Reflectors for solar power generation systems

Abstract

To provide a reflector for a photovoltaic power generation system with excellent weather resistance, improving a power generation efficiency; making it possible to reduce a site area; and making it possible to increase the amount of power generation while reducing costs of construction, maintenance, etc.SOLUTION: A reflector 4 is used for a photovoltaic power generation system comprising multiple double-sided incident type photovoltaic power generation panels 2, each of which is installed at a prescribed slant angle, directing a top-side power generation surface 6 toward the sunlight incident direction through a cradle 3. The reflector also comprises: a reflective layer 14 having a light reflection surface made of a sheet material having a color with high optical reflectance for reflecting the direct light and scattered light of a sunlight toward the bottom-side power generation surface 12 of the photovoltaic power generation panel 2; and a weed-proof layer 15 made of a weed-proof sheet material. The reflective layer 14 and the weed-proof layer 15 are integrally laminated. The thickness of the reflector 4 is 1.0 mm or larger.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] This invention relates to a reflector for a solar power generation system. [Background technology]

[0002] Traditionally, solar power generation systems have included mega solar power plants, which involve arranging a large number of solar panels on the ground to generate electricity on a large scale. As shown in the following Patent Documents 1 and 2, this mega solar power plant has a large number of solar power generation panels installed on a vast site, and each solar power generation panel is arranged via a mounting frame at a predetermined angle.

[0003] Because solar power generation systems, which consist of a large number of solar panels, are installed on vast outdoor sites, they require considerable effort for maintenance. This means that tasks such as suppressing the growth of weeds from the ground beneath the solar panels are necessary to prevent a decrease in power generation efficiency. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-228736 [Patent Document 2] Japanese Patent Publication No. 2015-216766 [Patent Document 3] Japanese Patent Publication No. 2019-068795 [Overview of the project] [Problems that the invention aims to solve]

[0005] As described above, weeds growing from the ground surface can cause problems by covering the solar power generation panels as they grow, thus blocking sunlight and reducing the amount of sunlight entering the panels. Removing these weeds requires manual removal, i.e., pulling them out, or applying herbicides, which means that workers are needed, making the work a time-consuming task. Furthermore, since weeds do not easily disappear and grow back, weeding work must be done repeatedly, making it a very cumbersome maintenance task. In addition, the use of herbicides may damage the surrounding environment. To alleviate these tasks, methods such as covering the ground surface with concrete after weeding or laying weed control sheets on the ground to inhibit weed growth have been implemented, but these are also cumbersome construction methods, and cost reduction is needed.

[0006] On the other hand, installing a large number of solar power generation panels on a vast site is necessary to ensure sufficient power generation, and installing a large-scale power generation facility with an output of 1 MW (1 megawatt = 1000 kW) or more requires a single plot of land with a flat surface. Therefore, efforts are being made to achieve installation conditions that are highly efficient in terms of power generation per unit area. To improve such power generation efficiency, some systems, such as the one described in Patent Document 3 above, use reflective multi-sheets laid on the ground and solar power generation panels that also have power generation capabilities on the back side to utilize reflected light from the ground for power generation. However, while this suppresses weed growth, it only makes it more difficult for sunlight to reach the weeds, and the removal and excavation of weeds is unavoidable, resulting in maintenance costs and a desire for further improvement. In addition, since the ground-facing side of the reflective multi-sheet is made of resin film, when installed on uneven ground, the reflective surface of the sheet also becomes uneven, which can reduce reflectivity and decrease the amount of light incident on the back side of the solar power generation panel. Furthermore, there is a risk of the sheet being damaged when installed on uneven ground.

[0007] The present invention has been made in view of the above circumstances, and its object is to be used in a solar power generation system that can improve power generation efficiency, reduce the floor area, increase the power generation amount while reducing costs such as construction and maintenance, and provide a reflector for a solar power generation system. Another object is to provide a reflector for a solar power generation system having excellent weather resistance.

Means for Solving the Problems

[0008] Next, the means for solving the above problems will be described with reference to the drawings corresponding to the embodiments. The reflector 4 for a solar power generation system according to claim 1 of the present invention is a reflector used in a solar power generation system including a double-sided incident type solar power generation panel 2 installed in a plurality of numbers with the power generation surface 6 on the upper surface inclined at a predetermined angle in the sunlight incident direction via a pedestal 3, The reflector 4 has a light reflecting surface that reflects direct sunlight and scattered sunlight toward the power generation surface on the lower surface of the solar power generation panel The layer contains 7.47 wt% or more of white pigment, and is a thermoplastic containing linear low-density polyethylene and an olefin resin containing low-density polyethylene. and consists of a reflective layer made of a resin sheet material, a weed prevention layer 15 made of a weed prevention sheet material, and the reflective layer 14 and the weed prevention layer 15 are integrally laminated, After the exposure test under the following conditions, the visible light reflectance of the light reflecting surface at a wavelength of 360 to 830 nm is 73.2~82.5 %, and the infrared reflectance at a wavelength of 3.2 to 19.8 μm is 4.4~7.7% and the surface of the reflective layer 14 constituting the reflector 4 has water repellency, and the water repellency coefficient of the reflector 4 is 1.0×10 2 m / sec or less, and the thickness of the reflector 4 is 1.0 mm or more. <​​​​​​​​​(Wavelength range: 300 - 700 nm) Water spray cycle: Water injection for 18 ± 0.5 minutes, water injection stopped for 102 ± 0.5 minutes Irradiation time: 3000 hours

[0009] In this reflector for a solar power generation system, with respect to the power generation surface 12 on the lower surface of the double-sided incident type solar power generation panel 2, a reflector 4 equipped with a sheet material having a high light reflectance reflects and makes incident the direct sunlight and scattered sunlight, thereby improving the power generation efficiency. Further, the reflector 4 is provided with a weed prevention layer 15, which suppresses the growth of weeds from the ground surface, thereby reducing maintenance work and its cost. Furthermore, according to this reflector 4, even when installed on uneven ground, the reflecting surface becomes a flat or nearly flat smooth surface, so the reflectance does not decrease and the light incident on the power generation surface 12 on the lower surface of the solar power generation panel does not decrease. This reflector for solar power generation systems reflects light in the near-infrared region, from the visible light to the short-wavelength side of sunlight, and has a low reflectivity in the far-infrared region. This prevents the temperature of the solar power generation panel from rising and does not reduce power generation efficiency. In this solar power generation system reflector, the surface of the reflective layer of the reflector laid on the site is made waterproof, so that rainwater does not remain on the surface of the reflector 4 and is directed away from the reflector. As a result, the surface of the reflective layer 14 is less likely to get dirty, and the frequency of maintenance is reduced.

[0010] The reflector for a solar power generation system according to claim 2 of the present invention is the reflector for a solar power generation system according to claim 1, The aforementioned white pigment contains titanium dioxide characterized by the above.

[0011] In this reflector for a solar power generation system, The aforementioned white pigment contains titanium dioxide by this, light of a wavelength used for power generation among direct sunlight and scattered sunlight can be made to enter the lower surface power generation surface 12 as well-reflected light, and the power generation efficiency can be improved.

[0020] The reflector for a solar power generation system according to claim 3 of the present invention is the reflector for a solar power generation system according to claim 1 or 2 and is characterized in that the surface of the reflection layer has an ultraviolet deterioration prevention layer.

[0021] In this reflector for solar power generation systems, the UV degradation prevention layer prevents UV degradation of the reflective layer, that is, it prevents degradation caused by irradiation with ultraviolet light contained in sunlight, thereby extending the lifespan of the reflector and allowing for longer replacement and maintenance intervals.

[0028] Claims of the present invention 4 The reflector for the solar power generation system described is as claimed. 1 The reflector for the solar power generation system described above, The weed-suppressing layer is characterized by being composed of a thermoplastic resin and a black pigment.

[0029] In this reflector for solar power generation systems, using a black sheet for the weed control layer allows for a higher density than nonwoven fabric, effectively applying weight stress per unit volume to weeds and promoting weed death.

[0030] Claims of the present invention 5 The reflector for the solar power generation system described is as claimed. 4 The reflector for the solar power generation system described above, The weed control layer includes The thermoplastic resin is characterized by being made of an olefin-based resin.

