DE102009032575A1 - Optical arrangement for deflecting and concentrating sunlight on solar cell in solar power plant, has plate aligned to light source so that light is transmitted to Fresnel-structure and enters through boundary surface to medium i.e. air - Google Patents

Abstract

The arrangement has a plate aligned to a light source so that light emitted from the light source enters through a boundary surface (G) into the plate and is reflected from a Fresnel-structure to the boundary surface within the plate. The light is transmitted to a narrow surface within the plate. The plate is aligned to the source so that the light enters through the narrow surface and is transmitted to the Fresnel-structure within the plate by total reflection. The light enters through the boundary surface into an ambient medium i.e. air. The plate is made of glass or plastic.

Description

The The invention relates to an optical arrangement for influencing the propagation direction of light. It is in a first embodiment particularly suitable, from different, temporally to bundle incoming light in changing directions and focused on the receiving surface of a photocell redirect. In a second, this alternative embodiment the invention is preferred for scattering or homogenizing the applicable to a surface light source emitted light.

The first embodiment is for example in connection with photovoltaic systems of interest, where during the day focused sunlight from different directions concentrated On solar cells is directed to the energy efficiency of solar cells to increase.

The Generation of electrical energy from sunlight with the help of Photovoltaic systems is in the current state of the art with less Environmentally friendly systems for generating energy from Expenditure and Cost reasons not competitive because the silicon as a starting material in the production of solar cells relatively is expensive. Therefore, among other things, there is an objective of research and development in this technical field in methods to find that increase the yield of currently common solar cells.

In this regard, Arrangements have already been developed that use the sunlight focus on solar cells.

The Concentration takes place for example with the aid of mirrors or Lenses that are upstream of the solar cells in the direction of irradiation and direct sunlight up to 1000 times more intensely onto the solar cells.

at However, such highly concentrated arrangements becomes predominantly only that sunlight is converted into electricity in the direction of Normals of the receiving surface of the solar cell, ie only in the incidence solder, meets the solar cell. Since the direction of incidence but with changes the position of the sun, the solar cell of the Sun tracked so that the direction the normal also always with changing sun position or as long as the direction corresponds to the sun, otherwise the effect will not take effect, with the concentration is intended.

in the State of the art tracking devices are known which However, so material and cost are that the Energy balance the effort for tracking not justified.

A Therefore, preferred development direction is photovoltaic systems to create sunlight in spite of constant change the sun even without a complicated tracking device continued concentrated and in the direction of the idea solder on the Solar cell is addressed.

This is achieved for example with so-called optical tracking devices. Such a tracking device is in US 20030015233 A1 described. It comprises a collector lens, a solar cell and a lens array. The lens array is disposed between the collector lens and the solar cell and has the task to focus the collected and partially focused by the collector lens radiation concentrated in the incident solder on the solar cell.

In US 5,877,874 is also described a device for concentrating solar radiation on a solar cell. The collection and concentration of sunlight is carried out here by means of a holographic Planarkonzentrators, consisting of a plane-parallel, highly transparent plate and at least one holographic-optical film which is applied to a surface of the plate. The holographic-optical film has a multiplicity of diffractive optical structures which influence the incidence of the sunlight so that it strikes one or more solar cells at an angle which deviates as little as possible from the incidence solder.

These Concentrator photovoltaic systems are still too expensive and too expensive, so it does not succeed, the efficiency significantly increase. In particular, facilities which holograms used to change the direction of solar radiation will not reach the efficiency of conventional, with Mirrors or lenses working concentrators. Reinforce holograms the light striking the solar cells only by a factor of 10, while with classic systems factors between 100 and 1000 can be achieved. On top of that, the cost of holographic systems also relatively are high.

The second embodiment of the invention optical arrangement is particularly for the scattering of light or to homogenize the intensity of a plane Light source radiated light usable. With this embodiment becomes a uniform luminance in a light achieved radiating surface, as for example in Connection with projection devices desirable is.

The known LCD-LED panels, light tunnels or other light having relatively good homogenization properties scattering optical devices do not meet higher demands.

