WO2002044629A1

WO2002044629A1 - Patterned radiation energy converter

Info

Publication number: WO2002044629A1
Application number: PCT/EP2001/013752
Authority: WO
Inventors: Isabella Mayer; Miladin Lazarov; Reinhard Dasbach
Original assignee: Tinox Gesellschaft Für Energieforschung Und Entwicklung Mbh
Priority date: 2000-11-28
Filing date: 2001-11-26
Publication date: 2002-06-06
Also published as: DE10058931A1; EP1340026A1; AU2002221894A1

Abstract

Patterned radiation energy converter for the conversion of radiation energy in heat energy, comprising a substrate at least partially covered with one or more layers (1, 2), of which at least one (1) is embodied as a radiation-absorbing layer, whereby the thickness (d1, d2) and/or chemical composition of at least one of the layers (1, 2) changes periodically parallel to the surface of the substrate. The invention further relates to a method of the production of the patterned radiation energy converter and the use thereof in solar collectors.

Description

Patterned radiant energy converter

The present invention relates to a patterned radiation energy converter for converting radiation energy into thermal energy, a method for its production and its use.

The CH patent 581 812 discloses a solar collector whose solar-irradiable collector surface has elevations, which are elevations of the substrate to which the solar-irradiable collector surface is applied.

WO-A-9 726 488 discloses colored radiation energy converters (absorbers) which can be used in solar collectors and in which a radiation-absorbing layer is applied to a substrate such as a metal sheet. However, due to the generally high requirements for a perfect optical impression, there is a high rejection due to defects in the coating of sheets with the radiation-absorbing layer or in the further processing of the coated sheets. It can also happen that waves in the coated sheet cannot be avoided by the type of further processing, which are then perceived as unattractive or impairing value. In particular in the further processing of sheets on which a selectively absorbing layer as in WO-A-9 726 488, there are always rejects due to surface defects that have already been introduced into the surface during coating or further processing.

In solar collectors, the heat converted via the steel energy converter is usually transported away via a pipe system, the one Has heat exchanger liquid. When soldering or welding the pipe system to the absorber, however, there are always spots on the absorber surface and waves and dents in the sheet. A committee at this stage of manufacture is associated with high costs.

The object of the present invention was now to provide a radiation energy converter which also meets high aesthetic and technical requirements in the case of slight production defects, so that the number of rejects is reduced.

To achieve this object, a patterned radiation energy converter (absorber) is proposed which has a substrate which is coated with one or more layers, the thickness and / or chemical composition of at least one of the layers changing periodically parallel to the surface of the substrate , This periodic change in the layer parameters causes a periodic change in the brightness and / or the color impression of the surface of the radiation energy converter. At least one of the layers with which the substrate is coated is designed as a radiation-absorbing layer.

It was found by the inventors that, depending on the design of the layer, a loss in efficiency can occur, but this loss is tolerable for the low temperature range, since the reduced power can be compensated for by a slight increase in the collector area. These additional costs due to the greater use of materials can, however, be offset many times over by reducing the scrap.

The invention thus relates to a patterned radiation energy converter (absorber) for converting radiation energy into thermal energy, which comprises a substrate which is at least partially coated with one or more layers, at least one of which is designed as a radiation-absorbing layer. det, wherein the radiation energy converter is characterized in that the thickness and / or the chemical composition of at least one of the layers changes periodically parallel to the surface of the substrate. In addition, the invention relates to a method for producing the radiation energy converter, which is characterized in that one or more layers, of which at least one is formed as a radiation-absorbing layer, are applied to a substrate by means of a vacuum coating method or a wet chemical method, that the thickness and / or the chemical composition of at least one of the layers changes periodically parallel to the surface of the substrate. The invention also relates to the use of the radiation energy converter in a solar collector and / or as a decorative layer. Preferred embodiments of the invention are described in the following description, the figures and the subclaims.

