WO2017202918A1

WO2017202918A1 - Reflector device

Info

Publication number: WO2017202918A1
Application number: PCT/EP2017/062553
Authority: WO
Inventors: Antoine Bittar
Original assignee: Shimmer Gmbh
Priority date: 2016-05-25
Filing date: 2017-05-24
Publication date: 2017-11-30
Also published as: CN109154453A

Abstract

The present invention provides a reflector device carrier structure for carrying on its first side (F) a reflective surface layer, comprising a back plate (42), a body part (44) positioned on the back plate (42) and having at least two stacked layers (46a-46b), each of which formed by a hollow structure made of a construction material, wherein adjacent stacked layers (46a-46b) are separated by a sheet layer (48), wherein of the at least two stacked layers (46a-46b) pairs of adjacent layers differ in at least one parameter of their hollow structures, such as orientation. The invention further provides reflector devices as well as methods for producing them.

Description

Reflector Device

Description

The present invention generally relates to improvements in reflector device carrier structures, reflector devices and methods for producing the same.

Solar reflectors are used for a variety of purposes and in particular in solar dish systems and central tower systems of concentrating solar power plants. For example, from document US 4 172 443 a concentrating solar power plant is known which essentially is a distributed solar collector with a central radiation receiver and a plurality of reflectors mounted on articulated structures arranged over a large area below and around the receiver.

Such central tower systems generally comprise a tower structure more or less centrally situated, atop which a receiver is positioned and around which individual articulate d reflectors are arranged in order to form a reflector field which collects the sun's irradiance from a large area and concentrates it on to the central receiver. The articulated reflectors are often referred to as heliostats which is a combination of the Greek word for "sun" and the term "stationary". Solar irradiance concentrated on the receiver is substantially absorbed by the receiver and converted into heat which is then transported away from the receiver for further use or conversion.

Alternatively, instead of a receiver sitting atop a tower structure, a secondary reflector may be positioned thereon to redirect the concentrated irradiance to a receiver for instance placed on the ground below the tower structure.

In all cases, an essential component of these solar concentrating systems is the articulated reflector mentioned above which is arranged such that it tracks the motion of the sun so that its rays are continuously reflected towards the receiver or the secondary reflector atop the tower structure. Dishes of such solar dish systems and heliostats are, however, also applicable in smaller installations such as solar cookers. Historically, the tracking of the motion of the sun has been performed by hand or complex mechanical devices, whereas nowadays dishes and heliostats are usually positioned by computer controlled motors in order to be turned into correct alignment with the sun and the receiver.

Heliostats are known in a variety of forms wherein essential features of all of those forms are a foundation and/or a pedestal which are arranged to penetrate the ground or rest upon it, drive mechanisms for movement in two or more axial directions, a structural frame driven by these drive

mechanisms and a mirror element or a plurality of mirror elements attached to the structural frame via connectors.

Such heliostats are known with a variety of types of mirror elements as described in the following: firstly, heliostat reflectors have been constructed with standard sheets of back silvered glass mirrors attached to steel frames through adjustable lugs glued to the back of the glass mirror elements. Such reflector systems are used in parabolic trough solar plants and in some central tower heliostats and are often referred to as bare mirror elements. They are comparatively light but do not assure sufficient rigidity and are thus limited to small sizes which are defined by the available types of glass and are therefore not scalable to large reflector sizes. They also present a safety hazard on breaking as the mirrors are not made of toughened glass. Field assembly and canting into a steel frame are required to adjust the position, orientation and optical performance of the mirror elements.

Secondly, segmented mirror elements are known to be used in heliostat reflectors being assembled from segments of mirrors. These segments are square, rectangular, triangular or of other shapes. Some segments may be back silvered glass elements. They are assembled, several at a time, onto steel frames using adjustable lugs to form each heliostat reflector. Alternatively, these segments may be glued onto laminated metallic sheets which are then attached, once again several at a time for each heliostat, through lugs to a steel frame to define an optical surface shape. Their shape is usually an optically preferred shape such as a flat or parabolic shape.

Though heliostats are mentioned as the articulated reflector, all statements made herein and in the description of the present invention are applicable to dual axis reflectors in the same manner.

