JP2018011459A - Concentrating solar battery system and power generation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concentrating solar battery system and a power generation method in which the solar battery is allowed to excellently receive scattered light reflected by a reflecting mirror, by which power can be generated at high output.SOLUTION: A concentrating solar battery system comprises: a reflecting mirror 20 which is parallel with an optical axis and includes at least one cross section having a macroscopically parabolic shape; and a receiver 30 which is parallel with the optical axis and has a built-in solar battery 10, in which the parabolic shape is in a shape which is expressed by a formula y=axand a is 0.8 or more and 8.0 or less, and a first light-receiving surface and a second light-receiving surface being both primary surfaces of receiver are irradiated with incident light reflected by the reflecting mirror 20.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a concentrating solar cell system and a power generation method using the concentrating solar cell system.

  The trough-type concentrating solar cell system collects sunlight on a solar cell using a reflector installed in the shape of a trough (rain gutter), thereby reducing the number of solar cells compared to a normal panel type solar cell module. Thus, the same degree of photoelectric conversion can be performed. It is also possible to collect thermal energy by passing a refrigerant or the like through a receiver that receives the condensed light.

  Many such trough-type concentrating solar cell systems have been reported (for example, Patent Document 1). Generally, a trough-type concentrating solar cell system collects sunlight incident parallel to the optical axis of a parabola in a solar cell installed near the focal point of the parabola by installing a reflecting mirror in a parabolic shape. It is possible to irradiate with light. Solar cells are known to improve open circuit voltage by condensing, and the output of solar cells can be expected to improve.

International Publication No. 2011/114861

R. Perez, R.A. Seals, J.M. Michalsky, All-weather model for sky luminance distribution-preliminary configuration and validation, Solar Energy, 50, (1993), p. 235-245.

However, the trough-type concentrating solar cell system can collect incident light (direct light) parallel to the optical axis of the parabola at the focal position, but incident light (scattered light) not parallel to the optical axis. ) Can hardly be focused and irradiated at the focal position.
Specifically, sunlight is scattered by clouds and surrounding buildings to generate scattered light, and most of such scattered light is directed to the solar cell disposed at the focal position of the trough-type concentrating solar cell system. There is a problem that it is not irradiated.

  The present invention has been made in view of the above-described problems, and allows a solar cell to favorably receive scattered light reflected by a reflecting mirror, and thereby a concentrating solar cell system capable of generating electric power at a high output. An object of the present invention is to provide a power generation method using the concentrating solar cell system.

The inventors have made a concentrating solar cell system parallel to the optical axis and a reflecting mirror including at least one cross section that is macroscopically parabolic, parallel to the optical axis, The above-mentioned parabolic shape is expressed by the equation y = ax ² and a is 0.8 or more and 8.0 or less, and is reflected by the reflecting mirror. It has been found that the above problems can be solved by irradiating incident light onto the first light receiving surface and the second light receiving surface, which are both main surfaces of the receiver, and the present invention has been completed. Specifically, the present invention provides the following.

That is, the present invention
(I) A concentrating solar cell system including a reflecting mirror and a receiver,
The reflector includes at least one cross section that is parallel to the optical axis and macroscopically parabolic,
A parabolic shape is a shape represented by the formula y = ax ² and a is 0.8 or more and 8.0 or less,
The receiver has a plate shape parallel to the optical axis, and extends in a direction perpendicular to at least one of the aforementioned cross sections.
The receiver has a first light receiving surface and a second light receiving surface on the back side of the first light receiving surface, and a solar cell is disposed therein,
A concentrating solar cell system in which incident light reflected by the reflecting mirror is collected and then irradiated to the solar cell through both the first light receiving surface and the second light receiving surface, and
(Ii) Provided is a power generation method including performing power generation by irradiating sunlight to the concentrating solar cell system according to (i).

  ADVANTAGE OF THE INVENTION According to this invention, the scattered light reflected by a reflective mirror can be favorably received by a solar cell, and thereby the concentrating solar cell system which can generate electric power with high output, and the said concentrating solar cell system are used. And a power generation method.

