TW201946288A - Photovoltaic power generation system equipped with reflection mirror - Google Patents

Abstract

The present invention addresses the problem of providing a photovoltaic power generation system excellent in power generation efficiency and stable amount of power generation. The photovoltaic power generation system is characterized by being equipped with a reflection mirror provided at a position from which reflection is applied to a solar cell module and the light receiving surface of the solar cell module, wherein: a mirror surface reflectance when the wavelength of the reflection mirror is 800nm is 15% to 45%, inclusive; and a light beam transmittance when the wavelength of the reflection mirror is 800nm is 20% to 45%, inclusive.

Description

   Solar power generation system with reflector   

The present invention relates to a solar power generation system having a reflecting mirror.

In recent years, as alternative energy sources for petrochemical fuels such as petroleum and coal, various methods such as nuclear power generation, hydropower generation, wind power generation, and solar power generation have attracted attention. Among them, solar power generation, which directly converts solar energy into electrical energy, is highly anticipated as a green energy source.

Solar photovoltaic power generation is generally performed by a solar cell module having a structure in which a transparent front substrate / a transparent sealing material / a solar cell element / a sealing material / Protective sheet on the back of the solar cell. The sunlight shining on the light-receiving surface of the solar cell module reaches the solar cell element through the transparent front substrate and the transparent sealing material, and is converted into electrical energy in the solar cell element. The electrical energy obtained in this way is taken out to the outside through the wires connected to the solar cell element and is then supplied to various electrical appliances.

The amount of power generated by a solar cell module is usually proportional to the illuminance of sunlight reaching the solar cell element. Moreover, in a solar power plant represented by a large-scale solar power plant (Mega Solar), a general aspect is to connect about 10 solar cell modules in series, and a power conditioner Appropriate current and voltage values to operate as a solar power generation system.

In addition, it is known that the amount of power generated by a solar cell module is affected not only by the intensity of sunlight reaching the ground, but also by the height of the sun, so it will also vary depending on the installation angle of the solar cell module. Therefore, in order to increase the power generation of the solar power generation system, it is important to adjust the installation angle of the solar cell module according to the latitude and longitude of the installation environment, and to increase the amount of light incident on the solar cell element.

In recent years, a tracking system that changes the angle of a solar cell module in accordance with the height of the sun has been developed with the goal of increasing the annual cumulative power generation of a photovoltaic power generation system (Patent Document 1). In addition, a solar power generation system using a reflector for reflecting sunlight and collecting light to a solar cell module is also known (Patent Document 2).

    [Prior technical literature]         [Patent Literature]    

Patent Document 1 Japanese Patent Application Publication No. 2016-62931

Patent Document 2 Japanese Patent Laid-Open No. 2006-40931

However, in the tracking system of Patent Document 1, since the power generation amount per unit area of the solar cell module does not increase, the power generation efficiency is insufficient, and the increased output is often insufficient to meet the cost. In addition, the amount of power generated by photovoltaic power generation may become unstable due to weather conditions, time, and seasons, and a load may be imposed on the power generation system. In the solar power generation system described in Patent Document 2, since the light transmittance of the reflecting mirror is low, when the height of the sun is low, the sunlight is blocked by the reflecting mirror, and the light irradiated from behind the reflecting mirror cannot be used. Since it temporarily decreases, the power generation efficiency may become insufficient. In addition, in cloudy weather and other conditions, sunlight enters from all directions of the sky, so only mirrors with high specular reflectance and low light diffusivity may become insufficient in power generation efficiency.

Therefore, in view of the related prior art, the present invention has as its object to provide a photovoltaic power generation system excellent in power generation efficiency and stability in power generation amount.

In order to achieve the above-mentioned problems, the present invention includes the following configurations.

(1) A solar power generation system, comprising: a solar cell module; and a reflector provided at a position for irradiating reflected light to a light-receiving surface of the solar cell module; and a specular reflectance at a wavelength of 800 nm of the reflector. It is 15% or more and 45% or less, and the light transmittance of the reflector at a wavelength of 800 nm is 20% or more and 45% or less.

(2) The solar power generation system according to (1), wherein the light transmittance of the aforementioned mirror at a wavelength of 1,800 nm is 80% or more, and the average light transmittance of the aforementioned mirror at a wavelength of 1,200 nm or more and 1,400 nm or less Above 60% and below 80%.

(3) The solar power generation system according to (1) or (2), wherein the reflecting mirror includes a thin film composed of two types of layers mainly composed of a thermoplastic resin, and the two types of layers (a layer having a large refractive index is Among the layer A, the layer with a low refractive index is the layer B), the A layer and the B layer are alternately located in the thickness direction, and the total number of layers of the A layer and the B layer is 600 or more, and in accordance with JIS K 5600- 5-6: The test results of the peel strength between the A layer and the B layer measured in 1999 were classified as 0.

(4) The solar power generation system according to any one of (1) to (3), wherein the light-receiving surface of the reflector is incident at a light-incident angle of 30 ° to a light-receiving angle of 25 ° to 35 ° The maximum value of the average variable angle reflectance in the frequency band of 300nm to 1,200nm is 15% to 35%. When incident at an angle of 60 °, the wavelength of the light receiving angle is 55 ° to 65 ° and the wavelength is 300nm to 1,200nm. The maximum value of the average variable angle reflectance at the frequency band is 10% or more and 30% or less.

(5) The solar power generation system according to any one of (1) to (4), wherein the specular reflectance of the aforementioned mirror at a wavelength of 700 nm is 15% or more and 45% or less, and Light transmittance is 20% to 45%.

(6) The photovoltaic power generation system according to any one of (3) to (5), wherein the thermoplastic resin constituting the A layer contains polyalkylene terephthalate as a main component.

(7) The solar power generation system according to any one of (1) to (6), wherein the haze of the reflector is 4% or more and 30% or less.

(8) The solar power generation system according to any one of (3) to (7), wherein the reflecting mirror has a front substrate, a sealing material, and the A layer and the B layer alternately from the light receiving surface side in order. The multilayer film is located in the thickness direction and the total number of layers of the A layer and the B layer is 600 or more. The front substrate is made of any one of tempered glass, polycarbonate, and polymethyl methacrylate. In addition, the sealing material is mainly composed of any one of ethylene / vinyl acetate copolymer (EVA), transparent silicon, and polymethyl methacrylate.

(9) The solar power generation system according to (8), wherein the haze of the front substrate is 10% to 75%.

(10) The solar power generation system according to (8) or (9), wherein the surface of the multilayer film on the side opposite to the light-receiving surface has a UV-resistant layer.

According to the present invention, it is possible to provide a photovoltaic power generation system excellent in power generation efficiency and stability in power generation amount.

1‧‧‧solar battery module

2‧‧‧Reflector

3‧‧‧ Stand for Solar Cell Module

4‧‧‧ mirror stand

5‧‧‧multilayer film

6‧‧‧A floor

7‧‧‧B floor

8‧‧‧ front substrate

9‧‧‧sealing material

10‧‧‧UV resistant layer

11‧‧‧solar cell element

12‧‧‧ solar cell back protection sheet

FIG. 1 is a side view of a photovoltaic power generation system according to an embodiment of the present invention.

FIG. 2 is a top view of a photovoltaic power generation system according to an embodiment of the present invention.

3 is a top view of a photovoltaic power generation system according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view showing an example of a multilayer film used in a mirror.

FIG. 5 is a cross-sectional view showing an example of a reflecting mirror that can be used in the present invention.

6 is a cross-sectional view showing an example of a solar cell module that can be used in the present invention.

    [Form for Implementing Invention]    

Hereinafter, the photovoltaic power generation system of the present invention will be described in detail.

