Laminated-type photovoltaic block

Abstract

The purpose of the present invention is to provide laminated-type photovoltaic block technology having laminated photovoltaic layers and a high photovoltaic efficiency. To achieve the purpose above, one of the representative laminated-type photovoltaic blocks according to the present invention is a block body obtained by laminating plate-shaped photovoltaic cells, and a height dimension of the block body is greater than or equal to either of the depth dimension or the width dimension.　A transparent conductive film serving as an upper electrode and a lower electrode of the photovoltaic cell is formed on both surfaces of a transparent substrate constituting the photovoltaic cells.

Description

Stacked photovoltaic blocks

[0001] The present invention relates to a stacked photovoltaic block.

[0002] As the movement towards a sustainable society rapidly gains momentum, energy conservation and CO2 reduction are also being considered for structures such as homes and buildings. ２ In response to this trend, technological development is underway to install solar cells on the roofs and windows of buildings to generate photovoltaic power.

[0003] For example, Patent Document 1 discloses "a solar cell module including, in this order, a glass plate located on the light-receiving surface side, a solar cell cell, and a glass plate located on the back surface side, wherein a low-emissivity film is formed on the surface of at least one of the light-receiving surface side and the back surface side."

[0004] Furthermore, Patent Document 2 discloses a solar cell window panel that can change the solar heat gain coefficient without mechanical manipulation. It discloses the following configuration: "The solar cell window glass 10 is placed in an opening of a building. The solar cell window glass 10 comprises a light-transmitting glass panel 12 and a plurality of solar cell modules 14 arranged alternately in the height direction on an interior side surface 12a and an exterior side surface 12b of the glass panel 12."

[0005] JP 2021-15939 A JP 2021-11809 A

[0006] However, both Patent Documents 1 and 2 assume that the light-receiving surface of the solar cell is arranged at an angle as close to perpendicular as possible to the angle of incidence of light. Patent Document 2 also discloses a structure in which solar cells are stacked in N layers, but the solar cell-equipped window glass in Patent Document 2 has an aperture ratio of 0% at the meridian altitude on the summer solstice and 40% or more at the meridian altitude on the winter solstice. Therefore, the solar cell module in Patent Document 2 has significant limitations on its arrangement area, and there are issues with the power generation efficiency of the solar cells.

[0007] Therefore, an object of the present invention is to provide a stacked photovoltaic block technology having stacked photovoltaic layers and high photovoltaic efficiency.

[0008] In order to solve the above problems, one representative stacked photovoltaic block of the present invention is a block body formed by stacking flat photovoltaic cells, in which the height dimension of the block body is equal to or greater than either the depth dimension or the width dimension, and the transparent substrate constituting the photovoltaic cells has transparent conductive films formed on both sides thereof to serve as the upper and lower electrodes of the photovoltaic cells.

[0009] According to the present invention, it is possible to provide a stacked photovoltaic block technology having stacked photovoltaic layers and high photovoltaic efficiency. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments of the invention.

[0010] FIG. 1A is a schematic view of a typical stacked photovoltaic block. FIG. 1B is a top view of a typical stacked photovoltaic block. FIG. 1C is a side view of a typical stacked photovoltaic block. FIG. 2A is a cross-sectional view of an example of a configuration of a photovoltaic cell. FIG. 2B is a cross-sectional view of an example of a configuration of a photovoltaic cell. FIG. 2C is a cross-sectional view of an example of a configuration of a photovoltaic cell. FIG. 2D is a cross-sectional view of an example of a configuration of a photovoltaic cell. FIG. 3 is a diagram illustrating the relationship of the light receiving angle for a single photovoltaic cell. FIG. 4 is a diagram illustrating the relationship of the light receiving angle for a stacked photovoltaic block. FIG. 5 is a graph showing the oblique incident light characteristics (cosine characteristics) of illuminance. FIG. 6 is a graph showing the relationship between the oblique incident light characteristics and the conversion efficiency. FIG. 7A is a top view illustrating a photovoltaic cell of a modified example. FIG. 7B is a cross-sectional view illustrating a photovoltaic cell of a modified example. FIG. 7C is a cross-sectional view illustrating a stacked photovoltaic block of a modified example. FIG. 8A is a schematic view of a frame that accommodates stacked photovoltaic blocks. Fig. 8B is a diagram illustrating a process of accommodating photovoltaic cells in a frame. Fig. 8C is a schematic diagram of a window member and an exterior material accommodated in a frame. Fig. 9 is a schematic cross-sectional view of an extraction electrode of a stacked photovoltaic block. Fig. 10 is a cross-sectional view of three types of transparent substrates. Fig. 11 is a cross-sectional view of a stacked photovoltaic block of the first embodiment.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the present invention is not limited to this embodiment. In addition, in the description of the drawings, the same parts are designated by the same reference numerals.

