WO2008141621A2

WO2008141621A2 - Photovoltaic device comprising solar cells that are laterally mounted on optical elements

Info

Publication number: WO2008141621A2
Application number: PCT/DE2008/000831
Authority: WO
Inventors: Erich W. Merkle
Original assignee: Solartec Ag
Priority date: 2007-05-21
Filing date: 2008-05-19
Publication date: 2008-11-27
Also published as: WO2008141621A3; DE102007023583A1

Abstract

The invention relates to a photovoltaic device for directly converting solar energy into electric energy, comprising at least one solar cell and at least one first optical element that is associated with the solar cell, said element deflecting the incident solar rays, in a first spectral range that can be converted into electric energy by the solar cell, to the solar cell that is mounted on a lateral surface of the first optical element and the incident solar rays, in a second spectral range that can not be converted into electric energy by the solar cell, deflects away from the surface of the solar cell to a target area that is devoid of solar cells.

Description

PHOTOVOLTAIC DEVICE WITH SIDE-APPLIED SOLAR CELLS ON OPTICAL ELEMENTS

The invention relates to a photovoltaic device (PV device) for the direct conversion of solar energy into electrical energy according to the appended claim 1. The invention also relates to a manufacturing method for such a photovoltaic device (solar module) with at least one solar cell for direct conversion of light in electrical power.

In the field of solar energy use, it has been known for some 50 years that solar energy can also be converted directly into electricity by silicon. Monocrystalline or multicrystalline silicon is usually used in the solar cells customary today. These silicon solar cells convert only part of the spectrum of the incident radiation into electrical current.

Thin-film solar cells are often used to convert solar radiation into electricity.

Higher efficiency with over 39% conversion of solar radiation can be achieved through the use of high performance PV cells from higher value semiconductor (MI-IV) semiconductor materials such as silicon dioxide. GalliumArsenide (GaAs) can be achieved.

Such cells based on semiconductor material can be constructed stepwise as single, tandem, triple cells or multiple stack cells and thereby use solar radiation with a broader frequency spectrum. However, the large-scale production of such cells is very expensive. It was therefore chosen the approach to focus the incident solar radiation on a very small area of, for example, below a few hundred square millimeters or even below one square millimeter. Only for this small area then a solar cell is necessary. The material input can then be less than 1% compared to the large-scale use of such cells. The concentration makes it possible to use the high luminous efficacy of high-performance PV cells of currently over 39%.

From the document DE 103 20 663 A1, a PV device for concentrating solar radiation (hundred to a thousandfold concentration) on microsolar cells made of semiconductor material is known. The PV device has a closed housing, in the interior of which at least one optical device and at least one associated microsolar cell are arranged. The at least one optical device concentrates the incident light more than 100 times each on an associated micro-solar cell with a smaller area than a few hundred square millimeters. For tracking on the position of the sun, the at least one optical device can be moved independently of the associated micro-solar cell and of the stationary housing and thus tracked to the sun. Also, the unit of a micro solar cell and optical device can be moved independently of the surrounding housing and thus track the sun. Since the efficiency of the micro-solar cell decreases with increasing temperature, the micro-solar cells used therein is in each case surrounded by a heat sink, which is intended to dissipate the accumulated heat from the associated micro-solar cell. The type of mounting of the micro-solar cells in the interior of a housing, despite existing heat sinks around the micro-solar cells leads to problems in the necessary heat dissipation, which remains trapped in the case, as well as contamination of the inside of the PV device and the sensitive micro-solar cells.

Such micro-solar cells are very sensitive to environmental influences, even dust particles and small particles of dirt or moisture can impair their function.

As basically only the connection of several photovoltaic devices allows an economical use of such a photovoltaic device, these are preferably combined to form a solar system.

It is disadvantageous in known solar modules or photovoltaic devices that the solar cells used therein must each be positioned very precisely on the optical axis and / or in the focus of the associated concentrating optical element, which concentrates the incident solar radiation on the smaller surface thereof. The lens systems usually used have a high weight, which leads to a difficult tracking to the sun and increased production costs because of the large amounts of material used.

Usually, only a part of the incident radiation can be converted into electricity by the solar cells used in the process. The convertible solar radiation has wave frequencies v whose photon energy hv is above the energy gap of the semiconductor materials used in the solar cells. This usable by the solar cell part of the radiation is rather shortwave.

The part of the incident solar radiation, which is not converted by the solar cells into electricity, is rather long-wave and makes itself felt as heat.

Since the efficiency of solar cells decreases with an increase in temperature, in such solar modules, the working temperature of the solar cells due to the large amounts of heat that arise during their operation, or due to the incident heat radiation (IR radiation) difficult to keep in a range in the the solar cells can work effectively.