    <Solar Power Generation System>    

It is important that the photovoltaic power generation system of the present invention includes a solar cell module and a reflector provided at a position where the reflected light is irradiated to the light receiving surface of the solar cell module. By adopting this configuration, the solar cell module is irradiated with the solar light reflected by the reflector, so that more solar light reaches the solar cell element. Therefore, compared with a solar power generation system without a mirror, the power generation amount is increased.

The arrangement of the reflecting mirror is not particularly limited as long as the effect of the present invention is not impaired. From the viewpoint of increasing the amount of light reaching the solar cell element, it is preferable that the reflecting mirror is located on the light receiving surface of the solar cell module, as shown in FIG. 1, for example. And the light-receiving surface of the reflector faces the light-receiving surface of the solar cell module. By adopting such a configuration, most of the sunlight reflected by the reflector is incident on the light-receiving surface of the solar cell module, and the output of the solar cell module is improved. Here, the light-receiving surface refers to a surface located on the opposite side from the ground surface, and generally, sunlight is irradiated onto the light-receiving surface.

When the solar power generation system of the present invention is installed in a region north of the Tropic of Cancer, it is preferable to install the solar cell module with the light-receiving surface facing the south. With this configuration, the time for which the sun is positioned on the south side of the solar cell module becomes longer, so that more direct light can be incident on the solar cell element. On the other hand, from the same point of view, in a region located south of the Tropic of Cancer, it is preferable to install the light receiving surface of the solar cell module toward the north. In addition, the term “south side” here refers to not only the southward orientation, but also an orientation inclined 45 ° west or east from the southward orientation, and the same explanation is applied to the north side.

Although the solar power generation system of the present invention also varies according to the season and the latitude of the installed location, from the viewpoint of increasing the amount of sunlight reaching the solar cell element, the angle between the horizontal plane and the light-receiving surface of the mirror is preferably 5 ° to 50 °. When the angle between the horizontal plane and the light-receiving surface of the mirror is 5 ° or more, the reflected light generated by the mirror does not face the sky but toward the solar cell module, so the amount of reflected light incident on the solar cell module changes. many. On the other hand, when the included angle between the horizontal plane and the light-receiving surface of the mirror is 50 ° or less, sunlight becomes difficult to be blocked by the mirror, and the reduction in the amount of light directly incident on the solar cell module is suppressed.

Aiming at the preferred positional relationship between the solar cell module and the reflector in the solar power generation system of the present invention, an embodiment is shown for explanation. FIG. 1 shows a side view of a photovoltaic power generation system according to an embodiment of the present invention, and FIGS. 2 and 3 show top views of the photovoltaic power generation system according to an embodiment of the present invention. The present embodiment is presented as a specific example, and the present invention is not limited to this.

In the solar power generation system shown in Figs. 1 to 3, the solar cell module 1 is fixed by the stand 3 of the solar cell module so that the light receiving surface faces south, and the angle between the light receiving surface and the horizontal plane is 25 °. In addition, the reflecting mirror 2 is fixed in front of the light receiving surface of the solar cell module 1 by the mirror mount 4 so that the light receiving surface faces the north side, and the angle between the light receiving surface and the horizontal plane is 25 °. In addition, hereinafter, the stand 3 for solar cell modules and the stand 4 for mirrors may be collectively referred to as a stand.

At this time, if the height of the lower end of the reflecting mirror is consistent with the height of the lower end of the solar cell module, the reflected light generated by the reflecting mirror 2 will not be blocked by the back surface of the solar cell module 1 or the frame (not shown). It is preferable to reach the light receiving surface of the solar cell module 1 efficiently. In Figs. 1 to 3, the solar cell module and the mirror system are depicted in a parallel positional relationship in the long side direction, but it is not necessary to be parallel. The positional relationship can be appropriately adjusted according to the terrain of the place to be installed, etc. .

In FIGS. 1 to 3, the solar cell module 1 and the reflector 2 are each depicted as a rectangular parallelepiped, but as long as the effect of the present invention is not impaired, the surface may have unevenness, and the surface may be curved. In addition, the areas of the light-receiving surface of the solar cell module 1 and the light-receiving surface of the reflector 2 are not particularly limited as long as the effects of the present invention are not impaired, and a space can be considered for adjustment. For example, as shown in FIG. 2, the areas of the two may be equal, or as shown in FIG. 3, the areas of the two may be different (the example of FIG. 3 is that the area of the light-receiving surface of the reflector 2 is larger than that of the solar cell module 1 Big example.). When the areas of the two are equal to each other as shown in FIG. 2, it is not necessary to prepare a common member of a plurality of sizes for both, and there is an advantage that the manufacturing steps can be simplified or the cost can be reduced.

In addition, from the viewpoint of improving the rigidity to improve resistance to natural environments such as strong wind, it is also preferable that the mirror has a frame (not shown) at the end. From the viewpoint of improving rigidity, the frame is preferably made of metal such as aluminum, brass, silver, and copper. From the balance of rigidity and cost, aluminum is preferred.

The stands 3 and 4 preferably have a mechanism capable of adjusting the orientation of the solar cell module 1 or the light-receiving surface of the reflector 2 or the angle with respect to the horizontal plane (hereinafter, collectively referred to as an angle adjustment mechanism). The effect of improving the output using a mirror is affected by changes in the height of the sun based on the season. Therefore, it is easy to optimize the installation conditions of the solar cell module 1 or the reflecting mirror 2 by having the angle adjustment mechanism of the stands 3 and 4 in accordance with the change of the season. Output boost effect.

More specifically, in the summer when the sun height is high, in order to efficiently inject the sunlight reflected by the mirror 2 toward the light-receiving surface of the solar cell module 1, it is preferable to make the horizontal plane and the light-receiving surface of the mirror 2 The included angle becomes larger within the above-mentioned preferable range. This is because when the height of the sun is high, if the included angle between the horizontal plane and the light-receiving surface of the mirror 2 is small, the reflected light generated by the mirror 2 tends to move away from the light-receiving surface of the solar cell module 1. On the other hand, in winter where the height of the sun is low, from the above viewpoint, it is preferable to make the angle between the horizontal plane and the light-receiving surface of the mirror 2 smaller than in summer.

    <Reflector>    

In the solar power generation system of the present invention, in a state where the height of the sun is high, the sunlight is mainly irradiated on the light-receiving surface side, but if the height of the sun becomes low, the sunlight is also irradiated on the side opposite to the light-receiving surface. Therefore, in order to increase the power generation amount in a state where the height of the sun is high, it is preferable to increase the incident amount of light in a wavelength band that contributes to solar power generation to the solar cell module as much as possible, and contribute to the power generation amount. The specular reflectance of the mirror in the increased wavelength band is high. On the other hand, in order to maintain the power generation in a state where the height of the sun is low, it is necessary to increase the amount of light incident on the solar cell module in the same frequency band by specular reflection, and it is also necessary to make the sunlight from behind the mirror Transmit it to the module. Therefore, for a mirror, not only the specular reflectance in the same frequency band is required, but also the light transmittance in the same frequency band is required to be high. Generally speaking, the specular reflectance and the light transmittance are trade off. In addition, if we also consider that the height of the sun will change according to time or season, and to maximize the power generation of the solar power generation system, the balance between the specular reflectance and light transmittance of the light that contributes to the increase in power generation will be Become important.

From the above point of view, in the solar power generation system of the present invention, the specular reflectance of the mirror at a wavelength of 800 nm is 15% to 45%, and the light transmittance at a wavelength of 800nm is 20% to 45%. important. From the same viewpoint, the specular reflectance of the mirror at a wavelength of 800 nm is preferably 20% to 45%, and more preferably 25% to 45%. In addition, the light transmittance at a wavelength of 800 nm is preferably 20% to 40%, and more preferably 20% to 35%.

