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Coming soon: smart windows -- a high-tech, residential option

You've heard of smart pets: Roll over, Poopsie! Fetch! Speak!

But have you heard of smart windows? Darken, Window! Lighten!

Soon, your windows might be as smart as your pets…and save you money, too. Much as you love your pets, you probably can't say that about them.

Smart window technology for the homeowner might be only a couple of years away, according to Dennis Vogt of Distinctive Glass in Lynnwood, Wash., a suburb of Seattle. Right now, he says, these self-darkening windows are finding their way into big commercial buildings, but are too pricey for residential applications. But with the aid of federal research and development money, the cost has been dropping -- though it is still two to three times more than conventional glass, according to Eric Bloom, a researcher for Pike Research.

What are smart windows?

The U.S. Department of Energy's Lawrence Livermore National Laboratory, which has been heavily involved in smart-window technology, estimates that windows in the United States currently cost us $40 billion a year in energy use; hence, there is tremendous pressure to take windows well beyond the 1970s' low-e, double-pane technology currently in use.The frenzy of research to create smart windows has spawned four different glass technologies that can either darken the glass or make it turn opaque, as needed:

  1. Photochromic: This glass darkens when it gets lighter outside, much like photosensitive sunglasses. A disadvantage is that the windows may darken when you don't want them to -- for instance on a cold, sunny day when you would like to have sunlight to warm your room.
  2. Thermocromic: These windows will darken as the temperature rises to reduce solar heating. They can significantly reduce air-conditioning costs. However, because the glass becomes opaque as it heats, they are not suitable for view windows but have applications in areas such as skylights.
  3. Liquid crystal display: LCD windows do not block light, nor do they provide energy savings. They are used for privacy. In their natural state, the liquid crystals are random and create a milky-white translucence. When energy is applied, the crystals align, clearing the window and letting light pass freely through it.
  4. Electrochromic: Applying an electrical current will darken these windows. The darkened glass can range from clear to opaque, so they are suitable for a variety of uses, including privacy, reducing glare, and cutting solar heat. The windows operate on very low voltage; the current is used only to darken and lighten the window, not to maintain the level of tint, so there is not a continuing draw of electricity. Also, according to the National Association of Homebuilders, electrochromic windows can be fine-tuned to block certain wavelengths, such as infrared (heat). Electrochromic glass is the one most likely destined for residential use.

How are smart windows currently in use?

  • In commercial buildings smart windows can reduce energy loss in vast expanses of windows. They also can be used to create privacy in conference rooms.
  • Some hospitals have tried them instead of curtains in a multi-patient room. Besides darkening to provide privacy, they limit sound transmission and are easier to sterilize than curtains.
  • Boeing has used them on its new 787 Dreamliner. Instead of the customary pull-down shades, the windows have several levels of shading.

When can they be available for home use?

Two major electrochromic-glass developers in the U.S. are on the verge of mass-producing their product. Sage Electrochromics of Minnesota is building a massive production plant with the help of a $72 million loan guarantee from the Department of Energy and $31 million in tax credits. A California company, Soladigm, plans to build a plant in Mississippi to mass-produce its electrochromic glass. Such large-scale production spurs Vogt's optimism for residential smart windows, as it should bring the costs down.

When smart windows do become available for residential use, along with the existing low-e technology that is currently the standard for energy-efficient windows, they could generate huge energy savings. While modern low-e windows are around 50 percent more efficient than their 1970s' precursors, smart windows can probably increase that efficiency by an additional 50 percent.

Most types of smart windows operate with a low-voltage current, but while they use very little electricity, homes will need to be specially wired for them, which makes retrofitting problematic. However, it is conceivable that researchers could create solar-power units for smart windows to provide the needed electricity without internal house wiring.

Besides applications for windows, smart glass may also be used to create privacy inside the home, such as in the bathroom around toilets or showers.

For now, switches activate smart glass, but it is no jump in technology to activate it by voice. And a smartphone app could activate it remotely.

Yes, your windows soon could actually be smarter than your pet. The question is whether Poopsie will be jealous if you love your windows more.

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