These systems require canting and assembly of individual mirror elements to a steel frame that is then attached to a pedestal structure. Inherent rigidity is often ensured for the individual segments, but overall rigidity of the heliostat relies on the sizable and heavy metal structure and adjustable lugs to maintain the segments rigidly connected with respect to each other and to comply with the preferred shape. Thus, said segmented mirror elements are heavy and expensive.

There also diaphragm mirror elements known for the use in heliostats and parabolic dishes have been made by a steel diaphragm having an evacuable back structure onto the front of which are placed back silvered glass mirrors. Such diaphragm mirror elements have been made in large sizes and may not require lugs due to the direct gluing of mirror segments to the steel membrane. The preferred optical shape is obtained by creating a pressure differential between the front and the rear of the metallic membrane. These diaphragm mirror elements are however not easily shapeable and

cumbersome concerning their production and maintenance.

Another known form of heliostat reflectors comprises foam backed mirror elements which are made of thin highly reflective back silvered glass mirrors integrated into foam and steel sandwich backings. These facets achieve a higher reflectivity due to the employed thin glass as the reflecting element. They have been produced in sizes up to 8 m². However, no larger facets or high curvature facets have been possible due to various reasons including non-uniformity of the foam materials, issues with thermal extension properties and the need for substantial foam thicknesses and steel structural elements embedded in the foam to achieve the desired rigidity. Large area heliostats using these facets therefore need a more substantial steel frame and fixtures to hold several facets in a single heliostat structure thus compromising many of the structural advantages of said construction.

These steel frames and fixtures generally lead to heavy pedestals and foundations as support for the mobile mirror assemblies and therefore more costly heliostats as well as extensive field assembly and canting work in order to achieve the optical quality are required in the solar field. The need for further structural frame and canting mechanisms also adds to the distortions experienced during longterm use of moving heliostats.

Furthermore, the inevitable spacing between facets on the heliostat frame leads to reduced areal efficiency of the individual heliostats and increased blocking and shading losses in the heliostat field for a given reflective area in the field.

Lastly, glass-glass mirror elements with foam interlayers are known as a variation of the foam sandwich mirrors. In this design, the back plate used for the foam sandwich is replaced by a glass plate and the foam is selected according to thermal compatibility with both the front and back glass plates. Although these facets can achieve relatively good optical quality and are able to take high radii of curvature, their size has been limited to about 3 m ² implying that several facets are needed in order to manufacture larger heliostats. This again leads to the requirement of a steel frame, fixing lugs and complex assembly and canting work in the field during construction as well as reduced areal efficiency due to blocking and shading of the assembled heliostats.

To summarize, despite various different known types of mirror elements in heliostats, each one of the known construction forms has one or more of the following issues: a lack of rigidity, size constraints, low reflectance because of thicker glass, safety hazards due to shattering in a dangerous manner, requirement of multiple metallic layers with thermal matching issues and increased weight, insufficient curvature radii and/or high requirements in construction and maintenance.

The present invention aims at overcoming these issues and providing an arbitrarily sized, highly rigid and light-weight reflector device carrier structure as well as reflector device inherently achieving high reflectivity, requiring no external frame structure, no adjustable lugs and no field-based optical adjustment during mounting on a heliostat pedestal of reduced size.

Therefore, in a first aspect of the invention, a reflector device carrier structure for carrying on its first side a reflective surface layer is presented, comprising a back plate, a body part positioned on the back plate and having at least two stacked layers, each of which formed by a hollow structure made of a construction material, wherein adjacent stacked layers are separated by a sheet layer, wherein of the at least two stacked layers pairs of adjacent layers differ in at least one parameter of their hollow structures, such as the orientation.

This kind of construction, colloquially referred to as a sandwich structure due to its stacking of layers of different kinds, allows for the manufacturing of large sized reflector devices by suitably adjusting the properties of the stacked layers and the hollow structures. Consequently, the properties of the reflector device carrier structure can be fine-tuned and adjusted according to the particular requirements of individual reflector devices. Thus, the invention circumvents several of the disadvantages of the existing facet based heliostats and glass heliostats.