It is a figure which shows the outline of a concentrating solar cell system provided with a trough-type reflective mirror. It is a figure which shows typically the cross section of a concentrating solar cell system provided with the reflective mirror comprised from a some strip-shaped mirror. It is a figure which shows typically the relationship between the width Wm of the strip-shaped mirror which comprises a reflective mirror, and the width Ws of the optical axis direction of a solar cell. It is a figure which shows typically the relationship between the shape of a reflective mirror, and the range of the scattered light which can be received with a solar cell. It is a figure which shows typically the cross section of a concentrating solar cell system provided with the receiver provided with a single solar cell inside, and the reflective mirror comprised from a some strip-shaped mirror. It is a figure which shows typically the cross section of a receiver provided with a single solar cell inside. It is a figure which shows typically the cross section of a concentrating solar cell system provided with the receiver provided with two solar cells inside, and the reflective mirror comprised from a some strip-shaped mirror. It is a figure which shows typically the cross section of a receiver provided with two solar cells and the cooling part between two solar cells inside. It is a figure which shows the variation of the shape of a reflective mirror. It is a figure which shows the relationship between the shape of a parabola and the taking-in rate of scattered light. It is a figure which shows the relationship between the shape of the parabola for every weather, and the taking-in rate of scattered light.

  Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. can do.

≪Concentrated solar cell system≫
The concentrating solar cell system includes a reflecting mirror and a receiver.
The reflecting mirror includes at least one cross section that is parallel to the optical axis and macroscopically parabolic.
For a cross section having a parabolic shape, the parabolic shape is a shape represented by the formula y = ax ² and a is 0.8 or more and 8.0 or less.
The receiver has a plate shape parallel to the optical axis and extends in a direction perpendicular to at least one of the aforementioned cross sections.
The receiver has a first light receiving surface and a second light receiving surface on the back side of the first light receiving surface, and a solar cell is disposed inside.
Incident light reflected by the reflecting mirror is collected and then applied to the solar cell through both the first light receiving surface and the second light receiving surface.

As described above, the reflecting mirror includes at least one cross section that is macroscopically parabolic as a cross section parallel to the optical axis.
In the present specification, “a cross section that is macroscopically parabolic” may be referred to as a “parabolic cross section”.
Moreover, when there is no special description about "macroscopic parabolic shape" or "parabolic cross section", such a cross section is "a cross section parallel to the optical axis".
Furthermore, “parallel” or “vertical” in the present specification and claims includes not only geometrical parallel or vertical but also substantially parallel or substantially vertical to the extent that it can be recognized as parallel or vertical visually.

Here, when all the parabolic cross sections included in the reflecting mirror are parallel to each other and have the same shape, the reflecting mirror includes one parabolic cross section.
Also,
-When the reflecting mirror has the same parabolic shape, but includes n types of parabolic sections that are not parallel to each other,
The reflector includes n parabolic sections that are parallel to each other but of different shapes; and
When the reflector includes n kinds of parabolic sections that are not parallel to each other and have different shapes,
Suppose that the reflector includes n parabolic cross sections.
In addition, when the shape of the parabolic cross section changes continuously, it is clear that the reflector includes at least one macroscopic parabolic cross section, while the number of types of parabolic cross sections may not be specified. is there.

In the conventional concentrating solar cell system described in Patent Document 1 described above, direct light incident in a direction parallel to the optical axis is collected at the focal position of the reflecting mirror (see FIG. 1). 2, see FIG. 4 and FIG. For this reason, in the conventional concentrating solar cell system, attention is paid only to high-efficiency power generation from the condensed direct light, and a cylindrical rod-shaped solar cell is arranged at the focal position of the reflecting mirror.
However, the scattered light reflected by the reflecting mirror is reflected at a location shifted from the focal position of the reflecting mirror. For this reason, in the conventional concentrating solar cell system, the scattered light cannot be sufficiently utilized for power generation.
In this regard, in a concentrating solar cell system, when a receiver that is plate-shaped parallel to the optical axis and incorporates a solar cell is used, not only reflected direct light but also reflected scattered light is reflected by the receiver. Light can be received by the first light receiving surface and the second light receiving surface which are both main surfaces.
In addition, since the receiver has a plate shape parallel to the optical axis, there is almost no influence of the light incident on the reflecting mirror by the receiver.
For this reason, the power generation efficiency of the concentrating solar cell system is improved by using a combination of a reflecting mirror having a parabolic cross section and a receiver having a plate shape parallel to the optical axis and incorporating a solar cell.

As described above, in a concentrating solar cell system that uses a reflecting mirror including a parabolic cross section, it is possible to condense direct light, but it is difficult to condense much of scattered light.
For this reason, it is necessary to improve the efficiency of capturing scattered light in the receiver in order to improve the output in the system.
In order to improve the efficiency of capturing scattered light, the condensing magnification of the concentrating solar cell system is preferably in the range of 2 to 20 times. By collecting light with such a low light collection magnification, the receiver has a certain width with respect to the parabola formed by the reflecting mirror. For this reason, it is easier to capture more scattered light than a system with a high condensing magnification that collects light with respect to a parabola. The light collection magnification here is based on the amount of current when a solar cell is placed under AM 1.5G (1 sun), and what is the current obtained in the concentrating solar cell system under the same light source. Define by doubling.