Usually, heat, which is caused during operation of the solar cells or by the incident heat radiation, by means of the environment Air cooling or via heat sink derived. It is also known, for example from document DE 40166665 A1, to avoid high concentrations of the incident solar radiation in order to avoid overheating of the solar cells used therein.

Furthermore, hologram structures with diffraction gratings are known from the prior art.

XuXiang, ZhouBin, LiuChunze, XuChao, WuGuangming, NiXingyuan, ShenJun, who participated in "The 2 ^nd SPIE International Symposium on Advanced Optical Manufacturing." The article entitled "Fabrication of high-sensitivity photosensitive SiO ₂ / Zrθ ₂ gel film by UV exposure" and Testing Technologies ", Shanghai, China, 2005, Proc. of SPIE Vol. 6149, pp. 61490N-1 - 61490N-6, a SiO ₂ ZZrO ₂ -GeI film is disclosed, which is chemically modified with β-diketones and which is prepared by means of a sol-gel process with tetraethyl Ortosilicate is mixed.

In the sol-gel process very thin coatings can be realized. In sol-gel processes, there are a variety of hydrolysis and polymerization reactions that result in the formation of a colloidal solution. Particles having a small diameter of a few hundred nanometers and previously dissolved in a liquid then condense to a gel.

The chemical change makes the above-mentioned gel films photosensitive. During irradiation of these gel films with UV light having a wavelength of 335 nm, the characteristic absorption band shifts to shorter wavelengths with a maximum at 334 nm. The shift of the characteristic absorption band causes a change in the solubility of the above-mentioned gel films. These UV-irradiated gel films become alcohol soluble. These photosensitive gel films are each coated on a silicon dioxide substrate and the exposure to UV radiation is in each case through a mask. Subsequently, these gel films are leached in alcohol. Finally, surface relief gratings with a period of 2 μm and a depth of 80 nm are obtained. Such photosensitive gel films have proven to be advantageous in the production of micro-optical elements.

The invention has for its object to build a photovoltaic device so that a high efficiency of the solar cells is maintained over a longer time.

To solve the problem, the invention proposes a photovoltaic device with the features mentioned in claim 1. Advantageous embodiments can be found in the subclaims.

With the photovoltaic device of the present invention, high solar cell efficiency is obtained over a long period of time by stabilizing the working temperature of the solar cells in a range in which the solar cells can operate efficiently.

In the photovoltaic device according to the invention, by means of at least one first optical element, a deflection of the incident solar radiation in a first spectral range to at least one associated, attached to a side surface of the optical element

Solar cell. The solar cell completely converts the first spectrum of incident solar radiation into electrical energy. The incident radiation in a second spectral range, which is not convertible from the solar cell into electrical energy, is thereby from the first optical element by means of a on the side facing the sun of the first optical

Element existing first hologram structure from the surface of the side-mounted solar cell away on a solar cell-free target area diverted. As is known, solar cells convert the incident solar radiation into heat in a spectral range which they can not convert into electrical energy, in this case the incident solar radiation in the second spectral range. Because the first optical element only deflects the first spectral range of the incident solar radiation that can be converted by the solar cell into electrical energy, an undesired increase in the temperature of the solar cell is avoided. Since the efficiency of a solar cell decreases with an increase in the temperature thereof, a high efficiency of the solar cell over a longer time is obtained.

Because the incident solar radiation in the second spectral range is deflected away from the surface of the solar cell to a solar cell-free target area already on the side of the first optical element facing the sun, the incident solar radiation in the second spectral range becomes the entire immediate vicinity of the solar cell deflected away. This avoids heating of the solar cell, which would convert solar radiation impinging on it into heat in the second spectral range. Thus, a heating of the solar cell due to the incident long-wave heat radiation is avoided, which would otherwise collect in the areas of the first optical element, which are located in the immediate vicinity of the solar cell, and would mitgewarm the solar cell.

By attaching the solar cell on a side surface of the first optical element, the structure of a photovoltaic device according to the invention compared to the structure of a conventional photovoltaic device with optical elements that focus the incident solar radiation on each mounted on its side facing away from the sun solar cells is facilitated. Consequently, the manufacturing costs of a photovoltaic device according to the invention decrease. In a PV device according to the invention eliminates the overhead, which in the usual systems by the case required, very accurate positioning of the solar cells on the optical Axis and / or in the focus of the associated first optical element is required.

In the photovoltaic device according to the invention, the first optical element is planar. Thus, the first optical element can be constructed very accurately. The construction of a planar first optical element requires less effort than the construction of a first optical element having curved refractive surfaces.

On the lateral surface of the first optical element can also be several, such solar cells may be present, each of which can convert the incident solar radiation in the first spectral range into electrical energy. Thus, the efficiency of the photovoltaic device according to the invention is increased.