The figures show:

1 a shows a schematic representation of an apparatus for producing a radiation energy converter preferred according to the invention with a stripe pattern:

Fig. Lb is a schematic representation of the mask used in Fig. La;

1c shows a cross section through a radiation energy converter preferred according to the invention, in which the layer thickness of the antireflection layer (layer 2) is varied periodically;

FIG. 1d shows a cross section through a radiation energy converter preferred according to the invention, in which the change in the layer thickness takes place continuously;

Fig. Le is a schematic representation of a wavy mask for generating a constant change in layer thickness; Fig. If a cross section through a preferred radiation energy converter according to the invention, in which the layer thickness of the absorber layer (layer 1) is varied periodically;

2 shows a schematic representation of an apparatus for producing a radiation energy converter preferred according to the invention with a stripe pattern, the position of the gas nozzles used being indicated relative to the strip (substrate) to be coated;

3 a shows a schematic illustration of an apparatus for producing a radiant energy converter with a checked pattern; and

3b is a perspective view of a radiant energy converter with a checked pattern preferred according to the invention.

In the present case, the term “patterned radiation energy converter” is intended to express that the radiation energy converters or absorbers are not homogeneously coated with a monochrome layer. Furthermore, the term “periodically” means that it occurs regularly or regularly recurring.

The surface of the substrate is at least partially, preferably completely, covered with one or more layers, the thickness and / or chemical composition of at least one of the layers changing periodically parallel to the surface of the substrate. In the following, the term “the varying layer” refers to the layer in which, according to the invention, the thickness and / or chemical composition changes periodically parallel to the surface of the substrate. This change preferably takes place at a distance perceptible to the eye. This does not mean a columnar microstructure as disclosed in WO-A-9 517 533. This columnar microstructure arises when a layer is grown on a substrate. Any irregularities that occur Layer thicknesses are in the micro range and are imperceptible to the eye. The thickness and / or chemical composition of the varying layer preferably changes at a periodic distance in the range from 1 to 40 cm, preferably from 3 to 9 cm, more preferably from 4 to 7 cm. Preferably at least 3, more preferably 10 to 30, even more occur. preferably 12 or 15, periodic changes in the thickness or chemical composition of the varying layer over a distance of one meter. In a preferred embodiment of the invention, the periodic change runs in a straight line, that is to say along or across the edges of the radiation energy converter, so that a stripe pattern is produced. However, it can also run in any other geometric shapes, for example checkered, honeycomb-shaped, diamond-shaped, circular, elliptical, helical or in the form of a Penrose pattern. An example of a radiation energy converter with a periodic change in the layer thickness is shown schematically in FIGS. 1c, 1d, 1f and 3b.

The periodic change in the thickness and / or chemical composition of the varying layer parallel to the surface of the substrate according to the invention gives the viewer the impression of a pattern, for example a strip or corrugated sheet, when the radiation energy converter is viewed from above. Checked, honeycomb or diamond pattern. This pattern distracts the viewer from errors in the coating of the radiation energy converter and thus enables a reduction in rejects. The human brain perceives structures through contrasts with the background. As a result of the pattern achieved according to the invention, the background is now structured on the radiation energy converter by a light-dark or a color contrast, so that the contrast to a defect on the surface of the radiation energy converter, such as a wave or bump, is flowing or changes arbitrarily. Since the contrast can no longer be clearly assigned, the detection of the error is made more difficult. In addition, architecturally interesting design effects can be achieved with the pattern. The radiation energy converter is advantageously the same at every point r of its surface in terms of layer thickness and chemical composition as at point r '

? ' = f + nι ä, + d, + n ₂ ä ₂ + d 2 »

where α _j and a _{2 are} fundamental translation vectors, d _j and d _{2 are} difference vectors and ni and n _{2 are} any integers, where:

| d | / | a | <25%.

The varying layer preferably contains at least one metal of the sub-group elements of the periodic table or a compound of the metal with nitrogen and / or oxygen and / or carbon or an alloy of the metal with one or more other metals. The metal is preferably a metal from group IVA, VA or VIA of the periodic table, particularly preferably a metal from group IVA of the periodic table, preferably titanium. In addition, a compound or alloy of titanium is preferred. Preferred compounds, in particular ceramic compounds have the formula MC _x N _y O _z, wherein M = Ti, Zr and / or Hf; x, y, z = 0 to 2.1 ;. x + y + z =? =, 0.01 to 4, in particular x + y + z = 0.01 to 2. The ratio of metal to carbon to nitrogen to oxygen is from 1: (0 to 2.1): ( 0 to 2.1): (0 to 2.1), preferably from 1: (0 to 1.0): (0 to 1.0): (0 to 2.0), particularly preferably from 1: (0 to 0.5): (0 to 0.5): (0 to 1.5) before. The above ratios relate to the number of particles or molar ratios. In addition to titanium, zirconium and / or hafnium, the varying layer can also contain niobium, tantalum, tungsten, molybdenum or their alloys as additional metals, which has an advantageous effect on the corrosion resistance of the layer. Furthermore, such alloys can have favorable mechanical properties. Materials such as those in WO-A-9 are also suitable as the material for the layer 726 488, DE-C-43 44 258 and DE-A-195 06 188 are described. A layer of titanium oxycarbonitride or titanium oxynitride, in particular of titanium oxycarbonitride, is particularly preferred.