[0012] In this disclosure, the term "window / exterior component" refers to various forms of components, including windows installed in buildings and structures, all translucent components that partition the interior space of buildings and structures, all translucent components that separate the interior and exterior of automobile bodies, and all components that make up the roofs and walls of buildings and structures, including not only components that are the outermost layer of a building or structure that comes into contact with the outside air, but also components used in the inner layers. Furthermore, the stacked photovoltaic block of this disclosure can be combined with a frame or the like to be used as a window component, exterior material, or other component. Furthermore, the stacked photovoltaic block of this disclosure can be used for various purposes, such as objects, power generation devices, and charging devices.

[0013] [Normal Stacked Photovoltaic Block] <Stacked Photovoltaic Block> A normal stacked photovoltaic block will be described below with reference to FIGS. 1A to 1C. FIG. 1A is a schematic view of a stacked photovoltaic block. In FIG. 1A, a stacked photovoltaic block 10 includes multiple layers of photovoltaic cells, each of which includes an upper transparent substrate 1, a lower transparent substrate 2, and a power generation section sandwiched between these two transparent substrates. The photovoltaic cells are stacked such that H is equal to or greater than either L or W, where H is the z-direction dimension of the stacked photovoltaic block 10, L is the x-direction dimension, and W is the y-direction dimension. In other words, where the z-direction dimension is the height, the x-direction dimension is the depth, and the y-direction dimension is the width, the height is equal to or greater than either the depth or the width. Note that, hereinafter, the "height direction" may be referred to as the "stacking direction" in this disclosure. The +z direction is sometimes referred to as the upward direction, and the −z direction is sometimes referred to as the downward direction.

[0014] 1A shows a block formed by stacking five flat photovoltaic cells, but the number of stacked layers is preferably five or more. Note that the photovoltaic cells do not necessarily have to be flat, and may have a curved plate shape. Furthermore, the upper transparent substrate 1 and the lower transparent substrate 2 may be made of a light-transmitting material such as glass or acrylic.

[0015] Next, the planar structure of the stacked photovoltaic block 10 will be described with reference to FIG. 1B . FIG. 1B is a top view of the stacked photovoltaic block. The upper transparent substrate 1 and the lower transparent substrate 2 are offset in the y direction. The photovoltaic region 3 and the sealing portion 4 for sealing the photovoltaic region 3 are disposed in the region where the upper transparent substrate 1 and the lower transparent substrate 2 overlap in the z direction. The sealing portion 4 is disposed so as to surround the photovoltaic region. Note that the photovoltaic region 3 and the sealing portion 4 do not necessarily have to coincide with the region where the upper transparent substrate 1 and the lower transparent substrate 2 overlap in the z direction. The photovoltaic region 3 and the sealing portion 4 may be located inside the region where the upper transparent substrate 1 and the lower transparent substrate 2 overlap in the z direction. The photovoltaic cell shown in FIG. 1B has a light brown photovoltaic region 3 as an example. However, the photovoltaic region 3 does not necessarily have to be colored and may be transparent. It is preferable that the other components are formed of a substantially transparent material.

[0016] Next, the cross-sectional structure of the stacked photovoltaic block 10 will be described with reference to FIG. 1C . FIG. 1C is a side view schematically illustrating the cross-sectional structure of the stacked photovoltaic block. An upper electrode 5 and a lower electrode 6 are disposed on the surfaces of the upper transparent substrate 1 and the lower transparent substrate 2 that contact the photovoltaic region 3, respectively. These upper electrodes 5 and lower electrodes 6 may be transparent conductive films such as FTO or ITO formed on the surfaces of the upper transparent substrate 1 and the lower transparent substrate 2, respectively. In one photovoltaic cell 7, the upper transparent substrate 1 and the lower transparent substrate 2 are offset in the y direction, so that the upper electrode 5 and the lower electrode 6 can be connected to the outside. Electric power generated by the photovoltaic cell can be extracted to the outside through the portions of the upper electrode 5 and the lower electrode 6 that can be connected to the outside.

