JP2013088690A - Light collecting device and photovoltaic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light collecting device which suppresses energy loss in light collection process to be able to more efficiently collect light energy of sunlight or the like.SOLUTION: A light collecting device includes: a light collecting member 10 including a prism-like light collecting part 10a which reflects, a plurality of times, light incident from a first surface 11 between a second surface 12 and the first surface 11 to collect the light; and a reflecting member 15 which has a reflecting surface 16 provided opposite to the second surface 12. The light collecting part 10a is configured so that light incident on the first surface 11 is transmitted through the second surface 12, is reflected by the reflecting surface 16, and makes incident again on the light collecting part 12 from the second surface 12, and then is totally reflected by the first surface 11. The light collecting part is configured so that its vertex angle α is approximately a minimum value in an angular range where the light having made incident again is totally reflected by the first surface 11.

Description

  The present invention relates to an apparatus for condensing light, and more specifically, includes a first surface on which received light is incident and a second surface that intersects the first surface at an acute angle. The present invention relates to a condensing device having a prism-like condensing unit that condenses light by reflecting a plurality of times with a first surface, and a photovoltaic device using such a condensing device.

  A condensing device having the prism-shaped condensing unit as described above is known as a condensing device that condenses sunlight, for example. A basic conceptual diagram of such a light collecting device 9 is shown in FIG. The condensing device 9 includes a first surface 91 on which sunlight is incident, a second surface 92 that intersects the first surface 91 at an apex angle α and returns incident light, and a third surface that intersects the first surface 91 at a substantially right angle. 93 and includes a light collecting member 90 having a light collecting portion 90a formed in a prismatic shape or a wedge shape in cross-sectional view. The photovoltaic device is configured such that a photoelectric conversion element (solar cell) that photoelectrically converts the collected light is provided on the third surface 93.

  Now, when the horizontal length of the light collecting unit 90a is L, the height in the vertical direction is H, and the width in the direction perpendicular to the paper surface is constant, the light collecting magnification of the light collecting device 9 is generally (Incident area) / (exit area) = L / H. In this specification, the light collecting magnification defined based on the geometric shape of the light collecting device is referred to as “shape light collecting magnification” in this specification. From the above formula, it is required to reduce the apex angle α in order to increase the shape condensing magnification.

  However, when the apex angle α is decreased, the incident angle of the light incident from the first surface 91 on the second surface 92 is also decreased, and the incident angle θ of sunlight on the first surface 91 is increased by a considerable amount. Otherwise, incident light will pass through the second surface 92. On the other hand, when the incident angle θ is increased, the light intensity (energy density) per unit area of the sunlight incident on the first surface 91 is lowered, so that it is difficult to efficiently collect the light energy of the sunlight.

  Therefore, the reflective surface is formed by vapor-depositing a metal film on the second surface 92 or by attaching a mirror, and the like, and the reflection on the second surface 92 and the total reflection on the first surface 91 are repeated. A condensing device configured to condense light onto the third surface 93 has been proposed (see, for example, Patent Document 1 and Patent Document 2).

JP-A-6-275859 JP 11-340493 A

  Certainly, by forming a metal film or the like on the second surface 92 as a reflective surface, the light reflected by the second surface 92 is set so as to satisfy the total reflection condition when entering the first surface 91. For example, the light that has been diffracted and condensed a plurality of times between the first surface 91 and the second surface 92 can be guided to the third surface 93. Therefore, light can be efficiently incident into the light condensing unit 90a, and the shape condensing magnification can be increased.

  However, in such a configuration, since the reflection on the second surface 92 is caused by a metal film, a mirror, or the like, loss of light energy due to absorption of the reflection surface cannot be excluded. Since the light incident on the condensing device 9 is condensed by being diffracted a plurality of times between the first surface 91 and the second surface 92, the energy loss is a power of the number of reflections, and in the condensing process (light guiding process). There was a problem that the energy decrease of the large.

  The present invention has been made in view of the above problems, and provides a condensing device capable of concentrating light energy such as sunlight more efficiently by suppressing energy loss in the condensing process. For the purpose. It is another object of the present invention to provide a photovoltaic device that can use light energy such as sunlight more efficiently.

  In order to achieve the above object, a first embodiment illustrating the present invention is a light collecting device. This condensing device has a first surface on which received light is incident and a second surface that intersects the first surface at an acute angle and is formed of a transparent material. A light-collecting member having a prism-like light-condensing portion that condenses light by being reflected a plurality of times with respect to one surface, and a reflective member provided with the reflective surface facing the second surface. The light converging part is incident on the first surface at an incident angle θ, passes through the second surface, is reflected by the reflecting surface, reenters the light converging part from the second surface, and the reincident light is incident on the first surface. And the intersection angle (vertical angle in the embodiment) α between the first surface and the second surface is the minimum in the angle range in which the re-incident light is totally reflected by the first surface. It is configured to be an angle near the value (an angle of about *% with respect to the minimum value).

  The incident angle θ and the crossing angle α are such that the energy condensing magnification of the light incident on the first surface and condensed by the condensing unit is near the maximum value (for example, the maximum energy in the embodiment shown in FIG. 6). It can be set so that the incident angle θ, which is the condensing magnification, is about ± 5 degrees with respect to 76 degrees. The received light is sunlight, and the intersection angle α can be set in consideration of the viewing diameter of sunlight.

