Patent Application
20070223121
This application is related to a reflector (e.g., mirror) for use in a solar collector or the like. In certain example embodiments of this invention, a reflector for a solar collector or the like is made by (a) forming a reflective coating on a flat glass substrate, (b) cold-bending the glass substrate with the reflective coating thereon using a mold member; and (c) applying a plate member (e.g., thermoplastic or glass based) to the cold-bent glass substrate, the plate member for maintaining the coated glass substrate in a bent orientation. In certain example embodiments of this invention, the reflector may be used in a solar collector, or in any other suitable application.
Solar collectors are known in the art. Example solar collectors are disclosed in U.S. Pat. Nos. 5,347,402, 4,056,313, 4,117,682, 4,608,964, 4,059,094, 4,161,942, 5,275,149, 5,195,503 and 4,237,864, the disclosures of which are hereby incorporated herein by reference. Solar collectors include at least one mirror (e.g., parabolic or other type of mirror) that reflects incident light (e.g., sunlight) to a focal location such as a focal point. In certain example instances, a solar collector includes one or more mirrors that reflect incident sunlight and focus the light at a common location. For instance, a liquid to be heated may be positioned at the focal point of the mirror(s) so that the reflected sunlight heats the liquid (e.g., water, oil, or any other suitable liquid) and energy can be collected from the heat or steam generated by the liquid.
Conventional reflectors such as that shown in
Unfortunately, the aforesaid process of manufacturing reflectors is problematic for at least the following reasons. First, the hot bending (using temperatures of at least 580 degrees C.) may cause distortions in the glass itself, which can lead to optical deficiencies. Second, application of a reflective coating onto a pre-bent glass substrate is difficult at best, and often leads to reduced reflective/mirror quality.
Thus, it will be appreciated that there exists a need in the art for a more efficient technique for making bent reflective coated articles. An example of such an article is a mirror which may be used in solar collector applications or the like.
In certain example embodiments of this invention, a reflector for a solar collector or the like is made by (a) forming a reflective coating on a flat glass substrate, (b) cold-bending the glass substrate with the reflective coating thereon using a mold member; and (c) applying a plate member to the cold-bent glass substrate, the plate member for maintaining the coated glass substrate in a bent orientation. The coating may be a single layer coating, or a multi-layer coating, in different example embodiments of this invention. In certain example embodiments of this invention, the glass substrate with the coating thereon may be bent at a temperature of no more than about 200 degrees C., more preferably no more than about 150 degrees C., more preferably no more than about 100 degrees C., even more preferably no more than about 75 degrees C., still more preferably no more than about 50 degrees C., still more preferably no more than about 40 or 30 degrees C., and most preferably at about room temperature.
In certain example embodiments, the plate member may be flat and may be applied to the flat glass substrate prior to bending thereof. Then, the plate member (e.g., of a thermoplastic or the like) and the glass substrate can be bent together with the thermoplastic optionally being pre-heated to permit more efficient bending thereof.
In certain example embodiments of this invention, there is provided a method of making a mirror, the method comprising: providing a flat glass substrate; forming a reflective coating on the flat glass substrate; after the reflective coating has been formed on the flat glass substrate, bending the glass substrate together with the coating thereon into a desired bent shape, the bending being performed when the glass substrate is at a temperature of no more than about 200 degrees C.; and maintaining the glass substrate and the coating thereon in substantially the desired bent shape by using a thermoplastic member that is attached to the glass substrate and/or the coating thereon.
In other example embodiments of this invention, there is provided a method of making a reflector, the method comprising: providing a flat glass substrate; forming a reflective coating on the flat glass substrate, the reflective coating for reflecting visible and/or IR radiation and comprising at least one reflective layer comprising one or more of Ag, Al and/or Cr; after the reflective coating has been formed on the flat glass substrate, bending the glass substrate together with the coating thereon into a desired bent shape, the bending being performed when the glass substrate is at a temperature of no more than about 200 degrees C.; and maintaining the glass substrate and the coating thereon in substantially the desired bent shape by using a frame member.
