Solar power generation system

Abstract

We provide a solar power generation system that suppresses the reduction in plant growth. [Solution] The photovoltaic power generation system includes a solar cell module positioned above a cultivation area where a predetermined plant is grown. The solar cell module has two substrates and a power generation element provided between the two substrates. The solar cell module has a light transmittance based on the light saturation point of the predetermined plant.

Description

Technical Field

[0001] The present disclosure relates to a solar power generation system including a power generation module used for solar power generation.

Background Art

[0002] A solar power generation system combining solar power generation and plant cultivation has been conventionally studied. In Patent Document 1, plants are cultivated using sunlight that is not utilized by a power generation module by arranging silicon-based power generation modules at intervals.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Since the leaves of a plant may be located in the shadow area of a power generation module, the plant is repeatedly exposed to a state where sunlight directly irradiates and a state where sunlight is blocked by the shadow of the power generation module. In the state where sunlight is blocked, it may fall below the light compensation point of the plant, and if the time that the leaves are located in the shadow area becomes long, the growth of the plant is hindered.

[0005] The present disclosure provides a solar power generation system that suppresses the reduction of plant growth.

Means for Solving the Problems

[0006] The solar power generation system of the present disclosure includes a solar cell module disposed above a cultivation section where a predetermined plant is cultivated. The solar cell module has two substrates and a power generation element provided between the two substrates. The solar cell module has a light transmittance based on the light saturation point of a predetermined plant.

Effects of the Invention

[0007] The photovoltaic power generation system described herein provides a photovoltaic power generation system that suppresses the reduction in plant growth. [Brief explanation of the drawing]

[0008] [Figure 1] External view of the solar cell system of Embodiment 1 [Figure 2] System configuration diagram of a solar cell system [Figure 3] Schematic front view of a solar cell module according to an embodiment. [Figure 4] Schematic cross-sectional view of the solar cell module along the IV-IV line in Figure 3. [Figure 5] Schematic front view of the power generation element in the power generation module shown in Figure 3. [Figure 6] Figure 3: Enlarged perspective view of a portion of the power generation element. [Figure 7] Enlarged cross-sectional view along line VII-VII in Figure 6 [Figure 8A] Enlarged cross-sectional view along line VIII-VIII in Figure 6 [Figure 8B] Enlarged cross-sectional view along line VIII-VIII in Figure 6 of the modified example. [Figure 9] Graph showing the relationship between the amount of light given to plants and the rate of photosynthesis, categorized by shade tolerance type. [Figure 10] A graph showing the optical properties of a certain region of the solar cell layer in a solar cell module. [Figure 11] A graph showing the optical properties of a region without a solar cell layer in a solar cell module. [Figure 12] An explanatory diagram illustrating the state of light irradiated onto plant leaves in the comparative example. [Figure 13] A graph showing the relationship between the amount of light supplied to a plant and the rate of photosynthesis. [Figure 14] An explanatory diagram illustrating the state of light irradiated onto the leaves of a plant in Embodiment 1. [Figure 15] A table relating the light saturation point and transmittance. [Figure 16] Flowchart showing the manufacturing process of a solar cell module [Figure 17] Expanded perspective view of a part of a power generation element in Embodiment 2 [Figure 18] External view of a solar cell system in a modified example [Figure 19] External view of a solar cell system in a modified example

Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, terms indicating a specific direction or position (terms including, for example, "up", "down", "right", and "left") are used as necessary. However, the use of these terms is for facilitating the understanding of the present disclosure with reference to the drawings, and the technical scope of the present disclosure or the usage mode of the power generation module according to the present disclosure is not limited by the meanings of these terms. Further, the following description is merely illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses. Furthermore, the drawings are schematic, and the ratios of each dimension etc. do not necessarily match the actual ones.

[0010] In this specification, "electrically connected" means that at least one of the following conditions is satisfied: current can flow between a plurality of components, a plurality of components are capacitively coupled, and a plurality of components are electromagnetically coupled.

[0011] (Embodiment 1) Hereinafter, this embodiment will be described with reference to the drawings.

[0012] [1. Configuration of a solar power generation system] Refer to FIGS. 1 and 2. FIG. 1 is an external view of a solar cell system 1. FIG. 2 is a system configuration diagram of the solar cell system 1.

