Volume 35, Number 10, October 2000
Changes in Coatings Offer the Industry
a Wide Selection From which to Choose
by Ellen Giard
hether you like it or not, change happensDOS to Windows®, cassette to CD, VCR to DVD. Glass is no exception. When the industry first took an interest in coatings, we saw attractive, shiny, colored glass. A decade later, coated glass has become more functional, and experts predict coatings will continue to evolve with amazing possibilities in the future and prospects that will change the way the world views glass.
This courthouse in Minneapolis features coatings by Viracon.
Chocolate or Vanilla
Since the 1970s, consumers, architects and builders have searched for ways to make windows more energy efficient. Before the invention of low-emissivity glass (low-E), the only glass available did nothing to eliminate, much less reduce, light transmission. Reflective coatings, which gave a building a colored, mirror look, could reduce light transmission, but had no way of blocking harmful rays. By the late 1980s, many people found another efficiency option with low-E coatings.
The first form of low-E glass was created by sputter-coating lites of finished glass. To many, the new soft-coat process was a technological breakthrough, but it did have its limitations. The original soft coat could be scratched or damaged easily and could deteriorate with exposure to air, giving it a brief shelf life. Hard-coat, or pyrolitically-coated, low-E glass, is made while the glass is still hot in the annealing lehr. It offered the advantage of hardness and durability, and became a marketed product in 1988. It had, however, actually been in the invention stages since 1974, developed by Roy G. Gordonaccording to the book Glass.
The Dr. Pepper building in Dallas features Viracons Solarscreen 2000 on grey glass.
An Extra Scoop
Now, in the 21st century, there are hundreds of glass coating choices available in a wide assortment of colors. Coatings today are more functional, user-friendly and offer better performance, said Russell Ebeid, president of Guardian Industries Glass Group, in Auburn Hills, Mich. Now they come in a variety of flavors. In the 1970s, it was as though all we had was chocolate and vanilla. Now we have the whole 31 flavors to choose from.
The initial use of coatings, specifically low-E, sparked a revolution that made the glass industry and consumers aware of the many advantages it provided.
According to Marc Massa, director of product sales for AFG Industries in Kingsport Tenn., glass manufacturers in the 1990s responded to the demands for low-E glass by developing and marketing a vast number of products, with different coatings that could meet various performance criteria. Coatings now can be adapted to suit the needs of a particular region, depending upon its climate, Ebeid said. Its no longer a one-size-fits-all product. He also says coated glass that offers such characteristics as improved energy efficiency and a way to cut heating costs is only a starting point for the future technological advancements and innovations.
The Solar Two plant in Daggett, Calif., features nearly 2,000 sun-tracking mirrors that produce enough
electric power for about 10,000 homes.
So Many Choices
In the not-too-far-off days you may see glass in a car that is the same color as the car, or bathroom mirrors that dont fog or a shower door that doesnt bead water. Such concepts are not impossible. Ebeid explained that in the future most glass is going to have some type of coating. Even windows that change color in response to the position of the sun or glass that has the ability to darken or lighten based upon the users discretion are possibilities.
Most of the coatings we see today are passive, which means they only reduce light or heat or light and heat, said Michelle Spatenka, architect design associate with Viracon. The coatings of the future will be active, in the sense that they will actually absorb the suns heat and store it to use later. We will be reducing the amount of energy we use and using more of the sun as an energy source, she said. Several glass manufacturers are in research and development stages working to make such advanced coatings readily available.
Glass by William S. Ellis (for a review of Glass see USGlass, June 2000 page 8.) also examines what the coatings of tomorrow will be like. New coatings will give glass more control over comfort features such as temperature and light for example, the coating may function as a Venetian blind, opening and closing as needed. Such technology is already being used in many office buildings, but is not yet so advanced as to satisfy the tireless probings of glass scientists, writes Ellis.
Rick Bodette, vice president of technical development at AFG, said that in the future windows are going to become even more user-friendly with the use of anti-reflective coatings that will improve transparency. We also are going to see smart windows that are coated to adjust their shade to match the climate and provide more privacy. Bodette added that anti-wetting coatings, which keep dirt and rain from adhering to the glass, making it easier to clean, will become popular.
According to Ebeid, these new coatings will be comprised of a series of thin layers of metals that adhere to the glass chemically. Each metal has a different property and will give the glass a different characteristic. It is through these metals that we are going to see a myriad of possibilities offered, he said. One coating may just eliminate UV rays while another blocks a certain portion of the suns rays, such as the ones that fade furniture. These coatings will be spectrally-selective.
As these new coatings come into play, it is not just glass that will be experiencing change, but the industry as a whole. For starters, companies that take on this endeavor will have to make major financial investments, anywhere from $15 million to $35 million, depending on the number of coatings a particular manufacturer is capable of handling at a single time, Ebeid said. He also believes the glass industry will have to become more multi-dimensional in order to succeed in this area. The biggest need is going to be a more technical upgrade of personnel, he said. Manufacturers of these coatings are going to have to be consistent and steady about qualifying the contractors they use and the industry will have to be sensitive to the proper installation procedures. He also noted that in the long run the use of these coatings will further differentiate the glass manufacturers. Those who pull this off are going to be the big winners, he said.
And, like with any new and improved product, coatings will have to overcome challenges and obstacles before becoming a mainstream product. For example, Ebeid explained that since people are generally in a no-change mode, it may take a long time for the new coatings to be accepted. He also added that since the industry, as a whole, can be slow to move, these products may not get a quick start up. The people involved in these coatings are going to have to have deep pockets, he said.
The Cherry on Top
Perhaps one of the most impressive and awe-inspiring inventions to unfold lies in the concept of Photovoltaics (PV), which are solid state semiconductor devices that can convert light directly into electricity. Photovoltaics offer the ability to control the amount of outdoor light that is let inside, to some level, and at the same time produce electricity, said Gerry Braun, director of thin-film marketing for BP Solar, a PV manufacturer.
PV devices, called solar cells, consist of layers of semiconductor materials that have different electronic properties. According to the U.S. Department of Energy (DOE) Photovoltaics Program website, the process was first used in the space program, and can be used to pump water, light up the night, activate switches, charge batteries and more.
For glass, PV thin film can be placed on either side of a lite of glass. Either way requires a different mechanism and structure of the cell, said James Rannels, director, DOE Office of Solar Energy and Technology. He added that while PV can be affixed directly to a roof or structure, many people find them unattractive to view. They can also be incorporated directly into a building, as part of a skylight, for instance.
In the United States PV thin films most commonly are used in commercial projects, but in other countries are also being used widely in homes. More than 20,000 homes a year in Japan are adding rooftop solar and a similar number in Germany, Braun said. He added that the homes in the United States using this process are concentrated in California where there is a state program supporting PV; however, the number of homes using rooftop solar throughout this country is limited. We can see a day when Photovoltaics are just like another coating used for a particular project, Braun said. And it will become part of the manufacturing process as well.
In addition, many glass manufacturers are heading in the direction of PV and working to help market these new coatings. Pilkington Solar International, for example, is partnering with Gelsenkirchen Research Institute, which is developing a PV cell invented by Michael Grätzel. According to Pilkingtons website, the cell uses coated glass plates, one of which acts as an aphotosensitiser that harvests sunlight, ultimately to release electrons that will generate an electric current.
The Last Bite
Three decades ago the world first saw a new opportunity in glass coatings. Today, glass manufacturers, consumers and architects can expect to find more comfort, energy efficiency and benefits from quality glass products.
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