TECHNICAL FIELD

Embodiments herein relate to fasteners. In particular, embodiments herein relate to an arrangement of fasteners for securing a mirror to a support of a parabolic solar reflector. Also, embodiments herein relate to a mirror comprising an arrangement of fasteners and a parabolic solar reflector. BACKGROUND

Concentrated Solar Power, CSP, systems generate solar power by using mirrors or lenses to concentrate a large area of sunlight, or solar thermal energy, onto a small area. Energy from the concentrated area may thereafter be converted to electrical energy. In systems comprising a parabolic solar reflector, a single parabolic reflector focuses solar thermal energy toward a focal point. Traditional parabolic solar reflectors often comprise a large parabolic mirror mounted to a vertical support. Alternatively, a parabolic solar reflector may also comprise several smaller mirrors, wherein each small mirror is mounted such that the small mirrors form a single parabolic reflector as a whole. The mirrors may be fastened to a support with its reflective side being angled towards the focal point of the parabolic solar reflector.

Since the parabolic solar reflectors are often placed in locations that may experience extreme weather conditions in order to receive as much sunlight as possible, such as, e.g. hot deserts or cold arctic areas, they must be made to endure these kind of harsh environments. One example is that winds may cause the structure of the parabolic solar reflector to cringe and sway and making the mirrors move, vibrate or shake, and consequently causing the mirrors to get damaged or break. Another example is that large temperature differences may cause the mirrors of a parabolic solar reflector to thermally expand or contract and thus crack around its fastening points.

SUMMARY

It is an object of embodiments herein to prevent mirrors fastened to a support of a parabolic solar reflector from getting damaged or break. According to a first aspect of embodiments herein, the object is achieved by an arrangement of fasteners for securing a mirror of a parabolic solar reflector to a support of said parabolic solar reflector. The arrangement of fasteners comprises a first, second and third fastener arranged on the back of said mirror in a triangular formation. Each of the 5 first, second and third fastener comprises a mounting plate and a collar having an

aperture arranged to receive a fastening element in order to connect the mirror to the support. The mounting plate of the first fastener is configured such that the collar is laterally movable in all directions with respect to the mounting plate, the mounting plate of the second fastener is configured such that the collar is laterally fixed with respect to the o mounting plate, and the mounting plate of the third fastener is configured such that the collar is laterally movable along a single line of direction with respect to the mounting plate.

By having an arrangement of fasteners as described above, a tension-less fastening5 of a mirror to a support of a parabolic solar reflector is enabled. This is because the triangular formation of the fasteners and the combined moving pattern of the collars will enable the mirror to move, expand or contract in a controlled manner when mounted and secured on the support of the parabolic solar reflector. Thus, forces acting on the parabolic solar reflector or thermally related forces of the mirror will not be transferred0 between any of the fasteners and the mirror. This means that the mirror will be a lot less likely to crack or break around its fastening points to the support of the parabolic solar reflector. Hence, an improved fastening of a mirror to a support of a parabolic solar reflector is provided. This will prevent mirrors fastened to a support of a parabolic solar reflector from getting damaged or break.

5

In some embodiments, the single line of direction along which the collar of the third fastener is laterally movable is substantially in the direction of the second fastener. In some embodiments, each mounting plate of the first second and third fastener may comprise a central aperture through which the fastening element is able to extend in order0 to be received by the aperture of the collar. In this case, according to some embodiments, the single line of direction along which the collar of the third fastener is laterally movable is substantially in the direction of the central aperture of the mounting plate of the second fastener. This means that, while the mirror is laterally fixed via the second fastener, the free lateral movement of the first fastener and the single directional lateral movement of the third fastener ensures that the mirror may only move, expand or contract in

predetermined ways.

In some embodiments, the mounting plate of the first fastener is configured such that the collar is laterally movable in all directions with respect to the mounting plate by having a central aperture that is larger than the aperture of the collar in all directions. Also, in some embodiments, the mounting plate of the second fastener is configured such that the collar is laterally fixed with respect to the mounting plate by having a central aperture that is substantially the same size as the aperture of the collar. Further, in some embodiments, the mounting plate of the third fastener is configured such that the collar is laterally movable along a single line of direction with respect to the mounting plate by having a central aperture that extends in said single line of direction. These provide a simple way to enable a controlled lateral movement of the mirror via the mounting plates of each of the first, second and third fastener.

