JP2011077160A - Solar cell module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solar cell module in which temperature rise is moderate at the initial stage of heat generation. <P>SOLUTION: There is provided the solar cell module in which a non-light receiving surface of a photoelectric conversion cell is sealed with an insulating material having a thermal conductivity of 0.3 W/m K or more. The insulating material preferably has a volume resistivity of 10<SP>8</SP>Ω cm or more. The insulating material is, preferably, formed by containing 50-90 pts.mass of insulating inorganic filler, having a thermal conductivity of 5 W/m K or more and 10-50 pts.mass of resin having a glass transition point of 100°C or below. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solar cell module, and more particularly to a solar cell module that suppresses a local temperature increase and alleviates a problem caused by local overheating.

In general, the power generation efficiency of solar cells decreases as the temperature increases. In particular, the crystalline silicon type cell is remarkable, the voltage having the greatest effect is the voltage, which decreases at a rate of 0.4 to 0.5% / ° C., and as a result, the output is also greatly decreased. Further, when the voltage is lowered, this portion has a high electric resistance because of the relationship that the cells are connected in series, and the temperature rise is larger than that of the other portions. For this reason, when the temperature locally rises due to some cause such as shade or dust, the temperature of the portion increases at an accelerated rate, thereby reducing the power generation efficiency of the entire module. In an extreme case, the cell electrodes and the sealing material are thermally deteriorated, causing a failure called a hot spot.

Several module cooling means are known to prevent hot spots. For example, a fin provided on the back surface of a solar cell module, a hybrid module that cools solar cells with a heat medium such as water and uses hot water at the same time, a heat radiation plate, a fluid as a heat medium on the back surface of the module There are those that are filled, water-cooled, air-cooled, those that are cooled by a heat radiating sheet, a heat pipe, etc. (for example, Patent Documents 1 to 8).

  In addition, it has been studied to improve heat conductivity on the non-light-receiving surface side of the photoelectric conversion cell to release heat. For example, Patent Document 9 proposes that heat is released from the non-light-receiving surface side by using a resin sheet sandwiching the photoelectric conversion cell and having a good thermal conductivity from the light-receiving surface side to the non-light-receiving surface side. Yes. Patent Document 10 proposes a technique in which a sheet having high thermal conductivity is disposed between a photoelectric conversion cell and a filler on the non-light-receiving surface side, and particles having high thermal conductivity are used as the filler on the non-light-receiving surface side. Has been.

JP 11-36540 A Japanese Patent Laid-Open No. 10-62017 Japanese Patent Laid-Open No. 2005-123452 Japanese Patent Laid-Open No. 11-354819 JP 2005-18352 A JP 2002-170974 A JP 2005-136236 A JP-A-9-186353 JP-A-10-56189 JP 2004-31455 A

When using a cooling device as disclosed in Patent Documents 1 to 8, a large incidental facility is required, which not only increases the system complexity and size but also increases the cost. For this reason, it is difficult to adopt except for a hybrid with solar hot water. A system mainly intended for direct power generation using sunlight has not been put into practical use except for a condensing large system that requires a local temperature rise. Moreover, the method for improving the thermal conductivity on the non-light-receiving surface side is a simple method, but the system has not been optimized so far. For example, even if a resin sheet with good thermal conductivity is used, if the outer layer portion is a layer with low thermal conductivity, heat stays there. For this reason, the purpose of releasing heat to the outside of the target module to increase the power generation efficiency has not been achieved. Moreover, the method of disposing a sheet having a large thermal conductivity on the non-light-receiving surface of the photoelectric conversion cell is an effective method for suppressing hot spots, but the function of protecting the photoelectric conversion cell is impaired. An object of the present invention is to diffuse the initial heat of the solar cell module and moderate its temperature rise.

