JP2002270885A - Light condensing solarlight power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light condensing solarlight power generator having a high efficiency by suppressing a decrease in an output due to a resistance loss or a chromatic aberration without reducing a photodetecting amount even without enhancing a tracking accuracy or an assembling accuracy. SOLUTION: Since a local light condensing density is enhanced in the vicinity of a pair of bus bars 42 as compared with that of another region on a photodetecting surface 38 of a solar battery cell 36 via a secondary condenser lens 34, a substantial photodetecting area of the cell 36, is enlarged, and the area utility ratio is enhanced. Hence, the photodetecting amount is assured without enhancing the tracking accuracy or the assembling accuracy. Further, since problems due to a distribution diode effect or an ohmic contact disturbance in association with a current concentration are eliminated, the substantial resistance of a pectinated electrode 40 is reduced, and further a condensing density near the bus bar 42 is enhanced, a photocurrent of each wavelength can approach to each other, and hence the photodetecting amount is not reduced even without enhancing the tracking accuracy or the assembling accuracy, the decrease in the output due to the resistance loss or the chromatic aberration is suppressed, and the efficiency of the solar light power generation is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generator having a high power generation efficiency.

[0002]

2. Description of the Related Art In order to increase the power generation efficiency of a photovoltaic power generation device provided with a photovoltaic cell for converting solar energy received on a light receiving surface into electric energy, condensed solar energy incident on the light receiving surface is increased. There is known a concentrating solar power generation device including a solar cell that converts light into electric energy.
For example, a concentrating solar power generation device (US Pat. No. 4,069,812) that condenses sunlight using a single Fresnel lens and makes it incident on a light receiving surface of a solar cell, a set of a prismatic cover and a wide electrode In addition, a concentrating solar power generation device (USP 4,711,9) in which the resistance loss of the comb-shaped electrode is improved.
72), a concentrating photovoltaic power generator with improved tracking accuracy by means of a secondary convex lens (US Pat. No. 5,167,72)
4), a concentrating photovoltaic power generator (USP) in which spectral mismatch due to chromatic aberration is improved using a color mixing prism
6,031,179).

[0003]

By the way, the above-mentioned conventional concentrator photovoltaic power generator still has various disadvantages. For example, in a concentrating photovoltaic power generation device that condenses sunlight using a single Fresnel lens and makes it incident on the light receiving surface of the photovoltaic cell, a slight shift of the photovoltaic cell increases as the condensing magnification increases. Since the amount of received light is affected, tracking accuracy when tracking the sun position and assembling accuracy of the condenser lens and the solar cell are required, and there is a disadvantage that the device becomes expensive. In a concentrator photovoltaic power generation system that improves the resistance loss of comb-shaped electrodes by combining a prismatic cover and a wide electrode, the prismatic cover improves the resistance loss, but high-precision alignment during assembly work Is necessary, the device becomes expensive, and when the current in the upper layer and the current in the lower layer do not match in a multi-junction solar cell in which cells (junctions) having different absorption wavelength bands are stacked, the value of the output becomes smaller. There is a disadvantage that loss due to chromatic aberration and tracking accuracy are not improved. Further, in the concentrator photovoltaic power generator in which the tracking accuracy is improved by the secondary convex lens, the chromatic aberration is rather deteriorated and the resistance loss is increased. Also, in a concentrator photovoltaic power generation system in which spectral mismatch due to chromatic aberration is improved by using a color mixing prism, transmission loss is increased because two prism structures are required, and resistance loss and tracking accuracy are not improved. There were drawbacks.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. It is an object of the present invention to reduce the amount of received light without increasing tracking accuracy and assembly accuracy, and to reduce resistance loss and chromatic aberration. It is an object of the present invention to provide a high-efficiency concentrating solar power generation device in which a decrease in output due to the light is suppressed.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the gist of the present invention is to provide a condensing type solar cell in which sunlight condensed by a primary condensing device is incident on a light receiving surface of a solar cell. A photovoltaic device, wherein (a) a plurality of relatively thin comb-shaped electrodes arranged at predetermined intervals, and the plurality of comb-shaped electrodes are connected to collect generated current generated in the comb-shaped electrodes. A solar cell in which a bus bar is provided on a light receiving surface, and (b) a secondary light condensing that condenses light at a higher density on an area closer to the bus bar on the light receiving surface of the solar cell than on other areas. And a lens.