According to the above-described reflecting mirror, good power generation is performed mainly by converging direct light parallel to the optical axis at the focal point. If there is no problem even with short-time power generation, a concentrating solar cell system including a reflecting mirror fixed in a position and direction in which direct light is easily received may be used.
On the other hand, in general, it is often desired that good power generation be performed for as long a time as possible. For this reason, it is preferable that the concentrating solar cell system can track the sun so that the optical axis, which is the incident direction of the direct light from the sun, and the symmetry axis of the radiation section always coincide.
The tracking method is not particularly limited. For example, a method of tracking the sun from the east to the west by rotating the reflecting mirror and the receiver according to the rotation axis along the north-south direction is preferable in the day sun tracking.
Such tracking may be uniaxial tracking in which a rotation axis along the north-south direction is installed parallel to the ground.
In addition to tracking according to the first rotation axis installed along the north-south direction and parallel to the earth's axis, the optical axis and the incident direction of the direct light coincide with the seasonal variation of the solar altitude. As described above, two-axis tracking may be used in which the reflecting mirror and the receiver are rotated according to the second rotation axis.
As such two-axis tracking, it is preferable to use an equatorial mount method that is well-known as a tracking method applied to the base of the astronomical telescope.

  Hereinafter, the concentrating solar cell system will be described with reference to the drawings. In each figure, dimensional relationships such as thickness and length are appropriately changed for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

FIG. 1 is a diagram showing an outline of a concentrating solar cell system including a trough-type (rain gutter) reflecting mirror 20, which is a preferred embodiment of the concentrating solar cell system. The concentrating solar cell system including the trough-type reflecting mirror 20 is preferable in that the reflecting mirror 20 and the receiver 30 can be easily formed and can be manufactured at low cost. The shape of the reflecting mirror 20 is not limited to the trough type.
The trough-type reflecting mirror 20 extends linearly in the first direction shown in FIG. In addition, the shape of the cross section A perpendicular to the first direction of the trough-type reflecting mirror 20 is macroscopically a parabola having an optical axis perpendicular to the first direction as an axis of symmetry at any position. Shape.
Further, the plurality of parabolic sections included in the trough-type reflecting mirror 20 have the same shape.
The incident light reflected by the reflecting mirror 20 is collected inside the recess formed by the reflecting mirror 20 and then irradiated to the first light receiving surface and the second light receiving surface which are both main surfaces of the receiver 30. As described above, a receiver 30 that extends linearly in the first direction and includes the solar cell 10 therein is disposed near the focal point of the reflecting mirror 20.
Thereby, the solar cell 10 can utilize efficiently the reflected light which injects from a 1st light-receiving surface, and the reflected light which injects from a 2nd light-receiving surface, and can generate electric power with high efficiency.

In the concentrating solar cell system shown in FIG. 1, the reflecting mirror 20 and the receiver 30 may extend in any length in the first direction.
In particular, when performing uniaxial tracking, the length of the reflecting mirror 20 and the receiver 30 in the first direction is sufficiently long, for example, several tens of meters, so that the collection loss of sunlight due to seasonal variation can be reduced. .
Explain the solar collection loss due to seasonal variations. For example, in the winter season, the solar altitude is low even at the time of South and Central. When the solar altitude is low, in the uniaxial tracking trough type concentrating solar cell system in which the rotation axis is set in the north-south direction, the south-side reflector is irradiated with sunlight from an oblique angle on the north-south surface. There is a case where the solar cell is not irradiated with light and a collection loss of sunlight occurs. For this reason, in the trough-type concentrating solar cell system as shown in FIG. 1, the ratio of the collection loss of sunlight mainly generated in winter is reduced by making the reflector 20 and the receiver 30 sufficiently long. Can be made.

The reflecting mirror 20 and the receiver 30 incorporating the solar cell 10 described above are installed on a gantry not shown in FIG. As described above, the gantry may include a tracking mechanism for tracking the sun.
Hereinafter, the reflecting mirror 20 and the receiver 30 which are main components of the concentrating solar cell system will be described.

