JP4253191B2

JP4253191B2 - Concentrating solar power generator

Info

Publication number: JP4253191B2
Application number: JP2003000791A
Authority: JP
Inventors: 道雄近藤; 建次荒木; 敏夫江上; 雅男平松; 憲徳宮崎
Original assignee: Daido Steel Co Ltd; Daido Metal Co Ltd
Current assignee: Daido Steel Co Ltd; Daido Metal Co Ltd
Priority date: 2003-01-07
Filing date: 2003-01-07
Publication date: 2009-04-08
Anticipated expiration: 2023-01-07
Also published as: JP2004214470A

Description

【０００１】
【発明の属する技術分野】
本発明は集光レンズによって太陽電池面に太陽光を集光するようにした集光式太陽光発電装置に関し、特に、追尾誤差やレンズ組付け誤差等の影響を受けることなく太陽電池面の照度を均一に保って安定した発電を行えるようにした集光式太陽光発電装置に関する。
【０００２】
【従来の技術】
集光式太陽光発電装置は常に太陽方向へ向けた集光レンズによって比較的小径の太陽電池面に太陽光を集光して効率的な発電を行うものである。集光レンズとしてはフレネルレンズを使用することが多い。このような集光式太陽光発電装置において、追尾誤差やフレネルレンズの組付け誤差等によって集光レンズの向きが僅かに太陽方向から外れると太陽電池の受光面上の照度が急激に低下して発電量が大きく損なわれる。そこで、従来は、集光レンズと太陽電池の間に二次集光器を設けて、集光レンズから射出される光束が正規方向から多少振れても、二次集光器の内部で反射させることによって上記光束を太陽電池の受光面へ常に確実に入射させるようにしている（特許文献１）。
【０００３】
一方、フレネルレンズとしては、製造やメンテナンスが容易等の理由で平板フレネルレンズが多用される。平板フレネルレンズ１の一例を図４に示す。図４において、平板１２には表面側に略三角プリズム断面の同心円環状の突条１１が多数形成され、各突条１１の三角プリズムの頂角θｔは通常、平板１２面に対して垂直で、プリズム斜面に対し入射角θｉで平板１２表面側から入射する平行太陽光Ｌ１を、最小偏角θｄで屈折させるように設定されている。これにより色収差を最小にできるから、発電波長領域の異なる多数のＰＮ接合素子を直列に接合した多接合型太陽電池を使用した場合に、広い波長域（０．４５μｍ〜１．７μｍ）の太陽光を上記太陽電池に入射させて効率的な発電を行なうことができる。
【０００４】
【特許文献１】
特開２００１−３６１２０
【０００５】
【発明が解決しようとする課題】
しかし、最小偏角θｄで屈折させるように突条１１の略三角プリズム断面を設定した上記平板フレネルレンズ１では、図５に示す二次集光器２の入光端面２ａ近くに位置するレンズ焦点領域において、光線高の低い領域（レンズ内周部）の突条１１から至った光Ｌ２１の焦点位置Ｆ１が、光線高の高い領域（レンズ外周部）の突条１１から至った光Ｌ２２の焦点位置Ｆ２よりも上記端面２ａに近くなる。すなわちレンズ内周部の突条１１の焦点距離がレンズ外周部の突条の焦点距離よりも長くなる。これは、遮光部の発生による光学効率（透過率）の低下を最小限にするために、レンズ内周部では通常、三角プリズムの頂角θｔを極力小さくしているからである。この結果、レンズ内周部の突条１１で屈折させられた光Ｌ２１は、レンズ外周部の突条１１で屈折させられた光Ｌ２２に比して、二次集光器２の入光端面２ａに入射する角度θが小さくなって二次集光器２内部での反射が充分になされず、このために、太陽電池受光面への太陽光の入射が不均一になってムラを生じることがあった。
【０００６】
そこで、本発明はこのような課題を解決するもので、平板フレネルレンズと二次集光器を組み合わせた集光式太陽光発電装置において、太陽電池の受光面への太陽光の入射ムラを小さく抑えることができる集光式太陽光発電装置を提供する事を目的とする。
【０００７】
【課題を解決するための手段】
上記目的を達成するために、本発明では、太陽光（Ｌ１）を集光するフレネルレンズ（１）と、フレネルレンズ（１）により集光された光（Ｌ２）を入射させて内部反射を繰り返させつつ導光する二次集光器（２）と、二次集光器（２）より出力された光が入射する太陽電池（３）とを備える集光式太陽光発電装置において、平板（１２）の表面側に略三角プリズム断面の同心円環状の突条（１１）を多数形成して上記フレネルレンズ（１）とするとともに、レンズ内周部の突条（１１）から至った光（Ｌ２１）の焦点位置（Ｆ１）が、レンズ外周部の突条（１１）から至った光（Ｌ２２）の焦点位置（Ｆ２）よりも二次集光器（２）の入光端面（２ａ）から遠くなるようにこれら突条（１１）の断面形状を設定する。この場合の突条の断面形状の設定は、例えば上記突条の略三角プリズム断面の頂角を適当な角度に設定することにより行う。
【０００８】