[0006]

In this way, the sunlight condensed on the light receiving surface of the photovoltaic cell by the primary light condensing device is transferred to another area of the light receiving surface closer to the bus bar by the secondary light condensing lens. Light is collected at a higher density than the area. Thereby, first, light deviating from the light receiving surface of the solar cell is made incident on the light receiving surface by the secondary condenser lens, and the target area viewed from the primary condenser device is enlarged. Since the effective light receiving area is increased and the area utilization rate is increased, the amount of received light is secured without increasing the tracking accuracy and the assembly accuracy, and the efficiency of photovoltaic power generation is improved. In addition, sunlight is collected by the secondary condensing lens in the area near the bus bar on the light-receiving surface of the photovoltaic cell at a higher density than in other areas. Since the problem caused by the disturbance is eliminated and the resistance of the comb electrode is substantially reduced, the efficiency of photovoltaic power generation is improved. In addition, the secondary condensing lens functions as a concave lens in the central portion of the light receiving surface that is particularly affected by chromatic aberration, that is, in the middle portion of the bus bar, so that the condensing density at the central portion is low and the condensing density near the bus bar is increased. In addition, the photocurrent of each wavelength can be brought close to each other, and the light output can be increased. Furthermore, the light irregularly reflected by the comb-shaped electrode provided on the light-receiving surface of the solar cell is confined in the secondary condensing lens and made incident again on the light-receiving surface of the solar cell, so that the shade of the comb-shaped electrode Loss is reduced and the efficiency of solar power generation is increased.

[0007]

In another preferred embodiment of the present invention, preferably, the solar cell comprises a pair of bus bars parallel to each other, and connecting the pair of bus bars at right angles to the pair of bus bars. A plurality of comb-shaped electrodes arranged at regular intervals in the longitudinal direction of the pair of bus bars; and a plurality of comb-shaped electrodes provided on the light receiving surface, wherein the secondary condensing lens is located immediately above the pair of bus bars. Has a pair of projections at a position shifted by a predetermined distance from the middle area of the pair of bus bars, and has a recess on the middle area of the pair of bus bars, and has a light receiving surface of the solar cell. This is a multimodal convex lens provided in a state of being superimposed on. With this configuration, since the multimodal convex lens is provided so as to overlap the light receiving surface of the solar cell, the comb-shaped electrode provided on the light receiving surface of the solar cell can be protected and sealed. In addition, electrode corrosion and deliquescence deterioration of the antireflection film are prevented. Further, since the focal length of the multimodal convex lens is extremely shortened, there is an advantage that the solar cell module has a flat shape.

[0008] Preferably, the solar cell is a multi-junction solar cell in which a plurality of types of pn junctions having different absorption wavelength bands are stacked. In such a multi-junction solar cell, the difference in photocurrent between the pn junctions having different absorption wavelength bands provided in a stacked manner in the thickness direction is reduced, so that the output reduction due to the chromatic aberration can be suitably reduced. .

[0009]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, a solar tracking device 10 includes a concentrating solar power generation device 12 according to an embodiment of the present invention and the concentrating solar power generation device 12 around a vertical axis and a horizontal axis. Rotatably supported and its concentrating solar power generation device 12
Has a vertical axis driving device 14 and a horizontal axis driving device 16 that are driven to rotate around the vertical axis and the horizontal axis so that the solar cell is maintained in a posture facing the sun. The position of the sun is tracked so that it can always face the sun. Vertical axis drive 1
Reference numeral 4 denotes a vertical output shaft 18 protruding upward and rotatable around a vertical axis, and a U fixed to the output shaft 18 for supporting the concentrating solar power generation device 12 rotatably around a horizontal axis. And a U-shaped arm 20. The horizontal axis driving device 16 is provided at one end of the U-shaped arm 20 and supports the concentrating solar power generation device 12.
2 is provided with an output shaft 24 described below, which is connected directly or indirectly via a simple reduction gear.

As shown in FIG. 2, the concentrator photovoltaic power generation device 12 has a fan-shaped cross section and an opening on the side of a partial cylindrical surface, and a case 30 for functioning as a primary concentrator. And a non-imaging Fresnel lens 32 of a partial cylindrical shape fitted in the opening of
2, a secondary condensing lens 34 and a semiconductor solar cell 36 arranged in a state of being superimposed on the bottom surface of the case 30 at the light condensing position of the case 2, and as shown by a dashed line in FIG. When the sunlight L is condensed on the battery cell 36 through the secondary condenser lens 34, the power generated from the solar cell 36 is output. In the concentrator photovoltaic power generation device 12, the non-imaging Fresnel lens 32 is used so that, as shown in FIG. The intensity of light condensed on the solar cell 36 by the image system Fresnel lens 32 can be made constant.