  Furthermore, a condensing device may be configured by including a condensing lens that condenses received light on the second surface so as to face the first surface.

  A second aspect illustrating the present invention is a photovoltaic device. The photovoltaic device includes the above-described condensing device and a photoelectric conversion element that photoelectrically converts light collected by the condensing member.

  In the light condensing device according to the first aspect, the light condensing unit has the light incident on the first surface transmitted through the second surface, reflected by the reflecting surface, and reentered the light condensing unit from the second surface. The reflected light is configured to be totally reflected by the first surface. According to such a condensing device, the first second surface that is incident on the first surface is transmitted and reflected by the reflecting surface, but after reentering the condensing portion, the first surface and the first surface are reflected. The light is totally reflected by the two surfaces and collected. Therefore, the loss of light energy due to absorption of the reflecting surface can be suppressed more than the configuration in which the reflecting surface is formed on the second surface. Furthermore, the condensing device of this configuration is configured such that the intersection angle α between the first surface and the second surface is an angle near the minimum value in the angle range in which the re-incident light is totally reflected by the first surface. Is done. As will be described later, with respect to an arbitrary incident angle θ, the crossing angle α in the reflection state as described above has an angle range with a predetermined width. In the light collecting device of this aspect, the angle is set near the minimum value in the angle range. The angle in the vicinity of the minimum value is an angle in a range on the small angle side including the minimum value, and is set in consideration of the processing accuracy and assembly accuracy of the light collecting member, the angle width of the incident light with respect to the incident central axis, and the like. Therefore, according to the condensing device having such a configuration, it is possible to provide a condensing device that can condense light energy such as sunlight more efficiently by suppressing energy loss in the condensing process.

  In addition, according to the configuration in which the incident angle θ and the crossing angle α are set so that the energy condensing magnification is close to the maximum value, the energy loss in the condensing process is suppressed to the maximum, and light energy such as sunlight is reduced. Furthermore, the condensing apparatus which can condense efficiently can be provided.

  The photovoltaic device of the 2nd mode is provided with the above condensing devices and a photoelectric conversion element which carries out photoelectric conversion of the condensed light. For this reason, the photovoltaic device which can utilize light energy, such as sunlight, more efficiently can be provided.

It is a schematic diagram of the condensing device (and photovoltaic device) of the 1st composition form. It is explanatory drawing for demonstrating the light energy condensed on an output surface, when condensing sunlight with the condensing apparatus which has a prism-shaped condensing part. It is explanatory drawing for demonstrating the difference in the light guide state in three types of condensing apparatuses which have a prism-shaped condensing part. It is explanatory drawing for demonstrating the establishment conditions of a total reflection type condensing device. It is explanatory drawing for demonstrating the establishment conditions of a total reflection + mirror type condensing device. It is the graph which put together the energy condensing magnification when making apex angle (alpha) the minimum with respect to incident angle (theta) about three types of condensing apparatuses. It is a graph which shows the spectrum distribution of sunlight around Japan. It is explanatory drawing which expands and shows the schematic structure and condensing part of the condensing apparatus of a 2nd structure form. It is explanatory drawing which expanded and compared the reflective state of the light ray in the 2nd surface vicinity of a mirror type condensing device and a total reflection + mirror type condensing device among three types of condensing devices. 10 is a graph showing changes in energy arrival efficiency when the inclination angle γ of the central optical axis of sunlight incident on the condensing lens is changed for the two types of condensing devices shown in FIG. 9. It is explanatory drawing for demonstrating the condensing apparatus which has the conventional prism-shaped condensing part.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. First, referring to FIG. 2, the light energy collected on the third surface 93 is based on the case where sunlight is collected by the light collecting device 9 having the prism-like light collecting portion 90a similar to FIG. While explaining. FIG. 2 is a cross-sectional view along a plane on which light traveling along the central optical axis of sunlight refractions.

Now, let L (mm) be the length in the horizontal direction of the condensing unit 90a, H (mm) be the height in the vertical direction, and d (mm) be the width in the direction perpendicular to the paper surface. Further, the irradiation intensity (energy density) of sunlight is set to air mass AM = 1.5 to 1 sun (100 mW / cm ² ) at latitude near Japan, and the first surface 91 of the central optical axis of sunlight is applied. Is the incident angle of θ.

At this time, the energy density E in the 1st surface 91 of the sunlight which injects into the condensing part 90a is represented like the following (1) formula on the basis of the irradiation intensity of sunlight.

If the ratio of the light energy that reaches the third surface 93 out of the light energy of sunlight incident on the first surface 91 (referred to as “energy arrival efficiency” for convenience in this specification) is R, the third surface The energy density X of the light that reaches 1 is expressed by the following equation (2) with reference to the irradiation intensity of sunlight.

  The energy density X obtained by the equation (2) is a ratio of the collected light intensity to the irradiation intensity of sunlight, that is, a light collection magnification expressed with reference to the energy density. Thus, the light collection magnification X obtained with the energy density as a reference is referred to as “energy light collection magnification” in the present specification.

