JP3091755B1 - Concentrating solar power generator - Google Patents

Abstract

The present invention provides a concentrating photovoltaic power generation device in which the reflectance at the interface between a condensing device and a photoelectric conversion device is reduced, and the optical efficiency or the amount of generated power is substantially increased. A light-collecting device having a light-receiving surface and a reflecting surface, wherein a space sandwiched between the light-receiving surface and the reflecting surface is filled with a medium having a higher refractive index than the outside of the light-receiving surface. A concentrating solar power generation device having a photoelectric conversion device having a part of the surface in contact with the light collection device, wherein a refractive index of at least a region in contact with the photoelectric conversion device in the medium is other than that in the medium. It is higher than the refractive index of the region. Further, the refractive index of a region in contact with the light receiving surface in the medium is the lowest in the medium, and the refractive index of a region in the medium contacting the photoelectric conversion device is the highest in the medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concentrating photovoltaic power generation device, and more particularly to a technique effective when applied to reduce the reflectance at the interface between a condensing device and a photoelectric conversion device.

[0002]

2. Description of the Related Art There are two types of concentrator photovoltaic power generators: those that track sunlight and those that do not. The former is mainly used as a high-power concentrator of several tens to several hundreds of times, and the latter is used as a high-power concentrator.
It is used in a low-magnification light-condensing type of about twice to five times. This non-tracking, low-magnification, concentrator photovoltaic device, for example, "Prototype photovoltaic roof tiles",
Proceedings of the 13th European Photovoltaic Solar Energy Conference in 1990,
It is described on pages 1483 to 1486.
The concentrating device of this concentrating solar power generation device is generally formed of a medium having a higher refractive index than air, such as glass or acrylic, and a reflecting mirror surrounding a part of the medium. When the light reaches the light receiving surface of the light condensing device after being reflected by the reflecting mirror, light having a shallow angle with respect to the light receiving surface is totally reflected and can be confined. In addition, these concentrating solar power generation devices mainly use crystalline silicon solar cells as photoelectric conversion devices,
The surface has a texture structure that reduces the reflectance using double reflection.

[0003]

However, in the above-mentioned prior art, in view of the principle that sunlight rays incident from the outside of the condensing device must be collected in the photoelectric conversion device, some of the light incident on the photoelectric conversion device is used. The component enters the light receiving surface of the photoelectric conversion device at a shallow angle. In this case, light rays having an incident angle of 55 degrees or less with respect to the light receiving surface of the photoelectric conversion device cannot be double-reflected due to the texture structure, and therefore, the reflectance at the interface between the condensing device and the photoelectric conversion device is ideally reduced. It is difficult to do so, which has substantially reduced the optical efficiency. Also, compared to non-concentrating solar power generation devices, the concentrating solar power generation device receives the same amount of light but collects light in a narrower photoelectric conversion device, so the temperature of the photoelectric conversion device rises more. However, there is a problem that the characteristics are easily deteriorated. The present invention has been made in order to solve the problems of the prior art, and an object of the present invention is to reduce the angle of incidence of sunlight in a concentrator photovoltaic device, which is incident on a photoelectric conversion device. Accordingly, it is an object of the present invention to provide a technique capable of reducing the reflectance at the interface between the light-collecting device and the photoelectric conversion device and substantially increasing the optical efficiency or the amount of power generation. It is another object of the present invention to provide a concentrator photovoltaic power generation device that not only reduces the reflectance but also cools the photoelectric conversion device to prevent deterioration in characteristics. The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0004]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows. That is, the present invention has a light-collecting device having a light-receiving surface and a reflective surface, wherein a space sandwiched between the light-receiving surface and the reflective surface is filled with a medium having a higher refractive index than the outside of the light-receiving surface. A photovoltaic power generation device having a photoelectric conversion device having at least a part of a surface in contact with the light collection device, wherein a refractive index of at least a region of the medium that is in contact with the photoelectric conversion device is within the medium. Is characterized by being higher than the refractive index of other regions. Further, the present invention provides a light-collecting device having a light receiving surface and a reflecting surface, wherein a space sandwiched between the light receiving surface and the reflecting surface is filled with a medium having a higher refractive index than the outside of the light receiving surface. A photovoltaic device having at least a part of the surface and a photoelectric conversion device that is in contact with the condensing device, wherein a refractive index of a region of the medium that is in contact with the light receiving surface is the lowest in the medium. And a region in the medium that is in contact with the photoelectric conversion device has a highest refractive index in the medium. Further, the present invention provides a light-collecting device having a light receiving surface and a reflecting surface, wherein a space sandwiched between the light receiving surface and the reflecting surface is filled with a medium having a higher refractive index than the outside of the light receiving surface. A photovoltaic power generation device having a photoelectric conversion device having at least a part of a surface in contact with the light collection device, wherein the medium has a non-uniform refractive index, and a light beam passing through the medium. The angle of the photoelectric conversion device with respect to the normal direction of the light-receiving surface decreases each time the light passes through a region having a different refractive index. Further, the invention is characterized in that a cooling fluid having a higher refractive index than other media in the light-collecting device flows in a region of the medium in contact with the photoelectric conversion device.

