DE102011112395A1 - Radiant energy converter e.g. power converter for solar radiation, has deflecting unit for directing first portion of incoming radiation on absorber unit, and for converting second portion of radiation into electrical energy - Google Patents

Abstract

The radiant energy converter has deflecting unit (120) for directing a first portion (101a) of incoming radiation on absorber unit (110), and for converting second portion (101b) of radiation into electrical energy. The deflecting unit has photovoltaically active layer (121) with thickness of 10 microns or less. An independent claim is included for system for producing electric power from solar radiation energy.

Description

In general, the present invention relates to systems and devices for converting radiant energy, for example solar radiation energy, into another form of energy, preferably at least partially into electrical energy.

The extreme increase in the cost of fossil fuels, and in particular their limited availability, is increasingly exploring alternative options for generating energy in a cost-efficient and environmentally sound manner. In particular, the conversion of solar radiation energy into other suitable forms of energy, in particular into electrical energy, is becoming increasingly important in the energy supply. At present, many concepts are being developed in practice or are already being used commercially to convert solar energy into electrical energy. For example, there are a large number of solar thermal power plants in which the radiant energy is first of all converted into heat as efficiently as possible, which is then fed via various heat transfer media as process heat to various cycle processes. There are many types of heat generation used in which, for example, the solar radiation is directed in a concentrated manner to an absorber, in which then takes place a heating of the heat transfer medium or directly a working medium. By concentrating the solar radiation, temperatures of over 1000 ° C can be reached, so that the thermal efficiency of a downstream cycle can be correspondingly high, provided that the high temperatures are compatible with the practical conditions of the proposed cycle. In particular, solar thermal power plants are increasingly being installed, in which concentrator surfaces, for example in the form of parabolic troughs, et cetera at least uniaxially track the sun so as to achieve an efficient evaporation of a working medium at a reasonable cost, which is subsequently relaxed directly via a turbine.

Furthermore, large power plants with photovoltaic modules are increasingly installed, thus allowing a direct conversion of radiant energy into electrical energy, but in contrast to the solar thermal power plants, which allow efficient storage of process heat, a continuous operation, at least from an economic point of view not possible is. Furthermore, in particular to increase the efficiency of photovoltaic modules, in some cases expensive production processes are required which make economical use appear less promising, both in small local plants and in larger power plants. While there are promising developments, such as the use of concentrated solar radiation in solar cells having multiple stacked PN junctions, the overall semiconductor surface area required is significantly reduced, however, the starting materials and, in particular, the manufacturing processes are present and very time-consuming in the near future thus costly, so that it is questionable whether with this additional effort overall a cheaper generation of electricity is possible. On the other hand, the well established semiconductor technology based on silicon, which is available in almost unlimited quantities, at least theoretically, suffers from a relatively low efficiency, since in silicon the optical properties and in particular the bandgap energy can not be adjusted in any way. As is known, the conversion of radiant energy into electrical energy in a semiconductor material depends on the extent to which electron / hole pairs are generated in the vicinity of a PN junction, separated from the electric field prevailing in the space charge zone, and provided as an electrical current via suitable contacts can.

In order to generate an electron / hole pair in a semiconductor, it is therefore necessary for the arriving photons to have at least the energy of the band gap, so that an electron can be excited from the valence band into the conduction band. For crystalline silicon, the bandgap energy is about 1.1 eV, so that near infrared radiation and above can be absorbed. On the other hand, the absorption of photons with a much greater energy leads to the generation of an electron / hole pair, but the excess energy is transferred to the electron, which then loses the additional energy in the lattice through scattering, so that a significant portion of the photon energy is converted into heat becomes.

For this reason, it is attempted to provide a plurality of semiconductor materials in such a way that in each case a different bandgap energy enables the efficient absorption of incident radiation, without the substantial portion being converted into heat. Such solar cells have a significantly higher efficiency than conventional silicon solar cells, but require significantly higher costs for the provision of the materials and the process of producing the plurality of stacked semiconductor layers.

With a view to reducing the cost of solar cells, very thin semiconductor layers as thin as a few microns to several hundreds of nanometers are used in the form of amorphous or microcrystalline layers deposited on a suitable substrate using low cost techniques. For example, amorphous silicon can be applied very efficiently over large areas, so that the significantly lower efficiency is accepted due to the significant cost advantages in the production of corresponding solar cells, in particular in applications in which the available area for the mounting of the solar modules is available. Therefore, amorphous solar modules are preferably used, especially in large solar systems. However, in these solar modules there is also the problem that different wavelength ranges of the incident radiation can be converted only to a limited extent into electrical energy, since a complex adaptation and provision of several different bandgap energies is required in this case.

