Photovoltaic power generation system

Abstract

[Problem] The present invention addresses the problem of making it possible to increase generating efficiency and reduce site area, and to increase power generation while reducing the cost of construction, maintenance, etc. The present invention also addresses the problem of providing a reflector for solar power generation systems which has excellent weather resistance. [Solution] The present invention comprises a plurality of solar power generation panels (2) installed with a frame (3) such that upper power generation surfaces thereof (6) face the sunlight incidence direction. The solar power generation panels (2) are each a two-surface-incidence-type solar power generation panel provided with a power generation surface (6, 12) at both the upper and lower surfaces thereof. A light passage space (13) is provided below the lower power generation surfaces (12). A reflector (4) is laid so as to cover the site surface (7) in the area beneath the solar power generation panels (2) and in the vicinity thereof. In the reflector (4), a surface side facing the lower power generation surfaces (12) is a reflection layer (14) comprising a sheet material that reflects directly incident sunlight and scattered light, and that is of a color having a high light reflectivity, and the reverse surface side which faces and is in contact with the site surface (7) is a grass preventive layer (15) comprising a grass preventive sheet material. The reflection layer (14) and the grass preventive layer (15) are formed in laminated, integral manner.

Description

[Technical field]

[0001] The present invention relates to a photovoltaic power generation system. [Background technology]

[0002] Conventionally, a type of solar power generation system known as "mega solar" generates large amounts of electricity by arranging a large number of solar panels on the ground. As shown in the following Patent Documents 1 and 2, this mega solar power plant consists of a large number of solar power panels installed over a vast site, with each solar power panel mounted on a stand and inclined at a predetermined angle.

[0003] Solar power generation systems consisting of such a large number of solar power generation panels are installed on a large outdoor site, and therefore require a great deal of effort in maintenance. In other words, in order to prevent a decrease in power generation efficiency, work such as suppressing the growth of weeds on the site below the solar power generation panels is necessary. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-228736 A [Patent Document 2] JP 2015-216766 A [Patent Document 3] JP 2019-068795 A Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, weeds growing on the site surface may cover the solar panels as they grow, which may block sunlight and reduce the amount of sunlight entering the power generation surface. To address this issue, weeds are removed by manual removal, i.e., by pulling them out, or by spraying herbicides, which requires workers, and therefore the work requires a lot of time. In addition, weeds grow back easily without being stopped, so weeding work must be done many times, which is a very troublesome maintenance work. Furthermore, using herbicides may cause damage to the surrounding environment. In order to reduce this work, methods such as covering the site surface with concrete after weeding or laying weed-proof sheets on the ground to inhibit the growth of weeds have been used, but these are troublesome work and there is a need to reduce costs.

[0006] On the other hand, the installation of many solar panels on a large site is necessary to ensure sufficient power generation, and in order to install a large-scale power generation facility with an output of 1 MW (1 megawatt = 1000 kW) or more, a single plot and a flat site surface are required. Therefore, for example, a search is being made to realize an installation state with high power generation efficiency per site area. In order to improve such power generation efficiency, some methods use reflected light from the ground to generate power by laying a reflective multi-sheet on the ground as in Patent Document 3 above and using a solar power generation panel with a power generation function on the back side. Although the above-mentioned weed countermeasures can suppress weeds from growing, they only make it difficult for sunlight to reach the weeds, and the removal and removal work of weeds is unavoidable, and further improvement is desired due to the maintenance costs required. In addition, since the site side of the reflective multi-sheet is made of a resin film, when the sheet is installed on an uneven ground, the reflective surface of the sheet is also not flat, so the reflectivity decreases and there is a risk that the light incident on the back side of the solar power generation panel will decrease. Furthermore, there is a risk that the sheet will be damaged when installed on an uneven ground.

[0007] The present invention has been made in consideration of the above-mentioned situation, and its object is to provide a solar power generation system that improves power generation efficiency, enables a reduction in site area, and increases the amount of power generated while reducing costs such as construction and maintenance. [Means for solving the problem]

[0008] Next, means for solving the above problems will be described with reference to the drawings corresponding to the embodiments. The solar power generation system 1 according to claim 1 of the present invention is a solar power generation system including a plurality of solar power generation panels 2 installed on a stand 3 with a power generation surface 6 on the upper surface inclined at a predetermined angle toward the direction of sunlight incidence, The solar panel 2 is a double-sided incident solar panel having power generating surfaces 6, 12 on both the upper and lower surfaces, The mount 3 is set at a predetermined height, and a light passing space 13 is provided below the lower power generating surface 12 of the double-sided incident type solar panel 2, The solar panel includes a reflector 4 that is laid so as to cover the lower portion of the double-sided incident solar panel 2 and the site surface 7 around the lower portion. The reflector 4 is The front surface side of the double-sided incident type solar power generation panel 2 facing the bottom power generation surface 12 reflects direct light and scattered light of sunlight toward the bottom power generation surface 12. Light The reflective layer 14 is made of a resin sheet material having a reflective surface. The light reflecting surface is Exposure test under the following conditions After that, the light reflectance of sunlight in the wavelength range of 500 to 1000 nm is 70% or more, and the average light reflectance of sunlight in the wavelength range of 5000 to 20000 nm is 15% or less, The reflector 4 is configured The above The surface of the reflective layer 14 has water impermeability, and the water impermeability coefficient of the reflector is 1.0×10 -11 m / sec or less, The back surface side facing the site surface 7 and in contact with the site surface 7 is a weed-control layer 15 made of a weed-control sheet material, The reflective layer 14 and the weed-control layer 15 are integrally formed as a laminate. Exposure test conditions Test equipment: Sunshine Weather Meter (Suga Test Instruments S80BBR) Black panel temperature: 63±3℃ Relative humidity: 50±5% Irradiance on sample surface: 255±10%w / m 2 (wavelength range 300~700nm) Water spray cycle: Water spray 18±0.5 minutes, water spray stop 102±0.5 minutes Irradiation time: 3000 hours

[0009] In this solar power generation system, the solar power generation panel is a double-sided incident type solar power generation panel 2, which makes it possible to increase the amount of power generation, and the reflector 4, which is equipped with a sheet material with high light reflectivity, reflects direct sunlight and scattered light onto the power generation surface 12 on the lower surface, thereby improving the power generation efficiency. In addition, the reflector 4 is equipped with a weed-proof layer 15, which suppresses the growth of weeds from the site surface, thereby reducing maintenance work and associated costs.

[0010] In addition, this solar power generation system reflects sunlight in the visible to near-infrared region on the short wavelength side, and has a low light reflectance in the far-infrared region, which prevents the temperature of the solar power generation panels from rising and does not reduce power generation efficiency.

[0011] Furthermore, in this solar power generation system, the surface of the reflective layer of the reflector laid on the site is provided with water-proofing properties, so that rainwater does not remain on the surface of the reflector 4 but is guided to the outside of the reflector. This makes the surface of the reflective layer 14 less likely to become dirty, reducing the frequency of maintenance.

[0012] The solar power generation system according to claim 2 of the present invention is the solar power generation system according to claim 1, The light reflecting surface is characterized in that it is white.

[0013] In this solar power generation system, the light-reflecting surface is made white, so that direct and scattered sunlight with the wavelengths used for power generation can be effectively reflected onto the lower power generation surface 12, thereby improving the power generation efficiency.

[0014] The solar power generation system according to claim 3 of the present invention is the solar power generation system according to claim 1, The light reflecting surface is characterized in that it is formed of a metal layer.

[0015] In this solar power generation system, the light reflecting surface is made of a metal layer, so that direct sunlight and scattered light can be effectively reflected onto the lower power generation surface 12, thereby improving the power generation efficiency.