[0005]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments, components having the same functions are denoted by the same reference numerals, and repeated description thereof will be omitted.

[First Embodiment] FIG. 1 is a sectional view of a main part showing a configuration of a concentrating solar power generation device according to a first embodiment of the present invention. FIG. 2 is a condensing device shown in FIG. FIG. 2 is an exploded perspective view showing the configuration of FIG. The light condensing device 1 has a triangular or trapezoidal cross section, and has different refractive indexes.
A seed prism (2, 3, 4) was used. The three kinds of prepared glasses are a flower crown glass 2 having a refractive index of 1.49, a heavy barium crown glass 3 having a refractive index of 1.62, and a tantalum flint glass 4 having a refractive index of 1.80. . As shown in FIG. 1, triangular sections having apical angles of 21 °, 19 °, and 17 ° in descending order of refractive index were prepared, and were cut out so that adjacent sides had the same length. These are adhered by ultraviolet curing resin,
Further, silver was deposited on the back surface of the prism to form a reflection surface 5. On the other hand, a double-sided solar cell 6 based on a p-type high-resistance crystalline silicon semiconductor was used as a photoelectric conversion device.

The manufacturing process of the concentrator photovoltaic power generation device according to the present embodiment is as follows. First, the base p
A texture is formed with potassium hydroxide solution on both sides of the high-resistance crystalline silicon semiconductor, and then phosphorus is diffused on one side. Subsequently, a nitride film is deposited on both surfaces by a CVD method, and finally, comb electrodes are formed on both surfaces by printing. The double-sided light-receiving solar cell 6 thus produced is shown in FIG.
(2), a double-sided solar cell 6 is bonded with an ethylene-vinyl acetate copolymer (EVA; hereinafter, simply referred to as EVA) so as to be sandwiched between the two concentrating devices 1 shown in FIG. I let it.

In the concentrator photovoltaic power generator according to the present embodiment, the light beam irradiated perpendicular to the light receiving surface of the concentrator 1 draws a locus 7 as shown in FIG. When a light beam passes through a boundary from a region having a low refractive index to a region having a high refractive index, the emission angle with respect to the interface becomes smaller than the incident angle, and finally the light beam is transmitted to the photoelectric conversion device (double-sided solar cell 6). It is possible to make it incident at an angle close to normal. This makes it possible to reflect most of the incident light twice on the texture formed on the surface of the photoelectric conversion device (double-sided light receiving solar cell 6). As a result, the effective reflectivity at the interface between the light condensing device 1 and the photoelectric conversion device (double-sided solar cell 6) decreases, and the short-circuit current increases.

Also, in the prism which is the condensing device 1, since a medium having a relatively high refractive index is used in a portion in contact with the photoelectric conversion device, the prism at the interface between the condensing device 1 and the photoelectric conversion device is also used in this case. It functions to reduce reflection and increase short-circuit current. In the present embodiment, the reflectance at the interface between the light-collecting device 1 and the photoelectric conversion device can be reduced by 7% as compared with the case where the light-collecting device 1 having a single refractive index is provided.
The fabricated concentrator photovoltaic power generation device has an optical efficiency of 85
%, And the light collection magnification was able to be increased to 5.8 times. In the present embodiment, as shown in FIG. 3, the condensing device 1 is formed by superposing wedge-shaped prisms (2, 3, 4) having a triangular cross section and having different refractive indices. It may be configured. In the light collecting device 1 according to the present embodiment, the refractive indexes are 1.49 and 1,49, respectively.
Although 1.62 and 1.80 glasses were used, if the transmittance is close to 100% in the wavelength region of visible light and the refractive index is different, the same light-collecting effect as in the present embodiment should be exhibited. Is possible. Further, in the present embodiment, the condensing device 1 is formed by combining prisms (2, 3, 4) having different refractive indexes. However, similar results can be obtained by using a prism whose refractive index is continuously changed. It is possible to get. Furthermore, in the present embodiment, a crystalline silicon solar cell having a double-sided comb-shaped electrode was used as the photoelectric conversion device. However, if double-sided light reception is possible, polycrystalline silicon, amorphous silicon,
It may be an IV compound or a II-VI compound solar cell.

