DE102011112395B4 - Radiation energy converter for generating electrical energy - Google Patents

Abstract

A radiant energy converter (100) comprising: an absorber unit (110) and a deflector unit (120) having a surface shape curved in at least one direction and serving as a concentrator surface and having a photovoltaic active region (121) of amorphous silicon and configured to conduct electrical Generating energy from a first portion (101a) on the deflector unit (120) of incident radiant energy (101) and directing a second portion (101b) of the incident radiant energy for concentration by reflection onto the absorber unit (110) to form at least a portion thereof Converting process heat (130), wherein the process heat (130) at least partially obtained in the absorber unit (110) is utilized to produce the amorphous silicon in a system (133) providing process heat at a temperature of 150 ° C or higher to heat the active area (121).

Description

In general, the present invention relates to a device for converting radiant energy, for example of 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.

The publication US 4,284,839 describes a solar energy collection device and method wherein a Fresnel lens system and a mirror system are provided to direct solar radiation to an absorber device.

The document US 2003/0 213 514 A1 describes a photovoltaic module that can concentrate in the range of about 500 to more than 1000 units of solar radiation intensity in a power range of several kW up to 50 kW.

The publication DE 10 2008 009 477 A1 describes a solar thermal electric power generation device having an absorber mounted at least partially within an evacuated housing.

The publication DE 28 55 553 A1 describes a solar energy conversion system with a system for focusing the beams, wherein the focused beams are received by solar cells and at least one heat absorber.

The publication DE 10 2006 032 876 A1 describes a heat plate that is designed to be installed or retrofitted behind any solar panel.

The publication DE 10 2007 062 378 A1 describes a method and a device for generating electrical energy, wherein the efficiency of photovoltaic solar energy systems is increased by a cooled region is provided on the side facing away from the irradiation side, the waste heat is further used for energy production.

The publication EP 2 148 377 A1 describes a system for generating energy by solar power, on which a two-dimensional reflector is provided with a holder and a foil-like solar battery. The film forms a partially absorbing and a partially reflecting surface of the reflector.

The publication DE 101 34 901 A1 describes a thin film solar cell module having a transparent substrate, a front side electrode layer, a photovoltaic conversion layer, and a backside layer in the form of an electrode, these layers being sequentially deposited on the substrate.

The publication US 4,371,738 A describes amorphous silicon solar cells in which aging is reduced by annealing such cells at a temperature of about 200 ° C for at least 30 minutes.

It is an object of the present invention to provide means for achieving overall higher efficiency in the conversion of radiant energy to another form of energy, particularly electrical energy, by avoiding or reducing the problems set forth above by taking into account the aging of amorphous silicon.

According to the invention, the aforementioned object is achieved by a radiation energy converter having the features of claim 1. Advantageous variants can be found in the dependent claims.

The radiant energy converter of the present invention allows, among other things, an efficient distribution of the incident radiation through the Deflector unit, which is arranged spatially separated from the absorber line, so that already a part of this radiation is converted in the deflector unit into electrical energy, whereby even in the deflector unit a suitable adaptation, for example in the form of semiconductor materials and their bandgap energies, and the like, to a Part of the incident spectrum can take place without the second part of the incident radiation being significantly influenced and thus 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.

The deflector unit has a photovoltaically active area. That is, at least a large part of the optically active area of the deflector unit can be used as a photovoltaic active area, with a suitable adaptation to the desired wavelength range leads to a relatively high efficiency of the photovoltaically active area, while the remaining radiation or at least a large part of it efficiently is 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.