In addition, it is generally considered that light having a wavelength of 700 nm, which is higher than 800 nm, can be effectively used for contribution to power generation of, for example, an amorphous silicon solar cell element even when irradiated from behind the reflector. Preferably, the specular reflectance of the mirror at a wavelength of 700 nm is 15% to 45%, and the light transmittance at a wavelength of 700nm is 20% to 45%. From the same viewpoint, the specular reflectance at the wavelength of 700 nm of the mirror is more preferably 20% to 45%, and further preferably 30% to 45%. In addition, the light transmittance at a wavelength of 700 nm is more preferably 25% to 45%, and more preferably 30% to 40%.

From the same viewpoint, it is preferable that the average value of the specular reflectance at the wavelength of 400 nm to 700 nm of the mirror is 20% to 45%, and the average value of the light transmittance at the wavelength of 400nm to 700nm is 20% or more. Below 45%. In addition, it is more preferable that the average value of the specular reflectance at this wavelength band is 25% or more and 45% or less, and the average value of the light transmittance at this wavelength band is 25% or more and 45% or less. The average value of the specular reflectance at the frequency band is 30% to 40%, and the average value of the light transmittance at this wavelength band is 30% to 40%.

Set the specular reflectance at the wavelength of 800nm of the mirror at 15% to 45% or within the above-mentioned preferred range, and set the light transmittance at the wavelength of 800nm to 20% to 45% or below. In the best range, and set the specular reflectance at the wavelength of 700nm of the mirror at 20% to 45% or in the above-mentioned preferred range, and set the light transmittance at the wavelength of 700nm to 20% or more 45 % Or less, or a method within the above-mentioned preferred range, as long as the effect of the present invention is not impaired, there is no particular limitation. For example, a method using a mirror having a structure in which two layers having different refractive indices are alternately and repeatedly arranged (about The details will be described later.).

In addition, in the photovoltaic power generation system of the present invention, in terms of power generation efficiency and durability, the light transmittance at the wavelength of 1,800 nm of the reflector is preferably 80% or more. By adopting such an aspect, it is possible to reduce the influence of light in a wavelength band which does not contribute to power generation and deteriorates the performance or durability of the solar cell module. More specifically, light with a wavelength of 1,800 nm is light in the infrared region, and although it does not contribute to the power generation of almost all solar cell elements, it causes the temperature of the solar cell element or solar cell module to rise. In general, as the temperature of a solar cell module increases, the durability or the amount of power generation decreases. From the viewpoint of durability and the amount of power generation, it is preferable to reduce the incidence of light of this wavelength.

In addition, in the solar power generation system of the present invention, from the viewpoint of maintaining the power generation amount and durability and expanding the selection range of solar cell elements, it is preferable that the average wavelength of the mirror is 1,200 nm or more and 1,400 nm or less. The transmittance is 60% to 80%. Light having a wavelength of 1,200 nm or more and 1,400 nm or less is also light in the infrared region, which increases the temperature of solar cell elements and solar cell modules. Moreover, in the most common crystalline silicon solar cell elements of solar cells, light in a wavelength range of 400 nm to 1,150 nm is helpful for power generation, and in amorphous silicon solar cell elements, light in a wavelength range of 300 nm to 700 nm is helpful. For power generation, light with a wavelength above 1,200 nm and below 1,400 nm hardly contributes to power generation. Therefore, the average light transmittance at the wavelengths of the mirror above 1,200nm and below 1,400nm is 60% or more, which can reduce the reflection of light in the same wavelength band generated by the mirror or the resulting light toward the solar cell mode. The solar power generation system is equipped with a solar cell module using the solar cell elements exemplified above, and the power generation amount and durability of the solar cell module can be maintained.

However, on the other hand, there are also gallium arsenic multi-junction solar cell elements that contribute to power generation, such as light having a wavelength of 350 nm to 1,750 nm. The power generation amount is increased by light having a wavelength of 1,200 nm to 1,400 nm Solar cell element. Therefore, the average light transmittance of the reflector at a wavelength of 1,200 nm to 1,400 nm can be 80% or less, and reflection can be obtained also in a solar power generation system including a solar cell module using such a solar cell element. Mirror effect.

The method of setting the light transmittance of the mirror at a wavelength of 1,800 nm to 80% or more and the average light transmittance of 1,200 nm to 1,400 nm or less to 60% to 80% is not a problem as long as the effect of the present invention is not impaired. Specific restrictions include, for example, setting the specular reflectance of the mirror at a wavelength of 800 nm to 15% or more and 45% or less, or setting the light transmittance at a wavelength of 800 nm to 20%. Above 45% or less is the same method as the above-mentioned preferred range.

In the photovoltaic power generation system of the present invention, from the viewpoint of power generation improvement when the height of the sun is low, it is preferable that the light receiving angle is 25 ° with respect to the light receiving surface of the reflector at an incident angle of 30 °. The maximum value of the average variable angle reflectance at a wavelength range of 300nm to 1,200nm to 35 ° is 15% to 35%, and the average variable angle at a wavelength range of 300nm to 1,200nm when incident at an angle of 60 ° The maximum reflectance is 10% to 30%. The average variable angle reflectance is an average value of reflectance measured at a reflection angle of 25 ° to 35 ° (or 55 ° to 65 °) at a frequency band of 300 nm to 1,200 nm. The maximum reflectance of the average value is called Is the maximum value of the average variable angle reflectance. The specular reflection, diffuse reflection, and transmission of light are generally offset. Specular reflection is important when the sun's height or solar illuminance is high. On the other hand, when the sun's height or solar illuminance is low, diffuse reflection and transmission become important. From the viewpoint of power generation stability, the balance between specular reflection, diffuse reflection, and transmission is important. The larger the maximum value of the average variable angle reflectance, the higher the degree of specular reflection, and the lower the light transmittance and light scattering. From the foregoing point of view, the maximum value of the average variable angle reflectance becomes an indicator of power generation improvement and power generation amount stability.

With this aspect, the transmittance and diffuse reflection of sunlight at a low solar height are promoted, and the power generation of the solar power generation system is improved at a low solar height. The method of obtaining the average variable-angle reflectance and the maximum value of the average variable-angle reflectance is as described in the item [Production of a mirror, measurement method and evaluation method of characteristics] (11) in the examples.

From the same viewpoint, it is more preferable that the average value of the average variable angle reflectance at a wavelength of 300 to 1,200 nm with a light receiving angle of 25 ° to 35 ° with respect to the light receiving surface of the mirror is incident at a 30 ° incident angle. The maximum value of the average variable angle reflectance at a wavelength of 300 nm to 1,200 nm when the incident angle is 60% or more and 26% or less and 25% or less is 25% or more and 30% or less.

The average variable-angle reflectance can be measured by using a UV-3600Plus manufactured by Shimadzu Corporation and mounting a variable-angle mask unit. In addition, as a means for setting the maximum value of the average variable-angle reflectance within the above-mentioned preferable range, for example, the use of a layer A and a layer B having a thermoplastic resin as a main component in the reflector is alternately located in the thickness direction. On multilayer films. By adopting such an aspect, the variable angle reflectance can be appropriately adjusted, and the mirror can have the aforementioned characteristics.

In the solar power generation system of the present invention, it is preferable that the reflector includes a thin film composed of two types of layers containing a thermoplastic resin as a main component, and the two types of layers (the layer with a large refractive index is A layer and the refractive index is Among the small layers is the B layer), the A layer and the B layer are alternately located in the thickness direction, and the total number of layers of the A layer and the B layer is 600 or more. With this configuration, it is easy to control the specular reflectance of the mirror at a wavelength of 800 nm, the light transmittance at a wavelength of 800 nm, 1,800 nm, and the average light transmittance at a wavelength of 1,200 nm or more and 1,400 nm or less. Within the aforementioned range. As a result, the power generation amount and durability of the photovoltaic power generation system are improved. In addition, when a thermoplastic resin is used as a main component, it means that when the entire layer is 100% by mass, a thermoplastic resin containing 90% by mass or more and 100% by mass or less is included.