In general, therefore, the situation is often that the most efficient use of a large wavelength range is sought in systems for energy conversion of radiant energy into electrical energy, but the efficient conversion is sometimes associated with great technical effort. In solar thermal systems, although the vast majority of the incident spectrum can be ultimately converted into process heat, but this requires considerable effort in terms of maintenance, construction and operation of a corresponding system, with longer service life, for example in case of failure of a complex unit in the cycle, For example, in the form of a turbine, and the like occur, which can lead to a significantly reduced return, especially in connection with the generally higher installation costs. On the other hand, photovoltaic systems offer the advantage of lower installation costs, a more pronounced modularity in conjunction with lower maintenance, but an increase in the efficiency of the individual solar cells seems attainable only with great effort.

It is therefore an object of the present invention to provide means for the conversion of radiant energy into another form of energy, in particular electrical energy, while avoiding or reducing the problems outlined above, an overall higher efficiency and / or lower installation costs and / or higher Degree of flexibility in operation.

According to the invention, in one aspect of the invention, the aforementioned object is achieved by a radiation energy converter. The radiant energy converter comprises an absorber unit and a deflector unit which is designed to generate electrical energy from a first part onto the deflectors of incident radiant energy and to direct a second part of the incident radiant energy to the absorber unit by reflection.

The radiation energy converter of the present invention thus enables an efficient division of the incident radiation through the deflector unit, which is arranged spatially separated from the absorber unit, so that already a part of this radiation is converted into electrical energy in the deflector unit, whereby a suitable adaptation already in the deflector unit For example, in the form of semiconductor materials and their bandgap energies, and the like, may be to a portion of the incident spectrum without significantly affecting the second portion of the incident radiation and thus being available for further processing in the absorber unit. For example, the deflector unit may comprise one or more suitable material layers usable for conversion of radiation energy of a restricted wavelength range but having corresponding reflection properties or transmission properties such that the second portion of the incident radiation is matched in optical thickness by further material layers, for example bare metal layers dielectric layers, and the like, is directed to the absorber unit. The absorber unit can in turn be adapted in a suitable manner to the incoming radiation, so that, for example, compared to conventional photovoltaic systems results in a higher efficiency, but without elaborate semiconductor materials are required.

In an advantageous embodiment, the deflector unit has a photovoltaically active region. D. h., At least a large part of the optically active surface of the deflector unit can be used as a photovoltaic active region, with a suitable adaptation to the desired wavelength range leads to a relatively high efficiency of the photovoltaic active area, while the remaining radiation or at least a large Part of it is efficiently directed to the absorber unit. For example, if reflection of the second portion of the incident radiation occurs substantially at a backside of the photovoltaic active region, it is preferably adjusted so that its sensitivity is in the lower wavelength region of the incident radiation, so that excessive generation of waste heat due to absorption of photons takes place with a short wavelength.

In an advantageous embodiment, the photovoltaically active region has a semiconductor layer with a thickness of 10 μm or less, which is formed over a metal surface of the deflector unit. In this embodiment, therefore, the photovoltaically active region is provided in the form of a very thin semiconductor layer, so that in particular efficient production processes, such as in the form of chemical vapor deposition (CVD), or Other methods, for example by rolling, can be applied, which allow a large area application, on the other hand, the material consumption is low. For example, there are efficient methods for producing silicon on large-area carrier materials, wherein the bandgap energy or mobility gap that can be set in amorphous silicon also enables absorption, in particular in the visible region of the spectrum, and the lower limit wavelength is significantly smaller compared to, for example, crystalline silicon. Therefore, the absorption of the smaller wavelength portion can be accomplished without high heat dissipation in the photovoltaic active area. In other embodiments, the thin semiconductor layer may also be constructed of compound semiconductors to efficiently absorb a desired wavelength range, in particular, the composition of the compound semiconductors enabling accurate adjustment of bandgap energy.

In a further advantageous embodiment, the absorber unit has a second photovoltaically active region. In this way, the incident spectrum can be divided in a suitable manner, so that an efficient adaptation of the photovoltaically active material used can also take place in the absorber unit. In this case, the deflector unit and the absorber unit are advantageously sufficiently separated spatially so that, for example, the power loss in the deflector unit during the conversion of radiant energy into electrical energy does not affect the second photovoltaically active region in the absorber unit.

In a preferred embodiment, a lower limit frequency for the conversion of incident radiation into electrical energy in the second photovoltaically active region differs from the lower limit frequency of the photovoltaic active region in the deflector unit. That is, these cut-off frequencies are different so that a larger area of the incident spectrum can be more efficiently covered by both photovoltaically active areas. For example, in the deflector unit, suitable materials are provided so that a smaller wavelength fraction is efficiently absorbed and converted into electrical energy, while a larger wavelength region, for example, red light, near infrared, far infrared, is directed to the absorber unit the lower limit frequency is advantageously selected so that light in the near infrared region and in the red region is efficiently absorbed.