In particular, the invention can provide reflectors with a large surface area which can be constructed such that the full area is a reflecting area with high reflectivity. This lead to the highest possible heliostat areal efficiency. Also, due to the use of hollow structures in the body part, a lighter weight of the reflector device can be achieved while circumventing the uniformity issues of the known constructions discussed above. By employing suitable hollow structures in the body part, such as for example honeycomb structures, the rigidity of the construction can be optimized, which is even further

accentuated by the provision of adjacent layers differing in at least one parameter of their hollow structures such as the orientation. Further parameters of the hollow structures besides their orientations may for example be their thicknesses, their heights, their physical and mechanical properties and the ratio between material and cavities.

Also, due to the possible monolithic nature of the reflector devices using reflector device carrier structures according to the present invention, large reflective areas without "dead spaces" between mirror segments and reduced blocking and shading losses in the field can be constructed.

Alternatively or in addition to honeycomb structures, at least one of the stacked layers may comprise a tube structure, wherein preferably the longitudinal axes of the tubes are aligned with the stacking direction of the stacked layers and/or perpendicular to the back plate. It is, however, also possible to arrange tubes in layers in which the axes of the tubes are parallel to the plane of the back plate.

For the sheet layer, very thin sheets, for example made from plastic material, can be used in order to improve the stability of the body part of the reflector device carrier structure while maintaining a low weight. Furthermore, in the case of honeycomb structures and/or tube structures, the ratio of the wall thickness of the structure and the cavities provided between the walls can be adjusted depending on the thickness and stiffness of the sheet layers such that the rigidity of the structure can be maximized and weight can be minimized within the requirement of the particular reflector device

parameters. Due to the possible uniform rigidity across the entire structure which can be achieved by suitably choosing the above discussed parameters of the hollow structures and the sheet layers, thin glass mirrors can be used for the reflective surface layer of the reflector device which inherently leads to higher reflectance values which in turn leads to better beam quality, lighter weight and reduced costs.

In a second aspect of the invention, which may be implemented

independently or in combination with the first aspect, a reflector device carrier structure is provided, which is adapted to carry on its first side a reflective surface layer and comprising a back plate, a body part positioned on the back plate and having at least one layer comprising a tube structure, wherein the longitudinal axes of the tubes are perpendicular to at least one of the back plate and the reflective surface layer, wherein the tubes of the at least one layer, preferably the layer adjacent to the first side of the reflector device carrier structure, are sized and arranged such that the first side of the reflector device carrier structure has a predetermined curvature.

According to this second aspect of the invention, by providing a single layer of tubes with different lengths in a predetermined arrangement, which obviously can be combined with the sandwich structure of the first aspect of the invention, in a very straightforward way a reflector device with a predetermined surface curvature can be achieved which furthermore exhibits all the advantages discussed above in the context of the first aspect of the invention such as uniform rigidity, light weight and a possible large continuous reflective surface.

In particular, the actual curvature of the first side of the reflector device carrier structure according to the present invention can be chosen almost arbitrarily, and can in particular have different predetermined curvatures along two orthogonal directions. ln order to reduce their environmental footprints, reflector device carrier structures, both according to the first and second aspect of the present invention, may comprise recycled plastics and/or recyclable plastics and/or biodegradable material.

There may also be provided on the first side of the reflector device carrier structure, both according to the first and second aspect of the invention, a plate layer, preferably a continuous plastic sheet. Onto said plate layer, the actual reflector surface layer may then be applied.

In a variant of the first aspect of the invention having the same advantages over the prior art, it also provides a reflector device carrier structure adapted to carry on its first side a reflective surface layer, comprising a back plate and a body part positioned on the back plate and separating the back plate from the reflective surface, wherein the body part is made of a discrete array or a connected network of essentially hollow support structures, oriented with at least one parameter of their hollow structures either parallel or perpendicular to the back plate.

In a third aspect, the present invention relates to a method for producing a reflector device carrier structure adapted to carry on its first side a reflective surface layer according to the second aspect of the invention, comprising providing a back plate, forming a body part by arranging one layer comprising a tube structure or at least two stacked layers of which at least one comprises a tube structure on the back plate, wherein at least one layer comprising a tube structure is formed by providing tube sections with predetermined lengths and arranging them on the back plate in such a manner that the first side of the reflector device carrier structure has a predetermined curvature.

