Though the concept is not new—variations including liquid crystal (LC) and suspended-particle technologies have been available for several years—Sage has worked to vamp up and refine the production of what they consider to be a superior technology. “Electrochromic materials are more durable, have a wider dynamic range, and respond to infrared and visible light,” Van Dine says. By comparison, he explains, LC windows consume larger amounts of AC voltage, and they're not translucent in a solid state; the other alternatives, suspended particle windows, are similar to LC in their energy consumption and even more complicated to construct and maintain. Over the last two years, Sage has worked closely with the Center for Ceramic Research at Rutgers University to optimize its use of inorganic ceramic materials, and they installed a new manufacturing facility in Faribault, Minn., to accommodate the mass production of large-scale windows (up to 212.5 square feet).
Though electrochromic windows have been installed in several homes and commercial spaces in the last few years, prior to this, their use had been restricted to proprietary applications, including transport vehicles for military personnel on duty in severely hot climates and blast-resistant windows requiring minimal heat and solar gain. Beginning this year, Sage is offering their product for use in large-scale commercial and public settings. Though they do not recommend specifying the product for an entire facade—rather, to implement a window or two here or there as needed—widespread use is at last a possibility.
Sage's forthcoming product, embedded with solar collecting cells, takes electrochromics and photovoltaics a step further by recognizing the interdependence of these two technologies. Like cell phones and laptop computers, electrochromic glass runs on direct current (DC), or the constant flow of electrons from low to high potential. Solar panels generate DC power, which for most other applications must be converted to alternating current (AC). With electrochromic glass, however, conversion to AC is not necessary, because the input of the windows matches the output of the PV cells. On bright sunny days, when conditions are optimal for producing more PV energy, a phase-change will probably be desired (to keep light out), and the energy needed to implement it will already be available. On cloudy days, users will probably want to let light in and the small amount of PV energy that is available from the environment won't be needed.
Though the company has already been approached to supply electrochromic glass for skyscrapers, at the moment they're more interested in implementing the technology in a variety of building types and at strategic points, such as a southwest-facing facade or on a roof. “We're particularly interested in working with architects and owners that want to preserve a visual connection to the outside,” Van Dine says.
Each pane of electrochromic glass passes through a large tempering oven on rollers.
The coatings are added to the electrochromic glass through a process called sputtering. The panes pass through a series of large vacuum chambers where plasma is charged to produce ions that graft to the glass and form each coating.
Sage electrochromic glass can be tinted to varying degrees, allowing for the user to control light- flow into the work place.
The electrochromic coatings are on the inner surface of the outer pane of the insulating glass unit. When the glass is tinted, the coatings reradiate the sun's energy as it hits the glass, preventing that energy from passing through the second pane and into the interior of the building.
Looking through a porthole in the coater, the vacuum chamber in the sputtercoating machine is bathed in a purple light given off by plasma. Argon ions are extracted from the plasma to form one of the five coatings.
Soft-coat low-E glass, like electrochromic glass, is manufactured using a sputtercoating process. But whereas soft-coat low-E glass is about .15 microns thick, electrochromic glass, with its five distinct layers, measures .8 microns.