JPH05190884A - Covering material for solar battery - Google Patents

Abstract

PURPOSE:To enable directivity of an incidence efficiency to be generated and eliminate a need for an additional mechanism for adjusting an installation angle between an installation-type solar battery and a foundation by forming an inclination surface which is asymmetrical left and right or front and back at a proper spacing on the surface of a translucent plate-like or film-like covering material for covering the surface of the solar battery. CONSTITUTION:A covering material 10 for a solar battery 20 consists of a colorless and transparent glass or a translucent substance such as acryl resin, and the surface side has a wave shape and at the same time the rear side has a flat face. In the surface of the wave shape, a vertical surface 11 which is extended in the normal direction which is erected on the surface of the solar battery 20 and an inclination surface 12 which is extended in a direction which is at an angle of theta for the surface of the solar battery are repeated at a specified pitch. The pitch of the vertical surface 11 is set to a value which is two times larger than that of the surface electrode layer of the solar battery and at the same time each vertical surface is laid out directly above the surface electrode layer. Also, a flat rear surface of the film body 10 is joined to the surface of the solar battery 20 by an adhesive layer 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell covering mounted on a solar car or the like.

[0002]

2. Description of the Related Art The surface of a solar cell mounted on a solar car or installed on a roof of a house is usually a translucent plate or film for mechanically protecting the surface. The covering body is attached. A typical coating of this type has a flat surface. Further, for the purpose of increasing the incident efficiency to the light-receiving surface by directing the incident light beam that passes through this type of coating toward the surface electrode layer of the solar cell toward the light-receiving surface away from this surface electrode layer based on the lens effect,
The technical idea of forming a bilaterally symmetrical corrugated inclined surface on the surface of the covering is disclosed in Japanese Patent Laid-Open No. 63-102279.

[0003]

SUMMARY OF THE INVENTION The conventional coating body described above is
Since the surface is a flat surface or has a corrugated shape that is symmetrical in the left-right direction (or front-rear direction), it has a light-receiving characteristic that is symmetrical in the left-right direction (or front-back direction) around the normal line set on the surface of the solar cell.
However, in a stationary solar cell that does not have a tracking function, the inclination of the base on which it is installed does not necessarily match the optimal orientation of the solar cell to maximize the amount of received light. There is a problem in that an additional mechanism for adjusting the installation angle is required between and, and the structure becomes complicated and the cost becomes high. In particular, when installing in a solar car or the like, there is a problem that the weight of the entire vehicle and air resistance increase with the addition of the installation angle adjusting mechanism.

[0004]

Means for Solving the Problems The left and right or front and rear asymmetrical inclined surfaces are formed on the surface of the solar cell coating body according to the present invention to form left and right or front and rear asymmetrical (directional).
Light receiving characteristics are realized.

[0005]

Function: A part of the sun rays incident on the cover enters the cover and the remaining part becomes reflected light. In the case of a flat plate-shaped coating with a flat surface, all reflected light leaves the coating, and the opportunity for entering the coating is completely lost. On the other hand, in the covering body having the corrugated surface, the optical path of the reflected light has an opportunity to intersect with the adjacent mountain, so that the opportunity to re-enter the covering body is given to a part thereof. A part of the reflected light that has the opportunity of re-incident enters the inside of the coating by this re-incident, and the remaining part becomes the re-reflected light. A part of the re-reflected light has an opportunity for its optical path to intersect with an adjacent mountain, so that the light is re-incident on the coating.

As described above, the incidence efficiency is determined by how many times the reflected light is allowed to be re-incident. From this point, the coating body having a corrugated surface has a higher incidence efficiency than the coating body having a flat surface.
Further, in the case of a cover having an asymmetrical corrugated surface, the path followed by the reflected light beam differs depending on the incident direction of the sun's rays, and the chance of re-incident light given to such reflected light beam also differs. As a result, the coating having a bilaterally asymmetrical wavy surface has a directivity in the incidence efficiency.

For example, as shown in FIG. 4, it is assumed that the covering body has a bilaterally asymmetrical corrugated surface. One inclined surface AB of this cover is a vertical surface extending in the direction of the normal line standing on the surface of the solar cell, and the other inclined surface BC adjacent to this is a complementary angle between the vertical surface AB and θ ( 90 ° -θ). The material of this cover is typically glass or acrylic resin, and its refractive index is about 1.5.