[0031] In this reflector for solar power generation systems, the weed-preventing layer is constructed to have superior mechanical strength.

[0032] Claims of the present invention 6 The reflector for the solar power generation system described is as claimed. 5 The reflector for the solar power generation system described above, The weed control layer includes The olefin resin is characterized by comprising at least one of low-density polyethylene and linear low-density polyethylene.

[0033] In this reflector for solar power generation systems, the weed control layer can be made from an ethylene-based resin sheet that offers excellent flexibility and ease of installation. [Effects of the Invention]

[0034] According to the reflector for a photovoltaic power generation system described in claim 1 of the present invention, by reflecting both direct and scattered sunlight onto the power generation surface on the lower surface of a double-sided incident photovoltaic power generation panel using a reflector equipped with a sheet material with high light reflectivity, it is possible to improve power generation efficiency and increase the amount of power generated. Furthermore, by improving the amount of power generated, it becomes possible to reduce the number of photovoltaic power generation panels to be installed, thereby promoting a reduction in the amount of land required. Furthermore, the reflector is equipped with a weed-suppressing layer that comes into contact with the ground surface, which suppresses the growth of weeds from the ground surface. This reduces maintenance work such as weed removal and lowers associated costs. Furthermore, with this reflector, even when installed on uneven ground, the reflective surface becomes flat or a nearly flat, gently sloping surface, so the reflectivity does not decrease, and the amount of light incident on the power generation surface on the underside of the solar power generation panel does not decrease. Furthermore, by reflecting light in the near-infrared region, which is on the visible to short wavelength side of sunlight, and having a low reflectivity in the far-infrared region, it is possible to prevent the temperature of the solar power generation panel from rising, thus achieving the effect of not reducing power generation efficiency. Furthermore, by providing a water-resistant surface to the reflector, rainwater does not accumulate on the surface of the reflector but is directed away from it. This makes the surface of the reflective layer less prone to dirt buildup and reduces the frequency of maintenance.

[0035] According to the reflector for a photovoltaic power generation system described in claim 2 of the present invention, The aforementioned white pigment contains titanium dioxide This allows light of wavelengths used for power generation, from both direct and scattered sunlight, to be effectively reflected onto the lower power generation surface, thereby improving power generation efficiency.

[0040] Claims according to the present invention 3 According to the described reflector for solar power generation systems, the UV degradation prevention layer prevents UV degradation of the reflector layer, that is, it prevents degradation caused by irradiation with light in the ultraviolet range contained in sunlight, thereby extending the lifespan of the reflector and extending the replacement interval and maintenance interval.

[0044] Claims according to the present invention 4 According to the described reflector for solar power generation systems, by using a black sheet for the weed control layer, a higher density can be achieved compared to nonwoven fabric, allowing for efficient application of weight stress per unit volume to weeds and promoting weed death.

[0045] Claims according to the present invention 5 According to the described reflector for solar power generation systems, the weed control layer has a structure that provides excellent mechanical strength.

[0046] Claims according to the present invention 6 According to the described reflector for solar power generation systems, the weed control layer can be made from an ethylene-based resin sheet that offers excellent flexibility and ease of installation. [Brief explanation of the drawing]

[0047] [Figure 1] This is a schematic perspective view of a photovoltaic power generation system according to the first embodiment of the present invention. [Figure 2] This is a schematic perspective view of a photovoltaic power generation system according to a second embodiment of the present invention. [Figure 3] This is a magnified side view of a portion of a solar power generation system. [Figure 4] This is a partially enlarged schematic side view illustrating the operation of a solar power generation system. [Figure 5] This graph shows the relationship between wavelength and light reflectance, based on the results of a spectral reflectance measurement test for an example of a reflective sheet. [Modes for carrying out the invention]

[0048] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. Figure 1 is a schematic perspective view showing a photovoltaic power generation system according to an embodiment of the present invention. The photovoltaic power generation system 1 according to this embodiment mainly comprises a photovoltaic power generation panel 2, a mounting frame 3, and a reflector 4.

[0049] The solar power generation panel 2 is constructed by integrating and modularizing multiple solar cells. In this embodiment, solar cells are provided on both the front and back surfaces, resulting in a double-sided incident solar power generation panel where both surfaces are power-generating surfaces. As shown in Figure 1, multiple solar power generation panels 2 are arranged in parallel vertically and horizontally, and connected in a long horizontal direction, and placed on a mounting frame 3 (described later) to form a solar cell array 5. Multiple rows of these solar cell arrays 5 are arranged in the depth direction on a site of a desired size. These rows of solar cell arrays constitute a so-called mega solar (large-scale solar power generation), that is, a group of solar power generation panels capable of obtaining an output of at least 1 MW or more.

[0050] Each solar cell array 5 is arranged with a predetermined gap between them. This gap is set so that the upper power generation surfaces 6 of the solar power generation panels 2 of each solar cell array 5, which are installed in multiple rows, do not cast shadows on each other from direct sunlight, and so that workers can easily pass through during maintenance and other operations.

[0051] While there are various configurations for the solar power generation panel 2, suitable examples include the Swan series from JinkoSolar, the MBB bifacial PERC half-cell double glass module from JA Solar, the Duomax Twin from Trina Solar, the HiKu5 series from Canadian Solar, the LR4-72HBD series from Longi Solar, the Q.PEAK DUO from Hanwha Q CELLS, the double glass bifacial monocrystalline PERC module from Lysen Energy, and the GCL-M6 / 72GD from Golden Concord Holdings Limited (GCL). In all cases, power generation from the bottom power generation surface 12 (the back surface) increases the power generation per panel by approximately 20%.

[0052] Figure 3 is an enlarged side view of a portion of the solar power generation system. The solar cell array 5 consists of the aforementioned solar power generation panels 2 and a mounting frame 3 on which these solar cell panels 2 are placed, and is installed on the site surface 7.

[0053] The frame 3 consists of support columns 8, horizontal members 9, connecting brackets 10, etc., each of which is connected and fixed by means of bolts, welding, etc. The frame 3 is also fixed by a foundation 11 installed on the ground 7.

[0054] The mounting frame 3 is used to secure the solar power generation panels 2 with connecting brackets 10, and the power generation surface of the solar power generation panels 2 is tilted from the horizontal at, for example, about 30°. This tilt angle is determined considering conditions such as the latitude and environment of the installation site. For example, in high-latitude regions of the Northern Hemisphere such as Japan, the top power generation surface 6 is tilted towards the south and fixed to the mounting frame 3. The height of the mounting frame 3 is set so that the height from the site surface 7 to the lower edge 2a of the inclined panel 2 is 0.8m or more, ensuring sufficient space beneath the mounting frame 3. This space becomes a light-transmitting space 13 for the lower power-generating surface 12 of the solar power generation panel 2.

[0055] The reflector 4 is positioned on the site surface 7 at the bottom of the mounting frame 3, facing the power generation surface 12 on the underside of the solar power generation panel 2. The reflector 4 is in the form of a sheet and consists of a reflective layer 14 on the upper surface and a weed-preventing layer 15 on the lower surface, with each of these layers being integrated into a laminated structure.

[0056] In the first embodiment, the surface of the reflective layer 14 constituting the reflector 4 is waterproof. The reflective layer 14 is made of a sheet material with a high light reflectivity that reflects light of wavelengths used for power generation from both direct and scattered sunlight. In this embodiment, the reflective sheet has a white surface. This reflective sheet is made of a flexible material such as a resin sheet or rubber sheet with a thickness of 0.5 to 3.0 mm, preferably 1.0 mm or 1.5 mm. For example, the resin sheet material may be polyethylene resin, polyester resin, polypropylene resin, polyethylene terephthalate, vinyl chloride resin, polystyrene resin, fluororesin, nylon resin, etc. The surface is white, either as the material of the reflective sheet itself or as a white coating. This waterproof reflective sheet has a waterproofing coefficient of 1.0 × 10 -11The water permeability is less than m / sec, allowing rainwater and water droplets to be effectively guided outwards from the surface. Here, "water permeability coefficient" refers to the "water permeability coefficient" in the voluntary standards for water permeability sheets set by the Japan Water Permeability Association, but in this invention, to avoid confusion with the water permeability coefficient described later, it will be referred to as "water permeability coefficient". This water permeability coefficient is obtained by determining the water permeability in accordance with JIS Z 0208 "Method for testing moisture permeability of moisture-proof packaging materials (cup method)" and then using the calculation formula described in "6.4.8 Calculation of water permeability coefficient" of the "Water Permeability Technology and Management Manual" (published by the Japan Water Permeability Association: May 2019 edition). The above value indicates that the water permeability is low, and therefore the water permeability is high.