In order to achieve more efficient utilization of the incident solar radiation, preferably several of the first optical elements, each with at least one laterally mounted solar cell, are present in the photovoltaic device according to the invention.

Preferably, the photovoltaic device according to the invention comprises a plurality of the first optical elements, wherein a plurality of the first optical elements deflect the incident solar radiation in the first spectral range for a plurality of different angles of incidence respectively to the associated solar cell. As a result, the photovoltaic device according to the invention can also operate without tracking, since at different positions in the sun, the incident solar radiation is deflected by the first optical elements onto the at least one associated solar cell.

Also, the photovoltaic device according to the invention may comprise a plurality of the first optical elements, wherein a plurality of the first optical Elements which deflect vertically incident solar radiation in the first spectral range in each case to the associated solar cell. Such a photovoltaic device according to the invention is tracked to the sun and provides high power throughout the day as the solar cells are irradiated throughout the day while the sun is shining.

The first optical element preferably has at least one laterally mounted solar cell with a smaller area than the light entry surface of this first optical element. In this case, the incident radiation in the first spectral range is concentrated on the surface of the solar cell by means of the first optical element. Thus, the effectively utilized area of the solar cell can be substantially reduced, which leads to a minimization of the purchasing or manufacturing costs of the solar cells used.

In the case of the photovoltaic device according to the invention, several of the first optical elements, in particular all the first optical elements, are preferably formed on a common light entry body and / or light exit body. As a result, such inventive first optical elements can be handled and designed more easily. This leads to a reduction in the manufacturing cost of such a photovoltaic device according to the invention.

The first hologram structure of the first optical element is preferably designed such that it deflects the incident solar radiation in the second spectral range at at least one obtuse angle with respect to the straight line perpendicular to the sun-facing side of the first optical element and transmits the incident solar radiation in the first spectral range.

Thus, an increase in the working temperature of at least one

Solar cell can be avoided, as so from the at least one solar cell into heat convertible part of the incident solar radiation on this first does not hit at all. By attaching the first hologram structure to the sun-facing side of the first optical element, the incident heat radiation in the first optical element can not collect, since it is already deflected back on its side facing the sun back into the outside environment. In this case, the incident solar radiation in the second spectral range which can not be converted into electrical energy by the associated solar cell and thus also the incident heat radiation is redirected back into the outside environment. Consequently, the incident solar radiation in the second spectral range and thus also the incident long-wave heat radiation in the immediate vicinity of the solar cell not even advised. This prevents overheating of the solar cell.

The first hologram structure preferably has a plurality of superimposed, in particular planar hologram layers, the incident solar radiation in at least a portion of the second spectral range, which is not convertible by the solar cell into electrical energy, under or at an obtuse angle to that of the sun to deflect the vertical side of the first optical element perpendicular straight line and transmit the incident solar radiation in the convertible from the associated solar cell into electrical energy first spectral range. Such a realization of the first hologram structure is particularly simple and cost-effective and allows a very accurate deflection of the incident sun radiation in the second spectral range which can not be converted into electrical energy by the associated solar cell, since a hologram layer precisely matched to this is provided for each such subrange of the second spectrum ,

Also, the first hologram structure can transmit the incident solar radiation in the first spectral range and the incident solar radiation in the second spectral range at different acute angles to the to the sun-facing side of the first optical element vertical straight line deflect to a solar cell-free target area, the side facing away from the sun of the first optical element in the lateral distance from the at least one solar cell having side surface of the first optical element under the first optical element, in particular immediately below this is present

Consequently, bundling of the incident solar radiation in the second spectral range, in particular of the incident heat radiation, onto the same solar cell-free target region can also be achieved by means of the first optical hologram structure. In this case, the solar cell-free target area on the side facing away from the sun of the first optical element under this, in particular directly below this, in the lateral distance from the solar cell having side surface of the first optical element is present. Due to the fact that the solar cell-free target area is located at a distance from the solar cell, no heat can accumulate in the vicinity of the solar cell which would otherwise heat the solar cell. Here, too, an overheating of the solar cell is avoided.

In particular, the first hologram structure has a plurality of superimposed hologram layers, each of which has a plurality of hologram regions of different hologram nature, the hologram regions of a hologram layer perpendicularly directing the incident solar radiation in a subregion of the second spectral region at different acute angles with respect to the side of the first optical element facing the sun Just in each case deflect to a same target area, which is on the side facing away from the sun of the first optical element in the lateral distance from the at least one solar cell having side surface of the first optical element under the first optical element, in particular directly below it, and solar radiation in the first and the remaining second spectral range passes. So can for each subsection of the second Spectral range in each case a hologram layer be present, which is precisely tuned to the associated portion of the second spectral range. By means of this construction of the first hologram structure, the incident solar radiation in the second spectral range is deflected very precisely to the same solar cell-free target region.

