JP2012164901A - Building material integrated type solar battery and back sheet of the solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of a conventional building material integrated type solar battery in which a steel plate having the entire surface coated with a dark colored coat is used as a back sheet and thus a sunshine reflection rate and an infrared radiation rate of the back sheet are low, leading to the deterioration of the generation efficiency.SOLUTION: In a building material integrated type solar battery according to this invention, a double face painted steel plate, having a first end surface 3a on the solar battery module 2 side which is formed by a reflective coat 31 having light reflectivity and a second end surface 3b which is positioned on the reverse side of the first end surface 3a and is formed by a radioactive coat 32 having heat radiation property, is used as the back sheet 3.

Description

  The present invention relates to a building material integrated solar cell and its back sheet, and in particular, the first end surface on the solar cell module side is formed of a reflective coating film having light reflectivity, and is located on the back side of the first end surface. The present invention relates to a novel improvement for improving power generation efficiency while avoiding an increase in component costs by using a double-sided coated steel sheet composed of a radioactive coating film having thermal radiation as a back sheet.

  Examples of this type of building material integrated solar cell and its back sheet that have been used in the past include the configurations shown in Non-Patent Document 1 below. That is, in the conventional building material-integrated solar cell, a back sheet made of a steel plate for roof is fixed to the anti-light-receiving surface of the solar cell module. Generally, as a steel sheet for roofs used in such a building material-integrated solar battery 1, a dark color paint (L * = 35 or less) as shown in the following table is used in order to match the color tone with other parts of the roof. A steel plate whose entire surface is coated is preferably used.

“Guidelines and Basics for Photovoltaic Field Testing Projects: Solar Power Generation for the Future” (Issued Date: March 19, 2008, Issued by the New Energy and Industrial Technology Development Organization, page 6)

In the conventional building material integrated solar cell 1 as described above, since the steel sheet coated with the dark paint is used as the back sheet, the solar reflectance (JIS K 5602) of the back sheet is 10% or less. Low. For this reason, the reflected light from the back sheet cannot be used for power generation, and power generation efficiency is reduced.
In addition, since the infrared emissivity is as low as about 0.6 to 0.8 in the steel sheet coated as described above, the temperature of the back sheet increases due to the radiant heat of sunlight, for example, in the case of strong solar radiation such as in summer. There is a high possibility that it will greatly exceed the temperature drop due to heat dissipation. For this reason, the temperature of a solar cell module also rises with the temperature rise of a back sheet, and power generation efficiency will fall. Considering the cooling of the solar cell module and the back sheet, it may be possible to attach a heat radiation fin to the back sheet, but this leads to an increase in component costs.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a building material-integrated solar cell that can improve power generation efficiency while avoiding an increase in parts cost, and a back sheet thereof. That is.

  The back sheet of the building material integrated solar cell according to the present invention is a back sheet of the building material integrated solar cell fixed to the anti-light-receiving surface of the solar cell module, and the first end surface on the solar cell module side has light reflectivity. It consists of a double-sided coated steel sheet in which the second end face located on the back side of the first end face is made of a radioactive paint film having thermal radiation.

  Moreover, the building material integrated solar cell according to the present invention includes a solar cell module and a back sheet fixed to the non-light-receiving surface of the solar cell module, and the first end surface on the solar cell module side reflects the back sheet. It consists of a double-coated steel sheet in which a second end face located on the back side of the first end face is constituted by a radioactive paint film having thermal radiation.

  According to the building material integrated solar cell of the present invention and the back sheet thereof, the first end surface on the solar cell module side is constituted by a reflective coating film having light reflectivity, and the second end surface located on the back side of the first end surface is Since the double-sided coated steel sheet composed of a thermal radiation coating is used as a back sheet, the reflected light from the back sheet can be used for power generation, and the temperature of the back sheet and solar cell module can be increased without using additional components. Can be prevented. As a result, power generation efficiency can be improved while avoiding an increase in component costs.

