United Facade

Electro-Chromic (EC) Smart Glass

[section label=”Media Top” bg=”437″ bg_color=”rgb(170, 40, 47)” bg_overlay=”rgba(35, 29, 29, 0.837)” padding=”0px”] [row] [col span__sm=”12″] [/col] [/row] [row style=”large” h_align=”center”] [col span=”11″ span__sm=”12″ align=”center”] [ux_text text_align=”left” text_color=”rgb(255, 255, 255)”]

Electro-Chromic (EC) Smart Glass

Electro-Chromic smart glass is capable of adjusting its transmittance, which refers to the amount of light it allows to pass through, when subjected to an electrical signal. This reversible transformation can modify the glass’s state from transparent to opaque or any intermediate state. Moreover, current studies are focusing on the ability to manipulate the reflectance of electrochromic smart glass using similar techniques.

How does classic Electro-Chromic glass work?

Electro-Chromic glass comes in various types, each with distinct characteristics. Some types solely darken when stimulated, akin to photochromic sunglasses that darken when exposed to sunlight. Other types darken and turn translucent, while some become reflective and opaque like a mirror.

Various technologies power different types of electrochromic glass, but I will only elaborate on one of them, the original technology discovered by Dr. Satyen K. Deb in 1969. This technology involves the movement of lithium ions in transition metal oxides, such as tungsten oxide. Lithium, which is commonly found in rechargeable lithium-ion batteries, is the chemical element responsible for this technology.

Regular windows are typically composed of a single vertical pane of glass, whereas double-glazed windows have two glass panes separated by an air gap to improve insulation against heat and sound. More advanced windows, which utilize low-e heat-reflective glass, have a thin layer of metallic chemicals coating them, keeping homes warm during winter and cool during summer. Electrochromic windows operate similarly to these windows, but with much more advanced metal-oxide coatings, which are deposited using manufacturing processes akin to those used in the production of integrated circuits (such as silicon computer chips).

When discussing “Electrochromic glass,” it’s important to note that the window can be made from either glass or plastic, serving as the base material or substrate. This substrate is coated with multiple thin layers through a process called sputtering, which precisely adds thin films of one material onto another. On the interior surface facing into your home, the window features a double-sandwich composed of five ultra-thin layers. The center is occupied by a separator, flanked by two electrodes (thin electrical contacts) on either side of the separator, and then two transparent electrical contact layers on either side of the electrodes. The fundamental working principle involves the migration of lithium ions (positively charged lithium atoms with missing electrons) back and forth between the two electrodes through the separator. In its transparent state, the lithium ions reside in the innermost electrode, which typically consists of lithium cobalt oxide (LiCoO2). When a low voltage is applied to the electrodes, the ions travel through the separator to the outermost electrode, where they soak into a layer made of polycrystalline tungsten oxide (WO3), effectively causing it to reflect light and turning the window opaque. The ions remain there until the voltage is reversed, prompting them to move back and restoring the window’s transparency. Electrochromic windows do not require power to maintain their clear or dark state—only to switch between the two.

What’s good and bad about Electro-Chromic windows?


Smart windows have significant environmental benefits, despite their seeming novelty. When in their opaque state, they block nearly all (about 98 percent) of the sunlight hitting them, which can substantially reduce the need for air conditioning and the associated installation and energy costs. Since they are operated by electricity, they can be easily controlled by a smart home system or sunlight sensor, regardless of whether people are inside the building. According to the National Renewable Energy Laboratory (NREL) of the US Department of Energy, these windows could save up to one eighth of the total energy used by buildings in the US each year. Although smart windows require only small amounts of electricity to switch from dark to light (100 windows use about as much energy as a single incandescent lamp), they result in a significant net energy savings. Smart windows also offer privacy at the touch of a button (eliminating the need for dusty curtains and blinds), convenience (automatically darkening windows can protect upholstery and artwork from fading), and improved security (electrically operated curtains are notoriously unreliable).


It’s worth noting that the cost of installing smart windows can be significantly higher than that of regular glass, given the necessary electrodes and specialized metal coatings involved. A single large smart window can cost between $500 and $1000, equating to around $50 to $100 per square foot (or $500 to $1000 per square meter). However, concerns also exist about the longevity of the materials, with current windows losing their efficiency within just 10 to 20 years, which is much shorter than what most homeowners would anticipate from conventional glazing. Another disadvantage is the time it takes for some electrochromic windows to switch between being transparent and opaque, which could take several minutes, whereas stick-on electrochromic films can change much more quickly, transitioning within a second.

[/ux_text] [/col] [/row] [/section]