[0017] (Variations of Photovoltaic Cells) Next, several examples of the configuration of the photovoltaic cell 7 will be described with reference to Figures 2A to 2D. As the photovoltaic cell that can be used in the present invention, any type of photovoltaic cell, photovoltaic element, or solar cell can be used as long as the photovoltaic region can be surrounded by a light-transmitting substrate. Examples of photovoltaic cells are shown in Figures 2A to 2D below, but these do not in any way limit the applicability of the technology of the present disclosure. The photovoltaic cell 7 shown in Figures 2A to 2D is a cross-sectional view of the photovoltaic cell 7 constituting the stacked photovoltaic block shown in Figure 1A in the xz plane.

[0018] The photovoltaic cell shown in Figure 2A is a wet-type photovoltaic element that uses a titanium dioxide layer as a photovoltaic layer. In Figure 2A, the upper transparent substrate 1 is a transparent substrate made of glass or resin, and an upper electrode 5 made of a transparent conductive film such as FTO is formed on one surface. A lower electrode 6 and a charge exchange layer 15 are disposed above the lower transparent substrate 2, and a porous titanium dioxide 12 serving as a photovoltaic layer is disposed below the upper electrode 5. An electrolyte 14 is sealed between the upper electrode 5 and the lower electrode 6. This electrolyte is typically an iodine-based electrolyte prepared by dissolving iodine in a potassium iodide aqueous solution. A sealing portion 4 is in close contact with the upper and lower transparent substrates to prevent the electrolyte 14 from leaking out.

[0019] The photovoltaic cell of Figure 2B differs from that of Figure 2A in that the photovoltaic region employs dye-sensitized porous titanium dioxide 13 in which a sensitizing dye such as a ruthenium complex dye is solidified. In other words, the photovoltaic cell of Figure 2B is a general dye-sensitized photovoltaic element (DSSC: Dye Sensitized Solar Cell). Since the other configurations are the same as those of Figure 2A, the same or equivalent components as those of Figure 2A are designated by the same reference numerals, and their description will be simplified or omitted.

[0020] Next, the photovoltaic cell of Fig. 2C differs from the photovoltaic cell of Fig. 2B in that it does not use porous titanium dioxide as the photovoltaic layer, but instead employs silicon dioxide particles 20 with a particle size of 500 nm or less, which are mixed with ethanol and applied to a charge exchange layer 15 made of platinum or the like, and then dried. Since the other configuration is the same as that of Fig. 2A, the same reference numerals are used for the same or equivalent components as those of Fig. 2A, and their description will be simplified or omitted.

[0021] Next, the photovoltaic cell of Figure 2D differs from Figures 2A to 2C in that it uses two photovoltaic layers: a layer of dye-sensitized porous titanium dioxide 13 and a layer of silicon dioxide particles 20. Since the other configuration is the same as that of Figure 2A, the same or equivalent components as those of Figure 2A are denoted by the same reference numerals, and their description will be simplified or omitted.

[0022] As described above, various photovoltaic elements can be used for the photovoltaic cell 7 in the present disclosure. In particular, photovoltaic elements having a photovoltaic layer made of silicon dioxide, as disclosed in Japanese Patent No. 5848324 and the like, are suitable, but the present disclosure is not necessarily limited to these, and the present disclosure may also be applied to photovoltaic elements using a perovskite film.