[0013] The solar cell system 1 is installed in an agricultural facility such as a glasshouse 2. The solar cell modules 10, which generate electricity from sunlight, may be installed on the roof 2a, windows 2b, or walls 2c of these buildings, or as part of them. In this embodiment, the solar cell modules 10 are installed as part of the roof 2a and walls 2c of the glasshouse 2. Depending on the sunlight irradiation conditions and the desired amount of power generated, it is determined which surface of the glasshouse 2 the solar cell modules 10 will be installed on. The solar cell system 1 may also be installed in a vinyl greenhouse instead of a glasshouse 2. The larger the substrate area of ​​the solar cell module 10 in this disclosure, the greater the effect of the present invention can be obtained, as the proportion of sunlight blocked by materials other than the solar cell module per unit area of ​​the building where it is installed can be reduced.

[0014] Refer to Figure 2. The solar cell system 1 comprises a plurality of solar cell modules 10, bus wiring 3a and 3b, a controller 4, and an output unit 5. Furthermore, the solar cell system includes a storage battery 6, a lighting unit 7, a drive unit 8, and a cultivation unit 9. The output unit 5 is connected to the storage battery 6, the lighting unit 7, and the drive unit 8, and is, for example, a distribution board.

[0015] The solar cell module 10 converts sunlight into electrical energy. The positive lead wire 23 of the solar cell module 10 is connected to the bus wiring 3a, and the negative lead wire 24 of the solar cell module 10 is connected to the bus wiring 3b. Multiple solar cell modules 10 are connected in parallel or in series to the bus wirings 3a and 3b. The sum of the currents flowing from each solar cell module 10 is input to the controller 4.

[0016] The controller 4 includes an integrated circuit (which can be implemented using semiconductor elements, etc.) and a power conditioner, and converts the power converted by the solar cell module 10 into power usable by the battery 6, lighting unit 7, and drive unit 8. The converted power is supplied to the battery 6, lighting unit 7, and drive unit 8 via the output unit 5.

[0017] The battery 6 stores excess power that cannot be used by the lighting unit 7 and the drive unit 8. The battery 6 supplies the stored power to the lighting unit 7 and the drive unit 8 at night or on rainy days when the solar cell module 10 cannot generate power.

[0018] The lighting unit 7 emits light using the supplied power. The lighting unit 7 is, for example, an LED light or a fluorescent lamp.

[0019] The drive unit 8 uses the supplied power to drive a motor or the like. The drive unit 8 is, for example, a blower. In this way, the power generated by each solar cell module 10 may be stored, consumed, or further transmitted to the outside via the output unit 5.

[0020] The cultivation area 9 is the region where plants are planted, and is located, for example, below the solar cell module 10. The cultivation area 9 is, for example, the soil area.

[0021] [2. Solar cell module configuration] The basic configuration of the solar cell module 10 will be explained with reference to Figures 3 and 4. Figure 3 is a schematic front view of the solar cell module 10. Figure 4 is a schematic cross-sectional view of the solar cell module of Figure 3 along line IV-IV.

[0022] As shown in Figures 3 and 4, the solar cell module 10 comprises a first substrate 11, a second substrate 12, a power generation element 100, and a filler material 32. The solar cell module 10 is arranged such that ambient light is incident on it from the first substrate 11 side, for example.

[0023] The Z-direction shown in Figures 3 and 4 corresponds to the thickness direction of the solar cell module 10. The thickness direction of the solar cell module 10 is, for example, the stacking direction of the two substrates 11 and 12, or the stacking direction of the solar cell layers contained in the solar cell module 10. Furthermore, the directions that intersect (in this case are orthogonal) with each other in a plane perpendicular to the Z-direction are defined as the X-direction and the Y-direction.

[0024] The first substrate 11 and the second substrate 12 are light-transmitting. "Light-transmitting" means the ability to transmit light in the wavelength range necessary for plant growth. The first substrate 11 and the second substrate 12 are, for example, glass substrates (tempered glass substrates) and have a thickness of, for example, 2 mm or more. As shown in Figure 3, the second substrate 12 may be omitted from the top view of the solar cell module 10 or a part thereof for clarity.

[0025] As shown in Figure 4, the first substrate 11 and the second substrate 12 are arranged facing each other in the Z direction. The first substrate 11, which is the light-receiving side, may be thinner than the second substrate 12. The peripheral edges of the first substrate 11 and the peripheral edges of the second substrate 12 are sealed by a sealing member 50. In a plan view from the Z direction, the sealing member 50 is located outside the area where the power generation element 100 is arranged. As the sealing member 50, a thermoplastic elastomer such as butyl rubber can be used to suppress water vapor intrusion. By using a resin material with low oxygen permeability in combination, the sealing performance can be further improved.

[0026] The power generation element 100 has a solar cell layer and is located between the first substrate 11 and the second substrate 12. In the example shown in Figure 1, the power generation element 100 is stacked on the first substrate 11. A portion of the light incident on the solar cell module 10 passes through the power generation element 100, and a portion is absorbed by the power generation element 100 and converted into electrical energy.