The photovoltaic active region has a semiconductor layer in the form of amorphous silicon, for example, having a thickness of 10 μm or less formed over a metal surface of the deflector unit. The photovoltaically active region is thus provided in the form of a very thin semiconductor layer of amorphous silicon, so that in particular efficient production methods, 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 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 covered more efficiently overall 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 so that this proportion can be efficiently converted, but the lack of smaller wavelength range now can not contribute to the generation of high power dissipation. 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. In other embodiments, for example, the smaller wavelength region is efficiently deflected by the deflector unit while the long wavelength region is absorbed, so that in this case too, a targeted adaptation in the absorber unit is possible, but by dividing the incident spectrum into at least two subregions results in that the complexity in each of the photovoltaically active regions can be reduced, so that overall the manufacturing costs are significantly lower compared to complex solar cells with multiple PN junctions.

The absorber unit is further configured to provide process heat for the further conversion of radiant energy into another energy form 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 for the elevation of the deflector unit and the absorber unit anyway. In contrast to conventional systems, however, the hybrid system allows the generation of electrical energy already after installation of the deflector unit, which can also be used in particular in an installation stage in which, where appropriate, the process heat is not yet available for longer periods of time. In other words, in particular for systems with high output power, a modular installation can take place, 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. That is, the radiant energy converter allows the concentration of the second portion of the incident radiation, so that a relatively high temperature can be achieved in particular in the absorber, even if a part of the incident spectrum and thus the energy thus transported was already absorbed in the deflector to provide process heat , which is versatile. 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.

The provision of process heat also serves to heat at least a 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 used efficiently to maintain the efficiency of the photovoltaic active region in the deflector unit at a high level by heating the deflector unit, such as the semiconductor layers, regularly or as needed , 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 be advantageous for cooling 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.

• 1 eine schematische Darstellung eines bekannten Systems zur Energieerzeugung aus Solarstrahlung zeigt, wobei ein Strahlungsenergiewandler vorgesehen ist,
• 2 schematisch den Strahlungsenergiewandler der Erfindung zeigt, in dem photovoltaisch aktive Bereiche sowohl in der Deflektoreinheit als auch in der Absorbereinheit vorgesehen sind,
• 3 und 4 schematisch Darstellungen der Absorbereinheit zeigen, wobei photovoltaisch aktive Bereiche und/oder thermo-elektrische Bereiche in der Absorbereinheit vorgesehen sind,
• 5 und 6 schematische Querschnittsansichten des photovoltaisch aktiven Bereichs der Deflektoreinheit gemäß anschaulichen Ausführungsformen zeigen,
• 7 schematisch den Strahlungswandler mit einer Nachführung zeigt und
• 8 den Strahlungswandler gemäß anschaulichen Ausführungsformen zeigt, in denen die Absorbereinheit Prozesswärme bereitstellt, die zum Aufheizen der eines Teils der Deflektoreinheit genutzt wird.

Further details will become apparent from the following description taken in conjunction with the accompanying drawings, in which:

• 1 shows a schematic representation of a known system for generating energy from solar radiation, wherein a radiant energy converter is provided,
• 2 schematically shows the radiant energy converter of the invention, are provided in the photovoltaic active regions in both 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 a radiant energy converter, which is not the subject of the invention and a deflector unit 120 and an absorber unit 110 having. The deflector unit 120 is suitably constructed to be 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 form, the deflector unit 120 is designed so that it serves as a concentrator at least in one direction, so that at least the second part 101b as concentrated radiation arrives at the absorber unit 110. 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 level, 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 has a photovoltaic active area 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 radiation 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 for efficiently photons of the radiation 101 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 certain 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 region 121 is provided in the form of bandgap energies in the range of about 1.7-2.5 eV, as is accomplished with amorphous silicon, for example. 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 absorbed in the deflector unit 120 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 thermo-electrical conversion into electrical energy, while another part is efficiently converted into process heat, thereby optionally provide process heat at a desired high temperature.

