MX2008003526A - Method for production of an optical mirror - Google Patents

Abstract

In order to produce heliostats, which are used in solar-thermal power stations, the method according to the invention provides for a mirror plate (1) to be placed on a mount structure (2) using a required-shape mould (5) and with the interposition of adhesion means (6). The required-shape mould (5) and the position and orientation with respect to a defined reference point are in this case transferred to the mirror plate (1) and are modelled into the adhesive means (6). Once the adhesive means (6) have cured, the required-shape mould (5) is removed, after which its shape is embossed in the mirror plate (1).

Description

METHOD FOR THE PRODUCTION OF AN OPTICAL MIRROR DESCRIPTION OF THE INVENTION The invention relates to a method for the production of an optical mirror, in particular for a solar collector, where a mirror plate, which has a reflection side and an adhesion side, is placed on a support structure. This mirror unit and support structure is hereinafter referred to as a heliostat. Concentrating solar collectors of this type have been known for a long time. These are generally produced by sticking a mirror sheet in a support structure. A method of this type is also described in DE 38 32 961 Al. The invention is based on this in finding a method that allows the gluing of certain types of sheet that previously could not be glued. This is achieved inventively because the sheets that will be used are superficially melted by application of heat, then they are provided with a glue and finally they are put in contact by pressing the sheet surfaces, one against the other. The sheet applied in this way in its outline on a substrate surface is then mounted on a structure of Support that is adapted to the requirements through a fine adjustment. Solar thermal plants usually operate with a mirror arrangement and a heat sink, the so-called receptor. Here you can differentiate between tracking systems on an axis or on two axes. The heliostats of the heliostat field are displaced with the help of motors in such a way that incident sunlight is reflected and diverted to the receiver, located at a height above the mirrors. The receiver has, in a one-axis system, one or several absorber tubes, in a two-axis system a tube bundle or a volumetric absorber. This absorbs the solar radiation concentrated by the heliostats and conducts this energy, converted into heat, with the help of a medium that flows through it. In the course of the day, the heliostats are displaced according to the position of the sun that sunlight always falls on the receiver. Among other options, heliostats of this type are produced in such a way that their support structure corresponds as precisely as possible to the theoretical shape of the mirror and the mirror itself is fixed in this structure so that its theoretical form is adjusted. The mirror plate itself is molded to the required shape, in the case of a small curvature, by elastic stress, in the case of a larger curvature also by thermal deformation. The exact conduction of the sunlight requires a very high precision in the production of the heliostats used. The mirrors have a certain curvature according to their distance from the receiver. To achieve maximum performance it is necessary to respect the curvature parameters of the mirror surface with maximum precision. It is problematic in this that the production of such an exact mirror could be carried out technically up to now only with a very large investment, since from the support structure had to meet these requirements of precision. The solution is therefore known to produce a mirror with a medium precision and fine-tune it with a fine adjustment. This method involves high demands on both the material of the support structure and the technicians who perform the fine adjustment. It is necessary to define individual adjustable points in the support structure that allow a fine adjustment by adjusting screws. For the optimal adjustment of the collectors requires the use of specialized personnel, which is a cause of great costs. Just in times of rising energy costs, solar thermal plants tend to be a useful alternative to fossil fuels.