The solar cell 36 has a long plate shape, for example, as shown in FIG. The solar cell 36
The light receiving surface 38 has a plurality of relatively thin comb-shaped electrodes 40 arranged in parallel in the short side direction (width direction, that is, the y direction) at regular intervals in the longitudinal direction, and the longitudinal direction of the light receiving surface 38. A relatively thick pair of busbars (collecting electrodes) 42 provided in a state connected to the comb-shaped electrode 40 at the side edge in the (x direction), that is, the side edge along the long side, is, for example, a conductive adhesive. It is formed of an agent or a conductive thick film material. The comb electrodes 40 are arranged on the light receiving surface 38 so as to have the same density.

The solar battery cell 36 has a multi-junction structure in which a plurality of types of pn junctions having different absorption wavelength bands are stacked, as shown in FIG. 4, for example. In the embodiment of FIG. 4, the dimensional ratios and the like of the respective parts are not necessarily drawn accurately. In FIG. 4, the solar cell 36 is
The upper part of the p-type germanium plate is n
A bottom junction layer 46 in which a pn junction is formed by forming a mold, an n ⁺ -GaAs layer of about 0.1 μm and an n ⁺
-(In) GaAs As layer, and the Ge
A buffer layer 48 stacked on the substrate 46, n ⁺⁺ -In
A tunnel layer 50 composed of a GaP layer and a p ^++- AlGaAs layer sequentially and stacked on the buffer layer 48
And p ⁺ -InGaP layer, p- (In) GaAs layer, n
An intermediate junction layer 52 having a pn junction formed by sequentially forming a ⁺ -(In) GaAs layer and an n ⁺ -AlInP layer; an n ⁺⁺ -InGaAs layer and a p ⁺⁺ -AlGa layer;
A tunnel layer 54, a p-AlInP layer, and a p-I
An upper junction layer 56 having a pn junction formed by sequentially forming an nGaP layer, an n ⁺ -InGaP layer, and an n ⁺ -AlGaP layer. In FIG. 4 described above, a back electrode 58 is fixed to the bottom surface of the solar cell 36, and generated power is output between the back electrode 58 and the comb-shaped electrode 40 on the light receiving surface 38. . A contact layer 60 made of, for example, n-AlInP is provided between the comb electrode 40 and the n ⁺ -AlGaP layer of the upper bonding layer 56.
Is provided, and an antireflection film 62 is provided on the exposed surface of the n ⁺ -AlGaP layer. In FIG. 4, substances shown in [] are impurities diffused or ion-implanted for setting a semiconductor type.

The bottom bonding layer 46, the intermediate bonding layer 52,
And the pn junctions provided in the upper junction layer 56 are electrically connected in series, and have absorption bands different from each other in the center wavelength, as shown in FIG. High conversion efficiency can be obtained by making the absorption wavelength band of the wavelength band a wide band.

FIG. 6 shows a solar cell module in which the secondary condensing lens 34 is closely stacked on the solar cell 36 constructed as described above. The secondary condensing lens 34 is made of a transparent material such as glass or acrylic resin having a refractive index sufficiently larger than 1. For example, as shown in FIG.
A multimodal convex lens having a pair of convex portions 66 at a position shifted by a predetermined distance to the intermediate region side of the pair of bus bars 42 and having a concave portion 68 on the intermediate region of the pair of bus bars 42. For this reason, as shown by the sunlight L indicated by a dashed line in FIG.
The light is condensed on a region closer to the pair of bus bars 42 at a higher density than other regions.

As described above, according to the present embodiment, the vicinity of the pair of bus bars 42 on the light receiving surface 38 of the photovoltaic cell 36 is more locally collected by the secondary condensing lens 34 than in other regions. Since the light density is increased, the following various functions can be obtained. First, (a) light deviating from the light receiving surface 38 of the solar cell 36 is made incident on the light receiving surface 38 by the secondary condensing lens 34, and the non-imaging Fresnel lens 3
Since the target area, that is, the light receiving surface 38 as viewed from the side of the primary light condensing device, that is, the light receiving surface 38 is enlarged, the substantial light receiving area of the solar cell 36 is enlarged, and the area utilization factor is increased. For example, 0.5m
The secondary condenser lens 34 can be assembled with a tolerance of about m, the amount of received light is secured without increasing the tracking accuracy or the assembly accuracy, and the efficiency of photovoltaic power generation is improved.