When the crossing angle formed by the first surface 91 and the second surface 92, that is, the apex angle of the light collecting portion 90a is α, and the parallel portion 91p having a thickness h (mm) is provided on the first surface 91, the third surface The height H of 93 is represented by the following formula (3).
H = h + L * tan α (3)

  Inventors calculated the energy condensing magnification X obtained by each type of condensing device about the case where the second surface 92 of the condensing part is the three types shown in FIGS. 3 (1) to (3). . Here, FIG. 3 is a schematic view illustrating a state in which a cross-section similar to that of FIG. 2 is partially enlarged, and light incident from the first surface is guided toward the third surface. In FIG. 3, (1) is a light collecting device of the type in which the second surface 92 is a flat polished surface and the light incident from the first surface 91 is totally reflected by the second surface 92, and (2) is a surface polished first. A condensing device of the type in which the second surface 92 is used as a reflecting surface, for example, by depositing a metal film on the two surfaces 92, and (3) a reflecting member (mirror) in which the reflecting surface 96 faces the second surface 92 through an air layer. ) 95 is provided, and the light transmitted through the second surface 92 is reflected by the reflecting surface 96 of the reflecting member 95 so as to be incident again on the condensing member from the second surface 92.

  3 (1) to (3), the length of the condensing part is L = 30 (mm), the incident angle θ of the central optical axis of sunlight is 72 degrees, and the viewing diameter is 0.52 degrees. When the refractive index of the member is set to n = 1.5, the state where the energy collection magnification X is maximized is illustrated for each type. Hereinafter, for convenience of explanation, (1) is referred to as “total reflection type”, (2) is referred to as “mirror type”, and (3) is referred to as “total reflection + mirror type”.

(Energy condensing magnification of total reflection type condensing device)
First, taking a total reflection type condensing device as an example, sunlight incident from the first surface 91 is totally reflected and folded by the second surface 92, propagates inside the condensing member, and is totally reflected by the first surface 91. The conditions for this will be described with reference to FIG. FIG. 4 is a cross-sectional view similar to FIG. 2, and the same reference numerals as those in FIG. For simplicity of explanation, it is assumed that there is no wavelength dispersion and no absorption of the light collecting member 90.

As shown in FIG. 4, the light incident on the condensing unit 90 a from the first surface 91 at the incident angle θ is directed toward the second surface 92 at the refraction angle θ ₁ corresponding to the refractive index n of the condensing member 90. Advance inside the member. At this time, the incident angle θ ₂ to the second surface 92 is θ ₂ = θ ₁ + α, where α is the angle formed by the first surface 91 and the second surface 92, that is, the apex angle of the light collecting portion 90a. is there. The light reflected by the second surface 92 travels toward the first surface 91 inside the member, and enters the first surface 91 at an incident angle θ ₃ . At this time, the incident angle θ ₃ to the first surface 91 is θ ₃ = θ ₂ + α = θ ₁ + 2α. Thereafter, the incident angle on each surface is similarly increased by α.

Therefore, in the total reflection type condensing device, the incident angle θ ₂ = θ ₁ + α when the sunlight incident on the condensing unit 90a from the first surface 91 first enters the second surface 92 is The condition is that the angle of reflection is not less than the total reflection angle in the optical member 90.

The above conditions, that is, the length L of the condensing part 90a = 30 (mm), the incident angle θ of the central optical axis of sunlight to the first surface 91 = 72 degrees, the solar viewing diameter of 0.52 degrees, By applying the refractive index n = 1.5 or the like of the optical member 90 and determining the minimum apex angle α of the total reflection type condensing device, the apex angle α = 2.6 degrees. At this time, the shape condensing magnification L / H and the like are as follows.
L / H = 30 / (0.1 + 30 * tan 2.6 °) = 20.5
・ Cos72 ° = 0.309
・ R = 79.5%
The decrease in energy arrival efficiency R of 20.5% is due to loss (Fresnel loss) due to Fresnel reflection at the incident surface (first surface) 91.

When these values are substituted into the equation (2) to obtain the energy collection magnification X, the energy collection magnification X ₁ of the total reflection type light collecting device is X ₁ = 5.0 (sun).

(Energy condensing magnification of mirror type condensing device)
Next, in the mirror type condensing device, referring again to FIG. 4 for the conditions for the sunlight incident from the first surface 91 to be reflected and condensed by the second surface 92 and the first surface 91. I will explain.

In this type of condensing device, the second surface 92 itself is a reflective surface (mirror surface) by depositing a metal film such as aluminum on the second surface 92 or by bonding a mirror to the second surface 92. It has become. Therefore, the sunlight that has entered the light collecting unit 90 a from the first surface 91 is reflected even if the incident angle θ ₂ when first incident on the second surface 92 is less than the total reflection angle of the light collecting member 90. The light is reflected at the reflection angle θ ₂ by the second surface 92 which is a surface. Therefore, in the mirror type condensing device, the incident angle θ ₃ = θ ₁ + 2α of the light reflected by the second surface 92 and incident on the first surface 91 is equal to or larger than the total reflection angle of the condensing member 90. Is a condition.

Therefore, the same conditions as described above, that is, the length L of the condensing part 90a = 30 (mm), the incident angle θ of the central optical axis of sunlight to the first surface 91 = 72 degrees, and the solar viewing diameter 0.52 When the minimum apex angle α of the mirror type condensing device is obtained by applying the refractive index n = 1.5 or the like of the condensing member 90, the apex angle α = 1.3 degrees. At this time, the shape condensing magnification L / H and the like are as follows.
L / H = 30 / (0.1 + 30 * tan1.3) = 38.4
・ Cos72 ° = 0.309
・ R = 34.4%

  The decrease 65.6% in the energy arrival efficiency R is due to the Fresnel loss at the incident surface (first surface) 91 and the absorption loss 10% at the reflecting surface (second surface) 92. The amount of decrease in energy arrival efficiency R is large because the Fresnel loss at the incident surface is only once when the sunlight is incident on the first surface 91, but the absorption loss at the reflecting surface is the second for sunlight. This is because it increases cumulatively every time it is reflected by the surface 92.