The present invention employs the following means in order to solve the above problems.
(1) A solar cell module in which the non-light-receiving surface side of the photoelectric conversion cell is sealed with an insulating material having a thermal conductivity of 0.3 W / m · K or more.
(2) The solar cell module according to (1), which is an insulating material having a volume resistivity of 10 ⁸ Ω · cm or more.
(3) Insulation in which the insulating material contains 50 to 90 parts by mass of an insulating inorganic filler having a thermal conductivity of 5 W / m · K or more and 10 to 50 parts by mass of a resin having a glass transition temperature of 100 ° C. or less. The solar cell module according to (1) or (2), wherein the solar cell module is a conductive material.
(4) The solar cell module according to any one of (1) to (3), wherein a thickness of the sealed insulating material is 0.1 mm or more.

The solar cell module according to the present invention can suppress a temperature rise in the initial heat generation of the solar cell module by a simple and inexpensive method.

In the present invention, the photoelectric conversion cell refers to an element that converts light energy into electric energy, and includes various types such as single crystal silicon type, polycrystalline silicon type, amorphous silicon type, compound semiconductor type, organic semiconductor type, and photosensitized type. Various types are known. Although not particularly limited in the present invention, the main target is a single crystal or polycrystalline silicon solar cell that is most popular, has abundant practical data, and has the greatest influence of temperature rise.

In the present invention, the non-light-receiving surface indicates the reverse surface of the light-receiving surface that receives sunlight. The light-receiving surface needs to be light transmissive in order to take in a lot of sunlight, but the non-light-receiving surface is less necessary. Rather, it is made opaque to scatter light to increase the conversion efficiency of incident sunlight. ing.

  In the present invention, the insulating material for sealing the non-light-receiving surface of the photoelectric conversion cell has a thermal conductivity of 0.3 W / m · k or more, preferably 0.5 W / m · K, more preferably 1.0 W / An insulating material of m · K or more is used. Here, if the thermal conductivity is low, the effect of diffusing heat decreases.

In the present invention, as the insulating material for sealing the non-light-receiving surface of the photoelectric conversion cell, an insulating material having a volume resistivity of preferably 10 ⁸ Ω · cm or more, more preferably 10 ¹⁰ Ω · cm or more is used. . If the volume resistance value is small, current leakage and unnecessary energization are likely to occur, resulting in a reduction in power generation and failure.

The insulating inorganic filler used in the insulating material of the present invention has a thermal conductivity of 5 W / m · K or more, preferably 10 W / m · K or more, and a volume resistivity of preferably 10 ⁸ Ω · cm or more. More preferably, an insulating inorganic filler of 10 ¹⁰ Ω · cm or more is used. Such inorganic fillers are preferably oxides, hydroxides, nitrides and carbides of metal elements such as B, Al, Mg, Ca, Si, Zn, Sn, Ti, Fe, Cu, Ni, and Zr. , Borides and the like are used. Among these, in consideration of thermal conductivity, hygroscopicity, chemical stability and price, Al ₂ O ₃ and MgO which are oxides of Al and Mg, Al (OH) ₃ and Mg (which are hydroxides) OH) ₂ and nitrides such as AlN and BN are particularly preferred. These insulating inorganic fillers can be used alone, but can be used in a plurality of two or more. In this case, the thermal conductivity is obtained by weighted averaging the thermal conductivity of each insulating inorganic filler by the volume fraction.

The insulating material in the present invention contains an insulating inorganic filler and a resin having a glass transition temperature of 100 ° C. or lower, preferably 80 ° C. or lower, more preferably 60 ° C. or lower. If the glass transition temperature of the resin is high, the insulating material is hard and brittle, and the sealing function for protecting the photoelectric conversion cell is lowered. For this reason, in this invention, it is also possible to use the plasticizer which softens resin with resin and an insulating inorganic filler. In this case, the glass transition temperature of the insulating material is the glass transition temperature of the resin.