From that Based on the invention, the object is an optical Arrangement for influencing the propagation direction of light to create which overcomes the disadvantages of the prior art as far as possible.

• – mindestens eine durch zwei sich parallel gegenüber liegende Großflächen und umlaufende Schmalflächen begrenzte Platte aus einem transparenten Material, das im Vergleich zu einem umgebenden Medium optisch dichter ist, wobei
• – eine der beiden Großflächen als Grenzfläche für den Übergang des Lichtes aus dem umgebenden Medium in die Platte oder umgekehrt aus der Platte in das umgebende Medium vorgesehen ist,
• – die zweite Großfläche mit einer nach innen reflektierenden Fresnel-Struktur versehen ist, und
• – die Platte zu einer Lichtquelle so ausgerichtet ist, daß das von der Lichtquelle abgestrahlte Licht durch die Grenzfläche hindurch in die Platte eintritt, innerhalb der Platte von der Fresnel-Struktur so zur Grenzfläche zurück reflektiert wird, daß es innerhalb der Platte durch Totalreflexion bis zu mindestens einer der Schmalflächen fortgeleitet wird und dort austritt, oder die Platte zu einer Lichtquelle so ausgerichtet ist, daß das von der Lichtquelle abgestrahlte Licht durch mindestens eine der Schmalflächen in die Platte eintritt, innerhalb der Platte durch Totalreflexion zu der Fresnel-Struktur geleitet wird, von dieser zu der Grenzfläche hin reflektiert wird und infolge dessen durch die Grenzfläche in das umgebende Medium austritt.

According to the invention comprises an optical arrangement of the aforementioned type

• - At least one limited by two parallel large surfaces and circumferential narrow surfaces plate of a transparent material, which is visually denser compared to a surrounding medium, wherein
• One of the two large surfaces is provided as an interface for the passage of the light from the surrounding medium into the plate or vice versa out of the plate into the surrounding medium,
• - The second large area is provided with an inwardly reflective Fresnel structure, and
• - The plate is aligned with a light source so that the light emitted by the light source through the interface penetrates through the plate is reflected within the plate of the Fresnel structure back to the interface that within the plate by total reflection up to at least one of the narrow surfaces is passed and exits there, or the plate is aligned with a light source so that the light emitted by the light source passes through at least one of the narrow surfaces in the plate, is passed inside the plate by total reflection to the Fresnel structure, is reflected from this to the interface and as a result exits through the interface into the surrounding medium.

In a first embodiment of this arrangement is at least one of the narrow sides provided a photocell, and the interface is the light source facing so that the light incident direction with the normal of the interface angle in a range ± φ1 includes. At each of the angles φ1 in this Range ± φ1 will be the light entering the Broken plate to the incidence slot, it comes under one of φ1 dependent angle φ2 in the plate. The Fresnel structure reflects the light at an angle φ3 to the interface back that it's totally at the interface reflected and inside the plate by total reflection to the Narrow side is forwarded, arranged at the photocell is.

there For example, the light source can change its position over time the light incidence direction with the normal of the interface an angle φ1 changing in chronological order included in the range already mentioned ± φ1 lies. The sizes of the angles φ2 and φ3 are dependent on the size of the each current angle φ1 different.

Of the Angle φ1 is preferably within a range from -45 grd to +45 grd. Depending on it the angle φ2 is in a range of -25.9 grd to 25.9 grd and the angle φ3 in a range of 0.001 grd to 55.2 grd, where φ3 = 0.001 grd a grazing Incidence of light on the interface means.

In a second embodiment is at least one of Narrow sides arranged a light source, and that of the light source radiated light enters through this narrow side in the plate. Within the plate, the light is propagated by total reflection, meets the Fresnel structure and is subject to this different directions, with the normal of the interface Includes angle in a range ± φ2, so reflected back to the interface that the Light passes through the interface, while the incident solder is broken away and as a result in different directions, with the normal of the interface angle in a range ± φ1 Include scattered from the plate.