[0027] As shown in Figure 6, the filler material 32 is located between the second substrate 12 and the first substrate 11, and between the second substrate 12 and the power generation element 100. For these fillers 32, for example, polyvinyl butyral (PVB), ethylene vinyl acetate copolymer (EVA), polyolefin (PO), etc. can be used. The filler material 32 allows the first substrate 11 and the second substrate 12 to be held in close contact, thereby ensuring the strength of the solar cell module 10.

[0028] The filler material 32 is formed by placing the filler material on the power generation element 100 and the first substrate 11, then sealing it with the second substrate 12 and the sealing member 50, and finally pressing and melting it to fill the internal space. Therefore, the filler material 32 is bonded to the first substrate 11 and the power generation element 100.

[0029] As shown in Figure 3, the solar cell module 10 includes a pair of wires 21 and 22. The wires 21 and 22 are, for example, metal wires (e.g., tab wires or lead wires). The wires 21 and 22 are electrically connected to the power generation element 100 within the space enclosed by the first substrate 11, the second substrate 12, and the sealing member 50.

[0030] In the sealing member 50, a through-hole is formed that communicates from the internal space of the solar cell module 10 to the outside, and the wirings 21 and 22 pass through the sealing member 50 from within the area enclosed by the sealing member 50 to the outside of the sealing member 50. The wirings 21 and 22 that extend to the outside of the sealing member 50 are connected to the terminal box 19. Within the terminal box 19, wiring 21 is electrically connected to lead wire 23, and wiring 22 is electrically connected to lead wire 24.

[0031] As shown in Figure 3, the solar cell module 10 includes tab wires 41 and 42 extending in the Y-axis direction between the first substrate 11 and the second substrate 12. Wiring 21 includes tab wire 41, and wiring 22 includes tab wire 42. These tab wires are, for example, metal wires. In this embodiment, wirings 21 and 22 are each made of copper wire covered with solder (tab wires). Tab wire 41 is provided on one end of the power generation element 100 in the X direction. Tab wire 42 is provided on the other end of the power generation element 100 in the X direction.

[0032] [3. Structure of the power generation element 100] The structure of the power generation element 100 in the solar cell module 10 will be explained with reference to Figures 5 to 8. Figure 5 is a schematic top view of the power generation element 100 in the solar cell module 10. Figure 6 is an enlarged top view of a part of the power generation element 100 in Figure 5. Figure 6 shows an enlarged view of the region 100a shown in Figure 5. Figure 7 is an enlarged cross-sectional view along the VIA-VIA line in Figure 6. Figure 8 is an enlarged cross-sectional view along the VIB-VIB line in Figure 6.

[0033] As shown in Figure 5, the power generation element 100 comprises a plurality of battery cells 150 supported by the first substrate 11 and connected in series, tab wires 41 and 42, on a light-transmitting first substrate 11. The plurality of battery cells 150 connected in series are located on a portion of the main surface 11s (inner surface) of the first substrate 11.

[0034] The solar cell 150 includes, for example, a pair of transparent electrodes and a solar cell layer located between the pair of transparent electrodes. The solar cell 150 only needs to be supported by the main surface 11s of the first substrate 11 and does not need to be in direct contact with it. Multiple solar cells 150 are connected in series along the X direction from one end to the other of the first substrate 11.

[0035] Tab wire 41 is located on one end of the first substrate 11. Tab wire 42 is located on the other end of the first substrate 11.

[0036] Solar cells 150 connected in series in the X-axis direction are also arranged on the first substrate 11 in the Y-axis direction. One end of each solar cell 150 connected in series in the X-axis direction is connected to tab wire 41, and the other end is connected to tab wire 42. Therefore, the power generated in the solar cells 150 connected in series in the X-axis direction is extracted by tab wires 41 and 42, respectively.

[0037] The solar cells 150 connected in series are arranged on the main surface 11s of the first substrate 11, spaced apart from each other in the Y direction, and may, for example, extend parallel to each other in a plan view from the Z direction. In a plan view from the Z direction, a second groove 160 is formed between adjacent solar cells 150 in the Y-axis direction.

[0038] In other words, as shown in Figures 6 to 8B, the power generation element 100 has a plurality of solar cells 150 arranged in series with a first pitch Pt1 and in parallel with a second pitch Pt2, a first groove 130 formed between adjacent solar cells 150 in the series direction, and a second groove 160 formed between adjacent solar cells 150 in the parallel direction.

[0039] For example, the first pitch Pt1 is between 1 mm and 10 mm, the second pitch Pt2 is between 0.1 mm and 100 mm, the width of the first groove 130 is between 0.08 mm and 1 mm, and the width of the second groove 160 is between 0.1 mm and 50 mm. The length of the second pitch Pt2 is determined by the length of the plant leaf (leaf blade), and the width of the second groove 160 is determined by the light saturation point of the plant.