It is a figure which shows the external appearance of the building material integrated solar cell by Embodiment 1 of this invention. It is a figure which shows the external appearance of the modification of the building material integrated solar cell of FIG. It is a side view which expands and shows the solar cell module and back sheet | seat of FIG.1 and FIG.2. It is a graph which shows the relationship between the solar radiation reflectance of the back seat | sheet surface of FIG. 3, and the surface temperature of a solar cell module. It is a graph which shows the relationship between the infrared emissivity of the back seat | sheet back surface of FIG. 3, and the surface temperature of a solar cell module.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a view showing the appearance of a building material-integrated solar cell 1 according to Embodiment 1 of the present invention. FIG. 1 (a) shows the top surface of the building material-integrated solar cell 1, and FIG. Shows the side of the building material integrated solar cell 1. As shown in FIG. 1, the building material integrated solar cell 1 has a solar cell module 2 and a back sheet 3. The solar cell module 2 generates light by receiving light from the light receiving surface 2a. In the drawing, although the solar cell module 2 is shaded, it does not show the actual color tone, but is for easy understanding.

  The back sheet 3 is a hard member fixed to the anti-light-receiving surface 2b of the solar cell module 2, and serves as a building material constituting the roof of the house as a whole. Engaging portions 4 extending along the width direction 1 a are formed at both upper and lower end portions of the backsheet 3, and the engaging portions 4 are engaged with the engaging portions 4 of the other backsheet 3. Thus, the plurality of building material integrated solar cells 1 are connected so as to form a recumbent roof.

  Next, FIG. 2 is a figure which shows the external appearance of the modification of the building material integrated solar cell 1 of FIG. 1, (a) of FIG. 2 has shown the plane, (b) of FIG. 2 has shown the side surface. ing. The building material integrated solar cell 1 in FIG. 1 forms a recumbent roof, but as shown in FIG. 2, the engaging portion 4 of the back sheet 3 extends along the depth direction 1b, and the engaging portion A vertical roof can be formed by engaging 4 with the engaging portion 4 of another backsheet 3 by caulking.

  Next, FIG. 3 is an enlarged side view showing the solar cell module 2 and the back sheet 3 of FIGS. 1 and 2. In the solar cell module 2, the cover member 20, the first sealing material 21, the solar battery cell 22, and the second sealing material 23 are sequentially laminated from the light incident side (front surface). The cover member 20 is an exterior material that constitutes the light receiving surface 2a of the solar cell module 2, and is made of, for example, a resin film or a glass plate that is excellent in light transmittance and weather resistance. The first and second sealing materials 21 and 23 are for embedding and stabilizing the solar cells 22 made of crystalline silicon or the like, and are mainly made of a thermoplastic resin excellent in thermal fluidity and thermal adhesiveness. It is comprised by the resin plastic material used as a component. These cover member 20, the 1st sealing material 21, the photovoltaic cell 22, and the 2nd sealing material 23 are integrated by the vacuum laminating method etc., for example. The cover member 20 has a thickness of about 1.1 mm, and the first and second sealing materials 21 and 23 have a thickness of about 0.9 mm.

  The back sheet 3 is fixed to the anti-light-receiving surface 2 b of the solar cell module 2, that is, the rear surface of the second sealing material 23. The back sheet 3 is made of a stainless steel plate 30 as a base material, and is composed of a coating film having functions different on the front surface and the back surface. That is, the back sheet 3 is configured by a reflective coating 31 having a light-reflecting first end surface 3a (front surface) on the solar cell module 2, and a second end surface 3b (on the back side of the first end surface 3a). The back surface is a double-sided coated steel plate composed of a radioactive coating film 32 having thermal radiation. The thickness of the back sheet 3 is about 0.27 mm.

  Next, the effect | action that the back sheet 3 is comprised with the double-sided coated steel plate is demonstrated. The light incident on the solar cell module 2 passes through the cover member 20 and the first sealing material 21 and reaches the solar cell 22, while passing through the gap between the solar cells 22 and the second sealing material 23. As a result, the first end surface 3a of the backsheet 3 is reached. At this time, since the first end face 3a is constituted by the reflective coating 31, the light that has reached the first end face 3a can be reflected by the first end face 3a, and this reflected light is reflected by the solar battery cell 22. Can be used for power generation. On the other hand, the back sheet 3 absorbs the radiant heat of the incident light. However, since the second end surface 3b is constituted by the radiation coating film 32 having thermal radiation, the radiant heat is the second end surface opposite to the solar cell module 2. Heat is radiated from 3b. Thereby, without using additional parts, such as a radiation fin, the temperature rise of the solar cell module 2 by the radiant heat which the back seat | sheet 3 absorbed can be made small, and the fall of the power generation efficiency accompanying the temperature rise of the solar cell module 2 can be avoided. .

  Next, the reflective coating film 31 will be described in more detail. The present applicant uses six 100 W halogen lamps as a light source for a solar cell module having a size of 250 mm × 300 mm, and uses the solar reflectance (JIS K 5602) of the backsheet surface and the temperature of the solar cell module surface. I investigated the relationship.