The mean value of the thickness of the varying layer is preferably in the range from 10 to 10000 nm, preferably from 30 to 4000 nm, very preferably from 50 to 2000 nm. The deviation from the mean value by changing the layer thickness is in the range from (±) 1 to 60% , especially 2 to 30%, more preferably 3 to 15%. The layer thickness mentioned ensures that ^" bends of the radiation energy converter can be tolerated without damage.

A change in the chemical composition of the varying layer can be achieved by a person skilled in the art in the course of experiments which are customary in the art. In a preferred embodiment, this change in layers of metal compounds is achieved by changing the proportion of at least one component selected from nitrogen, oxygen and carbon. In another preferred embodiment, the proportion of the metals to one another is changed in layers of at least two different metals. If the chemical composition changes, the proportion of a component can vary by 1 to 100 atom%, preferably by 10 to 30 atom%, based on the metal.

In addition to the layer absorbing the radiation, the radiation energy converter can comprise one or more additional layers, preferably an additional layer. The radiation-absorbing layer can be coated with this additional layer or these additional layers. There is also the possibility that one or more of these additional layers lie between the substrate and the radiation absorbing layer. Of the additional layers, one or more of these layers can be optically transparent in one wavelength range or different wavelength ranges. Such layers consist of dielectric connections or glasses. In a particularly preferred embodiment of the invention, the varying layer is the radiation-absorbing layer, which is in particular designed as described above in the description of the varying layer.

In another preferred embodiment of the invention, the layer is designed as an anti-reflective layer, as described for example in Goetzberger, B. Voß, J. Knobloch; Solar energy: photovoltaics; Pp. 125-127; BG Teubner, Stuttgart 1994. Such a layer preferably consists of a silicon-containing glass, silicon dioxide or a dielectric, for example ZrO ₂ , HfO ₂ , Y ₂ O ₃ , TiO ₂ , SiO ₂ , Al ₂ O ₃ , SnO ₂ or Si ₃ N ₄ , in particular the antireflection layer consists of a silicon-containing glass, the Li ₂ O, B ₂ O ₃ , F, Na ₂ O, A1 ₂ 0 ₃ , SiO ₂ , K ₂ O, Fe ₂ O ₃ , Sb ₂ O ₃ and / or BaO contains. The layer thickness of the antireflection layer is preferably 70 to 120 nm. There is also the possibility that there is a periodic change in the layer thickness and / or chemical composition both in the radiation-absorbing layer and in the antireflection layer. In a preferred embodiment of the invention, the degree of solar absorption does not change by more than ± 2% as a result of the change in the layer thickness of the antireflection layer. The average degree of absorption, averaged over the entire area, is greater than 90%.

In a preferred embodiment of the invention, the varying layer of the radiation energy converter has been applied to a substrate by a vacuum coating process, for example PVD, PECVD or CVD, or by a wet chemical process. Suitable substrates are made of a metal, such as copper, aluminum, molybdenum, silver, gold, tungsten, nickel, chromium, zirconium, titanium, hafnium, tantalum, niobium, vanadium, iron or their alloys, such as, for example, stainless steel. Other suitable substrates consist of a ceramic, glass, plastic, carbon fiber-containing materials or composite materials. The substrate is preferably made of copper, aluminum or stainless steel. In a particularly preferred embodiment of the invention, the radiation energy converter is designed as a selective absorber. In particular, this is an absorber-reflector tandem with an additional anti-reflective layer.