For example, silicon material may be used for these purposes, such as in crystalline or polycrystalline form, because about crystalline silicon material has its lower cut-off frequency in the near infrared region, so that this fraction can be efficiently converted, but now the lack of smaller wavelengths does not produce it can contribute to a high power loss. Of course, photovoltaic active regions having a plurality of different cut-off frequencies can also be used so that the width of the region of the efficiently absorbed wavelengths is increased. For example, in other embodiments, the smaller wavelength region is efficiently deflected by the deflector unit while the long wavelength region is absorbed, so that targeted adjustment in the absorber unit is also possible in this case, however, by dividing the incident spectrum into at least two subregions This leads to the fact that the complexity in each of the photovoltaically active areas can be reduced, so that the total manufacturing cost is significantly lower compared to complex solar cells with multiple PN junctions.

In an advantageous embodiment, the absorber unit is designed to provide process heat for the further conversion of radiant energy into another form of energy from the second part of the incident radiation. In this case, for example, an efficient use of the process heat can take place in that, for example, the heat itself is used or at least part of the process heat is used to provide mechanical or electrical energy. For this purpose, corresponding cycle processes can be implemented on the basis of the process heat in order to generate additional electrical energy in addition to the electrical energy already generated in the deflector unit, for instance via the drive of steam turbines, liquid turbines, and the like. It is also possible to store the process heat or a part thereof, so that the process heat is also available in times when there is no solar irradiation, if required. In this way, a hybrid energy converter can thus be provided, in which photovoltaic and process heat are used simultaneously or successively for energy generation. This simultaneous provision of photovoltaic electrical energy and process heat, which can be used in many ways, results in a synergistic effect in applications in which the provision of process heat is an essential aspect. That is, in such applications, providing an absorber unit is required to generate process heat from the solar radiation at high temperature, so that the technical components are required anyway for the elevation of the deflector unit and the absorber unit. In contrast to conventional systems, however, the hybrid system allows the generation of electrical energy already after installation of the deflector unit, in particular in one Installation stage is used in which, where appropriate, the process heat is not available for a long periods of time. In other words, in particular for systems with high output power, a modular installation can be carried out, it being possible for energy to be drawn from at least the deflector unit, so that, if appropriate, higher profitability results for a corresponding installation. Furthermore, such systems for generating a relatively high process heat are usually associated with a higher maintenance, so that optionally in appropriate maintenance phases, especially for the area that is responsible for the process heat, yet the generation of electrical energy via the deflector is possible.

In one illustrative embodiment, the radiant energy converter further comprises a thermoelectric transducer thermally connected to the absorber unit. In this way, at least part of the process heat can be converted into electrical energy without mechanically complex components. If necessary, process heat with a "low" temperature can still be "recycled" to a certain degree, which would otherwise be used only at great expense, for example by means of a thermodynamic cycle process which is designed for low temperatures.

In an advantageous embodiment, the radiation energy converter further comprises a heat transfer medium guided in the absorber unit. That is, in this embodiment, a suitable heat transfer medium, for example, thermal oil, water, and the like is used as an efficient medium to suitably provide and / or store the process heat. Here, in particular, the aforementioned aspect also applies that the radiation energy converter according to the invention also provides electrical energy when, for example, the area for providing the process heat by means of the heat transfer medium is still in the installation phase or in a maintenance phase.

In a preferred embodiment, the deflector unit is part of a concentrator device for concentrating the second part of the incident radiation energy. D. h., The radiation energy converter allows the concentration of the second portion of the incident radiation, so that in the absorber in particular a relatively high temperature can be achieved, even if a part of the incident spectrum and thus the energy transported with it has already been absorbed in the deflector unit, to provide process heat, which can be used in a variety of ways. By way of example, as a result of the higher temperature of the process heat obtained by the concentrated radiation, higher efficiency cycle processes can be carried out if the process heat is processed via corresponding mechanical transducers. In other embodiments in which a photovoltaically active region is provided as an alternative or in addition to generating process heat, the concentrated radiation can also be supplied to the photovoltaically active second region in the absorber unit, so that significantly smaller areas are required there for the necessary semiconductor materials on the one hand contributes to a higher overall efficiency of the second photovoltaically active area and on the other hand generally reduces the costs for the production of the second photovoltaically active area in comparison with modules which are not operated with concentrated radiation.

In an advantageous embodiment, the radiation energy converter comprises an at least uniaxial tracking device which is coupled at least to the deflector unit. As a result of this tracking of at least the deflector unit, the overall yield can be increased both in the deflector unit and in the absorber unit. A uniaxial tracking is a suitable compromise between technical effort to implement the tracking and the resulting increase in the overall efficiency of the radiant energy converter. In the case of uniaxial tracking, it is advantageous, for example, to construct the deflector unit in long rows, so that a high yield is nevertheless achieved in the various sun positions by adjusting the inclination angle of the deflector unit.

For example, the deflector unit can be provided in the form of one or more parabolic troughs, wherein the absorber unit is also provided in a corresponding elongate configuration which is arranged in or at least in the immediate vicinity of the focal line of the parabolic troughs.