When these values are substituted into the equation (2) to obtain the energy condensing magnification X, the energy condensing magnification X ₂ of the mirror type condensing device is X ₂ = 4.1 (sun).

(Total reflection + Energy collection magnification of mirror type condensing device)
Next, in the total reflection + mirror type condensing device, conditions for efficiently collecting sunlight incident from the first surface 91 will be described with reference to FIG. FIG. 5 is a cross-sectional view similar to FIG. 4, and the same reference numerals as those in FIG.

As shown in FIG. 5, the light incident on the condensing unit 90 a from the first surface 91 at the incident angle θ is refracted at the refraction angle θ ₁ corresponding to the refractive index n of the condensing member 90, and the second surface 92. Is incident at an incident angle θ ₂ = θ ₁ + α. In this type, in order to improve the shape condensing magnification, the incident angle θ ₂ is set to be less than the total reflection angle of the condensing member 90 so that the light incident on the second surface is emitted from the second surface 92 at the emission angle θ ₂₁ . Is set. Second surface light emitted from the 92 is reflected by the reflecting surface 96 of mirror 95, in the case where the reflecting surface 96 and parallel to the second surface 92, second surface 92 from the condensed portion 90a at an incident angle theta ₂₁ Re-incident on. At this time, the refraction angle of light when reentering the member from the second surface 92 is θ _2, which is the same as the incident angle from the first surface 91 to the second surface 92. The light re-entered from the second surface 92 travels inside the member toward the first surface 91 and enters the first surface 91 at an incident angle θ ₃ . The incident angle θ ₃ to the first surface 91 is θ ₃ = θ ₂ + α = θ ₁ + 2α. The subsequent incident angles on each surface are the same as described above, and each time the light enters each surface, it sequentially increases by α.

Therefore, in the total reflection + mirror type condensing device, the sunlight that is incident on the condensing unit 90a from the first surface 91 at the incident angle θ is most efficiently condensed to the first second surface. The incident angle θ ₃ = θ ₁ + 2α when light that is transmitted through the second surface 92 at the time of incidence and re-entered the second surface 92 is incident on the first surface 91 is equal to or greater than the total reflection angle at the light collecting member 90. This is the case.

At this time, the same conditions as those described above, that is, the length L of the light condensing part 90a = 30 (mm), the incident angle θ of the central optical axis of sunlight to the first surface 91 = 72 degrees, If the apex angle α satisfying the above condition is determined by applying the refractive index n = 1.5 or the like of the light collecting member 90 at 52 degrees, the angle range is 1.3 degrees ≦ α. In the present technology, the apex angle α is set to an angle in the vicinity of the minimum value in this angle range, specifically, 1.27 degrees or more (about 3% with respect to the minimum value). In this configuration example, the apex angle α is set to 1.3 degrees. At this time, the shape condensing magnification L / H and the like are as follows.
L / H = 30 / (0.1 + 30 * tan1.3) = 38.4
・ Cos72 ° = 0.309
・ R = 71.7%

  The decrease 28.3% in the energy arrival efficiency R is due to the Fresnel loss at the incident surface (first surface 91 and second surface 92) and the absorption loss 10% at the reflecting surface 96 of the mirror. However, since the light re-entering the condensing unit 90a from the second surface 92 is then totally reflected and collected by the first surface 91 and the second surface 92, the energy loss due to absorption of the reflecting surface is once. Only.

When these values are substituted into the equation (2) to determine the energy collection magnification X, the energy collection magnification X ₃ of the total reflection + mirror type light collecting device is X ₃ = 8.5 (sun). .

From the above, when the incident angle θ of the central optical axis of sunlight is θ = 72 degrees, the energy condensing magnification X of the three types of condensing devices is compared as follows.
-Total reflection type condensing device: Energy condensing magnification X ₁ = 5.0 (sun)
-Mirror type condensing device: Energy condensing magnification X ₂ = 4.1 (sun)
-Total reflection + mirror type condensing device: energy condensing magnification X ₃ = 8.5 (sun)
It can be seen that, under the condition where the incident angle θ of sunlight is 72 degrees, the energy collection magnification of total reflection + mirror type is the highest.

The incident angle θ of the central optical axis of sunlight is changed in the range of θ = 64 to 84 degrees, and the energy condensing magnification X (X ₁ , X ₂ , X ₃ ) is similarly calculated for each type of condensing device. FIG. 6 shows the result of summarizing the results into a graph. In the figure, in order from the left, a total reflection type, a mirror type, and a total reflection + mirror type are obtained, and each is obtained at each incident angle when the incident angle is changed at a pitch of 4 degrees in the range of θ = 64 to 84 degrees. The energy collection magnification is shown by a bar graph. As the apex angle α, a minimum incident angle is applied to each incident angle for each type.

