SOLAR CONCENTRATOR FACET, SOLAR CONCENTRATOR COMPRISING SAID FACET AND METHOD OF INSTALLATION THEREOF

Abstract

The invention relates to a facet for solar concentrators, suitable for its use as reflective element of a heliostat, the facet comprising a main body defining a front surface and a back surface. Advantageously, the back surface of the main body is attached to at least three substantially linear ribs, which are arranged substantially parallel along said back surface, and wherein at least one of the three ribs is configured with adjustable anchoring means adapted for their connection to the structure of a solar concentrator. Moreover, the anchoring means are adapted such that the distance between at least one of the three ribs and the structure of a solar concentrator can be varied. The invention also relates to a solar concentrator comprising said facet, and to a method of installation thereof.

Claims

1. A facet for solar concentrators, suitable for its use as reflective element of a solar concentrator, the facet comprising a main body defining a front surface and a back surface; wherein the back surface of the main body is attached to at least three substantially linear ribs, which are arranged substantially parallel along said back surface, and wherein at least one of the three ribs is configured with adjustable anchoring means adapted for their connection to the structure of a solar concentrator, such that the distance between at least one of the three ribs and the structure of a solar concentrator can be varied by adjusting the anchoring means; wherein each of the three ribs comprises a plurality of anchoring orifices adapted for receiving the adjustable anchoring means.

2. The facet according to claim 1, wherein the ribs are channel-formed and comprise fixation surfaces adapted for their attachment to the back surface of the main body.

3. The facet according to claim 2, wherein the fixation surfaces comprise linear flaps arranged at both sides of the ribs, and wherein the ribs are attached to the back surface of the facet though adhesive means applied to the linear flaps.

4. The facet according to claim 2, wherein the inner volume defined by the channel-formed ribs is configured as a housing for at least part of the anchoring means.

5. The facet according to claim 1, wherein the anchoring means comprise one or more washers configured as conical-spherical pairs of connectors.

6. The facet according to claim 1, wherein the main body of the facet comprises, a glass body, a metallic reflective body, a mirror body, a multi-layer or sandwich body, a plastic body, a foam body, a honeycomb body, or any combination thereof, in any technically possible order.

7. The facet according to claim 1, wherein the main body of the facet is substantially flat, non-flat, parabolic, cylindrical, hyperbolic, or spherical.

8. A solar concentrator comprising: a pedestal; a torque tube; a plurality of transverse arms supported by the torque tube, wherein the transverse arms are connected to a plurality of longitudinal bars arranged substantially parallel to the torque tube; and one or more facets according to claim 1; wherein the longitudinal bars are configured with a plurality of anchoring points adapted to attach the facets to the longitudinal bars through the anchoring means.

9. The solar concentrator according to claim 8, wherein: the longitudinal bars are arranged substantially parallel to the torque tube; the transverse arms are arranged substantially perpendicular to the torque tube; the transverse arms are arranged on both sides of the torque tube; one, two or three of the anchoring means of the at least three ribs are adjustable; and/or the connection between the transverse arms and the longitudinal bars comprises a plurality of fixing means comprising screws, nuts, bolts, rivets, or flanges.

10. The solar concentrator according to claim 8, wherein at least part of the anchoring means is housed within the longitudinal bars.

11. A method for installing a facet for solar concentrators, suitable for its use as reflective element of a solar concentrator, wherein the facet comprising a main body defining a front surface and a back surface; wherein the back surface of the main body is attached to at least three substantially linear ribs, which are arranged substantially parallel along said back surface, and wherein at least one of the three ribs is configured with adjustable anchoring means adapted for their connection to the structure of a solar concentrator, such that the distance between at least one of the three ribs and the structure of a solar concentrator can be varied by adjusting the anchoring means; wherein each of the three ribs comprises a plurality of anchoring orifices adapted for receiving the adjustable anchoring means in a solar concentrator according to claim 8; wherein said method comprises performing the following steps of: a) mounting the facet in the solar concentrator, by connecting the facet to one or more longitudinal bars through the anchoring means; b) adjusting the curvature of the facet around an axis substantially parallel to the ribs, by varying the relative distances between at least one of the three ribs and the longitudinal bars.

12. The method according to claim 11, wherein a canting operation comprising orienting the facet relative to the solar concentrator is performed during step b) of the method.

13. The method according to claim 11, further comprising the following step before step a): c) adjusting the curvature of the facet around at least one axis thereof, wherein said axis is substantially perpendicular to the axis adjusted in step b).