2 schematically shows a radiation energy converter 100 according to the present invention, in which the range 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 second 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 second region 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 having to absorb the entertaining portion of the visible light, since this is already present in the photovoltaically active region 121 the deflector unit 120 was absorbed. That is, it can be amorphous silicon for the field 121 and suitable semiconductor materials for the field 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 regions may be made of silicon material, with amorphous material for the region 121 which can be applied over a large area in a very efficient deposition process with a low layer thickness. Because the deflector unit 120 forming a concentrator surface can therefore be the second 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. Especially when using crystalline silicon material for the second region 111 For example, well-established manufacturing processes and material resources may be employed, due to the subdivision of the incident radiation by 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 with silicon in the second active area 111 To ensure this area can be thermally effective with one area 112 can be coupled by the heat efficiently as process heat at a desired operating temperature of the active region can be dissipated, so that thermally stable conditions in the second region 111 are present.

In other embodiments, the photovoltaically active second region becomes 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, with 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 also be used for the second region 111 and also the surface shape of the region 111 is suitably chosen, if for example different angles of incidence are considered to be 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 even an arrangement having three or more PN junctions in a stacked configuration may also be provided, as 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 using known materials and methods, wherein also a suitable contacting of individual solar cells in the area 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 with the photovoltaic active area 121 made of amorphous silicon. 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 or a special suitable electrode layer is applied to the substrate 122.

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 carried out so that electrically functional solar modules on a suitable carrier film are then in turn during a suitable phase of the manufacturing process on the substrate 122 is applied. The optical properties of the area 121 in cooperation with the carrier material 122 In one embodiment, they are set so that the highest possible degree of reflection is achieved for radiation having a longer wavelength than the smallest bandgap energy or mobility gap of the region 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 repeated passage through 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 are reflected, and then in turn pass through the layers 121 and 123. 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, the like 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, furthermore, the absorber unit 110 is also mechanical 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 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 dissipated more efficiently, for example in a heat storage 131 which in turn is a thermodynamic system 132 can feed, in which a suitable cyclic process 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, optionally with the waste heat 132a may be used can, 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.

The system 133 provides process heat at a temperature of 150 ° C or higher, which is then applied to 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 invention, 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, in particular at times with maximum solar irradiation, wherein, depending on the desired operating temperature, the resulting process heat may possibly also be reused, for example in a low-temperature cycle, for example an ORC process
(organic Rankine cycle), thereby reducing the overall efficiency of the radiant energy converter 100 and related thermodynamic systems.

Claims (10)

Radiation energy converter (100) with: an absorber unit (110) and a deflector unit (120) having a surface shape curved in at least one direction and serving as a concentrator surface and having a photovoltaic active region (121) of amorphous silicon, and configured to receive electrical energy from a first portion (101a) to the deflector unit (120) generating incident radiant energy (101) and directing a second portion (101b) of the incident radiant energy for concentration by reflection onto the absorber unit (110) to convert at least a portion thereof to process heat (130); wherein the process heat (130) at least partly obtained in the absorber unit (110) is used to produce the amorphous silicon in the active region (121) by means of a system (133) which supplies process heat with a temperature of 150 ° C. or higher. anneal. Radiation energy converter after Claim 1 wherein the photovoltaic active region (121) has a thickness of 10 μm or less, over a carrier material (122) of the deflector unit (120) is formed. Radiation energy converter after Claim 1 , wherein a lower limit frequency for the conversion of incident radiation into electrical energy of the photovoltaically active region (121) of the deflector unit (120) 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). Radiation energy converter after Claim 3 and 4 wherein a lower limit frequency for the conversion of incident radiation into electrical energy in the second photovoltaic active region (111) differs from the lower limit frequency of the photovoltaic active region (121) in the deflector unit (120). Radiation energy converter according to one of the preceding claims, wherein the absorber unit (110) is adapted to provide from the second part (101b) of the incident radiation at least a portion of the process heat (130) for the further conversion of radiant energy into mechanical or electrical energy. Radiation energy converter after Claim 6 further comprising a thermoelectric transducer thermally connected to the absorber unit (110). Radiation energy converter after Claim 6 or 7 further comprising a heat transfer medium (114) carried in the absorber unit (110). 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 (120). Radiation energy converter after Claim 9 wherein the deflector unit (120) is part of a parabolic trough.

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