[0016] The solar power generation system according to claim 4 of the present invention is the solar power generation system according to any one of claims 1 to 3, The optical film is characterized in that an ultraviolet degradation prevention layer is provided on the surface of the reflective layer.

[0017] In this solar power generation system, the UV degradation prevention layer prevents UV degradation of the reflective layer, i.e., prevents degradation due to exposure to light in the ultraviolet range contained in sunlight, thereby extending the life of the reflector and extending the replacement and maintenance intervals.

[0018] In the solar power generation system of the present invention, the reflector 4 is permeable, and the water permeability coefficient of the reflector 4 is 1.0×10 -5 It may be configured to be up to 1.0 m / sec.

[0019] In this case, by providing water permeability to the reflector 4 laid on the site surface, rainwater can pass through and be guided to the site surface, preventing rainwater from staying on the surface of the reflector 4. This prevents a decrease in power generation efficiency. Effect of the Invention

[0020] According to the solar power generation system of claim 1 of the present invention, the reflector having a sheet material with high light reflectivity reflects direct and scattered sunlight onto the power generation surface on the lower surface of the double-sided incident solar power generation panel, thereby improving the power generation efficiency and increasing the amount of power generation. Furthermore, the increased amount of power generation makes it possible to reduce the number of solar power generation panels installed and promote the reduction of the land area. In addition, the reflector is equipped with a weed-prevention layer that comes into contact with the site surface, which inhibits the growth of weeds from the site surface, thereby reducing maintenance work such as weed removal and reducing the associated costs.

[0021] In addition, according to the solar power generation system of claim 1 of the present invention, since the solar light in the visible to near-infrared region on the short wavelength side is reflected and the light reflectance on the far-infrared region side is low, it is possible to prevent the temperature of the solar power generation panel from increasing, and it is possible to obtain the effect of not reducing the power generation efficiency.

[0022] Furthermore, according to the solar power generation system of claim 1 of the present invention, by providing the surface of the reflector with water-proofing properties, rainwater does not remain on the surface of the reflector but can be guided to the outside of the reflector, which makes the surface of the reflective layer less likely to become dirty and reduces the frequency of maintenance.

[0023] According to the solar power generation system of claim 2 of the present invention, the light reflecting surface is configured in white, so that direct and scattered sunlight having wavelengths used for power generation can be effectively reflected and incident on the lower power generation surface, thereby improving the power generation efficiency.

[0024] According to the solar power generation system of claim 3 of the present invention, the light reflecting surface is made of a metal layer, so that direct sunlight and scattered light can be effectively reflected onto the lower power generation surface, thereby improving the power generation efficiency.

[0025] According to the solar power generation system of claim 4 of the present invention, the ultraviolet degradation prevention layer prevents ultraviolet degradation of the reflective layer, i.e., prevents degradation due to exposure to light in the ultraviolet range contained in sunlight, extends the life of the reflector, and can extend the replacement and maintenance intervals. [Brief description of the drawings]

[0026] [Figure 1] 1 is a schematic perspective view of a solar power generation system according to a first embodiment of the present invention. [Diagram 2] FIG. 11 is a schematic perspective view of a solar power generation system according to a second embodiment of the present invention. [Diagram 3] FIG. 2 is a partially enlarged side view of the solar power generation system. [Figure 4] FIG. 2 is a partially enlarged schematic side view showing the operation of the solar power generation system. [Diagram 5] 1 is a graph showing the relationship between wavelength and light reflectance, which is a test result of a spectral reflectance measurement in an example of a reflective sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an outline of a solar power generation system according to an embodiment of the present invention. The solar power generation system 1 according to this embodiment includes a solar power generation panel 2, a stand 3, and a reflector 4 as main components.

[0028] The solar panel 2 is configured by integrating a plurality of solar cells into a module, and in this embodiment, it is a double-incident solar panel in which solar cells are provided on both the front and back sides and both sides generate electricity. As shown in Fig. 1, multiple photovoltaic panels 2 are arranged in parallel vertically and horizontally, connected horizontally in a long shape, and placed on a mounting stand 3 (described later) to form a solar cell array 5, and these solar cell arrays 5 are arranged in multiple rows in the depth direction on a site of a desired size. These solar cell array rows form a so-called mega solar (large-scale solar power generation), that is, a group of solar cell panels capable of obtaining an output of at least 1 MW or more.

[0029] The solar cell arrays 5 are arranged at a predetermined interval between each other. This interval is set so that the upper power generation surfaces 6 of the solar cell panels 2 of each solar cell array 5 installed in multiple rows are not shaded by direct sunlight and so that workers can pass through the intervals sufficiently for maintenance, etc.

[0030] Solar power panels 2 are available in a variety of configurations, but suitable examples include the Swan series manufactured by JinkoSolar, the MBB bifacial PERC half-cell double-glass module manufactured by JA Solar, the Duomax Twin manufactured by Trina Solar, the HiKu5 series manufactured by Canadian Solar, the LR4-72HBD series manufactured by LONGi Solar, the Q.PEAK DUO manufactured by Hanwha Q Cells, the double-glass bifacial monocrystalline PERC module manufactured by License Energy, and the GCL-M6 / 72GD manufactured by Golden Concord Holdings Limited (GCL). All of these panels generate electricity from the lower power generation surface 12, which is the back surface, thereby increasing the amount of electricity generated per panel by approximately 20%.

[0031] FIG. 3 is a partially enlarged side view of the solar power generation system. The solar cell array 5 is composed of the above-mentioned solar power generation panel 2 and a stand 3 on which the solar cell panel 2 is placed, and is disposed on a site surface 7.

[0032] The mount 3 is composed of pillars 8, cross members 9, connecting brackets 10, etc., which are connected and fixed by means of bolts, welding, etc. The mount 3 is also fixed by a foundation 11 installed on the ground 7.

[0033] The photovoltaic panel 2 is fixed to the mounting base 3 by a connecting bracket 10, and the power generating surface of the photovoltaic panel 2 is inclined, for example, at about 30° from the horizontal. This inclination angle is determined taking into consideration conditions such as the latitude and environment of the installation location, and for example, in high latitude regions in the Northern Hemisphere such as Japan, the power generating surface 6 on the upper surface is inclined toward the south and fixed to the mounting base 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 0.8 m or more, and sufficient space is secured below the mounting frame 3. This space becomes the light passing space 13 for the lower power generating surface 12 of the photovoltaic panel 2.

[0034] The reflector 4 is disposed on the site surface 7 below the mounting base 3 and facing the power generation surface 12 on the lower surface of the photovoltaic panel 2. The reflector 4 is in the form of a sheet, and is composed of a reflective layer 14 that forms the upper surface and a weed-control layer 15 that forms the lower surface, and these layers are integrated into a laminated structure.

[0035] In the first embodiment, the surface of the reflective layer 14 constituting the reflector 4 has water-blocking properties. The reflective layer 14 is made of a sheet material with a color that has high light reflectance and reflects light of wavelengths used for power generation among direct light and scattered light of sunlight, and in this embodiment, it is a reflective sheet with 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, and examples of the resin sheet material include polyethylene resin, polyester resin, polypropylene resin, polyethylene terephthalate, vinyl chloride resin, polystyrene resin, fluororesin, and nylon resin. The surface is white, and the material of the reflective sheet itself is white, or the surface is a white coating film. This waterproof reflective sheet has a waterproof coefficient of 1.0 x 10 -11m / sec or less, and it is possible to effectively guide rainwater and water droplets from the surface to the outside. Here, the "water barrier coefficient" refers to the "water permeability coefficient" in the voluntary standard for water barrier sheets set by the Japan Water Barrier Association, but in the present invention, it is written as "water barrier coefficient" because there is a risk of confusion with the water permeability coefficient described later. This water barrier coefficient is obtained by calculating the water permeability in accordance with JIS Z 0208 "Water barrier packaging material water permeability test method (cup method)" and then using the calculation formula described in "6.4.8 Calculation of water permeability coefficient" in the "Water Barrier Technology and Management Manual" (issued by the Japan Water Barrier Association: May 2019 edition), and the above numerical value shows that the water permeability is low, that is, the water barrier is high.