By attaching the first hologram structure on the side of the first optical element facing the sun, a deflection of the incident solar radiation in the second spectral range which can not be converted into electrical energy by the solar cell is carried out on a solar cell-free target area already on the side of the first optical element facing the sun , It is thus achieved that the incident solar radiation in the second spectral range and consequently also the incident thermal radiation do not even reach the part of the associated first optical unit adjacent to the solar cell, since it is deflected beforehand. Consequently, the incident solar radiation in the second spectral range can not reach the surface of the solar cell and be converted by it into heat. This also avoids that the incident long-wave heat radiation collects in the immediate vicinity of the solar cell and heats it.

In a particular embodiment of the invention, a heat conductor plate or an absorber body is mounted under the carrier body of the at least one first optical element, which in particular have a piping system.

The absorber body in particular has a selective absorber. A selective absorber has a particularly high absorption capacity (absorptivity) for the spectral range of solar radiation, in which most of the energy is radiated while the radiation is more infrared

Heat radiation is minimized by a low emissivity. Simple absorber bodies such as black paint, on the other hand, absorb solar radiation as good as they give off heat radiation. When the sun's rays strike an absorber body, short-wave, high-energy radiation is converted into long-wave radiation (heat radiation). Heat that is not absorbed directly by the absorber or emitted by the latter as an emission is reflected back by a reflecting disk which is always present in conventional absorber bodies. The thermal radiation is thus trapped in the absorber body.

Preferably, the first hologram structure is formed so that the solar cell-free target area forms a portion of the heat conductor plate or the absorber body.

The heated absorber body or the heated heatpipe plate transfers the heat to a fluid flowing through the piping system connected to the absorber body or to the heatpipe plate

Heat transfer medium such. Water or oil. This transports the collected heat energy to a thermal utilization such as e.g. a consumer or a heat storage.

The incident heat and the use of an absorber body and the incident solar radiation in the second spectral range with shorter wavelengths are fed by means of flowing through the piping heat transfer medium of the existing solar cell-free target areas of thermal utilization and exploited by this. The heat from the immediate vicinity of the solar cells is dissipated and avoided overheating this.

In particular, the first optical element comprises a second hologram structure and an optical device, wherein the second hologram structure transmits the incident solar radiation in the second spectral range, is present at the sun-facing side of the first optical element and the incident solar radiation in the first spectral range at least at an acute angle relative to the perpendicular to the sun-facing side of the first optical element deflects straight line and the optical device, the deflected by the second hologram structure solar radiation of the solar cell in concentrated form.

The second hologram structure may also be present on the side of the first optical element facing away from the sun and redirect the incident solar radiation in the first spectral range under at least one obtuse angle relative to the straight line on the side of the first optical element facing away from the sun. Also in this case, solar radiation deflected by the second hologram structure is supplied to the solar cell in concentrated form by means of the optical device in concentrated form.

The use of a second hologram structure for deflecting the incident solar radiation in the first spectral range is particularly preferred since such a hologram structure can be realized in a particularly simple and cost-effective manner. The loss of solar radiation incident on such a hologram structure is minimal due to interactions therewith.

The second hologram structure preferably comprises a plurality of superimposed, in particular planar hologram layers which deflect the incident solar radiation in each case at an acute angle to the associated solar cell at an acute angle with respect to the side of the first optical element facing the sun and solar radiation in the second Let spectral range through. Such a realization of the second hologram structure is particularly simple and inexpensive and allows a very accurate deflection of the incident solar radiation in the first spectral range convertible from the associated solar cell into electrical energy, since for each subarea of this first spectral range a precise one coordinated hologram layer is provided.

In particular, the optical device comprises a transparent layer, which transmits the solar radiation, which is deflected by the second hologram structure, to the solar cell by means of total reflection.

In particular, the second hologram structure is present on the side of the first optical element facing the sun and has the transparent planar layer on the side facing away from the sun. The material of this layer is selected with a refractive index such that on the side of this layer facing away from the sun a total reflection of the solar radiation deflected by the second hologram structure occurs in the entire first spectral range. The solar radiation reflected on the side of the transparent layer facing away from the sun is then totally reflected on the side of the transparent layer facing the sun and thus supplied in concentrated form to the solar cell.

The second hologram structure may also be present on the side of the first optical element facing away from the sun and have the transparent planar layer on the side facing the sun. The material of this layer is similar to previously selected with a refractive index such that on the sun-facing side of this layer, total reflection of the solar radiation deflected by the second hologram structure occurs in the entire first spectral range. The reflected on the side of the transparent layer facing the sun

Solar radiation is then totally reflected on the side of the transparent layer facing away from the sun and thus supplied in concentrated form to the solar cell.