In a further advantageous embodiment, the radiation energy converter comprises a device for heating at least part of the deflector device. As a result, it is possible, in particular, to apply process heat in the deflector unit in order, for example, to achieve adaptation to specific process conditions. It is well known that photovoltaic active regions made of amorphous silicon undergo photo-induced degradation, which is reversible when the amorphous silicon material is annealed at temperatures of 150 ° C and higher. In this way, the process heat provided in the radiant energy converter can be efficiently utilized, for example, to maintain the efficiency of the photovoltaically active area in the deflector unit at a high level, by regularly or on demand Heating the deflector unit, such as the semiconductor layers provided therein takes place. For example, the process heat can be stored efficiently and fed to the deflector unit at times, for example at night, so that the reversible resetting of the properties of the photovoltaically active area is possible.

In further illustrative embodiments, the device components that serve to heat a portion of the deflector unit may also advantageously serve to cool a portion of the deflector unit such that controllable temperature conditions prevail during operation of the photovoltaic active area in the deflector unit. In particular, this can be avoided or at least mitigated in phases with maximum irradiation a significant reduction in the conversion efficiency of.

In a further aspect of the present invention, the aforementioned object is achieved by a system for generating electrical energy from solar radiation energy. The system includes a radiant energy converter, previously described, or as also explained in the following detailed description, and a thermodynamic system coupled to and configured with the absorber unit of the radiant energy converter, at least a portion of the second portion directed onto the absorber unit to generate mechanical and / or electrical energy to the incident radiation.

It is also true for the system according to the invention that the flexibility and / or the overall efficiency and / or the profitability in generating electrical energy from solar radiation can be improved in comparison to conventional photovoltaic systems or solar thermal systems, in particular through the interaction of the radiation energy converter and a thermodynamic system.

Further advantageous embodiments are also set forth in the appended claims and are also explained in the following detailed description in conjunction with the accompanying drawings, in which:

1 shows a schematic representation of a system for generating energy from solar radiation, wherein a radiation energy converter according to the invention is provided,

2 schematically shows the radiant energy converter in an embodiment in which photovoltaically active areas are provided both in the deflector unit and in the absorber unit,

3 and 4 show schematically representations of the absorber unit, wherein photovoltaically active areas and / or thermo-electric areas are provided in the absorber unit,

5 and 6 show schematic cross-sectional views of the photovoltaically active region of the deflector unit according to illustrative embodiments,

7 schematically shows the radiation converter with a tracking and

8th the radiation converter according to illustrative embodiments, in which the absorber unit provides process heat, which is used to heat a part of the deflector unit.

1 schematically shows an embodiment of a radiant energy converter 100 , the one deflector unit 120 and an absorber unit 110 having. The deflector unit 120 Is suitably constructed to a part 101 an incident radiation 101 , which occurs in the form of solar radiation, to convert into electrical energy. Furthermore, the deflector unit 120 formed, at least a second part 101b the incident radiation 101 to reflect and on the absorber unit 110 to steer. In the illustrated embodiment is the deflector unit 120 designed so that it serves as a concentrator at least in one direction, so that at least the second part 101b as concentrated radiation at the absorber unit 110 arrives. In this case, the deflector unit 120 a surface shape that is curved in at least one direction to achieve the concentrating effect. For example, the surface shape is at least approximately spherical, parabolic, or the like in FIG 1 shown plane, so that an elongated area with concentrated radiation at or near the absorber unit 110 results. In one embodiment, the deflector unit 120 formed substantially as one or more parabolic troughs, while in other embodiments, other surfaces can be used to radiation to the absorber unit 110 to steer. For example, several deflector units 120 be arranged with a flat surface, that in total also a concentrated radiation at the absorber unit 110 results.

The deflector unit 120 In an advantageous embodiment, it has a photovoltaically active region 121 on, for example, on a suitable substrate 122 is applied. The photovoltaic active area 121 is made of a suitable semiconductor material or a plurality of semiconductor materials, so that a conversion of the radiant energy 101 into electrical energy. Furthermore, the individual material layers are in the range 121 about in connection with the carrier material 122 so provided that at the same time an efficient reflection of the radiation 101b is reached. This is done, for example, by the photovoltaic active area 121 is provided in conjunction with suitable optically active layers such that, for example, the bandgap energy is suitable to efficiently photons the radiation 101e absorb while photons of radiation 101b effectively reflected. As already explained, the electronic and optical properties of semiconductor materials can be adjusted in many ways such that an efficient conversion of radiation energy into electron / hole pairs is restricted to a specific wavelength range.

