Scientists Have Developed New Smart Windows That Switch From Clear to Foggy and Generate Heat

Created by scientists at The Chinese University of Hong Kong, smart windows can regulate the amount of sunlight that enters a room by switching from transparent to reflective. The glass is also able to block UV rays and infrared light. 

Generates Energy Independently 

The window generates electricity on its own with mechanical energy and radiant energy from light. Yunluang Ji, an assistant professor at The Chinese University of Hong Kong in China and co-author of the study, said that combining mechanics and radiance is a totally new paradigm that has allowed the team of scientists to change a window's transparency "without too much external power."

Private and Energy Efficient

Compared to traditional glass panels, smart windows are more efficient. With transparent glass, sunlight easily passes through, heating the room in the process. As a result, a lot of electricity is consumed since people turn on fans or air conditioners to stay cool. This is not the case with smart windows. Smart windows tune room temperature without external power, thus reducing energy consumption. They also help ensure privacy in residential and commercial buildings since users can change the windows' opacity at the touch of a button. 
How Do Smart Windows Work?

Between the two layers of glass, there are polymer-dispersed liquid crystals or PDLCs. These liquid crystals are randomly arranged and scatter light as it passes through, making the glass opaque. When an electric current is applied, the crystals align in one direction, allowing the light to easily pass through and making the glass transparent. 
Ji and his team created a new kind of liquid crystal with a helical shape similar to the structure of DNA. This type of liquid is very stable and allows the window display to switch from transparent to foggy and vice versa. After switching, this cholesterol liquid crystal can maintain a foggy state for a week.

The Power Supply

The power source of the smart window is a triboelectric nanogenerator. This is a relatively new type of technology that converts energy from small-scale physical changes into electricity.
These nanogenerators acquire energy through triboelectric charging, in which materials are electrically charged after separation from each other. A common example is static electricity, which comes from running a plastic comb through one's hair"

Even though the power produced by the nanogenerator is very small," Yunluang said, the difference in the appearance of light after charging is huge. The nanogenerator was able to achieve a high transparency contrast of 71.5% in a smart window. This technology can "impact our daily lives" by "making a big difference thanks to low energy." 

In the future, scientists want to optimize this intelligent window system making it more energy-efficient so that manufacturers can use this technology on a larger scale.