In this embodiment of the invention, it is preferred that the first hologram structure present on the side of the first optical element facing the solar side, the incident solar radiation in that of the associated solar cell does not redirect to electrical energy convertible second spectral range back to the outside environment, to avoid that the transparent layer this incident solar radiation in the second spectral range by total reflection of the associated solar cell passes. Since the solar cell would convert the incident solar radiation into heat in the second spectral range, the solar cell is protected from superfluous heating by the presence of the first hologram structure.

In a particularly preferred embodiment of the photovoltaic device according to the invention, the optical device has a first and a second optical device. In this case, the first optical device reflects the solar radiation deflected by the second hologram structure, and the second optical device further reflects the solar radiation reflected by the first optical device. The first optical device also reflects the solar radiation reflected by the second optical device.

In this case, the first and / or the second optical device can be realized particularly simply in each case by means of a third hologram structure, which transmits the impinging solar radiation in the second spectral range and which reflects the impinging solar radiation in the first spectral range.

In particular, the third hologram structure comprises a plurality of hologram layers superimposed on one another which in each case reflect the solar radiation impinging on them in a partial region of the first spectral region and transmit the solar radiation impinging on them in the other first and second spectral regions. Such a realization of the third hologram structure is particularly simple and cost-effective and enables a very accurate reflection of the incident solar radiation in the first spectral range, since a hologram layer which is very precisely matched to this is provided for each subregion of the first spectrum. In particular, the second optical hologram structure and the second optical device are provided on the side of the first optical device facing away from the sun, and the first optical device comprises a semitransparent mirror which reflects the solar radiation deflected by the second hologram structure and the solar radiation reflected by the second optical device ,

Preferably, the second optical hologram structure and the first optical device are provided on the sun-facing side of the first optical device, and the second optical device has a mirror that further reflects the solar radiation reflected by the first optical device.

Also, the second optical hologram structure and the second optical device may be provided on the sun-facing one of the first optical devices. In this case, the first optical device can have a mirror which reflects the solar radiation deflected by the second hologram structure and reflected by the second optical device. In particular, in this arrangement, the second optical device may comprise a semitransparent mirror which reflects the solar radiation reflected by the first optical structure.

The use of mirrors or semi-transparent mirrors allows a particularly simple and cost-effective implementation of the first and / or second optical device.

In these embodiments of the invention, in which the first or the second optical device comprises a mirror, it is particularly preferred that the first hologram structure present on the side of the first optical element facing the sun deflects the incident solar radiation in the second spectral range back into the external environment, because this radiation is also deflected by reflection on the mirror on the solar cell would be converted into heat by it. The solar cell would be heated.

Preferably, the solar cell is mounted in direct contact with a side surface of the first optical element and in particular has a surface which equals the lateral surface of the first optical element.

In a particular embodiment of the invention, a second optical element is present between the at least one solar cell and the lateral surface of the first optical element, which deflects the solar radiation impinging on the side surface of the first optical element having the solar cell in the first spectral range in such a way that this impinges evenly on the surface of at least one solar cell. In particular, the second optical element has at least one fourth hologram structure which deflects the solar radiation impinging on the side surface of the first optical element having the solar cell in the first spectral range in such a way that it impinges uniformly on the surface of the solar cell. A uniform distribution of the solar radiation impinging on the solar cell onto the surface of the solar cell is particularly advantageous since in this way the values of the electrical current generated by the solar cell can be accurately predicted and are so easy to handle. In addition, a local overload of the at least one solar cell can be avoided.

In a particular embodiment of the invention, the at least one solar cell has a surface that is different from the associated side surface of the first optical element. In particular, the surface of the solar cell may be larger than the associated side surface of the first optical element. The existing second optical element behaves like a scattering lens. By reducing very high concentrations of the deflected to the at least one solar cell Solar radiation in the first spectral range, an overload of the solar cell can be avoided and their performance can be precisely controlled. By avoiding the overload of the solar cell, the life of this is increased.

In a particularly preferred embodiment of the invention, the at least one solar cell has an area which is smaller than the lateral area of the first optical element. The existing second optical element behaves like a converging lens and focuses the incident on the associated side surface of the first optical element solar radiation in the first spectral range on the smaller surface of the solar cell. In this case, a very large concentration of the incident solar radiation in the first spectral range can be achieved by first deflecting the incident solar radiation in the first spectral range by means of the first optical element on a side surface and thereby concentrated and then by means of the second optical element on the smaller relative to the side surface Area of the associated solar cell is concentrated. So solar cells can be used with a very small area. The purchase or production costs of the solar cells used are reduced.