The invention is based, therefore, on the objective of offering a method for the production of an optical mirror that allows to do without a fine adjustment of the mirror, after its production, without undermining the precision and allowing an economic production on an industrial scale of such mirrors. This objective is solved by the method having the characteristics of the main claim. Significant modifications of this method can be derived from the subordinate claims. Inventively it is used, for the production of an optical mirror - in particular of a heliostat for a concentration solar collector -, a mirror plate that has been placed in a theoretical contour mold. The reflective side is, in this case, supported against the theoretical contour mold. The theoretical contour mold represents an impression of the ideal curvature for the mirror in turn, so that by direct support of the plate in the theoretical contour mold, also the mirror plate is molded into its final shape, particularly its curvature final . So that the mirrors, which form the thermosolar plant, can be displaced following the sun, they are installed in support structures that can pivot in such a way that the maximum is always transmitted possible energy to the receiver. The mirror plate is placed on the support structure by interposing a glue. The plate keeps its theoretical outline in this, so that it always retains its ideal contour. The plastic glue joins the plate with the support structure, so that the plate is held in its current position after the glue has hardened. It has turned out to be an advantage when the support structure is first provided with glue and the mirror plate is then printed on the glue. The glue is displaced, while the mirror plate is housed in a positive connection, resting closely on the theoretical contour mold and preserves this contour also thanks to the support of the theoretical contour mold. The mirror plate remains in this position together with the theoretical contour mold at least until the glue has hardened at least approximately. After removing the theoretical contour mold, the mirror plate continues to maintain the outline of the theoretical contour mold, which corresponds with great precision to the ideal curvature for the mirror. An application of the glue, for example in the support structure, does not have to be done in such a way as to cover an area. It is sufficient, therefore, to apply the glue on individual support points and hold the plate, therefore, only at predetermined points. This allows to save glue and, on the other hand, the glue, which yields under the pressure of the placed mirror plate, can thus flow into the interstices between the support points. Thanks to the fact that fine adjustment is not required, it is convenient to use a rigid support structure for mounting the mirror plate. This support construction does not need to correspond to the high precision requirements of the theoretical contour mold, thanks to the method, since the tolerances are compensated by the glue. Also a subsequent fine adjustment is inventively omitted, which represents a further simplification of the construction and simultaneously produces a cost saving in the production of the support structure. The mechanical strength of the mirror plate is further favored because the plate consists of a rigid, but flexible material. If a soft plate is used, then it would not be possible to definitively prevent further deformation, for example at points with less support for support points. The invention, described in the foregoing, is explained below in more detail by means of figures 1 to 3. It is shown: 1 a support structure, as well as a mirror plate mounted on a theoretical contour mold prior to assembly in a sectioned image representation, FIG. 2 a support structure with a mirror plate placed, even without removing the contour mold Theoretical, in a representation of sectioned image, and Figure 3 a finished heliostat, produced according to the inventive method, also in a sectioned image representation. Figure 1 shows a support structure 2 for the production of a heliostat. In the support structure 2, glue 6 has been applied to individual support points 7. In preparation for the production, a mirror plate 1 having a reflection face 3 and an adhesion face 4 is fixed in a theoretical contour mold 5 in such a way that the mirror plate 1 exactly represents the contour of the mold 5 of theoretical outline on its face 3 of reflection. In the representation, the mirror plate 1 is drawn at a distance from the theoretical contour mold 5 to guarantee a unique designation of symbols. But in fact, the mirror plate 1 is mounted in the theoretical contour mold 5 so that it rests intimately on it. Figure 2 shows a second stage of the method of production, in which the mirror plate 1 is printed, together with the theoretical contour mold 5, in the glue 6 filled. The glue 6 moves in this towards the sides, so that the outline of the mirror plate 1, after all, is transferred to the glue 6. The theoretical contour mold 5 is left for so long on the mirror plate 1 until the glue 6 has hardened and supported, on the one hand, the contour of the mirror plate 1, and also fixes it thanks to its adhesive force. After the glue 6 has hardened, the theoretical contour mold 5 can be removed, the mirror plate 1 retaining the curvature predetermined by the theoretical contour mold 5. Figure 3 shows the finished heliostat that deflects the sunlight, drawn with a line of dashes and dots in the figure, to a receiver 8. This is just a representation of principle for which it must be taken into account that there are several heliostats as well associates The support structure 2 can pivot in a way that is not of interest here, so that "the arrangement can follow the sunlight in such a way that the maximum light output is always diverted towards the receiver 8. The curvature of the the mirror plate 1 is predetermined by its theoretical contour mold as a function of the distance between the heliostat and the receiver 8.

In the foregoing, therefore, a method is described for the production of an optical mirror, in particular for a solar collector, which allows an accurate and, however, fast and simple production of such heliostats. This is achieved through the use of a theoretical contour mold, on which the mirror plate is mounted that must be fixed in a support structure. This plate is placed together with the theoretical contour mold, by interposing a glue on the support structure and this is removed only after the glue has hardened and, consequently, the mirror contour remains. List of reference symbols 1 Mirror plate 2 Support structure 3 Reflection face A Adhesion face 5 Contour contour mold 6 Glue 7 Support points

Claims (5)

1. Method for the production of an optical mirror, in particular for a solar collector, where a mirror plate having a reflection face and an adhesion face is placed on a support structure and the mirror plate is mounted with its face reflection in a theoretical contour mold, characterized in that the mirror plate is then placed with its adhesion side, together with the theoretical contour mold, by interposing a glue on the support structure, separating the theoretical contour mold from the plate of mirror when the glue is hardened at least approximately. Method according to claim 1, characterized in that the mirror plate is housed at least almost positively in the theoretical contour mold prior to assembly, because the adhesive is applied to the support structure and the mirror plate is printed on extended form in the glue with the adhesion face in such a way that the reflection face of the mirror plate represents at least approximately the surface of the theoretical contour mold. Method according to claim 2, characterized in that the adhesive is applied only in individual support points in the support structure. Method according to one of the preceding claims, characterized in that a rigid structure is used as the support structure. Method according to one of the preceding claims, characterized in that the mirror plate consists of a rigid, but flexible material.