[0057] The surface of the reflective sheet preferably has water-repellent properties, which repel rainwater and easily guide water droplets away from the surface of the reflective sheet. Furthermore, it is preferable that the reflective sheet has functions such as chemical resistance, heat resistance, fire resistance, flame retardancy, cold resistance, radiation resistance, thermal conductivity, abrasion resistance, friction resistance, and antistatic properties. In addition, a transparent protective layer may be provided on the surface. The following are some ways to provide water repellency to the surface of the reflective sheet. For example, one method is to incorporate a water-repellent agent into the reflective sheet. Another method is to apply a surface treatment agent consisting of a water-repellent agent to the surface of the reflective sheet.

[0058] To elaborate on the fact that the reflective sheet surface is white, which has a high light reflectivity, the power generation surface of the photovoltaic panel 2 generates electricity when irradiated with sunlight. However, it is not necessary for the power generation surface to receive sunlight across the entire wavelength range, and infrared light is not required. On the other hand, infrared sunlight causes a heat generation phenomenon in the photovoltaic panel 2, and if the temperature of the power generation surface exceeds 50°C, it will reduce the power generation efficiency. Therefore, it is preferable that the surface of the reflective sheet reflects light in the near-infrared region of sunlight, from visible light to short wavelengths. For example, the surface of the reflective sheet may be white, and an infrared-removing film may be provided on its surface. This film may be a filter that removes or absorbs near-infrared and far-infrared rays in the region of 1000 nm or more, so that infrared light is not reflected to the solar power generation panel 2. Furthermore, since the reflective sheet is prone to deterioration due to ultraviolet rays contained in sunlight, it is also possible to incorporate an ultraviolet absorber into the surface layer of the reflective sheet or to apply an ultraviolet degradation prevention coating to create an ultraviolet degradation prevention layer.

[0059] Furthermore, as a reflective sheet as described above, for example, a sheet is suitable that has a light reflectance of 70% or more for wavelengths of 500 to 1000 nm in sunlight, a low light reflectance for wavelengths of 2300 nm or more, an average light reflectance of 15% or less for wavelengths of 5000 to 20000 nm, preferably an average light reflectance of 10% or less for wavelengths of 5000 to 20000 nm, and has the characteristic of not reflecting light in the bands known as short-wavelength infrared to mid-wavelength infrared, long-wavelength infrared (thermal infrared), and far-infrared. Alternatively, for example, the surface of the reflective sheet may be made white, and an infrared-removing film may be provided on its surface, preferably a filter-like film that removes or absorbs near-infrared and far-infrared in the region of 1000 nm or more, so as not to reflect light in the infrared region to the solar power generation panel 2.

[0060] As a specific example of a reflective sheet, a suitable choice is the Binon Metallobarrier SLS (product name) manufactured by Takiron CI Co., Ltd., which is made of an olefin resin consisting of a white layer with a white pigment on the surface and a black layer with a black pigment on the back. In this case, the reflective sheet itself has a light-blocking rate of about 99%, and weed control effects can also be expected.

[0061] The following are the results of spectral reflectance measurements using a Fourier transform infrared spectrophotometer (FTIR) in accordance with JIS R 1693-2:2012, using this reflective sheet (Binon Metallobarrier SLS (product name)). [Test equipment] • FTIR device (Perkin Elmer System2000 model) • Integrating sphere: (Labsphere RSA-PE-200-ID) The inside of the sphere is coated with gold. ·Integrating sphere entrance aperture: φ16mm ·Measurement part diameter: φ24mm [Measurement conditions] ·Measurement area: 370~7800cm -1 (Effective range 400~6000cm) -1 ) • Total number of times: 200 ·Light source: MIR • PixelMIR-TGS ·Resolution: 16cm -1 Beam splitter: optimized KBr The optical path from the light source to the detector was filled with N2 gas and purged. [conditions] The reflectance spectrum was measured at room temperature. The measurements were performed using an integrating sphere. These measurements conform to JIS R 1693-2:2012. [Measurement results] Figure 5 shows the spectral reflectance spectrum at room temperature, graphed as the relationship between wavelength and light reflectance. As shown in Figure 5, the average light reflectance at wavelengths of 5000 to 20000 nm is low, at less than 10%, indicating that light in the bands known as short-wavelength infrared, mid-wavelength infrared, long-wavelength infrared (thermal infrared), and far-infrared is not reflected.

[0062] The weed control layer 15 consists of a highly light-blocking weed control sheet, such as a nonwoven fabric. This weed control layer 15, a weed control sheet, is a sheet material that promotes weed death by inflicting environmental stress on weeds, such as heat stress, weight stress, and stress due to photosynthesis inhibition. Such weed control sheets may be made from specific materials such as long-fiber nonwoven fabrics like polyester fibers, polyethylene fibers, polyamide fibers, aramid fibers, acrylic fibers, carbon fibers, polyurethane fibers, cotton yarn, wool yarn, silk yarn, hemp, or sheep's wool, and may be formed using these materials individually or in combination of two or more types. In addition, resin sheets that do not have water permeability may be used for the weed control sheets. When installing the reflector 4 on uneven ground, it is preferable to use a highly cushioned woven or nonwoven fabric to prevent damage to the reflective layer 14 due to the unevenness of the ground.

[0063] As the weed control sheet as described above, for example, it is a non-woven fabric, and the light transmittance at each wavelength measured every 1 nm in the range of 400 nm or more and 700 nm or less is 10% or less, the puncture resistance is 10 to 30 N, and the basis weight is 100 to 400 g / m 2 is preferably used. As the resin sheet having no water permeability, it is made of a flexible material such as a resin sheet with a thickness of 0.5 to 3.0 mm, preferably 1.0 mm or 1.5 mm, or a rubber sheet. For example, as the material of the resin sheet, it is made of polyethylene resin, polyester resin, polypropylene resin, polyethylene terephthalate, vinyl chloride resin, polystyrene resin, fluororesin, nylon resin, etc.

[0064] As a specific weed control sheet, for example, the following three can be mentioned as non-woven fabrics. <Example 1> For example, the mass per unit area is 150 to 260 g / m 2 , the thickness is 0.4 to 0.6 mm, the density is 0.4 g / cm 3 , the tensile strength in the longitudinal direction is 290 to 790 N / 5 cm, the tensile strength in the transverse direction is 190 to 500 N / 5 cm, the elongation in the longitudinal direction is 15 to 30%, the elongation in the transverse direction is 15 to 25%, the tear strength in the longitudinal direction is 80 N, the tear strength in the transverse direction is 100 N, and the water permeability coefficient is 8.0×10 -5 ~1.0×10 -4 m / sec, the puncture resistance is between 17 and 20 N, and the light-shielding rate is 95%. The Axtar Mantle weed control sheet (trade name) manufactured by Toray Industries, Inc. having such characteristic data is preferably used. <Example 2> In addition, as this weed control sheet, it is generally a sheet with a light-shielding rate of 95% or more, which is the ability to block sunlight. For example, the weight is about 310 g / m 2 , the thickness at 0.7 kPa pressure is about 3.8 mm, the thickness at 2 kPa pressure is about 3.5 mm, the tensile strength in the longitudinal direction is about 1200 N / 5 cm, the tensile strength in the weft direction is about 920 N / 5 cm, the elongation rate in the longitudinal direction is about 70%, the elongation rate in the transverse direction is about 80%, the tear strength in the longitudinal direction is about 250 N, the tear strength in the transverse direction is about 240 N, and the water permeability coefficient at a water temperature of 15°C is -3Toyobo Co., Ltd.'s 9321N (trade name), which is made of a nonwoven fabric with a density of m / sec and a bursting strength of approximately 3200 kPa, is preferably used. <Example 3> Weight: 2 kg / m 2 In addition, it is preferable to have a weed control sheet that imparts weight stress to weeds, has a light transmittance of 10% or less at each wavelength measured at 1 nm intervals in the wavelength range of 400 nm to 800 nm, absorbs sunlight and suppresses photosynthesis of weeds beneath the sheet, and absorbs sunlight and raises the temperature of the weed control sheet itself, thereby inflicting heat stress on the weeds beneath the sheet.