In a particular embodiment of the invention, at least one of the hologram structures of the first and / or the second optical element comprises at least one gel photosensitive film having at least one diffraction grating having a given period and depth. The diffraction gratings of such at least one hologram structure can be realized very accurately and inexpensively. In this case, a very accurate deflection of the incident on this solar radiation can be achieved.

Some embodiments of the invention are explained below with reference to the accompanying drawings. It shows:

Fig. 1 is a schematic sectional view of an inventive Photovoltaic device according to a first embodiment with at least a first optical element with a transparent layer.

Fig. 2 is a schematic sectional view of an inventive

Photovoltaic device according to a second embodiment having at least a first, a second optical element, which behaves like a converging lens, a heat conductor plate and a piping system.

FIG. 1 shows a first embodiment of the photovoltaic device or the solar module 10 according to the invention.

Each solar module 10 has a plurality of first optical elements 15, which each have a solar cell 25 on a first side surface 20.

The solar cell 25 can convert the incident solar radiation into electrical energy in a first, rather short-wave spectral range 30. In this case, the incident solar radiation in the remaining second spectral range 35 can only be converted by the solar cell 25 into heat. The incident solar radiation in the second spectral range 35 is rather longwave.

On its side facing the sun, the first optical element 15 has a first planar hologram structure 40, which in particular reflects the incident, rather long-wave solar radiation in the second spectral range 35 at an obtuse angle (> 90 °, <180 °) back into the external environment and lets through the rather short-wave, incident solar radiation in the first spectral range.

The transmitted by the first hologram structure 40, short-wave

Solar radiation in the first spectral range 30 is then produced by means of a side of the first hologram structure 40 facing away from the sun mounted second hologram structure 45 at an acute angle (0, <90 °) relative to the perpendicular to the second hologram 45 straight line deflected.

On the side of the second hologram structure 45 facing away from the sun there is an optical device 50 comprising a transparent layer. The material or the material mixture of the transparent layer encompassed by the optical device 50 is selected so that the solar radiation deflected by the second hologram structure 45 is totally reflected in the first spectral range 30 on the side facing away from the sun of the transparent layer covered by the optical device 50 , After the total reflection, the solar radiation in the first spectral region 30 is totally reflected again at the sun-facing transparent layer encompassed by the optical device 50, then again at the side facing away from the sun from the optical one

Device 50 covered transparent layer reflects u.s.w. and so the solar cell 25 fed. The concentrated solar radiation in the first spectral region 30 is efficiently converted into electrical energy by the solar cell 25.

The incident solar radiation in the second spectral range 35 is deflected back into the external environment by the first hologram structure 40, does not reach the solar cell 25 and can not be converted into heat by this. Thus, overheating of the solar cell 25 is avoided and its working temperature is maintained in a range in which the solar cell 25 efficiently converts solar energy into electric power. The efficiency and the life of the solar cell 25 are increased.

The first existing optical elements 15 are mounted on their side facing the sun on a transparent light entrance plate 60, which forms the common light entrance body of the photovoltaic device 10, and which is passed by the incident solar radiation 29, before each of these 29 is split by a first optical element 15 in different spectral ranges 30, 35.

The first existing optical elements 15 are attached to their side facing away from the sun on a common carrier body 61.

In a second embodiment of the photovoltaic device 10 according to the invention shown in FIG. 2, the first optical element 15 has, on its side facing the sun, the first hologram structure 40 which, in this embodiment of the invention, has a plurality of hologram regions 41, 42 with different holographic properties, the incident solar radiation in the second spectral range 35 to a solar cell-free target area 70, which is present under the first optical element 15, in the lateral distance from the solar cell 25.

All existing first optical elements 15 are connected at their side facing away from the sun with a heat conductor plate 75. The solar cell-free target areas 70, which are each assigned to a first optical element 15, form subregions of the heat conductor plate 75.

A pipeline system 80 is connected to the side of the heat conductor plate 75 facing away from the sun and is present in particular under the solar cell-free target areas 70. Thus, the concentrated on the first target areas 70 incident solar radiation in the second spectral range 35 and thus also focused on the first target areas 70 rather long-wave incident heat radiation, the pipe system 80 via the heat conductor plate 75 and then from a flowing through the piping 80 heat transfer medium such as water or Oil (not shown) at a thermal use (not shown) to be transported. The incident solar radiation in the second spectral range 35 can thus from a be exploited thermal utilization.

On the side of the second hologram structure 45 facing away from the sun, a first optical device 50 comprising a semitransparent mirror is mounted, which is passed by the solar radiation transmitted by the first hologram structure 40 in the first spectral region 30.

On the side of the first optical element 15 facing away from the sun, there is a second hologram structure 45, which redirects the solar radiation 30 impinging on it in the first spectral range at an obtuse angle with respect to the straight line perpendicular to the second hologram structure 45 and on the impinging solar radiation in the first second spectral range 35 passes.