本発明においては、平板フレネルレンズにおけるレンズ内周部の突条から至った光の焦点位置が、レンズ外周部の突条から至った光の焦点位置よりも二次集光器の入光端面から遠くなるように、すなわちレンズ内周部の突条の焦点距離がレンズ外周部の突条の焦点距離よりも短くしてあるから、レンズ内周部の突条で屈折させられた光の、二次集光器の入光端面に入射する角度は大きくなり、二次集光器内部での反射が充分になされるようになる。この結果、平板フレネルレンズのレンズ内周部およびレンズ外周部のいずれから二次集光器の入光端面に入射する光も二次集光器内部での反射が充分になされ、太陽電池の受光面への太陽光の入射が均一になって照度ムラの発生が防止される。なお、内周部の突条について、入射する平行太陽光を最小偏角で屈折させる条件を外しても、当該内周部においては屈折角が小さいから色収差による光の広がりはそれ程大きくならない。また、レンズ内周部の面積はレンズの全面積に比して小さいから、二次集光器への光入射角を大きくするために三角プリズム頂角を大きくしても、これにより拡大する遮光部の面積はレンズ全面積から見ると依然小さいから、損失は小さく、照度ムラの改善の効果のほうが大きい。
【０００９】
なお、上記カッコ内の符号は、後述する実施形態に記載の具体的手段との対応関係を示すものである。
【００１０】
【発明の実施の形態】
本発明の集光式太陽光発電装置（以下、単に発電装置という）の構成の一例を図１に示す。図１において、発電装置には集光用の平板フレネルレンズ１が設けられており、その構造は既に従来技術の欄で説明したように、表面（上面）側に同心円環状の突条１１が多数形成され、各突条１１の断面形状は略三角プリズム断面となっている（図４参照）。平板フレネルレンズ１の下方には、後端（下端）に向けて小径となり４つのテーパ状側面２ｃを有する四角錐台形の二次集光器２が配設してあり、その後端面（出光端面）２ｂに接して四角形の基板を有する太陽電池３が設けてある。
【００１１】
平行太陽光Ｌ１が平板フレネルレンズ１に入射すると、収束する円形光束Ｌ２となって二次集光器２に向けて射出され、二次集光器２の前端面（入光端面）２ａ近くで一旦集光させられた後（図２）、ほぼ入光端面（例えば１１ｍｍ角）２ａいっぱいに拡散してこれに入射する。二次集光器２の入光端面２ａに入射した円形光束Ｌ２はテーパ状の４つの側面２ｃで全反射させられつつ出光端面２ｂへ向かい、これに接して設けられた太陽電池３の受光面（例えば７ｍｍ角）に入射する。二次集光器２内には、万華鏡的に多数の太陽電池虚像が形成されており、二次集光器２内に入射した光はその側面２ｃで多様な方向へ反射を繰り返して各虚像方向へ向う結果、太陽電池３の受光面に万遍なく入射する。
【００１２】
ここで、本実施形態では、平板フレネルレンズ１の内周部の突条１１について、その略三角プリズム断面の頂角θｔ（図４）を、入射する平行太陽光Ｌ１を最小偏角θｄで屈折させる条件を満たす角度よりも大きく設定してある。これにより、平板フレネルレンズ１によって集光させられる太陽光Ｌ１は、その焦点領域Ａの拡大図である図３に示すように、レンズ内周部の突条１１から至った光Ｌ２１の焦点位置Ｆ１が、レンズ外周部の突条１１から至った太陽光Ｌ２２の焦点位置Ｆ２よりも二次集光器２の入光端面２ａから遠くなる。すなわちレンズ内周部の突条１１の焦点距離がレンズ外周部の突条１１の焦点距離よりも短くなる。
【００１３】
この結果、レンズ内周部の突条１１で屈折させられた光Ｌ２１の、二次集光器２の入光端面２ａに入射する角度θが従来よりも大きくなり、上述した二次集光器２内部での反射が充分になされるようになる。これにより、平板フレネルレンズ１のレンズ内周部およびレンズ外周部のいずれから二次集光器２の入光端面２ａに入射する光Ｌ２１，Ｌ２２も二次集光器２内部での反射が充分になされ、太陽電池３の受光面への太陽光の入射が均一になってムラの発生が防止される。なお、内周部の突条１１について、上述のように、入射する平行太陽光Ｌ１を最小偏角θｄで屈折させる条件を外しても、当該内周部においては屈折角が小さいから色収差による光の広がりはそれ程大きくなく、光波長による太陽電池への入射光の照度ムラが生じることはない。
【００１４】
上記実施形態では、平板フレネルレンズの、外周部の突条の焦点距離に対して内周部の突条の焦点距離を短くした例について説明したが、内周部をさらに内外複数の環状部に区画して、これら各環状部の突条の焦点距離を外周部の突条の焦点距離に対して順次短くなるように設定しても良い。
【００１５】
【発明の効果】
以上のように、本発明によれば、平板フレネルレンズと二次集光器を組み合わせた集光式太陽光発電装置において、太陽電池の受光面への太陽光の入射ムラを小さく抑えることができる。
【図面の簡単な説明】
【図１】本発明の一実施形態における、集光式太陽光発電装置の構成を示す斜視図である。
【図２】集光式太陽光発電装置の光路図である。
【図３】光路中の集光領域の拡大図で、図２のＡ部拡大図である。
【図４】平板フレネルレンズの部分拡大断面図である。
【図５】従来の集光式太陽光発電装置における、光路中の集光領域の拡大図である。
【符号の説明】
