 | Bob Crager of Lewis Street Glass is a 26 year veteran in the glass business. Lewis Street Glass is a leading Wichita Glass company, serving the entire Wichita/Sedgwick County area since 1919. They do anything and everything having to do with glass, both residential and commercial. They also do Auto glass. They are located at 743 South Market, facing Kellogg on the South, and you can reach them by phone at (316) 263-8259. You can email Bob Crager at bcrager@lewisstreetglass.com |
Glass
2010-02-01 08:42:00
Smart windows for commercial buildings
Answer: There’s a good chance you can do that. If you missed last month’s article, go back and re read that so you’ll be up to speed with us this month. There are some companies around that have the ability to upgrade existing windows with “suspended particle device” glass, where you would have the technology within your grasp to control, with remote, or other automatic devices, the “powering on” of your windows for a clear view outside. You might wonder how energy efficient it could be to have to “power on” your windows to get a clear view outside. Well, it’s been said that you can power about 15 or 16 large suspended particle device windows in your home, for example, for less electricity than it takes to provide the power to run a simple night light.
Photocells and other sensing devices can be used to control the level of light automatically. These SPD’s (suspended particle devices) can also be used for a lot of other consumer products, like sun visors, sunroofs, rearview mirrors, and flat panel displays for your computers.
SPD technology isn’t the only smart-window technology on the block. Liquid crystals have been in use for years, and electrochromics essentially performs the same functions as suspended particles. Let’s look briefly here at these two technologies. Windows are undergoing a change the likes of which haven’t been seen since the horizontal mini-blind was developed 50 years ago. Soon, curtains and window blinds could be obsolete. SPD technology is certainly one of the reasons for this window revolution, but other competing technologies like liquid crystals are responsible, too.
You are probably familiar with liquid crystals, which are found in many of the products you use every day. Portable computers, calculators, digital clocks and watches, and microwave ovens all use liquid crystal displays (LCDs). In these displays, electricity is used to change the shape of the liquid crystals to allow light to pass through, thus forming figures and numbers on the display. The technology behind an LCD is similar to the polymer dispersed liquid crystals (PDLCs) used in some smart-window applications. In these windows, the liquid crystals respond to an electrical charge by aligning parallel and letting light through. When the electrical charge is absent, the liquid crystals in the window are randomly oriented. With liquid crystals, the glass is either clear or translucent. There are no intermediate settings. PDLCs are not a developing technology. In fact, they can already be found in offices and homes around the globe. Because it can achieve a translucent setting, PDLC technology is great for homes and offices -- you get privacy without sacrificing all light. PDLCs and suspended particle devices require power for their smart windows to be transparent. A different smart window technology is in development that would reverse the process.
So what else is in store for the future of smart windows?
The future is really bright for the smart window technology, both commercially and residentially, due simply to the amazing array of applications for these relatively new windows. For example, the electrochromic windows darken when voltage is added and are transparent when voltage is taken away. Like suspended particle devices, electrochromic windows can be adjusted to allow varying levels of visibility. They are not an all-or-nothing technology like liquid crystals. Electrochromic windows center around special materials that have electrochromic properties. Electrochromic” describes materials that can change color when energized by an electrical current. Essentially, electricity kicks off a chemical reaction in this sort of material. This reaction (like any chemical reaction) changes the properties of the material. In this case, the reaction changes the way the material reflects and absorbs light. In some electrochromic materials, the change is between different colors. In electrochromic windows, the material changes between colored (reflecting light of some color) and transparent (not reflecting any light).
At its most basic level, an electrochromic window needs this sort of electrochromic material and an electrode system to change its chemical state from colored to transparent and back again. There are several different ways to do this, employing different materials and electrode systems.
Like other smart windows, electrochromic windows are made by sandwiching certain materials between two panes of glass. Here are the materials inside one basic electrochromic window system and the order you will find them in:
1) Glass or plastic panel
2) Conducting oxide
3) Electrochromic layer, such as tungsten oxide
4) Ion conductor/electrolyte
5) Ion storage
6) A second layer of conducting oxide
7) A second glass or plastic panel
In this design, the chemical reaction at work is an oxidation reaction -- a reaction in which molecules in a compound lose an electron. Ions in the sandwiched electrochromic layer are what allow it to change from opaque to transparent. It’s these ions that allow it to absorb light. A power source is wired to the two conducting oxide layers, and a voltage drives the ions from the ion storage layer, through the ion conducting layer and into the electrochromic layer. This makes the glass opaque. By shutting off the voltage, the ions are driven out of the electrochromic layers and into the ion storage layer. When the ions leave the electrochromic layer, the window regains its transparency. Interesting, huh? Some information was researched on the worldwideweb…More next month...