Said method can be automated to a high degree using known computer systems which provide for the automated arrangement and positioning of the respective tube sections in a suitable manner. In particular, a tube section with predetermined length may be provided by cutting one or more tubes into tube sections of the required length.

In a fourth aspect, the present invention relates to a reflector device comprising a single continuous carrier element, if desired embodied by a reflector device carrier structure according to the first and/or second aspect of the invention and/or produced by a method according to the third aspect of the invention, adapted to carry on its first side a reflective surface layer and on its second side having a back plate, and a reflective surface layer attached to the carrier element and having a predetermined curvature, wherein the reflective surface layer consists of at least two mirror segments which are arranged on the first side of the carrier element such that a single continuous reflective surface is formed which is shaped along two

orthogonal directions according a desired curvature of the reflective surface layer.

Due to the reflective surface being continuous and also employing a single continuous carrier element, many of the disadvantages mentioned above in the context of known reflector devices are overcome, such as gaps in the reflective area and blocking and shading losses.

The mirror segments may in general be arbitrarily formed, it may also sometimes be advantageous if no more than two segments meet at one point, in order to facilitate the continuous nature of the reflective surface. Therefore, the mirror segments may be formed as parallel bands spanning over the first side of the reflector device which are positioned side-by-side.

A reflector device according to the invention may be provided with a non- axisymmetric reflective surface layer and/or a reflective surface layer which has different curvatures along different directions which allows for providing reflector devices for all kinds of applications.

In a fifth aspect, the invention relates to a method for producing a reflector device, comprising providing a carrier structure adapted to carry on its first side a reflective surface layer and on its second side having a back plate, if desired the reflector device being according to the fourth aspect of the invention, applying an intermediate layer on the first side of the carrier structure, disposing at least one mirror segment on the intermediate layer, exerting pressure on the least one mirror segment such that the at least one mirror segment is being shaped along two orthogonal directions in order to achieve a desired curvature of the reflective surface layer formed by the at least one mirror segment.

By shaping the at least one mirror segment while it is already disposed on the intermediate layer and thus in contact with the carrier structure, it can be ensured that the desired curvature of the reflective surface can be achieved with the highest precision which also allows for rather complex surface curvatures.

To further facilitate the shaping of the mirror segments to their

predetermined curvatures, the intermediate layer may be applied on the first side of the carrier structure in non-uniform thickness which may or may not be uniform with the desired curvature of the reflective surface, depending on the particularities of the actual production process as well as the desired shape of the reflector device.

The intermediate layer may further also have adhesive properties and provide the attachment of the at least one mirror segment to the carrier structure.

For exerting pressure on the at least one mirror segment at least one roller and/or at least one inflatable bag may be used.

Depending on the material used for the at least one mirror segment, it may be beneficial to perform the shaping of the at least one mirror segment at ambient temperature or heat the mirror segment prior to or during it being shaped.

Further properties and advantages of the present invention will in the following be presented by the description of embodiments shown in the accompanied drawings, which show:

Figure 1 A: multiple layers of a first embodiments of a reflective device carrier structure according to the invention in an exploded view;

Figure 1 B: a variation of the first embodiment of a carrier structure shown in figure 1A;

Figure 2A: a second embodiment of a reflector device carrier structure according to the invention;

Figure 2B: a section through the carrier structure of figure 2A;

Figure 2C: a plan view of the structure of figure 2A without sheet layers;

Figure 3A: a third embodiment of a reflector device carrier structure

according to the invention;

Figure 3B: a variation of the third embodiment of figure 3A shown in section;

Figure 4: a fourth embodiment of a reflector device carrier structure according to the invention in exploded view;

Figure 5A: a first embodiment of a reflector device according to the

invention;

Figure 5B: a section through the device of figure 5A; Figure 6A: a section through a second embodiment of a reflector device according to the invention before shaping of the mirror segments; the device of figure 6A after shaping of the mirror segments; a third embodiment of a reflector device according to the invention;

Figure 7B: the reflector device of figure 7A before shaping of mirror

segments; and

Figure 7C: the reflector device of figure 7A after shaping of mirror

segments.