The A layer and the B layer can alternately exist in the thickness direction, and the specular reflectance of the mirror can be improved in a specific wavelength band. The wavelength band (main reflection wavelength: λ) at which reflection is performed is determined based on the following formula A, and can be controlled by adjusting the thickness and refractive index of each layer.

Formula A: λ = 2 × (na × da + nb × db)

na: average in-plane refractive index of layer A

nb: in-plane average refractive index of the B layer

da: layer thickness of layer A (nm)

db: layer thickness of layer B (nm)

λ: main reflection wavelength (nm).

“Layer A and B are alternately located in the thickness direction” refers to a state where the laminated constitution of the A layer and the B layer repeatedly exists when a cross section parallel to the thickness direction is observed. In addition, as long as the reflection mirror does not impair the effect of the present invention, the layer A and B layers are repeatedly formed, and the layer does not belong to the layers A and B, or the continuous portion of the A or B layer exists. .

The reflectance can be controlled by the refractive index difference between the A layer and the B layer, and the number of layers of the A layer and the B layer. More specifically, the reflectance can be increased by increasing the refractive index difference between the A layer and the B layer and increasing the total number of layers of the A layer and the B layer.

By setting the total number of layers of the A layer and the B layer to 600 or more, the reflector becomes a person having high light reflection performance to a degree that can improve the power generation of the solar cell module. The upper limit of the total number of layers of the A layer and the B layer is not particularly limited as long as the effect of the present invention is not impaired, and it is 1,200 in terms of the effect of increasing the light reflectance as the number of layers increases and the cost. That is, the total number of layers of the A layer and the B layer is preferably 600 or more and 1,200 or less from the viewpoint of considering both improvement in the reflection performance of the mirror and reduction in manufacturing cost.

Examples of the thermoplastic resin that can be used as the main component of the A layer of the reflector of the photovoltaic power generation system of the present invention (hereinafter, referred to as a thermoplastic resin A) include crystalline polyterephthalic acid. Crystalline polyesters such as ethylene glycol and crystalline polyethylene naphthalate. Examples of the thermoplastic resin that can be used as the main component of the layer B (hereinafter referred to as the thermoplastic resin B) include amorphous polyethylene terephthalate and amorphous polyethylene naphthalate. Amorphous polyesters such as ethylene glycol, fluorine-based elastomers, and the like. Here, the crystalline property refers to a characteristic that an exothermic peak accompanied by crystallization is observed when a polymer is gradually cooled after being heated and melted to melt and solidify, and the amorphous property refers to a polymer When the temperature was raised to melt and slowly cooled to solidify, the characteristics of the exothermic peak were not observed because crystallization did not occur. The combination of the thermoplastic resin A and the thermoplastic resin B, and the composition of the A layer and the B layer can be freely selected as long as the refractive index of the A layer is larger than that of the B layer, so long as the effect of the present invention is not impaired.

The method of forming the reflector in which the A layer and the B layer are alternately positioned in the thickness direction and the total number of layers of the A layer and the B layer is 600 or more is not particularly limited as long as the effect of the present invention is not impaired. The method described.

First, the thermoplastic resin A and the thermoplastic resin B heated and melted by different extruders are fed into a feed block so that they are laminated alternately so that the total number of layers becomes 600 or more, and then they are removed from the mold. It was discharged onto a casting drum, cooled and solidified, and an orientation-free sheet was obtained. Thereafter, this non-oriented sheet is uniaxially or biaxially stretched to produce a multilayer film having a structure as shown in FIG. 4, and this multilayer film is assembled in a reflector, whereby the reflector can be made into layer A and The B layers are alternately located in the thickness direction, and the total number of layers of the A layer and the B layer is 600 or more. FIG. 4 is a cross-sectional view showing an example of a multilayer film used in a mirror. Reference numeral 5 in FIG. 4 indicates a multilayer film, reference numeral 6 indicates an A layer, and reference numeral 7 indicates a B layer. At this time, since the thickness of each layer can be adjusted in the shape of the slit (length, width) by using the feed block, it is also easy to achieve an arbitrary layer thickness.

In the case where the A layer and the B layer are alternately positioned in the thickness direction in the reflector, it is preferable to classify the test results of the peel strength between the A layer and the B layer measured in accordance with JIS K 5600-5-6: 1999. Is 0. According to the classification of the test results of the peel strength between the A layer and the B layer measured according to JIS K 5600-5-6: 1999, the more excellent the interlayer adhesion strength between the A layer and the B layer, the smaller the value.

When the photovoltaic power generation system of the present invention is installed, the mirror system is exposed to the same natural environment as the solar cell module, and therefore is subjected to stress caused by temperature and humidity cycles and ultraviolet rays. The classification of the test results of the peel strength between the A layer and the B layer is 0, and the interlayer peeling of the A layer and the B layer due to these stresses can be reduced. As a result, the performance of the mirror can be maintained for a long period of time. .

The means for classifying the test results of the peel strength between the A layer and the B layer measured in accordance with JIS K 5600-5-6: 1999 into 0 in a reflector is not particularly limited as long as the effect of the present invention is not impaired. For example, a method of adjusting the composition of the A layer and the B layer such that the absolute value of the difference between the Hansen solubility parameter of the A layer and the Hansen solubility parameter of the B layer is 3.0 MPa ^1/2 or less. Hereinafter, the solubility parameter of Hansen may be referred to as HSP. When the A layer is composed of a single component, the HSP of the component is referred to as the HSP of the A layer. When the A layer is composed of plural components, the HSP of the most contained component in the A layer is referred to as the HSP of the A layer. . The same explanation applies to the HSP of layer B.

HSP is an index indicating the degree to which a substance is soluble in other substances, and the solubility is represented by a three-dimensional vector. This three-dimensional vector can be represented by a dispersion term (δ _d ), a polarity term (δ _p ), and a hydrogen term (δ _h ). On the other hand, the closer the vector is, the higher the solubility can be determined.

HSP can be calculated using the solubility parameter estimation software based on the method described in Hansen Solubility Parameters, A User's Handbook by Charles M. Hansen, CRC Press Boca Raton F1 (2007). For the solubility parameter estimation software, for example, Hansen Solubility Parameters in Practice (HSPiP, developed by Charles M Hansen, Steven Abbott, etc.) can be used. The HSPiP is equipped with a function for calculating the absolute value of the difference between the two components of HSP, and a library containing HSP of various substances including resin.

Hereinafter, a method for obtaining the absolute value of the difference between the HSP of the A layer and the HSP of the B layer will be specifically described. First, to 1 g of the resin constituting the A layer and the B layer (the resin with the largest content in the case of plural components), 15 kinds of solvents (water, acetone, 2-butanone, cyclopentanone, isopropyl) were added in small amounts one by one. Alcohol, ethanol, 1-octanol, toluene, hexane, acetic acid, butyl acetate, aniline, methanamine, 2-aminoethanol, and 2-butoxyethanol) until the resin raw material is completely dissolved or the solvent The amount reaches 99g, and the saturated solution concentration at this time is obtained in 6 stages (6: insoluble, 5: mass percentage concentration less than 5%, 4: mass percentage concentration more than 5% and less than 10%, 3: mass percentage concentration 10% Above and less than 30%, 2: mass percentage concentration of 30% to less than 50%, 1: mass percentage concentration of 50% or more) indicates the solubility of each solvent. Here, "6: insoluble" refers to a case where an undissolved resin raw material is observed even if the amount of the solvent reaches 99 g. Next, the obtained data is input to HSPiP, and the absolute value of the difference between the HSP of layer A and the HSP of layer B is obtained. The absolute value (R) of the difference between the HSP of the A layer and the HSP of the B layer is the HSP of the A layer (δ _dA , δ _pA , δ _hA ), and the HSP of the B layer is (δ _dB , δ _pB , δ _hB ) can be calculated by the following formula B.

