Just like other smart home features, smart windows are designed to be intuitive. Imagine a world in which your home’s windows will be controllable via smartphone or even simple gesture. Heat-sensor window treatments will automatically close or open depending on a homeowner’s ideal temperature preferences. Not only will you gaze through your window to the outside world, but you will also be able to virtually interact with your home environment, pane by translucent pane.
The newly designed “smart” windows consist of conductive glass plates outlined with metal ions that spread out over the surface, blocking light in response to an electrical current.
Windows that tint on demand already exist—one prominent class of them is known as electrochromic windows. Method involves using ions from two metals, like copper and silver, in an electrolyte gel on the window. The glass also needs to have indium tin oxide in it, a transparent conductor that’s ubiquitous in television and smartphone screens. By applying a negative electrical voltage, the window becomes dark because the ions form elemental, solid metal, which is opaque. A positive voltage causes the metal to dissolve back into ion form, allowing the light to come through.
Fast and durable
Commercially available smart windows are made of materials, such as tungsten oxide, that change color when charged with electricity. But according to McGehee, these materials tend to be expensive, have a blue tint, can take more than 20 minutes to dim and become less opaque over time.
The Stanford prototype blocks light through the movement of a copper solution over a sheet of indium tin oxide modified with platinum nanoparticles. When transparent, the window is clear and allows about 80 percent of surrounding natural light to pass through. When dark, the transmission of light drops to below 5 percent. It only takes about 30 seconds to change from transparent to dark or vice versa.
Smart windows change how they filter the sunlight based on the weather outside.
In cold weather, smart windows let more sunlight in, and in warm weather, they keep sunlight out. There are a range of technologies that enable the windows to do this.
Certain smart windows are powered by electricity and include a switch or button for changing the sunlight filter. Some electric-powered models can be programmed to automatically change based on outdoor weather. Electric windows use small amounts of energy to operate their controls, which detracts slightly from their energy savings.
Other windows use nanotechnology to change from transparent to opaque. For example, flexible thermochromic technology adjusts the incoming light based on the weather without the use of electricity. RavenBrick, the company’s manufacturer, claims that the windows can save up to 30% on the building’s energy use, and are twice as efficient as the leading energy efficient windows on the market.