In one embodiment, for example, the photovoltaically active region 121 designed so that a relatively short-wave fraction of the radiation 101 effectively absorbed and partially converted into electrical energy, while the long-wavelength region is efficiently reflected. For this purpose, for example, the photovoltaic active area 121 in the form of one or more suitable semiconductor materials having bandgap energies in the range of about 1.7-2.5 eV, such as can be accomplished with amorphous silicon and the like. On the other hand, this semiconductor material is then relatively permeable to the longer-wave radiation, which then passes through the carrier material 122 , which is provided, for example, in the form of aluminum, the like, or one or more layers of material that are applied to the substrate, is reflected.

Suitable semiconductor materials and layers for the construction of the photovoltaically active region 121 will be explained in more detail below. It should be noted that in further embodiments, radiation having a short wavelength may be reflected, while radiation having a longer wavelength may be efficiently reflected in the deflector unit 120 can be absorbed and converted into electrical energy, if such an arrangement is considered to be generally advantageous.

The absorber unit 110 spatially from the deflector unit 120 is separated by a distance of several cm to several meters or several tens of meters, is formed in some embodiments that at least a part of the incident there radiation, ie at least a portion of the radiation 101b in the absorber unit 110 continues to be used to generate energy efficiently. For this purpose, the absorber unit 110 suitable means for, in some embodiments by the incoming radiation 101b process heat 130 which can be stored, for example, using appropriate thermal storage 131 and / or directly in a system 132 can be converted to, for example, electrical energy 132b provide while the additional heat at a lower temperature 132a can continue to be used or as waste heat occurs. The process heat 130 can be the direct result of the incoming radiation 101b be so produced by the most complete absorption and conversion in internal energy of an absorber material, or may be waste heat of an intermediate process, which also serves to generate energy. For example, as described in more detail below, in some embodiments, another photovoltaically active region is in the absorber unit 110 be provided by removing the heat 130 is maintained at a desired operating temperature. Of course, only a part of the absorber unit 110 incoming radiation 101b be converted by photovoltaic and / or thermoelectric conversion into electrical energy, while another part is efficiently converted into process heat, so as to optionally provide process heat at a desired high temperature.

2 schematically shows the radiant energy converter, in which the area 121 as a photovoltaic active area in the deflector unit 120 is provided and also a photovoltaic active area 111 in the absorber unit 110 is intended for the direct conversion of radiant energy into electrical energy. Note that generally in the present application, a photovoltaic active region is to be understood as a region in which generation of electron / hole pairs and their separation take place in a built-in electric field due to the presence of a PN junction, which process does not is limited to a specific wavelength range. Electron / hole pair generation for deep infrared wavelengths is also considered photovoltaic activity herein.

The area 111 is thereby advantageously adapted to the incident radiation that results in a high degree of absorption in conjunction with the highest possible conversion efficiency. For this purpose, in some illustrative embodiments, a crystalline semiconductor material is used, since in this case the conversion efficiency is generally significantly higher than in amorphous semiconductor materials. For example, crystalline silicon material can be efficient for the area 111 The band gap energy of about 1.1 eV allows efficient absorption in the near infrared range and for long wavelength light in the visible range, but without the entertaining range of the visible light must be absorbed, since this already in the photovoltaic active area 121 the deflector unit 120 was absorbed. That is, suitable semiconductor materials tuned to two different wavelength ranges for the region 121 and for the area 111 can be used, both areas can be made independently and takes place due to the spatial separation of these two areas, which can be at least a few inches to several meters, no direct thermal influence.

For example, both areas can be made of silicon material, in particular amorphous material for the area 121 which can be applied over a large area in a very efficient deposition process with a low layer thickness. In embodiments in which the deflector unit 120 forms a concentrator surface, therefore, the active region 111 be made with a reduced area and therefore with low cost of materials, so that the use of crystalline semiconductor material does not lead to high production costs. In particular, when using crystalline silicon material, well-established manufacturing methods and material resources can be used, due to the subdivision of the incident radiation through the deflector unit 120 in both areas 121 . 111 a higher efficiency compared to conventional solar modules based on silicon may be expected. For example, by increasing the overall efficiency, and particularly avoiding large heat loss in the crystalline silicon material, the use of expensive semiconductor materials, such as gallium arsenide based, and the like, can be avoided. For a high efficiency of silicon in the active area 111 To ensure this area can be thermally effective with one area 112 can be coupled through which heat can be dissipated efficiently as process heat at a desired operating temperature of the active region, so that thermally stable conditions in the range 111 available.

In other embodiments, the photovoltaic active region 111 in the form of semiconductor solar cells, in which two or more PN junctions are optically connected in series, so that overall the conversion efficiency can be extended to a larger wavelength range. Due to the division by the deflector unit 120 However, in comparison to conventional concentrator solar cells, if necessary, the number of PN junctions required, and thus the total material cost and the production cost can be reduced.