In figure 1A a first embodiment of a reflector device carrier structure according to the invention is denoted with reference numeral 10 and shown in exploded view. It comprises a back plate 12 and a body part 14 positioned on the back plate. The back plate 12 may be made of suitable materials such as a solid metal plate and may consist of several connected sections or may be manufactured in one piece. It may further comprise on its side opposed to the body part 14 connecting means for installing the reflective device carrier structure 10 on a movable frame or similar devices according to its designated use.

The body part 14 in turn comprises three stacked layers 16a, 16b and 16c made of tubes between which sheet layers 18 are interposed. The

longitudinal axes of the tubes are aligned with the stacking direction of the stacked layers 16a-16c of body part 14 and are thus perpendicular to the back plate 12. Within a single layer 16, the tubes are arranged in a regular pattern equidistant to each other in two dimensions. In other embodiments of the invention, the spacing between the tubes may however also vary within a single layer or among different layers. It has to be noted that the tubes of neighboring stacked layers 16a-16c are offset in two dimensions such that the longitudinal axes of the tubes of neighboring layers 16a-16c are parallel but not aligned with one another.

The tubes of the stacked layers 16a-16c may be solid or hollow and may be formed from a wide range of construction materials such as recycled or recyclable plastics. The diameters of the tubes as well as their spacing can be chosen together with the construction material according to the desired rigidity and weight of the reflector device carrier structure 10.

On top of the body part 14 a first side F of the reflector device carrier structure is formed as a continuous plane layer, on which the actual reflective surface layer can be positioned. The sheet layers 18 as well as the plane layer of the first side F may be made of thin plastic or metal layers or foils, wherein the sheet layers 18 and the plane layer of the first side F may be of the same material and thickness or may differ in at least one of these parameters.

Figure 1 B shows a variation of the first embodiment of a reflector device carrier structure according to the invention, denoted with the reference numeral 10'. Similar to the structure shown in figure 1A, the structure 10' shown in figure 1 B also comprises a back plate 12', a body part 14', stacked layers 16a', 16b' and 16c' with interposed sheet layers 18' as well as a first side F on which a reflective surface layer can be carried.

The difference between the carrier structure 10' of figure 1 B compared with the structure 10 of figure 1A is that the tubes within the stacked layers 16a'- 16c' are not only offset from one another in two dimensions as shown in figure 1 A, but they also differ in length. Specifically, the tubes used in the middle layer 16b' are longer than the tubes used in the lower and upper layers 16a' and 16c'. Thus, the thickness I _a of the bottom layer 16a' and the thickness l_c of the top layer 16c' are smaller than the thickness I _b of the middle layer 16b'. Through this difference in the lengths of the tubes and thus the thicknesses of the respective stacked layers, a further parameter is provided for the adjustment of the rigidity and weight of the reflector device carrier structure 10'.

Another parameter which may be adjusted when hollow tubes are used for the stacked layers 16a-16c and 16a'-16c' respectively are their wall thicknesses, i.e. the ratio of material to cavities within the respective layers. Said ratio may be identical for different layers but does not necessarily have to be.

Figures 2A to 2C show a second embodiment of a reflector device carrier structure according to the invention generally denoted with reference numeral 20. Similar to the carrier structures according to the first

embodiment and the variation of the first embodiment 10 and 10', said second embodiment of a reflector device carrier structure 20 comprises a back plate 22, a body part 24, stacked layers 26a-26c, sheet layers 28 and a first side F adapted to carry a reflective surface layer.

Compared to the first embodiment shown in figure 1A and the variation of the first embodiment shown in figure 1 B, the diameters of the tubes used in the stacked layers 26a-26c is larger in carrier structure 20 shown in figures 2A-2C and the spacing between the individual tubes is smaller and may be zero.

As can be seen in figure 2B, the wall thickness of the tubes as well as their spacing are chosen relatively small such that the cavities inside the hollow tubes are much larger than the cavities between the individual tubes. As can best be seen in figure 2C, which shows a top view of the structure 20 with omitted sheet layers 28 for illustrative purposes, the tubes of the individual stacked layers 26a-26c are offset in both dimensions X and Y by about half the diameter of the individual tubes thus forming the regular pattern shown in figure 2C. With this arrangement, higher rigidity of the reflector device carrier structure 20 can be achieved while maintaining a low weight due to the favorable ratio between material and cavities within the stacked layers 26a-26c owing to the small wall thickness of the individual tubes.