From FIG. 6, in the range of incident angle θ of sunlight = 64 to 84 degrees, the total reflection + mirror type condensing device has the highest energy collection magnification at any incident angle, and the total reflection + mirror type is compared. It can be seen that even when θ = 64 degrees and 84 degrees where the target energy collection magnification is low, it is higher than the maximum energy collection magnification obtained by other types. It can also be seen that in the total reflection + mirror type condensing device, the energy condensing magnification becomes maximum when the incident angle is θ = 76 degrees. The energy collection magnification calculated at this time is X ₃ = 9.1.

(First configuration form)
Hereinafter, a more specific configuration form of the total reflection + mirror type condensing device will be described. The schematic block diagram of the condensing apparatus 1 of a 1st structure form is shown in FIG. FIG. 1 is a cross-sectional view along a plane along which light traveling along the central optical axis of sunlight refracts in the same manner as the above-described drawings.

  In the condensing device 1, a prism-shaped condensing portion 10 a is formed by a first surface 11 that is a light receiving surface, a second surface 12 that intersects the first surface at an apex angle α, and a third surface 13 that is orthogonal to the first surface. The light condensing member 10 and the reflecting member 15 disposed opposite to the second surface 12 via the separation layer 17, and the light transmitted through the second surface 12 out of the light incident from the first surface 11, It is configured to be reflected by the reflecting surface 16 of the reflecting member 15 and re-enter the light collecting unit 10a from the second surface 12. FIG. 1 shows a configuration in which a photoelectric conversion element (solar cell) 18 is disposed on the third surface 13 to form a photovoltaic device PVS1.

  The condensing member 10 is formed of a transparent material having optical transparency with respect to the wavelength of the condensed light. In the condensing device of this configuration, a transparent material having light transmittance corresponding to the spectral distribution of sunlight (see FIG. 7) is used. Examples of such a transparent material include various optical glasses represented by BK7, and transparent resin materials such as PMMA (polymethyl methacrylate) and PC (polycarbonate). The first to third surfaces 11 to 13 are formed by optical polishing flat. Note that the length L of the light collecting unit 10a, the width d in the direction perpendicular to the paper surface, and the like can be arbitrarily set depending on the size of the photoelectric conversion element 18, the scale of the system in which the light collecting device 1 is used, and the like. In the present configuration, optical glass having a refractive index n = 1.5 is used, L = 30 (mm), and the apex angle α of the light collecting portion 10a is 0.8 °.

  The reflection member 15 includes a reflection surface 16 that faces the second surface 12 of the light collecting member. In the illustrated configuration example, aluminum is deposited on the upper surface of the base material formed in the same shape as the light collecting member 10 (the outer surface of the light collecting member 10 corresponding to the second surface 12) to form a reflective surface (mirror surface). The formed structure is illustrated. In addition, what is necessary is just to form a reflective surface with a high reflectance with respect to the wavelength band of sunlight, for example, silver, gold | metal | money, copper, etc. may be vapor-deposited and a reflective surface may be formed. An appropriate protective film or the like may be formed according to the material to be deposited. By forming the reflective surface 16 by aluminum vapor deposition, the manufacturing cost of the reflective member 15 can be reduced. On the other hand, by using the reflecting member 15 as a silver or gold coated mirror, the absorption loss on the reflecting surface can be reduced and the energy condensing magnification can be increased.

  The separation layer 17 optically separates the second surface 12 of the light collecting member 10 and the reflective surface 16 of the reflective member 15. The spacing layer 17 in this configuration example is an air layer, and an air gap is formed between the second surface 12 of the light collecting member and the reflecting surface 16 of the reflecting member. The separation layer 17 may be any layer as long as it has a lower refractive index than the light condensing member and can optically separate the second surface 12 and the reflection surface 16. What is necessary is just to be larger than the wavelength (for example, 420-800 nm) of a region with a high energy density.

  Considering general processing accuracy (waviness / roughness) of the second surface 12 of the condensing member and the reflecting surface 16 of the reflecting member, an air gap of at least about 1 μm is generated when the two are overlapped. This air gap is thick enough to optically separate the second surface 12 and the reflecting surface 16 for light in a wavelength band in which the energy density of sunlight is high. For this reason, the second surface 12 and the reflecting surface 16 are arranged to face each other via a required separation layer 17 only by placing and fixing the second surface 12 of the light collecting member 10 on the reflecting surface 16 of the reflecting member 15. Is done. Thereby, the condensing apparatus 1 can be comprised with a simple structure.

  In addition, a spacer having a thickness of about several μm or more is provided between the second surface 12 of the light collecting member and the reflecting surface 16 of the reflecting member (for example, the four corners of the opposing surface). 17 may be formed. According to such a structure, the 2nd surface 12 and the reflective surface 16 can be optically isolate | separated reliably about the whole wavelength band of sunlight.

In the condensing device 1 configured in this manner, the light incident from the first surface 11 at the incident angle θ and transmitted through the second surface 12 is reflected by the reflecting member disposed via the separation layer 17. 16 and then re-enters the condensing part 10a from the second surface 12 at a refraction angle θ ₂ = θ ₁ + α (see FIG. 5). The light re-entered from the second surface travels through the condensing unit and enters the first surface 11 at an incident angle θ ₃ = θ ₁ + 2α. The incident angle θ ₃ is equal to or greater than the total reflection angle of the light collecting member 10 having a refractive index n = 1.5, and this light is totally reflected by the first surface 11 toward the second surface 12, and the second surface. 12 is incident at an incident angle θ ₄ = θ ₁ + 3α (not shown).