  The resin used in the present invention is not particularly limited, but includes ethylene / vinyl acetate copolymer (EVA), olefinic monomers such as ethylene and propylene, acrylic acid, ethyl acrylate, butyl acrylate, octyl acrylate, and the like. Acrylic, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic monomers such as octyl methacrylate, copolymers with styrene, ethylene, propylene and maleic acid, maleic anhydride, methyl maleate , Copolymers with maleic monomers such as ethyl maleate, copolymers such as ethylene, propylene and butadiene, acrylonitrile, high molecular weight resins such as polyethylene glycol and polypropylene glycol, either alone or copolymerized, acrylic Homo or copolymers and methacrylic and monomers such as styrene, polyvinyl butyral resins, silicone resins and epoxy resin is used. These resins preferably have a large molecular weight in view of the effect of protecting the photoelectric conversion cell and the stable retention of the insulating inorganic filler. Generally, a resin having a weight average molecular weight of 10,000 or more is used. In addition, it is also possible to produce an insulating material using a low molecular weight resin and form a crosslink while fixing the positional relationship with the photoelectric conversion cell.

  The plasticizer used in the insulating material in the present invention is selected depending on the resin, but is preferably substantially non-volatile. The fact that it does not substantially volatilize means that the temperature may be as high as about 100 ° C. in an environment where the solar cell module is used, but there is no vapor pressure at this temperature. Commonly used plasticizers include low molecular weight compounds having a composition similar to that of resins, polyethylene glycol, polyprolene col, long chain fatty alcohols, glycerin, saccharides, etc., long chain fatty acids, sorbitan acid, phthalic acid, malein Acids, phosphoric acid, adipic acid, trimellitic acid, citric acid, and other esters and ethers are used.

The insulating material in this invention contains 50-90 mass parts of insulating inorganic fillers and 10-50 mass parts of resin. Here, if there are few insulating inorganic fillers, thermal conductivity will become low, and if there are many, it will become weak and the function which protects a photoelectric conversion cell will fall. If there is little resin, it will become weak, and if there is much resin, thermal conductivity will become low. Moreover, in this invention, an insulating organic filler, a conductive inorganic filler, etc. can be used together in the range in which characteristics, such as heat conductivity and insulation, do not deviate.

  In the solar cell module of the present invention, the thickness of the sealed insulating material is 0.1 mm or more at the thinnest portion, preferably 0.2 mm or more, and more preferably 0.3 mm or more. If the insulating material is thin, it becomes a bottleneck for heat conduction, impairing the thermal diffusivity, and if it is too thick, the amount of expensive insulating material used increases and the cost increases.

The solar cell module of the present invention preferably has a low thermal conductivity anisotropy of the sealed insulating material, and the ratio of the thermal conductivity between the horizontal plane and the vertical plane with respect to the photoelectric conversion cell is preferably 5 or less, more preferably. Is 3 or less. This is because the heat generated in the photoelectric conversion cell is transferred in the vertical direction and then diffused in the horizontal direction, so if the thermal conductivity anisotropy is large, the transfer of thermal conductivity is limited to the smaller one. Will be. Also,

The solar cell module of the present invention preferably has a low insulation anisotropy of the sealed insulating material, and the ratio of the electrical resistance between the horizontal plane and the vertical plane with respect to the photoelectric conversion cell is preferably 5 or less, more preferably 3 It is as follows. This is because anisotropic conductivity exists when the anisotropy of insulation is large, and the anisotropy is disturbed when stress is applied to the sealing process or the module being used, causing failure or malfunction. Prone to cause.

  The light receiving surface side of the solar cell module of the present invention is not particularly limited. It is essential to be transparent in order to receive sunlight, but the most commonly used structure uses tempered glass as the outermost layer, ethylene / vinyl acetate copolymer resin, ethylene / acrylic acid copolymer resin, polyvinyl butyral Sealed with resin. Although it is preferable to use it as it is in the present invention, it is not particularly limited.