A third embodiment of a reflector device carrier structure 30 shown in figure 3A does not rely on vertical tubes within the stacked layers, but on a saw tooth structure. Once again, said carrier structure 30 comprises a back plate 32, a body 34, a plurality of stacked layers 36a-36c comprising the above- mentioned hollow saw tooth structure, between which sheet layers 38 are interposed and a first side F arranged to carry a reflective surface layer.

As can be seen in figure 3A, the stacked layers are rotated relative to their respective neighboring layers by 90°. With this arrangement, the rigidity of the reflector device carrier structure 30 can be made substantially uniform in both directions X and Y. The hollow saw tooth structure itself can for example be made from plastic or metal sheets which are folded into said saw tooth pattern. Once again, the ratio of material to cavities within the respective layers 36a-36c is relatively small, so that light weight of the reflector device carrier structure 30 can be ensured.

Figure 3B shows a variation of the carrier structure 30 of figure 3A, denoted with the reference numeral 30'. It differs from the carrier structure 30 shown in figure 3A in that there is no saw tooth pattern used in the stacked layers 36a'-36c', but parallel walls which are arranged perpendicular to both the back plate 32' and the first side F. Similar to the stacked layers 36a-36c of figure 3A, neighboring layers 36a'-36c' in carrier structure 30' are rotated by an angle of 90°, such that in the sectional view of figure 3B, the section through the middle layer 36b' is parallel to its walls and in the upper and lower layers 36a' and 36c' the section is perpendicular to the parallel walls.

In figure 4, a fourth embodiment of a reflector device carrier structure 40 according to the invention is shown, once again comprising a back plate 42, a body part 44, stacked layers of hollow structures 46a and 46b, a sheet layer 48 and a first side F adapted to carry a reflective surface layer.

In the fourth embodiment of a reflector device carrier structure 40 a honeycomb structure is used in the stacked layers 46a and 46b of the body part 44. The honeycombs themselves are hollow and form a pattern with a high degree of symmetry. Consequently, the hollow structure of the layers 46a and 46b consists of the walls of the honeycombs and the cavities formed inside them. The two individual stacked layers 46a and 46b are offset relative to one another along the directions X and Y in a similar way as the tubes of a reflector device carrier structure 20 according to the second embodiment shown in figures 2A to 2C by half the diameter of their cavities.

Such a stacked honeycomb structure through its high degree of symmetry provides uniform properties of the reflector device carrier structure 40 together with high rigidity and a low weight.

It has to be noted that the embodiments of figures 1 A to 4 can be varied in a number of ways. For example, the number of stacked layers of their body parts can be chosen almost arbitrarily. In the case of the saw tooth or parallel wall hollow structures of figures 3A and 3B it might be beneficial to chose an even number of stacked layers if the hollow structures of the layers are rotated by 90° with respect to one another. On the other hand, other angles between the structures may be chosen, such as 60° or 45°. Also, different hollow structures might be combined in a single carrier structure, such as alternating layers of tubes and honeycombs. Furthermore, various known techniques can be used for joining the different stacked layers with the sheet layers and with the base plate, such as gluing and welding, depending on the used materials.

Figures 5A and 5B show a first embodiment of a reflector device according to the invention denoted with reference numeral 60, in which a reflector device carrier structure 50 similar to the first to fourth embodiments of a reflector device carrier structure presented above is used. It is for reasons of presentability that the stacked layers of the carrier structure 50 are not shown offset relative to one another, yet the carrier structure 50 could as well be provided by one of those presented in figures 1 A to 4.

On the first side F of the carrier structure 50, a reflective surface is formed by multiple mirror segments 62a, 62b and 62c. These mirror segments are shaped along the two directions X and Y and positioned on the first side F of the monolithic carrier structure 50 in such a way that they form a single continuous reflective surface. The individual mirror segments 62a-62c are formed as strips, so there is no occurrence on the continuous reflective surface of more than two of them being adjacent in a single point, which facilitates the forming of the single continuous reflector surface during the shaping of the individual segments 62a-62c. As can be seen in figure 5B, the mirror segment 62c is bent upwards from the carrier structure 50 on its outer edge and thus not in contact with the carrier structure 50 in its entirety.