[0036] The surface of the reflective sheet is preferably water-repellent, and the water-repellent property makes it easy to repel rainwater and direct water droplets from the surface of the reflective sheet to the outside. In addition, the reflective sheet preferably has functions such as chemical resistance, heat resistance, fire and flame resistance, flame retardancy, cold resistance, radiation resistance, thermal conductivity, wear, friction, and antistatic properties. A transparent protective layer may be further provided on the surface. The structure for providing the surface of the reflective sheet with water-repellent properties is as follows. For example, the first method is to include a water-repellent agent in the reflective sheet. The second method is to apply a surface treatment agent made of a water-repellent agent to the surface of the reflective sheet.

[0037] More specifically, the surface of the reflective sheet is white and has high light reflectance. The power generating surface of the photovoltaic panel 2 generates electricity when irradiated with sunlight, but the power generating surface does not need to receive sunlight in the entire wavelength range, and does not need to receive infrared light. However, sunlight in the infrared range generates heat in the photovoltaic panel 2, and when the power generating surface exceeds 50°C, this causes a decrease in power generation efficiency. For this reason, it is preferable to have the surface of the reflective sheet reflect sunlight in the visible to near-infrared region on the short wavelength side. For example, the surface of the reflective sheet is made white and an infrared ray removal film is provided on the surface, for example a filter-like film that removes or absorbs near-infrared and far-infrared rays in the region of 1000 nm or more is provided, so that light in the infrared region is not reflected to the solar power generation panel 2. In addition, since the reflective sheet is easily deteriorated by ultraviolet rays contained in sunlight, an ultraviolet absorbing agent may be blended into the surface layer of the reflective sheet, or an ultraviolet degradation prevention layer may be provided by applying an ultraviolet degradation prevention coating.

[0038] As the above-mentioned reflective sheet, for example, a sheet having a light reflectance of 70% or more for wavelengths of 500 to 1000 nm of 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 having characteristics of not reflecting light in the bands known as short-wavelength infrared rays to medium-wavelength infrared rays, long-wavelength infrared rays (thermal infrared rays), and far-infrared rays is suitable. Also, for example, the reflective sheet surface may be made white and an infrared ray removal film is provided on the surface, preferably a filter-like film that removes or absorbs near-infrared rays and far-infrared rays in the range of 1000 nm or more, so that light in the infrared range is not reflected to the solar power generation panel 2.

[0039] A specific example of a suitable reflective sheet is Vinone Metallobarrier SLS (product name) manufactured by Takiron C.I. Co., Ltd., which is made of an olefin resin consisting of a white layer having a white pigment on the front side and a black layer having a black pigment on the back side. In this case, the reflective sheet itself has a light blocking rate of about 99%, and a weed-preventing effect can also be expected.

[0040] The test results of spectral reflectance measurement of this reflective sheet (Vinone Metallobarrier SLS (product name)) using a Fourier transform infrared spectrophotometer (FTIR) in accordance with JIS R 1693-2:2012 are shown below. [Test equipment] FTIR equipment (Perkin Elmer System 2000) Integrating sphere: (RSA-PE-200-ID, manufactured by Labsphere) 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 ) -Number of times: 200 ·Light source: MIR Detector MIR-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 measurement was carried out using an integrating sphere. These measurements comply with JIS R 1693-2:2012. [Measurement results] The spectral reflectance spectrum at room temperature is shown in a graph in Figure 5 as the relationship between wavelength and light reflectance. As shown in Figure 5, the average light reflectance in the wavelength range of 5,000 to 20,000 nm is low at 10% or less, and light in the ranges known as short-wavelength infrared, medium-wavelength infrared, long-wavelength infrared (thermal infrared), and far-infrared is not reflected.

[0041] The weed-control layer 15 is made of a weed-control sheet having high light-shielding properties, and is made of, for example, nonwoven fabric. The weed-control sheet that forms this weed-control layer 15 is a sheet material that promotes the withering and death of weeds by applying environmental stresses to the weeds, such as heat stress, weight stress, and stress due to inhibition of photosynthesis. Specific materials for such weed control sheets include long fiber nonwoven fabrics such as polyester fibers, polyethylene fibers, polyamide fibers, aramid fibers, acrylic fibers, carbon fibers, polyurethane fibers, cotton threads, wool threads, silk threads, hemp, and wool, and are formed using these alone or in combination of two or more types. Also, weed control sheets may be made of resin sheets that have no water permeability. When the reflector 4 is installed on uneven ground, it is more preferable to use woven or nonwoven fabrics with high cushioning properties so that the reflective layer 14 is not damaged by unevenness of the ground.

[0042] The above-mentioned weed-control sheet is, for example, a nonwoven fabric having a light transmittance of 10% or less for each wavelength measured at 1 nm intervals in the wavelength range of 400 nm to 700 nm, a puncture resistance of 10 to 30 N, and a basis weight of 100 to 400 g / m 2 It is preferable to use what is called The impermeable resin sheet is made of a flexible material such as a resin sheet or rubber sheet having 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, polyvinyl chloride resin, polystyrene resin, fluororesin, nylon resin, etc.

[0043] Specific examples of weed control sheets include the following three types of nonwoven fabric: <Example 1> For example, if the mass per unit area is 150 to 260 g / m 2 , thickness 0.4~0.6mm, density 0.4g / cm 3 , Tensile strength in the machine direction: 290-790N / 5cm, Tensile strength in the cross direction: 190-500N / 5cm, Elongation in the machine direction: 15-30%, Elongation in the cross direction: 15-25%, Tear strength in the machine direction: 80N, Tear strength in the cross direction: 100N, Permeability coefficient: 8.0×10 -5 ~1.0×10 -4 Axtar Mantle weed control sheet (product name) manufactured by Toray Industries, Inc., which has characteristic data of a weed-proofing rate of 95%, a weed-proofing rate of 17 to 20 N, and a weed-proofing rate of 100% is preferably used. <Example 2> In addition, this weed control sheet is generally a sheet with a shading rate, which is the ability to block sunlight, of 95% or more, and has a weight of, for example, about 310 g / m 2 , thickness at 0.7 kPa pressure: approx. 3.8 mm, thickness at 2 kPa pressure: approx. 3.5 mm, tensile strength in the longitudinal direction: approx. 1200 N / 5 cm, tensile strength in the lateral direction: approx. 920 N / 5 cm, longitudinal elongation rate: approx. 70%, transverse elongation rate: approx. 80%, tear strength in the longitudinal direction: approx. 250 N, tear strength in the lateral direction: approx. 240 N, permeability coefficient at 15°C water temperature: 4.4×10 -3A suitable example is 9321N (trade name) manufactured by Toyobo Co., Ltd., which is made of a nonwoven fabric having a tensile strength of about 3200 kPa and a compressive strength of about 100 m / sec. <Example 3> Weight per unit area is 2kg / m 2 Preferably, the weed control sheet has a light transmittance of 10% or less for each wavelength measured in 1 nm increments in the wavelength range of 400 nm to 800 nm, absorbs sunlight and inhibits photosynthesis in the weeds underneath the weed control sheet, and absorbs sunlight to increase the temperature of the weed control sheet itself, thereby applying weight stress to the weeds underneath the weed control sheet.