The plane-parallel plate consists for example of glass with a refractive index in the range n = 1.47 to 1.75, while the surrounding medium Air or another, visually thinner compared to this glass Medium with also a refractive index n ≈ 1. At the Of course, glass can also be another Material, such as plastic, can be used, as far as it is described optical requirements met.

in the The invention is based on the use of the first embodiment the optical arrangement for deflecting and concentrating of the Incoming during the course of the day constantly changing direction Sunlight on a solar cell. Also included in the Invention is the use of the invention optical arrangement in the direction of incidence of sunlight several times in succession.

With such a multi-layered arrangement of superimposed and thereby separated by air spaces glass panes is the construction of a complete solar power plant possible.

At Place the multi-layered discs Also, a single thicker slice can be used on it the surface opposite the interface Stepped stepped and with each step mirrored, reflective Fresnel structures, such as will be explained in more detail below.

In this way, the yield is currently übli Solar cells so far increased that is obtained with a smaller number of solar cells more electrical energy than previously possible in the prior art. With the Fresnel structures, a significantly better efficiency is achieved than with the hologram structures known from the prior art.

Instead of a comparatively large number of expensive solar cells For example, a house roof can be equipped with inexpensive glass panes, which collect the sunlight, relative to their orientation divert to the sun by means of the Fresnel structure and then concentrated to a smaller number of solar cells. This results a particularly cost-effective solution.

In an advantageous embodiment is the sun-facing interface the plate provided with a layer that reflects IR radiation. In order to the penetration of this radiation is avoided in the plate and thus an undesirably high heating of the solar cell prevented. In further embodiments, the split off IR radiation useful for hot water or Building heating to be used.

Of the in this way with the inventive arrangement In comparison with the prior art achieved advantage is so far even further intensified, as well as diffused sunlight within the already specified angular range of about -45 grd can be collected to +45 grd, which is especially useful offers advantages in more northerly latitudes.

in the The invention is based on the use of the second embodiment as a surface light source that respects its Intensity radiates homogenized light.

The Invention will be described below with reference to embodiments explained in more detail. In the accompanying drawings demonstrate

1 the basic structure of the arrangement according to the invention in the first embodiment when used for deflecting and concentrating sunlight on a solar cell, here for clarity with only a glass pane and a solar cell,

2 an example of the glass pane after 1 introduced and extending over a region B Fresnel structure and at the same time an example of the course of radiation outside and inside the glass sheet,

3 according to the basic structure 1 in a multiple arrangement of glass panes, which are arranged one behind the other in the direction of irradiation of the sunlight,

4 the multiple arrangement after 3 with alignment of the irradiation surface of the glass panes with changed irradiation direction,

5 the representation analogous to 2 , but in the beam direction according to 4 .

6 to 10 the multiple arrangement after 3 at different irradiation directions given by the position of the sun,

11 a multiple arrangement of glass sheets in the direction of the sunlight in succession, wherein, in contrast to the illustrations in 1 . 3 and 6 to 10 Solar cells are provided on both narrow-side outlet ends of the glass panes,

12 an embodiment of the arrangement according to the invention with a glass pane, which is executed at different areas in different thicknesses and is provided there each with a Fresnel structure,

13 a multiple arrangement of glass panes, as in 12 are shown formed

14 by way of example for illustration in FIG 2 alternative radiation profile when using a Fresnel structure with a flank angle ε = 21 grd with the same refractive index of the glass of n = 1.5178,

15 the basic structure of the arrangement according to the invention in the second embodiment when used for deflecting and scattering or homogenizing the light emitted from a light source arranged on at least one light source and thus to achieve a homogeneous luminance emanating from a surface.

In 1 is provided for the inventive arrangement by way of example a disc S made of glass with the name Bk7, which has a refractive index n = 1.5187 at light of wavelength 546 nm. The disc S has a thickness d = 20 mm and is aligned to the direction of incidence E of sunlight L, that the direction of incidence E with the normal N of the Einstrahlfläche on the disc S, which also defines the interface G between the glass and the surrounding medium , an angle φ1 = ± 0 grd. The surrounding medium in this case is air with the refractive index n ≈ 1, which depends on the respective atmospheric condition.