Formula B: R ² = 4 × (δ _dB -δ _dA ) ² + (δ _pB -δ _pA ) ² + (δ _pB -δ _pA ) ²

By setting the absolute value of the difference between the HSP of the A layer and the B layer to 3.0 MPa ^1/2 or less, the interlayer adhesion strength between the A layer and the B layer can be enhanced. On the other hand, if the absolute value of the difference between the HSP of the A layer and the B layer becomes too small, in the process of manufacturing a multilayer film having the A layer and the B layer, the resin composition used to obtain each layer is mixed, and the The interface becomes unclear and the specular reflectance becomes small. From the point of clarifying the interface between the layers to avoid a decrease in the specular reflectance, the absolute value of the difference in HSP between the A layer and the B layer is preferably 0.01 MPa ^1/2 or more.

Examples in which the absolute value of the difference between the HSP of the A layer and the B layer is 0.01 MPa ^1/2 or more and 3.0 MPa ^1/2 or less may include the use of crystalline polyethylene terephthalate (hereinafter, referred to as In the case of PET.) A resin is used as the thermoplastic resin A, and an amorphous polyester resin is used as an example of the thermoplastic resin B. The amorphous polyester resin used as the thermoplastic resin B is preferably an amorphous polyester resin containing a spiroglycol unit. The amorphous polyester resin containing a spiroglycerol unit has a small difference in glass transition temperature from the crystalline polyethylene terephthalate. Therefore, since the thermoplastic resin B is an amorphous polyester resin containing a spiroglycerol unit, it is possible to reduce excessive stretching or interlayer peeling during molding.

In addition, in the solar power generation system of the present invention, from the viewpoint of light resistance, it is preferable that the A layer contains polyalkylene terephthalate as a main component. By adopting such a configuration, the peel strength between the A layer and the B layer can be improved, and a solar power generation system having high durability can be obtained. In addition, since the ultraviolet absorption is small, a solar power generation system having high light resistance can be obtained. From the same viewpoint, it is more preferable that the A layer contains polyethylene terephthalate as a main component. In addition, from the same viewpoint, it is preferable that the B layer contains polyethylene terephthalate as a main component, and it is more preferable that the B layer contains polyethylene terephthalate as a main component.

In the case of using an amorphous polyethylene terephthalate as the amorphous polyester resin of the thermoplastic resin B, as long as the effect of the present invention is not impaired, the amorphous polyethylene terephthalate can also be used in its molecular chain. Dicarboxylic acid units other than terephthalic acid units and glycol units other than ethylene glycol units are included. Examples of such a copolymerization unit include, in addition to the aforementioned spiroglycerin unit, a cyclohexanedicarboxylic acid unit, a cyclohexanedimethanol unit, and the like. In addition, the content thereof is not particularly limited, and it is preferable to set the total dicarboxylic acid unit to 100 mol% or less to 25 mol% or to set the total diol unit to 100 mol%. At 25 mol% or less.

In addition, in the photovoltaic power generation system of the present invention, the haze of the aforementioned reflector is preferably from the viewpoint of reducing the variation in the power generation amount by increasing the power generation amount at low illumination and low solar height. It is 4% or more and 30% or less. Changes in the amount of power generation and the like can be performed by evaluating the output increase rate of a solar cell module described later. The output increase rate at low illumination and low solar height is more preferably 2% to 10%, and more preferably 4% to 8%. In addition, the variation in power generation amount (difference in the rate of increase in output) is preferably 5% or more and 20% or less.

As the haze of the aforementioned reflecting mirror is 4% or more, the scattering of light generated by the mirror is improved. Under cloudy weather conditions, such as cloudy days, the incident light is radiated from all directions throughout the day. By using a highly scattering mirror, it is possible to utilize light incident from various directions. As a result, the output of the solar power generation system in weather conditions such as cloudy days with low solar illumination is promoted.

In addition, since the specular reflectance of the reflecting mirror and the haze value are in a trade-off relationship, the haze of the reflecting mirror can be appropriately selected so that the specular reflectance of the reflecting mirror can obtain the aforementioned preferred range. From this point of view, the haze of the reflector is preferably 30% or less. By adopting such a configuration, the output of the photovoltaic power generation system under a weather condition such as a sunny day with high solar illumination is promoted. From the same viewpoint, the haze of the reflector is more preferably 5% or more and 20% or less, and still more preferably 5% or more and 10% or less.

The haze can be measured using a haze meter NDH4000 (Nippon Denshoku) in accordance with the method described in JIS K7136: 2000, and the transmission haze at the time of 0-degree injection.

Hereinafter, an example of a layer configuration of a mirror will be described with reference to FIG. 5. FIG. 5 is a cross-sectional view showing an example of a reflecting mirror that can be used in the present invention. The reflector shown in FIG. 5 has a configuration in which a front substrate 8, a sealing material 9, a multilayer film 5, and a UV-resistant layer 10 are sequentially located from a light-receiving surface side.

In order to make the reflector strong enough to withstand long-term installation, it is preferable to have a structure having a front substrate on the light-receiving surface of the reflector. The front substrate 8 acts to impart rigidity and impact resistance to the mirror. In addition, the haze of the reflector can be adjusted by having the front substrate 8. In addition, the haze of a mirror that combines the front substrate 8, the sealing material 9, the multilayer film 5, and the UV-resistant layer 10 can be appropriately adjusted by the haze of each component. Among the above components, the haze of the front substrate 8 has the greatest influence on the haze of the reflector.

From the viewpoint of a preferable range of the haze of the reflector, the haze of the front substrate is preferably 10% or more and 75% or less, and more preferably 30% or more and 60% or less. As a means for making the haze of the reflector 4% or more and 30% or less, it is preferable to use a haze of The front substrate of 10% to 75% uses a multilayer film having a haze of 1% to 15% and a sealing material to integrate them.

As the front substrate 8, tempered glass, polycarbonate, polymethyl methacrylate, and the like can be used. Among them, tempered glass is preferably used from the viewpoint of rigidity and durability.

The sealing material 9 plays a role of close contact between the front substrate 8 and the multilayer film 5 and protects the multilayer film 5 from ultraviolet rays or impact. The sealing material 9 can be, for example, ethylene vinyl acetate copolymer (EVA), transparent silicon, methyl methacrylate, or the like, and may further contain one or more kinds of ultraviolet absorbers as needed, Additives such as light stabilizers, crosslinking agents, and silane coupling agents. Various additives can be used by a publicly known one, and the types and combinations thereof can be freely selected within a range that does not impair the effects of the present invention.

In addition, in the photovoltaic power generation system of the present invention, from the viewpoint of protecting the mirror from ultraviolet rays and impact, it is preferable to have a front substrate, a sealing material, and the A layer and A multilayer film in which the B layer is alternately located in the thickness direction and the total number of the A layer and the B layer is 600 or more. The front substrate is made of reinforced glass, polycarbonate, polytetrafluoroethylene, and polymethacrylic acid. Any one of methyl esters is a constituent component, and the sealing material is mainly composed of any one of ethylene / vinyl acetate copolymer (EVA), transparent silicon, and polymethyl methacrylate. From a viewpoint, it is more preferable that the front substrate is tempered glass and the sealing material is EVA.

The UV-resistant layer 10 plays a role of reducing deterioration of the multilayer film 5 from the back side due to scattered light from the sun or light reflected from the ground. When the multilayer film 5 is deteriorated from the back side, the performance of the mirror may be reduced due to cracks, precipitation of oligomers, and the like. From the viewpoint of weather resistance, the UV-resistant layer 10 preferably contains an acrylic resin and an ultraviolet absorber. The acrylic resin is not particularly limited as long as the effects of the present invention are not impaired. From the viewpoints of weather resistance and adhesion to the multilayer film 5, an acrylic urethane resin is preferred. Among these, from the viewpoints of curability and heat resistance of the resin, an acrylic urethane resin having a structure in which an acrylic polyol resin and an isocyanate are crosslinked is more preferred. In addition, a known ultraviolet absorber can be used as long as the effect of the present invention is not impaired. The method for forming the UV-resistant layer 10 is not particularly limited as long as the effect of the present invention is not impaired, and it can be formed by, for example, a known coating method or the like.