１…平板フレネルレンズ、１１…突条、１２…平板、２…二次集光器、３…太陽電池、Ｌ１…太陽光、Ｌ２…集光された光。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a concentrating solar power generation device that condenses sunlight onto a solar cell surface by a condensing lens, and in particular, the illuminance of the solar cell surface without being affected by tracking errors or lens assembly errors. The present invention relates to a concentrating solar power generation apparatus that can maintain power uniformly and perform stable power generation.
[0002]
[Prior art]
A concentrating solar power generation device always efficiently generates power by concentrating sunlight on a relatively small-diameter solar cell surface with a condensing lens directed toward the sun. Fresnel lenses are often used as condenser lenses. In such a concentrating solar power generation device, if the orientation of the condensing lens slightly deviates from the solar direction due to tracking error, Fresnel lens assembly error, etc., the illuminance on the light-receiving surface of the solar cell rapidly decreases. Power generation is greatly impaired. Therefore, conventionally, a secondary condenser is provided between the condenser lens and the solar cell so that the light beam emitted from the condenser lens is reflected inside the secondary condenser even if the light beam is slightly deviated from the normal direction. This ensures that the light flux is always incident on the light receiving surface of the solar cell (Patent Document 1).
[0003]
On the other hand, as the Fresnel lens, a flat Fresnel lens is frequently used because of easy manufacturing and maintenance. An example of the flat Fresnel lens 1 is shown in FIG. In FIG. 4, a large number of concentric annular ridges 11 having a substantially triangular prism cross section are formed on the surface side of the flat plate 12, and the apex angle θt of the triangular prism of each ridge 11 is usually perpendicular to the flat plate 12 surface. The parallel sunlight L1 incident from the surface side of the flat plate 12 at the incident angle θi with respect to the prism inclined surface is set to be refracted at the minimum deviation angle θd. Since chromatic aberration can be minimized by this, when a multi-junction solar cell in which a large number of PN junction elements having different power generation wavelength regions are joined in series is used, sunlight in a wide wavelength region (0.45 μm to 1.7 μm) is used. Can be efficiently incident on the solar cell.
