JP2013008830A - Optical element for concentrating photovoltaic power generator, manufacturing method therefor, and concentrating type photovoltaic power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element for photovoltaic power generator with excellent weatherability, manufacturing method therefor, and concentrating type photovoltaic power generator.SOLUTION: The optical element 4 for concentrating type photovoltaic power generator is composed of glass material with a flame-polished surface 40. The glass material has a pair of end faces and a pair of side faces opposing to each other, and at least a part of the side faces are flame-polished.

Description

  The present invention relates to an optical element of a concentrating solar power generation device, a manufacturing method thereof, and a concentrating solar power generation device.

  Conventionally, in a concentrating solar power generation apparatus, a glass optical system is provided between a condensing lens and a solar battery cell. The optical system made of glass transmits the light collected by the condensing lens to the solar battery cell with total reflection on the inner surface. Therefore, the optical characteristics of the optical system are affected by the surface state.

  The concentrating solar power generator is mainly used outdoors. Therefore, weather resistance is required for the optical system. For example, Patent Document 1 discloses that a fluororesin thin film is provided on the side surface of an optical system. In Patent Document 1, it is proposed that this prevents the surface of the optical system from becoming clouded by water droplets and the like, and preventing a part of light from leaking therefrom.

JP 2006-275881 A

  In a concentrating solar power generation device, a further powerful optical element having excellent weather resistance is required. The main object of the present invention is to provide an optical element of a concentrating solar power generation device excellent in weather resistance, a manufacturing method thereof, and a concentrating solar power generation device.

  The optical element of the concentrating solar power generation device of the present invention is made of a glass material having a flame-polished surface.

  In the optical element of the concentrating solar power generation device of the present invention, the glass material preferably has a pair of end faces and side faces facing each other, and at least a part of the side faces is subjected to flame polishing.

  In the optical element of the concentrating solar power generation device of the present invention, the surface roughness of the flame-polished portion of the surface of the optical element is preferably 200 nm or less in terms of arithmetic average roughness (Ra).

  In the optical element of the concentrating solar power generation device of the present invention, the glass material may contain an alkali component.

  In the optical element of the concentrating solar power generation device of the present invention, the glass material may be made of silicate glass.

  The concentrating solar power generation device of the present invention includes a solar cell and a condensing optical system that condenses the solar cell. The condensing optical system has an optical element made of a glass material having a flame-polished surface.

  In the method for manufacturing an optical element of the concentrating solar power generation device of the present invention, an optical element is obtained by flame polishing at least a part of the surface of the glass material.

  In the method for manufacturing an optical element of the concentrating solar power generation device of the present invention, flame polishing may be performed by burner heating, high frequency induction heating, or resistance heating.

  ADVANTAGE OF THE INVENTION According to this invention, the optical element of the concentrating solar power generation device excellent in the weather resistance, its manufacturing method, and a concentrating solar power generation device can be provided.

It is a typical conceptual diagram of the concentrating solar power generation device which concerns on one Embodiment of this invention. 1 is a schematic perspective view of an optical element according to an embodiment of the present invention.

  Hereinafter, an example of the preferable form which implemented this invention is demonstrated. However, the following embodiment is merely an example. The present invention is not limited to the following embodiments.

  Moreover, in each drawing referred in embodiment etc., the member which has the substantially same function shall be referred with the same code | symbol. The drawings referred to in the embodiments and the like are schematically described, and the ratio of dimensions of objects drawn in the drawings may be different from the ratio of dimensions of actual objects. The dimensional ratio of the object may be different between the drawings. The specific dimensional ratio of the object should be determined in consideration of the following description.

(Concentrated solar power generator)
FIG. 1 is a schematic conceptual diagram of a concentrating solar power generation apparatus including an optical element according to this embodiment.

  The concentrating solar power generation device 1 includes a solar cell 5 and a condensing optical system 2 that condenses sunlight on the solar cell 5. The condensing optical system 2 includes a condensing member 3 and an optical element 4. The condensing member 3 condenses light such as sunlight. The condensing member 3 can be composed of, for example, a convex lens or a Fresnel lens having positive optical power.

  The optical element 4 is disposed between the light collecting member 3 and the solar cell 5. The light condensed by the condensing member 3 enters the optical element 4 from the end face 41 of the optical element 4 (see FIG. 2). The optical element 4 homogenizes the light collected by the light collecting member 3 and guides it to the light receiving surface 50 of the solar cell 5. Specifically, the light incident on the optical element 4 propagates through the optical element 4 while being homogenized by being reflected by the side surfaces 43 a to 43 d of the optical element 4. The light propagating through the optical element 4 is emitted from the end face 42 of the optical element 4 toward the light receiving surface 50 as a homogenized planar light.