In some embodiments, each mounting plate of the first second and third fastener may comprise a cavity for housing the collar between the mounting plate and the back of said mirror. This will create a space between the back of the mirror and the mounting plate into which the shaft of the fastening element may extend when being inserted and fastened. In some embodiments, one or more of the mounting plates of the first second and third fastener may be adapted to be adhered to or mechanically attached onto the back of the mirror. This enables the fastener to be attached to the back of the mirror is several different ways. According to a second aspect of embodiments herein, the object is achieved by a mirror comprising an arrangement of fasteners as described above. According to a fourth aspect of embodiments herein, the object is achieved by a parabolic solar reflector comprising one or more mirrors as described above. BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the embodiments will become readily apparent to those skilled in the art by the following detailed description of exemplary embodiments thereof with reference to the accompanying drawings, wherein: Fig. 1 illustrates a side-view of a concentrated solar power system comprising a parabolic solar reflector,

Fig. 2 illustrates a cross-sectional view of a fastening element and a fastener,

Fig. 3 illustrates a cross-sectional view of a fastener and a side-view of a

fastening element,

Fig. 4 illustrates embodiments of an arrangement of fasteners and a mirror,

Fig. 5 illustrates further embodiments of an arrangement of fasteners and a

mirror.

DETAILED DESCRIPTION

In the following, a detailed description of the different embodiments of a fastener and a fastening element is disclosed with reference to the accompanying drawings. All examples herein should be seen as part of the general description and are therefore possible to combine in any way in general terms. Individual features of the various embodiments and methods may be combined or exchanged unless such combination or exchange is clearly contradictory to the overall function.

Fig. 1 , illustrates a concentrated solar power system 100 from a side view showing the concentrated solar power system 100 in the way that the system is normally visible when deployed and in use. The concentrated solar power system 100 comprises a parabolic solar reflector 1 10 and a support 120 for the parabolic solar reflector 1 10. The parabolic solar reflector 1 10 may comprise one or more mirrors 1 1 1 . The mirror of the parabolic solar reflector 1 10 are arranged on the support 120 such that their reflective sides are angled towards the focal point of the parabolic solar reflector 1 10. It is understood that any further parts of the concentrated solar power system 100 are not relevant to the description of the embodiments herein and are therefore not described in more detail herein.

Fig. 2 illustrates a cross-sectional view of a mirror 1 1 1 , a fastening element 210 and a fastener 220. The mirror 1 1 1 comprises a reflective side 1 12, or front side, and a back side 1 13. The fastener 220 is attached to the back side 1 13 of the mirror 1 1 1 . The fastener 220 may comprise a mounting plate 230, a collar 240, protective discs 250, 251 , and a supporting disc 260. The mounting plate 230, the collar 240 and the supporting disc 260 may be made of a metal, such as, e.g. steel.

The mounting plate 230 may comprise a circumferential edge 231 , a cavity 232 and a central aperture 231 . The circumferential edge 231 may be arranged to be tightly fixed to the back side 1 13 of the mirror 1 1 1 . The circumferential edge 231 may, for example, be adhered to the back side 1 13 of the mirror 1 1 1 using any suitable adhesive or glue. Alternatively, the circumferential edge 231 may, for example, comprise one or more holes in order to allow the mounting plate 230 to be screwed or nailed tightly onto the back side 1 13 of the mirror 1 1 1 . The shape of the mounting plate 230 may provide a cavity 232 between the back side 1 13 of the mirror 1 1 1 and the mounting plate 230. The cavity 232 may be adapted such that the mounting plate 230 may house the collar 240. The cavity 232 is also adapted such that the space between the back side 1 12 of the mirror 1 1 1 and the mounting plate 230 is large enough in order to enable a shaft 21 1 of the fastening element 210 to extend into the space, when being inserted and fastened into the fastener 220, without coming into contact with the back side 1 13 of the mirror 1 1 1 .

The collar 240 may be arranged to extend through the central aperture 233 of the mounting plate 230; that is, the collar 240 may be mounted in and about the central aperture 233 of the mounting plate 230. A first protective disc 250 may be arranged between the collar 240 and the mounting plate 230. The first protective disc 250 may extend around the central aperture 233 of the mounting plate 230. A second protective disc 251 may be arranged on the outside of the cavity 232 of the mounting plate 230 between the mounting plate 230 and a supporting disc 260. The second protective disc 251 and the supporting disc 260 may extend around the central aperture 233 of the mounting plate 230. The first and second protective discs 250, 251 may be made of a soft material, such as, rubber or plastic. A more detailed description of the collar 240 is provided below with reference to Fig. 3.

The fastening element 210 comprise a shaft 21 1 having a first end being adapted to be inserted into and fastened in the collar 240 of the fastener 220 and a second end being adapted to be inserted into and fastened in the support 120 of the parabolic solar reflector 1 10. The fastening element 210 may also be referred to as an adjustment screw, since by screwing the fastening element 210 in or out of the support 120 the angle of the mirror 1 1 1 may be adjusted.