[0044] Then, the reflective sheet serving as the reflective layer 14 is attached to the front surface, and the weed-control sheet serving as the weed-control layer 15 is attached to the back surface, and these are integrated to obtain the sheet-like reflector 4 having a laminated structure. The reflective sheet and the weed control sheet can be integrated by a method of co-extrusion molding the two sheets into two integrated layers using an extrusion molding device to obtain the reflector 4, or by laminating the reflective sheet and the weed control sheet together by thermal lamination using a 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 integrated by bonding them together over their entire surfaces using an adhesive or by bonding them together in dots or lines to form the reflector 4.

[0045] This sheet-like reflector 4 is formed, for example, with a width of 1.0 to 2.5 m and a length of 10 to 100 m, and is manufactured, stored, and transported in a rolled up state. When the reflector 4 is to be installed, it is unrolled from the rolled up state and spread out on the site surface 7, and multiple pieces are arranged in parallel in the width direction and connected and fixed to each other to cover the site surface 7 without any gaps.

[0046] Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a schematic perspective view of a solar power generation system according to a second embodiment of the present invention. In the second embodiment, the photovoltaic power generation panel 2 and the mounting stand 3 can be the same as those in the first embodiment.

[0047] In the second embodiment, the reflective layer 14 constituting the reflector 4 has water permeability. The water permeability of the reflective layer 14 allows rainwater to quickly penetrate the site surface. Such a water-permeable reflective sheet is constructed by forming a large number of perforations 16 through a woven or nonwoven fabric, or a water-impermeable resin or rubber sheet. By forming the perforations 16, the reflective sheet has a structure that is water permeable in the thickness direction. The perforations 16 are through holes with an inner diameter that allows good water permeability, and are formed on a part or the entire surface.

[0048] The reflective layer 14 is made of a sheet material of a color with high light reflectance that reflects light of the wavelengths used for power generation out of direct light and scattered light from sunlight. Specific nonwoven materials include long fiber nonwoven fabrics such as polyester fibers, polyethylene fibers, polyamide fibers, aramid fibers, acrylic fibers, carbon fibers, polyurethane fibers, cotton threads, wool threads, silk threads, hemp, and wool, and these may be used alone or in combination of two or more types. In addition, the light transmittance for each wavelength measured in 1 nm increments in the wavelength 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 / m 2 It is preferable to use what is called The water-impermeable sheet having the above-mentioned perforated portion 16 is made of a flexible material such as a resin sheet or rubber sheet having 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, polyvinyl chloride resin, polystyrene resin, fluororesin, nylon resin, etc.

[0049] It is preferable to use a weed-control sheet with high light-blocking properties for the weed-control layer 15. For example, a nonwoven fabric is 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 thread, wool thread, silk thread, hemp, and wool, and these can be used alone or in combination of two or more types. In addition to the nonwoven fabric, a three-dimensional mesh such as an embossed three-dimensional sheet or net can also be used as the drainage core material by integrating it with the nonwoven fabric. In order to obtain a sufficient weed-control effect, it is preferable that at least one layer constituting the weed-control layer is constructed in a dark color such as black in order to provide light-blocking properties. However, if the light-blocking properties of the reflective layer are sufficient, the weed-control sheet does not need to have light-blocking properties.

[0050] Specific examples of weed control sheets include the following three types of nonwoven fabric: <Example 1> For example, if the mass per unit area is 150 to 260 g / m 2 , thickness 0.4~0.6mm, density 0.4g / cm 3 , Tensile strength in the machine direction: 290-790N / 5cm, Tensile strength in the cross direction: 190-500N / 5cm, Elongation in the machine direction: 15-30%, Elongation in the cross direction: 15-25%, Tear strength in the machine direction: 80N, Tear strength in the cross direction: 100N, Permeability coefficient: 8.0×10 -5 ~1.0×10 -4 Axtar Mantle weed control sheet (product name) manufactured by Toray Industries, Inc., which has characteristic data of a weed-proofing rate of 95%, a weed-proofing rate of 17 to 20 N, and a weed-proofing rate of 100% is preferably used. <Example 2> In addition, this weed control sheet is generally a sheet with a shading rate, which is the ability to block sunlight, of 95% or more, and has a weight of, for example, about 310 g / m 2 , thickness at 0.7 kPa pressure: approx. 3.8 mm, thickness at 2 kPa pressure: approx. 3.5 mm, tensile strength in the longitudinal direction: approx. 1200 N / 5 cm, tensile strength in the lateral direction: approx. 920 N / 5 cm, longitudinal elongation rate: approx. 70%, transverse elongation rate: approx. 80%, tear strength in the longitudinal direction: approx. 250 N, tear strength in the lateral direction: approx. 240 N, permeability coefficient at 15°C water temperature: 4.4×10 -3A suitable example is 9321N (trade name) manufactured by Toyobo Co., Ltd., which is made of a nonwoven fabric having a tensile strength of about 3200 kPa and a compressive strength of about 100 m / sec. <Example 3> Weight per unit area is 2kg / m 2 Preferably, the weed control sheet has a light transmittance of 10% or less for each wavelength measured in 1 nm increments in the wavelength range of 400 nm to 800 nm, absorbs sunlight and inhibits photosynthesis in the weeds underneath the weed control sheet, and absorbs sunlight to increase the temperature of the weed control sheet itself, thereby applying weight stress to the weeds underneath the weed control sheet.

[0051] Then, the reflective sheet serving as the reflective layer 14 is attached to the front surface, and the weed-control sheet serving as the weed-control layer 15 is attached to the back surface, and these are integrated to obtain the sheet-like reflector 4 having a laminated structure. The reflective sheet and the weed control sheet may be integrated into a reflector 4 by a method of laminating the reflective sheet and the weed control sheet together by thermal lamination using a laminating device, a method of thermocompressing the reflective sheet and the weed control sheet together using a heat press device, a method of bonding the reflective sheet and the weed control sheet together over their entire surfaces using an adhesive or the like, or by bonding them together in dots or lines, or a method of integrating them by needle punching or the like.

[0052] This sheet-like reflector 4 is formed, for example, with a width of 1.0 to 2.5 m and a length of 10 to 100 m, and is manufactured, stored, and transported in a rolled up state. When the reflector 4 is to be installed, it is unrolled from the rolled up state and spread out on the site surface 7, and multiple pieces are arranged in parallel in the width direction and connected and fixed to each other to cover the site surface 7 without any gaps.

[0053] The reflector 4 in this embodiment 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 -5 ~1.0m / sec, which effectively guides rainwater and other water to the bottom of the sheet. Furthermore, the permeability coefficient is 5.0×10 -5A coefficient of permeability of 1.0 m / sec or less is preferable. If the coefficient of permeability is equal to or higher than the lower limit, the effect of directing rainwater to the underside of the sheet is enhanced. If the coefficient of permeability is equal to or lower than the upper limit, the weight stress of the reflector is fully exerted, a good weed control effect can be obtained, and cushioning properties against unevenness of the ground can also be obtained. This coefficient of permeability can be measured by a method conforming to JIS A 1218 "Testing method for permeability of soil".

[0054] For this reflector 4, a sheet material with excellent water permeability and chemical resistance, which is made by integrating a black embossed three-dimensional sheet as a drainage core material and a long-fiber spunbond nonwoven fabric as a protective material, in layers, such as Geoflow (product name) made by Daipla Co., Ltd., can be used. Also, a sheet made by sandwiching a three-dimensional mesh such as a net between nonwoven fabrics from above and below can be used as the substrate.