The solar radiation deflected by the second hologram structure 45 in the first spectral range 30 is then reflected at the mirrored, sun-facing side of a semitransparent mirror comprised by a first optical device 50, transmitted by the second hologram structure 45, from a side facing the sun of the second hologram structure 45 present and of a second optical

Means 90 reflected third hologram structure 90 is reflected, then reflected again on the side facing away from the sun of the first optical device 50 included semitransparent mirror 50, etc., and so the solar cell 25 fed. The third hologram structure comprised by the second optical device 90 is designed such that the third hologram structure transmits the incident solar radiation in the first spectral range 30 and the solar radiation deflected by the second hologram structure 45 in the first spectral range 30. In order to avoid disturbing interactions between the second hologram structure 45 and the third hologram structure included in the second optical device 90, the second hologram structure 45 deflects the incident solar radiation in the first spectral region 30 under a blunt Angle relative to the perpendicular to the fifth hologram structure 85 straight line, which differs substantially from the angle formed between the direction of incidence of solar radiation in the first spectral range 30 and the perpendicular to the second hologram 45 straight line.

Finally, the solar radiation in the first spectral region 30 reaches the first side surface 20 of the first optical element 15, on which there is a second optical element 95, which behaves like a converging lens in this embodiment. The solar radiation impinging on the second optical element 95 in the first spectral range 35 is bundled by this 95 onto the surface of the solar cell 25 and then efficiently converted by this 25 into electrical energy.

In this case, the solar cell 25 has an area which is smaller than the light entry area and the first side area of the first optical element 15 and also as the light entry area of the second optical element 95. Thus, the purchase or production costs of the solar cells 25 used can be reduced become.

The solar radiation impinging on the third hologram structure covered by the second optical device 90 in the second spectral range 35 is transmitted by the third hologram structure and impinges on the heat conductor plate 75 present on the side of the second optical device 90 facing away from the sun.

By virtue of this construction, the incident solar radiation in the second spectral range 35 does not reach the solar cell 25 and can not be converted into heat by it. Thus, overheating of the solar cell 25 is avoided and its working temperature is maintained in a range in which the solar cell 25 efficiently converts solar energy into electric power. The efficiency and the life of the solar cell 25 are increased. LIST OF REFERENCE NUMBERS

10 photovoltaic device

15 first optical element 20 first side surface of the first optical element

25 solar cell

29 incident solar radiation

30 solar radiation in the first spectral range 35 solar radiation in the second spectral range 40 first hologram structure

41, 42 areas of the first hologram structure 40 of different holographic nature

45 second hologram structure

50 optical device 55 first optical device

60 common light entry plate

61 common carrier body 70 solar cell-free target area 75 heat conductor plate 80 piping system

90 second optical device

95 second optical element

Claims

1. Photovoltaic device (10) for direct conversion of solar energy into electrical energy with at least one solar cell (25) and at least one of the solar cell (25) associated first optical element (15), the incident solar radiation in a first spectral range (30) , which is similar to the spectral range, which is convertible by the solar cell (25) into electrical energy, which deflects on one of its side surfaces (20) mounted solar cell (25) and on its side facing the sun has a first hologram structure (40) the incident radiation in a second spectral region (35), which is similar to the spectral region which is not convertible by the solar cell (25) into electrical current, deflects away from the surface of the solar cell (25) to a solar cell-free target region (70).

2. Photovoltaic device according to claim 1, characterized in that it comprises a plurality of solar cells (25) and a plurality of first optical elements (15), each having a light entrance surface which is substantially larger than the surface of a solar cell (25). is, wherein each solar cell (25) is associated with at least one of the first optical elements (15) or each first optical element (15) are associated with each solar radiation in the same first spectral range (30) using solar cells.

3. Photovoltaic device according to claim 1 or 2, characterized in that the plurality of optical first elements (15) are formed on a common light entry body (60) and / or light exit body.

4. Photovoltaic device according to one of the preceding claims, characterized in that the first hologram structure (40) transmits the incident solar radiation in the first spectral range (30) and the incident solar radiation in the second spectral range (35) at least at an obtuse angle to the on the sun-facing side of the first optical element (15) deflects vertical straight line or the incident solar radiation in the second spectral range (35) at different acute angle to the sun on the facing side of the first optical element (15) perpendicular straight to the same , solar cell-free target area (70) which deflects on the side facing away from the sun of the first optical element in the lateral distance from the solar cell (25) side surface (20) of the first optical element (15) below the first optical element (15), especially immediately below this is present.