[Embodiment 2] FIG. 4 is a diagram showing a configuration of a concentrator photovoltaic power generator according to Embodiment 2 of the present invention.
In the present embodiment, two pieces of white plate tempered glass 8 having a refractive index of 1.47 and a thickness of 2 mm and two heavy niobium flint glasses 9 having a refractive index of 1.83 and a thickness of 1.2 mm are used. A double-sided light-receiving solar cell 10 having a width of 20 mm and a cycle of 52 mm is adhered so as to sandwich it from both sides, and a reflection sheet 11 having a V-groove opened 120 degrees from the back is attached to complete a concentrating solar power generation device. I let it. That is, in the present embodiment, a condensing device is configured by combining glasses having different refractive indexes. At this time, the glass was an ultraviolet curable resin, the solar cell and the glass were adhered by EVA, and the gap 12 formed between the two glasses in the center was filled with EVA due to the thickness of the double-sided solar cell 10. Further, the space created between the V-groove of the reflection sheet 11 and the glass is EVA as it is.
Filled with. The completed flat plate type concentrating solar power generation device had a converging magnification of 2.6 times and an optical efficiency of 91%. In this embodiment, since the glass having a relatively low refractive index is used on the light receiving surface side of the light collecting device, the light collection magnification can be increased without increasing the reflectance of the light receiving surface of the light collecting device. . Moreover, since the refractive index of the glass is increased from the outside toward the center in parallel with the light receiving surface of the photoelectric conversion device (double-sided solar cell 10), the ray trajectory 1 shown in FIG.
As shown in 3, the light beam enters the light receiving surface of the photoelectric conversion device at an angle close to perpendicular. Thereby, the reflectance does not increase even at the interface between the light-collecting device and the photoelectric conversion device, and there is an effect of increasing the short-circuit current. In this embodiment, the light-collecting device is formed by combining glasses having different refractive indexes. However, the same result can be obtained by using two glasses whose refractive indexes are continuously changed. . Further, in the present embodiment, the same effect can be obtained by directly depositing titanium oxide on the white plate strengthened glass 8 instead of using the heavy niobium flint glass 9. The refractive index of titanium oxide slightly varies depending on the deposition method, conditions, and the like.
When the white plate tempered glass on which the titanium oxide of 100 nm was deposited was used, the power generation amount increased by about 3% compared to the above embodiment. Further, the thickness of the light-collecting device can be reduced to two-thirds, and the weight of the entire light-collecting solar power generation device can be reduced by 30% compared to the above embodiment.

[Embodiment 3] FIG. 5 is a perspective view showing the entire configuration of a concentrating solar power generation apparatus according to Embodiment 3 of the present invention, and FIG. 6 is a sectional view taken along the line AA 'of FIG. FIG. 3 is a cross-sectional view showing a cross-sectional structure taken along line BB ′. Concentrating solar cells tend to be hot due to their high light irradiation intensity. This causes deterioration of the characteristics of the solar cell, and particularly lowers the open-circuit voltage and the conversion efficiency. Therefore, in the present embodiment, the liquid 1 having a high refractive index is used instead of the glass having a high refractive index located below the dual-sided solar cell 10 of the second embodiment.
4 to be filled. A suction port 16 and a discharge port are provided in the frame 15 of the concentrator photovoltaic power generator so that the liquid can circulate. This allows
The two-sided solar cell 10 was liquid-cooled, and the problem of the temperature rise of the two-sided solar cell 10 could be solved while maintaining the above effects. Examples of the liquid 14 having a high refractive index include iodine or an iodine-based organic solvent. In this embodiment, methyl iodide having a refractive index of 1.74 is used. In the case of the present embodiment, although the medium having the refractive index of 1.74 was introduced in place of the medium having the refractive index of 1.80, the optical efficiency was slightly lowered. It is possible to return to. In the present embodiment, the liquid 14 having a high refractive index is filled in place of the glass having a high refractive index located below the double-sided solar cell 10. The same effect can be obtained even if the same liquid is filled instead of the located glass. In addition, originally, a liquid having a specific gravity slightly higher than 1 was sealed in a portion where glass having a specific gravity of 2 or more was inserted, so that the weight of the entire photovoltaic module could be reduced by about 20%. Thereby, when actually installing the concentrator photovoltaic power generator of the present embodiment, the burden on the operator can be significantly reduced. As described above, the invention made by the inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and can be variously modified without departing from the gist of the invention. Of course, it is.

[0012]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows. (1) According to the present invention, the incident angle at which sunlight enters the photoelectric conversion device can be reduced, so that the reflectance at the interface between the light-collecting device and the light receiving surface of the photoelectric conversion device is reduced, It is possible to substantially improve optical efficiency or power generation. (2) According to the present invention, the region in contact with the photoelectric conversion device in the medium of the light-collecting device is made of a fluid.
It is possible to suppress a rise in temperature of the photoelectric conversion device, suppress deterioration in characteristics of the photoelectric conversion device, and reduce the weight of the entire concentrating solar power generation device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing a configuration of a concentrating solar power generation device according to a first embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a configuration of the light collecting device shown in FIG.