Preferably, this situation and the orientation of the disc S corresponds to the state of the sun in the zenith. The sunlight L passes through the boundary surface G in the same direction and thus the same angle φ2 = ± 0 grd in the disc S a.

The the boundary G parallel opposite Area of the disc S is with a itself over a Area B extending Fresnel structure provided. The Fresnel structure reflects the sunlight L entering the window S. Interface G back, with the reflection direction with the interface G includes an angle φ3 = 25 grd. Of the Angle or the direction of reflection with the flank angle ε of Fresnel structure set in the one chosen here Example should be 32.5 grd.

Of the Angle φ3 differs from the critical angle of total reflection far from the fact that the light at the interface G in the disc S is reflected back and inside the disc S is passed through total reflection and finally meets a solar cell Z, which at a narrow-side outlet end the disc S is arranged.

The in this way with the solar cell Z obtained amount of electrical Energy is many times higher than direct, unbundled Irradiation of the sunlight L on the same solar cell Z.

Out 2 is the introduced into the glass, over a range B extending sawtooth Fresnel structure with the flank angle ε = 32.5 grd selected here as an example. At the same time, this representation serves to clarify the course of the radiation outside and inside the disc S.

The angle φ1, which includes the direction of incidence E with the normal N of the incident surface of the disc S, here, as already described above, ± 0 grd. Depending on this, according to the function φ ₂ = arcsin (sinφ ₁ / n) with n the refractive index the angle φ2 also ± 0 grd. The Fresnel structure is designed here so that according to the function φ ₃ = 90 grd - (2 · ε - φ ₂ ) the angle φ3 = 25 grd, which leads to the total reflection at the interface G.

The Width of the area B must be limited so that the light after the Reflection at the interface G on as few rectified flanks of the Fresnel structure hits, resulting in a undesirably high degree to a change the angle φ3 and thus lead to less energy would.

3 shows one compared to 1 extended embodiment of the arrangement according to the invention. Here, six slices S1 to S6 are placed in parallel on top of each other and aligned relative to the direction of incidence E of the sunlight L as well as the individual slices S in 1 , Each of the slices S1 to S6 has a region B provided with a Fresnel structure, wherein the regions B from slice S1 to slice S6 are offset from each other by this amount B. In each case between two superimposed writing S1 to S6, an air gap is provided.

Also in 3 illustrated situation, including the orientation of the slices S1 to S6 corresponds, as already in 1 , the state of the sun in the zenith. If the position of the sun deviates from the zenith, situations arise as explained below.

Kick the sunlight, as in 4 shown, at an angle φ1 = -30 grd in the slices S1 to S6, resulting in accordance with the above functions φ2 = -19.2 and Grd φ3 = 5.8 grd. For explanation shows 5 the basic course of the radiation outside and inside the disc S until it hits the solar cell Z.

In the course of the ever changing position of the sun situations arise as exemplarily in 6 and 7 shown. Kick the sunlight like in 6 at an angle φ1 = -20 grd into the slices S1 to S6, the angles φ2 = -13.0 degrees and φ3 = 12.0 degrees are formed. At the in 7 shown angle φ1 = -10 grd, the sun is already approaching the zenith; this results in angles φ2 = -6.6 and φ3 = 18.4 degrees.

In 4 . 6 and 7 are situations in which the sun has not yet reached zenith. In each of these situations, despite the deviation of the irradiation direction E from the normal N, the sunlight L collected and deflected by the slices S1 to S6 is concentrated on the solar cell Z because the sunlight L is refracted toward the entrance slit with the entrance to the slab S1 and thereby penetrates into each of the slices S1 to S6 under an angle φ2 changing with the position of the sun, with the result that the sunlight L in each of the slices S1 to S6 is at an angle φ3 which in turn changes as a function of the position of the sun to the boundary surface G is reflected back at the respective pane S1 to S6, totally reflected at the respective boundary surface G, propagated by total reflection within the respective pane S1 to S6 and finally impinges on the solar cell Z arranged at the narrow-side outlet ends of the panes S1 to S6.