Next, (b) the sunlight L is applied to the secondary condenser lens 3
4, since the light can be collected on the solar cell 36 without extremely increasing the light collection magnification at the center, the distributed diode effect and the ohmic contact disturbance caused by the extreme light collection are suppressed. Efficiency is increased. The distributed diode effect means that as the distance from the comb-shaped electrode 40 increases, the path through which the generated current flows to the comb-shaped electrode 40 increases and the voltage increases. This is a phenomenon of internal conduction and was discovered by the present inventors. The ohmic contact disturbance is a phenomenon in which, when the degree of light collection increases, the thickness of a barrier at the interface between a metal and a semiconductor increases due to injected electrons or holes, and contact resistance sharply increases.

(C) In the central portion of the light receiving surface 38 where the influence of chromatic aberration is particularly large, that is, at the intermediate portion between the pair of bus bars 42, the secondary focusing lens 34 functions as a concave lens and the focusing density at the central portion 7, the light-collecting density near the bus bar 42 is increased, and the conventional light-collecting intensity (incident intensity) is dispersed, as shown in FIG. 7, for example. Increased. That is, the solar cell 36 is a multi-junction solar cell in which a plurality of types of pn junctions having different absorption wavelength bands are stacked, and among the pn junctions having different absorption wavelength bands provided in the thickness direction. Has the property of being limited by the weakest output of the lens, and when the secondary condenser lens 34 is not used,
For example, as shown in FIG. 8, at the center in the width direction of the light receiving surface 38, the light output (absorbed energy intensity) of the pn junction of the bottom bonding layer 46 is low, and the light output (absorbed energy intensity) of the pn junction of the upper bonding layer 56 is low. ) Is high and the difference is large, but the difference in the light current between the secondary light condensing lenses 34 (the light condensing density at the center in the width direction of the light receiving surface 38 is reduced) causes the difference in the mutual photocurrent. Since the chromatic aberration is reduced, there is an advantage that the output reduction is appropriately reduced by the chromatic aberration.

(D) Light-receiving surface 3 of solar cell 36
8, the light irregularly reflected by the comb-shaped electrode 40 is confined in the secondary condensing lens 34 and made incident on the light-receiving surface 38 of the solar cell 36 again.
The shade loss is reduced and the efficiency of solar power generation is increased.

According to the present embodiment, the solar cell 3
Reference numeral 6 denotes a pair of bus bars 42 parallel to each other, and connects the pair of bus bars 42 at right angles to the pair of bus bars 42, and at a predetermined interval in the longitudinal direction of the pair of bus bars 42. And a plurality of comb-shaped electrodes 40 arranged on the light receiving surface 38.
The pair of bus bars 42 is located immediately above the pair of bus bars 42.
Has a pair of projections 66 at a position shifted by a predetermined distance to the intermediate region side, and has a concave portion 68 on the intermediate region of the pair of bus bars 42 so as to overlap the light receiving surface 38 of the solar cell 36. Since the multi-modal convex lens is provided in a state where the comb-shaped electrode 40 provided on the light-receiving surface 38 of the solar cell 36 can be protected and appropriately sealed, the comb-shaped electrode 40 and the bus bar Corrosion of electrodes such as 42 and deliquescence deterioration of the antireflection film 62 are prevented. In addition, since the focal length of the secondary condensing lens (multimodal convex lens) 34 is extremely short, there is an advantage that the solar cell module (the secondary condensing lens 34 and the solar cell 36) has a flat shape.

While the embodiment of the present invention has been described in detail with reference to the drawings, the present invention can be embodied in still another embodiment.

For example, in the above-described embodiment, as shown in FIG. 3, for example, the solar cell 36 is provided with a pair of bus bars 42 at the side edges in the longitudinal direction, and the connection between the pair of bus bars 42 is provided. Although a large number of comb-shaped electrodes 40 are arranged in parallel with each other at regular intervals in the longitudinal direction as described above, for example, as shown in FIG.
A plurality of pairs of bus bars 42 connected to each other by 0 may be provided on the light receiving surface 38, or, for example, as shown in FIG. 10, the bus bars 42 are provided along four sides of the light receiving surface 38, A large number of comb-shaped electrodes 40 have their light receiving surfaces 3
8 may be arranged at equal density and connected to the bus bar 42.