[0023] (Photovoltaic Characteristics) Next, the photovoltaic characteristics of the stacked photovoltaic block in which five layers of photovoltaic cells 7 shown in FIG. 1C are stacked will be described with reference to FIGS. 3 and 4, comparing the angle characteristics with a single photovoltaic cell 7. FIG. 3 is a diagram showing the relationship between the light-receiving angles when the in-plane direction of the light-receiving surface is set to 90° and the normal direction is set to 0° for a single photovoltaic cell 7. FIG. 4 is a diagram showing the relationship between the light-receiving angles when the in-plane direction of the light-receiving surface is set to 90° and the normal direction is set to 0° for a stacked photovoltaic block in which five layers of single photovoltaic cells 7 are stacked. In both the cases of FIG. 3 and FIG. 4, the photovoltaic cell 7 is a dye-sensitized photovoltaic element having a photovoltaic layer made of silicon dioxide and dye-containing titanium dioxide as described in FIG. 2. Then, a photovoltaic power of 1 sun (1,000 W / m ２ When the light beam of 1000 W was irradiated onto the sample, the maximum output shown in Table 1 was obtained.

[0024] As can be seen from the above data, the stacked photovoltaic block can exhibit a considerable degree of photovoltaic capacity even if light is not necessarily incident from the normal to the light-receiving surface.

[0025] (Oblique Incident Light Characteristics) Next, for a photovoltaic cell in which a photovoltaic region is surrounded by a translucent substrate, the oblique incident light characteristics (cosine characteristics) of illuminance and the relationship between the oblique incident light characteristics and conversion efficiency will be described with reference to Figures 5 and 6.

[0026] Figure 5 is a graph showing the oblique incident light characteristics (cosine characteristics) of illuminance. The illuminance on the light-receiving surface of a photovoltaic element changes in proportion to the cos θ of the incident angle θ of light incident on the light-receiving surface, and the illuminance (E2) when illuminated from the oblique θ direction is cos θ times the illuminance (E1) when illuminated from the normal direction to the light-receiving surface. Therefore, when the normal direction to the light-receiving surface (θ = 0°) is set to "1", the incident light characteristics for each angle are as shown in the graph in Figure 5.

[0027] (Conversion Efficiency of Obliquely Incident Light) Next, the relationship between obliquely incident light characteristics and conversion efficiency will be described with reference to FIG. 6. FIG. 6 is a graph showing the relationship between obliquely incident light characteristics and conversion efficiency. In the graph, the solid line (DSSC-1) shows the conversion efficiency at each angle, using the left vertical axis, when the normal direction (θ = 0°) to the DSSC photovoltaic cell (single cell) is set to "1". In addition, the dotted line (single crystal silicon-1) shows the results of measuring similar conversion efficiency characteristics using a single crystal silicon photovoltaic element. This dotted line also shows the conversion efficiency at each angle, and is therefore plotted using the left vertical axis.

[0028] In the graph of FIG. 6, the conversion efficiency η is a value calculated by the following formula: η = Pmax ÷ (E × A) × 100 η: conversion efficiency [%] Pmax: output at the optimum operating point [W] E(Eθ): irradiance [W / m ２ ] A: Light receiving area [m ２ ]

[0029] In the graph of Figure 6, the solid line (DSSC-1) indicates that the conversion efficiency increases with increasing θ. This is thought to be due to factors such as wall reflection in the measurement environment, light deflection from the glass side, and the influence of light incident from the back side as the angle increases. In any case, it can be seen that for photovoltaic cells sandwiched between translucent substrates, it is possible to significantly increase the photovoltaic efficiency even if the light-receiving surface is not necessarily set perpendicular to the light incident direction. Conventional photovoltaic cells made of single-crystal silicon, amorphous silicon, or the like, required the light-receiving surface to be set facing the direction of sunlight incidence. However, in photovoltaic elements having a photovoltaic region sandwiched between translucent substrates, as shown in the present disclosure, it is possible to achieve high photovoltaic efficiency even with a stacked photovoltaic block in which multiple translucent substrates are stacked.

[0030] [Modification of a conventional stacked photovoltaic block] Next, a modification that takes into account the low incidence angle dependency of the photovoltaic capacity of the stacked photovoltaic block will be described with reference to Figures 7A to 7C. The modification differs from a conventional stacked photovoltaic block in that the photovoltaic cell has a horizontally elongated shape. Figure 7A is a top view of the photovoltaic cell as viewed from the z direction, and Figure 7B is a schematic cross-sectional view of the photovoltaic cell in the yz plane. And Figure 7C is a schematic cross-sectional view of the stacked photovoltaic block in the modification in the yz plane. In the following description, components that are the same as or equivalent to those in the above-mentioned conventional stacked photovoltaic block will be assigned the same reference numerals, and their description will be simplified or omitted.

