Hal Major © 2009
BobVilaContractors.com
Smart glass or switchable glass refers to glass or glazing that change from transparent to opaque when electricity is applied to it. Smart glass, smart windows and switchable windows are based on three different technologies.
Smart glass allows you to change the amount light and heat that penetrates the glass while leaving a clear view from the inside to the outside. The reduction in heat penetration helps to keep the home cool and reduce air conditioning energy costs. The light reduction helps to preserve interior fabrics and carpeting from fading due to sunlight.
Suspended Particle Glass
In suspended particle glass, a thin film laminate of rod-like particles suspended in a fluid is placed between two sheets of glass or plastic layers. One technology attaches the laminate to a one layer.
When electricity is applied, the suspended particles align with each other and let light pass through. The glass can be dimmed to control of the amount of light and heat passing through. A very small and constant electrical current is needed for keeping the smart window transparent. So, if you want a lot of light to pass through you will need to turn your window on bright.
If you turn the power off, the suspended particles return to their natural random patterns and absorb light. From the outside the glass panel looks dark, blue or, in more recent developments, grey or black color.
Liquid Crystals
The actual name of this smart technology is polymer-dispersed liquid crystal glass. A liquid mix of polymer and liquid crystals is placed between two layers of glass or plastic that includes a thin layer of a transparent, conductive material. The polymer is allowed to cure, forming the sandwich structure of the smart window. This creates a capacitor like effect. Electrodes from a power supply are attached to the transparent electrodes.
Without electricity applied, the liquid crystals are randomly arranged in the droplets, resulting in scattering of light. The window looks milky white in appearance. When electricity is applied, the electric field created between the two electrodes on the glass cause the liquid crystals to align with each other. And, the light passes through the droplets with minimal scattering, making the window clear. The amount electricity applied to the liquid crystals controls the degree of transparency.
Electro chromic Glass
Similar to the suspended particle and liquid crystal glass the electrochromic glass uses electricity to control transparency. The glass changes between a colored, translucent state of blue or blue-green and a clear state. A quick shot of electricity is needed. But once the change has happened, electricity is no longer needed to maintain the darkening. You may have electrochromic glass in your car if you have a rearview mirror that darkens when the light from the car behind you hits the mirror. An electric eye picks up the light and sends a jolt of electricity to the mirror and it darkens.
Smart windows require installation by a reputable contractor and you can learn more at the
Department of Energy website.