To produce the radiation energy converter according to the invention, the varying layer is applied to the substrate by means of a vacuum coating process or a wet chemical process, with vacuum coating processes being particularly preferred. Appropriately, these are PVD (physical vapor depositioή), CVD (chemical vapor depositioή), PECVD (plasma enhanced chemical vapor depositioή) or ion plating, in particular PVD methods such as reactive vapor deposition, sputtering, reactive plasma processes, or the in Process described in DE-A-195 06 188 or WO-A-9 726 488. In general, the procedure for applying the layer to the substrate is as follows: First of all, the substrate is positioned in a vacuum chamber and heated to 20 to 500 ° C., preferably to 100 to 400 ° C., particularly preferably to 200 to 350 ° C. For coating in the chamber by means of evaporation, preferably electron beam evaporation, at a vacuum of 10 ^"5 to 10 ^{" 2} mbar, preferably from 10 ^"4 to 10 ^{" 2} mbar, particularly preferably from 10 ^"4 to 5T0 ^{" 3} mbar Metal or the alloy as defined above evaporates. If metal compounds are to be applied, appropriate process gases, such as oxygen, nitrogen and / or carbon-containing gases, such as, for example, carbon dioxide, methane or ethyne, are additionally introduced into the vacuum chamber.

In a preferred embodiment of the invention, a reactive PVD method is used, in which at least one metal is evaporated by means of an evaporator source. Depending on the material of the varying layer, at least one process gas is expediently introduced, which reacts with the evaporated metal on the substrate to form the compound forming the varying layer. To achieve the change in thickness according to the invention and / or chemical composition of the varying layer, different procedures are possible, which are described in more detail below.

In a preferred embodiment, the substrate is moved relative to at least one evaporator source. In this case, at least one mask is introduced between at least one evaporator source and the substrate, the geometric arrangement of which may be changed periodically during the application process. The mask can be, for example, a comb-shaped or rake-shaped mask or a wavy mask. FIG. 1 a shows schematically the implementation of a method for producing a stripe pattern by changing the layer thickness using a mask. By inserting a comb-shaped mask (basic comb) between the evaporators and the strip (substrate) to be coated moving at a constant speed, the length of the distance on which evaporated material condenses on the strip is varied. The mask can be moved periodically across the bandwidth. In the case of a suitable mask, the width of the tines and the distances between them are in the range from 1 to 40 cm, preferably from 3 to 9 cm. As shown in FIG. 1b, the maximum coating width L ₂ on which evaporator material can condense on the belt without a mask is reduced by the mask with tines of length Li by a maximum of 60%, preferably by 1 to 20%. Depending on the evaporation characteristics of the evaporators used, the layer thickness at the points at which the mask acts is reduced by the amount by which the maximum vaporisable distance is reduced. FIG. 1 c shows a cross section through a strip coated according to FIG. 1 a, which represents a preferred radiation energy converter with a radiation-absorbing layer 1 and an antireflection layer 2. While layer 1 has a constant thickness, the thickness of layer 2 changes by 1 to 60%. Depending on the distance h between the mask and the strip to be coated, a smooth transition between the strips can also be produced. The larger the distance, the softer the transition. Thus, in the radiation energy converter of FIG. 1d, the thickness of the layer 2 changes continuously, so that there is a smooth transition in color impression or brightness. This effect can also be achieved by using a wavy mask, as shown in Fig. Le.

In a preferred embodiment of the invention, an antireflection layer is applied as a varying layer to a radiation-absorbing layer, the mask being introduced only when this layer is applied. As a result, the wavelength at which the maximum reflection reduction occurs occurs in the shorter-wave range, so that a different color impression is created. This is described in detail in WO-A-9 726 488. In this way, a radiation energy converter is produced which shows a stripe pattern for the eye along the direction of movement of the substrate. For example, stripes of alternating blue (minimum reflection at 600 nm) and light blue (minimum reflection at 650 nm) or, for example, blue (minimum reflection at 600 nm) and red-violet (minimum reflection at 550 nm) can be produced with a selective absorber.

In a particularly preferred embodiment, the substrate consists of copper or aluminum with a thickness of 0.12 to 0.6 mm, the absorber layer consists of a titanium carboxynitride layer or titanium oxynitride layer with a thickness of 30 to 120 nm and the antireflection layer consists of SiO ₂ with a thickness of 30 to 200 nm. Both the absorber layer and the antireflection layer are applied in a roll coating vapor deposition process using electron beam evaporators at a substrate temperature between 20 ° C. and 400 ° C. The distance between the evaporators and the substrate is between 0.3 m and 0.9 m. The length L _{2 of} the maximum coating area (see. Fig. Lb or le) is between 0.3 m and 2 m. The ratio of the tine length Li to the length L of the coating area Lι / L ₂ (see. Fig. Lb or le) is between 10 and 40%. The distance h between the mask and the substrate is between 0.01 m and 0.2 m. When using a mask with teeth of different lengths, stripes with more than 2 different colors can also be created.