In still further example embodiments of this invention, there is provided a mirror comprising: a bent glass substrate; a mirror coating on the bent glass substrate, the mirror coating for reflecting visible light and comprising at least one reflective layer comprising one or more of Ag, Al and/or Cr; wherein the bent glass substrate with the mirror coating thereon is maintained in a desired bent shape by a frame member comprising a thermoplastic, so that if the frame member were removed then the glass substrate would no longer be in the desired bent shape.
In other example embodiments of this invention, there is provided a method of making a coated article, the method comprising: providing a flat glass substrate; forming a reflective coating on the flat glass substrate; after the reflective coating has been formed on the flat glass substrate, bending the glass substrate together with the coating thereon into a desired bent shape, the bending being performed when the glass substrate is at a temperature of no more than about 200 degrees C.; and maintaining the glass substrate and the reflective coating thereon in substantially the desired bent shape by using another glass substrate and a glue layer, wherein the glue layer is provided between the glass substrate that supports the reflective coating and the another glass substrate. A corresponding product may also be provided in this regard wherein the glass substrate and the reflective coating thereon are maintained in substantially the desired bent shape by using another glass substrate and the glue layer so that if the glue layer were not present the glass substrate would not be maintained in its desired bent form.
Referring now more particularly to the accompanying drawings in which like reference numerals indicate like parts throughout the several views.
In certain example embodiments of this invention, a reflector for a solar collector or the like is made by (a) forming a reflective coating on a flat glass substrate, (b) cold-bending the glass substrate with the reflective coating thereon using a mold member; and (c) applying a plate member to the cold-bent glass substrate, the plate member for maintaining the coated glass substrate in a bent orientation. In certain example embodiments of this invention, the glass substrate with the coating thereon may be bent at a temperature of no more than about 200 degrees C., more preferably no more than about 150 degrees C., more preferably no more than about 100 degrees C., even more preferably no more than about 75 degrees C., still more preferably no more than about 50 degrees C., still more preferably no more than about 40 or 30 degrees C., and possibly at about room temperature in certain example instances.
In certain example embodiments, the plate member may be flat and may be applied to the flat glass substrate prior to bending thereof. Then, the plate member (e.g., of a thermoplastic or the like) and the glass substrate can be bent together with the thermoplastic optionally being pre-heated to permit more efficient bending thereof.
In certain example embodiments of this invention, the reflector may be used as a mirror in a solar collector, or in any other suitable application. In mirror applications, the mirror may be either a first/front surface mirror or a second surface mirror. However, a second surface mirror is preferred in certain example embodiments, because the glass of the mirror can protect the reflective coating supported thereby from the atmosphere and the like. In a first or front surface mirror, the reflective coating is provided on the front surface of the glass substrate so that incoming light is reflected by the coating before it passes through the glass substrate. Since the light to be reflected does not have to pass through the glass substrate in first surface mirrors (in contrast to rear or second surface mirrors), first surface mirrors generally have higher reflectance than rear surface mirrors and less energy is absorbed by the glass. Thus, the first surface mirrors are more energy efficient than are rear or second surface mirrors. Certain example first surface mirror reflective coatings include a dielectric layer(s) provided on the glass substrate over a reflective layer (e.g., of Al, Ag or the like). However, both first and second surface mirrors may be made and used in different example embodiments of this invention.
In certain example embodiments of this invention, the reflector is a mirror (first or second surface mirrors) which may be used in applications such as one or more of: parabolic-trough power plants, compound parabolic concentrating collectors, solar dish-engine systems, solar thermal power plants, and/or solar collectors, which rely on mirror(s) to reflect and direct solar radiation from the sun. In certain example instances, the mirror(s) may be mounted on a steel or other metal based support system. In certain example embodiments, the reflector may be an IR reflecting coated article that may be used in window or other applications. In such IR reflecting embodiments, the reflective coating may include at least one infrared (IR) reflecting layer of or including a material such as silver, gold, or the like, and may be at least partially transmissive to visible light while blocking significant amounts of IR radiation, and may be used in window or other suitable applications.