5. Photovoltaic device according to one of the preceding claims, characterized in that the first optical element (15) has an optical device (50) and a second hologram structure (45), wherein the second hologram structure (45) the incident solar radiation in the second spectral range (35) passes on the side facing the sun of the first optical element (15) and the incident solar radiation in the first spectral range (30) at at least one acute angle with respect to the side of the first optical element (15) facing the sun. vertically deflected or on the side facing away from the sun of the first optical element (15) is present and the incident solar radiation in the first spectral range (30) at least an obtuse angle with respect to the side facing away from the sun of the first optical element (15) Just deflects and the optical device (50) from the second hologram Structure (40) redirected solar radiation in the first Spectral range (30) of the solar cell (25) zuleitet.

6. Photovoltaic device according to claim 5, characterized in that the optical device (50) has a transparent layer which directs the deflected by the second hologram structure (45) solar radiation in the first spectral range (30) of the solar cell (25) by means of total reflection ,

7. A photovoltaic device according to claim 5, characterized in that the optical device (50) comprises a first optical means (55) and a second optical means (90), wherein the first optical means (55) of the second hologram structure (55) reflects deflected solar radiation in the first spectral range (30) and the second optical device (90) reflects the solar radiation reflected by the first optical device in the first spectral range (30) further and wherein the first optical device (55) also of the second optical device (90) reflected solar radiation in the first spectral range (30) further reflected.

8. A photovoltaic device according to claim 7, characterized in that the first optical device (55) and / or the second optical device (90) comprises / each comprise a third hologram structure, the sun radiation in the second spectral range (95) passes through and the incident Solar radiation in the first spectral range (30) reflected / reflect each.

9. Photovoltaic device according to one of claims 7 or 8, characterized in that the second optical hologram structure (45) and the second optical Means (90) are provided on the side of the first optical device (55) facing away from the sun, in that the first optical device (55) comprises a semitransparent mirror which transmits the solar radiation deflected by the second hologram structure (45) in the first spectral range (30). and reflecting the solar radiation reflected by the second optical device (90) in the first spectral region (30).

10. Photovoltaic device according to one of claims 7, 8 or 9, characterized in that the second optical hologram structure (45) and the first optical device (55) on the side facing the sun of the first optical device (55) are present and that the second optical device (90) comprises a mirror which reflects solar radiation reflected by the first optical device (55) in the first spectral region (30).

11. Photovoltaic device according to one of claims 7 or 8, characterized in that the second optical hologram structure (45) and the second optical device (90) on the sun facing the first optical device (55) are present and that the first optical means (55) comprises a mirror which deflects the solar radiation reflected by the second hologram structure (45) and reflected by the second optical means in the first spectral region (30) and / or the second optical means (90) comprises a semitransparent mirror which reflects the solar radiation reflected by the first optical structure (55) in the first spectral range (30).

12. Photovoltaic device according to one of the preceding claims, characterized in that between the solar cell (25) and the lateral surface (20) of the first optical element (15), a second optical element (95) is present, which on the the Solar cell (25) having side surface (20) of the first optical element (15) incident solar radiation in the first spectral range (30) deflects in such a way that it impinges uniformly on the surface of the solar cell (25).

The photovoltaic device according to claim 12, wherein the at least one solar cell has a surface different from the side surface of the first optical element to which the solar cell is attached ,

14. Photovoltaic device according to one of the preceding claims, characterized in that at least one hologram structure of the first (15) and / or the second optical element (95) has at least one diffraction hologram with a given diffraction angle.

A photovoltaic device according to any one of the preceding claims, characterized in that at least one of the hologram structures of the first (15) and / or the second optical element (95) comprises at least one photosensitive gel film having at least one diffraction grating having a given period and depth includes.

16. Photovoltaic device according to one of the preceding claims, characterized in that a heat conductor plate (75) or an absorber body for solar thermal purposes with the side facing away from the sun of the first optical element (15) is connected, wherein the absorber body preferably comprises a selective absorber.

17. Photovoltaic device according to claim 16, characterized in that in that a pipeline system (80) is mounted on the side of the heat conductor plate (75) or absorber body facing away from the sun and for dissipating heat arising in the photovoltaic device (10) by incident solar radiation (29) by means of a heat transfer medium and for supplying the thus heated heat transfer medium is used for thermal utilization.

18. Photovoltaic device according to one of the preceding claims, characterized in that at least one solar cell (25) is a micro solar cell, in particular with an areal extent of equal to or less than about 100 mm ² .

19. Photovoltaic device according to one of the preceding claims, characterized in that the solar cell (25) is a multi-layer cell of semiconductor compounds, in particular a tandem or triplets of III-V semiconductor compounds.

20. A method for producing a photovoltaic device (10) according to at least one of the preceding claims.

21. Solar system with a plurality of photovoltaic devices (10) according to at least one of claims 1 to 19.