As a matter of course, the incident angle θ ₄ exceeds the total reflection angle of the light collecting member 10, is totally reflected by the second surface 12, and goes toward the first surface 11 again. Thereafter, in the same manner, the first surface 11 and the second surface 12 are totally reflected and turned back, and the incident angle θ _n to each surface gradually increases (that is, the light traveling direction gradually approaches the horizontal left). The light is condensed toward the third surface 13. The third surface 13 is an exit surface of the light collector 1, and the light that has been condensed and reaches the third surface 13 exits from the third surface 13. In the configuration example shown in the figure, light emitted from the light collecting device 1 enters the photoelectric conversion element 18 and is converted into electric power.

  The condensing device 1 configured as described above has a significantly higher energy condensing magnification X as compared with conventional total reflection type condensing devices and mirror type condensing devices. Even in the case of a general aluminum vapor deposition film, X reaches 9.1 (sun). Therefore, according to the condensing device 1 having such a configuration, it is possible to provide a condensing device that can condense light energy such as sunlight more efficiently by suppressing energy loss in the condensing process. . In addition, when the reflecting surface 16 of the reflecting member 15 is Ag coated or Au coated, the energy collection magnification can be further increased.

(Second configuration form)
Next, the condensing device 2 of a 2nd structure form is demonstrated with reference to FIGS. Here, FIG. 8 is an explanatory diagram showing the schematic configuration of the condensing device 2 and the condensing unit in an enlarged manner. FIG. 9 is an explanatory diagram comparing the reflection state of light rays in the vicinity of the second surface of the (1) mirror type condensing device and (2) total reflection + mirror type condensing device. FIG. 10 shows the energy arrival efficiency when the tilt angle γ of the central optical axis of sunlight incident on the condensing lens 29 is changed for the mirror type condensing device and the total reflection + mirror type condensing device 2. 6 is a graph showing how R changes.

  The condensing device 2 is broadly classified into a total reflection + mirror type condensing unit 20a and a condensing unit 20b that guides light whose incident angle to each surface is increased by the condensing unit. The optical member 20, the condensing lens 29 that condenses the sunlight on the second surface 22 that is provided opposite to the first surface 21 of the condensing unit 20 a, and the reflecting surface 26 are interposed via a separation layer (air layer) 27. And the reflecting member 25 disposed opposite to the second surface 22 as a main component. Then, the light incident from the first surface 21 through the condensing lens 29 is transmitted through the second surface 22 and reflected by the reflecting surface 26, and reenters the condensing unit 20a from the second surface 22. The surface 21 is configured to be totally reflected.

  The condensing device 2 of this configuration form is basically the point that the incident angle θ of the central optical axis of sunlight with respect to the first surface 21 that is the incident surface is basically 0 degrees, and the sunlight is condensed. The light collecting and incident on the second surface 22 through the lens 29 is different from the light collecting device 1 of the first configuration form. FIG. 8 shows a configuration example in which a photoelectric conversion element (solar cell) 28 is disposed at the end of the light guide 20b to form the photovoltaic device PVS2.

  The condensing member 20 of this configuration form includes a total reflection + mirror type condensing unit 20a and a light guide unit 20b that guides light whose incident angle is increased by the condensing unit 20a. The condensing unit 20a is configured in a prismatic shape or wedge shape having a triangular cross-sectional view by a first surface 21 that is a light receiving surface and a second surface 22 that intersects the first surface 21 at an apex angle α. The light guide portion 20b includes a first surface 21 extending from the light collecting portion 20a and extending rightward, a fourth surface 24 that intersects the second surface 22 at an obtuse angle and extends parallel to the first surface 21, and a paper surface. And front and rear side surfaces (not shown). The third surface 23, which is the exit surface, moves to the right due to the provision of the light guide portion 20b, and is formed at the end portion (right end in the drawing) of the light guide portion 20b opposite to the light condensing portion 20a. .

  The condensing lens 29 is provided above the first surface 21 so as to face the first surface, and the second surface passes through the first surface 21 with sunlight whose central optical axis is irradiated substantially perpendicularly to the first surface 21. 22 is focused and incident. In the illustrated configuration example, the condensing lens 29 is an aspherical lens having a rectangular size of 10 (mm) × 10 (mm), a focal length f = 20 (mm), and a refractive index of 1.5. A case where the central optical axis is perpendicularly incident on the condenser lens 29 will be illustrated. At this time, the incident angle θ of the central optical axis of sunlight entering the first surface 21 through the center of the condenser lens 29 is 0 degree.

  The positive / negative of the inclination γ (see FIG. 8) of the central optical axis of sunlight with respect to the condenser lens 29 is + (plus) when the sun is inclined to the left in FIG. Let-(minus). In FIGS. 8 and 11, ray tracing is performed by setting the sun's viewing diameter to 0.52 degrees (± 0.26 degrees with respect to the central optical axis).

  The condensing member 20 is formed of a transparent material having optical transparency with respect to the wavelength of the light to be condensed, like the condensing member 10 described above. In this configuration example, PMMA having a refractive index n = 1.5 is used, the height H of the light collecting unit 20a and the light guide unit 20b × the width d in the direction perpendicular to the paper surface is 1 (mm) × 1 (mm) The length of the light guide part 20b including the part 20a was set to 100 (mm).