  The solar cell 5 is disposed on the end surface 42 of the optical element 4 so that the light receiving surface 50 faces the end surface 42. The light emitted from the end face 42 of the optical element 4 enters the solar cell 5. And in the solar cell 5, light energy is converted into electrical energy.

  In addition, the kind of solar cell 5 is not specifically limited. The solar cell 5 can be composed of, for example, a single crystal silicon solar cell, a polycrystalline silicon solar cell, a thin film solar cell, an amorphous silicon solar cell, a dye-sensitized solar cell, an organic semiconductor solar cell, or the like.

(Optical element)
FIG. 2 is a schematic perspective view of the optical element according to the present embodiment. Next, a specific configuration of the optical element 4 will be described with reference to FIG.

  The optical element 4 is made of a glass material. The glass material constituting the optical element 4 preferably contains an alkali component. Examples of the alkali component include lithium, potassium, cesium and the like.

The glass material is preferably silicate glass. Specifically, a glass material, for _example, SiO 2: 40 to 80 _{wt%, Al} 2 O 3: _{0~30 wt%, B} 2 O 3: _0~30 wt%, CaO: 0 to 20 wt%, MgO: 0 to 20 wt%, ZnO: 0 to 20 wt%, BaO: 0 to 20 _wt%, Na 2 O: 0~20 _wt%, K 2 O: 0~20 _wt%, Li 2 O: _0~ 20 _wt%, TiO 2: 0 _wt%, ZrO 2: 0 to 20 _{wt%, Sb} 2 O 3: _0~1 wt% and SrO: is preferably one containing from 0 to 20 wt%.

  In the present invention, the silicate glass includes borosilicate glass.

The glass material preferably has a thermal expansion coefficient of 120 × 10 ⁻⁷ / ° C. or less, more preferably 100 × 10 ⁻⁷ / ° C. or less, and 80 × 10 8 within a temperature range of 30 ° C. to 300 ° C. More preferably, it is ⁻⁷ / ° C. or lower. This is because if the thermal expansion coefficient of the glass material is too large, cracks are likely to occur in the glass material due to thermal shock when flame polishing described in detail later is performed.

  The internal transmittance of the glass material at a wavelength of 400 nm is preferably 80% / 10 mm or more, more preferably 85% / 10 mm or more, and further preferably 87.5% / 10 mm or more.

  The glass material has a shape that tapers from the light collecting member 3 side toward the solar cell 5 side. The surface 40 of the glass material has two end surfaces 41 and 42 constituting a light entrance / exit surface and side surfaces 43a to 43d constituting a light reflection surface. The end surfaces 41 and 42 are opposed to each other. The side surfaces 43 a to 43 d connect the end surfaces 41 and 42.

  At least a part of the surface 40 of the glass material constituting the optical element 4 is flame-polished. Specifically, at least a part of at least the side surfaces 43a to 43d of the surface 40 of the glass material is flame-polished. In the present embodiment, specifically, the entire surface 40 of the glass material is flame polished. For this reason, the corner | angular part and ridgeline part of glass material are also flame-polished, and it is R chamfering shape.

  The surface roughness of the flame-polished portion of the surface 40 is usually 200 nm or less in terms of the arithmetic surface roughness (Ra) defined by JISB0601. The surface roughness of the flame-polished part of the surface 40 is preferably 100 nm or less in arithmetic surface roughness (Ra), more preferably 50 nm or less, further preferably 20 nm or less, and more preferably 10 nm or less. It is particularly preferred that

  Hereinafter, an example of the manufacturing method of the optical element 4 will be described.

(Optical element manufacturing method)
The optical element 4 is obtained by flame polishing at least a part of the surface 40 of the glass material.

  The method for flame polishing the surface 40 of the glass material is not particularly limited. For example, flame polishing can be performed by burner heating, high-frequency heating, resistance heating, or the like.

  The temperature of flame polishing can be appropriately adjusted in consideration of the composition and physical properties of the glass material. Flame polishing is preferably performed at a temperature equal to or higher than the glass transition temperature (Tg) of the glass material, and more preferably performed at a temperature equal to or higher than the softening temperature (Ts) of the glass material.

  As described above, in this embodiment, at least a part of the surface 40 of the glass material is flame-polished to produce the optical element 4. For this reason, the optical element 4 excellent in weather resistance can be obtained. Although this reason is not certain, it is considered that a protective layer is formed on the surface 40 of the optical element 4 by flame polishing. In particular, when the glass material constituting the optical element 4 contains an alkali component, the surface 40 of the optical element 4 has less alkali components than the inside due to flame polishing, and the weather resistance is significantly superior to the inside. Since the protective layer is formed, it is considered that the effect of improving the weather resistance by flame polishing can be obtained more remarkably.

