With the world facing an impending energy crisis, researchers have been working on new low-power-consuming technologies. Studies show that around 2% of all the energy used in the US is “taken” by residential windows. So developing cutting-edge technologies like smart windows, that allow consumers to block either all light or just some will potentially save billions of dollars on heating, cooling and lighting costs. Existing smart window products are made of materials, such as thermotropic and photochromic technology, that change color but tend to be expensive, and take a long time to change shades.
Stanford University engineers have recently filed a patent for their work on a new approach to dynamic smart windows. The method presented in Cell Press’s new journal Joule, involves embedding the glass with indium tin oxide, and using ions from two metals, like copper and silver, in an electrolyte gel on the window. The metal ions are spread out over the surface, blocking light, in response to electrical current rapidly. A negative electrical voltage applied to the window transforms it from light to dark. And applying a positive charge causes the reverse transformation from dark to light. These highly durable, neutral color, high contrast windows transform from clear to dark in less than a minute.
Chris Barile assistant professor of chemistry at the University of Nevada Reno, and the study’s first author, says the electrical charge is only needed to change the window’s opacity. “We designed it so that when you do unplug the window, it’s stable,” Barile says. “Whatever state you leave the window in, it will stay in.”
The next big hurdle for the team is increasing the functional size of the windows, which are very small in their first prototype. The next goal set is to create the same window that scales over three feet per side. “This is the big challenge,” Barile says: “As the voltage travels across the surface of the window, it drops, making the device work less effectively.”
- Yue et al. Dynamic Windows with Neutral Color, High Contrast, and Excellent Durability using Reversible Metal Electrodeposition. Joule, 2017 DOI: 10.1016/j.joule.2017.06.001