  The reflecting member 25 is configured to have a reflecting surface 26 that faces the second surface 22 of the light collecting member. In the figure, a configuration using an aluminum vapor deposition mirror in which the reflecting surface 26 is the same as or slightly larger than the second surface is illustrated. As described above, a silver cord mirror, a gold coat mirror, or the like may be used.

  The separation layer 27 optically separates the second surface 22 of the light collecting member 20 and the reflection surface 26 of the reflection member 25. In this configuration example, the separation layer 27 is an air layer, and an air gap is formed between the second surface 22 of the light collecting member and the reflection surface 26 of the reflection member. The thickness of the separation layer 27 is not particularly limited as long as the second surface 22 and the reflection surface 26 can be optically separated. Specifically, the wavelength of a region having a high energy density in the wavelength distribution of sunlight (for example, Larger than 420 to 800 nm). For this reason, the second surface 22 and the reflecting surface 26 are disposed to face each other with a required separation layer 27 only by overlapping the reflecting surface 26 of the reflecting member 25 on the second surface 22 of the light collecting member 20 and fixing it. . Thereby, the condensing apparatus 2 can be comprised with a simple structure.

  Note that a spacer having a thickness of about several μm or more is provided between the second surface 22 of the light condensing member and the reflecting surface 26 of the reflecting member (for example, the four corners of the opposing surface), and the separation layer 27. May be formed. According to such a structure, the 2nd surface 22 and the reflective surface 26 can be optically isolate | separated reliably about the whole wavelength band of sunlight.

  Here, in the condensing device 2 of this configuration form, sunlight is collected by the condensing lens 29 and enters from the first surface 21. At this time, the light on the central optical axis that enters the first surface 21 through the center of the lens has an incident angle θ = 0 ° to the first surface, and the second surface 22 has the top of the condensing unit 20a. Incident at an angle α. Also, the incident angle to the second surface 22 differs between the light passing through the center of the lens and the light passing through the edge away from the center. In the figure, the incident angle of the light passing through the left end side is the largest, and the light passing through the right end side The incident angle is the smallest. Therefore, in the total reflection type, the mirror type, and the total reflection + mirror type condensing device, the apex angle α of the condensing unit 20a is different from that of the condensing device 1 of the first configuration described above.

  First, in the total reflection type, the condition is that the incident angle when the light incident from the first surface 21 first enters the second surface 22 is equal to or greater than the total reflection angle of the light collecting member 20. When the minimum apex angle α satisfying this condition is obtained, α = 52 degrees. On the other hand, in the mirror type, the condition is that the incident angle when the light reflected by the second surface 22 enters the first surface 21 is equal to or greater than the total reflection angle of the light collecting member 20. When the minimum apex angle α satisfying this condition is obtained, α = 26 degrees. Further, in the total reflection + mirror type, the incident angle when the light transmitted through the second surface 22 and reflected by the reflection surface 26 is incident on the first surface 21 is equal to or greater than the total reflection angle of the light collecting member 20. It is a condition. The angle range of the apex angle that satisfies this condition is 26 to 51 degrees, and the minimum apex angle is α = 26 degrees.

  Since the azimuth and altitude of the sun change with time, such three types of light collecting devices require a tracking device that tracks the sun. At this time, in order to make the light condensed by the condensing lens 29 surely enter the second surface 22, the area of the second surface 22 viewed from the condensing lens 29 side is large. It is desirable that the apex angle α of the portion 20a is small. Therefore, in the following, a mirror type having a relatively small apex angle α and a total reflection + mirror type will be compared. The mirror-type condensing device is a condensing device in which aluminum is deposited on the second surface 22 of the condensing member in the total reflection + mirror-type condensing device 2 and the second surface itself is a mirror surface. The second surface of the mirror type light condensing device different from the total reflection + mirror type light condensing device 2 is denoted by the symbol “′” and represented as a second surface 22 ′.

  FIG. 9 is a comparison of the reflected state of light rays in the vicinity of the second surface of the (1) mirror type condensing device and (2) total reflection + mirror type condensing device. In the figure, a partial enlarged view of each part surrounded by a frame and denoted by a, b, c, d is shown. (1) a and b in the figure are the reflection states of light rays in the vicinity of the second surface in the mirror type condensing device, and a is the first state of the light incident from the first surface 21 on the second surface 22 '. The reflection state, b is the second reflection state on the second surface 22 '. (2) c and d in the figure are the total reflection + the reflection state of the light beam near the second surface in the mirror type condensing device 2, and c is the vicinity of the second surface of the light incident from the first surface. The first reflection state, d is the second reflection state near the second surface. In both types, the inclination angle γ (see FIG. 8) of the central optical axis of sunlight with respect to the condenser lens 29 is −2 degrees.

  In the mirror type condensing device of FIG. 9 (1), the reflection of the light incident from the first surface 21 into the condensing unit 20a near the second surface is the second surface 22 ′, that is, the first and second times. It is reflection by the reflective surface in which the aluminum vapor deposition film was formed. Thereafter, the light guide 20 b is totally reflected by the first surface 21 and the fourth surface 24 and reaches the third surface 23. In the condensing device of this form, the light incident from the first surface 21 causes an absorption loss at the reflecting surface every time it is reflected by the second surface 22 '. The energy reaching efficiency R of the mirror type condensing device calculated under these conditions was 64%.