[0040] Each solar cell 150 has a laminated structure in which layers including a transparent electrode 151 as a first electrode layer, a solar cell layer PV as a power generation layer, and a transparent electrode 155 as a second electrode layer are stacked in the Z direction. These layers are supported on the main surface 11s of the first substrate 11. The solar cell layer PV is located between the transparent electrode 151 and the transparent electrode 155. The transparent electrode 151 as the second electrode layer is located on the first substrate 11 side of the solar cell layer PV. Note that the first electrode layer is not limited to a transparent electrode; an opaque electrode layer may also be used. The solar cell layer PV is a thin film type and is, for example, a laminated film including an n-type semiconductor layer 152 as an electron transport layer, an i-type semiconductor layer 153, and a p-type semiconductor layer 154 as a hole transport layer, from the first substrate 11 side. The solar cell layer PV may further include an electron transport layer and / or a hole transport layer as needed.

[0041] The solar cell layer PV and the transparent electrode 155 are separated for each solar cell 150. In the example shown in Figure 8A, the solar cell layer PV, the transparent electrode 155 and the transparent electrode 151 are separated for each solar cell 150 by the second groove 160. In the modified example shown in Figure 8B, the solar cell layer PV and the transparent electrode 155 are separated for each solar cell 150 by the second groove 160, but the transparent electrode 151 is not separated for each solar cell 150 by the second groove 160.

[0042] Each solar cell 150 has a transparent electrode 151, a transparent electrode 155, and a solar cell layer PV located between the transparent electrodes 151 and 155. The transparent electrode 151 (or transparent electrode 155) of the solar cell 150 located at one end in the X-axis direction is electrically connected to a tab wire 41. Similarly, the transparent electrode 155 (or transparent electrode 151) of the solar cell 150 located at the other end in the X-axis direction is electrically connected to a tab wire 42. The transparent electrode 151 is located at the bottom of each adjacent solar cell 150 along the X-axis direction. The transparent electrode 155 has an interlayer connection portion 155a extending downward near the other end in the X-axis direction. The lower end of the interlayer connection portion 155a is connected to one side of the transparent electrode 151 in the X-axis direction.

[0043] The i-type semiconductor layer 153 is a layer that converts absorbed light into photoelectric energy (photoelectric conversion layer). The i-type semiconductor layer 153 contains, for example, a perovskite compound (perovskite semiconductor) as a photoelectric conversion material. The perovskite compound is a perovskite crystal structure represented by the chemical formula ABX3 and structures having similar crystals. A is a monovalent cation, B is a divalent cation, and X is a halogen anion. The transparent electrodes 151 and 155 are translucent metal oxide layers such as indium tin oxide (ITO) or indium zinc oxide (IZO), or a fluorine-doped tin oxide (FTO) layer. Note that the materials of each layer constituting the power generation element 100 are not limited to those described above, and known materials may be used.

[0044] [4.Light saturation point] One of the parameters that determines the amount of plant growth is the light saturation point. The light saturation point indicates the maximum amount of light required for photosynthesis in plants. In other words, there is wasted energy that does not affect plant growth even if the amount of light exceeds the light saturation point.

[0045] Plants with a light saturation point of 20-30 klx include, for example, butterbur, Japanese ginger, Japanese parsley, lettuce, green beans, and chili peppers. Plants with a light saturation point of 40-60 klx include, for example, eggplant, Chinese cabbage, cabbage, peas, celery, and cucumbers. Plants with a light saturation point of 70-80 klx include, for example, tomatoes, taro, and watermelon.

[0046] Refer to Figure 9. Figure 9 is a graph showing the relationship between the amount of light given and the rate of photosynthesis for plants categorized by shade tolerance type. Graph gr1 shows the rate of photosynthesis for weakly shade-tolerant plants, graph gr2 shows the rate of photosynthesis for moderately shade-tolerant plants, and graph gr3 shows the rate of photosynthesis for strongly shade-tolerant plants.

[0047] Plants with low light saturation points, such as Japanese ginger and lettuce, are highly shade-tolerant, and their photosynthetic rate saturates early as light intensity increases. Since highly shade-tolerant plants maintain sufficient growth even in weak light, increasing light intensity does not increase their growth. Therefore, lowering the light transmittance of the solar cell module 10 does not hinder plant growth.

[0048] Plants with high light saturation points, such as tomatoes and watermelons, have weak shade tolerance, meaning their photosynthetic rate is less likely to saturate, unlike plants with strong shade tolerance. Since these plants grow more as they receive more light, a high light transmittance from the solar cell module 10 is desirable.