<Reflector>
As described above, the reflecting mirror 20 includes at least one macroscopic parabolic cross section (parabolic cross section) as a cross section parallel to the optical axis.
In the reflecting mirror 20, the parabolic cross section is preferably continuous, but it is not always necessary.
For example, in the trough-type reflecting mirror 20 described above, a concave portion or a convex portion may be provided on at least a part of the reflecting mirror for the convenience of installing the reflecting mirror 20 on the gantry. In this case, the shape of the cross section at the position corresponding to the concave portion or the convex portion is not a parabolic shape, and the parabolic cross section of the reflecting mirror 20 is discontinuous.

  Like the trough-type reflector 20 described above, the shape of the reflector 20 is preferably the shape of a trajectory when the parabolic shape continuously moves. The shape of the reflecting mirror 20 may be the shape of a trajectory formed by moving in a curved line, but the shape of the trajectory formed by moving in a straight line (that is, trough type) The reflecting mirror 20 is preferable because it is easy to manufacture and the reflecting mirror 20 is small.

For example, as shown in FIG. 2, the reflecting mirror 20 may be composed of a plurality of strip-shaped plane mirrors. FIG. 2 is a schematic view of a cross section including a parabolic cross section of a concentrating solar cell system including a reflecting mirror composed of a plurality of strip-shaped plane mirrors, as viewed from a direction perpendicular to the parabolic cross section.
The reflecting mirror 20 is preferably composed of two or more types of strip-shaped flat mirrors having different short side lengths. In FIG. 2, the reflecting mirror 20 is comprised from the strip type plane mirrors 20a-21g of a total of seven types.
In this case, it is preferable that the plane mirrors 20a to 21g constitute a tangent to the parabola on the same cross section as the parabola cross section, and are arranged so that the plane mirrors do not overlap. By doing so, sunlight can be efficiently condensed on the receiver 30 without causing a shadow by another plane mirror on the plane mirror.

As shown in FIG. 2, when the reflecting mirror 20 is configured using a plurality of types of plane mirrors, the plurality of plane mirrors 20a to 20g preferably have different short side widths Wm.
Hereinafter, a preferable range of the short side width Wm of the strip-shaped reflecting mirror will be described with reference to FIG. FIG. 3 is an enlarged view of a part of FIG. In FIG. 3, for convenience, only the solar cell 10 in the receiver 30 is illustrated, and the receiver 30 is not illustrated.
In FIG. 3, the width in the optical axis direction of the solar cell 10 is Ws, the width of the short side of the strip-shaped flat mirror 20c is Wm, the incident angles of the direct light 1 and the direct light 2 to the flat mirror 20c are α, When the incident angle of the reflected light to the battery 10 is β, Wm and Ws are expressed by the following formula:
Wm ≦ 2sin (α) × Ws
It is preferable to satisfy this relationship.
In FIG. 3, the relationship between the short side width of the plane mirror 20c and the width in the optical axis direction of the solar cell 10 is described as an example, but the short side width of the plane mirror other than the plane mirror 20c and the optical axis direction of the solar cell 10 The same applies to the relationship with the width.
If the short side width of the plane mirror and the width in the optical axis direction of the solar cell 10 are in the above relationship, the reflected light of the direct light is evenly applied to the main surface of the solar cell 10, and light collection loss, Electric resistance loss and the like in the battery 10 can be suppressed.

The shape of the parabola with respect to the parabola cross section is the shape of a parabola that satisfies 0.8 ≦ a ≦ 8.0 when the parabola is expressed by the equation y = ax ² . The range of a described above is preferably 1.0 ≦ a ≦ 6.0, and more preferably 2.0 ≦ a ≦ 4.5.
As shown in FIG. 4A, with respect to the shape of the parabola, when a in the above formula is small, the distance between the solar cell 10 installed near the focal point of the parabola and the reflecting mirror 20 composed of the plane mirrors 20a to 20m. Is long. If it does so, only the narrow range scattered light shown by the broken-line arrow in Fig.4 (a) can condense to the solar cell 10. FIG.
On the other hand, as shown in FIG. 4B, the shape of the parabola is wider because the distance between the reflecting mirror 20 formed by the plane mirrors 20a to 20g and the solar cell 10 is shorter when a in the above formula is large. Easy to capture scattered light in the range. As a result, improvement in solar cell output is expected.
However, if “a” in the above equation is excessive, the opening of the reflecting mirror is narrowed, so that a large amount of direct light and scattered light are hardly incident on the reflecting mirror 20. If direct light and scattered light do not sufficiently enter the reflecting mirror 20, it is difficult to sufficiently collect light on the solar cell 10.
For the reason described above, regarding the shape of the parabola with respect to the parabolic cross section, in the above formula, if 0.8 ≦ a ≦ 8.0, both the direct light and the scattered light can be favorably condensed on the solar cell 10. High power and easy power generation.