In figures 6A and 6B a second embodiment of a reflector device 70 is shown, which comprises the same carrier structure 50 as the embodiment shown in figures 5A and 5B. The section of figure 6A is made along the direction Y and thus parallel to the contact surface of the individual mirror segments 72a and 72b which are positioned side-by-side in a similar way as the mirror segments 62a-62c in figure 5A. Thus, only a first mirror segment 72a is visible in figure 6A. Between said mirror segment 72a and the body part 50, there is provided an intermediate layer 74. Said intermediate layer 74 exhibits a concave curvature. It has to be noted that in figure 6A, the mirror segment 72a is not yet shaped into its desired curvature but is still plane.

Figure 6B shows the reflector device 70 of figure 6A in a section along the X-direction perpendicular to the contact surfaces between the mirror segments 72a and 72b. Furthermore, figure 6B shows the reflector device 70 after the shaping of said mirror segments 72a and 72b into a concave or parabolic shape. It can be seen that the mirror segments 72a and 72b during their shaping have been adapted in their curvature to the intermediate layer 74. Said intermediate layer 74 can also have adhesive properties and thus provide the attachment of the mirror segments 72a and 72b to the body part 50.

Finally, in figures 7A to 7C a third embodiment of a reflector device according to the invention is shown and denoted with the reference numeral 80. Similar to the embodiments shown in figures 5A, 5B, 6A and 6B, the reflector device 80 of figures 7A to 7C comprises a carrier element 50' as well as a plurality of mirror segments 82a-82c forming a continuous reflective surface layer carried on the body part of the carrier structure.

Once again, figure 7B shows a section along the Y-direction before the shaping of the mirror segments 82a-82c and figure 7C shows a section along the X-direction after the shaping of the mirror segments 82a-82c. In contrast to the embodiment of figures 6A and 6B, in which an intermediate layer 74 with a predetermined curvature was provided on the body part of the carrier structure 50, in the embodiment of figures 7A to 7C, the curvature is provided by the body part of the carrier structure 50' itself.

For this purpose, the top layer 56c' of the body part of the carrier structure 50 comprising stacked layers 56a'-56c' is formed by tubes of different lengths, which are arranged such that the shortest tubes are positioned in the center of the carrier structure while longer tubes are positioned towards the edges of the carrier structure 50' both in the X and the Y direction.

Consequently, the first side F of the carrier structure 50' exhibits a parabolic or concave shape similar to the shape of the intermediate layer 74 of the embodiment shown in figures 6A and 6B.

Again, the shaping of the mirror segments 82a-82c can be performed by applying pressure on them such that their shaped adapts to the shape of the underlying top layer 56c' of the body part 50' of the carrier structure.

Depending on the properties of the material used for the mirror segments 82a-82c, this shaping of the mirror segments 82a-82c can be performed with the mirror segments being pressed at ambient temperature or heated prior to or during the shaping process.

Claims

1 . Reflector device carrier structure for carrying on its first side (F) a reflective surface layer, comprising:

a back plate (12; 12'; 22; 32; 32'; 42),

a body part (14; 14'; 24; 34; 34'; 44) positioned on the back plate (12; 12'; 22; 32; 32'; 42) and having at least two stacked layers (16a-16c; 16a'-16c'; 26a-26c; 36a-36c; 36a'-36c'; 46a, 46b), each of which formed by a hollow structure made of a construction material, wherein adjacent stacked layers (16a-16c; 16a'-16c'; 26a-26c; 36a-36c; 36a'-36c'; 46a, 46b) are separated by a sheet layer (18; 18'; 28; 38; 38'; 48),

wherein of the at least two stacked layers (16a-16c; 16a'-16c'; 26a-26c; 36a-36c; 36a'-36c'; 46a, 46b) pairs of adjacent layers differ in at least one parameter of their hollow structures, such as orientation.

2. Reflector device carrier structure according to claim 1 , wherein at least one of the stacked layers (46a-46b) comprises a honeycomb structure.

3. Reflector device carrier structure according to claim 1 or claim 2, wherein at least one of the stacked layers (16a-16c; 16a'-16c'; 26a- 26c) comprises a tube structure, wherein preferably the longitudinal axes of the tubes are aligned with the stacking direction of the stacked layers (16a-16c; 16a'-16c'; 26a-26c) and/or perpendicular to the back plate (12; 12'; 22).