[0055] Next, a third embodiment of the present invention will be described. In the third embodiment, the same members as those in the first embodiment are denoted by the same reference numerals and will be described with reference to FIG. In the third embodiment, similarly to the above-described first embodiment, the reflector 4 is disposed on the site surface 7 below the mounting base 3 and facing the power generation surface 12 on the lower surface of the photovoltaic panel 2. The reflector 4 is in the form of a sheet, and is composed of a reflective layer 14 that forms the upper surface and a weed-control layer 15 that forms the lower surface, and these layers are integrated into a laminated structure.

[0056] The reflective layer 14 is made of a material of a color such as white that has a high light reflectance and reflects light of the wavelengths used for power generation among direct and scattered sunlight, and is a reflective sheet made of a flexible material such as a resin sheet or a rubber sheet. The weed-control layer 15 is made of, for example, a black material that has water-blocking and light-blocking properties, and is a weed-control sheet made of a flexible material such as a resin sheet or a rubber sheet. The reflective sheet and the weed control sheet are laminated together to form a single sheet material, which constitutes the reflector 4.

[0057] The reflector 4 has a thickness of 1.0 to 2.0 mm, preferably 1.0 to 1.3 mm, of which the thickness that becomes the reflective layer 14 is preferably about 0.4 mm. In the third embodiment, the surface of the reflective layer 14 constituting the reflector 4 is also configured to have a water-impermeable property, and the water-impermeable coefficient is 1.0×10 -11 m / sec or less, which allows rainwater and water droplets to be effectively guided outward from the surface. In addition, both the reflective layer 14 and the weed-control layer 15 have a light-shielding property, which allows a weed-control effect to be obtained.

[0058] The resin material constituting the reflective layer 14 in the third embodiment is a mixture of thermoplastic resin, olefin resin, and white pigment in a predetermined weight percentage. Examples of the thermoplastic resin include olefin resin, vinyl chloride resin, polyester resin, rubber, thermoplastic elastomer, polystyrene resin, fluororesin, and nylon resin. Of these, olefin resin is preferred, and low-density polyethylene and linear low-density polyethylene are more preferred. Examples of olefin resins include ethylene resins such as low-density polyethylene, linear low-density polyethylene using a Ziegler catalyst, linear low-density polyethylene using a metallocene catalyst, and the like, and polypropylene resins such as ethylene-vinyl acetate copolymer, homopolypropylene, random propylene copolymer, and the like. In particular, it is preferable to use at least one linear low-density polyethylene using a metallocene catalyst. Examples of white pigments include titanium oxide, zirconium oxide, calcium carbonate, calcium sulfate, zinc oxide, barium sulfate, barium carbonate, silica, alumina, kaolin, clay, talc, white earth, aluminum hydroxide, magnesium carbonate, and white hollow resin emulsion, and titanium oxide is preferred. In addition to the above-mentioned resin and pigment, the reflective layer 14 contains weather resistance agents, such as ultraviolet absorbing agents and light stabilizers.

[0059] The resin material constituting the weed-control layer 15 is a mixture of thermoplastic resin, olefin resin, and black pigment at a predetermined weight percentage. The thermoplastic resin and olefin resin are the same as the resin material constituting the reflective layer 14 described above. Examples of 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, and preferably carbon blacks.

[0060] Then, the reflective sheet that will become the reflective layer 14 is on the front side, and the weed-control sheet that will become the weed-control layer 15 is on the back side, and they are integrated to obtain a laminated structure of a sheet-like reflector 4. The integrated reflector 4 is a sheet material with a white front side and a black back side. The reflective sheet and the weed control sheet can be integrated by a method of co-extrusion molding the two sheets into two integrated layers using an extrusion molding device to obtain the reflector 4, or by laminating the reflective sheet and the weed control sheet together by thermal lamination using a 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 integrated by bonding them together over their entire surfaces using an adhesive or by bonding them together in dots or lines to form the reflector 4.

[0061] This sheet-like reflector 4 is formed, for example, with a width of 1.0 to 2.5 m and a length of 10 to 100 m, and is manufactured, stored, and transported in a rolled up state. When the reflector 4 is to be installed, it is unrolled from the rolled up state and spread out on the site surface 7, and multiple pieces are arranged in parallel in the width direction and connected and fixed to each other to cover the site surface 7 without any gaps.

[0062] As the weed control layer 15, a nonwoven fabric may be laminated as in the first embodiment. In that case, the weight is about 310 g / m 2, thickness at 0.7 kPa pressure: approx. 3.8 mm, thickness at 2 kPa pressure: approx. 3.5 mm, tensile strength in the longitudinal direction: approx. 1200 N / 5 cm, tensile strength in the lateral direction: approx. 920 N / 5 cm, longitudinal elongation rate: approx. 70%, transverse elongation rate: approx. 80%, tear strength in the longitudinal direction: approx. 250 N, tear strength in the lateral direction: approx. 240 N, permeability coefficient at 15°C water temperature: 4.4×10 -3 A nonwoven fabric having a linear velocity of 1.5 m / sec and a burst strength of about 3200 kPa is preferably used. When a weed control layer is formed from this nonwoven fabric, similarly to the first embodiment described above, the reflective layer 14 is attached to the front surface and the nonwoven fabric is attached to the back surface, and they are bonded together using a bonding method such as heat pressing, heat embossing, hot melt adhesive, ultrasonic bonding, or high frequency bonding to obtain a sheet-like reflector 4 as a laminated structure.

[0063] The reflector according to the third embodiment, which is a single sheet material in which the reflective sheet and the weed control sheet are laminated together, preferably has the following physical properties.

[0064] The tear strength of the reflector is preferably 60N to 300N, more preferably 70N to 250N. Also, it is more preferably 90N to 200N. By setting the tear strength to the lower limit or more, it is possible to obtain a reflector that is not easily broken by impact. By setting the tear strength to the upper limit or less, the reflector has flexibility, and even when installed on uneven ground, it is possible to obtain a reflective surface that is flat or nearly flat.

[0065] As described above, the reflectors are used as a welded joint by overlapping the widthwise ends of the reflectors, and the joint shear strength between the reflectors is preferably 70 N / cm to 400 N / cm. More preferably, it is 100 N / cm to 300 N / cm. By making the joint shear strength equal to or greater than the lower limit, peeling of the sheets from the overlapping portion during construction is suppressed. Furthermore, by making the joint shear strength equal to or less than the upper limit, the overlapping portion has flexibility, and even when the reflector is installed on uneven ground, the reflecting surface can be a flat or nearly flat, smooth surface.

[0066] The reflector preferably has a tensile strength of 140 N / cm or more and 1000 N / cm or less, more preferably 200 N / cm or more and 800 N / cm or less. By making the tensile strength equal to or greater than the lower limit, the reflector has sufficient strength and is excellent in workability. Furthermore, by making the tensile strength equal to or less than the upper limit, the reflector has flexibility, and even when installed on uneven ground, the reflective surface can be flat or nearly flat. Furthermore, the tensile strength of this reflector after long-term use, i.e., after long-term weathering, is preferably 100 N / cm to 1000 N / cm, and more preferably 200 N / cm to 800 N / cm. By setting the tensile strength after long-term weathering in the above range, the reflector has sufficient weather resistance and can maintain a balance between strength and flexibility for a long period of time, thereby reducing the frequency of replacement.