  FIG. 4 is a graph showing the relationship between the solar reflectance on the surface of the back sheet of FIG. 3 and the surface temperature of the solar cell module. As shown in the figure, it was found that the surface temperature of the solar cell module was lowered as the solar reflectance on the surface of the back sheet was increased. Specifically, the surface temperature was 39 ° C. when the solar reflectance was 5%, but the surface temperature could be suppressed to about 34 ° C. or lower when the solar reflectance was 25% or higher.

  Here, the power generation efficiency of the crystalline silicon solar cell is greatly influenced by temperature, and it is said that the power generation efficiency decreases by 0.4 to 0.5% when the temperature rises by 1 ° C. That is, when the solar reflectance is 25% or more, the surface temperature can be lowered by about 5 ° C. or more compared to the case where the solar reflectance is 5%, so that the power generation efficiency can be improved by 2 to 2.5% or more. become. This improvement rate is sufficient because it corresponds to more than 10% of the power generation efficiency of the crystalline silicon solar cell. Therefore, as the reflective coating 31, it is preferable to use a coating having a solar reflectance of 25% or more.

  Further, when the solar reflectance was 80% or more, the surface temperature could be suppressed to about 30 ° C. or less. That is, when the solar reflectance is 80% or more, the surface temperature can be lowered by about 10 ° C. or more as compared with the case where the solar reflectance is 5%, so that the power generation efficiency can be improved by 4 to 5% or more. . Since this improvement rate corresponds to more than 20% of the power generation efficiency of the crystalline silicon solar cell, it is quite useful. Therefore, it is more preferable to use a coating film having a solar reflectance of 80% or more as the reflective coating film 31.

As the coating film having a solar reflectance of 80% or more, various coating films can be used. However, the applicant of the present invention disclosed in JP 2007-47601 A, JP 2001-243819 A, and JP 2007-108242 A. It is possible to use the coating film disclosed in Japanese Patent Publication. That is, (1) (meth) acrylic polymer: 2-50 parts by mass, (meth) acrylic acid isobornyl: 30-97% by mass (meth) acrylic monomer: 98-50 parts by mass of (meth ) Thermal radical polymerization initiator in acrylic mixture: 0.1-5 parts by mass, cross-linking agent: 0.1-20 parts by mass, plasticizer with molecular weight of 500 or more: 1-20 parts by mass, titanium oxide pigment: 40-120 Diffusion reflection in which mass parts are blended and formed from a heat-polymerized acrylic paint whose viscosity is adjusted to 1 to 100 Pa · s, total reflectance in color measurement according to JIS Z8722 is 94% or more, and regular reflection light is removed. The main component is a coating film having a rate of 91% or more, and (2) an undercoating film to which a white pigment TiO ₂ powder is added, and a polyester resin containing TiO ₂ powder. The specific gravity N of the coating film is 1.75 <<2.3, the L value in hue measured by JIS Z 8722 90 than can be used a coating film comprising a topcoat coating film gloss by 60 ° specular gloss method 80 more than. If such a coating film is used, more reflected light can be utilized for the electric power generation in the photovoltaic cell 22, and electric power generation efficiency can be improved more reliably.

  As a coating film having a solar reflectance of 25% or more and less than 80%, a coating film disclosed by the present applicant in JP-A-2002-331611, that is, one or more kinds of V, Sr, and Y The coating film which contains the powder of the composite metal oxide containing Mn as a heat-shielding pigment can be mentioned. If such a coating film is used, the 1st end surface 3a of the back sheet 3 can be made into dark colors, such as black, dark brown, and dark blue, for example, and it can match | combine easily with the other part of a roof. it can.

  Next, the radioactive coating film 32 will be described in more detail. The present applicant investigated the relationship between the infrared emissivity on the back surface of the back sheet and the surface temperature of the solar cell module using six 100 W halogen lamps as light sources for the solar cell module having a size of 250 mm × 300 mm. It was.

  FIG. 5 is a graph showing the relationship between the infrared emissivity on the back surface of the back sheet of FIG. 3 and the surface temperature of the solar cell module. As shown in the figure, it was found that the surface temperature of the solar cell module was lowered as the infrared emissivity on the back surface of the back sheet was increased. Specifically, the surface temperature was 48 ° C. when the infrared emissivity was 0.05%, but the surface temperature could be suppressed to about 43 ° C. or less when the infrared emissivity was 0.85% or more. It was.