  The material of the reflecting mirror 20 is not particularly limited as long as it is a material having high reflection characteristics in the sensitivity wavelength region of the solar cell 10 and high reliability against outdoor exposure. Preferable specific examples of the material of the reflecting mirror 20 include aluminum and silver, an alloy containing aluminum and / or silver, and the like.

<Receiver>
The receiver 30 is plate-shaped parallel to the optical axis and extends in a direction perpendicular to at least one of the parabolic cross sections. The receiver 30 has a first light receiving surface and a second light receiving surface on the back side of the first light receiving surface as two main surfaces. And the solar cell 10 is arrange | positioned inside the receiver 30. FIG.

Hereinafter, the receiver 30 will be described with reference to FIGS. 5 and 6.
FIG. 5 shows a schematic diagram of a cross section including a parabolic cross section of the concentrating solar cell system as viewed from a direction perpendicular to the parabolic cross section.
The concentrating solar cell system shown in FIG. 5 includes a reflecting mirror 20 including a plurality of strip-shaped flat mirrors 20 a to 20 g and a receiver 30 in which the solar cell 10 is built.
The direct light from the sun is ideally incident on the reflecting mirror 20 parallel to the optical axis in FIG. At this time, the direct light and scattered light reflected by the reflecting mirror 20 are both main surfaces (first main surface and second main surface) of the plate-like solar cell 10 disposed inside the plate-like receiver 30. Is irradiated.

FIG. 6 is an enlarged view of the cross section of the receiver 30 in FIG. The type of the solar cell 10 disposed in the receiver 30 is not particularly limited as long as it can receive light and generate power on both surfaces (first main surface and second main surface) of the solar cell 10.
Examples of preferable solar cells include a crystalline silicon solar cell in which grid electrodes are formed on both sides, a back contact type crystalline silicon solar cell in which electrodes are concentrated on only one side, and the like. In the back contact type crystalline silicon solar cell, both p-type and n-type semiconductor layers are arranged on one side, and the metal electrodes are also arranged only on one side, but by providing a sufficient space between the metal electrodes. It is possible to receive light on both sides.
Hereinafter, the back contact type crystalline silicon solar cell will be described more specifically. The back contact type crystalline silicon solar cell is a back junction type solar cell in which a p-type semiconductor layer and an n-type semiconductor layer are disposed in contact with each other on one main surface of a crystalline silicon substrate.
As a preferable example of the back contact type crystalline silicon solar cell, a plurality of p-type semiconductor layers spaced apart from each other and a plurality of n-type semiconductor layers spaced apart from each other are disposed on one main surface of the crystalline silicon substrate. Things. Here, each of the p-type semiconductor layer and the n-type semiconductor layer is formed on one main surface of the crystalline silicon substrate substantially via the intrinsic i-type semiconductor layer.
Such a back contact type crystalline silicon solar cell is described in, for example, International Publication No. 2013/133005.
In this preferable back contact type crystalline silicon solar cell, the plurality of n-type semiconductor layers are formed by exposing portions of the surface of the p-type semiconductor layer that are not covered with the p-type semiconductor layer in the main surface of the crystalline silicon substrate. And covering the p-type semiconductor layer in contact therewith. In this case, the end portion of the n-type semiconductor layer is disposed immediately above the end portion of the p-type semiconductor layer.
In the pack contact type crystalline silicon solar cell described above, metal electrodes are provided on the respective surfaces of the plurality of p-type semiconductor layers and the plurality of n-type semiconductor layers, and current is extracted from the metal electrodes.
The solar cell 10 is preferably a solar cell that can receive light from both sides, such as a crystalline silicon solar cell having grid electrodes on both sides, and a back contact type crystalline silicon solar cell having a sufficient space between metal electrodes. . Further, a plurality of solar cells 10 may be continuously arranged in the receiver 30 along the direction in which the receiver 30 extends.
The solar cell 10 may be configured by arranging two solar cells at positions close to each other so that the light-receiving surface is on the surface protective material 50a and 50b side. In this case, a solar cell that can receive light only on one side can be used.