3 schematically shows a cross-sectional view of the absorber unit 110 according to an embodiment in which the photovoltaically active region 111 is provided so that the incoming radiation 101b impinges at relatively well defined angles of incidence so that, for example, the optical properties of the area 111 in a relatively precise manner to the incoming radiation 101b can be adjusted. For this purpose, the surface of the area 111 adapted to the geometry of the incoming beam, which succeeds with many small surface areas with a substantially planar surface or by an overall curved surface. In one embodiment, this is the range 111 so constructed that part of the radiation 101b is absorbed efficiently with shorter wavelength, for example due to the corresponding adjustment of the bandgap energy, as previously explained, while a part 101c with longer wavelength of incident radiation 101b is passed through and on to another component 112 in which then process heat can be generated at a relatively high temperature, the areas 111 and 112 thermally relatively well decoupled from each other. In this arrangement, for example, inexpensive well-proven semiconductor materials, such as in the form of silicon as a crystalline material, can be used, wherein the generation of heat loss in the range 111 is reduced, since a range of wavelengths in the original incoming solar radiation, which are below the cut-off wavelength, already in the deflector unit 120 while, on the other hand, the proportion of radiation 101c essentially only for heating the component 112 contributes, as the area 111 is designed so that he is responsible for the share 101c is essentially transparent.

Of course, other suitable semiconductor materials may be used, as well as the surface shape of the region 111 is suitably chosen when approximately different angles of incidence are considered non-negative or even advantageous.

4 schematically shows a cross-sectional view of the absorber unit 110 in an embodiment in which multiple layers 111 . 111b . 111c of the photovoltaic active area 111 on or above the component 112 are formed. For example, the layer 111b a crystalline semiconductor layer with a PN junction, wherein a bandgap energy is chosen so that it is suitable for the incoming radiation, as also explained above. For example, the layer is 111b provided as a crystalline silicon layer, allowing for the preparation of the active region 111 well proven process technologies and material sources used in semiconductor manufacturing can be used. As previously explained If desired, a tandem arrangement or arrangement with three or more PN junctions in a stacked configuration may also be provided if deemed appropriate for the conversion of radiant energy to electrical energy. The layer 111c is for example a passivation layer with suitable optical properties, in which also an electrode structure 113 is embedded in order to make contact with, for example, an n-doped region in the layer 111b manufacture.

Of course, another connection scheme can also be used in which, for example, the discharge of the electrical charges generally takes place at the rear side and the doped semiconductor layer at the front side is connected to the rear side via suitable contact elements.

The layer 111 is at least partially provided as an electrode material in order to make contact with, for example, a P-doped region of the layer 111b manufacture. The doping of the layer 111b is introduced in the usual way, such as by implantation, diffusion, and the like or by epitaxial layer construction. The starting material is known semiconductor wafers or polycrystalline starting material, which is available with suitable size and electronic properties. In the same way, the electrode 113 as well as the layer 111c produced using known materials and processes, wherein also a suitable contacting individual solar cells in the field 111 in a known manner can be done so that a desired series and / or parallel connection is achieved. If a plurality of different semiconductor materials, for example in the form of silicon / germanium, gallium arsenide with various III components and / or V components, and the like are to be provided, known methods, for example epitaxial growth of the desired semiconductor compound, can also be used for this, so that the required bandgap energies in the respective semiconductor material lead to the desired high conversion efficiency.

The area 112 For example, it is designed as an absorber layer that absorbs as much as possible the entire amount of radiation that covers the area 111 passes. As before with reference to 3 is explained, the areas can 111 and 112 Also be spatially separated, so that if necessary, a certain thermal decoupling is achieved. In this case, in the area 112 a desired high process temperature can be achieved, depending on the radiation energy absorbed in this area per unit of time, without a negative effect on the operating temperature of the photovoltaically active area 111 he follows. In other embodiments, as previously explained, the scope is 112 thermally good with the area 111 coupled and is actively controlled in temperature, for example by providing a suitable heat transfer medium (not shown), so that on the one hand the temperature of the area 111 can be set to a desired value and on the other hand, the heat dissipated by the heat transfer medium is available as process heat.

5 shows a schematic cross-sectional view of an embodiment of the deflector unit 120 in which the photovoltaic active area 121 is provided in the form of an amorphous semiconductor material. For example, the active area has 121 a typical PIN structure in which a lightly doped or undoped layer 121b , for example, is provided in the form of a hydrogen-doped silicon material, while a P-doped layer 121c and an n-doped layer 121 form the required PN junction. These layers are also provided as amorphous silicon material, possibly in conjunction with a suitable carbon doping, to adjust the optical properties accordingly. It is known, for example, that amorphous silicon material is relatively permeable to long-wave radiation due to a certain enrichment with carbon. Furthermore, in the area 121 one or more layers provided, wherein only a single further layer 121d which is, for example, an optically transparent electrode layer and thus a connection to the doped layer 121c manufactures. A backside electrode of the area 121 For example, by a metal of the carrier material 122 be provided, or it will be a special suitable electrode layer on the substrate 122 applied.