[0067] The reflector preferably has a tensile elongation at break of 300% to 1000%, more preferably 400% to 900%, and even more preferably 600% to 800%. By making the tensile elongation at break equal to or greater than the lower limit, the reflector has flexibility, and even when installed on uneven ground, the reflecting surface can be flat or nearly flat with a gentle slope. Furthermore, by making the tensile strength equal to or less than the upper limit, the reflector has sufficient strength and is excellent in workability. Furthermore, the tensile elongation at break of this reflector after long-term use, i.e., after long-term weathering, is preferably 250 to 1000%, more preferably 400 to 900%, and even more preferably 500 to 800%. By keeping the tensile elongation at break after long-term weathering within the above range, the reflector has sufficient weather resistance and can maintain a balance between strength and flexibility for a long period of time, thereby reducing the frequency of replacement.

[0068] The reflector preferably has a visible light reflectance of 55% or more when used for a long period of time, i.e., after long-term weathering, more preferably 65% ​​or more, and even more preferably 70% or more. By making the visible light reflectance after long-term weathering equal to or greater than the above values, the reflector has sufficient weather resistance, and can efficiently reflect light onto the power generation surface on the lower side of the solar panel for a long period of time, thereby maintaining power generation efficiency.

[0069] The reflector preferably has an infrared reflectance of 1% to 15%, more preferably 3% to 10%, before and after use, i.e., before and after long-term weathering. By keeping the infrared reflectance within the above range before and after long-term weathering, it is possible to suppress heat generation in the solar panel due to light with wavelengths in the infrared region, and prevent a decrease in power generation efficiency.

[0070] An example of the third embodiment will now be described. In the examples described below, the ingredients that respectively constitute the reflective layer 14 and the weed-control layer 15 will be abbreviated as follows: thermoplastic resin: PE1, olefin resin: PE2, white pigment: W-MB, black pigment: B-MB, and weather-resistant agent: UV-MB.

[0071] [Combined ingredients] The ingredients used in the examples are as follows: PE1 = Metallocene linear low-density polyethylene with melting point: 98°C, MFR: 2.0g / 10min (JIS K 7210-1, temperature 190°C, load 2.16kg), density: 0.908g / cm3 PE2 = Melting point: 111°C, MFR: 0.35g / 10min (JIS K 7210-1, temperature 190°C, load 2.16kg), density: 0.922g / cm 3 The basic properties of the high-pressure low-density polyethylene are MFR of 0.35g / 10min (JIS K 7210-1, temperature 190°C, load 2.16kg), density of 922kg / m 3 The mechanical properties are tensile breaking stress of 20MPa, tensile breaking elongation of 650%, and tensile impact strength of 470KJ / m 2It has a flexural modulus of 225MPa, a durometer hardness of 55D, an environmental stress crack resistance of 9Hr, and thermal properties such as a Vicat softening temperature of 97℃ and a melting temperature (DSC) of 111℃. It is additive-free and has high strength. ·W-MB=Density: 2.5g / cm 3 Titanium dioxide 83wt% polyethylene masterbatch UV-MB = Melting point: 110℃, Density: 0.995g / cm 3 Polyethylene masterbatch containing 20wt% of the hindered amine light stabilizer (dimethyl succinate · 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl-4-piperidine polycondensate) B-MB = Low density polyethylene masterbatch containing 40wt% carbon black

[0072] [Manufacturing procedure] <Example 1> The reflective layer 14 was made by mixing 59% by weight of PE1, 27% by weight of PE2, 9% by weight of W-MB, and 5% by weight of UV-MB, and the weed control layer 15 was made by mixing 75% by weight of PE1, 19% by weight of PE2, and 6% by weight of B-MB. Each was fed into a separate extruder, and a co-extrusion method was used to produce a reflector with a total thickness of 1.14 mm, with the reflective layer 14 being 0.40 mm and the weed control layer 15 being 0.74 mm. <Example 2> Using the same procedure as above, a reflector was produced with 45% by weight of PE1, 36% by weight of PE2, 9% by weight of W-MB, and 10% by weight of UV-MB, with a reflective layer 14 of 0.40 mm and a weed-proof layer 15 of 0.74 mm and a total thickness of 1.14 mm. <Example 3> Using the same procedure as above, 73% by weight of PE1, 18% by weight of PE2, and 9% by weight of W-MB were mixed to form the reflective layer 14, without adding UV-MB. In addition, 74% by weight of PE1, 18% by weight of PE2, and 8% by weight of B-MB were mixed to form 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.

[0073] [Table 1]

[0074] [evaluation] The reflectors of the three examples manufactured by the above manufacturing procedure were evaluated according to the following items. The results are shown in Table 2. <Test item 1: Tear strength> Using the reflectors of each example, the tear strength was measured in accordance with "6.6 Tear test" described in "6. Test methods for synthetic rubber and rigid resin-based waterproof sheets" in the "Waterproofing Technology and Construction Management Manual" (issued by the Japan Waterproofing Association: May 2019 edition).

[0075] <Test item 2: Shear strength of joints between sheets> Two reflectors were prepared for each example, and the ends of these two reflectors were overlapped with an overlap width of 120 mm. Using a Leister Tweeny automatic welding machine, the reflectors were pressed with a roll (having a 15 mm x 2 row pressing portion) while applying hot air at 500°C to obtain a welded joint. The specimens were then cooled to room temperature. The specimens were cut at the overlap position to a length of 250 mm and a width of 25 mm in the overlap direction, and the maximum load at break was measured at a tensile speed of 200 mm / min. The tensile strength was calculated using the following formula, and used as the shear strength of the joint between the sheets. Tensile strength (N / cm) = Maximum load (N) ÷ Width of sample piece (cm)

[0076] <Test item 3: Tensile strength · Test item 4: Tensile elongation at break> Using the reflectors of each example, the tensile strength and the elongation at tensile break were measured in accordance with "6.5 Tensile test" described in "6. Test methods for synthetic rubber and rigid resin-based waterproof sheets" in the "Waterproofing Technology and Construction Management Manual" (issued by the Japan Waterproofing Association: May 2019 edition). The samples were taken before and after the exposure test (long-term weather resistance test) and measurements were taken. The exposure test was as follows: Exposure test: Using a Sunshine Weather Meter (model number: Sunshine Weather Meter S80BBR) manufactured by Suga Test Instruments Co., Ltd., tests were conducted under the following conditions in accordance with JIS A 1415-1999 and JIS K 7350-4-1996. Test conditions Black panel temperature: 63±3℃ Relative humidity: 50±5% Irradiance on sample surface: 255±10%w / m 2 (wavelength range 300~700nm) Water spray cycle: Water spray 18±0.5 minutes, water spray stop 102±0.5 minutes Irradiation time: 3000 hours

[0077] <Test item 5: Visible light (360~830nm) reflectance> The reflectors of each embodiment were cut into samples of 20 x 20 mm after the exposure test. The samples were used to measure the total reflectance of the reflective layer 14 in the wavelength range of 190 to 2500 nm using a Hitachi High-Tech Science spectrophotometer (UH4150) and an integrating sphere. The total reflectance in the wavelength range of 360 to 830 nm was averaged using aluminum oxide (Al2O3 white plate) as a standard sample, and this was taken as the visible light reflectance. The measurements were performed with N=3. (Apparatus used to measure visible light reflectance) · φ60mm integrating sphere, inner surface coated with Spectralon Wavelength range: 190~2500nm Scan speed: 600nm / min Slit width: 5nm Sampling interval: 5nm Measurement environment: Room temperature (25°C), in air Equipment used: Hitachi spectrophotometer: UH4150 (manufactured by Hitachi High-Tech Science)

[0078] <Test item 6: Infrared (3.2~19.8μm) reflectance The reflector of each example was cut into a size of 20 x 20 mm, and the obtained samples were used to measure the regular reflectance of the reflective layer in the wavelength range of 1.3 to 20.0 μm by measuring the relative reflectance with a gold mirror as the standard using a Fourier transform infrared spectrometer (Spotlight 400) manufactured by PerkinElmer Japan. The regular reflectance in the infrared region of 3.2 to 19.8 μm was averaged, and this was taken as the infrared reflectance. The measurement was carried out with N=3. The samples were taken before and after the above-mentioned exposure test, and measurements were carried out for each. (Infrared reflectance device) - Relative reflectance measurement using a gold mirror as the standard (specular reflectance measurement) ·Incidence angle: 23 degrees Scan count: 64 Wavelength range: 1.3-20.0μm (7800-500cm -1 ) ·Light source: MIR Detector: MCT Beam splitter: OptKBr Sampling interval: 2cm -1 Measurement environment: Room temperature (20℃), in air Equipment used: FT-IR Spotlight 400 (PerkinElmer)

[0079] <Test item 7: Appearance of the reflective layer> The reflectors of the respective Examples were used as samples for the above-mentioned exposure test, and the reflective layer 14 was observed under a microscope at a magnification of 50 times to evaluate the occurrence of cracks and peeling. ◎: No cracks observed ○: Cracks occur, but the reflective layer does not peel off. ×: Many cracks occurred and the reflective layer peeled off.