The shaft 21 1 may also comprise a threaded section 214. The threaded section 214 allows the shaft 21 1 to be screwed into the support 120. The support 120 may comprise a hole arranged with a receiving threaded part 121 . The receiving threaded part 121 may be arranged to receive and engage with the threaded section 214 of the shaft 21 1 in order to secure the shaft 21 1 in the support 120. The threaded section 214 may be located at a mid-section of the shaft 21 1 . This enables the fastening element 210 to extend beyond the treaded section 214 and all the way through the support 120. This allows a section of the shaft 1 1 1 to protrude out of the support 120 on the back of the parabolic solar reflector 1 10. This section of the shaft 1 1 1 may then be used to adjust how far into the support 120 the shaft 1 1 1 of the fastening element 210 should be inserted. This enables the angle of the mirror 1 1 1 to be easily adjusted after being mounted on the support 120 using the fastening element 210 and the fastener 220.

The fastening element 210 may further comprise a mechanical spring 212 and a circumferential edge 213 around the shaft 21 1 . When the shaft 21 1 of the fastening element 210 is inserted into the collar 240 of the fastener 220, as shown in Fig. 1 , the mechanical spring 212 may be compressed between the circumferential edge 213 and the supporting disc 260 of the fastener 220. Thus, the mechanical spring 212 may exert a force onto the fastener 220 attempting to pull the shaft 21 1 out of the collar 240. This force may aid in securing a tight lock of the fastening element 210 in the fastener 220. In doing so, the mechanical spring 212 of the fastening element 210 also compresses the first and second protective discs 250, 251 between the collar 240, the mounting plate 230 and the supporting disc 260 such that there is no gap therein between that may cause vibrations or rattling.

In another example, the circumferential edge 213 may be replaced by extending the threaded section 214 towards the first end of the shaft 1 1 1 and having a threaded nut (not shown) providing the support for the mechanical spring 212. A more detailed description of the first end of the shaft 1 1 1 being adapted to be inserted into and fastened in the collar 240 of the fastener 220 is provided below with reference to Fig. 3.

Fig. 3 illustrates a cross-sectional view of a fastener 220 and a side-view of a fastening element 210.

As shown in Fig. 3, the collar 240 of the fastener 220 may be adapted to guide the shaft 21 1 of the fastening element 210 by further comprising at least a partly conical shaped aperture 241 . For example, the at least a partly conical shaped aperture 241 of the collar 240 may be widest where the shaft 21 1 enters the at least partly conical shaped aperture 241 and then become narrower further into the at least partly conical shaped aperture 241 before ending at a circumferential edge 242. This means that the at least partly conical shaped aperture 241 may guide the shaft 21 1 into and towards the centre of the at least partly conical shaped aperture 241 when the shaft 21 1 of the fastening element 210 is inserted into the collar 240, as shown by the arrow in Fig. 3.

The at least a partly conical shaped aperture 241 may comprise a circumferential 5 edge 242. The circumferential edge 242 may be adapted to cooperate with a locking ring 215 of the fastening element 210, as described in more detail below, in order to prevent the shaft 21 1 of the fastening element 210 from leaving the collar 240 once the shaft 21 1 of the fastening element 210 has been inserted into the collar 240. The circumferential edge 242 and the at least a partly conical shaped aperture 241 thus allowing the locking

1 o ring 215 of the shaft 21 1 to be moved and guided into a position in which it may cooperate with the circumferential edge 242 of the partly conical shaped aperture 241 and prevent the shaft 21 1 from leaving the collar 240.

As further shown in Fig. 3, the first end of the shaft 21 1 of the fastening element 210 may be adapted to be inserted into in the collar 240 of the fastener 220 by having an at

1 5 least partly conically shaped end-section 217. This enable the shaft 21 1 to be easily

guided by the at least partly conical shaped aperture 241 of the collar 240 while being inserted into the collar 240 of the fastener 220.

Furthermore, the first end of the shaft 21 1 of the fastening element 210 may be adapted to be fastened in the collar 240 of the fastener 220 by comprising a locking ring

20 215. The locking ring 215 may be circular or semi-circular in shape and may be a rounded or a flat ring. The locking ring 215 may, for example, be made of metal, such as, steel, or rubber. The locking ring 215 may be comprised in a recess 216 in the shaft 21 1 . The recess 216 of the shaft 21 1 may be formed in such a way that it enables the locking ring 215 to be moved past the circumferential edge 242 of the at least a partly conical shaped

25 aperture 241 of the collar 240 and cooperate with the circumferential edge 242 to prevent the shaft 21 1 from leaving the collar 240 once the shaft 21 1 has been inserted into the collar. This provides an easy snap-in locking mechanism wherein the locking ring 215 may be compressed into the recess 216 by, and while being guided in, the at least partly conical shaped aperture 241 of the collar 240, and then expand once passed the

30 circumferential edge 242 of the collar 240. The recess 216 may also be adapted to hold the locking ring 215 in place prior to the fastening element 210 being inserted into the collar 240 of the fastener 220.