  Moreover, the weather resistance of the side surfaces 43a to 43d can be improved by flame polishing the side surfaces 43a to 43d of the glass material. Therefore, the light reflectance of the side surfaces 43a to 43d hardly deteriorates with time. Accordingly, it is possible to suppress deterioration with time of the power generation efficiency of the concentrating solar power generation device 1.

  Moreover, the surface roughness of the side surfaces 43a to 43d can be reduced by flame polishing the side surfaces 43a to 43d of the glass material. Therefore, in the side surfaces 43a to 43d, the ratio of regular reflection of light is increased, leakage of light to the outside of the optical element 4 can be suppressed, and light reflectance can be increased. Therefore, the light collection efficiency to the solar cell 5 can be improved. As a result, the power generation efficiency of the concentrating solar power generation device 1 can be further improved. From the viewpoint of further improving the power generation efficiency of the concentrating solar power generation device 1, the surface roughness of the flame-polished part of the surface 40 is 100 nm or less in terms of the arithmetic surface roughness (Ra) defined by JISB0601. It is preferably 50 nm or less, more preferably 20 nm or less, and particularly preferably 10 nm or less.

  Moreover, the ridgeline part and corner | angular part of glass material become R chamfering shape by flame polishing. For this reason, the ridgeline part of a glass material, the chip | tip of a corner | angular part, etc. can be suppressed effectively.

  An antireflection film may be formed on the end surfaces 41 and 42. Thereby, when the sunlight condensed by the condensing member 3 enters the optical element 4 or when the sunlight transmitted through the optical element 4 enters the solar cell 5, the reflection loss of light is reduced. Can do. An example of the antireflection film is a dielectric multilayer film.

  Moreover, you may provide reflective films, such as Ag, Al, Ni, Cr, on the side surfaces 43a-43d. Thereby, the reflectance of the light in the side surfaces 43a to 43d can be further increased.

  In the present embodiment, the case where the glass material constituting the optical element 4 has a truncated pyramid shape has been described. However, the present invention is not limited to this configuration. In the present invention, the optical element is not particularly limited as long as it has a shape capable of condensing light onto a solar cell. The end face does not have to be planar, and may be convex or concave. According to the present invention, even when the optical element 4 has a complicated shape, the surface roughness can be reduced and the light reflection efficiency can be increased.

  Hereinafter, the present invention will be described in more detail based on specific examples. The present invention is not limited to the following examples. The present invention can be implemented with appropriate modifications without departing from the scope of the present invention.

Example 1
As glass raw materials, a SiO ₂ 71 parts by weight, 2 parts by weight of _Al 2 _{O 3,} 9 parts by weight of CaO, 4 parts by weight of MgO, 13 parts by weight of Na ₂ O, _{K 2} O 1 part by weight, Sb ₂ 0.1 part by weight of O ₃ was prepared. These glass raw materials were put in a platinum crucible so that the glass melt had a depth of 50 mm and melted at 1000 ° C. to 1500 ° C. for 3 hours to obtain molten glass. By pouring molten glass into a heat-resistant mold and press-molding, one end surface is a square with a side of about 10 mm, the other end surface is a square with a side of about 5 mm, and the height is about 20 mm. A certain frustum-shaped glass material was obtained.

  The side surface of the obtained glass material was flame-polished using an oxygen burner. Two end faces facing each other were mechanically polished. Table 1 shows the arithmetic surface roughness (Ra) of the side surface of the glass material before and after flame polishing. The arithmetic surface roughness (Ra) was measured as follows. Moreover, the weather resistance of the glass material was evaluated as follows. The results are shown in Table 1.

[Arithmetic surface roughness (Ra)]
The arithmetic surface roughness (Ra) of the side surface of the glass material was measured by ET4000AK manufactured by Kosaka Laboratory.

[Weatherability]
The glass material was left in a constant temperature and humidity chamber at 85 ° C. and a relative humidity of 85% for 2000 hours, and then the presence or absence of cloudiness on the side surface of the glass material was observed with a microscope. In addition, the thing without white turbidity or a precipitate on the surface was evaluated as ◯, and the one with white turbidity or a surface precipitate was evaluated as ×.

(Example 2)
Using the same glass raw material as in Example 1, a glass material was obtained in the same manner as in Example 1. Furthermore, the obtained glass material was reheat press molded. Next, the entire surface of the glass material was flame-polished using an oxygen burner. In the same manner as in Example 1, the arithmetic surface roughness (Ra) of the side surface portion of the glass material before and after flame polishing was measured. Moreover, the weather resistance evaluation of the glass material after flame polishing was performed. These results are shown in Table 1.