In a further preferred embodiment, it is not the layer thickness of the antireflection layer that is periodically varied, but rather the layer thickness of the absorber layer, as shown in FIG. 1f using layer 1 (absorber layer) and layer 2 (antireflection layer). The mask is only introduced when the absorber layer is applied , Stripes of different colors can be produced from this, since the optical system of the reflector-absorber tandem varies here periodically.

In a further preferred embodiment, both the layer thickness of the antireflection layer and the absorber layer are varied, the variation of the layer thickness also being able to have different periods and phase positions.

In further preferred embodiments of the invention, the desired change in the layer thickness and / or chemical composition is achieved via the geometric arrangement of at least two evaporator sources, the geometric arrangement of which can be changed periodically if necessary. In particular, the evaporation rate of at least one evaporated metal can also be changed periodically. In an alternative preferred embodiment of the invention, in which at least one process gas is introduced, the desired change in the layer thickness and / or chemical composition of the varying layer is achieved via the geometrical arrangement of at least two gas nozzles for introducing process gases, the geometrical arrangement thereof possibly again can be changed periodically. There is also the possibility that the gas flow of at least one process gas is changed periodically or that the gas composition is changed periodically when at least two different process gases are introduced. In this way, a change in the chemical composition of the varying layer is achieved. FIG. 2 shows a further preferred exemplary embodiment, in which a radiation energy converter with a stripe pattern is generated via periodically attached gas nozzles. From Rother / Netter, Plasma Coating Processes and Hard Material Layers, p. 188, Leipzig 1992, it is known that the color impression of titanium carbonitride layers depends on the composition of the layer as follows:

2, a rake consisting of gas nozzles is introduced between the substrate and the evaporators, in which nitrogen (gas 1) and methane (gas 2) are alternately introduced from one nozzle. It is also possible to introduce different gas mixtures. As a result, the gas distribution over the substrate changes periodically and when reacting with the vaporized metal, compounds of different chemical compositions are formed, which gives the impression of a stripe pattern when viewed from above. Here, e.g. create a pattern of silver and gold stripes.

3 a shows an apparatus for producing a radiant energy converter with a check pattern by means of masks. As in FIG. 1a, a comb-shaped mask is used in FIG. 3a. In addition, perpendicular to the prongs of the Comb metal strip moves at the same speed as the tape (substrate) to be coated. On the way back, the metal strips fold down due to the force of gravity so that they do not influence the vapor deposition. This component is therefore also known as a folding comb. If the path of the metal strips is the same as the length of the teeth of the comb, a check pattern is created with only two shades of color, cf. Fig. 3b. If, on the other hand, the path is different from that of the teeth of the comb, a pattern with three different color impressions is created. With the help of a folding comb, it is also possible to apply any pattern to the substrate, such as lettering. An opening in the shape of the desired pattern is made in the flaps.

The method according to the invention is preferably carried out as an in-line or roll-coating method.

The radiation energy converters according to the invention are used in solar collectors and / or as a decorative layer. They are particularly suitable in solar collectors, for example as roof and facade cladding for houses and other construction objects, in particular high-rise buildings and office buildings. The radiation energy converter according to the invention can also be integrated in a window element, which can be strung together or combined over a large area. It can also be used in public places or in swimming pools. The desired decorative effect is combined with the simultaneous generation of energy. The radiation energy converter according to the invention can of course be used in any type of collector, in particular for vacuum, flat or tube collectors.

In contrast to the CH patent 581 812, in which there are elevations in the substrate, according to the invention there are changes in the thickness or composition of a layer, that is - in the sense of CH 581 812 - changes in the thickness or chemical composition a layer of the solar-irradiable collector surface.

Claims

claims

1. Patterned radiation energy converter for converting radiation energy into thermal energy, which has a substrate which is at least partially coated with one or more layers, at least one of which is designed as a radiation-absorbing layer, characterized in that the thickness and / or the chemical composition of at least one of the layers changes periodically parallel to the surface of the substrate.