  In the receiver 30, the solar cell 10 is preferably sealed with a transparent sealing material 40. Although the sealing material 40 may be an organic material or an inorganic material, an organic material such as a resin can be used because it is easy to process and is lightweight. Examples of the transparent resin material that can be used as the sealing material 40 include EVA (ethylene vinyl alcohol copolymer). The transparent resin material used as the sealing material 40 includes various additives such as an ultraviolet absorber, an antioxidant, a flame retardant, a flame retardant aid, and a plasticizer as long as the transparency is not significantly impaired. May be.

It is preferable to provide surface protective materials 50a and 50b on both main surfaces of the plate-shaped sealing material 40 enclosing the solar cell 10. By providing the surface protection members 50a and 50b, it is easy to suppress the occurrence of scratches on the first light receiving surface and the second light receiving surface of the receiver 30 and damage to the solar cell 10 in the receiver 30.
The material of the surface protective materials 50a and 50b may be an organic material or an inorganic material as long as the material has durability that can withstand long-term exposure outdoors. For example, glass plates can be preferably used as the surface protective materials 50a and 50b. Further, as the material of the surface protective materials 50a and 50b, a resin for a hard coat material used for various purposes can be used. The surface protective materials 50a and 50b may be formed using a hard coat film, or after the hard coat forming coating liquid is applied to both main surfaces of the sealing material 40, the coating film is heated. Or may be formed by exposure or the like.

  Since the receiver 30 having the structure shown in FIG. 6 has a simple structure, it can be easily formed and is low in cost.

As described above, the single solar cell 10 capable of receiving light on both sides or the receiver 30 including the plurality of solar cells 10 arranged close to each other has been described above. However, the receiver 30 includes two solar cells 10 inside. You may have.
Specifically, the receiver 30 may include a first solar cell 10a and a second solar cell 10b on the first light receiving surface side and the second light receiving surface side, which are the two main surfaces, respectively.
The schematic diagram which looked at the cross section containing the parabolic cross section of a concentrating solar system provided with the receiver 30 of this structure and the reflective mirror 20 which consists of several strip-shaped plane mirrors 20a-20g from the perpendicular | vertical direction with respect to the parabolic cross section. Is shown in FIG.

In FIG. 8, the first solar cell 10a is arranged in the receiver 30 so that incident light incident through the first light receiving surface is received by the first main surface of the first solar cell 10a.
The second solar cell 10b is disposed in the receiver 30 so that incident light incident through the second light receiving surface is received by the first main surface of the second solar cell.
In the concentrating solar cell system, ideally, direct light from the sun enters the reflecting mirror 20 parallel to the optical axis. In this case, the direct light and scattered light reflected by the reflecting mirror 20 are incident on the first light receiving surface and the second light receiving surface of the receiver 30 as described above.
In this regard, when the first solar cell 10a and the second solar cell 10b are arranged in the receiver as shown in FIG. 8, the light incident on the first light receiving surface and the light incident on the second light receiving surface Power generation with high efficiency.

When providing the 1st solar cell 10a and the 2nd solar cell 10b in the receiver 30, various solar cells can be used as a 1st solar cell 10a and a 2nd solar cell 10b without a restriction | limiting in particular.
Examples of preferred solar cells include crystalline silicon solar cells, thin film silicon solar cells, III-V group solar cells, CdTe solar cells, perovskite solar cells, chalcopyrite solar cells (for example, CIGS solar cells), dye enhancement A sensitive solar cell, an organic solar cell, etc. are mentioned. In particular, a crystalline silicon solar cell is preferably a back contact solar cell from the viewpoint of reducing a light shielding loss due to a metal electrode.

  When the receiver 30 includes the first solar cell 10a and the second solar cell 10b on the first light receiving surface side and the second light receiving surface side, respectively, the first sun sealed in the sealing material 40a and the sealing material 40b, respectively. It is also preferable that the base material 60 that supports the battery 10a and the second solar battery 10b on both surfaces thereof includes the cooling unit 70 therein. A cross section of the receiver 30 is schematically shown in FIG.

When the receiver 30 includes the cooling unit 70 therein, the refrigerant can be circulated in the cooling unit 70. In this case, the heat generated by the incident light incident on the first solar cell 10a and the second solar cell 10b is transmitted to the refrigerant through the substrate 60, and the refrigerant flowing through the cooling unit 70 is heated. Thereby, the thermal energy generated in the receiver 30 is taken out of the concentrating solar cell system.
When the refrigerant is water, hot water is obtained by extracting heat energy. The obtained hot water is not particularly limited and can be used for various applications in which hot water has been conventionally used.
The hot water obtained by taking out the thermal energy can be used in agriculture for the purpose of promoting the growth of crops in winter, for example. The hot water can also be used for the purpose of heating (for example, floor heating) in an apartment house or hot water supply to a bathroom or the like.
When the temperature of the hot water is not as high as desired, the hot water may be used after being heated to a desired temperature using an apparatus such as a water heater (boiler).