[0004]
[Patent Document 1]
JP 2001-36120 A
[0005]
[Problems to be solved by the invention]
However, in the flat Fresnel lens 1 in which the substantially triangular prism section of the ridge 11 is set so as to be refracted at the minimum deflection angle θd, the lens focal point located near the light incident end face 2a of the secondary condenser 2 shown in FIG. In the region, the focal position F1 of the light L21 reaching from the ridge 11 in the low light ray region (lens inner periphery) is the focal point of the light L22 reaching the ridge 11 in the high light ray region (lens outer periphery). It is closer to the end face 2a than the position F2. That is, the focal length of the protrusion 11 on the inner peripheral portion of the lens is longer than the focal length of the protrusion on the outer peripheral portion of the lens. This is because the apex angle θt of the triangular prism is usually made as small as possible at the inner peripheral portion of the lens in order to minimize the decrease in optical efficiency (transmittance) due to the occurrence of the light shielding portion. As a result, the light L21 refracted by the protrusion 11 on the inner peripheral portion of the lens is compared with the light L22 refracted by the protrusion 11 on the outer peripheral portion of the lens, and the light incident end face 2a of the secondary condenser 2. The incident angle θ becomes smaller and the reflection inside the secondary concentrator 2 is not sufficiently performed. For this reason, the incidence of sunlight on the light-receiving surface of the solar cell becomes uneven and unevenness may occur. there were.
[0006]
Therefore, the present invention solves such a problem, and in a concentrating solar power generation device that combines a flat Fresnel lens and a secondary concentrator, the incidence unevenness of sunlight on the light receiving surface of the solar cell is reduced. It aims at providing the concentrating solar power generation device which can be suppressed.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, Fresnel lens (1) that condenses sunlight (L1) and light (L2) collected by Fresnel lens (1) are incident to repeat internal reflection. In a concentrating solar power generation apparatus including a secondary concentrator (2) that guides light while the light is output from the secondary concentrator (2), a flat plate ( A large number of concentric annular ridges (11) having a substantially triangular prism cross section are formed on the surface side of 12) to form the Fresnel lens (1), and the light (L21) from the ridge (11) on the inner periphery of the lens. ) Is farther from the light incident end face (2a) of the secondary condenser (2) than the focal position (F2) of the light (L22) reaching the ridge (11) on the outer periphery of the lens. The cross-sectional shape of these protrusions (11) is set so that it may become . In this case, the setting of the cross-sectional shape of the ridge is performed, for example, by setting the apex angle of the substantially triangular prism section of the ridge to an appropriate angle.
[0008]
In the present invention, the focal position of the light reaching the protrusion on the inner peripheral portion of the lens in the flat plate Fresnel lens is more from the light incident end face of the secondary condenser than the focal position of the light reaching the protrusion on the outer peripheral portion of the lens. Since the focal length of the protrusion on the inner periphery of the lens is shorter than the focal distance of the protrusion on the outer periphery of the lens, the light refracted by the protrusion on the inner periphery of the lens The angle of incidence on the light incident end face of the secondary condenser is increased, and reflection within the secondary condenser is sufficiently performed. As a result, the light incident on the light incident end face of the secondary condenser from either the lens inner peripheral part or the lens outer peripheral part of the flat Fresnel lens is sufficiently reflected inside the secondary condenser, and is received by the solar cell. The incidence of sunlight on the surface is uniform, and uneven illumination is prevented. In addition, even if it remove | excludes the conditions which refract the incident parallel sunlight with the minimum deflection angle about the protrusion of an inner peripheral part, since the refraction angle is small in the said inner peripheral part, the breadth of light by a chromatic aberration does not become so large. In addition, since the area of the inner periphery of the lens is smaller than the total area of the lens, even if the apex angle of the triangular prism is increased to increase the light incident angle to the secondary condenser, the light shielding is increased thereby. Since the area of the portion is still small when viewed from the total area of the lens, the loss is small and the effect of improving the illuminance unevenness is greater.
[0009]
In addition, the code | symbol in the said parenthesis shows the correspondence with the specific means as described in embodiment mentioned later.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
An example of the configuration of a concentrating solar power generation device (hereinafter simply referred to as a power generation device) of the present invention is shown in FIG. In FIG. 1, the power generating apparatus is provided with a concentrating flat plate Fresnel lens 1, and the structure thereof has many concentric annular ridges 11 on the surface (upper surface) side as already described in the section of the prior art. The cross-sectional shape of each protrusion 11 formed is a substantially triangular prism cross section (see FIG. 4). Below the flat Fresnel lens 1, a quadrangular pyramid-shaped secondary concentrator 2 having a small diameter toward the rear end (lower end) and having four tapered side surfaces 2c is disposed, and its rear end surface (light emission end surface). A solar cell 3 having a square substrate in contact with 2b is provided.
