PrintSmart Windows operate very similarly to photochromatic sunglasses, which have lenses that darken automatically in response to bright light. Since windows let in heat as well as light, it would not be energy efficient to block out sunlight (heat) on a cold winter day. Therefore, smart windows have control switches that permit them to be manually turned on or off—so, instead of adjusting a shade or blind, one simply flicks the switch of the Smart Window.
Instructions: Click and drag the button in the image to see the amount of incoming light when the Smart Window is on and off.
Click here to open a text description of the Smart Window activity.
Smart Windows use a new technology called Suspended Particle Devices (SPDs). They are small, light-absorbing microscopic particles or light valves. In Smart windows, millions of the SPDs are placed between two panes of glass that are coated with conductive material.
- When the Smart Windows are turned "on," electricity from the control switch travels through the conductive coating and causes the SPDs to line up and allow the passage of light.
- When the Smart Windows are turned "off," no electricity travels through the conductive coating, so the particles float freely between the glass, causing it to appear darkened or tinted.
A similar technology using electrochromics is also being developed to improve windows.
Instructions: Click the play button below to observe how the SPDs react.