[0049] Therefore, by changing the light transmittance of the solar cell module 10 according to the plants being cultivated in the cultivation unit 9, the balance between plant growth and the amount of power generated by the solar cell module 10 can be optimized for any given time when light is being shone. To achieve this, the amount of light transmitted from the solar cell module 10 is set to the light saturation point of the plants being cultivated in the cultivation unit 9.

[0050] In Embodiment 1, the amount of light transmitted through the solar cell module 10 is adjusted by the ratio of the total area of ​​the first groove 130 and the second groove 160 to the area of ​​the solar cell module 10. In the following description, when a transparent electrode 155 is used as the first electrode layer of the solar cell 150, the area of ​​the interlayer connection portion 155a of the transparent electrode 155 is also added to the area of ​​the first groove 130. In the manufacturing process of the solar cell 150, grooves are formed in the solar cell layer PV to form the interlayer connection portion 155a, and the area of ​​these grooves when viewed from above is also considered to be part of the area of ​​the first groove 130. The first groove 130 may be formed by physically cutting the first electrode layer to ensure light transmission, or the interlayer connection portion 155a may be formed by a material that is light-transmitting.

[0051] Figure 10 is a graph showing the optical properties of a certain region of the solar cell layer PV in the solar cell module 10. Graph gr4 shows the light absorption rate with respect to wavelength of light. Graph gr5 shows the light transmittance with respect to wavelength of light. The wavelength range of light necessary for plant growth is, for example, 400-700 nm, but since light in this wavelength range is also absorbed by the solar cell layer PV, the transmittance is less than 60%.

[0052] Figure 11 is a graph showing the optical properties of the region without photovoltaic (PV) in the solar cell module 10. Graph gr6 shows the light transmittance for a given wavelength of light. Graph gr7 shows the light reflectance for a given wavelength of light. In the region without PV in the solar cell layer, the light transmittance in the wavelength range necessary for plant growth is 60% or more. Therefore, the larger the region without PV in the solar cell module 10, the higher the light transmittance in the solar cell module 10, and the more light can be supplied to plants.

[0053] Figure 12 is an explanatory diagram illustrating the light conditions irradiated onto plants in a comparative example. When solar cell modules with low light transmittance are placed at intervals, when viewed on a per-leaf basis, two conditions occur: state C1, where light passing through the gaps between solar cell modules irradiates almost the entire area of ​​the leaf Lf, and state C2, where light does not irradiate almost the entire area of ​​the leaf Lf due to the shadow of the solar cell modules. As the angle of the sun changes over time, the leaves of plants grown below the solar cell modules will repeatedly experience states C1 and C2. Furthermore, depending on the relative positions of the solar cell modules and the plants, some leaves will remain in state C1, while others will remain in state C2.

[0054] Figure 13 is a graph showing the relationship between the amount of sunlight and the rate of photosynthesis in leaves. For example, in state C1, 1.0 [sun] of light is irradiated onto the leaf Lf, and in state C2, 0.1 [sun] of light is irradiated onto the leaf Lf. At the timing in state C1, the amount of light above the light saturation point... Since the light is shone on the leaves (Lf), the amount of light equivalent to 1.0[sun]-light saturation is wasted energy that is not used for photosynthesis or solar power generation.

[0055] In state C2, 0.9 [sun] of light is used for solar power generation, but the necessary amount of light is not irradiated to the leaves (Lf), thus hindering plant growth. Because the state alternates between C1 and C2 depending on the angle of the sun, the efficiency of light utilization is poor, and plant growth efficiency is also poor.

[0056] In contrast, according to the solar cell module 10 of Embodiment 1, the light transmittance is determined in accordance with the light saturation amount of the plant, thereby improving the efficiency of light utilization and the growth efficiency of the plant.

[0057] By forming a second pitch Pt2, which is also the pitch of the second groove 160, according to the plant's light saturation level, for example, by making the spacing of the second groove 160 shorter than the leaf blade Lg of the plant's leaf Lf, light can be irradiated onto the leaf Lf in a striped pattern, as shown in Figure 14. This reduces the influence of the sun's angle and allows the leaf Lf to be irradiated with the light saturation level at any given time. Furthermore, regardless of the relative positions of the solar cell module 10 and the plant, the light saturation level can be irradiated onto any leaf Lf at any position.

[0058] Since the leaf blade Lf of agriculturally cultivated plants is approximately 5 mm or longer, if the second pitch Pt2 is at least less than the length of the leaf blade, i.e., less than 5 mm, light transmitted through the second groove 160 will irradiate the leaf Lf. For example, since the leaf blade of a trifoliate leaf is 5 cm to 20 cm long, if the second pitch Pt2 is less than 5 mm, it is possible to sufficiently irradiate the leaf Lf in a striped pattern as shown in Figure 14.