Hereinafter, the present invention will be described in detail by way of examples.
1) Production of insulating material EVA resin EVAflex EV250 (manufactured by Mitsui DuPont Polychemical Co., Ltd., vinyl acetate content 28% by weight, glass transition temperature -28 ° C, softening temperature 39 ° C) with the composition shown in Table 1 and heat Heating roll of alumina filler DAW70 (made by Denki Kagaku Kogyo Co., Ltd., average particle size 70 μm) with conductivity 32 W / m · K and DAW05 (made by Denki Kagaku Kogyo Co., Ltd., average particle size 5 μm) with a thermal conductivity of 32 W / m · K Was used and kneaded at 150 ° C. to produce an insulating material. This was molded with a hydraulic press at a temperature of 120 ° C./10 mPa to obtain a sheet having a thickness of 1.0 mm.
2) Measurement of thermal conductivity, volume resistivity, and hardness The thermal conductivity, volume resistivity (based on JIS K 7194), and hardness (Asker C) of the prepared sheet were measured.
(Thermal conductivity)
The thermal conductivity of the heat conductive sheet is fixed between the TO-3 type copper heater case and the copper plate so that the sheet thickness is compressed by 10%, and then the heater case is supplied with electric power of 15 W between the heater case and the copper plate. The temperature difference was measured until the difference became constant, and the thermal resistance was calculated from the following formula (1).
Thermal resistance (° C./W)=Temperature difference (° C.) / Applied voltage (W) Equation (1)
Based on the obtained thermal resistance value, the thermal conductivity was calculated from the following formula (2). In addition, the thickness of a heat conductive sheet here is the thickness at the time of a thermal resistance measurement (The thickness which screwed so that sheet thickness might be compressed 10%, and measured thermal resistance). The heat transfer area is a TO-3 type heat transfer area of 0.0006 mm ² .
Thermal conductivity (W / m · K) =
Thermally conductive sheet thickness (m) / {thermal resistance (° C./W)×heat transfer area (m ² )} Formula (2)
(Asker C hardness)
The Asker hardness C at a temperature of 23 ° C. of the produced sheet was measured. Here, the Asker C hardness is SRISOlOl defined by the Japan Rubber Association standard.
2) Module production EVA sheet for solar cell sealing material (SOLAR EVA, Mitsui Chemicals Fabro Inc.) having a thickness of 0.8 mm as a light-receiving surface side filler on a 500 mm × 500 mm × 3 mm (thickness) solar cell cover glass Placed in series at a 1 cm interval around three photoelectric conversion cells (polycrystalline silicon, 150 mm × 150 mm × 0.25 mm) connected in series so that electricity can be taken out of the module. Further, sheets 1 to 4 as the non-light-receiving surface side filler and the same EVA sheet as the light-receiving surface side filler as a comparative example are laid thereon, and a fluorine resin film and a laminate sheet of PET resin are further used as the back material. They were stacked so as to be at the top and sealed with a solar cell laminator. The treatment conditions were as follows: a temperature of 120 ° C., a vacuum for 2 minutes, an atmospheric pressure press for 10 minutes, and an atmospheric pressure press at 150 ° C. for 30 minutes. No end face treatment was performed.
3) Initial evaluation of module The obtained solar cell module was evaluated by a method based on Reference 1 hot spot test (first) A-6 of JIS C 8917. However, the evaluation target was only the central cell, the temperature rise due to the presence or absence of the entire shielding was measured every 5 minutes, and the maximum temperature and the time reached were recorded. The results are summarized in Table 2.

From the examples and comparative examples, the solar cell module of the present invention was able to moderate the temperature rise in the initial heat generation of the solar cell module. Therefore, it can be expected to suppress the occurrence of the hot spot phenomenon.

Claims (4)

A solar cell module in which a non-light-receiving surface side of a photoelectric conversion cell is sealed with an insulating material having a thermal conductivity of 0.3 W / m · K or more. The solar cell module according to claim 1, which is an insulating material having a volume resistivity of 10 ⁸ Ω · cm or more. The insulating material is an insulating material comprising 50 to 90 parts by mass of an insulating inorganic filler having a thermal conductivity of 5 W / m · K or more and 10 to 50 parts by mass of a resin having a glass transition temperature of 100 ° C. or less. The solar cell module according to claim 1 or 2. The solar cell module according to any one of claims 1 to 3, wherein the sealed insulating material has a thickness of 0.1 mm or more.