Sunlight streaming through a window can really heat up a room. In winter, when heating bills can soar, people tend to welcome that extra warmth. But in summer, that heat just boosts cooling costs. A homeowner could keep out some of that warming light by drawing the curtains or lowering the blinds. Or the window could change its transparency — blocking out some light, as needed — all by itself. That’s the idea behind new “smart” windows.
Some smart windows already exist. They work just like large versions of the LCDs (liquid crystal diodes) found in watches and other electronic devices. When an electric current flows through an LCD window, a coating on the panes of its glass darken. That blocks out some of the light. A homeowner can control the window’s light-blocking ability — or opacity — simply by flipping a switch. Or, a sensor connected to the window can automatically control the current, just like the thermostat used to control a furnace or air conditioner.
But the new smart window does not require such electronics. It depends only on the temperature outdoors, says Xuhong Guo. He’s a chemical engineer at the East China University of Science and Technology in Shanghai. His team designed a new liquid that it sandwiches between two panes of window glass. The researchers describe how this makes their window “smart” in the December 3 issue of Industrial & Engineering Chemistry Research.