[0065] Then, the reflective sheet, which is the reflective layer 14, is placed on the surface, and the weed-proof sheet, which is the weed-proof layer 15, is placed on the back surface, and these are integrated to obtain a sheet-like reflector 4 as a laminated structure. The reflective sheet and the weed control sheet can be integrated in various ways, such as by co-extruding the two sheets together in a two-layer structure using an extrusion molding device to obtain the reflector 4, or by laminating the reflective sheet and the weed control sheet together using a heat laminating device. Furthermore, the reflective sheet and the weed control sheet can be heat-pressed together using a heat press device, or the reflective sheet and the weed control sheet can be bonded together using an adhesive, either across the entire surface, in a dotted or linear pattern, to form the reflector 4.

[0066] These sheet-like reflectors 4 are formed, for example, to a width of 1.0 to 2.5 m and a length of 10 to 100 m, and are manufactured, stored, and transported in a rolled-up state. When the reflectors 4 are laid, they are unrolled from their rolled-up state, spread out on the site surface 7, and multiple reflectors are placed in parallel in the width direction, connected to each other and fixed in place, so as to cover the site surface 7 without any gaps.

[0067] Next, a second embodiment of the present invention will be described with reference to Figure 2. Figure 2 is a schematic perspective view of a photovoltaic power generation system according to a second embodiment of the present invention. In the second embodiment, the solar power generation panel 2 and the mounting frame 3 can be the same as those in the first embodiment.

[0068] In the second embodiment, the reflective layer 14 constituting the reflector 4 is permeable to water. The permeable nature of the reflective layer 14 allows rainwater to quickly penetrate the ground surface. Such a permeable reflective sheet uses a structure in which numerous perforations 16 are formed through a woven or non-woven fabric, or a water-impermeable resin or rubber sheet. The formation of the perforations 16 gives the reflective sheet a structure that is permeable in the thickness direction. The perforations 16 are through holes with an inner diameter that allows for good water permeability, and are formed in part or throughout the sheet.

[0069] The reflective layer 14 consists of a sheet material with a high light reflectivity that reflects light of wavelengths used for power generation from both direct and scattered sunlight. Specific nonwoven fabric materials include long-fiber nonwoven fabrics such as polyester fibers, as well as polyethylene fibers, polyamide fibers, aramid fibers, acrylic fibers, carbon fibers, polyurethane fibers, cotton yarn, wool yarn, silk yarn, hemp, and sheep's wool. These materials are used individually or in combination of two or more types. Furthermore, the light transmittance at each wavelength measured at 1 nm intervals in the range of 400 nm to 700 nm is 10% or less, the puncture resistance is 10 to 30 N, and the basis weight is 100 to 400 g / m². 2 Those that are considered to be desirable are preferred. The waterproof sheet having the perforated portion 16 described above is made of a flexible material such as a resin sheet or rubber sheet with a thickness of 0.5 to 3.0 mm, preferably 1.0 mm or 1.5 mm. For example, the material of the resin sheet may be polyethylene resin, polyester resin, polypropylene resin, polyethylene terephthalate, vinyl chloride resin, polystyrene resin, fluororesin, nylon resin, etc.

[0070] For the weed control layer 15, it is preferable to use a weed control sheet with high light-blocking properties. For example, nonwoven fabric can be used. Specific materials include long-fiber nonwoven fabrics such as polyester fibers, polyethylene fibers, polyamide fibers, aramid fibers, acrylic fibers, carbon fibers, polyurethane fibers, cotton yarn, wool yarn, silk yarn, hemp, and sheep's wool. These materials are used individually or in combination of two or more types. In addition to nonwoven fabrics, embossed three-dimensional structured sheets and nets, or other three-dimensional mesh-like materials, can also be used as drainage core materials, integrated with nonwoven fabrics. To obtain sufficient weed control, it is preferable that at least one layer constituting the weed control layer be made of a dark color such as black for light blocking. However, if the light-blocking properties of the reflective layer are sufficient, the weed control sheet does not need to have light-blocking properties.

[0071] Specific examples of weed control sheets include the following three types of nonwoven fabrics: <Example 1> For example, the mass per unit area is 150-260 g / m² 2 Thickness 0.4~0.6mm, density 0.4g / cm³ 3 Tensile strength: longitudinal 290-790 N / 5cm, transverse 190-500 N / 5cm, elongation: longitudinal 15-30%, transverse 15-25%, tear strength: longitudinal 80 N, transverse 100 N, permeability coefficient: 8.0 × 10 -5 ~1.0×10 -4 Toray Industries, Inc.'s Akstar Mantle weed control sheet (product name), which has characteristic data of m / sec, puncture resistance of 17-20N, and light shielding rate of 95%, is preferably used. <Example 2> Furthermore, this weed control sheet is generally considered to have a light-blocking rate of 95% or more, which is its ability to block sunlight. For example, it weighs approximately 310g / m². 2 Thickness at 0.7kPa pressure: approximately 3.8mm, Thickness at 2kPa pressure: approximately 3.5mm, Tensile strength in the longitudinal direction: approximately 1200N / 5cm, Tensile strength in the weft direction: approximately 920N / 5cm, Elongation in the longitudinal direction: approximately 70%, Elongation in the transverse direction: approximately 80%, Tear strength in the longitudinal direction: approximately 250N, Tear strength in the transverse direction: approximately 240N, Permeability coefficient at a water temperature of 15℃: 4.4×10 -3Toyobo Co., Ltd.'s 9321N (trade name), which is made of a nonwoven fabric with a density of m / sec and a bursting strength of approximately 3200 kPa, is preferably used. <Example 3> Weight: 2 kg / m 2 In addition, it is preferable to have a weed control sheet that imparts weight stress to weeds, has a light transmittance of 10% or less at each wavelength measured at 1 nm intervals in the wavelength range of 400 nm to 800 nm, absorbs sunlight and suppresses photosynthesis of weeds beneath the sheet, and absorbs sunlight and raises the temperature of the weed control sheet itself, thereby inflicting heat stress on the weeds beneath the sheet.

[0072] Then, the reflective sheet, which is the reflective layer 14, is placed on the surface, and the weed-proof sheet, which is the weed-proof layer 15, is placed on the back surface, and these are integrated to obtain a sheet-like reflector 4 as a laminated structure. The reflective sheet and the weed control sheet may be integrated by methods such as laminating the reflective sheet and the weed control sheet together using a thermal laminating device, heat-pressing the reflective sheet and the weed control sheet together using a thermal press device, bonding the reflective sheet and the weed control sheet together using an adhesive to bond the entire surface, bond them in a dotted or linear pattern, or integrating them using a needle punch or the like to form the reflector 4.

[0073] These sheet-like reflectors 4 are formed, for example, to a width of 1.0 to 2.5 m and a length of 10 to 100 m, and are manufactured, stored, and transported in a rolled-up state. When the reflectors 4 are laid, they are unrolled from their rolled-up state, spread out on the site surface 7, and multiple reflectors are placed in parallel in the width direction, connected to each other and fixed in place, so as to cover the site surface 7 without any gaps.

[0074] In this embodiment, the reflector 4 is required to have a certain degree of water permeability as a whole. The water permeability from the front surface to the back surface of the reflector 4 can be expressed as a water permeability coefficient, which is 1.0 × 10⁻⁶. -5 The permeability coefficient is estimated to be ~1.0 m / sec, which effectively guides rainwater to the underside of the sheet. Furthermore, the permeability coefficient is 5.0 × 10 -5A permeability coefficient of ~1.0 m / sec is preferable. If the permeability coefficient is above the lower limit, the effect of directing rainwater to the underside of the sheet is enhanced. Furthermore, if the permeability coefficient is below the upper limit, the weight stress of the reflector is sufficiently exerted, resulting in good weed control and also providing cushioning against uneven ground. This permeability coefficient can be measured using a method compliant with JIS A 1218 "Method for testing the permeability of soil".