[0059] Next, we will explain how to set the light transmittance of the solar cell module 10 based on the light saturation point of the plant.

[0060] The light transmittance Lt is a value [%] greater than 0 and less than 100, and within the range of +30 to -30 relative to the light saturation point Sp [kLX] of the plants grown in cultivation section 9. In other words, it satisfies the following relationship. 0 <Lt<100 ···(1) Sp-30 ≤ Lt ≤ Sp+30 ... (2)

[0061] For example, in the case of a plant with a light saturation point Sp of 80, the light transmittance Lt1 of the solar cell module 10 will be as follows. 50 ≤ Lt1 < 100 ···(3)

[0062] Furthermore, for plants with a light saturation point Sp of 20, the light transmittance Lt2 of the solar cell module 10 is as follows. 0 <Lt2≦50 ···(4)

[0063] Alternatively, instead of determining the transmittance Lt using equations (1) and (2), the transmittance Lt may be determined, for example, by referring to the table shown in Figure 15. That is, the light transmittance of the solar cell module 10 corresponding to the light saturation point of the plant may be predetermined. In this case, the area ratio of the second groove may be determined based on the light transmittance and the area ratio of the first groove.

[0064] Furthermore, the ratio of the total area of ​​the second groove 160 to the area of ​​the power generation element 100 is, for example, the value obtained by subtracting the ratio of the total area of ​​the first groove 130 from the transmittance. For example, if the desired transmittance value of the solar cell module 10 is 60 and the total area of ​​the first groove 130 is 4%, then the ratio of the total area of ​​the second groove 160 is calculated as 60 - 4[%], resulting in 56[%].

[0065] [5. Method for manufacturing solar cell modules] Next, the manufacturing method of the solar cell module 10 will be described with reference to Figure 16. Figure 16 is a flowchart showing the manufacturing flow of the solar cell module 10.

[0066] In step S1, a first substrate 11 on which transparent electrodes 151 are placed is prepared. Next, in step S2, a solar cell layer PV is laminated on the transparent electrodes 151 of the first substrate 11. The solar cell layer PV is formed, for example, by coating and deposition. A transparent electrode 155 is further laminated on the solar cell layer PV.

[0067] In step S3, the first groove 130 is formed by laser scribing the transparent electrode 151, solar cell layer PV, and transparent electrode 155 stacked on the first substrate 11, thereby imparting transparency to the power generation element 100. Transparency can also be imparted by forming a second groove 160 by laser scribing the solar cell layer PV and transparent electrode 155 stacked on the first substrate 11.

[0068] In step S4, the sealing member 50 is formed on the peripheral edges of the outer periphery of the first substrate 11 and the second substrate 12. Furthermore, the space between the first substrate 11 and the second substrate 12 is filled with a filler material 32. In this way, the solar cell module 10 is formed.

[0069] [6. Effects, etc.] Thus, the solar cell system 1 includes a solar cell module 10 positioned above a cultivation section 9 where a predetermined plant is grown. The solar cell module 10 has a power generation element 100 provided between a first substrate 11 and a second substrate 12. The solar cell module 10 has a light transmittance based on the light saturation point of the predetermined plant.

[0070] Since the solar cell module 10 has a light transmittance based on the light saturation point of the plant, it can suppress changes in the amount of light irradiated to the plant.

[0071] Furthermore, when sunlight is irradiated onto the cultivation section 9 via the solar cell module 10, the light reception intensity of each leaf Lf of a given plant at any given time is uniform. Here, "uniform light reception intensity" means that, for each leaf Lf of a given plant, regardless of the angle of sunlight irradiation, the lower limit is the value obtained by multiplying the light reception intensity based on sunlight from the solar cell module 10 by its transmittance.

[0072] For example, the following relationship is satisfied between the light received by leaf Lf P, the incident light intensity I on solar cell module 10, and the transmittance T of solar cell module 10. P=I×T+α or P=I×T-α (5) Here, α is an influence value other than transmitted light. Note that the situation in which α is added to the light received by the leaf Lf is when the light received by the leaf Lf P is greater than the light received by the transmitted light due to reflection, diffusion, etc. This is because the light transmitted through the solar cell module 10 does not attenuate much by the time it reaches the cultivation area 9, and especially in glasshouses 2 and plastic greenhouses, there may be sunlight that irradiates the leaf Lf without passing through the solar cell module 10.