As shown in FIG. 4 (A), the path of the reflected light L ₁₁ of the sun ray L ₁₀ incident on the inclined surface BC from the left front side is away from this cover because it does not intersect the inclined surface AB. It completely misses the opportunity to enter into the cover. In addition, the path of the reflected light L ₂₁ of the sun ray L ₂₀ that is incident on the lower side of the inclined surface BC from the same direction intersects with the vertical surface AB, so that the opportunity to enter this cover is obtained again. However, the reflected light L that is reflected here and misses the opportunity to enter
_Since the route of ₂₂ does not intersect with the inclined surface BC, it becomes away from the covering body and completely misses the opportunity to enter the covering body.

On the other hand, as shown in FIG. 4B, the path of the reflected light L ₁₁ of the sun ray L ₁₀ incident on the vertical plane AB from the right front crosses the inclined plane BC, so that this coating is applied. Get another chance to enter the body. In addition, the path of the reflected light L ₁₂ that is reflected here and misses the opportunity to enter is again the vertical plane AB.
Because it intersects with, it gets another chance to enter this cladding. Here, the path of the reflected light L ₁₃ that has missed the opportunity to enter again crosses the inclined surface BC again, so that the opportunity to enter again is obtained. The reflected light L _{14 that} has missed the opportunity to enter on the inclined surface BC becomes one way away from the coating body and completely misses the opportunity to enter the coating body. That is, the sunlight ray L ₁₀ incident on the vertical plane AB from the right front is given four opportunities to approach until it completely misses the opportunity.

Further, since the path of the reflected light L ₂₁ of the sun ray L ₂₀ incident above the inclined surface BC in parallel with the sun ray L ₁₀ intersects the vertical plane AB, the opportunity to enter this cover is again obtained. To do. The path of the reflected light L ₂₂ that is reflected here and misses the opportunity to enter again intersects the vertical plane AB again, so that the opportunity to enter still remains. Below, because the illustration becomes complicated,
Although the optical path beyond that is omitted, a vertical plane AB is provided for the reflected light L _22.
There is still an opportunity to enter the slope BC.

As described above, in the case of FIG. 4, the sun rays entering the cover from the right front are given more opportunities to enter the cover than the sun rays entering from the left front. In addition, the absolute amount of reflected light decreases as the number of reflections increases. Therefore, the absolute amount of reflected light that is permanently moved away from this cover after repeating a large number of reflections is 1 or 2 times. Therefore, it is extremely small compared to the absolute amount of reflected light that is permanently distant from this cover. Therefore, in the case of FIG. 4, the incidence efficiency of the sun rays incident on the cover from the right front is increased as compared with that of the sun rays incident from the left front, and anisotropy of the incidence efficiency occurs.

[0012]

1 is a cross-sectional view showing the structure of a solar cell covering 10 according to an embodiment of the present invention together with a solar cell 20 to be covered. The solar cell 20 to be covered is a semiconductor substrate 21 such as AlGaAs in which a pn junction is formed at a predetermined depth from the surface, and is discretely formed at predetermined intervals on the surface of the semiconductor substrate 21 in a direction perpendicular to the paper surface. The strip-shaped front surface electrode layer groups 22a, 22b, 22c ... And the plate-shaped rear surface electrode layer 23 formed on the rear surface of the semiconductor substrate 21 are formed, and the front surface electrode layers 22a to 22e and the rear surface electrodes are formed. Photoelectromotive force generated between the layer 23 and the layer 23 is supplied to an electric circuit (not shown) in the subsequent stage.

The cover 10 is made of a transparent material such as colorless and transparent glass or acrylic resin, and has a corrugated shape on the front surface and a flat surface on the back surface. The corrugated surface has a predetermined vertical surface 11 extending in the direction of a normal line standing on the surface of the solar cell 20 and an inclined surface 12 extending in a direction forming an angle θ with the surface of the solar cell. It has been repeated on the pitch. In this embodiment, the vertical plane 1
The pitch of 1 is set to a value twice the pitch of the surface electrode layer of the solar cell (typically about 1 mm), and each vertical surface is arranged directly above the surface electrode layer. This cover 10
The flat back surface of is bonded to the front surface of the solar cell 20 by the adhesive layer 30.

FIG. 2 is a simulation result of confirming the directivity of the incident efficiency of the cover of FIG. 1 by the ray tracing method. In this simulation, the refractive index of the coating 10 is 1.5, and the outside of the coating 10 is air (refractive index 1.
0), the refractive index of the semiconductor substrate 20 is 3.5, and the adhesive layer 30
And the thickness of the surface electrode layers 22a, 22b, 22c ... Is zero, the surface electrode layer is a perfect reflection surface, and the percentage of that area to the total surface area of the semiconductor substrate 21 is 6.6%. The reflectance is Fresnel's formula. It is calculated according to.