[0075] The reflector 4 can be made of a sheet material with excellent water permeability and chemical resistance, such as Geoflow (product name) manufactured by Daipla Co., Ltd., which is integrally constructed in layers with a black embossed three-dimensional structured sheet as the drainage core and a long-fiber spunbond nonwoven fabric as the protective material. Alternatively, a sheet made by sandwiching a three-dimensional mesh structure such as a net between two layers of nonwoven fabric may be used as the base material.

[0076] Next, a third embodiment of the present invention will be described. In this third embodiment, components equivalent to those shown in the first embodiment described above are denoted by the same reference numerals, and will be described with reference to Figure 1. In this third embodiment, similar to the first embodiment described above, the reflector 4 is positioned on the site surface 7 at the bottom of the mounting frame 3, facing the power generation surface 12 on the underside of the solar power generation panel 2. The reflector 4 is in the form of a sheet and consists of a reflective layer 14 on the upper surface and a weed-preventing layer 15 on the lower surface, with each of these layers being integrated into a laminated structure.

[0077] The reflective layer 14 is made of a material with high light reflectivity, such as white, that reflects light of wavelengths used for power generation from both direct and scattered sunlight, and is a reflective sheet made of a flexible material such as a resin sheet or a rubber sheet. Furthermore, the weed control layer 15 is a weed control sheet that has water-blocking and light-blocking properties, is made of a black material, for example, and is composed of a flexible material such as a resin sheet or a rubber sheet. These reflective sheets and weed control sheets are then laminated together to form a single sheet material that constitutes the reflector 4.

[0078] The reflector 4 has a thickness of 1.0 to 2.0 mm, preferably 1.0 to 1.3 mm, and of that thickness, the thickness of the reflective layer 14 is preferably about 0.4 mm. In this third embodiment as well, the surface of the reflective layer 14 constituting the reflector 4 has a water-impermeable structure, and the water-impermeable coefficient is 1.0 × 10 -11 The flow rate is set to less than m / sec, allowing for effective guidance of rainwater and water droplets from the surface to the outside. In addition, both the reflective layer 14 and the weed-suppressing layer 15 have light-blocking properties, making it possible to achieve weed control.

[0079] The resin material constituting the reflective layer 14 in this third embodiment is a mixture of a thermoplastic resin, an olefin resin, and a white pigment in predetermined weight percentages. Examples of thermoplastic resins include olefin resins, polyvinyl chloride resins, polyester resins, rubber, thermoplastic elastomers, polystyrene resins, fluororesins, and nylon resins. Preferably, the resin is an olefin resin, and more preferably, low-density polyethylene or linear low-density polyethylene. Examples of olefin resins include ethylene resins such as low-density polyethylene, linear low-density polyethylene using a Ziegler catalyst, and linear low-density polyethylene using a metallocene catalyst, as well as polypropylene resins such as ethylene-vinyl acetate copolymers, homopolypropylene, and random propylene copolymers. It is particularly preferable to use at least one type of linear low-density polyethylene using a metallocene catalyst. Examples of white pigments include titanium dioxide, zirconium oxide, calcium carbonate, calcium sulfate, zinc oxide, barium sulfate, barium carbonate, silica, alumina, kaolin, clay, talc, white clay, aluminum hydroxide, magnesium carbonate, and white hollow resin emulsion, with titanium dioxide being preferred. In addition to the resin and pigment mentioned above, this reflective layer 14 also contains weather-resistant agents, such as ultraviolet absorbers and light stabilizers.

[0080] The resin material constituting the weed control layer 15 is a mixture of thermoplastic resin, olefin resin, and black pigment in predetermined weight percentages. Thermoplastic resins and olefin-based resins are considered to be equivalent to the resin materials constituting the reflective layer 14. The black pigments include carbon blacks such as furnace black, lamp black, acetylene black, and channel black; metals such as copper oxide and iron oxide; and organic pigments such as aniline black. Carbon blacks are preferred.

[0081] Then, a reflective sheet, which will serve as the reflective layer 14, is placed on the surface, and a weed-proof sheet, which will serve as the weed-proof layer 15, is placed on the back surface, and these are integrated to obtain a sheet-like reflector 4 as a laminated structure. The integrated reflector 4 is a sheet material with a white surface and a black back surface. The reflective sheet and the weed control sheet can be integrated in various ways, such as by co-extruding the two sheets together in a two-layer structure using an extrusion molding device to obtain the reflector 4, or by laminating the reflective sheet and the weed control sheet together using a heat laminating device. Furthermore, the reflective sheet and the weed control sheet can be heat-pressed together using a heat press device, or the reflective sheet and the weed control sheet can be bonded together using an adhesive, either across the entire surface, in a dotted or linear pattern, to form the reflector 4.

[0082] These sheet-like reflectors 4 are formed, for example, to a width of 1.0 to 2.5 m and a length of 10 to 100 m, and are manufactured, stored, and transported in a rolled-up state. When the reflectors 4 are laid, they are unrolled from their rolled-up state, spread out on the site surface 7, and multiple reflectors are placed in parallel in the width direction, connected to each other and fixed in place, so as to cover the site surface 7 without any gaps.

[0083] Alternatively, the weed control layer 15 may be configured by laminating nonwoven fabric, similar to the first embodiment. In that case, the weight would be approximately 310 g / m². 2Thickness at 0.7kPa pressure: approximately 3.8mm, Thickness at 2kPa pressure: approximately 3.5mm, Tensile strength in the longitudinal direction: approximately 1200N / 5cm, Tensile strength in the weft direction: approximately 920N / 5cm, Elongation in the longitudinal direction: approximately 70%, Elongation in the transverse direction: approximately 80%, Tear strength in the longitudinal direction: approximately 250N, Tear strength in the transverse direction: approximately 240N, Permeability coefficient at a water temperature of 15℃: 4.4×10 -3 A nonwoven fabric with a density of m / sec and a bursting strength of approximately 3200 kPa is preferably used. When a weed control layer is constructed from this nonwoven fabric, similar to the first embodiment described above, the reflective layer 14 is placed on the surface and the nonwoven fabric on the back surface, and they are bonded together using methods such as hot pressing, hot embossing, hot melt adhesive, ultrasonic bonding, and high-frequency bonding to obtain a sheet-like reflector 4 as a laminated structure.

[0084] The third embodiment, a reflector which is a single sheet material in which a reflective sheet and a weed control sheet are laminated and integrated, preferably has the following physical properties.

[0085] The reflector preferably has a tear strength of 60N to 300N, more preferably 70N to 250N, and even more preferably 90N to 200N. Setting the tear strength above the lower limit makes it possible to obtain a reflector that is resistant to tearing by impact. Setting the tear strength below the upper limit makes the reflector flexible, allowing the reflective surface to be flat or nearly flat even when installed on uneven ground.

[0086] As described above, the reflectors are used as a welded joint by overlapping their ends in the width direction, and it is preferable that the shear strength of the joint between the reflectors be between 70 N / cm and 400 N / cm. It is even more preferable that it be between 100 N / cm and 300 N / cm. By setting the shear strength of the joint above the lower limit, the separation of the sheets from the overlapping portion during construction is suppressed. Furthermore, by setting the shear strength of the joint below the upper limit, the overlapping portion has flexibility, and even when installed on uneven ground, the reflective surface can be flat or a gently sloping surface that is close to flat.

[0087] The reflector preferably has a tensile strength of 140 N / cm to 1000 N / cm, and more preferably 200 N / cm to 800 N / cm. By setting the tensile strength above the lower limit, the reflector has sufficient strength and excellent workability. Furthermore, by setting the tensile strength below the upper limit, the reflector has flexibility, and even when installed on uneven ground, the reflective surface can be flat or a gently sloping surface that is close to flat. Furthermore, it is preferable that the tensile strength of this reflector after long-term use, i.e., after long-term weathering, be between 100 N / cm and 1000 N / cm, and more preferably between 200 N / cm and 800 N / cm. By keeping the tensile strength after long-term weathering within the above range, the reflector will have sufficient weather resistance, maintaining a balance between strength and flexibility over a long period, and reducing the frequency of replacement.