In single layer embodiments, the reflective coating 10 may be made up of a single reflective layer of aluminum, silver, chromium, gold or the like that is sufficient to reflect the desired radiation (e.g., visible and/or IR radiation). In multi-layer embodiments, the reflective coating 10 may include a reflective layer of aluminum, silver, chromium, gold or the like and other layer(s) such as silicon oxide, silicon nitride which may be provided over and/or under the reflective layer. Other example reflective coatings 10 are set forth in U.S. Patent Document Nos. 2003/0179454, 2005/0083576, Ser. Nos. 10/945,430, 10/959,321, U.S. Pat. No. 6,783,253 or 6,934,085, any of which may be used herein, the disclosures of which are hereby incorporated herein by reference.
In certain example mirror embodiments, the reflective layer (e.g., Al, Ag, Au or Cr based layer) of the coating 10 may have an index of refraction value “n” of from about 0.05 to 1.5, more preferably from about 0.05 to 1.0. When the reflective layer of the coating 10 is of or based on Al, the index of refraction “n” of the layer may be about 0.8, but it also may be as low as about 0.1 when the layer is of or based on Ag. In certain example embodiments of this invention, a reflective metallic layer of Al may be sputtered onto the glass substrate 9′, directly or indirectly, using a C-MAG rotatable cathode Al inclusive target (may or may not be doped) and/or a substantially pure Al target (>=99.5% Al) (e.g., using 2 C-MAG targets, Ar gas flow, 6 kW per C-MAG power, and pressure of 3 mTorr), although other methods of deposition for the layer may be used in different instances. In sputtering embodiments, the target(s) used for sputtering Al reflective layer may include other materials in certain instances (e.g., from 0-5% Si to help the Al bond to the glass or some other layer). The reflective layer(s) of the coating 10 in certain embodiments of this invention has a reflectance of at least 75% in the 500 nm region as measured on a Perkin Elmer Lambda 900 or equivalent spectrophotometer, more preferably at least 80%, and even more preferably at least 85%, and in some instances at least about 90% or even 95%. Moreover, in certain embodiments of this invention, the reflective layer is not completely opaque, as it may have a small transmission in the visible and/or IR wavelength region of from 0.1 to 5%, more preferably from about 0.5 to 1.5%. The reflective layer may be from about 20-150 nm thick in certain embodiments of this invention, more preferably from about 40-90 nm thick, even more preferably from about 50-80 nm thick, with an example thickness being about 65 nm when Al is used for the reflective layer.
It is advantageous that the reflective coating 10 is formed (e.g., via sputtering or the like) on the glass 9′ when the glass is in a flat form, as shown in
Once the reflective coating 10 has been formed on the flat glass substrate 9′ to form a coated article as shown in
The bending of the coated glass article shown in
After the coated article including the glass 9′ and coating 10 has been cold-bent to its desired shape (e.g., parabolic shape) as shown in
Note that it is possible to use stiffening material (e.g., glass fibers or the like) in the plate 14 so provide the plate 14 with substantially the same dilatation properties as the glass 9′ (e.g., embedded glass fibers in polypropylene). Optionally, the thermoplastic plate 14 may also cover the edges of the glass 9′ and coating 10 so as to function as a mechanical protector to protect the edges of the glass and possibly prevent or reduce oxidation or degradation of the glass 9′ and/or coating 10.
Optionally, as shown in
While
Certain example embodiments of this invention are advantageous for a number of reasons. For example and without limitation, the thin glass 9′ used in the bending process is advantageous in that it permits high reflection characteristics to be realized, low weight characteristics and reduces constraints on the reflective coating. The cold-bending is advantageous in that it reduces distortions of the glass 9′ and/or coating 10 and provides for good shape accuracy, and the application of the coating 10 to the glass 9′ when the glass is in a flat form allows for improved mirror and/or reflective qualities to be realized. Moreover, the laminate nature of the product, with the thermoplastic plate 14 being adhered to the glass 9′, provides for better safety and allows the reflector to perform even if it should be cracked or broken.
In certain example embodiments discussed above, the thermoplastic member (thermoplastic plate 14) maintains the shape of the cold-bent coated article (e.g., mirror). However, in another example embodiment of this invention, the thermoplastic member may be replaced with a glue layer and another glass sheet. Such an example another embodiment is shown with reference to
Referring to
Then, the coated article including flat glass substrate 9′ with reflective coating 10 thereon is coupled to another flat glass substrate 18 with a glue layer 20 provided therebetween (see step S1 in
It is noted that in the
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