[0080] The above-mentioned evaluation results of the reflectors of the respective examples are shown in Table 2.

[0081] [Table 2]

[0082] As a result of exposure, it is found that the tensile strength, elongation at tensile break, visible light reflectance, and infrared reflectance of the reflectors of Examples 1 and 2 containing a weathering agent did not decrease, and they have excellent weather resistance, compared to Example 3 containing no weathering agent (UV-MB). In addition, when the deterioration of the visible light reflectance after 3000 hours was confirmed using an enlarged photograph, the occurrence of cracks was confirmed as the surface condition in Example 3, but peeling of the reflective layer 14 did not occur, and there is no problem in using any of the reflectors. On the other hand, no significant cracks were observed in Examples 1 and 2, which indicates that the incorporation of the weather resistance agent inhibits deterioration and suppresses the decrease in light reflectance. In other words, the results show that the reflector 4 is suitable for use in a solar power generation system.

[0083] In the above-mentioned configuration of the reflector, the surface of the reflective sheet constituting the reflective layer serving as the surface has been described as being white, but a metal layer may be formed on the surface as a sheet material of a color with high light reflectance that reflects direct light and scattered light from sunlight. The surface of this reflective sheet with a metal layer has a metallic gloss color due to the metal layer.

[0084] For example, it may be configured as a metal foil-coated reflective sheet having a metal foil such as aluminum foil formed on the surface. In this metal foil-coated reflective sheet, the base material is, for example, the above-mentioned resin sheet, and a metal foil having a thickness of 0.5 to 1.0 mm is formed on one surface of the resin sheet as the base material. In addition, when it is made into a metal foil, since it totally reflects sunlight, it also reflects light in the infrared region as described above, so heat measures are necessary. For this reason, it is preferable to apply a matte coating to prevent gloss, i.e., regular reflection like a mirror, 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.

[0085] In addition to the metal foil, a metal film may be formed on a resin sheet, and the reflective surface may be formed by vapor deposition, painting, plating, or other means. Furthermore, in addition to the above aluminum, at least one light reflecting agent selected from the group consisting of powders of titanium oxide, alumina, talc, calcium carbonate, zinc oxide, silica, mica powder, powdered glass, powdered nickel, powdered aluminum, and the like may be formed into a film to give a color ranging from silver to near white. A transparent protective film may be formed by coating on the surface of the metal layer, etc. This protective film is made of, for example, a resin material, such as polyethylene resin, and is formed as a coating film, which is a preferable configuration for providing water repellency and antifouling properties.

[0086] Next, a procedure for installing the above-mentioned solar power generation system 1 will be described. The procedure described below is a so-called renovation procedure in which an old photovoltaic power generation system has already been constructed, this is replaced with the photovoltaic power generation system 1 of the present invention, and the site and mounting frame are reused.

[0087] First, the site is cleared of weeds. As weeds may grow under the solar panels and the mountings, they are removed by mowing them down. Next, remove the roots of the weeds. Weeds may grow back from the roots, so it is best to remove as many roots as possible from the soil. You can also spray herbicide at this point.

[0088] Next, the reflector 4 is installed under the stand 3. If the foundation 11 constituting the mounting stand 3 is buried underground, the sheet-like reflector 4 is hollowed 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 covers the site surface 7 with the weed control layer 15 facing downward and the reflective layer 14 facing upward so as to fit as closely as possible. The reflector 4 is laid over the portion where the mounting stand 3 is installed and further outside the outermost periphery with a width of about 2 m. The reflector 4 is fixed to the ground by penetrating pin-shaped fasteners 17 at a specified interval. If the reflector 4 is in a rolled state as described above, it is laid while being unrolled, and fixed by adhesion or welding so that they are joined together in the width direction.

[0089] Next, the existing solar panels will be removed. The existing solar power generation panels that are connected and fixed to the mounting base 3 are removed from the mounting base 3 and completely removed. At this time, the electrically connected parts are also removed.

[0090] Next, a double-illuminated solar panel 2, which is a solar panel of this embodiment, is attached. Since the stand 3 has already been assembled, a new solar panel 2 is placed on the stand 3 and connected and fixed in place. At this time, if the inclination angle needs to be changed, the angle is adjusted and fixed. After that, electrical connections are made to each solar panel 2, and the system is completed.

[0091] Next, the operation of the above-mentioned configuration will be described. In the solar power generation system 1 of this embodiment, the existing single-sided solar power generation panel is replaced with a double-sided incident type power generation panel 2, and a reflector 4 that reflects direct and scattered solar light is installed on the site surface 7, making it possible to increase the amount of power generation.

[0092] In other words, if the solar power generation panels of an existing solar power generation system have only one power generation side and generate 250 W of power per panel, 4000 panels are required to generate 1000 kW (1 MW); however, in the case of this embodiment, if the solar power generation panels are double-illuminated solar power generation panels 2 that can generate 320 W of power on both sides per panel, installing the same 4000 panels can generate 1280 kW of power, which is a 1.28-fold increase in power generation when compared to the rated output power generation.

[0093] For this reason, in order to obtain 1000 kW of power generation, as before the replacement, in the case of the solar power generation system 1 of this embodiment, 3125 of the above-mentioned solar power generation panels 2 can be obtained. In other words, since the size of each solar power generation panel 2 is approximately the same dimension, it is possible to reduce the total area of ​​the entire solar power generation panels 2 by approximately 22%. In other words, when reconstructing, it is possible to reduce the installation area and the number of solar panels 2 and generate the same amount of power as before, making it possible to construct a solar power generation system 1 that can obtain the same amount of power generation by narrowing and reducing the previous site area.

[0094] The conversion efficiency of a solar panel is the percentage of the solar energy that it can actually convert into electrical energy. For example, an existing single-sided solar panel, SRM296P-72N manufactured by SANIX (hereinafter referred to as Panel A), has a rated output of 296W and a conversion efficiency of 15.2%, while a double-sided solar panel, TSM-440DEG17M manufactured by Trina Solar (hereinafter referred to as Panel B), has a rated output of 440W and a conversion efficiency of 19.9%. This shows that Panel B has a higher conversion efficiency than Panel A, and the conversion efficiency per unit area m 2 It is clear that a large amount of electricity is generated per unit area, and even when considered individually, space can be saved, which means that construction costs can be reduced.