The various material layers of the area 121 can be applied by suitable deposition methods, such as chemical vapor deposition (CVD), such as by means of a plasma atmosphere and the like, and this can be done even at low temperatures, so that a variety of support materials 122 for direct application of the area 121 can be provided. In other embodiments, the production of the area 121 be done so that electrically functional solar modules are produced on a suitable carrier film, which in turn then during a suitable phase of the manufacturing process on the carrier material 122 is applied. The optical properties of the area 121 in cooperation with the carrier material 122 be adjusted in one embodiment so that the highest possible degree of reflection is achieved for radiation having a longer wavelength than about the smallest bandgap energy or Mobility gap of the area 121 equivalent. For example, amorphous silicon exhibits rapid decay absorption for wavelengths greater than the bandgap energy so that long wavelength radiation is efficiently transmitted through the region 121 passes through and, for example, on a suitable backsheet layer, such as the substrate 122 , is reflected and after repeatedly traversing the area 121 is directed to the absorber. Because the thickness of the in the field 121 provided semiconductor materials, such as in the form of amorphous silicon, may be very small, for example, less than 1 micron or preferably 500 nm or less, the total loss of radiation, which does not lead to formation of electron / hole pairs, relatively low, so that a large proportion of the originally incident radiation with a wavelength that does not contribute to the electrical conversion anyway, is sent out again.

The layers of the area 121 can be subdivided by appropriate structuring measures into respective solar cells, which are then suitably connected in series and in parallel, as is the case also in typical amorphous solar modules. The structuring of the individual layers takes place for example by laser and / or by etching, in particular if very small lateral distances in the layers 121 to be realized. The deposition of the semiconductor materials in the region 121 is made with a thickness in the range of a few microns or 1 micron and much less, so that here the benefits of amorphous solar modules in terms of the required amount of semiconductor material and the efficiency of the manufacturing processes fully come into play. Furthermore, the thin-film technology also has the advantage that the range 121 is flexible and thus after the coating on the substrate 122 or a separate carrier material can be further deformed, for example when the carrier material 122 should serve as a concentrator surface for the second part of the incident radiation and must have a corresponding curvature.

6 schematically shows a cross-sectional view of the deflector unit 120 in which the photovoltaic active area 121 is also applied in the form of several layers, as explained, for example, previously, in which case at least one further optically active layer 123 is provided, which is effective, for example, to the incident radiation 101b to reflect while the radiation 101 essentially let through and in the active area 121 is absorbed. Furthermore, part of the radiation 101b that is not at the interfaces of the layers 123 and 121 was reflected on the substrate 122 be reflected, and then turn the layers 121 and 123 run through. For this purpose, the optical properties, ie refractive index and absorption coefficient, and the layer thicknesses are suitably adapted, so that a high degree of reflection for the radiation 101b yields while the radiation 101 effectively absorbed. In this way, a large proportion of the radiation is prevented 101b the active area 121 has to go through. Again, well-proven coating methods and patterning strategies for amorphous semiconductor materials and corresponding passivation layers, electrode layer, etc. are used, as they are also used in the technology for amorphous solar cells.

Although the production of the active area 121 can be made significantly simplified and inexpensive, if only a single PIN arrangement is provided, and multiple transitions can be used to a larger wavelength range effective in the active area if necessary 121 to absorb and convert into electrical energy. For example, in amorphous silicon material, other semiconductor materials, such as germanium, and the like can be incorporated to properly match the effective bandgap energy and mobility gap, respectively.

7 schematically shows an embodiment of the radiant energy converter 100 , wherein a means for tracking 140 at least for the deflector unit 120 is provided. In the illustrated embodiment is also the absorber unit 110 mechanically with the deflector unit 120 coupled, so that in the embodiment shown concentrated radiation at the absorber unit 110 can be provided. In the embodiment shown, the tracking is 140 provided as uniaxial tracking, so that, for example, a vertical adjustment is possible, as is suitable for parabolic troughs, for example. In other embodiments, the tracking is 140 designed as a biaxial tracking to allow a concentration in two levels. In other embodiments, the tracking is 140 designed so that individual areas of the deflector unit 120 be suitably adjusted in angle, so that a total of concentrated radiation in the absorber unit 110 arrives, which may not be mechanical with the deflector unit 120 is coupled. In this case, at least a simplified mechanical structure results for the absorber unit 110 , so that process heat can be dissipated more efficiently with less effort of the components involved and also the accessibility of the absorber unit 110 during operation and during maintenance phases is improved.