Further, in the solar power generation system of the present invention, from the viewpoint of protecting it from ultraviolet rays reflected from the ground, it is preferable to have a UV-resistant layer on the opposite side of the light-receiving surface of the multilayer film. Discoloration can be suppressed by setting it as such. Since the diffuse reflectance may be reduced in the range of about 500 nm to about 1,000 nm due to the discoloration of the mirror, the reduction of the power generation amount is promoted by having a UV-resistant layer. The UV-resistant layer may contain a known ultraviolet absorber, and the types and combinations thereof can be freely selected within a range that does not impair the effects of the present invention.

    <Solar Cell Module>    

The solar cell module in the photovoltaic power generation system of the present invention is not particularly limited as long as the effect of the present invention is not impaired, and a known one can be used. As a specific example, as shown in FIG. 6, a solar cell element 11 that converts solar light energy into electrical energy is disposed between the front substrate 8 on the light-receiving surface side and the protective sheet 12 on the back surface of the solar cell. The constituent member between the front substrate 8 and the solar cell back surface protective sheet 12 is sealed with a sealing material 9.

The front substrate 8 and the sealing material 9 can be the same as those of the aforementioned reflector. The solar cell element 11 can be applied to silicon based systems such as monocrystalline silicon, polycrystalline silicon, and amorphous silicon, copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, and gallium-arsenic. Various well-known solar cell elements, such as -V-group, II-VI compound semiconductor systems, compound multi-junction systems such as gallium-arsenic multi-junction systems, but polycrystalline silicon is preferably used from the viewpoint of power generation efficiency or cost.

The solar cell back surface protective sheet is not particularly limited as long as the effect of the present invention is not impaired, and a known one can be used. More specifically, a fluorine film, a polyester film, a polyolefin film, and a plurality of these can be bonded together. In addition, the solar cell back surface protective sheet can be made into a form having a layer containing white particles for improving the reflectance, or made into a form having an easy-to-adhere layer in order to enhance the adhesion with other members.

    [Example]    

Hereinafter, examples of the present invention will be described, but the present invention is not necessarily limited to these examples.

    [Making Reflector, Measuring Method and Evaluation Method of Characteristics]    

The production of the mirror and the measurement or evaluation shown in the examples were performed under the following conditions.

    (1) Production of mirrors    

Each member (to be described later) constituting a reflecting mirror is sequentially laminated from the light-receiving surface. This laminated body is put into a vacuum laminator with a hot plate temperature of 145 ° C, degassed for 4 minutes, and then pressurized at a pressure of 1 kgf / cm ² minute. After that, the thermoplastic resin that overflowed during the stacking was removed, and the aluminum frame was integrated with a silicon sealant.

    (2) specular reflectance of mirror    

The relative spectral reflectance of the mirror was measured using a UV-3600Plus manufactured by Shimadzu Corporation, with a wavelength of 700 nm to 900 nm at a pitch of 1 nm. When measuring the spectral reflectance, barium sulfate was used as a reference plate. After measuring the relative spectral reflectance, measure the relative spectral diffuse reflectance in the same wavelength range, and obtain the difference between the relative spectral reflectance and the relative spectral diffuse reflectance at a wavelength of 800 nm to obtain the specular reflectance (%) at a wavelength of 800 nm. ). The specular reflectance at a wavelength of 700 nm is obtained in the same manner by obtaining the difference between the relative spectral reflectance and the relative spectral diffusion reflectance at a wavelength of 700 nm.

    (3) Light transmittance of mirror    

The UV-3600Plus manufactured by Shimadzu Corporation was used to measure the spectral transmittance of the reflector at a wavelength of 1 nm in the range of 700 nm to 1,800 nm. From the obtained data, the values at the wavelengths of 700 nm, 800 nm, and 1,800 nm were taken as the light transmittances (%) at the wavelengths of 700 nm, 800 nm, and 1,800 nm, respectively. In addition, the average of the measured values in the range of 1,200 nm to 1,400 nm was calculated, and this was taken as the average light transmittance (%) at a wavelength of 1,200 nm to 1,400 nm.

    (4) Output improvement rate of solar cell module    

The two I-V Checker MP-11 mechanisms used by Inho Seiki are used to simultaneously evaluate the power generation of a photovoltaic system with a mirror and a photovoltaic system without a mirror. The difference between the maximum output value obtained when the mirror is installed and the maximum output value obtained when the mirror is not provided is obtained, and the ratio of the maximum output to the case where the mirror is not provided is calculated based on the difference. (%), Which is used as the output increase rate due to the mirror. The measurement was performed when the solar height was about 60 ° (58 ° to 65 °) and when the solar height was about 26 ° (21 ° to 30 °).

    (5) Light-shielding test of a mirror (evaluation of output of a solar cell module where sunlight is blocked by the mirror)    

After measuring the output of a single cell crystalline silicon module (cell size: 156mm x 156mm) according to JIS C 8914: 2005, the mirror is closely attached to the light receiving surface side of the single cell crystalline silicon module to cover the entire module. In the form of a light receiving surface, the output measurement is performed again. Calculate the ratio of the output when the mirror is in close contact with the output when the mirror is not in close contact. At this time, if the output of the case where the mirror is not brought into close contact is 20% or more, it is considered to be a pass.

    (6) Peel strength test (cross-cut test: when the film for reflective members is a multilayer film only)    

A cross-cut test was performed on a film to be described later by a method according to JIS K 5600-5-6: 1999. First, a 5 cm square test plate was sampled from the film. Thereafter, the surface of the test plate was cut six times at intervals of 1 mm to penetrate the surface of the test plate. Furthermore, in a manner capable of forming a lattice pattern, the cuts are rotated by 90 ° with respect to the cuts, and only an equal number of parallel cuts are made to overlap the cuts. On the surface of the test plate, the grid pattern was produced at three different locations. In addition, a tape according to JIS K 5600-5-6: 1999 was cut into small pieces having a length of about 75 mm. The center of the tape was placed on the grid in a direction parallel to one of the cuts, and the area covering the grid part was 25 mm in length, and the tape was flattened with a finger. After that, grasp one end of the tape at an angle close to 60 ° and tear it off within 1.0 second. The number of peeled grids in the above-mentioned grid pattern was counted, and the average value of the number of peeled grids in the grid pattern at three locations was taken as the test result. The test results are classified according to JIS K 5600-5-6: 1999, with 6-stage evaluation from 0 to 5. 0 means that the adhesion between the A layer and the B layer is the strongest.

    (7) Number of layers (only when the film for reflective members is a multilayer film)    

The layer structure of the multilayer film was determined by observing a sample cut out with a microtome using a transmission electron microscope (TEM). Using a transmission electron microscope H-7100FA (manufactured by Hitachi, Ltd.), a cross-sectional photograph of the film was taken at an acceleration voltage of 75 kV, and the layer composition was measured.

    (8) Refractive index of layer A and layer B (only when the film for reflective members is a multilayer film)    

The measurement was performed using a film containing only the thermoplastic resin A and a film containing only the thermoplastic resin B in accordance with the A method described in JIS K7142: 2008. Among the obtained refractive indices, the average refractive indices in two directions orthogonal to each other on the film surface were taken as the respective refractive indices.