[0088] The reflector preferably has an elongation of 300% to 1000% at tensile fracture, more preferably 400% to 900%, and even more preferably 600% to 800%. By setting the elongation at tensile fracture above the lower limit, the reflector has flexibility, and even when installed on uneven ground, the reflective surface can be flat or a nearly flat, smooth surface. Furthermore, by setting the tensile strength below the upper limit, the reflector has sufficient strength and excellent workability. Furthermore, it is preferable that the elongation of the reflector at tensile fracture after long-term use, i.e., after long-term weathering, be between 250% and 1000%, more preferably between 400% and 900%, and even more preferably between 500% and 800%. By keeping the elongation at tensile fracture after long-term weathering within the above range, the reflector will have sufficient weather resistance, maintaining a balance between strength and flexibility over a long period, and reducing the frequency of replacement.

[0089] The reflector preferably has a visible light reflectance of 55% or more after long-term use, i.e., after long-term weathering, more preferably 65% ​​or more, and even more preferably 70% or more. By ensuring that the visible light reflectance after long-term weathering is equal to or higher than the above values, the reflector has sufficient weather resistance, allowing reflected light to be efficiently incident on the power generation surface on the underside of the solar power generation panel over a long period of time, thereby maintaining power generation efficiency.

[0090] The reflector preferably has an infrared reflectance of 1% to 15% before and after use, i.e., before and after long-term weathering, and more preferably 3% to 10%. By keeping the infrared reflectance before and after long-term weathering within the above range, it is possible to suppress the heat generation of the solar power generation panel due to light of infrared wavelengths and prevent a decrease in power generation efficiency.

[0091] The following describes an example of the third embodiment. In the examples described below, the compounding agents constituting the reflective layer 14 and the weed-suppressing layer 15 will be abbreviated as follows: thermoplastic resin will be abbreviated as PE1, olefin resin as PE2, white pigment as W-MB, black pigment as B-MB, and weather-resistant agent as UV-MB.

[0092] [Combination drug] The formulations used in the examples are as follows: PE1 = Metallocene linear low-density polyethylene with a melting point of 98°C, MFR of 2.0 g / 10 min (JIS K 7210-1, temperature 190°C, load 2.16 kg), and density of 0.908 g / cm³. PE2 = Melting point: 111℃, MFR: 0.35g / 10min (JIS K 7210-1, temperature 190℃, load 2.16kg), Density: 0.922g / cm³ 3 For high-pressure low-density polyethylene, the basic physical properties are: MFR of 0.35 g / 10 min (JIS K 7210-1, temperature 190°C, load 2.16 kg), and density of 922 kg / m³. 3 In terms of mechanical properties, it has a tensile fracture stress of 20 MPa, a tensile fracture elongation of 650%, and a tensile impact strength of 470 kJ / m². 2It has a bending stiffness of 225 MPa, a durometer hardness of 55 D, an environmental stress crack resistance of 9 Hr, and thermal properties such as a Vicat softening temperature of 97°C and a melting temperature (DSC) of 111°C, possessing the characteristics of being additive-free and high-strength. ·W-MB=Density: 2.5g / cm 3 Polyethylene masterbatch containing 83 wt% titanium dioxide UV-MB = Melting point: 110℃, Density: 0.995 g / cm³ 3 Polyethylene masterbatch containing 20 wt% hindered amine-based light stabilizer (dimethyl succinate, 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl-4-piperidine polycondensate). • B-MB = Low-density polyethylene masterbatch containing 40 wt% carbon black.

[0093] [Manufacturing Procedure] <Example 1> For the reflective layer 14, 59% by weight of PE1, 27% by weight of PE2, 9% by weight of W-MB, and 5% by weight of UV-MB were mixed. For the weed control layer 15, 75% by weight of PE1, 19% by weight of PE2, and 6% by weight of B-MB were mixed. Each layer was fed into a separate extruder, and a reflector with a total thickness of 1.14 mm was manufactured by co-extrusion, with the reflective layer 14 being 0.40 mm thick and the weed control layer 15 being 0.74 mm thick. <Example 2> Using the same procedure as described above, a reflector with a total thickness of 1.14 mm was manufactured, with a reflective layer 14 of 0.40 mm and a weed-suppressing layer 15 of 0.74 mm, using PE1 at 45% by weight, PE2 at 36% by weight, W-MB at 9% by weight, and UV-MB at 10% by weight. <Example 3> Following the same procedure as described above, 73% by weight of PE1, 18% by weight of PE2, and 9% by weight of W-MB were mixed as the reflective layer 14, and UV-MB was not added. In addition, 74% by weight of PE1, 18% by weight of PE2, and 8% by weight of B-MB were mixed as the weed control layer 15. A reflector with a total thickness of 1.5 mm was manufactured, with the reflective layer 14 being 0.31 mm and the weed control layer 15 being 1.19 mm. The formulations for each of these examples are shown in Table 1.

[0094] [Table 1]

[0095] [evaluation] The reflectors of the three embodiments manufactured using the above manufacturing procedure were evaluated according to the following criteria. The results are shown in Table 2. <Test Item 1: Tear Strength> Using the reflectors of each embodiment, the tear strength was measured in accordance with "6.6 Tear Test" described in "6. Test Methods for Synthetic Rubber and Rigid Resin Waterproofing Sheets" of the "Waterproofing Technology and Construction Management Manual" (published by the Japan Waterproofing Association: May 2019 edition).

[0096] <Test Item 2: Shear Strength of the Joint Between Sheets> Two reflectors were prepared for each embodiment. The ends of these two reflectors were overlapped with a 120 mm overlap width, and a welded joint was obtained by applying 500°C hot air with a roll (having two 15 mm x 2 rows of pressing sections) using a Leister Twinny automatic welding machine. The joint was then cooled to room temperature. At the overlap position, the strip-shaped samples obtained for each embodiment were cut in the overlap direction with the overlap centered on the overlap, with a length of 250 mm and a width of 25 mm. The maximum load at break at a tensile speed of 200 mm / min was measured. The tensile strength was calculated using the following formula and was used as the shear strength of the joint between the sheets. Tensile strength (N / cm) = Maximum load (N) ÷ Width of sample piece (cm)

[0097] <Test item 3: Tensile strength; Test item 4: Elongation at tensile fracture> Using the reflectors of each embodiment, the tensile strength and elongation at tensile fracture were measured in accordance with "6.5 Tensile Test" described in "6. Test Methods for Synthetic Rubber and Rigid Resin Waterproofing Sheets" of the "Waterproofing Technology and Construction Management Manual" (published by the Japan Waterproofing Association: May 2019 edition). Samples were taken before and after the exposure test (long-term weather resistance test), and measurements were taken at each stage. The exposure test was conducted as follows: Exposure Test: The test was conducted using a Sunshine Weather Meter (model number: Sunshine Weather Meter S80BBR) manufactured by Suga Test Instruments Co., Ltd., in accordance with JIS A 1415-1999 and JIS K 7350-4-1996, under the following conditions. • Test conditions Black panel temperature: 63±3℃ Relative humidity: 50±5% Irradiance on the sample surface: 255±10%w / m 2 (wavelength range 300~700nm) Water spray cycle: Water spraying 18±0.5 minutes, water spraying stopped 102±0.5 minutes Irradiation time: 3000 hours

[0098] <Test Item 5: Visible Light (360-830nm) Reflectance> For each example, the reflector was subjected to the above exposure test, and the sample obtained was cut into 20 x 20 mm pieces. Using a Hitachi High-Tech Science spectrophotometer (UH4150) and an integrating sphere, the total reflectance of the reflective layer 14 in the wavelength range of 190 to 2500 nm was measured. Using aluminum oxide (Al2O3 white plate) as the standard sample, the total reflectance in the wavelength range of 360 to 830 nm was averaged and this was taken as the visible light reflectance. The measurement was performed with N=3. (Equipment used for visible light reflectance measurement) • Uses a φ60mm integrating sphere, with Spectralon coating on the inside. Wavelength range: 190~2500nm • Scan speed: 600nm / min • Slit width: 5nm • Sampling interval: 5nm • Measurement environment: Room temperature (25°C), in the atmosphere • Equipment used: Hitachi spectrophotometer: UH4150 (manufactured by Hitachi High-Tech Science)