14. The method according to claim 13, wherein, in step c), a curvature on the main body of the facet is generated by attaching the back surface of the main body to the ribs.

Description

DESCRIPTION OF THE DRAWINGS

[0052] FIG. 1 shows a rear view of a heliostat and a plurality of facets according to a preferred embodiment of the invention.

[0053] FIG. 2 shows a detailed view of the heliostat and the facets of FIG. 1.

[0054] FIGS. 3a-3d show different views of a facet according to the present invention.

[0055] FIGS. 4a-4b show different views of the connections of a heliostat and a facet according to the present invention.

NUMERICAL REFERENCES USED IN THE DRAWINGS

[0056] In order to provide a better understanding of the technical features of the invention, the referred FIGS. 1-4 are accompanied of a series of numeral references which, with an illustrative and non-limiting character, are hereby represented:

TABLE-US-00001 (1) Solar concentrator, Heliostat (2) Facet (3) Pedestal (4) Torque tube (5) Control cabinet (6) Transverse arms (7) Longitudinal bars (8) Fixing means (9) Anchoring points (10) Anchoring means (11) Main body of the facet (12) Linear ribs (12) Fixation surfaces (13) Anchoring orifice (14) Fixation flange (15, 15) Washers, conical-spherical pairs (16, 16) Nut fasteners

DETAILED DESCRIPTION OF THE INVENTION

[0057] Different preferred embodiments of the invention, provided for illustrating but non-limiting purposes, are described below, referring to FIGS. 1-4 of the present document.

[0058] FIGS. 1-2 show a heliostat (1) adapted for the installation of a plurality of facets (2) according to a preferred embodiment of the invention. The combined surface of said facets (2) form the reflective surface of the heliostat (1) (or grid), typically ranging from 120 to 210 m.sup.2 (however, smaller dimensions can be also implemented) whose structure is supported by a pedestal (3) and a torque tube (4), preferably configured with dual-axis tracking capacity (by means, for example, of corresponding zenith and azimuth drives). The pedestal (3) of the heliostat (1) of the invention has primarily a structural function, and it is fixed to a foundation and/or to the ground. Said pedestal (3) preferably incorporates a control cabinet (5) in which the control electronics of the heliostat (1) and corresponding electric power supply connections are located. Even though this embodiment will refer to a heliostat (1), this term can also apply to any solar concentrator.

[0059] The torque tube (4) supports a plurality of transverse arms (6), preferably arranged perpendicular thereto, wherein the arms (6) are preferably arranged on both sides of the torque tube (4), and connected to a plurality of longitudinal bars (7), arranged substantially parallel to the torque tube (4). The connection between the transverse arms (6) and the longitudinal bars (7) is obtained by means of a plurality of fixing means (8) which typically comprise screws, nuts, bolts, rivets, flanges, etc. Moreover, the longitudinal bars (7) are configured with a plurality of anchoring points (9) adapted to attach the facets (2) to the main body of the heliostat (1), thereby forming the heliostat (1) reflective grid and providing structural support thereto. As an example, FIG. 1 shows a heliostat (1) whose grid is formed by 8?4 rectangular facets (2). In the figure, the surface of the top left facet (2) has been highlighted within a rectangle in dashed lines (see also a detailed view of the facet (2) in FIG. 2).

[0060] The facets (2) are connected to the longitudinal bars (7) by corresponding anchoring means (10) which are applied to the anchoring points (9) of the bars (7). Said anchoring means (10) preferably adopt the form of adjustable bolts and fasteners, and are adapted such that the distance between the bars (7) and the facet (2) at the position of each anchoring point (9) can be varied. As it will be seen in the following paragraphs, this feature is key in order to obtain a desired curvature configuration of each facet (2), and also in the heliostat (1) as a whole (by canting the facets).

[0061] A preferred embodiment of the facet (2) of the invention is shown in FIGS. 3a-3d. As represented in said figures, the facet (2) comprises a main body (11) which configures the reflective surface of the facet (2). This body (11) can be of any type of the known configurations of the prior art comprising, for instance, a glass body, a metallic reflective body, a mirror body, a multi-layer (or sandwich) body, a plastic, foam, or honeycomb body, and any combination thereof, in any technically possible order. As a result of this combination, the main body (11) of the facet (2) is characterised by having a front surface (typically the reflective surface configured for facing the receiver) and a back surface (typically a support, structural or protective surface which will in general not be subject to direct solar radiation). The main body (11) of the facet (2) can also adopt several geometries and curvatures, being for example substantially flat, parabolic, spherical, cylindrical, hyperbolical, or comprising any other suitable geometry.