[0073] Furthermore, since the lower limit of the transmittance of the solar cell module 10 was originally set to a value close to the conditions required for solar sharing to be successful, it is desirable that it not fall below this value. Therefore, the following relationship holds true. P ≥ I × T ... (6) However, this does not apply to leaves that do not receive direct light transmitted through the solar cell module 10, depending on how the leaves grow and their position.

[0074] By doing this, it is possible to irradiate the light saturation point amount to the Lf of each plant leaf at any given time, thereby improving the efficiency of plant photosynthesis and balancing it with power generation efficiency.

[0075] The transmittance is greater than 0 and less than 100, and falls within a range of +30 to -30 relative to the light saturation point. As a result, the plant yield can be increased to more than 70% of the yield without the solar cell module 10, making it possible to operate it as an agrophotovoltaic power generation system.

[0076] (Embodiment 2) Next, the solar cell system 1A in Embodiment 2 will be described. In the solar cell system 1 in Embodiment 1, the amount of light transmitted was adjusted by the size of the area of ​​the first groove 130 and the second groove 160, but in the solar cell system 1A in Embodiment 2, the amount of light transmitted can be adjusted by changing the thickness of the solar cell layer PV.

[0077] For example, reducing the thickness of the solar cell PV layer can increase the amount of light transmitted, while increasing the thickness of the solar cell PV layer can decrease the amount of light transmitted. In particular, reducing the thickness of the i-type semiconductor layer 153 can increase the amount of light transmitted, while increasing the thickness of the i-type semiconductor layer 153 can decrease the amount of light transmitted.

[0078] Therefore, the thickness of the solar cell layer PV of the power generation element 100A in Embodiment 2 is determined based on the light saturation point of the plant. Since the light absorption rate due to the thickness of the solar cell layer PV is less than or equal to the value obtained by subtracting the transmittance value from 100, a solar cell module 10 with a desired transmittance can be manufactured by subtracting the light absorption rate due to the thickness of the solar cell layer PV from 100.

[0079] Furthermore, in the power generation element 100A of Embodiment 2, as shown in Figure 17, there is no need to form the second groove 160, so the amount of work to be removed by laser processing can be reduced.

[0080] Thus, in the solar cell system 1A of Embodiment 2, the solar cell module 10 has a light transmittance based on the light saturation point of the plant, so it is possible to suppress changes in the amount of light irradiated to the plant.

[0081] (Other embodiments) As described above, the above embodiments have been explained as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these embodiments and can be applied to embodiments that have been modified, replaced, added, or omitted as appropriate. Therefore, other embodiments will be illustrated below.

[0082] In the embodiment described above, the solar cell system 1 had solar cell modules 10 installed on the roof of the glasshouse 2, but it is not limited to this. As shown in Figure 18, the solar cell system 1B in modified example 2 may be an array type in which solar cell modules 10 are arranged front, back, left, and right. With an array type, the gaps between adjacent solar cell modules 10 are small, so the power generation efficiency can be improved. Also, as shown in Figure 19, the solar cell system 1C in modified example 3 may be a trellis type in which solar cell modules 10 are arranged with spacing in one direction.

[0083] (Summary of the embodiment) (1) The photovoltaic power generation system of the present disclosure comprises a solar cell module positioned above a cultivation area in which a predetermined plant is grown. The solar cell module has two substrates and a power generation element provided between the two substrates. The solar cell module has a light transmittance based on the light saturation point of the predetermined plant.

[0084] According to this solar power generation system, the solar cell modules have a light transmittance based on the light saturation point of plants, thus suppressing changes in the amount of light irradiated to plants.

[0085] (2) In the photovoltaic power generation system of (1), when sunlight is irradiated to the cultivation area via the solar cell module, the light reception intensity for each leaf of the predetermined plant is less than the light irradiation angle of the sunlight, and the lower limit is the value obtained by multiplying the light reception intensity of the solar cell module based on the sunlight by the transmittance.

[0086] (3) In the photovoltaic power generation system of (1) or (2), the transmittance is a value greater than 0 and less than 100, and within the range of -30 to +30 relative to the light saturation point.

[0087] (4) In any of the photovoltaic power generation systems described in (1) to (3), the power generation element comprises a plurality of solar cells arranged in series at a first pitch and in parallel at a second pitch, a first groove formed between adjacent solar cells in the series direction, and a second groove formed between adjacent solar cells in the parallel direction.

[0088] In the photovoltaic power generation system of (5)(4), each solar cell includes a first electrode layer, an electron transport layer, a power generation layer, a hole transport layer, and a second electrode layer, which are arranged between two substrates. In multiple solar cells, at least one of the electron transport layer, power generation layer, hole transport layer, and second electrode layer is arranged at a first pitch.