It should also be noted that the locking ring 215 allows for the fastening element 210 may turn or rotate in respect to the collar 240, and thus in respect to the fastener 220 and

35 the mirror 1 1 1 . This enables the fastening element 210 to be adjustably screwed into or out of the support 120 while being locked in the fastener 220, and thus further facilitating an easy adjustment of the angle of the mirror 1 1 1 subsequent to mounting the mirror 1 1 1 onto the support 120.

It should also be noted that the locking ring 215 of the shaft 21 1 of the fastening 5 element 210 prevents the shaft 21 1 and the fastening element 210 from leaving the collar 240 of the fastener 220, while the mechanical spring 215 applies a force attempting to push the shaft 21 1 of the fastening element 210 out of the collar 240 of the fastener 220. This combination ensures a tight, yet flexible lock of the fastening element 220 in the fastener 220.

1 0

Fig. 4 illustrates embodiments of an arrangement of fasteners 220 and a mirror 1 1 1 . A first, second and third fasteners 220a, 220b, 220c are attached to the mirror 1 1 1 in a triangular formation on the back side 1 13 of the mirror 1 1 1 . In this example, the first fastener 220a comprise a mounting plate 230a having a central aperture 320a that is 1 5 square shaped and larger in all lateral directions in respect to the central aperture 310a of the collar 240a.

Also, in this example, the second fastener 220b comprise a mounting plate 230b having a central aperture 320b that is round and is substantially the same size as the central aperture 310b of the collar 240b. However, is should be noted that the mounting

20 plate 230b and the collar 240b in this case may also be formed as a single unit. In this case, the collar 240b would be incorporated into the mounting plate 230b and no central aperture 320b of the mounting plate 230b would be needed. This may be advantageous since it may simplify the manufacturing process of the second fastener 220b.

Furthermore, in this example, the third fastener 220c comprise a mounting plate

25 230c having a central aperture 320c that is substantially the same size as the central aperture 310c of the collar 240c in all but one single line of direction. In this single line of direction, the central aperture 320c is larger than the central aperture 310c of the collar 240c.

30 Fig. 5 illustrates embodiments of an arrangement of fasteners 220 and a mirror 1 1 1 .

Fig. 5 is identical to Fig. 4, except in that it includes a dashed line 510 indicates the single line of direction of the central aperture 320c of the mounting plate 230c of the third fastener 220c when the mounting plate 230c of the third fastener 220c is directed substantially in the direction of the second fastener 220b. It also includes a dash-dotted

35 line 51 1 that indicates the single line of direction of the central aperture 320c of the mounting plate 230c of the third fastener 220c when the mounting plate 230c of the third fastener 220c is directed substantially in the direction of the central aperture 320b of the mounting plate 230b of the second fastener 220b. It should also be noted that the wording "laterally movable" herein refers to lateral movements in the same plane. Furthermore, the wording "laterally fixed" herein refers to the case where all lateral movements, except rotation, in the same plane is fixed.

The terminology used in the detailed description of the particular embodiments illustrated in the accompanying drawings is not intended to be limiting of the described arrangement of fasteners 220, mirror 1 1 1 or parabolic solar reflector 100 which instead should be construed in view of the enclosed claims. As used herein, the term "and/or" comprises any and all combinations of one or more of the associated listed items.

Further, as used herein, the common abbreviation "e.g.", which derives from the Latin phrase "exempli gratia," may be used to introduce or specify a general example or examples of a previously mentioned item, and is not intended to be limiting of such item. If used herein, the common abbreviation "i.e.", which derives from the Latin phrase "id est," may be used to specify a particular item from a more general recitation. The common abbreviation "etc.", which derives from the Latin expression "et cetera" meaning "and other things" or "and so on" may have been used herein to indicate that further features, similar to the ones that have just been enumerated, exist.

As used herein, the singular forms "a", "an" and "the" are intended to comprise also the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms "includes," "comprises," "including" and/or "comprising," when used in this specification, specify the presence of stated features, actions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, actions, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms comprising technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the described embodiments belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above embodiments should not be construed as limiting.