The vertical axis of FIG. 2 represents the percentage (incident efficiency%) of the total amount of sunlight incident on the semiconductor substrate 21 with respect to the total amount of sunlight incident on the coating 10. The horizontal axis is
It is an angle φ (°) formed by a normal line standing on the surface of the solar cell 10 and an incident sun ray, and φ has a positive value when the sun ray enters from the right side in FIG. 1. This incidence efficiency is calculated while changing the incidence angle φ by 5 °. The parameter is θ in FIG. 1, and is 0 °, 45 °, 6
Three values of 0 ° are selected.

FIG. 3 is a conceptual diagram showing a part of the progress of the simulation shown in FIG. 2. The straight line with an arrow is the optical path, and the numbers displayed near the light beam indicate the transmitted light and the reflected light. The amount of light. Each light quantity is the absolute quantity of the original incident light quantity is 1
It is expressed by the absolute light amount when 00 is set. The absolute light amount of each light beam decreases while repeating transmission and reflection, but the light beam whose absolute light amount has decreased to 5 or less is omitted in order to avoid complication. Of the 100 light amounts that first entered the inclined surface, 87.7 light amounts were transmitted, and
A light amount of 2.3 is reflected. The transmitted light amount of 87.7 reaches the surface of the semiconductor substrate, of which 13.0 is reflected. That is, the absolute amount of light entering the semiconductor substrate is 74.7. Since it is assumed that this corrugated structure continues indefinitely, a light beam with an absolute light intensity of 13.0 going out from the left end of the figure to the outside of the figure has an absolute light intensity of 12.
It again appears in the figure from the left as a ray of light 5.

The following conclusions can be drawn from the simulation results of FIG. 1. By making the surface of the cover corrugated regardless of the incident direction of the sun rays, the incidence efficiency can be improved as compared with the cover having a flat surface. 2. By making the surface of the covering body asymmetrical, an asymmetrical (directive) incidence efficiency can be obtained according to the incident direction of the sunlight. 3. In the region where φ that tries to use directivity is positive, θ =
The 45 ° corrugation has a higher incidence efficiency than the θ = 60 ° corrugation. Note that in FIG. 2, in the case of a flat surface (θ = 0), the incident efficiency is naturally symmetric regardless of the incident direction. Therefore, by comparing this with the incident efficiency on the corrugated surface, , The asymmetry of the incident efficiency on the corrugated surface becomes obvious.

[0018]

As described above in detail, the coating of the solar cell according to the present invention has a structure in which the asymmetrical corrugations are formed on the surface in the left-right direction or the front-back direction to generate the directivity of the incident efficiency. Therefore, an additional mechanism for adjusting the installation angle between the stationary solar cell and the base is not required, and the structure can be simplified and inexpensive.

In particular, in the case of a solar cell mounted on a solar car, the addition of the installation angle adjusting mechanism effectively avoids the problems of increasing the weight and air resistance of the entire vehicle, and impairing the aesthetic appearance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a coating body according to an embodiment of the present invention together with a solar cell to be coated.

FIG. 2 is a characteristic diagram showing a simulation result of incidence efficiency obtained for the structure of FIG.

FIG. 3 is a characteristic diagram showing an example of paths of transmitted light rays and reflected light rays, which are intermediate results of the simulation of the incident efficiency obtained for the structure of FIG. 1, and their absolute light amounts.

FIG. 4 is a conceptual diagram for explaining the operation of the present invention.

[Explanation of symbols]

10 coating body 11 one inclined surface (vertical surface) formed on the surface of the coating body 10 other inclined surface formed on the surface of the coating body 20 solar cell 30 having coating symmetry 30 adhesive layer

Claims (2)

[Claims] 1. A translucent plate-shaped or film-shaped solar cell coating for covering the surface of a solar cell, wherein a left-right or front-back asymmetric inclined surface is provided at an appropriate interval on the surface side of the coating. A coated body of a solar cell, which is formed. 2. One of the left and right or front and rear asymmetrical inclined surfaces extends in a direction parallel to a normal line standing on the surface of the solar cell, and the other inclined surface has the one inclined surface. The solar cell coating body according to claim 1, wherein the coating body extends in a direction having an angle of about 45 ^° .