[0099] <Test Item 6: Infrared (3.2~19.8μm) Reflectance> The reflectors from each example were cut into 20 x 20 mm pieces, and the resulting samples were used to measure the specular reflectance of the reflective layer in the wavelength range of 1.3 to 20.0 μm. This was done by measuring the relative reflectance with a gold mirror as the standard using a PerkinElmer Japan Fourier transform infrared spectrometer (Spotlight400). The specular reflectance in the infrared region of 3.2 to 19.8 μm was averaged and defined as the infrared reflectance. Measurements were performed with N=3. Samples were taken before and after the exposure test, and measurements were taken at each stage. (Devices using infrared reflectivity) • Relative reflectance measurement (specular reflectance measurement) using a gold mirror as the standard. ·Incidence angle: 23 degrees • Number of scans: 64 Wavelength range: 1.3~20.0 μm (7800~500 cm) -1 ) ·Light source: MIR • Detector: MCT • Beam splitter: OptKBr • Sampling interval: 2cm -1 • Measurement environment: Room temperature (20°C), in the atmosphere • Equipment used: FT-IR Spotlight400 (manufactured by PerkinElmer)

[0100] <Test Item 7: Appearance of the Reflective Layer> The reflectors of each embodiment were used as samples subjected to the above exposure test, and the reflective layer 14 was observed with a microscope at a magnification of 50x to evaluate the degree of crack formation and delamination. ◎: No cracks observed. ○: Cracks may occur, but delamination of the reflective layer will not occur. ×: Numerous cracks occur, and the reflective layer peels off.

[0101] Table 2 shows the evaluation results for each reflector in each embodiment.

[0102] [Table 2]

[0103] The results after exposure show that, compared to Example 3, which does not contain the weather-resistant agent (UV-MB), the tensile strength, elongation at tensile fracture, visible light reflectance, and infrared reflectance of the reflectors in Examples 1 and 2, which contain the weather-resistant agent, did not decrease, indicating superior weather resistance. Furthermore, when examining the accelerated degradation of visible light reflectance after 3000 hours using magnified photographs, crack formation was observed on the surface of Example 3, but no peeling of the reflective layer 14 occurred, indicating that all reflectors are suitable for use. On the other hand, no significant cracks appeared in Examples 1 and 2, indicating that the inclusion of a weather-resistant agent suppressed deterioration and prevented a decrease in light reflectivity. In other words, the results showed that it is suitable as a reflector 4 for use in a solar power generation system.

[0104] In the above-described example of the reflector configuration, the surface of the reflective sheet constituting the surface reflective layer was described as being white. However, a metal layer may be formed on the surface of the sheet material that makes up this reflective sheet, which has a high light reflectivity that reflects both direct and scattered sunlight. This reflective sheet with a metal layer will have a metallic luster color on its surface due to the metal layer.

[0105] For example, it may be constructed as a reflective sheet with metal foil, such as aluminum foil, formed on its surface. In this reflective sheet with metal foil, the base material is, for example, the resin sheet described above, and a metal foil with a thickness of 0.5 to 1.0 mm is formed on one surface of this resin sheet, which is the base material. Furthermore, when using metal foil, it will totally reflect sunlight, and as mentioned above, it will also reflect light in the infrared region, requiring heat countermeasures. For this reason, it is preferable to apply a matte coating to prevent gloss, i.e., specular reflection like a mirror, or to form a rough surface such as a textured surface, or to provide a filter or coating that removes or absorbs infrared rays as described above.

[0106] In addition to metal foil, a metal coating may be formed on a resin sheet, and a reflective surface may be formed by means of vapor deposition, painting, plating, etc. Furthermore, in addition to the aluminum mentioned above, at least one light-reflecting agent selected from powders such as titanium oxide, alumina, talc, calcium carbonate, zinc oxide, silica, mica powder, glass powder, nickel powder, and aluminum powder may be formed in a film, resulting in a color ranging from silver to near-white. Furthermore, a transparent protective film may be formed on the surface of the metal layer or the like by coating. This protective film may be made of, for example, a resin material such as polyethylene resin, and may be a coating film, which is a preferable configuration for providing water repellency and stain resistance.

[0107] Next, the installation procedure for the solar power generation system 1 described above will be explained. The procedure described below is a so-called renovation procedure in which an existing conventional solar power generation system is installed, and it is replaced with the solar power generation system 1 of the present invention, while reusing the site and mounting structure.

[0108] First, weeding will be carried out on the site. Since weeds may grow under the solar power generation panels and under the mounting frames, these will be removed by mowing or other means. Next, remove the weed roots. Since weeds can regrow from their roots, you should remove as many roots as possible from the soil. You may also apply herbicide at this stage.

[0109] Next, the reflector 4 is laid under the mounting frame 3. If the foundation 11 constituting the frame 3 is buried underground, the sheet-like reflector 4 is cut out to correspond to the portion of the foundation 11 and laid on the site surface 7 while avoiding the foundation 11. At this time, the reflector 4 is laid with the weed-suppressing layer 15 facing downwards and the reflector layer 14 facing upwards, covering the site surface 7 as closely as possible. The reflector 4 is also laid to a width of approximately 2m beyond the area where the frame 3 is installed and its outermost perimeter. The reflector 4 is fixed to the ground by passing pin-shaped fasteners 17 through it at predetermined intervals. If the reflector 4 is in a rolled state as described above, it is laid while being rolled up, and fixed by adhesive or welding so that they are joined together in the width direction.

[0110] Next, the existing solar panels will be removed. The existing solar panels, which are connected to and fixed to mounting frame 3, will be removed from mounting frame 3 and completely taken away. At this time, any electrically connected parts will also be disconnected.

[0111] Next, the double-sided photovoltaic panels 2, which are the photovoltaic panels of this embodiment, are installed. Since the mounting frame 3 has already been assembled, the new photovoltaic panels 2 are placed on the mounting frame 3 and connected and fixed in order. At this time, if it is necessary to change the tilt angle, the angle is adjusted and then fixed. After that, the electrical connections for each solar power generation panel 2 are made, and the project is completed.

[0112] Next, I will explain the function of the above-described configuration. In the photovoltaic power generation system 1 according to this embodiment, it is possible to increase the amount of power generated by replacing existing single-sided photovoltaic power generation panels with double-sided incident power generation panels 2 and by laying reflectors 4 on the site surface 7 to reflect direct sunlight and scattered light.

[0113] In other words, if the solar panels in an existing solar power generation system have a single-sided power generation surface and generate 250W per panel, 4000 panels are needed to obtain 1000kW (1MW). However, in this embodiment, if the double-sided incident solar power generation panels 2 generate 320W per panel, then by installing the same 4000 panels, a power generation of 1280kW can be obtained, which is a 1.28-fold increase in power generation when compared at rated output.

[0114] Therefore, in order to obtain a power generation amount of 1000kW, the same as before the replacement, in the case of the solar power generation system 1 in this embodiment, it is possible to obtain this amount with 3125 solar power generation panels 2. In other words, since the size of each solar power generation panel 2 is almost the same, it is possible to reduce the total area of ​​the entire solar power generation panel 2 by approximately 22%. In other words, during reconstruction, it becomes possible to reduce the installation area and the number of solar power generation panels 2 while maintaining the same power generation capacity as before, making it possible to construct a solar power generation system 1 that can achieve a similar amount of power generation while reducing the size of the previous site.

[0115] The conversion efficiency of a solar power generation panel is expressed as the percentage of solar energy that it can actually convert into electrical energy. For example, an existing single-sided solar power generation panel, the SANIX SRM296P-72N (hereinafter referred to as Panel A), has a rated output of 296W and a conversion efficiency of 15.2%, while a double-sided solar power generation panel, the Trina Solar TSM-440DEG17M (hereinafter referred to as Panel B), has a rated output of 440W and a conversion efficiency of 19.9%. From this, it can be seen that Panel B has improved conversion efficiency compared to Panel A, and per unit area m 2 It has been found that it generates a large amount of electricity per unit, and can save space even when viewed individually, which means that construction costs can be reduced.