FIG. 3 is a cross-sectional view of a main part showing another example of the light collecting device of the present embodiment.

FIG. 4 is a diagram illustrating a configuration of a concentrating solar power generation device according to a second embodiment of the present invention.

FIG. 5 is a perspective view showing an overall configuration of a concentrating solar power generation device according to Embodiment 3 of the present invention.

6 is a cross-sectional view showing a cross-sectional structure taken along line AA ′ and BB ′ shown in FIG.

[Explanation of symbols]

1. Concentrator, 2. Flower crown glass prism,
3: heavy barium crown glass prism, 4: tantalum flint glass prism, 5: reflection surface, 6, 10 ...
Double-sided light-receiving solar cell, 7, 13: ray trajectory, 8: white plate tempered glass, 9: heavy niobium flint glass prism, 11: reflection sheet, 12: gap, 14: liquid, 15
... frame, 16 ... inlet.

Continued on the front page (72) Inventor Ken Tsutsui 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Inside Hitachi, Ltd. Central Research Laboratory (72) Inventor Yoshiyoshi Miyamura 1-280, Higashi-Koigabo, Kokubunji-shi, Tokyo Hitachi, Ltd. Inside the Central Research Laboratory (72) Inventor Shinichi Muramatsu 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo Hitachi Central Research Laboratory (72) Inventor Junko Minemura 1-280, Higashi-Koigabo, Kokubunji-shi, Tokyo Hitachi Central Research Laboratory, Ltd. (56) reference Patent flat 11-266032 (JP, a) JP flat 10-221528 (JP, a) JP flat 8-128737 (JP, a) (58 ) investigated the field (Int.Cl. ⁷ , DB name) H01L 31/04-31/078

Claims (10)

(57) [Claims] A light-collecting device having a light-receiving surface and a reflecting surface, wherein a space sandwiched between the light-receiving surface and the reflecting surface is filled with a medium having a higher refractive index than the outside of the light-receiving surface; At least a part of the surface is a concentrating solar power generation device having a photoelectric conversion device in contact with the light collection device, wherein the refractive index of at least a region of the medium that is in contact with the photoelectric conversion device is within the medium. A concentrating solar power generation device having a higher refractive index than other regions. 2. A light-collecting device having a light receiving surface and a reflecting surface, wherein a space sandwiched between the light receiving surface and the reflecting surface is filled with a medium having a higher refractive index than the outside of the light receiving surface. A concentrator photovoltaic power generator having at least a part of the surface and a photoelectric conversion device that is in contact with the condensing device, wherein a refractive index of a region in the medium that is in contact with the light receiving surface is the lowest in the medium, A concentrating photovoltaic power generation device, wherein a refractive index of a region in the medium that is in contact with the photoelectric conversion device is the highest in the medium. 3. The light-converging type according to claim 1, wherein the refractive index in the medium gradually decreases as the distance from a region in contact with the photoelectric conversion device increases. Solar power generator. 4. The light condensing type according to claim 1, wherein the refractive index in the medium decreases continuously as the distance from a region in contact with the photoelectric conversion device increases. Solar power generator. 5. A light-collecting device having a light receiving surface and a reflecting surface, wherein a space sandwiched between the light receiving surface and the reflecting surface is filled with a medium having a higher refractive index than the outside of the light receiving surface. A concentrator photovoltaic power generator having at least a part of the surface and a photoelectric conversion device that is in contact with the light concentrator, wherein the medium has a non-uniform refractive index and a light beam that passes through the medium. A concentrator photovoltaic power generator, wherein the angle of the photoelectric conversion device with respect to the normal direction of the light receiving surface decreases each time the light passes through a region having a different refractive index. 6. The light- condensing device is provided with two light- condensing devices sandwiching the photoelectric conversion device, and the two light-condensing devices have a cross section including the light receiving surface, the reflection surface, and the photoelectric conversion device. The concentrator photovoltaic power generation device according to any one of claims 1 to 5 , wherein the reflection surface is configured by a straight line or a curve. 7. The concentrator photovoltaic power generator according to claim 1, wherein the photoelectric converter is provided in a medium of the concentrator. 8. The light-collecting device and the photoelectric conversion device,
The concentrating photovoltaic power generation according to claim 7, wherein the light receiving surface of the light condensing device, the reflection surface, and the light receiving surface of the photoelectric conversion device are arranged in parallel. apparatus. 9. The concentrating solar power generation device according to claim 1, wherein a region in the medium that is in contact with the photoelectric conversion device is formed of a fluid. . 10. The concentrator photovoltaic power generator according to claim 9, wherein the fluid is composed of iodine or an iodine-based organic solvent.