[0031] In the stacked photovoltaic block of the modified example, the photovoltaic cells are set in a horizontally elongated shape, so that when the stacked photovoltaic block is formed, a large area can be obtained in the yz plane, as shown in Fig. 7C. Since the upper and lower transparent substrates occupy most of the area in the yz plane, the entire stacked photovoltaic block appears as a nearly transparent planar block when viewed from the x-axis direction.

[0032] Next, with reference to Figures 8A to 8C, an example of using the modified stacked photovoltaic block as a window member or exterior material will be described. Figure 8A is a schematic diagram of a frame 16 for fixing and housing the stacked photovoltaic block as a member of a certain size. The frame 16 can be made of a metal such as aluminum to have a sash structure so that the stacked photovoltaic block can be housed inside the frame 16. By sequentially inserting horizontally elongated photovoltaic cells 7 into such a frame 16 as shown in Figure 8B, a window member or exterior material with photovoltaic capabilities can be obtained, as shown in Figure 8C, which is surrounded by a frame such as aluminum and whose entire surface is made of a transparent conductive substrate such as glass.

[0033] Next, an example of an extraction electrode 17 for extracting power from a stacked photovoltaic block will be described with reference to FIG. 9 . FIG. 9 is a schematic cross-sectional view of an extraction electrode installed on the side of the stacked photovoltaic block where the upper electrode 5 or the lower electrode 6 is exposed to the outside. The extraction electrode 17 is formed on one surface in a shape that engages with the irregularities on the side of the stacked photovoltaic block where the upper electrode 5 or the lower electrode 6 is exposed to the outside, and is composed of an extraction electrode base 18 and an extraction electrode contact 19 that contacts the upper electrode 5 or the lower electrode 6. The extraction electrode base 18 is formed of plastic, rubber, glass, or the like, and the extraction electrode contact 19 is conductively treated, such as by silver plating, to ensure conductivity. By using such an extraction electrode, power can be easily extracted from the stacked photovoltaic block. Furthermore, by providing such an extraction electrode 17 on the uneven side surface of the stacked photovoltaic block as a member that absorbs the uneven shape of the stacked photovoltaic block, it is possible to eliminate rattling of the stacked photovoltaic block within the frame 16 and to hold the stacked photovoltaic block stably within the frame.

[0034] First Embodiment Next, a first embodiment of the present disclosure, which is a further improvement of the above-described ordinary stacked photovoltaic block and its modified example, will be described with reference to FIGS. 10 and 11 .

[0035] In the above-described typical stacked photovoltaic block and its modified examples, each photovoltaic cell has two transparent substrates (an upper transparent substrate and a lower transparent substrate) with a photovoltaic region therebetween. However, the stacked photovoltaic block of the first embodiment employs transparent substrates with transparent electrode films on both the upper and lower surfaces of the substrate, so that between adjacent photovoltaic cells in the vertical direction, one lower transparent substrate and the other upper transparent substrate are formed from a single transparent substrate.

[0036] Examples of transparent substrates constituting the stacked photovoltaic block in the first embodiment will be described with reference to Fig. 10. Fig. 10 is a cross-sectional view of three types of transparent substrates used in the first embodiment. The transparent substrates shown in Fig. 10(a) and (c) are the same as the upper transparent substrate 1 and the lower transparent substrate 2 used in a normal stacked photovoltaic block and its modified example, respectively. The intermediate transparent substrate 9 shown in Fig. 10(b) has electrodes made of transparent conductive films on its upper and lower surfaces.

[0037] Next, with reference to FIG. 11 , the cross-sectional configuration of a stacked photovoltaic block using the three types of transparent substrates described in FIG. 10 will be described. In the following description, components that are the same as or equivalent to those in the above-described normal stacked photovoltaic block and its modified example will be denoted by the same reference numerals, and their description will be simplified or omitted. In FIG. 11 , the uppermost and lowermost layers of the stacked photovoltaic block employ an upper transparent substrate 1 and a lower transparent substrate 2, as in the normal stacked photovoltaic block and its modified example. The transparent substrates other than the uppermost and lowermost layers of the stacked photovoltaic block employ the intermediate transparent substrate 9 described in FIG. 10( b). As a result, in the stacked photovoltaic block of the first embodiment, the uppermost photovoltaic region 3 is formed between the upper transparent substrate 1 and the intermediate transparent substrate 9, and the second-highest photovoltaic region 3′ shares the intermediate transparent substrate 9 below the uppermost photovoltaic region 3, and the transparent conductive film below the intermediate transparent substrate 9 is used as the upper electrode. Similarly, the photovoltaic cells below this one share a transparent substrate with the adjacent photovoltaic cells, and form an upper electrode 5 and a lower electrode 6 .