In 8th to 10 is a selection of situations in which the sun has passed the zenith. So considered 8th the situation at an angle φ1 = 10 grd; depending on this we have φ2 = 6.6 grd and φ3 = 31.6 grd. In 9 result in dependence of an angle φ1 = 20 grd for φ2 = 13 grd and for φ3 = 38 grd. In 10 the angle φ1 = 30 grd, depending on that φ2 = 19.2 grd and φ3 = 44.2 grd.

It the angles φ1 and φ2 are always positive, if the sunlight is from the first quadrant of the drawing plane incident on the interface G.

Embodiments such as exemplified in FIG 11 shown. In this case, both narrow-side ends of the slices S1 to S6 are provided as exit ends for the bundled sunlight, and each solar cell Z is arranged there. The Fresnel structures are each positioned symmetrically to an axis A within the slices S1 to S6, so that, when sunlight L is incident parallel to the normal N, a symmetrical radiation course in the slices S1 to S6 results from the axis A as well. With changing sun position arise on both sides of the axis A with the representations in 1 . 3 . 4 and 6 to 10 comparable situations.

It should be emphasized that the number of six discs in the above-described embodiments has been chosen by way of example only. A larger or smaller number is of course within the scope of the invention. Likewise, embodiments in which several of the in 11 shown arrangements are adjacent. With such arrangements, a comparison with the embodiment according to 1 even higher energy efficiency achieved.

Further embodiments will become apparent with arrangements in which instead of superimposed discs glass or plastic plates are used, which, as in 12 and 13 shown, are executed as a whole. These plates are stepped at the bottom, that is, the interface G opposite side stepped. The individual stages correspond to the areas B in terms of their positioning, expansion and texture in the embodiments already described above and are provided with mirrored, inwardly reflecting Fresnel structures. These embodiments have technological advantages, as a thicker single disc is used instead of several thin individual discs. The preparation of the staircase can thus be done in only a single manufacturing step, z. B. by reaction casting, hot stamping or cold pressing, whereby the production is greatly simplified and inexpensive.

Concrete embodiments are analogous to the representations in FIG 1 . 3 . 4 and 6 to 10 conceivable, with mirror-symmetrical structure, as exemplified in 12 represented, or repeatedly lined up as in 13 shown. By such juxtaposition arbitrarily large solar concentrators can be provided.

In the embodiments described so far Fresnel structures are provided with a flank angle ε = 32.5 grd. In addition to this shows 14 by way of example, an alternative radiation profile when using a Fresnel structure with a flank angle ε = 21 grd with the same refractive index of the glass of n = 1.5178. As can be seen here, for the angle φ1 a very wide range of -45 grd to +45 grd is possible.

With the use of optical arrangement according to the invention In this way, that will turn out to be a constantly changing one Direction of incident sunlight deflected by optical means alone and focused on a photocell; a mechanical one Device for tracking the photocell for alignment to the respective light incident direction is not required.

15 shows the basic structure of the arrangement according to the invention in the second embodiment, namely for homogenizing the radiated from the interface G of a disc S light.

How out 15 As can be seen, the light emitted by a light source Q enters the disc S and is propagated within the disc S by total reflection, the different, chaotically distributed propagation directions of the light, of which only a few are shown here for clarity, with the interface G Include angles in the range ± φ3.

In these propagation directions, the light impinges on the flanks F of a mirrored Fresnel structure with, for example, a flank angle ε = 32.5 grd and is reflected back from the flanks F to the boundary surface G. Since the light strikes the flanks F under different propagation directions, the reflection directions are also chaotically different and depend on the respective angle φ3. From here also sawtooth Fresnel structure is in 15 for the sake of clarity, only one flank F is shown.

On the basis of the predetermined flank angle ε, the reflection directions with the normal N of the base area G include angles φ2 which are related to each other on the interface G do not meet the condition of total reflection, so that the light exits through the interface G through from the disc S. In the transition into the less dense medium surrounding the disc, the reflection directions, except for the reflection direction parallel to the normal N, are refracted away from the normal N, so that the light outside the disc S propagates in the directions designated R in a chaotic distribution ,

In the 15 The few directions R illustrated by way of example enclose an angle φ1 with the normal N as a function of the respective angle φ2 or φ3. The angle φ1, which the directions R can assume at the flank angle ε = 32.5 grd, is analogous to that of FIG 2 explained embodiment in the range of about -30 to about +30 grd, here also the angle φ1 in the propagation direction in the first quadrant of the plane is positive.

