of all of the fourth to sixth solar cell modules 4, 5, and 6 are assumed to be the same 2%, and in the third module group, the incidence rates of all of the seventh to ninth solar cell modules 7, 8, and 9 are assumed to be the same 4%. In this case, in order to increase the output of the solar cell modules 1 to 9, the solar cell module 1 on the left end of the first module group is disconnected from the first module group and reconnected to the second module group.For this purpose, there are provided a first switch S1 that can turn on and off the wiring from the positive pole to the first solar cell module 1, a second switch S2 that switches between a connected state in which the first solar cell module 1 and the second solar cell module 2 are connected and a non-connected state, a third switch S3 that connects the open positive pole to the second solar cell module 2 by disconnecting the first solar cell module 1 from the positive pole, a fourth switch S4 that connects the positive pole of the second module group to the first solar cell module 1, a fifth switch S5 that connects the fourth solar cell module 4 of the second module group in series to the first solar cell module 1, and a sixth switch S6 that can turn on and off the wiring from the positive pole of the second module group to the fourth solar cell module 4. At this time, the three switches S1, S2, and S6 are turned on, and the remaining switches S3, S4, and S5 are turned off. Then, as described above, in the indexing step 31, the solar cell module having the current variation, the first solar cell module 1 in FIG. 6, is identified, and in the determination step 32, it is determined that the output value of the solar cell system will be improved by switching the first solar cell module 1 having the current variation from the first module group to which the first solar cell module is connected to the second module group. Then, in the reconnection step 33, the reconnection is actually performed. When switching the connection, as shown in FIG. 7, the switches S1, S2, and S6 are turned OFF and the switches S3, S4, and S5 are turned ON, thereby disconnecting the first solar cell module 1 from the first module group and connecting it in series to the second module group. These switches S1 to S6 may be switched manually or automatically.

[0041] In addition, in the above embodiment, the solar cell modules are arranged with south facing due south, but the orientation of the solar cell modules may be changed within a range of ±45 degrees from due south. [Explanation of symbols]

[0042] 1 to 24... solar cell module, 25... light receiving surface (front) side transparent protective member, 26... back side transparent protective member, 27... solar cell, 28... sealing material, 29... installation process, 30... connection process, 31... indexing process, 32... evaluation process, 33... reconnection process, 34... roof, 35... H-shaped steel, 36... channel member, 37A... male connector, 37B... female connector, 38, 39... cable

Claims

[Claim 1] A photovoltaic power generation system comprising a plurality of bifacial solar cell modules, the system being configured to calculate a light incidence rate of the back surface of each solar cell module relative to the front surface based on the amount of light incident on the front surface and the amount of light incident on the back surface of each solar cell module, and comprising two or more module groups each including a plurality of solar cell modules having the same or similar calculated incidence rates connected in series; In the photovoltaic power generation system, among the plurality of solar cell modules, the plurality of solar cell modules located on the west side and the plurality of solar cell modules located on the east side are each formed into one module group.

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