In the case of the solar cell 36 shown in FIG. 9, a plurality of secondary condenser lenses 34 are connected to a pair of bus bars 42.
It is arranged so as to cover between them. Alternatively, a secondary condenser lens integrally molded to have a similar shape is used.
In the case of the solar cell 36 shown in FIG.
A secondary condensing lens is used in which the convex portions 66 are connected along the four sides of the light receiving surface 38, and the concave portions 68 are provided between the convex portions 66.

In the above-described embodiment, the non-imaging system Fresnel lens 32 is provided as the primary condensing device.
Other primary light collecting devices such as a cylindrical reflecting mirror and a spherical reflecting mirror may be used. In such a case, in the solar cell module in which the secondary condensing lens 34 is superimposed on the solar cell 36, the light receiving surface 38 may not necessarily be at a right angle to the sunlight L. Inclined to L,
It may be parallel to sunlight L. Further, the light receiving surface 38 need not necessarily be a flat surface.

Although not specifically exemplified, the present invention
Various changes can be made without departing from the spirit of the invention.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration example of a solar tracking device including a concentrating solar power generation device of the present invention.

FIG. 2 is a sectional view schematically illustrating the configuration of the concentrator photovoltaic power generator of FIG.

FIG. 3 is a perspective view showing a solar cell provided in the concentrator photovoltaic power generator of FIG.

FIG. 4 is a diagram illustrating a multi-junction structure of the solar cell of FIG.

5 is a diagram illustrating wavelength characteristics (absorption sensitivity characteristics) of the efficiency of the solar cell having the multi-junction structure of FIG. 3;

6 is a diagram showing a configuration of a solar cell module provided in the concentrating solar power generation device of FIG. 2, and is a diagram illustrating a shape of a secondary condensing lens.

FIG. 7 is a diagram for explaining light-collecting intensity characteristics of the secondary light-converging lens of FIG. 6 in comparison with conventional light-collecting intensity characteristics.

FIG. 8 is a diagram showing a comparison between a pn junction photocurrent of a bottom junction layer and a photocurrent of an upper junction layer in a solar cell having the multi-junction structure shown in FIG.

FIG. 9 is a perspective view showing a shape of a solar cell according to another embodiment of the present invention, and is a view corresponding to FIG.

FIG. 10 is a perspective view showing a shape of a solar battery cell according to another embodiment of the present invention, and is a view corresponding to FIG.

[Explanation of symbols]

 12: Concentrating solar power generation device 32: Non-imaging system Fresnel lens (primary focusing lens) 34: Secondary focusing lens 36: Solar cell 40: Comb electrode 42: Bus bar (collecting electrode) 66: Convex part 68: concave part

Claims (3)

[Claims] 1. A concentrating photovoltaic power generation device for causing sunlight condensed by a primary condensing device to enter a light receiving surface of a solar cell, comprising a plurality of relatively thin combs arranged at predetermined intervals. Electrodes and
A solar cell provided on a light receiving surface thereof with a bus bar to which the plurality of comb electrodes are connected to collect the generated current generated in the comb electrode; and a bus bar among the light receiving surfaces of the solar cells. And a secondary condensing lens that condenses light at a higher density than other regions in a region closer to the photovoltaic device. 2. The solar battery cell comprises: a pair of bus bars parallel to each other; connecting the pair of bus bars at a right angle to the pair of bus bars, in a longitudinal direction of the pair of bus bars. A plurality of comb-shaped electrodes disposed at regular intervals on the light-receiving surface, wherein the secondary condensing lens is disposed in a middle area of the pair of bus bars from directly above the pair of bus bars. A pair of convex portions provided at positions shifted by a predetermined distance to the side and a concave portion on an intermediate region of the pair of bus bars, and provided in a state of being superposed on the light receiving surface of the solar cell. The concentrator photovoltaic power generator according to claim 1, which is a peak convex lens. 3. The concentrator photovoltaic power generation device according to claim 1, wherein the solar cell is a multi-junction solar cell in which a plurality of types of pn junctions having different absorption wavelength bands are stacked.