2. Radiant energy converter according to claim 1, characterized in that the thickness and / or chemical composition of the at least one layer changes in a periodic distance in the range of 1 to 40 cm.

3. Radiant energy converter according to claim 1 or 2, characterized in that it is the same at every point f of its surface with respect to layer thickness and chemical composition as at point r '

r '= r + m a. + d, + n ₂ a ₂ + d 2 '

where aj and a are ₂ fundamental translation vectors, d, and d are ₂ difference vectors, and ni and n _{2 are} any integers, where: jd | / | a | <25%.

4. Radiant energy converter according to one of claims 1 to 3, characterized in that the at least one layer is an anti-reflective layer.

5. Radiant energy converter according to claim 4, characterized in that the anti-reflective layer made of a silicon-containing glass, silicon dioxide or a dielectric selected from ZrO ₂ , HfO ₂ , Y ₂ O ₃ , TiO ₂ , SiO ₂ , Al ₂ O ₃ , SnO ₂ or Si ₃ N consists, in particular, of a silicon-containing glass which contains Li ₂ O, B ₂ O ₃ , F, Na ₂ O, Al ₂ O ₃ , SiO ₂ , K ₂ O, Fe ₂ O ₃ , Sb ₂ O ₃ and / or BaO contains.

6. Radiant energy converter according to one of claims 1 to 3, characterized in that the at least one layer is a radiation absorbing layer.

7. Radiant energy converter according to claim 6, characterized in that the radiation absorbing layer contains a compound between one or more metals of the sub-group elements of the periodic table with nitrogen and / or oxygen and / or carbon, in particular that it has titanium oxycarbonitride or titanium oxynitride.

8. Radiant energy converter according to one of the preceding claims, characterized in that the mean value of the thickness of the at least one layer is in the range from 10 to 10000 nm, the deviation from the mean value in the range of (±) 1 for the periodic change up to 60%.

9. Radiant energy converter according to one of the preceding claims, characterized in that one or more of the layers by a vacuum coating process or wet chemical process on the

Substrate have been applied.

10. Radiant energy converter according to claim 9, characterized in that the substrate consists of a metal, a metal alloy, a ceramic, glass, plastic, a carbon fiber-containing material or a composite material.

11. Radiant energy converter according to one of the preceding claims, characterized in that it is designed as a selective absorber.

12. A method for producing a radiation energy converter according to one of the preceding claims, characterized in that one or more layers, at least one of which is formed as a radiation-absorbing layer, are applied to a substrate by means of a vacuum coating method or wet-chemical method be that the layer thickness and / or the chemical composition of at least one of the layers changes periodically parallel to the surface of the substrate.

13. The method according to claim 12, characterized in that a reactive PVD method is used as the vacuum coating method, in which at least one metal is evaporated by means of an evaporator source.

14. The method according to claim 13, characterized in that the substrate is moved relative to at least one of the evaporator sources.

15. The method according to claim 13 or 14, characterized in that at least one mask is introduced between at least one of the evaporator sources and the substrate, the geometric arrangement of which may be changed periodically.

16. The method according to any one of claims 13 to 15, characterized in that the periodic change in the layer thickness and / or chemical composition is achieved via the geometric arrangement of at least two evaporator sources, the geometric arrangement of which may be changed periodically.

17. The method according to any one of claims 13 to 16, characterized in that the evaporation rate of at least one evaporated metal is changed periodically.

18. The method according to any one of claims 13 to 17, characterized in that at least one process gas is introduced which reacts with the evaporated metal on the substrate to form the compound forming the layer, the periodic change in the layer thickness and / or chemical composition Is achieved via the geometric arrangement of at least two gas nozzles for introducing process gases, the geometric arrangement of which may be changed periodically.

19. The method according to any one of claims 13 to 18, characterized in that at least one process gas is introduced, which is vaporized with the

Metal on the substrate reacts to form the layer-forming compound, the gas flow of at least one process gas being changed periodically or the gas composition being changed periodically when at least two different process gases are introduced.

20. Use of a radiation energy converter according to one of claims 1 to 11 or produced according to one of claims 12 to 19, in a solar collector and / or as a decorative layer.