[0116] Comparing these solar panels (Panel A and Panel B above) with roughly equivalent total output, Panel A consists of 18 panels and Panel B consists of 12 panels, resulting in an output of 5328W for Panel A and 5280W for Panel B. There is a difference of 48W between these figures. To compare the power generation per panel output, if we convert Panel A's actual power generation of 2361W to match Panel B's output, the power generation becomes 5280 ÷ 5328 × 2361 = 2339W. Comparing this power generation of Panel A = 2339W with Panel B's actual power generation of 3374W, we can see that it represents an improvement of 144.2% (3374 ÷ 2339). Panel B is a product that generates electricity on its back surface as well, and the configuration including the reflector 4 of the present invention further improves the power generation efficiency, making it possible to further reduce space and achieve cost reductions.

[0117] Compared to single-sided solar panels, double-sided photovoltaic panels can increase power generation by approximately 30-50% due to the use of both power-generating surfaces. Therefore, as a solar power generation system 1, it is possible to increase the revenue from selling the generated electricity. For example, if the amount of solar radiation on the slope is 3.5 hours, and the annual power generation per 1MW is 1,277,500kWh from the top surface alone, then with a FIT (Feed-in Tariff) of 40 yen, it is expected that the revenue from selling electricity will be 51,100,000 yen. Furthermore, if the power generation of the solar power generation system 1 of the present invention, that is, a system equipped with power generation surfaces 6 and 12 on both sides and a reflector 4, increases by 30%, the revenue from selling electricity will be 66,430,000 yen, resulting in an annual profit increase of 15,330,000 yen. If this system has a remaining 15-year electricity sales period, it would result in an increase of approximately 230 million yen in electricity sales.

[0118] Figure 4 is a partially enlarged schematic side view illustrating the operation of a solar power generation system. Thus, in the photovoltaic power generation system 1 of this embodiment, direct sunlight enters the power generation surface 6 on the upper surface of the installed double-sided incident photovoltaic power generation panel 2, and reflected light from both direct and scattered sunlight reflected by the reflective layer 14 enters the power generation surface 12 on the lower surface with high reflectivity, resulting in power generation by these two power generation surfaces 6 and 12. The reflector 4 is laid in the light-passing space 13 below the mounting frame 3 and on the ground surface 7 around the outside of the mounting frame 3, so that reflected light strikes the lower power generation surface 12 of the photovoltaic power generation panel 2 well through a predetermined distance space, thereby promoting power generation by this lower power generation surface 12.

[0119] As a result, according to the solar power generation system 1 of this embodiment, the amount of power generated can be improved compared to conventional systems using double-sided ingress solar power generation panels 2, and it is also effective when obtaining as much power as possible in a limited site space, making it possible to construct an environmentally friendly solar power generation system 1.

[0120] Furthermore, according to the reflector 4 of the solar power generation system 1 of this embodiment, the growth of weeds on the site surface 7 is suppressed by the weed-suppressing layer 15, which reduces the time and costs required for maintenance, such as the expenses and labor costs that were necessary for weed removal. As a result, the impact of weeds on the power generation surface, as in the past, is eliminated, preventing a decrease in power generation and resulting in a significant reduction in costs.

[0121] Furthermore, even if a white weed control sheet is used alone as the reflector 4 in the above-described embodiment, it will not be able to reflect direct or scattered sunlight effectively, and a sufficient amount of power generation cannot be obtained. Also, in order to obtain a sufficient weed control effect, it must be made of a dark color such as black, otherwise it will not be able to promote the death of weeds. In other words, even if a single layer of weed control sheet is used as a reflector, it will not be able to reflect an effective amount of sunlight. Therefore, a single layer of weed control sheet cannot also serve as the reflective layer of the present invention. Moreover, a simple weed control sheet does not have sufficient stain resistance, and considering maintenance, it cannot be used in a solar power generation system like the present invention.

[0122] The present invention is not limited to the embodiments described above. It is also intended and within the scope of protection to be provided for the combination of each configuration of the embodiments, as well as for modifications and applications by those skilled in the art based on the description in the specification and well-known art.

[0123] For example, the above configuration example describes a case where an existing solar power generation system, that is, a system composed of single-sided solar power generation panels, is replaced with the configuration of the present invention. However, this solar power generation system 1 may also be newly installed. In this case, the installation can be completed by starting with laying the reflectors 4 on the site surface 7, followed by installing the mounting frame 3, and then attaching the double-sided incident solar power generation panels 2. In this case, the number of solar power generation panels 2 can be calculated based on the required amount of power generation for the site 7 where the system will be installed. Since the solar power generation system 1 of the present invention generates more power than conventional systems, it is possible to configure the system with a smaller site area.

[0124] Furthermore, although the surface of the reflector 4 was given as white in this example, the color of the reflective layer 14 is not limited to the above colors. It can also be a light gray, a light color, or any other color or tone. As long as it reflects direct and scattered sunlight well, that is, it should have a high light reflectivity. For example, if it is a bright green, a green-based color or tone, or has a camouflage pattern, it can reflect direct and scattered sunlight well while reducing any sense of incongruity with the surrounding environment, such as trees, and is effective for the power generation surface 12 on the underside of the solar power generation panel 2.

[0125] Furthermore, while we have described an example in which the reflective sheet constituting the reflective layer 14 is made by forming a metal layer on the surface of a resin sheet as the base material, it is not limited to this as long as the light reflection is good. For example, any sheet-like material will suffice, such as a woven fabric in which a glossing agent is impregnated into the fibers, a woven fabric in which glossy fibers are interwoven in the warp and weft threads, or a nonwoven fabric using such fibers.

[0126] Therefore, according to the solar power generation system 1 of this embodiment, it is possible to increase the amount of power generated, reduce the site area, and lower construction costs. In addition, maintenance costs can be reduced because weeds are suppressed. [Explanation of Symbols]

[0127] 1…Solar power generation system 2… Double-sided ingress photovoltaic panels (photovoltaic panels) 3… Stand 4...Reflector 6…Top power generation surface 7…Site surface 12…Bottom power generation surface 13…Light passing space 14...Reflection layer 15...Weed control layer 16...Perforation part

Claims

1. A reflector used in a photovoltaic power generation system that includes multiple double-incidence type photovoltaic power generation panels installed via a mounting frame, with the power generation surface on the upper surface tilted at a predetermined angle toward the direction of sunlight incidence, The reflector is A reflective layer having a light-reflecting surface that reflects direct and scattered sunlight toward the power-generating surface on the lower surface of the solar power generation panel, containing 7.47 wt% or more of white pigment in its entirety, and made of a thermoplastic resin sheet material containing linear low-density polyethylene and an olefin resin containing low-density polyethylene, A weed control layer made of weed control sheet material, It consists of the reflective layer and the weed-preventing layer, which are laminated and integrally formed. The aforementioned light-reflecting surface, after exposure testing under the following conditions, has a visible light reflectance of 73.2 to 82.5% at wavelengths of 360 to 830 nm, and an infrared reflectance of 4.4 to 7.7% at wavelengths of 3.2 to 19.8 μm. The surface of the reflective layer constituting the reflector is waterproof, and the waterproofing coefficient of the reflector is 1.0 × 10 -11 The time interval should be less than or equal to m / sec. A reflector for a photovoltaic power generation system, characterized in that the thickness of the reflector is 1.0 mm or more. Exposure test conditions Test equipment: Sunshine weather meter (Suga Test Machine S80BBR) Black panel temperature: 63±3℃ Relative humidity: 50 ± 5% Irradiance on the sample surface: 255 ± 10% w / m 2 (wavelength range 300-700nm) Water spray cycle: Water spraying 18 ± 0.5 minutes, water spraying stopped 102 ± 0.5 minutes Irradiation time: 3000 hours

2. The reflector for a photovoltaic power generation system according to claim 1, wherein the white pigment comprises titanium dioxide.

3. The reflector for a photovoltaic power generation system according to claim 1 or 2, characterized in that the surface of the reflective layer has an ultraviolet degradation prevention layer.

4. The reflector for a solar power generation system according to claim 1, characterized in that the weed-suppressing layer consists of a thermoplastic resin and a black pigment.

5. The reflector for a solar power generation system according to claim 4, characterized in that the thermoplastic resin contained in the weed control layer is an olefin resin.

6. The reflector for a photovoltaic power generation system according to claim 5, characterized in that the olefin resin contained in the weed control layer consists of at least one of low-density polyethylene and linear low-density polyethylene.

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