4. Reflector device carrier structure adapted to carry on its first side (F) a reflective surface layer, if desired according to any one of the preceding claims, comprising:

a back plate,

a body part positioned on the back plate and having at least one layer (56a'-56c') comprising a tube structure, wherein the longitudinal axes of the tubes are perpendicular to at least one of the back plate and the reflective surface layer,

wherein the tubes of at least one layer (56c¹), preferably the layer adjacent to first side of the reflector device carrier structure, are sized and arranged such that the first side of the reflector device carrier structure has a predetermined curvature.

Reflector device carrier structure according to claim 4, wherein the first side (F) of the reflector device carrier structure has a predetermined curvature along two orthogonal directions (X, Y).

Reflector device carrier structure adapted to carry on its first side a reflective surface layer, if desired according to any one of the preceding claims, comprising:

a back plate; and

a body part positioned on the back plate and separating the back plate from the reflective surface;

the body part being made of a discrete array or a connected network of essentially hollow support structures, oriented with at least one parameter of their hollow structures either parallel or perpendicular to the back plate.

Reflector device carrier structure according to any of the preceding claims, wherein the construction material comprises recycled plastics and/or recyclable plastics and/or biodegradable material.

Reflector device carrier structure according to any one of the preceding claims, wherein on its first side (F) a plate layer is provided, preferably a continuous plastic sheet.

Method for producing a reflector device carrier structure adapted to carry on its first side (F) a reflective surface layer according to any one of claims 4 to 8, comprising: providing a back plate,

forming a body part by arranging one layer (56c') comprising a tube structure or at least two stacked layers (56a'-56c') of which at least one (56c') comprises a tube structure on the back plate,

wherein at least one layer (56c') comprising a tube structure is formed by providing tube sections with predetermined lengths and arranging them on the back plate in such a manner that the first side (F) of the reflector device carrier structure has a predetermined curvature.

Method according to claim 9, wherein providing tube sections with predetermined lengths comprises cutting one or more tubes into tube sections of the desired lengths.

Reflector device, comprising:

a single continuous carrier element (50; 50'), if desired embodied by a reflector device carrier structure according to any one of claims 1 to 8, adapted to carry on its first side (F) a reflective surface layer and on its second side having a back plate, and

a reflective surface layer attached to the carrier element and having a predetermined curvature,

wherein the reflective surface layer consists of at least two mirror segments (62a-62c; 72a, 72b; 82a-82c) which are arranged on the first side (F) of the carrier element (50; 50') such that a single continuous reflective surface is formed which is shaped along two orthogonal directions (X, Y) according a desired curvature of the reflective surface layer.

Reflector device according to claim 1 1 , wherein

the reflective surface layer is non-axisymmetric and/or

the reflective surface layer has different curvatures along different directions.

13. Method for producing a reflector device, comprising: providing a carrier structure (50) adapted to carry on its first side (F) a reflective surface layer and on its second side having a back plate, if desired according to any one of claims 1 1 and 12,

applying an intermediate layer (74) on the first side (F) of the carrier structure (50),

disposing at least one mirror segment (72a, 72b) on the intermediate layer (74),

exerting pressure on the at least one mirror segment (72a, 72b) such that the at least one mirror segment (72a, 72b) is being shaped along two orthogonal directions (X, Y) in order to achieve a desired curvature of the reflective surface layer formed by the at least one mirror segment (72a, 72b).

14. Method according to claim 13, wherein the intermediate layer (74) is applied on the first side (F) of the carrier structure (50) in non-uniform thickness.

15. Method according to any claim 13 or claim 14, wherein the intermediate layer (74) has adhesive properties and provides the attachment of the at least one mirror segment (72a, 72b) to the carrier structure (50).

16. Method according to any of claims 13 to 15, wherein at least one roller and/or at least one inflatable bag is used to exert pressure on the at least one mirror segment (72a, 72b).

17. Method according to any of claims 13 to 16, wherein the shaping of the at least one mirror segment (72a, 72b) is performed at ambient temperature.

18. Method according to any of claims 13 to 16, wherein the at least one mirror segment (72a, 72b) is heated prior to or during it being shaped.