(Example 3)
A glass material was obtained in the same manner as in Example 2. Next, the entire surface of the glass material was flame polished by resistance heating with a heater. The arithmetic surface roughness (Ra) of the side surface of the glass material before and after flame polishing was measured. Moreover, the weather resistance evaluation of the glass material after flame polishing was performed. These results are shown in Table 1.

(Comparative Example 1)
A glass material was obtained in the same manner as in Example 1. Next, the entire surface of the glass material was mechanically polished. In the same manner as in Example 1, the arithmetic surface roughness (Ra) of the side surface portion of the glass material before and after polishing was measured. Moreover, the weather resistance evaluation of the glass material after grinding | polishing was performed. These results are shown in Table 1.

(Comparative Example 2)
A glass material was obtained in the same manner as in Example 1. Next, the ridge line portion and the corner portion of the glass material were mechanically polished, and the two end surfaces opposed to the side surface portion were not polished. In the same manner as in Example 1, the arithmetic surface roughness (Ra) of the side surface portion of the glass material was measured. Moreover, the weather resistance evaluation of the glass material after grinding | polishing was performed. These results are shown in Table 1.

Example 4
As glass materials, 50 parts by weight of SiO ₂ , 1 part by weight of Al ₂ O ₃ , 14 parts by weight of B ₂ O ₃ , 1 part by weight of CaO, 12 parts by weight of ZnO, 6 parts by weight of Na ₂ O, K _A platinum crucible was prepared by preparing 9 parts by weight of ₂ O, 2 parts by weight of Li ₂ O, 5 parts by weight of TiO ₂ and 0.1 parts by weight of Sb ₂ O ₃ so that the glass melt had a depth of 50 mm. And melted at 1000 ° C. to 1500 ° C. for 3 hours. Next, by pressing the molten glass, one end surface is a square with a side of about 10 mm, the other end surface is a square with a side of about 5 mm, and the height is about 20 mm. A glass material was obtained.

  The entire surface of the obtained glass material was flame-polished using an oxygen burner.

  In the same manner as in Example 1, the arithmetic surface roughness (Ra) of the side surface portion of the glass material before and after flame polishing was measured. Moreover, the weather resistance evaluation of the glass material after flame polishing was performed. These results are shown in Table 2.

(Example 5)
A glass material was obtained in the same manner as in Example 4. Next, two end surfaces of the glass material facing each other were mechanically polished, and the side surfaces were flame-polished using an oxygen burner. In the same manner as in Example 1, the arithmetic surface roughness (Ra) of the side surface portion of the glass material before and after flame polishing was measured. Moreover, the weather resistance evaluation of the glass material after flame polishing was performed. These results are shown in Table 2.

(Comparative Example 3)
A glass material was obtained in the same manner as in Example 4. Next, the entire surface of the glass material was mechanically polished. In the same manner as in Example 1, the arithmetic surface roughness (Ra) of the side surface portion of the glass material before and after mechanical polishing was measured. Moreover, the weather resistance evaluation of the glass material after grinding | polishing was performed. These results are shown in Table 2.

(Comparative Example 4)
A glass material was obtained in the same manner as in Example 4. Next, the ridge line portion and the corner portion of the glass material were mechanically polished, and the two end surfaces opposed to the side surface portion were not polished. In the same manner as in Example 1, the arithmetic surface roughness (Ra) of the side surface portion of the glass material was measured. Moreover, the weather resistance evaluation of the glass material after grinding | polishing was performed. These results are shown in Table 2.

DESCRIPTION OF SYMBOLS 1 ... Condensing type solar power generation device 2 ... Condensing optical system 3 ... Condensing member 4 ... Optical element 40 ... Surface 41, 42 ... End surface 43a, 43b, 43c, 43d ... Side surface 5 ... Solar cell 50 ... Light-receiving surface

Claims (8)

  An optical element of a concentrating solar power generation device made of a glass material having a flame-polished surface.   The optical element according to claim 1, wherein the glass material has a pair of end surfaces and side surfaces facing each other, and at least a part of the side surfaces is subjected to flame polishing.   The optical element according to claim 1, wherein the surface roughness of the flame-polished part of the surface of the optical element is 200 nm or less in terms of arithmetic average roughness (Ra).   The optical element according to claim 1, wherein the glass material includes an alkali component.   The optical element according to any one of claims 1 to 4, wherein the glass material is made of silicate glass. A solar cell, and a condensing optical system for focusing on the solar cell;
With
The concentrating optical system is a concentrating solar power generation apparatus having an optical element made of a glass material having a flame-polished surface.   A method for manufacturing an optical element of a concentrating solar power generation apparatus, wherein an optical element is obtained by flame polishing at least a part of a surface of a glass material.   The method of manufacturing an optical element according to claim 7, wherein flame polishing is performed by burner heating, high-frequency induction heating, or resistance heating.

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