  The refrigerant is not particularly limited and may be gas or liquid, and liquid is preferable in terms of heat transfer efficiency. As the liquid, a liquid that has been conventionally used as a refrigerant in various apparatuses can be used without particular limitation. Water is preferable as the liquid used as the refrigerant because it is inexpensive, has no danger of ignition or ignition, and has few problems at the time of leakage. When water is circulated through the cooling unit 70, various agents such as a scale inhibitor, a pH adjuster, a chelating agent, an antifoaming agent, a slime control agent, an antifungal agent, and an antiseptic can be added to the water. Good.

The material of the substrate 60 is preferably a material having high thermal conductivity such as aluminum or stainless steel.
Since the assembly of the receiver is easy, it is preferable that the base material 60 is divided into two parts, that is, a base material 60a and a base material 60b, as shown in FIG. In such a case, the base material 60a and the base material 60b are joined, and the cooling unit 70 is formed inside of both.

  The shape of the cooling unit 70 is not particularly limited. From the viewpoint that the cooling unit 70 can be easily formed, a single cooling unit 70 may be provided in the substrate 60. Further, since the heat transfer area is increased and the heat transfer efficiency can be increased, two or more cooling units 70 may be provided in the base material 60. In addition, in FIG. 8, the cross section of the receiver 30 which has the single cooling unit 70 is shown.

  In addition, a fine uneven pattern may be formed on the surface defining the cooling unit 70 of the base material 60 to increase the heat transfer efficiency between the refrigerant flowing through the cooling unit 70 and the base material 60. The shape of the uneven pattern is not particularly limited. Preferred pattern shapes include a line and space pattern composed of lines (convex portions) and spaces (concave portions), a dot pattern in which dots (convex portions) are scattered on the surface (concave portions) of the base material 60, and the base material 60. It may be a hole pattern in which holes (concave portions) are scattered on the surface (convex portion).

As described above, when a concentrating solar cell system including the reflector 20 described above and a receiver incorporating the solar cell 10 is used, not only direct light but also scattered light can be used effectively, and power can be generated with high efficiency.
In particular, as in Japan, in areas where there is little clear weather with cloudiness of 1 or less and there are many sunny or cloudy weather with cloudiness of 2 or more, the ratio of scattered light in all components of sunlight due to the scattering of sunlight by clouds. Is often 20% or more.
However, according to the concentrating solar cell system described above, even when the ratio of scattered light in all components of sunlight is 20% or more, the scattered light can be favorably used for power generation.

<Simulation>
Hereinafter, as an example, the effect of the trough-type concentrating solar cell system shown in FIG. 2 will be specifically described using simulation results. In addition, the effect regarding a concentrating solar cell system and its condensing efficiency is not limited to the trough concentrating solar cell system and the condensing effect shown in FIG.

Here, the relationship between the value of the coefficient a in the equation y = ax ² regarding the parabolic shape and the capture rate (%) of scattered light was examined by optical simulation.
For the optical simulation, ray tracing optical simulation software (Lighttools, manufactured by Cybernet) was used.
As a condition of the solar cell, use of a crystalline silicon solar cell having a corner of 7.8 cm was set.
As the coefficient a in the formula representing the parabolic shape, seven values of 0.3, 0.4, 1.1, 2.0, 3.8, 5.6, and 10.0 are set, and each value is set. Scattered light uptake rate (%) of the trough-type concentrating solar cell system was calculated.
In addition, about scattered light, light was equally irradiated from all directions, and it was investigated how much of the light was taken in by the solar cell.
In addition, as the reflecting mirrors, the setting range of the reflecting mirrors was set so that the reflecting mirrors on the left and right sides in FIG. The length of the short side of each plane reflector is the length of the short side (Wm) of the plane mirror and the width (Ws) of the solar cell in the optical axis direction.
Wm ≦ 2sin (α) × Ws).
FIG. 10 shows the calculation result. As can be seen from FIG. 10, about 10% or more of scattered light is captured when 0.8 ≦ a ≦ 8.0, and further about 15% when 1.0 ≦ a ≦ 6.0. As described above, it is understood that about 17% or more of scattered light is captured when 2.0 ≦ a ≦ 4.5.
Further, in the above calculation, uniform scattered light is assumed from all sides, but the same study was performed on scattered light in clear sky and cloudy sky using Perez Sky Diffuse Model (Non-Patent Document 1). The result is shown in FIG. In this case as well, similar results are shown, and it was found that good capture of scattered light can be expected at a specific coefficient a.