[0038] <Actions and Effects> The stacked photovoltaic block of the first embodiment can reduce the amount of transparent substrates constituting the block by approximately 50% compared to a standard stacked photovoltaic block and its modified stacked photovoltaic block. This significantly increases the proportion of the photovoltaic region in the stacked photovoltaic block and significantly increases the amount of photovoltaic power generated per unit volume. Furthermore, compared to conventional solar cell modules, the stacked photovoltaic block and its modified stacked photovoltaic block achieve significant benefits in terms of non-blocking of light from outdoors to indoors when used as a window member and sufficient photovoltaic power generation by utilizing light incident from multiple directions. Furthermore, the size of a basic photovoltaic cell is approximately 1 mm thick for the upper and lower transparent substrates, and the thickness of the photovoltaic region can be made 1 mm or less. Therefore, it is possible to similarly combine photovoltaic cells to form stacked photovoltaic blocks of various shapes.

[0039] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the present invention. For example, in the first embodiment, the upper and lower transparent substrates 1 and 2 are employed in the top and bottom layers of the stacked photovoltaic block, as in the case of a typical stacked photovoltaic block and its modified examples. However, in the stacked photovoltaic block of the present disclosure, the intermediate transparent substrate 9 can also be used as the transparent substrate in the top and bottom layers. Furthermore, it is not necessary for all transparent substrates other than the top and bottom layers of the stacked photovoltaic block to be composed of the intermediate transparent substrate 9; some of the transparent substrates can be composed of the upper transparent substrate 1 and the lower transparent substrate 2. Furthermore, the stacked photovoltaic block of the first embodiment can be configured as, for example, a horizontally elongated photovoltaic cell, as in the case of a typical stacked photovoltaic block and its modified examples, or the horizontally elongated photovoltaic section can be divided to provide multiple photovoltaic sections.

[0040] Furthermore, the shapes of the photovoltaic cells and the photovoltaic section are not limited to rectangular shapes, but various shapes such as circular, elliptical, and polygonal shapes can be adopted. Therefore, the shape of the stacked photovoltaic block is not limited to a plate shape, but can be cylindrical or various other shapes. Furthermore, although the upper and lower transparent substrates have been described as being flat, the transparent substrates are not limited to being flat and may have curved surfaces.

[0041] 1: Upper transparent substrate 2: Lower transparent substrate 3: Photovoltaic region 4: Sealing portion 5: Upper electrode 6: Lower electrode 7: Photovoltaic cell 9: Middle transparent substrate 10: Stacked photovoltaic block 12: Porous titanium dioxide 13: Dye-sensitized porous titanium dioxide 14: Electrolyte 15: Charge exchange layer 16: Frame 17: Extraction electrode 18: Extraction electrode base 19: Extraction electrode contact portion 20: Silicon dioxide particles

Claims

1. A stacked photovoltaic block is a block body in which flat photovoltaic cells are stacked, the height dimension of the block body being equal to or greater than either the depth dimension or the width dimension, and the transparent substrate constituting the photovoltaic cells has transparent conductive films formed on both sides thereof to serve as the upper and lower electrodes of the photovoltaic cells.

2. A stacked photovoltaic block consisting of a block of at least five or more flat photovoltaic cells, in which a portion of the transparent substrate constituting the photovoltaic cells has a transparent conductive film on both sides thereof which serves as the upper and lower electrodes of the photovoltaic cells, and in which the end faces of the stacked photovoltaic cells are aligned in an approximately flat shape.

3. A stacked photovoltaic block according to claim 1 or 2, wherein the photovoltaic cell has a structure in which a photovoltaic region is sandwiched between transparent substrates.

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