[0011]
When the parallel sunlight L1 enters the flat Fresnel lens 1, it converges into a circular light beam L2 and is emitted toward the secondary condenser 2, and near the front end face (light incident end face) 2a of the secondary condenser 2. After being condensed (FIG. 2), the light is diffused to the light incident end face (for example, 11 mm square) 2a and enters this. The circular light beam L2 incident on the light incident end surface 2a of the secondary condenser 2 is directed to the light output end surface 2b while being totally reflected by the four tapered side surfaces 2c, and the light receiving surface of the solar cell 3 provided in contact therewith. Incident (for example, 7 mm square). A large number of kaleidoscopic virtual images of solar cells are formed in the secondary concentrator 2, and light incident on the secondary concentrator 2 is repeatedly reflected in various directions on the side surface 2 c to each virtual image. As a result, the incident light uniformly enters the light receiving surface of the solar cell 3.
[0012]
Here, in this embodiment, with respect to the ridge 11 on the inner peripheral portion of the flat Fresnel lens 1, the apex angle θt (FIG. 4) of the substantially triangular prism section is refracted, and the incident parallel sunlight L1 is refracted with the minimum deviation angle θd. It is set larger than the angle that satisfies the condition to be satisfied. Thereby, the sunlight L1 collected by the flat Fresnel lens 1 is a focal position F1 of the light L21 that has reached the ridge 11 on the inner periphery of the lens, as shown in FIG. However, it is farther from the light incident end face 2a of the secondary condenser 2 than the focal position F2 of the sunlight L22 that reaches the protrusion 11 on the outer periphery of the lens. That is, the focal length of the protrusion 11 on the inner periphery of the lens is shorter than the focal length of the protrusion 11 on the outer periphery of the lens.
[0013]
As a result, the angle θ at which the light L21 refracted by the protrusion 11 on the inner periphery of the lens is incident on the light incident end surface 2a of the secondary condenser 2 becomes larger than before, and the secondary condenser described above. 2 is sufficiently reflected inside. As a result, the light L21 and L22 incident on the light incident end surface 2a of the secondary condenser 2 from either the lens inner peripheral part or the lens outer peripheral part of the flat Fresnel lens 1 is also sufficiently reflected inside the secondary condenser 2. As a result, the incidence of sunlight on the light receiving surface of the solar cell 3 becomes uniform and the occurrence of unevenness is prevented. As described above, even if the condition for refracting the incident parallel sunlight L1 at the minimum deviation angle θd is removed, the inner peripheral portion has a small refraction angle, and thus light caused by chromatic aberration. The spread of the light is not so large, and the illuminance unevenness of the incident light to the solar cell due to the light wavelength does not occur.
[0014]
In the above embodiment, the example in which the focal length of the protrusion on the inner peripheral portion is shortened with respect to the focal length of the protrusion on the outer peripheral portion of the flat plate Fresnel lens has been described, but the inner peripheral portion is further made into a plurality of inner and outer annular portions. It is also possible to divide and set the focal lengths of the ridges of each annular portion so as to be sequentially shorter than the focal lengths of the ridges of the outer peripheral portion.
[0015]
【The invention's effect】
As described above, according to the present invention, in a concentrating solar power generation device that combines a flat Fresnel lens and a secondary concentrator, it is possible to reduce the uneven incidence of sunlight on the light receiving surface of the solar cell. .
[Brief description of the drawings]
FIG. 1 is a perspective view showing a configuration of a concentrating solar power generation device according to an embodiment of the present invention.
FIG. 2 is an optical path diagram of the concentrating solar power generation device.
3 is an enlarged view of a condensing region in the optical path, and is an enlarged view of a part A in FIG.
FIG. 4 is a partially enlarged cross-sectional view of a flat Fresnel lens.
FIG. 5 is an enlarged view of a condensing region in an optical path in a conventional concentrating solar power generation device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Flat Fresnel lens, 11 ... Projection, 12 ... Flat plate, 2 ... Secondary concentrator, 3 ... Solar cell, L1 ... Sunlight, L2 ... Condensed light.

Claims

Output from the secondary concentrator, the secondary concentrator that guides the light collected by the Fresnel lens that collects the sunlight, the light that is collected by the Fresnel lens is incident , and the internal reflection is repeated on its side surface. In a concentrating solar power generation device including a solar cell on which light is incident, a large number of concentric annular ridges having a substantially triangular prism cross section are formed on the surface side of a flat plate to form the Fresnel lens, and the inner periphery of the lens The cross-sectional shape of these ridges is such that the focal position of light reaching the ridge is farther from the light incident end face of the secondary condenser than the focal position of light reaching the ridge on the outer periphery of the lens. A concentrating solar power generation device characterized by being set.