The radiation proceeds inside and outside the disc S in the embodiment 15 in comparison to the embodiment according to 2 in the opposite direction, but apply essentially the same physical laws. For this reason, the embodiments are after 1 to 14 in a figurative sense for the homogenization or for obtaining a homogeneous luminance emanating from the interface G usable.

LIST OF REFERENCE NUMBERS

A

axis

e

incidence direction

F

flank

G

interface

L

sunlight

N

normal

Q

light source

R

directions

S, S1 to S6

slices

Z

solar cell

φ1, φ2, φ3

angle

ε

flank angle

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 20030015233 A1 [0009]
• US 5877874 [0010]

Claims (11)

Optical arrangement for influencing the propagation direction of light, comprising - at least one by two parallel large areas and encircling narrow surfaces of a limited plate transparent material compared to a surrounding medium is optically denser, where - one of the two large areas as interface (G) for the transition of the light from the surrounding medium into the plate or vice versa is provided from the plate into the surrounding medium, - the second large area with an inwardly reflective Fresnel structure is provided, and - the plate too a light source is aligned so that the of the Light source radiated light through the interface (G) enters the plate, inside the plate of the Fresnel structure is reflected back to the interface (G), that it is within the plate by total reflection up to at least one of the narrow surfaces is forwarded and exit there, or - the plate to a light source is aligned so that the radiated from the light source Light through at least one of the narrow surfaces in the plate enters inside the plate by total reflection to the Fresnel structure is directed, reflected from this to the interface (G) out and as a result passes through the interface (G) enters the surrounding medium. An optical arrangement according to claim 1, wherein - at at least one of the narrow sides of a photocell is arranged, - the Interface (G) of the light source is facing so that the Direction of light incidence with the normal (N) of the interface (G) includes an angle from a range ± φ1, in which the light with the entry into the plate to Einfallslot broken down and thereby under one of the current Angle φ1 dependent angles φ2 in the Plate enters, - The Fresnel structure the light at an angle φ3 dependent on φ2 reflected back to the interface (G), so that - the Light at the interface (G) totally reflected and within the plate is propagated by total reflection, and - on which is arranged on the narrow side photocell is directed. Arrangement according to claim 2, with its position time-varying light source, wherein the light incident direction with the normal (N) of the interface (G) in temporal sequence includes changing angle φ1. Arrangement according to claim 1, wherein - at arranged at least one of the narrow sides of a light source (Q) is - The emitted light from the light source (Q) enters through this narrow side into the plate and within the Plate is propagated by total reflection, while the Fresnel structure and from this in different directions, with the normal (N) the interface (G) angle in a range ± φ2 include, back to the interface (G) is reflected, so that the light through the interface (G) passes through, is thereby broken away from the entrance slot and as a result, in different directions, with the normal (N) the interface (G) angle in the range ± φ1 include, exit from the plate. Optical arrangement according to one of the preceding claims, where the surrounding medium is air and the plate is glass or plastic having a refractive index in the range n = 1.47 to 1.75. Optical arrangement according to one of the preceding claims, where the angle φ1 is in a range of -45 grd to +45 grd. An optical arrangement according to claim 6, wherein depending on from the current angle φ1 - the angle φ2 in a range from -25.9 grd to +25.9 grd, and - of the Angle φ3 is in a range of 0.001 to 55.2 grd. Optical arrangement according to one of the preceding claims, in which the light source facing the interface (G) of the plate provided with an IR radiation reflecting layer is. Optical arrangement according to one of the preceding claims, at which the of the interface (G) opposite lying large area a staircase-shaped Gradation. Use of the optical arrangement according to one of The above claims for redirecting and concentrating the from the constantly changing direction during the day incident sunlight onto a solar cell (Z). Use of the optical arrangement according to one of aforementioned claims as surface light source, the homogenized with respect to its intensity Light radiates.

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