    (9) Absolute value of the difference between Hansen's solubility parameter (HSP), HSP of layer A and HSP of layer B    

To 1 g of the resin constituting the A layer and the B layer, 15 kinds of solvents (water, acetone, 2-butanone, cyclopentanone, isopropanol, ethanol, 1-octanol, toluene, hexane, acetic acid, Butyl acetate, aniline, methanamine, 2-aminoethanol, and 2-butoxyethanol) until the resin raw material is completely dissolved or the solvent amount reaches 99 g. The saturated solution concentration at this time is obtained in 6 stages (6: insoluble, 5: mass percentage concentration less than 5%, 4: mass percentage concentration of 5% or more and less than 10%, 3: mass percentage concentration of 10% or more and less than 30% , 2: mass percentage concentration of 30% or more and less than 50%, 1: mass percentage concentration of 50% or more) indicates the solubility of each solvent. Then, input the obtained data into Hansen Solubility Parameter in Practice (HSPiP) ver.3.1.17 (developed by Charles M Hansen, Steven Abbott, etc.), and calculate the HSP of layer A and layer B by the following formula B The absolute value (R) of the difference in HSP. Further, "6: insoluble" means even if the vehicle reached the resin was observed 99g undissolved material, the HSP A layer is expressed as _{(δ dA, δ pA, δ} hA), HSP B layer is represented as the (δ _dB , δ _pB , δ _hB ).

Formula B: R ² = 4 × (δ _dB -δ _dA ) ² + (δ _pB -δ _pA ) ² + (δ _pB -δ _pA ) ²

    (10) Haze    

The haze of the front substrate or the mirror was measured using a haze meter NDH4000 (Nippon Denshoku) in accordance with the method described in JIS K7136: 2000. The transmission haze was measured at a 0-degree incidence.

    (11) Maximum value of average variable angle reflectance    

The UV-3600Plus manufactured by Shimadzu Corporation is equipped with a variable-angle optical unit and a reflector for evaluation is provided. The incident angle of incident light is fixed at 30 ° (or 60 °), and the wavelength ranges from 300nm to 1,200nm. Within the range, the reflectance within a range of reflection angles of 25 ° to 35 ° (or 55 ° to 65 °) (reflection angle is in units of 1 °) is measured at 1 nm intervals. Then, the average value of each reflectance at a reflection angle of 25 ° to 35 ° (or 55 ° to 65 °) at 300nm to 1,200nm is calculated, and it is taken as the average variable angle reflectance at that angle. Among the average variable angle reflectances with a reflection angle of 25 ° to 35 ° (or 55 ° to 65 °), the largest value is taken as the maximum value of the average variable angle reflectance at an incident angle of 30 degrees (or an incident angle of 60 degrees). Here, the incident angle is an angle formed by the incident light and the light-receiving surface of the mirror, and the closer the incident angle is to 90 degrees, the closer the angle of incidence to the light-receiving surface of the mirror is. An incident angle of 30 degrees is assumed to be when the height of the sun is low, and an incident angle of 60 degrees is assumed to be measured when the height of the sun is high. Moreover, a barium sulfate board was used as a reference board.

    (12) The difference in the output improvement rate of the solar cell module    

The difference between the two output improvement rates (in the case where the solar height is about 60 ° and about 26 °) measured in the above (4) is obtained as the difference in the output improvement rate.

    [Thermoplastic resin]         (Thermoplastic resin A)    

Crystalline polyethylene terephthalate (F20S manufactured by Toray Co., Ltd., crystal melting temperature: 255 ° C, crystal melting heat: 41mJ / mg, crystallization temperature: 155 ° C).

    (Thermoplastic resin B1)    

Amorphous copolymerized polyester (dicarboxylic acid unit: terephthalic acid unit / cyclohexanedicarboxylic acid unit = 76.0mol% / 24.0mol%, glycol unit: ethylene glycol unit / spiroglycerol unit = 79.0mol% / 21.0 mol%).

    (Thermoplastic resin B2)    

Amorphous copolymerized polyester (dicarboxylic acid unit: terephthalic acid unit / cyclohexanedicarboxylic acid unit = 83.2mol% / 16.8mol%, glycol unit: ethylene glycol unit / spiroglycerol unit = 85.3mol% / 14.7mol%).

    (Thermoplastic resin B3)    

Amorphous copolymerized polyester (PETG6763 by Eastman, dicarboxylic acid unit: terephthalic acid unit = 100.0mol%, glycol unit: ethylene glycol unit / cyclohexanedimethanol unit = 70.0mol% / 30.0mol% ).

    (Thermoplastic resin B4)    

Polymethyl methacrylate (purchased from Plaskolite, Columbus, Ohio. Trade name: CP-80).

    (Manufacture of thermoplastic resins B1 and B2)    

First, 60.9 parts by mass of dimethyl terephthalate and 19.8% by mass of dimethyl 1,4-cyclohexanedicarboxylate with a cis / trans ratio of 72/28, 49.7 parts by mass of ethylene glycol, and 28.1 parts by mass of glycerin, 0.04 parts by mass of manganese acetate tetrahydrate, and 0.02 parts by mass of antimony trioxide were mixed. Next, the obtained mixture was dissolved and stirred at 150 ° C., and the temperature of the reaction content was gradually raised to 235 ° C. while stirring, so that methanol was distilled off. After a predetermined amount of methanol was distilled off, an ethylene glycol solution containing 0.02 parts by mass of trimethylphosphoric acid was added, and the transesterification reaction was completed by stirring for 10 minutes. Thereafter, the obtained transesterification reaction product was transferred to a polymerization apparatus, and the polymerization was carried out under reduced pressure and temperature while stirring to distill off ethylene glycol (polymerization took 90 minutes, and the pressure was reduced from normal pressure to 133 Pa or less, and from 235 at the same time) The temperature was raised to 285 ° C.). After the completion of the polymerization, the discharge port at the lower part of the polymerization apparatus was opened, and the contents of the polymerization apparatus were discharged to a water tank, which was cooled in the water tank and cut with a blade to prepare chips of thermoplastic resin B1. The thermoplastic resin B2 had a composition of raw materials of 66.7 parts by mass of dimethyl terephthalate and a cis / trans ratio of 72/28 of dimethyl 1,4-cyclohexanedicarboxylate of 13.9% by mass. Except for 53.6 parts by mass of ethylene glycol and 19.7 parts by mass of spiroglycerin, it was produced in the same manner as the thermoplastic resin B1.

    [Thin film for reflective member]         (Film 1 ~ 5)    

The multilayer film shown in Table 1 was used. The composition of each layer in Table 1 was calculated by setting all the components constituting each layer to 100% by mass.

    (Film 6 ~ 8)    

Film 6: A multilayer film "ESR" manufactured by 3M Corporation was used.

Film 7: An Al-deposited PET film "Metalumy" (registered trademark) S (# 25) (thickness: 25 µm) manufactured by Toray Film Processing Co., Ltd. was used. Film 8: White PET film "Lumirror" (registered trademark) E20 (# 50) (thickness: 50 μm) manufactured by Toray Co., Ltd.

    (Film 9)    

The method for adjusting the base material and the coating material using the coating material adjusted by using the following base material to form a UV-resistant layer on one side of the film 1 and the method for forming the UV-resistant layer are as follows. The thin film 9 is a light-receiving surface using a surface opposite to the surface on which the UV-resistant layer is formed.

Adjustment of base agent: UC CLEAR BS (solid content concentration: 0.5 parts by mass of silica and 0.8 parts by mass of ethyl acetate in a coating agent made of DIC (acrylic polyol) resin and an ultraviolet absorber are mixed at once. (40% by mass) of 239.8 parts by mass were dispersed using a bead mill to obtain a main agent of a coating material for forming a UV-resistant layer having a solid content concentration of 40% by mass.

Adjustment of paint: Pre-calculate the isocyanate resin as a hardener so that the mass ratio of DIC (strand) UC CLEAR BS (solid content concentration: 40% by mass) in the main agent of the paint for resin layer formation becomes 100 / 1.5. Urethane hardener G-18N (solid content concentration: 100% by mass) made by DIC (stock), blended with the above-mentioned base agent, and further weighed so as to have a solid content concentration of 30% by mass (resin solids The diluent (ethyl acetate) previously calculated as the coating method of the component concentration) was stirred for 15 minutes to obtain a coating material having a solid content concentration of 30% by mass (resin solid content concentration).