[0095] If we compare these solar panels (Panel A and Panel B above) with roughly the same total output, Panel A has 18 panels and Panel B has 12 panels, giving 5,328W for Panel A and 5,280W for Panel B. There is a difference of 48W between these figures, but in order to compare the amount of power generated per panel output, if we convert the actual power generation of Panel A, 2,361W, to Panel B, the power generation becomes 5,280÷5,328×2,361=2,339W. Comparing the power generation of Panel A, 2,339W, with the actual power generation of Panel B, 3,374W, we can see that this is an improvement of 144.2% from 3,374÷2,339. Panel B is a product in which power is generated on the back side as well, and the inclusion of reflector 4 of the present invention in the configuration further improves power generation efficiency, making it possible to further reduce space and realize cost reductions.

[0096] Compared to solar panels that generate electricity from only one side, bifacial solar panels can generate electricity 30 to 50% more, thanks to the power generation surfaces on both sides. As a result, the solar power generation system 1 can increase the income from selling the generated power. For example, if the amount of solar radiation on the slope is 3.5 hours, and the annual power generation per MW is 1,277,500 kWh from the top power generation surface alone, and the FIT (feed-in tariff) is 40 yen, the expected revenue from selling electricity is 51,100,000 yen. If the amount of power generated by the photovoltaic power generation system 1 of the present invention, that is, a system having power generation surfaces 6, 12 on both sides and a reflector 4, increases by 30%, the income from selling electricity will be 66,430,000 yen, resulting in an annual revenue increase of 15,330,000 yen. If there are 15 years remaining in the electricity sales period for this system, this will result in an increase in electricity sales of approximately 230 million yen.

[0097] FIG. 4 is a partially enlarged schematic side view showing the operation of the solar power generation system. Thus, in the photovoltaic power generation system 1 of this embodiment, direct sunlight is incident on the upper power generation surface 6 of the installed double-sided incidence photovoltaic panel 2, and direct sunlight and scattered light reflected by the reflective layer 14 are incident with high reflectivity on the lower power generation surface 12, and power is generated by these power generation surfaces 6, 12 on both sides. The reflector 4 is installed in the light passing space 13 below the frame 3 and on the site surface 7 around the outside of the placed frame 3, so that the reflected light falls satisfactorily on the lower power generation surface 12 of the photovoltaic panel 2 through a predetermined space, promoting power generation by this lower power generation surface 12.

[0098] As a result, according to the solar power generation system 1 of this embodiment, the double-illuminated solar power generation panel 2 can improve the amount of power generation compared to conventional methods, and is also effective in obtaining as much power generation as possible in a limited site space, making it possible to construct an environmentally friendly solar power generation system 1.

[0099] In addition, 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-proof layer 15, which makes it possible to reduce the expenses and labor costs required for removing weeds, as well as the time and expenses required for maintenance. Since there is no longer an impact on the power generation surface caused by weeds as in the past, there is no decrease in the amount of power generation, and costs are significantly reduced.

[0100] In addition, even if a white weed control sheet is used alone as the configuration of the reflector 4 of the present embodiment described above, it is not possible to satisfactorily reflect direct sunlight and scattered light, and sufficient power generation cannot be obtained. Furthermore, in order to obtain a sufficient weed control effect, it is necessary to use a dark color such as black in order to promote the death of weeds. In other words, even if a single layer of weed control sheet is used as a reflector, it is not possible 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. Furthermore, a simple weed control sheet is not configured to provide sufficient stain resistance, and cannot be used in a solar power generation system such as the present invention when maintenance is taken into consideration.

[0101] The present invention is not limited to the above-described embodiments, and the present invention also contemplates the mutual combination of the various components of the embodiments, as well as modifications and applications by those skilled in the art based on the description in the specification and well-known techniques, and these are included in the scope of protection sought.

[0102] For example, in the above configuration example, an existing solar power generation system, i.e., a system configured with a single-sided solar power generation panel, is described as being replaced with the configuration of the present invention, but this solar power generation system 1 may also be installed as a new system. In this case, construction can begin with laying the reflector 4 on the site surface 7, followed by setting up the mounting base 3 and attaching the double-illuminated photovoltaic panel 2, and then completing the installation in the following order. In this case, the number of solar panels 2 required for the site 7 on which they will be installed can be calculated based on the amount of power generation required. Since the solar power generation system 1 of the present invention generates more power than conventional systems, it is possible to reduce the site area required for the system.

[0103] In addition, although the surface of the reflector 4 is white in this example, the color of the reflective layer 14 is not limited to the above color, and may be a light gray color, a bright color, a color, a tone, etc., as long as it can satisfactorily reflect direct sunlight and scattered light, i.e., have a high light reflectance. For example, if it is bright green, a color, color, tone, or pattern such as a camouflage color based on green, it can satisfactorily reflect direct sunlight and scattered light while reducing the sense of incongruity in an environment with trees, etc., and is effective for the power generation surface 12 on the underside of the solar power generation panel 2.

[0104] Furthermore, although an example has been described in which the reflective sheet constituting the reflective layer 14 is formed on a resin sheet as a base material with a metal layer formed on the surface, the present invention is not limited to this as long as it has good light reflection, and any material that can be formed into a sheet shape, such as a woven fabric in which a gloss agent is impregnated into the fibers, a woven fabric in which a gloss agent has been added, a woven fabric in which glossy fibers are entangled with the warp and weft threads, or a nonwoven fabric using such fibers, may be used.

[0105] Therefore, the solar power generation system 1 according to this embodiment can improve the amount of power generation, reduce the site area, and reduce the construction cost. In addition, weeds are suppressed, so the maintenance cost can be reduced. [Explanation of symbols]

[0106] 1. Solar power generation system 2...Double-sided solar panel (solar panel) 3…Frame 4...Reflector 6…Top power generation surface 7. Site area 12...Bottom power generation surface 13…Light passing space 14...Reflection layer 15…Weed-proof layer 16...Perforation part

Claims

1. A solar power generation system including a plurality of solar power generation panels installed on a stand with the power generation surface on the upper surface inclined at a predetermined angle toward the direction of sunlight incidence, The solar power generation panel is a double-sided incident solar power generation panel having power generation surfaces on both the upper surface and the lower surface, The mounting base is set at a predetermined height to provide a light passing space below the bottom power generating surface of the double-sided incident type solar panel, A reflector is provided so as to cover the lower portion of the double-sided incident type solar panel and the site surface around the panel, The reflector is a surface side facing a lower power generating surface of the double-sided incident solar panel is a reflective layer made of a resin sheet material having a light reflecting surface that reflects direct light and scattered light of sunlight toward the lower power generating surface, The light reflecting surface has a light reflectance of 70% or more in the wavelength range of 500 to 1000 nm of sunlight and an average light reflectance of 15% or less in the wavelength range of 5000 to 20000 nm after an exposure test under the following conditions: The surface of the reflective layer constituting the reflector has water impermeability, and the water impermeability coefficient of the reflector is 1.0×10 -11 m / sec or less, The back surface side facing the site surface and in contact with the site surface is a weed-control layer made of a weed-control sheet material, A solar power generation system, characterized in that the reflective layer and the weed-control layer are integrally laminated. Exposure test conditions Test equipment: Sunshine Weather Meter (Suga Test Instruments S80BBR) Black panel temperature: 63±3℃ Relative humidity: 50±5% Irradiance on sample surface: 255±10% w / m 2 (wavelength range 300-700 nm) Water spray cycle: water spray 18±0.5 minutes, water spray stop 102±0.5 minutes Irradiation time: 3000 hours

2. 2. The solar power generation system according to claim 1, wherein the light reflecting surface is white.

3. 2. The solar power generation system according to claim 1, wherein the light reflecting surface is formed of a metal layer.

4. 4. The solar power generation system according to claim 1, further comprising an ultraviolet degradation prevention layer on a surface of the reflective layer.

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