[0089] (6) In the photovoltaic power generation system of (4) or (5), the ratio of the total area of ​​the second groove to the area of ​​the power generation element is the value obtained by subtracting the ratio of the total area of ​​the first groove to the area of ​​the power generation element from the transmittance.

[0090] (7) In any of the photovoltaic power generation systems described in (4) through (6), the width of the second groove is shorter than the leaf blade of a given plant.

[0091] (8) In any of the photovoltaic power generation systems described in (4) through (7), the pitch of the second groove is shorter than the leaf blade of the specified plant.

[0092] (9) In any of the photovoltaic power generation systems described in (1) to (3), the power generation element comprises a solar cell including a first electrode layer, an electron transport layer, a power generation layer, a hole transport layer, and a second electrode layer, which are arranged between two substrates. The light absorption rate due to the thickness of the power generation layer is less than or equal to the value obtained by subtracting the transmittance value from 100.

[0093] In the photovoltaic power generation system of (10)(5), the power generation layer contains a perovskite compound.

[0094] In the photovoltaic power generation system of (11)(9), the power generation layer contains a perovskite compound.

[0095] (12) In any of the photovoltaic power generation systems described in (1) through (11), both substrates are made of glass. [Industrial applicability]

[0096] This disclosure is useful for photovoltaic power generation systems that also utilize sunlight for plant cultivation. [Explanation of Symbols]

[0097] 1. Solar cell system 2. Glasshouse 2a Roof 3a, 3b Bus wiring 4 controllers 5 Output section 6. Storage Battery 7. Lighting Section 8 Drive unit 9 Cultivation Department 10 solar modules 11. First circuit board 11s main surface 12 Second board 13 Central area 19 Terminal box 21, 22 Wiring 23, 24 Lead wires 32 Filling material 41 Tab lines 42 Tab lines 50 Sealing member 51, 52 Bus wiring 100, 100A power generation element 100a, 100Aa area 120 strings 130 First Groove 150 solar cells 151 Transparent electrode 152 n-type semiconductor layer 153 Type i semiconductor layer 154 p-type semiconductor layer 155 Transparent electrode 160 Second groove PV solar cell layer Pt1 First Pitch Pt2 Second Pitch

Claims

1. It is equipped with a solar panel module that is placed above the cultivation area where the specified plants are grown, The aforementioned solar cell module is Two circuit boards, It has a power generation element provided between the two substrates, The solar cell module has a light transmittance based on the light saturation point of the predetermined plant, Solar power generation system.

2. When sunlight is irradiated onto the cultivation area via the solar cell module, the light reception intensity for each leaf of the predetermined plant is less than the value obtained by multiplying the light reception intensity of the solar cell module based on the sunlight by the transmittance, regardless of the angle of sunlight irradiation. The photovoltaic power generation system according to claim 1.

3. The aforementioned transmittance is a value greater than 0 and less than 100, and falls within the range of -30 to +30 relative to the light saturation point value. The solar power generation system according to claim 2.

4. The aforementioned power generation element is Multiple solar cells arranged in series with a first pitch and in parallel with a second pitch, A first groove formed between adjacent solar cells in the series direction, A second groove formed between adjacent solar cells in the parallel direction, The photovoltaic power generation system according to claim 1.

5. Each of the aforementioned solar cells includes a first electrode layer, an electron transport layer, a power generation layer, a hole transport layer, and a second electrode layer, which are disposed between the two substrates. In multiple solar cells, at least one of the electron transport layer, power generation layer, hole transport layer, and second electrode layer is arranged at the first pitch. The solar power generation system according to claim 4.

6. The ratio of the total area of ​​the second groove to the area of ​​the power generation element is the value obtained by subtracting the ratio of the total area of ​​the first groove to the area of ​​the power generation element from the transmittance. The solar power generation system according to claim 4.

7. The width of the second groove is shorter than the leaf blade of the predetermined plant. The solar power generation system according to claim 4.

8. The pitch of the second groove is shorter than the leaf blade of the predetermined plant. The photovoltaic power generation system according to claim 7.

9. The power generation element comprises a solar cell including a first electrode layer, an electron transport layer, a power generation layer, a hole transport layer, and a second electrode layer, which are arranged between the two substrates. The light absorption rate due to the thickness of the power generation layer is less than or equal to the value obtained by subtracting the transmittance value from 100. A solar power generation system according to any one of claims 1 to 3.

10. The power generation layer contains a perovskite compound. The photovoltaic power generation system according to claim 5.

11. The power generation layer contains a perovskite compound. The photovoltaic power generation system according to claim 9.

12. Both of the aforementioned substrates are made of glass. The photovoltaic power generation system according to claim 1.

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