≪Modification≫
The concentrating solar cell system is not limited to the embodiment described above, and various modifications and changes can be made. For example, the shape of the reflecting mirror 20 can be variously changed from the trough shape shown in FIG. 1 as long as a predetermined condition is satisfied.

As shown in FIG. 9, the shape of the reflecting mirror 20 may be a trajectory shape in which a parabola shape moves along a curved line. In this case, in consideration of the focal position of the parabolic cross section of the reflecting mirror 20, the plate-like receiver 30 bent along the curve of the opening of the reflecting mirror 20 is parallel to the optical axis in the recess formed by the reflecting mirror 20. Placed in.
Here, the reflecting mirror 20 curved in the direction perpendicular to the optical axis has been described, but the reflecting mirror may be curved in a direction parallel to the optical axis. In this case, the reflecting mirror may be convex toward the opening side or may be convex toward the side opposite to the opening side.

  When the reflecting mirror 20 having the shape shown in FIG. 9 is used, there is an advantage that the light receiving area of the solar cell 10 can be increased with the same installation width as that of the concentrating solar cell system including the trough-type reflecting mirror 20.

DESCRIPTION OF SYMBOLS 10 Solar cell 20 Reflecting mirror 30 Receiver 40 Sealing material 50a, 50b Surface protection material 60 Base material 70 Cooling part

Claims (13)

A concentrating solar cell system comprising a reflector and a receiver,
The reflecting mirror includes at least one cross section parallel to the optical axis and macroscopically parabolic,
The parabolic shape is a shape represented by the formula y = ax ² and the a is 0.8 or more and 8.0 or less,
The receiver has a plate shape parallel to the optical axis and extends in a direction perpendicular to at least one of the cross sections;
The receiver has a first light receiving surface and a second light receiving surface on the back side of the first light receiving surface, and a solar cell is disposed therein,
A concentrating solar cell system in which incident light reflected by the reflecting mirror is collected and irradiated to the solar cell through both the first light receiving surface and the second light receiving surface.   2. The concentrating solar cell system according to claim 1, wherein the concentrating solar cell system includes one of the macroscopic parabolic shapes and has a trough shape. The solar cell has a first main surface and a second main surface on the back side of the first main surface,
The concentrating solar cell system according to claim 1 or 2, wherein incident light incident through the first light receiving surface and the second light receiving surface is irradiated to the first main surface and the second main surface, respectively. The receiver has a first solar cell on the first light receiving surface side and a second solar cell on the second light receiving surface side,
The first main surface of the first solar cell and the first main surface of the second solar cell are arranged on the first light receiving surface side and the second light receiving surface side, respectively.
Incident light incident through the first light receiving surface and the second light receiving surface is irradiated to the first main surface of the first solar cell and the first main surface of the second solar cell, respectively.
3. The concentrating solar cell system according to claim 1, further comprising a cooling unit that circulates a refrigerant between the first solar cell and the second solar cell. The refrigerant is heated using thermal energy generated by incident light incident on the first solar cell and the second solar cell,
The concentrating solar cell system according to claim 4, wherein thermal energy is extracted by moving the refrigerant. The surface of the reflecting mirror is composed of a plurality of strip-shaped mirrors,
The concentrating solar cell system according to any one of claims 1 to 5, wherein a mirror surface of the strip-shaped mirror is a flat surface. The plurality of strip-shaped mirrors include two or more strip-shaped mirrors each having a short side length,
The concentrating solar cell system according to claim 6, wherein incident light reflected by each strip-shaped mirror falls within the first light receiving surface or the second light receiving surface of the receiver.   The concentrating solar cell system according to any one of claims 1 to 7, wherein the condensing magnification is 2 to 20 times.   The concentrating solar cell system according to any one of claims 1 to 8, which is a tracking type.   The concentrating solar cell system according to claim 9, which has a rotation axis parallel to the earth axis.   The concentrating solar cell system according to any one of claims 1 to 10, wherein the solar cell is a back contact solar cell.   The power generation method including irradiating sunlight to the concentrating solar cell system according to any one of claims 1 to 11 to generate power.   The power generation method according to claim 12, wherein a ratio of scattered light in the sunlight is 20% or more.

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