  In the total reflection + mirror type condensing device 2 in FIG. 9B, the first reflection of the light incident from the first surface 21 into the condensing unit is reflected on the reflecting surface of the reflecting member 25. The reflection by 26 and the second reflection are total reflection by the second surface 22. Thereafter, the light guide 20 b is totally reflected by the first surface 21 and the fourth surface 24 and reaches the third surface 23. Therefore, the light incident from the first surface 21 has an absorption loss at the reflection surface 26 at the first reflection, and a Fresnel loss occurs at the second surface 22 again. However, the second and subsequent reflections by the second surface 22 are total reflection, and no energy loss occurs. The energy arrival efficiency R of the total reflection + mirror type condensing device 2 calculated under these conditions was 71%.

  FIG. 10 shows the inclination angle γ of the central optical axis of sunlight incident on the condensing lens 29 in the range of −3 degrees to +3 degrees for the mirror type condensing device and the total reflection + mirror type condensing device 2. It is the graph which showed the mode of the change of the energy arrival efficiency R when changing. In the figure, the horizontal axis represents the inclination angle γ of the central optical axis of sunlight incident on the condensing lens 29, the left vertical axis represents energy arrival efficiency R, and the right vertical axis represents total reflection + energy of the mirror type condensing device 2. It is a difference ΔR in energy arrival efficiency obtained by subtracting the energy arrival efficiency of the mirror type light collecting device from the arrival efficiency.

  From this figure, the total reflection + mirror type condensing device 2 has higher energy efficiency or equivalent in the entire range of sunlight inclination angle γ = −2 degrees to +2 degrees, which is a substantial use range. ing. In particular, in the range of the inclination angle γ = −2 degrees to −1 degree, the total reflection + mirror type condensing device 2 clearly has higher energy arrival efficiency R, and the difference ΔR reaches a maximum of 7%. .

  In addition, in the range where the inclination | tilt angle (gamma) of sunlight is 0 degree-+2 degree, energy arrival efficiency R is substantially equivalent. This is because the number of reflections in the vicinity of the second surface is as small as two in the illustrated configuration example, the total reflection + Fresnel loss that occurs when re-entering the second surface 22 in the mirror type, and the second time in the mirror type. It is considered that the absorption loss generated at the time of reflection on the second surface 22 ′ is almost equal, that is, the effect of zero loss due to total reflection on the second surface 22 is not sufficiently exhibited. In other words, in the configuration in which the number of reflections in the vicinity of the second surface is 3 or more, the difference ΔR in energy arrival efficiency becomes larger in a wider angle range, and the superiority of the total reflection + mirror type condensing device is exhibited. It is thought that.

  Therefore, according to the condensing device 2 having such a configuration, it is possible to provide a condensing device that can condense light energy such as sunlight more efficiently by suppressing energy loss in the condensing process. .

  And according to the photovoltaic devices PVS1 and PVS2 in which the photoelectric conversion elements 18 and 28 are provided on the third surfaces (outgoing surfaces) 13 and 23 of the light collecting devices 1 and 2 as described above, the light energy of sunlight is increased. A photovoltaic device that can be used with high efficiency can be provided.

  The condensing devices 1 and 2 can be applied not only to a photovoltaic device that converts the light energy of the collected sunlight into electric energy, but also to other forms of energy, for example, devices that convert it into thermal energy. In this case, the light energy collected from the third surfaces 13 and 23 of the light collecting member is incident on a heat pipe with a light absorber, and the collected light energy can be photothermally converted into heat energy.

PVS1 Photovoltaic device PVS2 Photovoltaic device 1 Condensing device 10 of the first configuration form Condensing member (10a condensing part) 11 First surface 12 Second surface 13 Third surface 15 Reflecting member 16 Reflecting surface 18 Photoelectric conversion element ( Solar cell)
2 Condensing device 20 of 2nd composition form Condensing member (20a Condensing part, 20b Light guide part) 21 1st surface 22 2nd surface 23 3rd surface 24 4th surface 25 Reflective member 26 Reflective surface 28 Photoelectric conversion element (Solar cell)
29 Condensing lens L Length of the condensing portion H Height of the condensing portion α Vertex angle of the condensing portion (intersection angle between the first surface and the second surface)
γ Inclination of the central optical axis of sunlight relative to the condenser lens θ Incident angle on the first surface

Claims (5)

A first surface on which received light is incident and a second surface that intersects the first surface at an acute angle are formed of a transparent material, and light incident on the inside of the member is transmitted between the second surface and the first surface. A condensing member having a prism-like condensing part that condenses light by being reflected multiple times between,
A reflective member provided with a reflective surface facing the second surface,
The light converging unit receives light incident on the first surface at an incident angle θ, passes through the second surface, is reflected by the reflecting surface, and reenters the light condensing unit from the second surface. The incident light is configured to be totally reflected by the first surface, and
The intersection angle α between the first surface and the second surface is an angle near a minimum value in an angle range in which the re-incident light is totally reflected by the first surface. .   The incident angle θ and the crossing angle α are set such that an energy collection magnification of light incident on the first surface and collected by the light collecting unit is in the vicinity of a maximum value. The light collecting apparatus according to claim 1. The received light is sunlight,
3. The light collecting device according to claim 1, wherein the intersection angle α is set in consideration of a visual diameter of sunlight.   The condensing device according to claim 1, further comprising a condensing lens that condenses the received light on the second surface so as to face the first surface. The light collecting device according to any one of claims 1 to 4,
The photovoltaic device provided with the photoelectric conversion element which photoelectrically converts the light condensed by the said condensing member.