[0062] Advantageously in the invention, the back surface of the main body (11) of the facet (2) is attached to a plurality of linear ribs (12), at least three, which are preferably arranged substantially parallel along said surface. The ribs are preferably channel-formed and comprise fixation surfaces (12), preferably in the form of linear flaps, arranged at both sides of the ribs (12) for their attachment to the back surface of the main body (11) of the facet (2). Any possible attachment means can be used to that end, however, adhesive means applied to the linear flaps will in general be preferred. The inner volume configured by the channel-formed ribs (12) can be advantageously used as a housing for at least part of the anchoring means (10) connecting the facet (2) and the longitudinal bars (7).

[0063] In a preferred embodiment of the invention, each rib (12) is configured with at least one anchoring orifice (13) adapted for its alignment with the anchoring points (9) of the bars (7). Thereby, the anchoring means (10) applied from an anchoring point (9) can pass through the anchoring orifice (13) and be fastened to the facet (2), fixing it to the heliostat (1) structure. In further embodiments of the invention, each rib (12) can comprise two or more anchoring orifices (13), and each anchoring orifice (13) can comprise a fixation flange (14), for providing enhanced robustness to the connection between the bars (7) and the facets (2). Optionally, in a further embodiment of the invention, at least part of the anchoring means (10) can be advantageously housed within the longitudinal bars (7), as shown in FIGS. 4a-4b. Also, the anchoring means (10) can comprise one or more washers (15, 15) or any other joining means for improving the effectiveness of the connections of the facets (2) to the longitudinal bars (7). In a preferred embodiment of the invention, the washers (15, 15) are configured as conical-spherical pairs of connectors. Thanks to this configuration, misalignments between the relative orientations of the longitudinal bars and the facet can be achieved, without affecting the relative orientation of the anchoring means and the facet.

[0064] Thanks to the arrangement of at least three parallel ribs (12) in the facet (2), as well as to the application of linearly adjustable anchoring means (10) to the anchoring orifices (13) of said ribs (12), the curvature of the facet (2) around an axis parallel to the ribs (12) can be adjusted by varying the relative distances between the corresponding at least three anchoring orifices (13) of the ribs (12) and the anchoring points (9) of the bars (7). The variation of this distances can be obtained, for instance, by adjusting the position of nut fasteners (16, 16) comprised in the anchoring means (10), as the ones depicted in FIGS. 4a and 4b of the present document. In different embodiments of the invention, one, two or three of the anchoring means (10) of the at least three ribs (12) are adjustable.

[0065] This feature is remarkably advantageous compared to other known facets, as it allows adapting the curvature of each facet (2) in the heliostat (1) after its installation in the solar field. As a result, the need of complex curving processes applied to the facet (2) during its manufacturing can be, at least in part, avoided with the present invention. For example, in a preferred embodiment of the invention the facets (2) can undergo a curving process only around an axis perpendicular to the ribs (12) during its fabrication. This operation is much simpler, faster, and cheaper than curving the facets (2) over two axes at the factory. Later on, once the facets (2) have been installed at the longitudinal arms (7) of the heliostat (1), they can be further curved manually around the axis parallel to the ribs (12), by configuring the distances between the anchoring orifices (13) and the anchoring points (9) with the adjustment of the anchoring means (10). Moreover, this adjustment can be performed at any moment during the lifespan of the heliostat (1), without dismounting the facets (2).

[0066] The use of parallel ribs (12) according to the invention not only simplifies the curving processes of the facets (2), but also improves their robustness and can help reducing optical losses due to thermal expansion in operation conditions. Moreover, the fabrication of the ribs (12) according to the invention can be easily obtained through line manufacturing, cutting the ribs (12) from a longer linear piece in the factory. This process is fast, cost-reduced and does not require complex design profiles of facet-supporting elements for obtaining cylindrical, spherical, parabolic or any other desired geometries in the facet's surface. The mirror used can be also flat, and does not need to have any prior curvature, since the curvature of the facet (2) on the axis perpendicular to the ribs (12) is achieved during the process of attaching the main body (11) of the facet (2) to the ribs (12) in one axis and, in the other axis, during the process of assembly and canting of the facet (2) to the heliostat (1).