8th schematically shows an embodiment of the radiant energy converter 100 in cooperation with other thermodynamic components in which at least part of the deflector unit 120 on the absorber unit 110 Directed radiation is converted into process heat. For this purpose, the deflector unit 120 such as the photovoltaic active area 121 which simultaneously efficiently deflects and reflects radiation, as previously described. The absorber unit 110 includes, possibly in conjunction with components for the direct conversion of thermal energy into electrical energy, as described above, at least one heat transfer medium 114 , with which process heat is removed more efficiently, for example in a heat storage 131 which in turn is a thermodynamic system 132 can feed, in which a suitable cycle takes place, for example, with evaporation of suitable working media, by generating pressure, which is used via hydraulic means for generating mechanical energy and / or electrical energy, and the like, where appropriate, the waste heat occurring 132a can continue to be used, for example, in a further low-temperature cycle process, or the waste heat 132a if it has a sufficiently high temperature, can in another system 133 used to have a component 128 , such as a suitable coating, and the like, heat to the photovoltaic active region 121 transferred to. In other embodiments, heat will 131 from the store 131 the system 133 supplied when the waste heat 132a does not have a sufficiently high temperature.

In advantageous embodiments, the system provides 133 Process heat with a temperature of 150 ° C or higher ready, which then on the component 128 , such as by a heat transfer medium, and the like, is transferred to the active area 121 anneal. It is known that, in particular, amorphous silicon undergoes a light-induced degradation, which thus contributes to a reduction in the conversion efficiency. This process is highly reversible when the amorphous silicon layer is annealed at a temperature greater than 150 ° C, with additional electrical fields also being able to be applied. In the present embodiment, therefore, in the absorber unit 110 at least partially used process heat is used efficiently to, if necessary, the semiconductor material in the active area 121 to heat up, so that the degradation occurring is at least partially degraded again. For this purpose, if necessary or regularly the memory 131 or the system 132 provided process heat can be used, such as in phases in which the active area 121 is not in use, so that an elevated temperature does not affect the electronic properties during operation. Therefore, after irradiation and resulting degradation of the active area 121 , which leads to a reduction of the efficiency, regularly the degradation is recycled and the efficiency is raised again, so that overall a higher efficiency for the active area 121 results. The system 133 in conjunction with the as a heat exchanger to the active area 121 acting component 128 may also be used in advantageous embodiments to a desired operating temperature of the active area 121 during exposure to solar radiation. In this way, the already provided component 128 can be used as an efficient cooling system especially at times with maximum solar irradiation, which, depending on the desired operating temperature, the resulting process heat may optionally also be used, such as in a low-temperature cycle, such as an ORC process (organic Rankine cycle), thereby the overall efficiency of the radiant energy converter 100 and related thermodynamic systems.

Claims (14)

Radiation energy converter comprising: an absorber unit ( 110 ) and a deflector unit ( 120 ), which is designed to generate electrical energy from a first part ( 101 ) on the Deklektoreinheit ( 120 ) incident radiation energy ( 101 ) and a second part ( 101b ) of the incident radiation energy by reflection on the absorber unit ( 110 ) to steer. A radiant energy converter according to claim 1, wherein the deflector unit comprises a photovoltaically active region ( 121 ) having. A radiant energy converter according to claim 2, wherein the photovoltaically active region comprises a semiconductor layer having a thickness of 10 μm or less, which is over a support material ( 122 ) of the deflector unit is formed. Radiation energy converter according to claim 1 or 2, wherein a lower limit frequency for the conversion of incident radiation into electrical energy of the photovoltaically active area ( 121 ) of the deflector unit is in the range of visible light. Radiation energy converter according to one of the preceding claims, wherein the absorber unit (110) has a second photovoltaically active region ( 111 ) having. Radiation energy converter according to claim 4 and 5, wherein there is a lower limit frequency for the conversion of incident radiation into electrical energy in the second photovoltaically active region ( 111 ) from the lower limit frequency of the photovoltaically active region ( 121 ) in the deflector unit ( 120 ) is different. Radiation energy converter according to one of the preceding claims, wherein the absorber unit ( 110 ) is formed from the second part ( 101b ) of incident radiation process heat ( 130 ) for the further conversion of radiant energy into another form of energy. A radiant energy converter according to claim 7, further comprising a thermoelectric transducer thermally connected to the absorber unit. A radiant energy converter according to claim 7 or 8, further comprising a heat transfer medium carried in the absorber unit (16). 114 ) having. Radiation energy converter according to one of the preceding claims, wherein the deflector unit is part of a concentrator device for concentrating the second part of the incident radiation energy. Radiation energy converter according to one of the preceding claims, further comprising an at least uniaxial tracking device ( 140 ) which is coupled at least to the deflector unit. Radiation energy converter according to claim 11, wherein the deflector unit is part of a parabolic trough. A radiant energy converter according to claim 9, further comprising means ( 133 . 128 ) for heating at least a part of the deflector device. System for generating electrical energy from solar radiation energy comprising: a radiation energy converter ( 100 ) according to one of the preceding claims and a thermodynamic system ( 131 . 132 ; 133 ), which with the absorber unit ( 110 ) of the radiant energy converter ( 100 ) is coupled and configured to generate mechanical and / or electrical energy at least from a part of the second part of the incident radiation directed onto the absorber unit.

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