Formation of UV-resistant layer: Corona treatment was applied to one side of film 1, and the coating was further applied using a wire bar, dried at 120 ° C for 60 seconds, and UV-resistant was formed so that the coating thickness became 6.5 μm after drying. Floor. This was aged at 40 ° C. for 3 days to obtain a thin film 9.

    (Manufacturing method of films 1 to 5)    

The film 1 is manufactured in the following operation sequence. First, the thermoplastic resin A and the thermoplastic resin B1 were supplied to a biaxial extruder with a discharge hole, and melted at 275 ° C. After that, the molten resin is discharged while adjusting the discharge amount by a gear pump. After removing foreign matter and the like with respective filters, the two are combined with a supply block having 903 slits to form a total layer. The thermoplastic resin A (layer A) and the thermoplastic resin B1 (layer B) were alternately laminated so that the outermost layer on both sides became a layer of 903. At this time, the temperature of each resin is controlled within the range of 270.0 ° C ± 0.1 ° C before the entrance of the slit-shaped flow path of the supply block, and the thickness of each layer is determined by the flow path of each layer provided in the supply block. The shape and discharge amount of the fine slits are adjusted so that the total thickness ratio of the A layer and the B layer becomes 1: 1. The laminated body including a total of 903 layers obtained in this manner was formed into a sheet shape, and then statically applied to a casting drum whose surface temperature was controlled at 25 ° C. to obtain a cast film. After heating the cast film obtained with a roller group set at 75 ° C, the film was stretched 3.3 times in the conveying direction (longitudinal direction) while being heated rapidly from both sides of the film by a radiant heater between 100 mm in the stretching interval, and temporarily It cooled and obtained the uniaxially stretched film. Next, the uniaxially stretched film was guided to a tenter, and after being preheated with hot air at 100 ° C, it was stretched 3.5 times in the width direction (lateral direction) of the film perpendicular to the conveyance direction at a temperature of 110 ° C. The stretched film was directly heat-treated in a tenter with hot air at 230 ° C, and then subjected to a 5% relaxation treatment in the width direction at the same temperature. After slowly cooling to room temperature, it was rolled with a winder. take. The films 2 to 5 were manufactured in the same manner except that the types of resins and feed blocks having different numbers of slits were used.

    (Example 1)    

Sequential lamination: 3mm thick solar cell cover glass as front substrate, EVA (F806 by Hangzhou FIRST Co., Ltd.) as sealing material, multilayer film (film 1) as reflective member, (1) mirror According to the method described in the production item, a reflector having a light receiving surface size of 1,475 mm × 971 mm is produced. Here, as the solar cell cover glass, embossed glass manufactured by Osaka Glass Industry Co., Ltd. was used. Next, two polycrystalline silicon solar cell modules (light-receiving surface size: 1,475 mm × 971 mm) manufactured by Fujipream Co., Ltd. (hereinafter, in the examples, may be referred to as solar cell modules for short). According to JIS C8914: The reference state of 2005 was used to measure the maximum output. After confirming that the output of the two solar cell modules was almost the same, at an exposure test site (Otsu City, Shiga Prefecture) in Toray Co., Ltd.'s Seta Plant, one of them was facing south and formed at a 25 ° angle to the ground (horizontal surface). Corner way set. In addition, another solar cell module was similarly installed at a location 1.5 m east of the installed solar cell module. Then, in front of one of the solar cell modules, a reflecting mirror is installed facing north and forming an angle of 30 ° with respect to the ground. Table 2 shows the evaluation results of the specular reflectance of the mirror and the output increase rate of the solar cell module.

    (Examples 2 to 5, Comparative Examples 1 to 4)    

Evaluation was performed in the same manner as in Example 1 except that the film for a reflecting member constituting the reflecting mirror was set as shown in Table 2. The evaluation results are shown in Table 2.

    (Comparative example 5)    

Evaluation was performed in the same manner as in Example 1 except that the reflector was made of glass only. The evaluation results are shown in Table 2.

    (Comparative Example 6)    

The evaluation was performed in the same manner as in Example 1 except that a reflector and a solar cell cover glass having a thickness of 3 mm were used as the high-transmission glass having a thickness of 3 mm. The evaluation results are shown in Table 2.

The refractive index difference of the thin film 6 is unknown. The films 7 and 8 in Comparative Examples 3 and 4 do not have a laminated structure in which A and B layers are repeated. The mirror of Comparative Example 5 does not have a film. Therefore, in Comparative Examples 3 to 5, the measurement of the refractive index difference and the cross are not performed. Cutting test.

    [Industrial availability]    

According to the present invention, a photovoltaic power generation system having excellent power generation efficiency and stability in power generation amount can be obtained. The solar power generation system of the present invention is particularly suitable for outdoor use, and more suitable for an open rack.

Claims (10)

    A solar power generation system, comprising: a solar cell module; and a reflector provided at a position where the reflected light is irradiated onto a light-receiving surface of the solar cell module. The specular reflectance of the reflector at a wavelength of 800 nm is 15%. The above is 45% or less, and the light transmittance of the mirror at a wavelength of 800 nm is 20% to 45%.         For example, the photovoltaic power generation system of claim 1, wherein the light transmittance of the reflector at a wavelength of 1,800 nm is 80% or more, and the average light transmittance of the reflector at a wavelength of 1,200 nm or more and 1,400 nm or more is 60% or more. Below 80%.         For example, the solar power generation system according to claim 1 or 2, wherein the reflecting mirror includes a thin film composed of two layers mainly composed of a thermoplastic resin, and the two layers (a layer having a large refractive index is referred to as an A layer to reflect light) Among the layers with a small rate is layer B), the layer A and the layer B are alternately located in the thickness direction, and the total number of layers of the layer A and the layer B is 600 or more, and in accordance with JIS K 5600-5-6: 1999 The test result of the measured peel strength between the A layer and the B layer was classified as 0.         The solar power generation system according to any one of claims 1 to 3, wherein when the light-receiving surface of the reflector is incident at an incidence angle of 30 °, the light-receiving angle is 25 ° to 35 ° and the wavelength is 300 nm to 1,200 nm The maximum value of the average variable angle reflectance at the frequency band is 15% to 35%, and when the light is incident at an angle of 60 °, the light receiving angle is 55 ° to 65 ° and the wavelength is from 300nm to 1,200nm. The maximum reflectance is 10% to 30%.         The solar power generation system according to any one of claims 1 to 4, wherein the mirror has a specular reflectance of 15% to 45% at a wavelength of 700nm, and the light transmittance of the mirror at a wavelength of 700nm is 20 Above 45%.         The solar power generation system according to any one of claims 3 to 5, wherein the thermoplastic resin constituting the A layer is mainly composed of polyalkylene terephthalate.         The solar power generation system according to any one of claims 1 to 6, wherein the haze of the reflecting mirror is 4% or more and 30% or less.         The solar power generation system according to any one of claims 3 to 7, wherein the reflecting mirror has a front substrate, a sealing material, and the A layer and the B layer are alternately located in the thickness direction from the light receiving surface side and The multilayer film having a total number of 600 or more of the A layer and the B layer, the front substrate is made of any one of reinforced glass, polycarbonate, and polymethyl methacrylate, and the sealing material is The main component is any one of ethylene / vinyl acetate copolymer (EVA), transparent silicon, and polymethyl methacrylate.         For example, the solar power generation system of claim 8, wherein the haze of the front substrate is 10% to 75%.         The solar power generation system according to claim 8 or 9, wherein a UV-resistant layer is provided on a surface of the multilayer film on the side opposite to the light-receiving surface.