  As described above, the power generation efficiency of the crystalline silicon solar cell is said to decrease by 0.4 to 0.5% as the temperature increases by 1 ° C. That is, when the infrared emissivity is 0.85% or more, the surface temperature can be lowered by about 5 ° C. or more compared to when the infrared emissivity is 0.05%, so that the power generation efficiency is 2 to 2.5%. This can be improved. This improvement rate is sufficient because it corresponds to more than 10% of the power generation efficiency of the crystalline silicon solar cell. Therefore, as the radioactive coating film 32, it is preferable to use a coating film having an infrared emissivity of 0.85 or more.

  As the radioactive coating film 32 having an infrared emissivity of 0.85 or more, various coating films can be used, but the coating film disclosed by the present applicant in Japanese Patent Application Laid-Open No. 2004-276383, that is, surface tension, curing. It is possible to use a paint film made of a shrink paint obtained by mixing two or more kinds of resins having different speeds and the like and formed into a resin paint film having a predetermined surface roughness by application and baking under appropriate conditions. Although there are no particular restrictions on the paint resin system, polyester resin, acrylic resin or the like is used. The baking conditions are selected in the range of 180 to 250 ° C. and 30 to 120 seconds. The application amount of the shrink paint is determined so that a resin coating film having a film thickness of 12 μm or more is formed in order to make the infrared emissivity 0.85 or more. If the resin coating is too thin, the infrared emissivity tends to be low due to the influence of reflection on the surface of the substrate / metal plate.

  In such a building material integrated solar cell 1 and its back sheet 3, the first end surface 3 a on the solar cell module 2 side is configured by a reflective coating 31 having light reflectivity, and is located on the back side of the first end surface 3 a. Since the double-sided coated steel plate in which the second end surface 3b is composed of the radioactive coating film 32 having thermal radiation is used as the back sheet 3, the reflected light from the back sheet 3 can be used for power generation and the back without using additional parts. The temperature rise of the sheet 3 and the solar cell module 2 can be prevented. As a result, power generation efficiency can be improved while avoiding an increase in component costs.

  Moreover, since the reflective coating film 31 has a solar reflectance of 25% or more, the reflected light on the first end surface 3a of the back sheet 3 can be increased, and the power generation efficiency can be improved more reliably.

  Furthermore, since the radioactive coating film 32 has an infrared emissivity of 0.85 or more, heat radiation from the second end surface 3b of the back sheet 3 can be increased, and a temperature increase of the back sheet 3 and the solar cell module 2 can be avoided. Thereby, the fall of the power generation efficiency accompanying the temperature rise of the solar cell module 2 can be avoided more reliably, and the power generation efficiency can be improved.

DESCRIPTION OF SYMBOLS 1 Building material integrated solar cell 2 Solar cell module 2b Anti-light-receiving surface 3 Back sheet 3a 1st end surface 3b 2nd end surface 31 Reflective coating film 32 Radiant coating film

Claims (6)

  A back sheet for a building material-integrated solar cell fixed to the anti-light-receiving surface (2b) of the solar cell module (2), wherein the first end surface (3a) on the solar cell module (2) side has light reflectivity. It consists of a double-coated steel sheet composed of a reflective coating (31) and a second end surface (3b) located on the back side of the first end surface (3a) composed of a radioactive coating (32) having thermal radiation. A backsheet for a building material-integrated solar cell characterized by   The said reflective coating film (31) has a solar reflectance of 25% or more, The backsheet of the building material integrated solar cell of Claim 1 characterized by the above-mentioned.   The said radioactive coating film (32) has an infrared emissivity of 0.85 or more, The back sheet | seat of the building material integrated solar cell of Claim 1 or Claim 2 characterized by the above-mentioned. A solar cell module (2);
A back sheet (3) fixed to the anti-light-receiving surface (2b) of the solar cell module (2),
In the back sheet (3), the first end surface (3a) on the solar cell module (2) side is constituted by a reflective coating (31) having light reflectivity, and on the back side of the first end surface (3a). The building material integrated solar cell, wherein the second end face (3b) is made of a double-sided coated steel plate composed of a radioactive coating film (32) having thermal radiation.   The building material-integrated solar cell according to claim 4, wherein the reflective coating film (31) has a solar reflectance of 25% or more.   The building material-integrated solar cell according to claim 4 or 5, wherein the radioactive coating film (32) has an infrared emissivity of 0.85 or more.

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