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The open and shut case for "smart" windows
The so-called "smart" window isn't really smart, but it may well offer a smart alternative to cabin windows with manually or electrically operated shades. With the touch of a button, the "smart" window goes from clear to opaque and back-or anywhere in between.
The technology isn't new, but after about half a decade of development, it has reached the point where it is commercially available. Two aircraft manufacturers already offer it.
Hawker Beechcraft recently picked the SPD (suspended particle device) SmartGlass window as a retrofit item on its entire line of King Air twin turboprops. The aircraft manufacturer may also make the window available as a standard option on new King Airs, as well as on its Premier IA and Hawker business jets.
The SPD window resulted from six years of work by Research Frontiers of Woodbury, N.Y., and a two-year joint development project with manufacturer/distributor InspecTech Aero Service of Fort Lauderdale.
The advantages over current window-shade systems are multiple. The SPD product, which comes with a five-year warranty, has no moving parts; blocks more than 99.9 percent of harmful ultraviolet radiation; has no known limit to its life expectancy; and weighs less but costs no more than a window with an electrically operated shade.
According to InspecTech president Jim Lang, "We recently replaced a set of pleated-shade, manually operated aircraft windows for several hundred dollars less per window than it would have cost to replace them with [windows with] new pleated shades."
InspecTech's product comes in two variants-the e-Shade and the i-Shade. The e-Shade adjusts from clear to opaque and any point in between, and blocks 99.5 percent of incoming light. The i-Shade has a simple on/off button and at its opaque setting blocks 100 percent of incoming light.
The SPD technology involves millions of black particles, which are suspended in a liquid sandwiched between two layers of polycarbonate. By nature, the particles remain in a random pattern, blocking light from passing through the window. When an electric current is introduced into a conductive coating on the polycarbonate, the particles line up and allow light to pass through. How much light depends on the voltage applied.
InspecTech is looking into further uses for SPD technology and company owner Jim Lang said he has already had a request for an SPD cabin divider.
Meanwhile, Boeing Company has contracted with InspecTech competitor PPG Aerospace of Huntsville, Ala., to install PPG's electrochromic "smart" windows in Boeing's new 787 airliner. According to PPG Aerospace vice president David Morris, it will be the first commercial aviation application for electrochromic window technology.
Gentex Corp. of Zeeland, Mich., which developed the technology, may be best known for its development (using similar technology) of rear-view mirrors designed to reduce headlight glare from approaching automobiles. The PPG-Gentex relationship, according to Morris, allows the two companies to develop and market the new technology faster than either could do alone. PPG expects to begin shipments of the windows to Boeing later this year.
The Gentex technology is similar to that of Research Frontiers, but only in that its "active ingredient" is sandwiched between two pieces of glass that are coated on the inside with an electrical conductor. Where it differs is that the Genex "sandwich" contains an organic gel through which the electrical current passes, causing the gel to darken.
In the Boeing 787 windows, passengers will have the choice of five opacity levels. With no electric current, the window allows the passage of approximately 60 percent of exterior light. When the maximum current is applied, just 0.1 percent of light passes through. According to the company, the windows block 100 percent of ultraviolet rays.
The use of glass makes the windows from PPG heavier than those from InspecTec, but a PPG spokesman said the company is developing a means to apply the conducting coat to polycarbonate as well as glass.